diff --git a/backends/imgui_impl_allegro5.cpp b/backends/imgui_impl_allegro5.cpp
index 03a4570..9688f68 100644
--- a/backends/imgui_impl_allegro5.cpp
+++ b/backends/imgui_impl_allegro5.cpp
@@ -6,7 +6,8 @@
 //  [X] Platform: Keyboard support. Since 1.87 we are using the io.AddKeyEvent() function. Pass ImGuiKey values to all key functions e.g. ImGui::IsKeyPressed(ImGuiKey_Space). [Legacy ALLEGRO_KEY_* values will also be supported unless IMGUI_DISABLE_OBSOLETE_KEYIO is set]
 //  [X] Platform: Clipboard support (from Allegro 5.1.12)
 //  [X] Platform: Mouse cursor shape and visibility. Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange'.
-// Issues:
+// Missing features:
+//  [ ] Renderer: Multi-viewport support (multiple windows)..
 //  [ ] Renderer: The renderer is suboptimal as we need to convert vertices manually.
 //  [ ] Platform: Missing gamepad support.
 
diff --git a/backends/imgui_impl_allegro5.h b/backends/imgui_impl_allegro5.h
index 5b63654..a7f7c0e 100644
--- a/backends/imgui_impl_allegro5.h
+++ b/backends/imgui_impl_allegro5.h
@@ -6,7 +6,8 @@
 //  [X] Platform: Keyboard support. Since 1.87 we are using the io.AddKeyEvent() function. Pass ImGuiKey values to all key functions e.g. ImGui::IsKeyPressed(ImGuiKey_Space). [Legacy ALLEGRO_KEY_* values will also be supported unless IMGUI_DISABLE_OBSOLETE_KEYIO is set]
 //  [X] Platform: Clipboard support (from Allegro 5.1.12)
 //  [X] Platform: Mouse cursor shape and visibility. Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange'.
-// Issues:
+// Missing features:
+//  [ ] Renderer: Multi-viewport support (multiple windows)..
 //  [ ] Renderer: The renderer is suboptimal as we need to unindex our buffers and convert vertices manually.
 //  [ ] Platform: Missing gamepad support.
 
diff --git a/backends/imgui_impl_android.cpp b/backends/imgui_impl_android.cpp
index b0c4639..994b0c6 100644
--- a/backends/imgui_impl_android.cpp
+++ b/backends/imgui_impl_android.cpp
@@ -8,6 +8,7 @@
 //  [ ] Platform: Clipboard support.
 //  [ ] Platform: Gamepad support. Enable with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
 //  [ ] Platform: Mouse cursor shape and visibility. Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange'. FIXME: Check if this is even possible with Android.
+//  [ ] Platform: Multi-viewport support (multiple windows). Not meaningful on Android.
 // Important:
 //  - Consider using SDL or GLFW backend on Android, which will be more full-featured than this.
 //  - FIXME: On-screen keyboard currently needs to be enabled by the application (see examples/ and issue #3446)
diff --git a/backends/imgui_impl_android.h b/backends/imgui_impl_android.h
index 557bf0e..7cd4ef1 100644
--- a/backends/imgui_impl_android.h
+++ b/backends/imgui_impl_android.h
@@ -8,6 +8,7 @@
 //  [ ] Platform: Clipboard support.
 //  [ ] Platform: Gamepad support. Enable with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
 //  [ ] Platform: Mouse cursor shape and visibility. Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange'. FIXME: Check if this is even possible with Android.
+//  [ ] Platform: Multi-viewport support (multiple windows). Not meaningful on Android.
 // Important:
 //  - Consider using SDL or GLFW backend on Android, which will be more full-featured than this.
 //  - FIXME: On-screen keyboard currently needs to be enabled by the application (see examples/ and issue #3446)
diff --git a/backends/imgui_impl_dx10.cpp b/backends/imgui_impl_dx10.cpp
index 9691b49..0123aa6 100644
--- a/backends/imgui_impl_dx10.cpp
+++ b/backends/imgui_impl_dx10.cpp
@@ -4,6 +4,7 @@
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'ID3D10ShaderResourceView*' as ImTextureID. Read the FAQ about ImTextureID!
 //  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.
+//  [X] Renderer: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
@@ -15,6 +16,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2024-XX-XX: Platform: Added support for multiple windows via the ImGuiPlatformIO interface.
 //  2022-10-11: Using 'nullptr' instead of 'NULL' as per our switch to C++11.
 //  2021-06-29: Reorganized backend to pull data from a single structure to facilitate usage with multiple-contexts (all g_XXXX access changed to bd->XXXX).
 //  2021-05-19: DirectX10: Replaced direct access to ImDrawCmd::TextureId with a call to ImDrawCmd::GetTexID(). (will become a requirement)
@@ -79,6 +81,10 @@
     return ImGui::GetCurrentContext() ? (ImGui_ImplDX10_Data*)ImGui::GetIO().BackendRendererUserData : nullptr;
 }
 
+// Forward Declarations
+static void ImGui_ImplDX10_InitPlatformInterface();
+static void ImGui_ImplDX10_ShutdownPlatformInterface();
+
 // Functions
 static void ImGui_ImplDX10_SetupRenderState(ImDrawData* draw_data, ID3D10Device* ctx)
 {
@@ -542,6 +548,7 @@
     io.BackendRendererUserData = (void*)bd;
     io.BackendRendererName = "imgui_impl_dx10";
     io.BackendFlags |= ImGuiBackendFlags_RendererHasVtxOffset;  // We can honor the ImDrawCmd::VtxOffset field, allowing for large meshes.
+    io.BackendFlags |= ImGuiBackendFlags_RendererHasViewports;  // We can create multi-viewports on the Renderer side (optional)
 
     // Get factory from device
     IDXGIDevice* pDXGIDevice = nullptr;
@@ -558,6 +565,8 @@
     if (pDXGIAdapter) pDXGIAdapter->Release();
     bd->pd3dDevice->AddRef();
 
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        ImGui_ImplDX10_InitPlatformInterface();
     return true;
 }
 
@@ -567,12 +576,13 @@
     IM_ASSERT(bd != nullptr && "No renderer backend to shutdown, or already shutdown?");
     ImGuiIO& io = ImGui::GetIO();
 
+    ImGui_ImplDX10_ShutdownPlatformInterface();
     ImGui_ImplDX10_InvalidateDeviceObjects();
     if (bd->pFactory) { bd->pFactory->Release(); }
     if (bd->pd3dDevice) { bd->pd3dDevice->Release(); }
     io.BackendRendererName = nullptr;
     io.BackendRendererUserData = nullptr;
-    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;
+    io.BackendFlags &= ~(ImGuiBackendFlags_RendererHasVtxOffset | ImGuiBackendFlags_RendererHasViewports);
     IM_DELETE(bd);
 }
 
@@ -585,6 +595,129 @@
         ImGui_ImplDX10_CreateDeviceObjects();
 }
 
+//--------------------------------------------------------------------------------------------------------
+// MULTI-VIEWPORT / PLATFORM INTERFACE SUPPORT
+// This is an _advanced_ and _optional_ feature, allowing the backend to create and handle multiple viewports simultaneously.
+// If you are new to dear imgui or creating a new binding for dear imgui, it is recommended that you completely ignore this section first..
+//--------------------------------------------------------------------------------------------------------
+
+// Helper structure we store in the void* RendererUserData field of each ImGuiViewport to easily retrieve our backend data.
+struct ImGui_ImplDX10_ViewportData
+{
+    IDXGISwapChain*         SwapChain;
+    ID3D10RenderTargetView* RTView;
+
+    ImGui_ImplDX10_ViewportData()   { SwapChain = nullptr; RTView = nullptr; }
+    ~ImGui_ImplDX10_ViewportData()  { IM_ASSERT(SwapChain == nullptr && RTView == nullptr); }
+};
+
+static void ImGui_ImplDX10_CreateWindow(ImGuiViewport* viewport)
+{
+    ImGui_ImplDX10_Data* bd = ImGui_ImplDX10_GetBackendData();
+    ImGui_ImplDX10_ViewportData* vd = IM_NEW(ImGui_ImplDX10_ViewportData)();
+    viewport->RendererUserData = vd;
+
+    // PlatformHandleRaw should always be a HWND, whereas PlatformHandle might be a higher-level handle (e.g. GLFWWindow*, SDL_Window*).
+    // Some backends will leave PlatformHandleRaw == 0, in which case we assume PlatformHandle will contain the HWND.
+    HWND hwnd = viewport->PlatformHandleRaw ? (HWND)viewport->PlatformHandleRaw : (HWND)viewport->PlatformHandle;
+    IM_ASSERT(hwnd != 0);
+
+    // Create swap chain
+    DXGI_SWAP_CHAIN_DESC sd;
+    ZeroMemory(&sd, sizeof(sd));
+    sd.BufferDesc.Width = (UINT)viewport->Size.x;
+    sd.BufferDesc.Height = (UINT)viewport->Size.y;
+    sd.BufferDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
+    sd.SampleDesc.Count = 1;
+    sd.SampleDesc.Quality = 0;
+    sd.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;
+    sd.BufferCount = 1;
+    sd.OutputWindow = hwnd;
+    sd.Windowed = TRUE;
+    sd.SwapEffect = DXGI_SWAP_EFFECT_DISCARD;
+    sd.Flags = 0;
+
+    IM_ASSERT(vd->SwapChain == nullptr && vd->RTView == nullptr);
+    bd->pFactory->CreateSwapChain(bd->pd3dDevice, &sd, &vd->SwapChain);
+
+    // Create the render target
+    if (vd->SwapChain)
+    {
+        ID3D10Texture2D* pBackBuffer;
+        vd->SwapChain->GetBuffer(0, IID_PPV_ARGS(&pBackBuffer));
+        bd->pd3dDevice->CreateRenderTargetView(pBackBuffer, nullptr, &vd->RTView);
+        pBackBuffer->Release();
+    }
+}
+
+static void ImGui_ImplDX10_DestroyWindow(ImGuiViewport* viewport)
+{
+    // The main viewport (owned by the application) will always have RendererUserData == 0 here since we didn't create the data for it.
+    if (ImGui_ImplDX10_ViewportData* vd = (ImGui_ImplDX10_ViewportData*)viewport->RendererUserData)
+    {
+        if (vd->SwapChain)
+            vd->SwapChain->Release();
+        vd->SwapChain = nullptr;
+        if (vd->RTView)
+            vd->RTView->Release();
+        vd->RTView = nullptr;
+        IM_DELETE(vd);
+    }
+    viewport->RendererUserData = nullptr;
+}
+
+static void ImGui_ImplDX10_SetWindowSize(ImGuiViewport* viewport, ImVec2 size)
+{
+    ImGui_ImplDX10_Data* bd = ImGui_ImplDX10_GetBackendData();
+    ImGui_ImplDX10_ViewportData* vd = (ImGui_ImplDX10_ViewportData*)viewport->RendererUserData;
+    if (vd->RTView)
+    {
+        vd->RTView->Release();
+        vd->RTView = nullptr;
+    }
+    if (vd->SwapChain)
+    {
+        ID3D10Texture2D* pBackBuffer = nullptr;
+        vd->SwapChain->ResizeBuffers(0, (UINT)size.x, (UINT)size.y, DXGI_FORMAT_UNKNOWN, 0);
+        vd->SwapChain->GetBuffer(0, IID_PPV_ARGS(&pBackBuffer));
+        if (pBackBuffer == nullptr) { fprintf(stderr, "ImGui_ImplDX10_SetWindowSize() failed creating buffers.\n"); return; }
+        bd->pd3dDevice->CreateRenderTargetView(pBackBuffer, nullptr, &vd->RTView);
+        pBackBuffer->Release();
+    }
+}
+
+static void ImGui_ImplDX10_RenderViewport(ImGuiViewport* viewport, void*)
+{
+    ImGui_ImplDX10_Data* bd = ImGui_ImplDX10_GetBackendData();
+    ImGui_ImplDX10_ViewportData* vd = (ImGui_ImplDX10_ViewportData*)viewport->RendererUserData;
+    ImVec4 clear_color = ImVec4(0.0f, 0.0f, 0.0f, 1.0f);
+    bd->pd3dDevice->OMSetRenderTargets(1, &vd->RTView, nullptr);
+    if (!(viewport->Flags & ImGuiViewportFlags_NoRendererClear))
+        bd->pd3dDevice->ClearRenderTargetView(vd->RTView, (float*)&clear_color);
+    ImGui_ImplDX10_RenderDrawData(viewport->DrawData);
+}
+
+static void ImGui_ImplDX10_SwapBuffers(ImGuiViewport* viewport, void*)
+{
+    ImGui_ImplDX10_ViewportData* vd = (ImGui_ImplDX10_ViewportData*)viewport->RendererUserData;
+    vd->SwapChain->Present(0, 0); // Present without vsync
+}
+
+void ImGui_ImplDX10_InitPlatformInterface()
+{
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    platform_io.Renderer_CreateWindow = ImGui_ImplDX10_CreateWindow;
+    platform_io.Renderer_DestroyWindow = ImGui_ImplDX10_DestroyWindow;
+    platform_io.Renderer_SetWindowSize = ImGui_ImplDX10_SetWindowSize;
+    platform_io.Renderer_RenderWindow = ImGui_ImplDX10_RenderViewport;
+    platform_io.Renderer_SwapBuffers = ImGui_ImplDX10_SwapBuffers;
+}
+
+void ImGui_ImplDX10_ShutdownPlatformInterface()
+{
+    ImGui::DestroyPlatformWindows();
+}
+
 //-----------------------------------------------------------------------------
 
 #endif // #ifndef IMGUI_DISABLE
diff --git a/backends/imgui_impl_dx10.h b/backends/imgui_impl_dx10.h
index e7e798a..39259bd 100644
--- a/backends/imgui_impl_dx10.h
+++ b/backends/imgui_impl_dx10.h
@@ -4,6 +4,7 @@
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'ID3D10ShaderResourceView*' as ImTextureID. Read the FAQ about ImTextureID!
 //  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.
+//  [X] Renderer: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
diff --git a/backends/imgui_impl_dx11.cpp b/backends/imgui_impl_dx11.cpp
index 167bda6..3d7ec7e 100644
--- a/backends/imgui_impl_dx11.cpp
+++ b/backends/imgui_impl_dx11.cpp
@@ -4,6 +4,7 @@
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'ID3D11ShaderResourceView*' as ImTextureID. Read the FAQ about ImTextureID!
 //  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.
+//  [X] Renderer: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
@@ -15,6 +16,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2024-XX-XX: Platform: Added support for multiple windows via the ImGuiPlatformIO interface.
 //  2022-10-11: Using 'nullptr' instead of 'NULL' as per our switch to C++11.
 //  2021-06-29: Reorganized backend to pull data from a single structure to facilitate usage with multiple-contexts (all g_XXXX access changed to bd->XXXX).
 //  2021-05-19: DirectX11: Replaced direct access to ImDrawCmd::TextureId with a call to ImDrawCmd::GetTexID(). (will become a requirement)
@@ -80,6 +82,10 @@
     return ImGui::GetCurrentContext() ? (ImGui_ImplDX11_Data*)ImGui::GetIO().BackendRendererUserData : nullptr;
 }
 
+// Forward Declarations
+static void ImGui_ImplDX11_InitPlatformInterface();
+static void ImGui_ImplDX11_ShutdownPlatformInterface();
+
 // Functions
 static void ImGui_ImplDX11_SetupRenderState(ImDrawData* draw_data, ID3D11DeviceContext* ctx)
 {
@@ -554,6 +560,7 @@
     io.BackendRendererUserData = (void*)bd;
     io.BackendRendererName = "imgui_impl_dx11";
     io.BackendFlags |= ImGuiBackendFlags_RendererHasVtxOffset;  // We can honor the ImDrawCmd::VtxOffset field, allowing for large meshes.
+    io.BackendFlags |= ImGuiBackendFlags_RendererHasViewports;  // We can create multi-viewports on the Renderer side (optional)
 
     // Get factory from device
     IDXGIDevice* pDXGIDevice = nullptr;
@@ -573,6 +580,9 @@
     bd->pd3dDevice->AddRef();
     bd->pd3dDeviceContext->AddRef();
 
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        ImGui_ImplDX11_InitPlatformInterface();
+
     return true;
 }
 
@@ -582,13 +592,14 @@
     IM_ASSERT(bd != nullptr && "No renderer backend to shutdown, or already shutdown?");
     ImGuiIO& io = ImGui::GetIO();
 
+    ImGui_ImplDX11_ShutdownPlatformInterface();
     ImGui_ImplDX11_InvalidateDeviceObjects();
     if (bd->pFactory)             { bd->pFactory->Release(); }
     if (bd->pd3dDevice)           { bd->pd3dDevice->Release(); }
     if (bd->pd3dDeviceContext)    { bd->pd3dDeviceContext->Release(); }
     io.BackendRendererName = nullptr;
     io.BackendRendererUserData = nullptr;
-    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;
+    io.BackendFlags &= ~(ImGuiBackendFlags_RendererHasVtxOffset | ImGuiBackendFlags_RendererHasViewports);
     IM_DELETE(bd);
 }
 
@@ -601,6 +612,129 @@
         ImGui_ImplDX11_CreateDeviceObjects();
 }
 
+//--------------------------------------------------------------------------------------------------------
+// MULTI-VIEWPORT / PLATFORM INTERFACE SUPPORT
+// This is an _advanced_ and _optional_ feature, allowing the backend to create and handle multiple viewports simultaneously.
+// If you are new to dear imgui or creating a new binding for dear imgui, it is recommended that you completely ignore this section first..
+//--------------------------------------------------------------------------------------------------------
+
+// Helper structure we store in the void* RendererUserData field of each ImGuiViewport to easily retrieve our backend data.
+struct ImGui_ImplDX11_ViewportData
+{
+    IDXGISwapChain*                 SwapChain;
+    ID3D11RenderTargetView*         RTView;
+
+    ImGui_ImplDX11_ViewportData()   { SwapChain = nullptr; RTView = nullptr; }
+    ~ImGui_ImplDX11_ViewportData()  { IM_ASSERT(SwapChain == nullptr && RTView == nullptr); }
+};
+
+static void ImGui_ImplDX11_CreateWindow(ImGuiViewport* viewport)
+{
+    ImGui_ImplDX11_Data* bd = ImGui_ImplDX11_GetBackendData();
+    ImGui_ImplDX11_ViewportData* vd = IM_NEW(ImGui_ImplDX11_ViewportData)();
+    viewport->RendererUserData = vd;
+
+    // PlatformHandleRaw should always be a HWND, whereas PlatformHandle might be a higher-level handle (e.g. GLFWWindow*, SDL_Window*).
+    // Some backends will leave PlatformHandleRaw == 0, in which case we assume PlatformHandle will contain the HWND.
+    HWND hwnd = viewport->PlatformHandleRaw ? (HWND)viewport->PlatformHandleRaw : (HWND)viewport->PlatformHandle;
+    IM_ASSERT(hwnd != 0);
+
+    // Create swap chain
+    DXGI_SWAP_CHAIN_DESC sd;
+    ZeroMemory(&sd, sizeof(sd));
+    sd.BufferDesc.Width = (UINT)viewport->Size.x;
+    sd.BufferDesc.Height = (UINT)viewport->Size.y;
+    sd.BufferDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
+    sd.SampleDesc.Count = 1;
+    sd.SampleDesc.Quality = 0;
+    sd.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;
+    sd.BufferCount = 1;
+    sd.OutputWindow = hwnd;
+    sd.Windowed = TRUE;
+    sd.SwapEffect = DXGI_SWAP_EFFECT_DISCARD;
+    sd.Flags = 0;
+
+    IM_ASSERT(vd->SwapChain == nullptr && vd->RTView == nullptr);
+    bd->pFactory->CreateSwapChain(bd->pd3dDevice, &sd, &vd->SwapChain);
+
+    // Create the render target
+    if (vd->SwapChain)
+    {
+        ID3D11Texture2D* pBackBuffer;
+        vd->SwapChain->GetBuffer(0, IID_PPV_ARGS(&pBackBuffer));
+        bd->pd3dDevice->CreateRenderTargetView(pBackBuffer, nullptr, &vd->RTView);
+        pBackBuffer->Release();
+    }
+}
+
+static void ImGui_ImplDX11_DestroyWindow(ImGuiViewport* viewport)
+{
+    // The main viewport (owned by the application) will always have RendererUserData == nullptr since we didn't create the data for it.
+    if (ImGui_ImplDX11_ViewportData* vd = (ImGui_ImplDX11_ViewportData*)viewport->RendererUserData)
+    {
+        if (vd->SwapChain)
+            vd->SwapChain->Release();
+        vd->SwapChain = nullptr;
+        if (vd->RTView)
+            vd->RTView->Release();
+        vd->RTView = nullptr;
+        IM_DELETE(vd);
+    }
+    viewport->RendererUserData = nullptr;
+}
+
+static void ImGui_ImplDX11_SetWindowSize(ImGuiViewport* viewport, ImVec2 size)
+{
+    ImGui_ImplDX11_Data* bd = ImGui_ImplDX11_GetBackendData();
+    ImGui_ImplDX11_ViewportData* vd = (ImGui_ImplDX11_ViewportData*)viewport->RendererUserData;
+    if (vd->RTView)
+    {
+        vd->RTView->Release();
+        vd->RTView = nullptr;
+    }
+    if (vd->SwapChain)
+    {
+        ID3D11Texture2D* pBackBuffer = nullptr;
+        vd->SwapChain->ResizeBuffers(0, (UINT)size.x, (UINT)size.y, DXGI_FORMAT_UNKNOWN, 0);
+        vd->SwapChain->GetBuffer(0, IID_PPV_ARGS(&pBackBuffer));
+        if (pBackBuffer == nullptr) { fprintf(stderr, "ImGui_ImplDX11_SetWindowSize() failed creating buffers.\n"); return; }
+        bd->pd3dDevice->CreateRenderTargetView(pBackBuffer, nullptr, &vd->RTView);
+        pBackBuffer->Release();
+    }
+}
+
+static void ImGui_ImplDX11_RenderWindow(ImGuiViewport* viewport, void*)
+{
+    ImGui_ImplDX11_Data* bd = ImGui_ImplDX11_GetBackendData();
+    ImGui_ImplDX11_ViewportData* vd = (ImGui_ImplDX11_ViewportData*)viewport->RendererUserData;
+    ImVec4 clear_color = ImVec4(0.0f, 0.0f, 0.0f, 1.0f);
+    bd->pd3dDeviceContext->OMSetRenderTargets(1, &vd->RTView, nullptr);
+    if (!(viewport->Flags & ImGuiViewportFlags_NoRendererClear))
+        bd->pd3dDeviceContext->ClearRenderTargetView(vd->RTView, (float*)&clear_color);
+    ImGui_ImplDX11_RenderDrawData(viewport->DrawData);
+}
+
+static void ImGui_ImplDX11_SwapBuffers(ImGuiViewport* viewport, void*)
+{
+    ImGui_ImplDX11_ViewportData* vd = (ImGui_ImplDX11_ViewportData*)viewport->RendererUserData;
+    vd->SwapChain->Present(0, 0); // Present without vsync
+}
+
+static void ImGui_ImplDX11_InitPlatformInterface()
+{
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    platform_io.Renderer_CreateWindow = ImGui_ImplDX11_CreateWindow;
+    platform_io.Renderer_DestroyWindow = ImGui_ImplDX11_DestroyWindow;
+    platform_io.Renderer_SetWindowSize = ImGui_ImplDX11_SetWindowSize;
+    platform_io.Renderer_RenderWindow = ImGui_ImplDX11_RenderWindow;
+    platform_io.Renderer_SwapBuffers = ImGui_ImplDX11_SwapBuffers;
+}
+
+static void ImGui_ImplDX11_ShutdownPlatformInterface()
+{
+    ImGui::DestroyPlatformWindows();
+}
+
 //-----------------------------------------------------------------------------
 
 #endif // #ifndef IMGUI_DISABLE
diff --git a/backends/imgui_impl_dx11.h b/backends/imgui_impl_dx11.h
index 20887f3..1713fbd 100644
--- a/backends/imgui_impl_dx11.h
+++ b/backends/imgui_impl_dx11.h
@@ -4,6 +4,7 @@
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'ID3D11ShaderResourceView*' as ImTextureID. Read the FAQ about ImTextureID!
 //  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.
+//  [X] Renderer: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
diff --git a/backends/imgui_impl_dx12.cpp b/backends/imgui_impl_dx12.cpp
index 32f1622..cde8981 100644
--- a/backends/imgui_impl_dx12.cpp
+++ b/backends/imgui_impl_dx12.cpp
@@ -4,6 +4,8 @@
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'D3D12_GPU_DESCRIPTOR_HANDLE' as ImTextureID. Read the FAQ about ImTextureID!
 //  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.
+//  [X] Renderer: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
+//      FIXME: The transition from removing a viewport and moving the window in an existing hosted viewport tends to flicker.
 
 // Important: to compile on 32-bit systems, this backend requires code to be compiled with '#define ImTextureID ImU64'.
 // This is because we need ImTextureID to carry a 64-bit value and by default ImTextureID is defined as void*.
@@ -23,6 +25,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2024-XX-XX: Platform: Added support for multiple windows via the ImGuiPlatformIO interface.
 //  2022-10-11: Using 'nullptr' instead of 'NULL' as per our switch to C++11.
 //  2021-06-29: Reorganized backend to pull data from a single structure to facilitate usage with multiple-contexts (all g_XXXX access changed to bd->XXXX).
 //  2021-05-19: DirectX12: Replaced direct access to ImDrawCmd::TextureId with a call to ImDrawCmd::GetTexID(). (will become a requirement)
@@ -54,7 +57,6 @@
 #endif
 
 // DirectX data
-struct ImGui_ImplDX12_RenderBuffers;
 struct ImGui_ImplDX12_Data
 {
     ID3D12Device*               pd3dDevice;
@@ -67,10 +69,7 @@
     ID3D12DescriptorHeap*       pd3dSrvDescHeap;
     UINT                        numFramesInFlight;
 
-    ImGui_ImplDX12_RenderBuffers* pFrameResources;
-    UINT                        frameIndex;
-
-    ImGui_ImplDX12_Data()       { memset((void*)this, 0, sizeof(*this)); frameIndex = UINT_MAX; }
+    ImGui_ImplDX12_Data()       { memset((void*)this, 0, sizeof(*this)); }
 };
 
 // Backend data stored in io.BackendRendererUserData to allow support for multiple Dear ImGui contexts
@@ -89,11 +88,88 @@
     int                 VertexBufferSize;
 };
 
+// Buffers used for secondary viewports created by the multi-viewports systems
+struct ImGui_ImplDX12_FrameContext
+{
+    ID3D12CommandAllocator*         CommandAllocator;
+    ID3D12Resource*                 RenderTarget;
+    D3D12_CPU_DESCRIPTOR_HANDLE     RenderTargetCpuDescriptors;
+};
+
+// Helper structure we store in the void* RendererUserData field of each ImGuiViewport to easily retrieve our backend data.
+// Main viewport created by application will only use the Resources field.
+// Secondary viewports created by this backend will use all the fields (including Window fields),
+struct ImGui_ImplDX12_ViewportData
+{
+    // Window
+    ID3D12CommandQueue*             CommandQueue;
+    ID3D12GraphicsCommandList*      CommandList;
+    ID3D12DescriptorHeap*           RtvDescHeap;
+    IDXGISwapChain3*                SwapChain;
+    ID3D12Fence*                    Fence;
+    UINT64                          FenceSignaledValue;
+    HANDLE                          FenceEvent;
+    UINT                            NumFramesInFlight;
+    ImGui_ImplDX12_FrameContext*    FrameCtx;
+
+    // Render buffers
+    UINT                            FrameIndex;
+    ImGui_ImplDX12_RenderBuffers*   FrameRenderBuffers;
+
+    ImGui_ImplDX12_ViewportData(UINT num_frames_in_flight)
+    {
+        CommandQueue = nullptr;
+        CommandList = nullptr;
+        RtvDescHeap = nullptr;
+        SwapChain = nullptr;
+        Fence = nullptr;
+        FenceSignaledValue = 0;
+        FenceEvent = nullptr;
+        NumFramesInFlight = num_frames_in_flight;
+        FrameCtx = new ImGui_ImplDX12_FrameContext[NumFramesInFlight];
+        FrameIndex = UINT_MAX;
+        FrameRenderBuffers = new ImGui_ImplDX12_RenderBuffers[NumFramesInFlight];
+
+        for (UINT i = 0; i < NumFramesInFlight; ++i)
+        {
+            FrameCtx[i].CommandAllocator = nullptr;
+            FrameCtx[i].RenderTarget = nullptr;
+
+            // Create buffers with a default size (they will later be grown as needed)
+            FrameRenderBuffers[i].IndexBuffer = nullptr;
+            FrameRenderBuffers[i].VertexBuffer = nullptr;
+            FrameRenderBuffers[i].VertexBufferSize = 5000;
+            FrameRenderBuffers[i].IndexBufferSize = 10000;
+        }
+    }
+    ~ImGui_ImplDX12_ViewportData()
+    {
+        IM_ASSERT(CommandQueue == nullptr && CommandList == nullptr);
+        IM_ASSERT(RtvDescHeap == nullptr);
+        IM_ASSERT(SwapChain == nullptr);
+        IM_ASSERT(Fence == nullptr);
+        IM_ASSERT(FenceEvent == nullptr);
+
+        for (UINT i = 0; i < NumFramesInFlight; ++i)
+        {
+            IM_ASSERT(FrameCtx[i].CommandAllocator == nullptr && FrameCtx[i].RenderTarget == nullptr);
+            IM_ASSERT(FrameRenderBuffers[i].IndexBuffer == nullptr && FrameRenderBuffers[i].VertexBuffer == nullptr);
+        }
+
+        delete[] FrameCtx; FrameCtx = nullptr;
+        delete[] FrameRenderBuffers; FrameRenderBuffers = nullptr;
+    }
+};
+
 struct VERTEX_CONSTANT_BUFFER_DX12
 {
     float   mvp[4][4];
 };
 
+// Forward Declarations
+static void ImGui_ImplDX12_InitPlatformInterface();
+static void ImGui_ImplDX12_ShutdownPlatformInterface();
+
 // Functions
 static void ImGui_ImplDX12_SetupRenderState(ImDrawData* draw_data, ID3D12GraphicsCommandList* ctx, ImGui_ImplDX12_RenderBuffers* fr)
 {
@@ -167,11 +243,10 @@
     if (draw_data->DisplaySize.x <= 0.0f || draw_data->DisplaySize.y <= 0.0f)
         return;
 
-    // FIXME: I'm assuming that this only gets called once per frame!
-    // If not, we can't just re-allocate the IB or VB, we'll have to do a proper allocator.
     ImGui_ImplDX12_Data* bd = ImGui_ImplDX12_GetBackendData();
-    bd->frameIndex = bd->frameIndex + 1;
-    ImGui_ImplDX12_RenderBuffers* fr = &bd->pFrameResources[bd->frameIndex % bd->numFramesInFlight];
+    ImGui_ImplDX12_ViewportData* vd = (ImGui_ImplDX12_ViewportData*)draw_data->OwnerViewport->RendererUserData;
+    vd->FrameIndex++;
+    ImGui_ImplDX12_RenderBuffers* fr = &vd->FrameRenderBuffers[vd->FrameIndex % bd->numFramesInFlight];
 
     // Create and grow vertex/index buffers if needed
     if (fr->VertexBuffer == nullptr || fr->VertexBufferSize < draw_data->TotalVtxCount)
@@ -678,6 +753,13 @@
     return true;
 }
 
+static void ImGui_ImplDX12_DestroyRenderBuffers(ImGui_ImplDX12_RenderBuffers* render_buffers)
+{
+    SafeRelease(render_buffers->IndexBuffer);
+    SafeRelease(render_buffers->VertexBuffer);
+    render_buffers->IndexBufferSize = render_buffers->VertexBufferSize = 0;
+}
+
 void    ImGui_ImplDX12_InvalidateDeviceObjects()
 {
     ImGui_ImplDX12_Data* bd = ImGui_ImplDX12_GetBackendData();
@@ -689,13 +771,6 @@
     SafeRelease(bd->pPipelineState);
     SafeRelease(bd->pFontTextureResource);
     io.Fonts->SetTexID(0); // We copied bd->pFontTextureView to io.Fonts->TexID so let's clear that as well.
-
-    for (UINT i = 0; i < bd->numFramesInFlight; i++)
-    {
-        ImGui_ImplDX12_RenderBuffers* fr = &bd->pFrameResources[i];
-        SafeRelease(fr->IndexBuffer);
-        SafeRelease(fr->VertexBuffer);
-    }
 }
 
 bool ImGui_ImplDX12_Init(ID3D12Device* device, int num_frames_in_flight, DXGI_FORMAT rtv_format, ID3D12DescriptorHeap* cbv_srv_heap,
@@ -710,25 +785,21 @@
     io.BackendRendererUserData = (void*)bd;
     io.BackendRendererName = "imgui_impl_dx12";
     io.BackendFlags |= ImGuiBackendFlags_RendererHasVtxOffset;  // We can honor the ImDrawCmd::VtxOffset field, allowing for large meshes.
+    io.BackendFlags |= ImGuiBackendFlags_RendererHasViewports;  // We can create multi-viewports on the Renderer side (optional)
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        ImGui_ImplDX12_InitPlatformInterface();
 
     bd->pd3dDevice = device;
     bd->RTVFormat = rtv_format;
     bd->hFontSrvCpuDescHandle = font_srv_cpu_desc_handle;
     bd->hFontSrvGpuDescHandle = font_srv_gpu_desc_handle;
-    bd->pFrameResources = new ImGui_ImplDX12_RenderBuffers[num_frames_in_flight];
     bd->numFramesInFlight = num_frames_in_flight;
     bd->pd3dSrvDescHeap = cbv_srv_heap;
-    bd->frameIndex = UINT_MAX;
 
-    // Create buffers with a default size (they will later be grown as needed)
-    for (int i = 0; i < num_frames_in_flight; i++)
-    {
-        ImGui_ImplDX12_RenderBuffers* fr = &bd->pFrameResources[i];
-        fr->IndexBuffer = nullptr;
-        fr->VertexBuffer = nullptr;
-        fr->IndexBufferSize = 10000;
-        fr->VertexBufferSize = 5000;
-    }
+    // Create a dummy ImGui_ImplDX12_ViewportData holder for the main viewport,
+    // Since this is created and managed by the application, we will only use the ->Resources[] fields.
+    ImGuiViewport* main_viewport = ImGui::GetMainViewport();
+    main_viewport->RendererUserData = IM_NEW(ImGui_ImplDX12_ViewportData)(bd->numFramesInFlight);
 
     return true;
 }
@@ -739,12 +810,24 @@
     IM_ASSERT(bd != nullptr && "No renderer backend to shutdown, or already shutdown?");
     ImGuiIO& io = ImGui::GetIO();
 
+    // Manually delete main viewport render resources in-case we haven't initialized for viewports
+    ImGuiViewport* main_viewport = ImGui::GetMainViewport();
+    if (ImGui_ImplDX12_ViewportData* vd = (ImGui_ImplDX12_ViewportData*)main_viewport->RendererUserData)
+    {
+        // We could just call ImGui_ImplDX12_DestroyWindow(main_viewport) as a convenience but that would be misleading since we only use data->Resources[]
+        for (UINT i = 0; i < bd->numFramesInFlight; i++)
+            ImGui_ImplDX12_DestroyRenderBuffers(&vd->FrameRenderBuffers[i]);
+        IM_DELETE(vd);
+        main_viewport->RendererUserData = nullptr;
+    }
+
     // Clean up windows and device objects
+    ImGui_ImplDX12_ShutdownPlatformInterface();
     ImGui_ImplDX12_InvalidateDeviceObjects();
-    delete[] bd->pFrameResources;
+
     io.BackendRendererName = nullptr;
     io.BackendRendererUserData = nullptr;
-    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;
+    io.BackendFlags &= ~(ImGuiBackendFlags_RendererHasVtxOffset | ImGuiBackendFlags_RendererHasViewports);
     IM_DELETE(bd);
 }
 
@@ -757,6 +840,246 @@
         ImGui_ImplDX12_CreateDeviceObjects();
 }
 
+//--------------------------------------------------------------------------------------------------------
+// MULTI-VIEWPORT / PLATFORM INTERFACE SUPPORT
+// This is an _advanced_ and _optional_ feature, allowing the backend to create and handle multiple viewports simultaneously.
+// If you are new to dear imgui or creating a new binding for dear imgui, it is recommended that you completely ignore this section first..
+//--------------------------------------------------------------------------------------------------------
+
+static void ImGui_ImplDX12_CreateWindow(ImGuiViewport* viewport)
+{
+    ImGui_ImplDX12_Data* bd = ImGui_ImplDX12_GetBackendData();
+    ImGui_ImplDX12_ViewportData* vd = IM_NEW(ImGui_ImplDX12_ViewportData)(bd->numFramesInFlight);
+    viewport->RendererUserData = vd;
+
+    // PlatformHandleRaw should always be a HWND, whereas PlatformHandle might be a higher-level handle (e.g. GLFWWindow*, SDL_Window*).
+    // Some backends will leave PlatformHandleRaw == 0, in which case we assume PlatformHandle will contain the HWND.
+    HWND hwnd = viewport->PlatformHandleRaw ? (HWND)viewport->PlatformHandleRaw : (HWND)viewport->PlatformHandle;
+    IM_ASSERT(hwnd != 0);
+
+    vd->FrameIndex = UINT_MAX;
+
+    // Create command queue.
+    D3D12_COMMAND_QUEUE_DESC queue_desc = {};
+    queue_desc.Flags = D3D12_COMMAND_QUEUE_FLAG_NONE;
+    queue_desc.Type = D3D12_COMMAND_LIST_TYPE_DIRECT;
+
+    HRESULT res = S_OK;
+    res = bd->pd3dDevice->CreateCommandQueue(&queue_desc, IID_PPV_ARGS(&vd->CommandQueue));
+    IM_ASSERT(res == S_OK);
+
+    // Create command allocator.
+    for (UINT i = 0; i < bd->numFramesInFlight; ++i)
+    {
+        res = bd->pd3dDevice->CreateCommandAllocator(D3D12_COMMAND_LIST_TYPE_DIRECT, IID_PPV_ARGS(&vd->FrameCtx[i].CommandAllocator));
+        IM_ASSERT(res == S_OK);
+    }
+
+    // Create command list.
+    res = bd->pd3dDevice->CreateCommandList(0, D3D12_COMMAND_LIST_TYPE_DIRECT, vd->FrameCtx[0].CommandAllocator, nullptr, IID_PPV_ARGS(&vd->CommandList));
+    IM_ASSERT(res == S_OK);
+    vd->CommandList->Close();
+
+    // Create fence.
+    res = bd->pd3dDevice->CreateFence(0, D3D12_FENCE_FLAG_NONE, IID_PPV_ARGS(&vd->Fence));
+    IM_ASSERT(res == S_OK);
+
+    vd->FenceEvent = CreateEvent(nullptr, FALSE, FALSE, nullptr);
+    IM_ASSERT(vd->FenceEvent != nullptr);
+
+    // Create swap chain
+    // FIXME-VIEWPORT: May want to copy/inherit swap chain settings from the user/application.
+    DXGI_SWAP_CHAIN_DESC1 sd1;
+    ZeroMemory(&sd1, sizeof(sd1));
+    sd1.BufferCount = bd->numFramesInFlight;
+    sd1.Width = (UINT)viewport->Size.x;
+    sd1.Height = (UINT)viewport->Size.y;
+    sd1.Format = bd->RTVFormat;
+    sd1.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;
+    sd1.SampleDesc.Count = 1;
+    sd1.SampleDesc.Quality = 0;
+    sd1.SwapEffect = DXGI_SWAP_EFFECT_FLIP_DISCARD;
+    sd1.AlphaMode = DXGI_ALPHA_MODE_UNSPECIFIED;
+    sd1.Scaling = DXGI_SCALING_NONE;
+    sd1.Stereo = FALSE;
+
+    IDXGIFactory4* dxgi_factory = nullptr;
+    res = ::CreateDXGIFactory1(IID_PPV_ARGS(&dxgi_factory));
+    IM_ASSERT(res == S_OK);
+
+    IDXGISwapChain1* swap_chain = nullptr;
+    res = dxgi_factory->CreateSwapChainForHwnd(vd->CommandQueue, hwnd, &sd1, nullptr, nullptr, &swap_chain);
+    IM_ASSERT(res == S_OK);
+
+    dxgi_factory->Release();
+
+    // Or swapChain.As(&mSwapChain)
+    IM_ASSERT(vd->SwapChain == nullptr);
+    swap_chain->QueryInterface(IID_PPV_ARGS(&vd->SwapChain));
+    swap_chain->Release();
+
+    // Create the render targets
+    if (vd->SwapChain)
+    {
+        D3D12_DESCRIPTOR_HEAP_DESC desc = {};
+        desc.Type = D3D12_DESCRIPTOR_HEAP_TYPE_RTV;
+        desc.NumDescriptors = bd->numFramesInFlight;
+        desc.Flags = D3D12_DESCRIPTOR_HEAP_FLAG_NONE;
+        desc.NodeMask = 1;
+
+        HRESULT hr = bd->pd3dDevice->CreateDescriptorHeap(&desc, IID_PPV_ARGS(&vd->RtvDescHeap));
+        IM_ASSERT(hr == S_OK);
+
+        SIZE_T rtv_descriptor_size = bd->pd3dDevice->GetDescriptorHandleIncrementSize(D3D12_DESCRIPTOR_HEAP_TYPE_RTV);
+        D3D12_CPU_DESCRIPTOR_HANDLE rtv_handle = vd->RtvDescHeap->GetCPUDescriptorHandleForHeapStart();
+        for (UINT i = 0; i < bd->numFramesInFlight; i++)
+        {
+            vd->FrameCtx[i].RenderTargetCpuDescriptors = rtv_handle;
+            rtv_handle.ptr += rtv_descriptor_size;
+        }
+
+        ID3D12Resource* back_buffer;
+        for (UINT i = 0; i < bd->numFramesInFlight; i++)
+        {
+            IM_ASSERT(vd->FrameCtx[i].RenderTarget == nullptr);
+            vd->SwapChain->GetBuffer(i, IID_PPV_ARGS(&back_buffer));
+            bd->pd3dDevice->CreateRenderTargetView(back_buffer, nullptr, vd->FrameCtx[i].RenderTargetCpuDescriptors);
+            vd->FrameCtx[i].RenderTarget = back_buffer;
+        }
+    }
+
+    for (UINT i = 0; i < bd->numFramesInFlight; i++)
+        ImGui_ImplDX12_DestroyRenderBuffers(&vd->FrameRenderBuffers[i]);
+}
+
+static void ImGui_WaitForPendingOperations(ImGui_ImplDX12_ViewportData* vd)
+{
+    HRESULT hr = S_FALSE;
+    if (vd && vd->CommandQueue && vd->Fence && vd->FenceEvent)
+    {
+        hr = vd->CommandQueue->Signal(vd->Fence, ++vd->FenceSignaledValue);
+        IM_ASSERT(hr == S_OK);
+        ::WaitForSingleObject(vd->FenceEvent, 0); // Reset any forgotten waits
+        hr = vd->Fence->SetEventOnCompletion(vd->FenceSignaledValue, vd->FenceEvent);
+        IM_ASSERT(hr == S_OK);
+        ::WaitForSingleObject(vd->FenceEvent, INFINITE);
+    }
+}
+
+static void ImGui_ImplDX12_DestroyWindow(ImGuiViewport* viewport)
+{
+    // The main viewport (owned by the application) will always have RendererUserData == 0 since we didn't create the data for it.
+    ImGui_ImplDX12_Data* bd = ImGui_ImplDX12_GetBackendData();
+    if (ImGui_ImplDX12_ViewportData* vd = (ImGui_ImplDX12_ViewportData*)viewport->RendererUserData)
+    {
+        ImGui_WaitForPendingOperations(vd);
+
+        SafeRelease(vd->CommandQueue);
+        SafeRelease(vd->CommandList);
+        SafeRelease(vd->SwapChain);
+        SafeRelease(vd->RtvDescHeap);
+        SafeRelease(vd->Fence);
+        ::CloseHandle(vd->FenceEvent);
+        vd->FenceEvent = nullptr;
+
+        for (UINT i = 0; i < bd->numFramesInFlight; i++)
+        {
+            SafeRelease(vd->FrameCtx[i].RenderTarget);
+            SafeRelease(vd->FrameCtx[i].CommandAllocator);
+            ImGui_ImplDX12_DestroyRenderBuffers(&vd->FrameRenderBuffers[i]);
+        }
+        IM_DELETE(vd);
+    }
+    viewport->RendererUserData = nullptr;
+}
+
+static void ImGui_ImplDX12_SetWindowSize(ImGuiViewport* viewport, ImVec2 size)
+{
+    ImGui_ImplDX12_Data* bd = ImGui_ImplDX12_GetBackendData();
+    ImGui_ImplDX12_ViewportData* vd = (ImGui_ImplDX12_ViewportData*)viewport->RendererUserData;
+
+    ImGui_WaitForPendingOperations(vd);
+
+    for (UINT i = 0; i < bd->numFramesInFlight; i++)
+        SafeRelease(vd->FrameCtx[i].RenderTarget);
+
+    if (vd->SwapChain)
+    {
+        ID3D12Resource* back_buffer = nullptr;
+        vd->SwapChain->ResizeBuffers(0, (UINT)size.x, (UINT)size.y, DXGI_FORMAT_UNKNOWN, 0);
+        for (UINT i = 0; i < bd->numFramesInFlight; i++)
+        {
+            vd->SwapChain->GetBuffer(i, IID_PPV_ARGS(&back_buffer));
+            bd->pd3dDevice->CreateRenderTargetView(back_buffer, nullptr, vd->FrameCtx[i].RenderTargetCpuDescriptors);
+            vd->FrameCtx[i].RenderTarget = back_buffer;
+        }
+    }
+}
+
+static void ImGui_ImplDX12_RenderWindow(ImGuiViewport* viewport, void*)
+{
+    ImGui_ImplDX12_Data* bd = ImGui_ImplDX12_GetBackendData();
+    ImGui_ImplDX12_ViewportData* vd = (ImGui_ImplDX12_ViewportData*)viewport->RendererUserData;
+
+    ImGui_ImplDX12_FrameContext* frame_context = &vd->FrameCtx[vd->FrameIndex % bd->numFramesInFlight];
+    UINT back_buffer_idx = vd->SwapChain->GetCurrentBackBufferIndex();
+
+    const ImVec4 clear_color = ImVec4(0.0f, 0.0f, 0.0f, 1.0f);
+    D3D12_RESOURCE_BARRIER barrier = {};
+    barrier.Type = D3D12_RESOURCE_BARRIER_TYPE_TRANSITION;
+    barrier.Flags = D3D12_RESOURCE_BARRIER_FLAG_NONE;
+    barrier.Transition.pResource = vd->FrameCtx[back_buffer_idx].RenderTarget;
+    barrier.Transition.Subresource = D3D12_RESOURCE_BARRIER_ALL_SUBRESOURCES;
+    barrier.Transition.StateBefore = D3D12_RESOURCE_STATE_PRESENT;
+    barrier.Transition.StateAfter = D3D12_RESOURCE_STATE_RENDER_TARGET;
+
+    // Draw
+    ID3D12GraphicsCommandList* cmd_list = vd->CommandList;
+
+    frame_context->CommandAllocator->Reset();
+    cmd_list->Reset(frame_context->CommandAllocator, nullptr);
+    cmd_list->ResourceBarrier(1, &barrier);
+    cmd_list->OMSetRenderTargets(1, &vd->FrameCtx[back_buffer_idx].RenderTargetCpuDescriptors, FALSE, nullptr);
+    if (!(viewport->Flags & ImGuiViewportFlags_NoRendererClear))
+        cmd_list->ClearRenderTargetView(vd->FrameCtx[back_buffer_idx].RenderTargetCpuDescriptors, (float*)&clear_color, 0, nullptr);
+    cmd_list->SetDescriptorHeaps(1, &bd->pd3dSrvDescHeap);
+
+    ImGui_ImplDX12_RenderDrawData(viewport->DrawData, cmd_list);
+
+    barrier.Transition.StateBefore = D3D12_RESOURCE_STATE_RENDER_TARGET;
+    barrier.Transition.StateAfter = D3D12_RESOURCE_STATE_PRESENT;
+    cmd_list->ResourceBarrier(1, &barrier);
+    cmd_list->Close();
+
+    vd->CommandQueue->Wait(vd->Fence, vd->FenceSignaledValue);
+    vd->CommandQueue->ExecuteCommandLists(1, (ID3D12CommandList* const*)&cmd_list);
+    vd->CommandQueue->Signal(vd->Fence, ++vd->FenceSignaledValue);
+}
+
+static void ImGui_ImplDX12_SwapBuffers(ImGuiViewport* viewport, void*)
+{
+    ImGui_ImplDX12_ViewportData* vd = (ImGui_ImplDX12_ViewportData*)viewport->RendererUserData;
+
+    vd->SwapChain->Present(0, 0);
+    while (vd->Fence->GetCompletedValue() < vd->FenceSignaledValue)
+        ::SwitchToThread();
+}
+
+void ImGui_ImplDX12_InitPlatformInterface()
+{
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    platform_io.Renderer_CreateWindow = ImGui_ImplDX12_CreateWindow;
+    platform_io.Renderer_DestroyWindow = ImGui_ImplDX12_DestroyWindow;
+    platform_io.Renderer_SetWindowSize = ImGui_ImplDX12_SetWindowSize;
+    platform_io.Renderer_RenderWindow = ImGui_ImplDX12_RenderWindow;
+    platform_io.Renderer_SwapBuffers = ImGui_ImplDX12_SwapBuffers;
+}
+
+void ImGui_ImplDX12_ShutdownPlatformInterface()
+{
+    ImGui::DestroyPlatformWindows();
+}
+
 //-----------------------------------------------------------------------------
 
 #endif // #ifndef IMGUI_DISABLE
diff --git a/backends/imgui_impl_dx12.h b/backends/imgui_impl_dx12.h
index 8710910..f304cca 100644
--- a/backends/imgui_impl_dx12.h
+++ b/backends/imgui_impl_dx12.h
@@ -4,6 +4,7 @@
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'D3D12_GPU_DESCRIPTOR_HANDLE' as ImTextureID. Read the FAQ about ImTextureID!
 //  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.
+//  [X] Renderer: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
 
 // Important: to compile on 32-bit systems, this backend requires code to be compiled with '#define ImTextureID ImU64'.
 // See imgui_impl_dx12.cpp file for details.
diff --git a/backends/imgui_impl_dx9.cpp b/backends/imgui_impl_dx9.cpp
index 3eff9ab..59475d2 100644
--- a/backends/imgui_impl_dx9.cpp
+++ b/backends/imgui_impl_dx9.cpp
@@ -4,6 +4,7 @@
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'LPDIRECT3DTEXTURE9' as ImTextureID. Read the FAQ about ImTextureID!
 //  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.
+//  [X] Renderer: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
@@ -15,6 +16,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2024-XX-XX: Platform: Added support for multiple windows via the ImGuiPlatformIO interface.
 //  2024-02-12: DirectX9: Using RGBA format when supported by the driver to avoid CPU side conversion. (#6575)
 //  2022-10-11: Using 'nullptr' instead of 'NULL' as per our switch to C++11.
 //  2021-06-29: Reorganized backend to pull data from a single structure to facilitate usage with multiple-contexts (all g_XXXX access changed to bd->XXXX).
@@ -76,6 +78,12 @@
     return ImGui::GetCurrentContext() ? (ImGui_ImplDX9_Data*)ImGui::GetIO().BackendRendererUserData : nullptr;
 }
 
+// Forward Declarations
+static void ImGui_ImplDX9_InitPlatformInterface();
+static void ImGui_ImplDX9_ShutdownPlatformInterface();
+static void ImGui_ImplDX9_CreateDeviceObjectsForPlatformWindows();
+static void ImGui_ImplDX9_InvalidateDeviceObjectsForPlatformWindows();
+
 // Functions
 static void ImGui_ImplDX9_SetupRenderState(ImDrawData* draw_data)
 {
@@ -272,6 +280,11 @@
         global_vtx_offset += cmd_list->VtxBuffer.Size;
     }
 
+    // When using multi-viewports, it appears that there's an odd logic in DirectX9 which prevent subsequent windows
+    // from rendering until the first window submits at least one draw call, even once. That's our workaround. (see #2560)
+    if (global_vtx_offset == 0)
+        bd->pd3dDevice->DrawIndexedPrimitive(D3DPT_TRIANGLELIST, 0, 0, 0, 0, 0);
+
     // Restore the DX9 transform
     bd->pd3dDevice->SetTransform(D3DTS_WORLD, &last_world);
     bd->pd3dDevice->SetTransform(D3DTS_VIEW, &last_view);
@@ -293,10 +306,14 @@
     io.BackendRendererUserData = (void*)bd;
     io.BackendRendererName = "imgui_impl_dx9";
     io.BackendFlags |= ImGuiBackendFlags_RendererHasVtxOffset;  // We can honor the ImDrawCmd::VtxOffset field, allowing for large meshes.
+    io.BackendFlags |= ImGuiBackendFlags_RendererHasViewports;  // We can create multi-viewports on the Renderer side (optional)
 
     bd->pd3dDevice = device;
     bd->pd3dDevice->AddRef();
 
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        ImGui_ImplDX9_InitPlatformInterface();
+
     return true;
 }
 
@@ -306,11 +323,12 @@
     IM_ASSERT(bd != nullptr && "No renderer backend to shutdown, or already shutdown?");
     ImGuiIO& io = ImGui::GetIO();
 
+    ImGui_ImplDX9_ShutdownPlatformInterface();
     ImGui_ImplDX9_InvalidateDeviceObjects();
     if (bd->pd3dDevice) { bd->pd3dDevice->Release(); }
     io.BackendRendererName = nullptr;
     io.BackendRendererUserData = nullptr;
-    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;
+    io.BackendFlags &= ~(ImGuiBackendFlags_RendererHasVtxOffset | ImGuiBackendFlags_RendererHasViewports);
     IM_DELETE(bd);
 }
 
@@ -384,6 +402,7 @@
         return false;
     if (!ImGui_ImplDX9_CreateFontsTexture())
         return false;
+    ImGui_ImplDX9_CreateDeviceObjectsForPlatformWindows();
     return true;
 }
 
@@ -395,6 +414,7 @@
     if (bd->pVB) { bd->pVB->Release(); bd->pVB = nullptr; }
     if (bd->pIB) { bd->pIB->Release(); bd->pIB = nullptr; }
     if (bd->FontTexture) { bd->FontTexture->Release(); bd->FontTexture = nullptr; ImGui::GetIO().Fonts->SetTexID(0); } // We copied bd->pFontTextureView to io.Fonts->TexID so let's clear that as well.
+    ImGui_ImplDX9_InvalidateDeviceObjectsForPlatformWindows();
 }
 
 void ImGui_ImplDX9_NewFrame()
@@ -406,6 +426,148 @@
         ImGui_ImplDX9_CreateDeviceObjects();
 }
 
+//--------------------------------------------------------------------------------------------------------
+// MULTI-VIEWPORT / PLATFORM INTERFACE SUPPORT
+// This is an _advanced_ and _optional_ feature, allowing the backend to create and handle multiple viewports simultaneously.
+// If you are new to dear imgui or creating a new binding for dear imgui, it is recommended that you completely ignore this section first..
+//--------------------------------------------------------------------------------------------------------
+
+// Helper structure we store in the void* RendererUserData field of each ImGuiViewport to easily retrieve our backend data.
+struct ImGui_ImplDX9_ViewportData
+{
+    IDirect3DSwapChain9*    SwapChain;
+    D3DPRESENT_PARAMETERS   d3dpp;
+
+    ImGui_ImplDX9_ViewportData()  { SwapChain = nullptr; ZeroMemory(&d3dpp, sizeof(D3DPRESENT_PARAMETERS)); }
+    ~ImGui_ImplDX9_ViewportData() { IM_ASSERT(SwapChain == nullptr); }
+};
+
+static void ImGui_ImplDX9_CreateWindow(ImGuiViewport* viewport)
+{
+    ImGui_ImplDX9_Data* bd = ImGui_ImplDX9_GetBackendData();
+    ImGui_ImplDX9_ViewportData* vd = IM_NEW(ImGui_ImplDX9_ViewportData)();
+    viewport->RendererUserData = vd;
+
+    // PlatformHandleRaw should always be a HWND, whereas PlatformHandle might be a higher-level handle (e.g. GLFWWindow*, SDL_Window*).
+    // Some backends will leave PlatformHandleRaw == 0, in which case we assume PlatformHandle will contain the HWND.
+    HWND hwnd = viewport->PlatformHandleRaw ? (HWND)viewport->PlatformHandleRaw : (HWND)viewport->PlatformHandle;
+    IM_ASSERT(hwnd != 0);
+
+    ZeroMemory(&vd->d3dpp, sizeof(D3DPRESENT_PARAMETERS));
+    vd->d3dpp.Windowed = TRUE;
+    vd->d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
+    vd->d3dpp.BackBufferWidth = (UINT)viewport->Size.x;
+    vd->d3dpp.BackBufferHeight = (UINT)viewport->Size.y;
+    vd->d3dpp.BackBufferFormat = D3DFMT_UNKNOWN;
+    vd->d3dpp.hDeviceWindow = hwnd;
+    vd->d3dpp.EnableAutoDepthStencil = FALSE;
+    vd->d3dpp.AutoDepthStencilFormat = D3DFMT_D16;
+    vd->d3dpp.PresentationInterval = D3DPRESENT_INTERVAL_IMMEDIATE;   // Present without vsync
+
+    HRESULT hr = bd->pd3dDevice->CreateAdditionalSwapChain(&vd->d3dpp, &vd->SwapChain); IM_UNUSED(hr);
+    IM_ASSERT(hr == D3D_OK);
+    IM_ASSERT(vd->SwapChain != nullptr);
+}
+
+static void ImGui_ImplDX9_DestroyWindow(ImGuiViewport* viewport)
+{
+    // The main viewport (owned by the application) will always have RendererUserData == 0 since we didn't create the data for it.
+    if (ImGui_ImplDX9_ViewportData* vd = (ImGui_ImplDX9_ViewportData*)viewport->RendererUserData)
+    {
+        if (vd->SwapChain)
+            vd->SwapChain->Release();
+        vd->SwapChain = nullptr;
+        ZeroMemory(&vd->d3dpp, sizeof(D3DPRESENT_PARAMETERS));
+        IM_DELETE(vd);
+    }
+    viewport->RendererUserData = nullptr;
+}
+
+static void ImGui_ImplDX9_SetWindowSize(ImGuiViewport* viewport, ImVec2 size)
+{
+    ImGui_ImplDX9_Data* bd = ImGui_ImplDX9_GetBackendData();
+    ImGui_ImplDX9_ViewportData* vd = (ImGui_ImplDX9_ViewportData*)viewport->RendererUserData;
+    if (vd->SwapChain)
+    {
+        vd->SwapChain->Release();
+        vd->SwapChain = nullptr;
+        vd->d3dpp.BackBufferWidth = (UINT)size.x;
+        vd->d3dpp.BackBufferHeight = (UINT)size.y;
+        HRESULT hr = bd->pd3dDevice->CreateAdditionalSwapChain(&vd->d3dpp, &vd->SwapChain); IM_UNUSED(hr);
+        IM_ASSERT(hr == D3D_OK);
+    }
+}
+
+static void ImGui_ImplDX9_RenderWindow(ImGuiViewport* viewport, void*)
+{
+    ImGui_ImplDX9_Data* bd = ImGui_ImplDX9_GetBackendData();
+    ImGui_ImplDX9_ViewportData* vd = (ImGui_ImplDX9_ViewportData*)viewport->RendererUserData;
+    ImVec4 clear_color = ImVec4(0.0f, 0.0f, 0.0f, 1.0f);
+
+    LPDIRECT3DSURFACE9 render_target = nullptr;
+    LPDIRECT3DSURFACE9 last_render_target = nullptr;
+    LPDIRECT3DSURFACE9 last_depth_stencil = nullptr;
+    vd->SwapChain->GetBackBuffer(0, D3DBACKBUFFER_TYPE_MONO, &render_target);
+    bd->pd3dDevice->GetRenderTarget(0, &last_render_target);
+    bd->pd3dDevice->GetDepthStencilSurface(&last_depth_stencil);
+    bd->pd3dDevice->SetRenderTarget(0, render_target);
+    bd->pd3dDevice->SetDepthStencilSurface(nullptr);
+
+    if (!(viewport->Flags & ImGuiViewportFlags_NoRendererClear))
+    {
+        D3DCOLOR clear_col_dx = D3DCOLOR_RGBA((int)(clear_color.x*255.0f), (int)(clear_color.y*255.0f), (int)(clear_color.z*255.0f), (int)(clear_color.w*255.0f));
+        bd->pd3dDevice->Clear(0, nullptr, D3DCLEAR_TARGET, clear_col_dx, 1.0f, 0);
+    }
+
+    ImGui_ImplDX9_RenderDrawData(viewport->DrawData);
+
+    // Restore render target
+    bd->pd3dDevice->SetRenderTarget(0, last_render_target);
+    bd->pd3dDevice->SetDepthStencilSurface(last_depth_stencil);
+    render_target->Release();
+    last_render_target->Release();
+    if (last_depth_stencil) last_depth_stencil->Release();
+}
+
+static void ImGui_ImplDX9_SwapBuffers(ImGuiViewport* viewport, void*)
+{
+    ImGui_ImplDX9_ViewportData* vd = (ImGui_ImplDX9_ViewportData*)viewport->RendererUserData;
+    HRESULT hr = vd->SwapChain->Present(nullptr, nullptr, vd->d3dpp.hDeviceWindow, nullptr, 0);
+    // Let main application handle D3DERR_DEVICELOST by resetting the device.
+    IM_ASSERT(SUCCEEDED(hr) || hr == D3DERR_DEVICELOST);
+}
+
+static void ImGui_ImplDX9_InitPlatformInterface()
+{
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    platform_io.Renderer_CreateWindow = ImGui_ImplDX9_CreateWindow;
+    platform_io.Renderer_DestroyWindow = ImGui_ImplDX9_DestroyWindow;
+    platform_io.Renderer_SetWindowSize = ImGui_ImplDX9_SetWindowSize;
+    platform_io.Renderer_RenderWindow = ImGui_ImplDX9_RenderWindow;
+    platform_io.Renderer_SwapBuffers = ImGui_ImplDX9_SwapBuffers;
+}
+
+static void ImGui_ImplDX9_ShutdownPlatformInterface()
+{
+    ImGui::DestroyPlatformWindows();
+}
+
+static void ImGui_ImplDX9_CreateDeviceObjectsForPlatformWindows()
+{
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    for (int i = 1; i < platform_io.Viewports.Size; i++)
+        if (!platform_io.Viewports[i]->RendererUserData)
+            ImGui_ImplDX9_CreateWindow(platform_io.Viewports[i]);
+}
+
+static void ImGui_ImplDX9_InvalidateDeviceObjectsForPlatformWindows()
+{
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    for (int i = 1; i < platform_io.Viewports.Size; i++)
+        if (platform_io.Viewports[i]->RendererUserData)
+            ImGui_ImplDX9_DestroyWindow(platform_io.Viewports[i]);
+}
+
 //-----------------------------------------------------------------------------
 
 #endif // #ifndef IMGUI_DISABLE
diff --git a/backends/imgui_impl_dx9.h b/backends/imgui_impl_dx9.h
index 3965583..ecf7181 100644
--- a/backends/imgui_impl_dx9.h
+++ b/backends/imgui_impl_dx9.h
@@ -4,6 +4,7 @@
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'LPDIRECT3DTEXTURE9' as ImTextureID. Read the FAQ about ImTextureID!
 //  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.
+//  [X] Renderer: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
diff --git a/backends/imgui_impl_glfw.cpp b/backends/imgui_impl_glfw.cpp
index 8839178..23b0adb 100644
--- a/backends/imgui_impl_glfw.cpp
+++ b/backends/imgui_impl_glfw.cpp
@@ -9,6 +9,9 @@
 //  [X] Platform: Keyboard support. Since 1.87 we are using the io.AddKeyEvent() function. Pass ImGuiKey values to all key functions e.g. ImGui::IsKeyPressed(ImGuiKey_Space). [Legacy GLFW_KEY_* values will also be supported unless IMGUI_DISABLE_OBSOLETE_KEYIO is set]
 //  [X] Platform: Gamepad support. Enable with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
 //  [X] Platform: Mouse cursor shape and visibility. Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange' (note: the resizing cursors requires GLFW 3.4+).
+//  [X] Platform: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
+// Issues:
+//  [ ] Platform: Multi-viewport: ParentViewportID not honored, and so io.ConfigViewportsNoDefaultParent has no effect (minor).
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
@@ -20,6 +23,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2024-XX-XX: Platform: Added support for multiple windows via the ImGuiPlatformIO interface.
 //  2023-12-19: Emscripten: Added ImGui_ImplGlfw_InstallEmscriptenCanvasResizeCallback() to register canvas selector and auto-resize GLFW window.
 //  2023-10-05: Inputs: Added support for extra ImGuiKey values: F13 to F24 function keys.
 //  2023-07-18: Inputs: Revert ignoring mouse data on GLFW_CURSOR_DISABLED as it can be used differently. User may set ImGuiConfigFLags_NoMouse if desired. (#5625, #6609)
@@ -28,6 +32,7 @@
 //  2023-03-16: Inputs: Fixed key modifiers handling on secondary viewports (docking branch). Broken on 2023/01/04. (#6248, #6034)
 //  2023-03-14: Emscripten: Avoid using glfwGetError() and glfwGetGamepadState() which are not correctly implemented in Emscripten emulation. (#6240)
 //  2023-02-03: Emscripten: Registering custom low-level mouse wheel handler to get more accurate scrolling impulses on Emscripten. (#4019, #6096)
+//  2023-01-18: Handle unsupported glfwGetVideoMode() call on e.g. Emscripten.
 //  2023-01-04: Inputs: Fixed mods state on Linux when using Alt-GR text input (e.g. German keyboard layout), could lead to broken text input. Revert a 2022/01/17 change were we resumed using mods provided by GLFW, turns out they were faulty.
 //  2022-11-22: Perform a dummy glfwGetError() read to cancel missing names with glfwGetKeyName(). (#5908)
 //  2022-10-18: Perform a dummy glfwGetError() read to cancel missing mouse cursors errors. Using GLFW_VERSION_COMBINED directly. (#5785)
@@ -104,11 +109,29 @@
 
 // We gather version tests as define in order to easily see which features are version-dependent.
 #define GLFW_VERSION_COMBINED           (GLFW_VERSION_MAJOR * 1000 + GLFW_VERSION_MINOR * 100 + GLFW_VERSION_REVISION)
+#define GLFW_HAS_WINDOW_TOPMOST         (GLFW_VERSION_COMBINED >= 3200) // 3.2+ GLFW_FLOATING
+#define GLFW_HAS_WINDOW_HOVERED         (GLFW_VERSION_COMBINED >= 3300) // 3.3+ GLFW_HOVERED
+#define GLFW_HAS_WINDOW_ALPHA           (GLFW_VERSION_COMBINED >= 3300) // 3.3+ glfwSetWindowOpacity
+#define GLFW_HAS_PER_MONITOR_DPI        (GLFW_VERSION_COMBINED >= 3300) // 3.3+ glfwGetMonitorContentScale
+#if defined(__EMSCRIPTEN__) || defined(__SWITCH__)                      // no Vulkan support in GLFW for Emscripten or homebrew Nintendo Switch
+#define GLFW_HAS_VULKAN                 (0)
+#else
+#define GLFW_HAS_VULKAN                 (GLFW_VERSION_COMBINED >= 3200) // 3.2+ glfwCreateWindowSurface
+#endif
+#define GLFW_HAS_FOCUS_WINDOW           (GLFW_VERSION_COMBINED >= 3200) // 3.2+ glfwFocusWindow
+#define GLFW_HAS_FOCUS_ON_SHOW          (GLFW_VERSION_COMBINED >= 3300) // 3.3+ GLFW_FOCUS_ON_SHOW
+#define GLFW_HAS_MONITOR_WORK_AREA      (GLFW_VERSION_COMBINED >= 3300) // 3.3+ glfwGetMonitorWorkarea
+#define GLFW_HAS_OSX_WINDOW_POS_FIX     (GLFW_VERSION_COMBINED >= 3301) // 3.3.1+ Fixed: Resizing window repositions it on MacOS #1553
 #ifdef GLFW_RESIZE_NESW_CURSOR          // Let's be nice to people who pulled GLFW between 2019-04-16 (3.4 define) and 2019-11-29 (cursors defines) // FIXME: Remove when GLFW 3.4 is released?
 #define GLFW_HAS_NEW_CURSORS            (GLFW_VERSION_COMBINED >= 3400) // 3.4+ GLFW_RESIZE_ALL_CURSOR, GLFW_RESIZE_NESW_CURSOR, GLFW_RESIZE_NWSE_CURSOR, GLFW_NOT_ALLOWED_CURSOR
 #else
 #define GLFW_HAS_NEW_CURSORS            (0)
 #endif
+#ifdef GLFW_MOUSE_PASSTHROUGH           // Let's be nice to people who pulled GLFW between 2019-04-16 (3.4 define) and 2020-07-17 (passthrough)
+#define GLFW_HAS_MOUSE_PASSTHROUGH      (GLFW_VERSION_COMBINED >= 3400) // 3.4+ GLFW_MOUSE_PASSTHROUGH
+#else
+#define GLFW_HAS_MOUSE_PASSTHROUGH      (0)
+#endif
 #define GLFW_HAS_GAMEPAD_API            (GLFW_VERSION_COMBINED >= 3300) // 3.3+ glfwGetGamepadState() new api
 #define GLFW_HAS_GETKEYNAME             (GLFW_VERSION_COMBINED >= 3200) // 3.2+ glfwGetKeyName()
 #define GLFW_HAS_GETERROR               (GLFW_VERSION_COMBINED >= 3300) // 3.3+ glfwGetError()
@@ -129,8 +152,10 @@
     GLFWwindow*             MouseWindow;
     GLFWcursor*             MouseCursors[ImGuiMouseCursor_COUNT];
     ImVec2                  LastValidMousePos;
+    GLFWwindow*             KeyOwnerWindows[GLFW_KEY_LAST];
     bool                    InstalledCallbacks;
     bool                    CallbacksChainForAllWindows;
+    bool                    WantUpdateMonitors;
 #ifdef __EMSCRIPTEN__
     const char*             CanvasSelector;
 #endif
@@ -145,7 +170,7 @@
     GLFWcharfun             PrevUserCallbackChar;
     GLFWmonitorfun          PrevUserCallbackMonitor;
 #ifdef _WIN32
-    WNDPROC                 GlfwWndProc;
+    WNDPROC                 PrevWndProc;
 #endif
 
     ImGui_ImplGlfw_Data()   { memset((void*)this, 0, sizeof(*this)); }
@@ -163,6 +188,11 @@
     return ImGui::GetCurrentContext() ? (ImGui_ImplGlfw_Data*)ImGui::GetIO().BackendPlatformUserData : nullptr;
 }
 
+// Forward Declarations
+static void ImGui_ImplGlfw_UpdateMonitors();
+static void ImGui_ImplGlfw_InitPlatformInterface();
+static void ImGui_ImplGlfw_ShutdownPlatformInterface();
+
 // Functions
 static const char* ImGui_ImplGlfw_GetClipboardText(void* user_data)
 {
@@ -388,6 +418,9 @@
 
     ImGui_ImplGlfw_UpdateKeyModifiers(window);
 
+    if (keycode >= 0 && keycode < IM_ARRAYSIZE(bd->KeyOwnerWindows))
+        bd->KeyOwnerWindows[keycode] = (action == GLFW_PRESS) ? window : nullptr;
+
     keycode = ImGui_ImplGlfw_TranslateUntranslatedKey(keycode, scancode);
 
     ImGuiIO& io = ImGui::GetIO();
@@ -413,6 +446,13 @@
         bd->PrevUserCallbackCursorPos(window, x, y);
 
     ImGuiIO& io = ImGui::GetIO();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        int window_x, window_y;
+        glfwGetWindowPos(window, &window_x, &window_y);
+        x += window_x;
+        y += window_y;
+    }
     io.AddMousePosEvent((float)x, (float)y);
     bd->LastValidMousePos = ImVec2((float)x, (float)y);
 }
@@ -451,7 +491,8 @@
 
 void ImGui_ImplGlfw_MonitorCallback(GLFWmonitor*, int)
 {
-	// Unused in 'master' branch but 'docking' branch will use this, so we declare it ahead of it so if you have to install callbacks you can install this one too.
+    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
+    bd->WantUpdateMonitors = true;
 }
 
 #ifdef __EMSCRIPTEN__
@@ -473,32 +514,7 @@
 #endif
 
 #ifdef _WIN32
-// GLFW doesn't allow to distinguish Mouse vs TouchScreen vs Pen.
-// Add support for Win32 (based on imgui_impl_win32), because we rely on _TouchScreen info to trickle inputs differently.
-static ImGuiMouseSource GetMouseSourceFromMessageExtraInfo()
-{
-    LPARAM extra_info = ::GetMessageExtraInfo();
-    if ((extra_info & 0xFFFFFF80) == 0xFF515700)
-        return ImGuiMouseSource_Pen;
-    if ((extra_info & 0xFFFFFF80) == 0xFF515780)
-        return ImGuiMouseSource_TouchScreen;
-    return ImGuiMouseSource_Mouse;
-}
-static LRESULT CALLBACK ImGui_ImplGlfw_WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
-{
-    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
-    switch (msg)
-    {
-    case WM_MOUSEMOVE: case WM_NCMOUSEMOVE:
-    case WM_LBUTTONDOWN: case WM_LBUTTONDBLCLK: case WM_LBUTTONUP:
-    case WM_RBUTTONDOWN: case WM_RBUTTONDBLCLK: case WM_RBUTTONUP:
-    case WM_MBUTTONDOWN: case WM_MBUTTONDBLCLK: case WM_MBUTTONUP:
-    case WM_XBUTTONDOWN: case WM_XBUTTONDBLCLK: case WM_XBUTTONUP:
-        ImGui::GetIO().AddMouseSourceEvent(GetMouseSourceFromMessageExtraInfo());
-        break;
-    }
-    return ::CallWindowProcW(bd->GlfwWndProc, hWnd, msg, wParam, lParam);
-}
+static LRESULT CALLBACK ImGui_ImplGlfw_WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);
 #endif
 
 void ImGui_ImplGlfw_InstallCallbacks(GLFWwindow* window)
@@ -566,9 +582,16 @@
     io.BackendPlatformName = "imgui_impl_glfw";
     io.BackendFlags |= ImGuiBackendFlags_HasMouseCursors;         // We can honor GetMouseCursor() values (optional)
     io.BackendFlags |= ImGuiBackendFlags_HasSetMousePos;          // We can honor io.WantSetMousePos requests (optional, rarely used)
+#ifndef __EMSCRIPTEN__
+    io.BackendFlags |= ImGuiBackendFlags_PlatformHasViewports;    // We can create multi-viewports on the Platform side (optional)
+#endif
+#if GLFW_HAS_MOUSE_PASSTHROUGH || GLFW_HAS_WINDOW_HOVERED
+    io.BackendFlags |= ImGuiBackendFlags_HasMouseHoveredViewport; // We can call io.AddMouseViewportEvent() with correct data (optional)
+#endif
 
     bd->Window = window;
     bd->Time = 0.0;
+    bd->WantUpdateMonitors = true;
 
     io.SetClipboardTextFn = ImGui_ImplGlfw_SetClipboardText;
     io.GetClipboardTextFn = ImGui_ImplGlfw_GetClipboardText;
@@ -610,8 +633,13 @@
     emscripten_set_wheel_callback(EMSCRIPTEN_EVENT_TARGET_DOCUMENT, nullptr, false, ImGui_ImplEmscripten_WheelCallback);
 #endif
 
+    // Update monitors the first time (note: monitor callback are broken in GLFW 3.2 and earlier, see github.com/glfw/glfw/issues/784)
+    ImGui_ImplGlfw_UpdateMonitors();
+    glfwSetMonitorCallback(ImGui_ImplGlfw_MonitorCallback);
+
     // Set platform dependent data in viewport
     ImGuiViewport* main_viewport = ImGui::GetMainViewport();
+    main_viewport->PlatformHandle = (void*)bd->Window;
 #ifdef _WIN32
     main_viewport->PlatformHandleRaw = glfwGetWin32Window(bd->Window);
 #elif defined(__APPLE__)
@@ -619,11 +647,13 @@
 #else
     IM_UNUSED(main_viewport);
 #endif
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        ImGui_ImplGlfw_InitPlatformInterface();
 
     // Windows: register a WndProc hook so we can intercept some messages.
 #ifdef _WIN32
-    bd->GlfwWndProc = (WNDPROC)::GetWindowLongPtrW((HWND)main_viewport->PlatformHandleRaw, GWLP_WNDPROC);
-    IM_ASSERT(bd->GlfwWndProc != nullptr);
+    bd->PrevWndProc = (WNDPROC)::GetWindowLongPtrW((HWND)main_viewport->PlatformHandleRaw, GWLP_WNDPROC);
+    IM_ASSERT(bd->PrevWndProc != nullptr);
     ::SetWindowLongPtrW((HWND)main_viewport->PlatformHandleRaw, GWLP_WNDPROC, (LONG_PTR)ImGui_ImplGlfw_WndProc);
 #endif
 
@@ -652,6 +682,8 @@
     IM_ASSERT(bd != nullptr && "No platform backend to shutdown, or already shutdown?");
     ImGuiIO& io = ImGui::GetIO();
 
+    ImGui_ImplGlfw_ShutdownPlatformInterface();
+
     if (bd->InstalledCallbacks)
         ImGui_ImplGlfw_RestoreCallbacks(bd->Window);
 #ifdef __EMSCRIPTEN__
@@ -661,16 +693,16 @@
     for (ImGuiMouseCursor cursor_n = 0; cursor_n < ImGuiMouseCursor_COUNT; cursor_n++)
         glfwDestroyCursor(bd->MouseCursors[cursor_n]);
 
-    // Windows: register a WndProc hook so we can intercept some messages.
+    // Windows: restore our WndProc hook
 #ifdef _WIN32
     ImGuiViewport* main_viewport = ImGui::GetMainViewport();
-    ::SetWindowLongPtrW((HWND)main_viewport->PlatformHandleRaw, GWLP_WNDPROC, (LONG_PTR)bd->GlfwWndProc);
-    bd->GlfwWndProc = nullptr;
+    ::SetWindowLongPtrW((HWND)main_viewport->PlatformHandleRaw, GWLP_WNDPROC, (LONG_PTR)bd->PrevWndProc);
+    bd->PrevWndProc = nullptr;
 #endif
 
     io.BackendPlatformName = nullptr;
     io.BackendPlatformUserData = nullptr;
-    io.BackendFlags &= ~(ImGuiBackendFlags_HasMouseCursors | ImGuiBackendFlags_HasSetMousePos | ImGuiBackendFlags_HasGamepad);
+    io.BackendFlags &= ~(ImGuiBackendFlags_HasMouseCursors | ImGuiBackendFlags_HasSetMousePos | ImGuiBackendFlags_HasGamepad | ImGuiBackendFlags_PlatformHasViewports | ImGuiBackendFlags_HasMouseHoveredViewport);
     IM_DELETE(bd);
 }
 
@@ -678,10 +710,15 @@
 {
     ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
     ImGuiIO& io = ImGui::GetIO();
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
 
-    // (those braces are here to reduce diff with multi-viewports support in 'docking' branch)
+    ImGuiID mouse_viewport_id = 0;
+    const ImVec2 mouse_pos_prev = io.MousePos;
+    for (int n = 0; n < platform_io.Viewports.Size; n++)
     {
-        GLFWwindow* window = bd->Window;
+        ImGuiViewport* viewport = platform_io.Viewports[n];
+        GLFWwindow* window = (GLFWwindow*)viewport->PlatformHandle;
+
 #ifdef __EMSCRIPTEN__
         const bool is_window_focused = true;
 #else
@@ -690,19 +727,54 @@
         if (is_window_focused)
         {
             // (Optional) Set OS mouse position from Dear ImGui if requested (rarely used, only when ImGuiConfigFlags_NavEnableSetMousePos is enabled by user)
+            // When multi-viewports are enabled, all Dear ImGui positions are same as OS positions.
             if (io.WantSetMousePos)
-                glfwSetCursorPos(window, (double)io.MousePos.x, (double)io.MousePos.y);
+                glfwSetCursorPos(window, (double)(mouse_pos_prev.x - viewport->Pos.x), (double)(mouse_pos_prev.y - viewport->Pos.y));
 
             // (Optional) Fallback to provide mouse position when focused (ImGui_ImplGlfw_CursorPosCallback already provides this when hovered or captured)
             if (bd->MouseWindow == nullptr)
             {
                 double mouse_x, mouse_y;
                 glfwGetCursorPos(window, &mouse_x, &mouse_y);
+                if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+                {
+                    // Single viewport mode: mouse position in client window coordinates (io.MousePos is (0,0) when the mouse is on the upper-left corner of the app window)
+                    // Multi-viewport mode: mouse position in OS absolute coordinates (io.MousePos is (0,0) when the mouse is on the upper-left of the primary monitor)
+                    int window_x, window_y;
+                    glfwGetWindowPos(window, &window_x, &window_y);
+                    mouse_x += window_x;
+                    mouse_y += window_y;
+                }
                 bd->LastValidMousePos = ImVec2((float)mouse_x, (float)mouse_y);
                 io.AddMousePosEvent((float)mouse_x, (float)mouse_y);
             }
         }
+
+        // (Optional) When using multiple viewports: call io.AddMouseViewportEvent() with the viewport the OS mouse cursor is hovering.
+        // If ImGuiBackendFlags_HasMouseHoveredViewport is not set by the backend, Dear imGui will ignore this field and infer the information using its flawed heuristic.
+        // - [X] GLFW >= 3.3 backend ON WINDOWS ONLY does correctly ignore viewports with the _NoInputs flag (since we implement hit via our WndProc hook)
+        //       On other platforms we rely on the library fallbacking to its own search when reporting a viewport with _NoInputs flag.
+        // - [!] GLFW <= 3.2 backend CANNOT correctly ignore viewports with the _NoInputs flag, and CANNOT reported Hovered Viewport because of mouse capture.
+        //       Some backend are not able to handle that correctly. If a backend report an hovered viewport that has the _NoInputs flag (e.g. when dragging a window
+        //       for docking, the viewport has the _NoInputs flag in order to allow us to find the viewport under), then Dear ImGui is forced to ignore the value reported
+        //       by the backend, and use its flawed heuristic to guess the viewport behind.
+        // - [X] GLFW backend correctly reports this regardless of another viewport behind focused and dragged from (we need this to find a useful drag and drop target).
+        // FIXME: This is currently only correct on Win32. See what we do below with the WM_NCHITTEST, missing an equivalent for other systems.
+        // See https://github.com/glfw/glfw/issues/1236 if you want to help in making this a GLFW feature.
+#if GLFW_HAS_MOUSE_PASSTHROUGH
+        const bool window_no_input = (viewport->Flags & ImGuiViewportFlags_NoInputs) != 0;
+        glfwSetWindowAttrib(window, GLFW_MOUSE_PASSTHROUGH, window_no_input);
+#endif
+#if GLFW_HAS_MOUSE_PASSTHROUGH || GLFW_HAS_WINDOW_HOVERED
+        if (glfwGetWindowAttrib(window, GLFW_HOVERED))
+            mouse_viewport_id = viewport->ID;
+#else
+        // We cannot use bd->MouseWindow maintained from CursorEnter/Leave callbacks, because it is locked to the window capturing mouse.
+#endif
     }
+
+    if (io.BackendFlags & ImGuiBackendFlags_HasMouseHoveredViewport)
+        io.AddMouseViewportEvent(mouse_viewport_id);
 }
 
 static void ImGui_ImplGlfw_UpdateMouseCursor()
@@ -713,9 +785,10 @@
         return;
 
     ImGuiMouseCursor imgui_cursor = ImGui::GetMouseCursor();
-    // (those braces are here to reduce diff with multi-viewports support in 'docking' branch)
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    for (int n = 0; n < platform_io.Viewports.Size; n++)
     {
-        GLFWwindow* window = bd->Window;
+        GLFWwindow* window = (GLFWwindow*)platform_io.Viewports[n]->PlatformHandle;
         if (imgui_cursor == ImGuiMouseCursor_None || io.MouseDrawCursor)
         {
             // Hide OS mouse cursor if imgui is drawing it or if it wants no cursor
@@ -784,6 +857,48 @@
     #undef MAP_ANALOG
 }
 
+static void ImGui_ImplGlfw_UpdateMonitors()
+{
+    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    bd->WantUpdateMonitors = false;
+
+    int monitors_count = 0;
+    GLFWmonitor** glfw_monitors = glfwGetMonitors(&monitors_count);
+    if (monitors_count == 0) // Preserve existing monitor list if there are none. Happens on macOS sleeping (#5683)
+        return;
+
+    platform_io.Monitors.resize(0);
+    for (int n = 0; n < monitors_count; n++)
+    {
+        ImGuiPlatformMonitor monitor;
+        int x, y;
+        glfwGetMonitorPos(glfw_monitors[n], &x, &y);
+        const GLFWvidmode* vid_mode = glfwGetVideoMode(glfw_monitors[n]);
+        if (vid_mode == nullptr)
+            continue; // Failed to get Video mode (e.g. Emscripten does not support this function)
+        monitor.MainPos = monitor.WorkPos = ImVec2((float)x, (float)y);
+        monitor.MainSize = monitor.WorkSize = ImVec2((float)vid_mode->width, (float)vid_mode->height);
+#if GLFW_HAS_MONITOR_WORK_AREA
+        int w, h;
+        glfwGetMonitorWorkarea(glfw_monitors[n], &x, &y, &w, &h);
+        if (w > 0 && h > 0) // Workaround a small GLFW issue reporting zero on monitor changes: https://github.com/glfw/glfw/pull/1761
+        {
+            monitor.WorkPos = ImVec2((float)x, (float)y);
+            monitor.WorkSize = ImVec2((float)w, (float)h);
+        }
+#endif
+#if GLFW_HAS_PER_MONITOR_DPI
+        // Warning: the validity of monitor DPI information on Windows depends on the application DPI awareness settings, which generally needs to be set in the manifest or at runtime.
+        float x_scale, y_scale;
+        glfwGetMonitorContentScale(glfw_monitors[n], &x_scale, &y_scale);
+        monitor.DpiScale = x_scale;
+#endif
+        monitor.PlatformHandle = (void*)glfw_monitors[n]; // [...] GLFW doc states: "guaranteed to be valid only until the monitor configuration changes"
+        platform_io.Monitors.push_back(monitor);
+    }
+}
+
 void ImGui_ImplGlfw_NewFrame()
 {
     ImGuiIO& io = ImGui::GetIO();
@@ -798,6 +913,8 @@
     io.DisplaySize = ImVec2((float)w, (float)h);
     if (w > 0 && h > 0)
         io.DisplayFramebufferScale = ImVec2((float)display_w / (float)w, (float)display_h / (float)h);
+    if (bd->WantUpdateMonitors)
+        ImGui_ImplGlfw_UpdateMonitors();
 
     // Setup time step
     // (Accept glfwGetTime() not returning a monotonically increasing value. Seems to happens on disconnecting peripherals and probably on VMs and Emscripten, see #6491, #6189, #6114, #3644)
@@ -850,6 +967,399 @@
 }
 #endif
 
+
+//--------------------------------------------------------------------------------------------------------
+// MULTI-VIEWPORT / PLATFORM INTERFACE SUPPORT
+// This is an _advanced_ and _optional_ feature, allowing the backend to create and handle multiple viewports simultaneously.
+// If you are new to dear imgui or creating a new binding for dear imgui, it is recommended that you completely ignore this section first..
+//--------------------------------------------------------------------------------------------------------
+
+// Helper structure we store in the void* RendererUserData field of each ImGuiViewport to easily retrieve our backend data.
+struct ImGui_ImplGlfw_ViewportData
+{
+    GLFWwindow* Window;
+    bool        WindowOwned;
+    int         IgnoreWindowPosEventFrame;
+    int         IgnoreWindowSizeEventFrame;
+#ifdef _WIN32
+    WNDPROC     PrevWndProc;
+#endif
+
+    ImGui_ImplGlfw_ViewportData()  { memset(this, 0, sizeof(*this)); IgnoreWindowSizeEventFrame = IgnoreWindowPosEventFrame = -1; }
+    ~ImGui_ImplGlfw_ViewportData() { IM_ASSERT(Window == nullptr); }
+};
+
+static void ImGui_ImplGlfw_WindowCloseCallback(GLFWwindow* window)
+{
+    if (ImGuiViewport* viewport = ImGui::FindViewportByPlatformHandle(window))
+        viewport->PlatformRequestClose = true;
+}
+
+// GLFW may dispatch window pos/size events after calling glfwSetWindowPos()/glfwSetWindowSize().
+// However: depending on the platform the callback may be invoked at different time:
+// - on Windows it appears to be called within the glfwSetWindowPos()/glfwSetWindowSize() call
+// - on Linux it is queued and invoked during glfwPollEvents()
+// Because the event doesn't always fire on glfwSetWindowXXX() we use a frame counter tag to only
+// ignore recent glfwSetWindowXXX() calls.
+static void ImGui_ImplGlfw_WindowPosCallback(GLFWwindow* window, int, int)
+{
+    if (ImGuiViewport* viewport = ImGui::FindViewportByPlatformHandle(window))
+    {
+        if (ImGui_ImplGlfw_ViewportData* vd = (ImGui_ImplGlfw_ViewportData*)viewport->PlatformUserData)
+        {
+            bool ignore_event = (ImGui::GetFrameCount() <= vd->IgnoreWindowPosEventFrame + 1);
+            //data->IgnoreWindowPosEventFrame = -1;
+            if (ignore_event)
+                return;
+        }
+        viewport->PlatformRequestMove = true;
+    }
+}
+
+static void ImGui_ImplGlfw_WindowSizeCallback(GLFWwindow* window, int, int)
+{
+    if (ImGuiViewport* viewport = ImGui::FindViewportByPlatformHandle(window))
+    {
+        if (ImGui_ImplGlfw_ViewportData* vd = (ImGui_ImplGlfw_ViewportData*)viewport->PlatformUserData)
+        {
+            bool ignore_event = (ImGui::GetFrameCount() <= vd->IgnoreWindowSizeEventFrame + 1);
+            //data->IgnoreWindowSizeEventFrame = -1;
+            if (ignore_event)
+                return;
+        }
+        viewport->PlatformRequestResize = true;
+    }
+}
+
+static void ImGui_ImplGlfw_CreateWindow(ImGuiViewport* viewport)
+{
+    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
+    ImGui_ImplGlfw_ViewportData* vd = IM_NEW(ImGui_ImplGlfw_ViewportData)();
+    viewport->PlatformUserData = vd;
+
+    // GLFW 3.2 unfortunately always set focus on glfwCreateWindow() if GLFW_VISIBLE is set, regardless of GLFW_FOCUSED
+    // With GLFW 3.3, the hint GLFW_FOCUS_ON_SHOW fixes this problem
+    glfwWindowHint(GLFW_VISIBLE, false);
+    glfwWindowHint(GLFW_FOCUSED, false);
+#if GLFW_HAS_FOCUS_ON_SHOW
+    glfwWindowHint(GLFW_FOCUS_ON_SHOW, false);
+ #endif
+    glfwWindowHint(GLFW_DECORATED, (viewport->Flags & ImGuiViewportFlags_NoDecoration) ? false : true);
+#if GLFW_HAS_WINDOW_TOPMOST
+    glfwWindowHint(GLFW_FLOATING, (viewport->Flags & ImGuiViewportFlags_TopMost) ? true : false);
+#endif
+    GLFWwindow* share_window = (bd->ClientApi == GlfwClientApi_OpenGL) ? bd->Window : nullptr;
+    vd->Window = glfwCreateWindow((int)viewport->Size.x, (int)viewport->Size.y, "No Title Yet", nullptr, share_window);
+    vd->WindowOwned = true;
+    viewport->PlatformHandle = (void*)vd->Window;
+#ifdef _WIN32
+    viewport->PlatformHandleRaw = glfwGetWin32Window(vd->Window);
+#elif defined(__APPLE__)
+    viewport->PlatformHandleRaw = (void*)glfwGetCocoaWindow(vd->Window);
+#endif
+    glfwSetWindowPos(vd->Window, (int)viewport->Pos.x, (int)viewport->Pos.y);
+
+    // Install GLFW callbacks for secondary viewports
+    glfwSetWindowFocusCallback(vd->Window, ImGui_ImplGlfw_WindowFocusCallback);
+    glfwSetCursorEnterCallback(vd->Window, ImGui_ImplGlfw_CursorEnterCallback);
+    glfwSetCursorPosCallback(vd->Window, ImGui_ImplGlfw_CursorPosCallback);
+    glfwSetMouseButtonCallback(vd->Window, ImGui_ImplGlfw_MouseButtonCallback);
+    glfwSetScrollCallback(vd->Window, ImGui_ImplGlfw_ScrollCallback);
+    glfwSetKeyCallback(vd->Window, ImGui_ImplGlfw_KeyCallback);
+    glfwSetCharCallback(vd->Window, ImGui_ImplGlfw_CharCallback);
+    glfwSetWindowCloseCallback(vd->Window, ImGui_ImplGlfw_WindowCloseCallback);
+    glfwSetWindowPosCallback(vd->Window, ImGui_ImplGlfw_WindowPosCallback);
+    glfwSetWindowSizeCallback(vd->Window, ImGui_ImplGlfw_WindowSizeCallback);
+    if (bd->ClientApi == GlfwClientApi_OpenGL)
+    {
+        glfwMakeContextCurrent(vd->Window);
+        glfwSwapInterval(0);
+    }
+}
+
+static void ImGui_ImplGlfw_DestroyWindow(ImGuiViewport* viewport)
+{
+    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
+    if (ImGui_ImplGlfw_ViewportData* vd = (ImGui_ImplGlfw_ViewportData*)viewport->PlatformUserData)
+    {
+        if (vd->WindowOwned)
+        {
+#if !GLFW_HAS_MOUSE_PASSTHROUGH && GLFW_HAS_WINDOW_HOVERED && defined(_WIN32)
+            HWND hwnd = (HWND)viewport->PlatformHandleRaw;
+            ::RemovePropA(hwnd, "IMGUI_VIEWPORT");
+#endif
+
+            // Release any keys that were pressed in the window being destroyed and are still held down,
+            // because we will not receive any release events after window is destroyed.
+            for (int i = 0; i < IM_ARRAYSIZE(bd->KeyOwnerWindows); i++)
+                if (bd->KeyOwnerWindows[i] == vd->Window)
+                    ImGui_ImplGlfw_KeyCallback(vd->Window, i, 0, GLFW_RELEASE, 0); // Later params are only used for main viewport, on which this function is never called.
+
+            glfwDestroyWindow(vd->Window);
+        }
+        vd->Window = nullptr;
+        IM_DELETE(vd);
+    }
+    viewport->PlatformUserData = viewport->PlatformHandle = nullptr;
+}
+
+static void ImGui_ImplGlfw_ShowWindow(ImGuiViewport* viewport)
+{
+    ImGui_ImplGlfw_ViewportData* vd = (ImGui_ImplGlfw_ViewportData*)viewport->PlatformUserData;
+
+#if defined(_WIN32)
+    // GLFW hack: Hide icon from task bar
+    HWND hwnd = (HWND)viewport->PlatformHandleRaw;
+    if (viewport->Flags & ImGuiViewportFlags_NoTaskBarIcon)
+    {
+        LONG ex_style = ::GetWindowLong(hwnd, GWL_EXSTYLE);
+        ex_style &= ~WS_EX_APPWINDOW;
+        ex_style |= WS_EX_TOOLWINDOW;
+        ::SetWindowLong(hwnd, GWL_EXSTYLE, ex_style);
+    }
+
+    // GLFW hack: install hook for WM_NCHITTEST message handler
+#if !GLFW_HAS_MOUSE_PASSTHROUGH && GLFW_HAS_WINDOW_HOVERED && defined(_WIN32)
+    ::SetPropA(hwnd, "IMGUI_VIEWPORT", viewport);
+    vd->PrevWndProc = (WNDPROC)::GetWindowLongPtrW(hwnd, GWLP_WNDPROC);
+    ::SetWindowLongPtrW(hwnd, GWLP_WNDPROC, (LONG_PTR)ImGui_ImplGlfw_WndProc);
+#endif
+
+#if !GLFW_HAS_FOCUS_ON_SHOW
+    // GLFW hack: GLFW 3.2 has a bug where glfwShowWindow() also activates/focus the window.
+    // The fix was pushed to GLFW repository on 2018/01/09 and should be included in GLFW 3.3 via a GLFW_FOCUS_ON_SHOW window attribute.
+    // See https://github.com/glfw/glfw/issues/1189
+    // FIXME-VIEWPORT: Implement same work-around for Linux/OSX in the meanwhile.
+    if (viewport->Flags & ImGuiViewportFlags_NoFocusOnAppearing)
+    {
+        ::ShowWindow(hwnd, SW_SHOWNA);
+        return;
+    }
+#endif
+#endif
+
+    glfwShowWindow(vd->Window);
+}
+
+static ImVec2 ImGui_ImplGlfw_GetWindowPos(ImGuiViewport* viewport)
+{
+    ImGui_ImplGlfw_ViewportData* vd = (ImGui_ImplGlfw_ViewportData*)viewport->PlatformUserData;
+    int x = 0, y = 0;
+    glfwGetWindowPos(vd->Window, &x, &y);
+    return ImVec2((float)x, (float)y);
+}
+
+static void ImGui_ImplGlfw_SetWindowPos(ImGuiViewport* viewport, ImVec2 pos)
+{
+    ImGui_ImplGlfw_ViewportData* vd = (ImGui_ImplGlfw_ViewportData*)viewport->PlatformUserData;
+    vd->IgnoreWindowPosEventFrame = ImGui::GetFrameCount();
+    glfwSetWindowPos(vd->Window, (int)pos.x, (int)pos.y);
+}
+
+static ImVec2 ImGui_ImplGlfw_GetWindowSize(ImGuiViewport* viewport)
+{
+    ImGui_ImplGlfw_ViewportData* vd = (ImGui_ImplGlfw_ViewportData*)viewport->PlatformUserData;
+    int w = 0, h = 0;
+    glfwGetWindowSize(vd->Window, &w, &h);
+    return ImVec2((float)w, (float)h);
+}
+
+static void ImGui_ImplGlfw_SetWindowSize(ImGuiViewport* viewport, ImVec2 size)
+{
+    ImGui_ImplGlfw_ViewportData* vd = (ImGui_ImplGlfw_ViewportData*)viewport->PlatformUserData;
+#if __APPLE__ && !GLFW_HAS_OSX_WINDOW_POS_FIX
+    // Native OS windows are positioned from the bottom-left corner on macOS, whereas on other platforms they are
+    // positioned from the upper-left corner. GLFW makes an effort to convert macOS style coordinates, however it
+    // doesn't handle it when changing size. We are manually moving the window in order for changes of size to be based
+    // on the upper-left corner.
+    int x, y, width, height;
+    glfwGetWindowPos(vd->Window, &x, &y);
+    glfwGetWindowSize(vd->Window, &width, &height);
+    glfwSetWindowPos(vd->Window, x, y - height + size.y);
+#endif
+    vd->IgnoreWindowSizeEventFrame = ImGui::GetFrameCount();
+    glfwSetWindowSize(vd->Window, (int)size.x, (int)size.y);
+}
+
+static void ImGui_ImplGlfw_SetWindowTitle(ImGuiViewport* viewport, const char* title)
+{
+    ImGui_ImplGlfw_ViewportData* vd = (ImGui_ImplGlfw_ViewportData*)viewport->PlatformUserData;
+    glfwSetWindowTitle(vd->Window, title);
+}
+
+static void ImGui_ImplGlfw_SetWindowFocus(ImGuiViewport* viewport)
+{
+#if GLFW_HAS_FOCUS_WINDOW
+    ImGui_ImplGlfw_ViewportData* vd = (ImGui_ImplGlfw_ViewportData*)viewport->PlatformUserData;
+    glfwFocusWindow(vd->Window);
+#else
+    // FIXME: What are the effect of not having this function? At the moment imgui doesn't actually call SetWindowFocus - we set that up ahead, will answer that question later.
+    (void)viewport;
+#endif
+}
+
+static bool ImGui_ImplGlfw_GetWindowFocus(ImGuiViewport* viewport)
+{
+    ImGui_ImplGlfw_ViewportData* vd = (ImGui_ImplGlfw_ViewportData*)viewport->PlatformUserData;
+    return glfwGetWindowAttrib(vd->Window, GLFW_FOCUSED) != 0;
+}
+
+static bool ImGui_ImplGlfw_GetWindowMinimized(ImGuiViewport* viewport)
+{
+    ImGui_ImplGlfw_ViewportData* vd = (ImGui_ImplGlfw_ViewportData*)viewport->PlatformUserData;
+    return glfwGetWindowAttrib(vd->Window, GLFW_ICONIFIED) != 0;
+}
+
+#if GLFW_HAS_WINDOW_ALPHA
+static void ImGui_ImplGlfw_SetWindowAlpha(ImGuiViewport* viewport, float alpha)
+{
+    ImGui_ImplGlfw_ViewportData* vd = (ImGui_ImplGlfw_ViewportData*)viewport->PlatformUserData;
+    glfwSetWindowOpacity(vd->Window, alpha);
+}
+#endif
+
+static void ImGui_ImplGlfw_RenderWindow(ImGuiViewport* viewport, void*)
+{
+    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
+    ImGui_ImplGlfw_ViewportData* vd = (ImGui_ImplGlfw_ViewportData*)viewport->PlatformUserData;
+    if (bd->ClientApi == GlfwClientApi_OpenGL)
+        glfwMakeContextCurrent(vd->Window);
+}
+
+static void ImGui_ImplGlfw_SwapBuffers(ImGuiViewport* viewport, void*)
+{
+    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
+    ImGui_ImplGlfw_ViewportData* vd = (ImGui_ImplGlfw_ViewportData*)viewport->PlatformUserData;
+    if (bd->ClientApi == GlfwClientApi_OpenGL)
+    {
+        glfwMakeContextCurrent(vd->Window);
+        glfwSwapBuffers(vd->Window);
+    }
+}
+
+//--------------------------------------------------------------------------------------------------------
+// Vulkan support (the Vulkan renderer needs to call a platform-side support function to create the surface)
+//--------------------------------------------------------------------------------------------------------
+
+// Avoid including <vulkan.h> so we can build without it
+#if GLFW_HAS_VULKAN
+#ifndef VULKAN_H_
+#define VK_DEFINE_HANDLE(object) typedef struct object##_T* object;
+#if defined(__LP64__) || defined(_WIN64) || defined(__x86_64__) || defined(_M_X64) || defined(__ia64) || defined (_M_IA64) || defined(__aarch64__) || defined(__powerpc64__)
+#define VK_DEFINE_NON_DISPATCHABLE_HANDLE(object) typedef struct object##_T *object;
+#else
+#define VK_DEFINE_NON_DISPATCHABLE_HANDLE(object) typedef uint64_t object;
+#endif
+VK_DEFINE_HANDLE(VkInstance)
+VK_DEFINE_NON_DISPATCHABLE_HANDLE(VkSurfaceKHR)
+struct VkAllocationCallbacks;
+enum VkResult { VK_RESULT_MAX_ENUM = 0x7FFFFFFF };
+#endif // VULKAN_H_
+extern "C" { extern GLFWAPI VkResult glfwCreateWindowSurface(VkInstance instance, GLFWwindow* window, const VkAllocationCallbacks* allocator, VkSurfaceKHR* surface); }
+static int ImGui_ImplGlfw_CreateVkSurface(ImGuiViewport* viewport, ImU64 vk_instance, const void* vk_allocator, ImU64* out_vk_surface)
+{
+    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
+    ImGui_ImplGlfw_ViewportData* vd = (ImGui_ImplGlfw_ViewportData*)viewport->PlatformUserData;
+    IM_UNUSED(bd);
+    IM_ASSERT(bd->ClientApi == GlfwClientApi_Vulkan);
+    VkResult err = glfwCreateWindowSurface((VkInstance)vk_instance, vd->Window, (const VkAllocationCallbacks*)vk_allocator, (VkSurfaceKHR*)out_vk_surface);
+    return (int)err;
+}
+#endif // GLFW_HAS_VULKAN
+
+static void ImGui_ImplGlfw_InitPlatformInterface()
+{
+    // Register platform interface (will be coupled with a renderer interface)
+    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    platform_io.Platform_CreateWindow = ImGui_ImplGlfw_CreateWindow;
+    platform_io.Platform_DestroyWindow = ImGui_ImplGlfw_DestroyWindow;
+    platform_io.Platform_ShowWindow = ImGui_ImplGlfw_ShowWindow;
+    platform_io.Platform_SetWindowPos = ImGui_ImplGlfw_SetWindowPos;
+    platform_io.Platform_GetWindowPos = ImGui_ImplGlfw_GetWindowPos;
+    platform_io.Platform_SetWindowSize = ImGui_ImplGlfw_SetWindowSize;
+    platform_io.Platform_GetWindowSize = ImGui_ImplGlfw_GetWindowSize;
+    platform_io.Platform_SetWindowFocus = ImGui_ImplGlfw_SetWindowFocus;
+    platform_io.Platform_GetWindowFocus = ImGui_ImplGlfw_GetWindowFocus;
+    platform_io.Platform_GetWindowMinimized = ImGui_ImplGlfw_GetWindowMinimized;
+    platform_io.Platform_SetWindowTitle = ImGui_ImplGlfw_SetWindowTitle;
+    platform_io.Platform_RenderWindow = ImGui_ImplGlfw_RenderWindow;
+    platform_io.Platform_SwapBuffers = ImGui_ImplGlfw_SwapBuffers;
+#if GLFW_HAS_WINDOW_ALPHA
+    platform_io.Platform_SetWindowAlpha = ImGui_ImplGlfw_SetWindowAlpha;
+#endif
+#if GLFW_HAS_VULKAN
+    platform_io.Platform_CreateVkSurface = ImGui_ImplGlfw_CreateVkSurface;
+#endif
+
+    // Register main window handle (which is owned by the main application, not by us)
+    // This is mostly for simplicity and consistency, so that our code (e.g. mouse handling etc.) can use same logic for main and secondary viewports.
+    ImGuiViewport* main_viewport = ImGui::GetMainViewport();
+    ImGui_ImplGlfw_ViewportData* vd = IM_NEW(ImGui_ImplGlfw_ViewportData)();
+    vd->Window = bd->Window;
+    vd->WindowOwned = false;
+    main_viewport->PlatformUserData = vd;
+    main_viewport->PlatformHandle = (void*)bd->Window;
+}
+
+static void ImGui_ImplGlfw_ShutdownPlatformInterface()
+{
+    ImGui::DestroyPlatformWindows();
+}
+
+//-----------------------------------------------------------------------------
+
+// WndProc hook (declared here because we will need access to ImGui_ImplGlfw_ViewportData)
+#ifdef _WIN32
+static ImGuiMouseSource GetMouseSourceFromMessageExtraInfo()
+{
+    LPARAM extra_info = ::GetMessageExtraInfo();
+    if ((extra_info & 0xFFFFFF80) == 0xFF515700)
+        return ImGuiMouseSource_Pen;
+    if ((extra_info & 0xFFFFFF80) == 0xFF515780)
+        return ImGuiMouseSource_TouchScreen;
+    return ImGuiMouseSource_Mouse;
+}
+static LRESULT CALLBACK ImGui_ImplGlfw_WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
+{
+    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
+    WNDPROC prev_wndproc = bd->PrevWndProc;
+    ImGuiViewport* viewport = (ImGuiViewport*)::GetPropA(hWnd, "IMGUI_VIEWPORT");
+    if (viewport != NULL)
+        if (ImGui_ImplGlfw_ViewportData* vd = (ImGui_ImplGlfw_ViewportData*)viewport->PlatformUserData)
+            prev_wndproc = vd->PrevWndProc;
+
+    switch (msg)
+    {
+        // GLFW doesn't allow to distinguish Mouse vs TouchScreen vs Pen.
+        // Add support for Win32 (based on imgui_impl_win32), because we rely on _TouchScreen info to trickle inputs differently.
+    case WM_MOUSEMOVE: case WM_NCMOUSEMOVE:
+    case WM_LBUTTONDOWN: case WM_LBUTTONDBLCLK: case WM_LBUTTONUP:
+    case WM_RBUTTONDOWN: case WM_RBUTTONDBLCLK: case WM_RBUTTONUP:
+    case WM_MBUTTONDOWN: case WM_MBUTTONDBLCLK: case WM_MBUTTONUP:
+    case WM_XBUTTONDOWN: case WM_XBUTTONDBLCLK: case WM_XBUTTONUP:
+        ImGui::GetIO().AddMouseSourceEvent(GetMouseSourceFromMessageExtraInfo());
+        break;
+
+        // We have submitted https://github.com/glfw/glfw/pull/1568 to allow GLFW to support "transparent inputs".
+        // In the meanwhile we implement custom per-platform workarounds here (FIXME-VIEWPORT: Implement same work-around for Linux/OSX!)
+#if !GLFW_HAS_MOUSE_PASSTHROUGH && GLFW_HAS_WINDOW_HOVERED
+    case WM_NCHITTEST:
+    {
+        // Let mouse pass-through the window. This will allow the backend to call io.AddMouseViewportEvent() properly (which is OPTIONAL).
+        // The ImGuiViewportFlags_NoInputs flag is set while dragging a viewport, as want to detect the window behind the one we are dragging.
+        // If you cannot easily access those viewport flags from your windowing/event code: you may manually synchronize its state e.g. in
+        // your main loop after calling UpdatePlatformWindows(). Iterate all viewports/platform windows and pass the flag to your windowing system.
+        if (viewport && (viewport->Flags & ImGuiViewportFlags_NoInputs))
+            return HTTRANSPARENT;
+        break;
+    }
+#endif
+    }
+    return ::CallWindowProcW(prev_wndproc, hWnd, msg, wParam, lParam);
+}
+#endif // #ifdef _WIN32
+
 //-----------------------------------------------------------------------------
 
 #if defined(__clang__)
diff --git a/backends/imgui_impl_glfw.h b/backends/imgui_impl_glfw.h
index 6a9acd0..6fe6882 100644
--- a/backends/imgui_impl_glfw.h
+++ b/backends/imgui_impl_glfw.h
@@ -1,6 +1,7 @@
 // dear imgui: Platform Backend for GLFW
 // This needs to be used along with a Renderer (e.g. OpenGL3, Vulkan, WebGPU..)
 // (Info: GLFW is a cross-platform general purpose library for handling windows, inputs, OpenGL/Vulkan graphics context creation, etc.)
+// (Requires: GLFW 3.1+. Prefer GLFW 3.3+ for full feature support.)
 
 // Implemented features:
 //  [X] Platform: Clipboard support.
@@ -8,6 +9,9 @@
 //  [X] Platform: Keyboard support. Since 1.87 we are using the io.AddKeyEvent() function. Pass ImGuiKey values to all key functions e.g. ImGui::IsKeyPressed(ImGuiKey_Space). [Legacy GLFW_KEY_* values will also be supported unless IMGUI_DISABLE_OBSOLETE_KEYIO is set]
 //  [X] Platform: Gamepad support. Enable with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
 //  [X] Platform: Mouse cursor shape and visibility. Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange' (note: the resizing cursors requires GLFW 3.4+).
+//  [X] Platform: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
+// Issues:
+//  [ ] Platform: Multi-viewport: ParentViewportID not honored, and so io.ConfigViewportsNoDefaultParent has no effect (minor).
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
diff --git a/backends/imgui_impl_glut.cpp b/backends/imgui_impl_glut.cpp
index d8ffc90..0678603 100644
--- a/backends/imgui_impl_glut.cpp
+++ b/backends/imgui_impl_glut.cpp
@@ -7,7 +7,7 @@
 
 // Implemented features:
 //  [X] Platform: Partial keyboard support. Since 1.87 we are using the io.AddKeyEvent() function. Pass ImGuiKey values to all key functions e.g. ImGui::IsKeyPressed(ImGuiKey_Space). [Legacy GLUT values will also be supported unless IMGUI_DISABLE_OBSOLETE_KEYIO is set]
-// Issues:
+// Missing features:
 //  [ ] Platform: GLUT is unable to distinguish e.g. Backspace from CTRL+H or TAB from CTRL+I
 //  [ ] Platform: Missing horizontal mouse wheel support.
 //  [ ] Platform: Missing mouse cursor shape/visibility support.
diff --git a/backends/imgui_impl_glut.h b/backends/imgui_impl_glut.h
index 062110e..0067192 100644
--- a/backends/imgui_impl_glut.h
+++ b/backends/imgui_impl_glut.h
@@ -7,7 +7,7 @@
 
 // Implemented features:
 //  [X] Platform: Partial keyboard support. Since 1.87 we are using the io.AddKeyEvent() function. Pass ImGuiKey values to all key functions e.g. ImGui::IsKeyPressed(ImGuiKey_Space). [Legacy GLUT values will also be supported unless IMGUI_DISABLE_OBSOLETE_KEYIO is set]
-// Issues:
+// Missing features:
 //  [ ] Platform: GLUT is unable to distinguish e.g. Backspace from CTRL+H or TAB from CTRL+I
 //  [ ] Platform: Missing horizontal mouse wheel support.
 //  [ ] Platform: Missing mouse cursor shape/visibility support.
diff --git a/backends/imgui_impl_metal.h b/backends/imgui_impl_metal.h
index 53706d1..d9540fb 100644
--- a/backends/imgui_impl_metal.h
+++ b/backends/imgui_impl_metal.h
@@ -4,6 +4,7 @@
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'MTLTexture' as ImTextureID. Read the FAQ about ImTextureID!
 //  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.
+//  [X] Renderer: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
diff --git a/backends/imgui_impl_metal.mm b/backends/imgui_impl_metal.mm
index f9fd108..22aa37e 100644
--- a/backends/imgui_impl_metal.mm
+++ b/backends/imgui_impl_metal.mm
@@ -4,6 +4,7 @@
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'MTLTexture' as ImTextureID. Read the FAQ about ImTextureID!
 //  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.
+//  [X] Renderer: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
@@ -15,6 +16,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2024-XX-XX: Metal: Added support for multiple windows via the ImGuiPlatformIO interface.
 //  2022-08-23: Metal: Update deprecated property 'sampleCount'->'rasterSampleCount'.
 //  2022-07-05: Metal: Add dispatch synchronization.
 //  2022-06-30: Metal: Use __bridge for ARC based systems.
@@ -38,6 +40,12 @@
 #import <time.h>
 #import <Metal/Metal.h>
 
+// Forward Declarations
+static void ImGui_ImplMetal_InitPlatformInterface();
+static void ImGui_ImplMetal_ShutdownPlatformInterface();
+static void ImGui_ImplMetal_CreateDeviceObjectsForPlatformWindows();
+static void ImGui_ImplMetal_InvalidateDeviceObjectsForPlatformWindows();
+
 #pragma mark - Support classes
 
 // A wrapper around a MTLBuffer object that knows the last time it was reused
@@ -132,10 +140,14 @@
     io.BackendRendererUserData = (void*)bd;
     io.BackendRendererName = "imgui_impl_metal";
     io.BackendFlags |= ImGuiBackendFlags_RendererHasVtxOffset;  // We can honor the ImDrawCmd::VtxOffset field, allowing for large meshes.
+    io.BackendFlags |= ImGuiBackendFlags_RendererHasViewports;  // We can create multi-viewports on the Renderer side (optional)
 
     bd->SharedMetalContext = [[MetalContext alloc] init];
     bd->SharedMetalContext.device = device;
 
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        ImGui_ImplMetal_InitPlatformInterface();
+
     return true;
 }
 
@@ -143,13 +155,14 @@
 {
     ImGui_ImplMetal_Data* bd = ImGui_ImplMetal_GetBackendData();
     IM_ASSERT(bd != nullptr && "No renderer backend to shutdown, or already shutdown?");
+    ImGui_ImplMetal_ShutdownPlatformInterface();
     ImGui_ImplMetal_DestroyDeviceObjects();
     ImGui_ImplMetal_DestroyBackendData();
 
     ImGuiIO& io = ImGui::GetIO();
     io.BackendRendererName = nullptr;
     io.BackendRendererUserData = nullptr;
-    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;
+    io.BackendFlags &= ~(ImGuiBackendFlags_RendererHasVtxOffset | ImGuiBackendFlags_RendererHasViewports);
 }
 
 void ImGui_ImplMetal_NewFrame(MTLRenderPassDescriptor* renderPassDescriptor)
@@ -367,6 +380,7 @@
     depthStencilDescriptor.depthWriteEnabled = NO;
     depthStencilDescriptor.depthCompareFunction = MTLCompareFunctionAlways;
     bd->SharedMetalContext.depthStencilState = [device newDepthStencilStateWithDescriptor:depthStencilDescriptor];
+    ImGui_ImplMetal_CreateDeviceObjectsForPlatformWindows();
     ImGui_ImplMetal_CreateFontsTexture(device);
 
     return true;
@@ -376,9 +390,155 @@
 {
     ImGui_ImplMetal_Data* bd = ImGui_ImplMetal_GetBackendData();
     ImGui_ImplMetal_DestroyFontsTexture();
+    ImGui_ImplMetal_InvalidateDeviceObjectsForPlatformWindows();
     [bd->SharedMetalContext.renderPipelineStateCache removeAllObjects];
 }
 
+#pragma mark - Multi-viewport support
+
+#import <QuartzCore/CAMetalLayer.h>
+
+#if TARGET_OS_OSX
+#import <Cocoa/Cocoa.h>
+#endif
+
+//--------------------------------------------------------------------------------------------------------
+// MULTI-VIEWPORT / PLATFORM INTERFACE SUPPORT
+// This is an _advanced_ and _optional_ feature, allowing the back-end to create and handle multiple viewports simultaneously.
+// If you are new to dear imgui or creating a new binding for dear imgui, it is recommended that you completely ignore this section first..
+//--------------------------------------------------------------------------------------------------------
+
+struct ImGuiViewportDataMetal
+{
+    CAMetalLayer*               MetalLayer;
+    id<MTLCommandQueue>         CommandQueue;
+    MTLRenderPassDescriptor*    RenderPassDescriptor;
+    void*                       Handle = nullptr;
+    bool                        FirstFrame = true;
+};
+
+static void ImGui_ImplMetal_CreateWindow(ImGuiViewport* viewport)
+{
+    ImGui_ImplMetal_Data* bd = ImGui_ImplMetal_GetBackendData();
+    ImGuiViewportDataMetal* data = IM_NEW(ImGuiViewportDataMetal)();
+    viewport->RendererUserData = data;
+
+    // PlatformHandleRaw should always be a NSWindow*, whereas PlatformHandle might be a higher-level handle (e.g. GLFWWindow*, SDL_Window*).
+    // Some back-ends will leave PlatformHandleRaw == 0, in which case we assume PlatformHandle will contain the NSWindow*.
+    void* handle = viewport->PlatformHandleRaw ? viewport->PlatformHandleRaw : viewport->PlatformHandle;
+    IM_ASSERT(handle != nullptr);
+
+    id<MTLDevice> device = bd->SharedMetalContext.device;
+    CAMetalLayer* layer = [CAMetalLayer layer];
+    layer.device = device;
+    layer.framebufferOnly = YES;
+    layer.pixelFormat = bd->SharedMetalContext.framebufferDescriptor.colorPixelFormat;
+#if TARGET_OS_OSX
+    NSWindow* window = (__bridge NSWindow*)handle;
+    NSView* view = window.contentView;
+    view.layer = layer;
+    view.wantsLayer = YES;
+#endif
+    data->MetalLayer = layer;
+    data->CommandQueue = [device newCommandQueue];
+    data->RenderPassDescriptor = [[MTLRenderPassDescriptor alloc] init];
+    data->Handle = handle;
+}
+
+static void ImGui_ImplMetal_DestroyWindow(ImGuiViewport* viewport)
+{
+    // The main viewport (owned by the application) will always have RendererUserData == 0 since we didn't create the data for it.
+    if (ImGuiViewportDataMetal* data = (ImGuiViewportDataMetal*)viewport->RendererUserData)
+        IM_DELETE(data);
+    viewport->RendererUserData = nullptr;
+}
+
+inline static CGSize MakeScaledSize(CGSize size, CGFloat scale)
+{
+    return CGSizeMake(size.width * scale, size.height * scale);
+}
+
+static void ImGui_ImplMetal_SetWindowSize(ImGuiViewport* viewport, ImVec2 size)
+{
+    ImGuiViewportDataMetal* data = (ImGuiViewportDataMetal*)viewport->RendererUserData;
+    data->MetalLayer.drawableSize = MakeScaledSize(CGSizeMake(size.x, size.y), viewport->DpiScale);
+}
+
+static void ImGui_ImplMetal_RenderWindow(ImGuiViewport* viewport, void*)
+{
+    ImGuiViewportDataMetal* data = (ImGuiViewportDataMetal*)viewport->RendererUserData;
+
+#if TARGET_OS_OSX
+    void* handle = viewport->PlatformHandleRaw ? viewport->PlatformHandleRaw : viewport->PlatformHandle;
+    NSWindow* window = (__bridge NSWindow*)handle;
+
+    // Always render the first frame, regardless of occlusionState, to avoid an initial flicker
+    if ((window.occlusionState & NSWindowOcclusionStateVisible) == 0 && !data->FirstFrame)
+    {
+        // Do not render windows which are completely occluded. Calling -[CAMetalLayer nextDrawable] will hang for
+        // approximately 1 second if the Metal layer is completely occluded.
+        return;
+    }
+    data->FirstFrame = false;
+
+    viewport->DpiScale = (float)window.backingScaleFactor;
+    if (data->MetalLayer.contentsScale != viewport->DpiScale)
+    {
+        data->MetalLayer.contentsScale = viewport->DpiScale;
+        data->MetalLayer.drawableSize = MakeScaledSize(window.frame.size, viewport->DpiScale);
+    }
+    viewport->DrawData->FramebufferScale = ImVec2(viewport->DpiScale, viewport->DpiScale);
+#endif
+
+    id <CAMetalDrawable> drawable = [data->MetalLayer nextDrawable];
+    if (drawable == nil)
+        return;
+
+    MTLRenderPassDescriptor* renderPassDescriptor = data->RenderPassDescriptor;
+    renderPassDescriptor.colorAttachments[0].texture = drawable.texture;
+    renderPassDescriptor.colorAttachments[0].clearColor = MTLClearColorMake(0, 0, 0, 0);
+    if ((viewport->Flags & ImGuiViewportFlags_NoRendererClear) == 0)
+        renderPassDescriptor.colorAttachments[0].loadAction = MTLLoadActionClear;
+
+    id <MTLCommandBuffer> commandBuffer = [data->CommandQueue commandBuffer];
+    id <MTLRenderCommandEncoder> renderEncoder = [commandBuffer renderCommandEncoderWithDescriptor:renderPassDescriptor];
+    ImGui_ImplMetal_RenderDrawData(viewport->DrawData, commandBuffer, renderEncoder);
+    [renderEncoder endEncoding];
+
+    [commandBuffer presentDrawable:drawable];
+    [commandBuffer commit];
+}
+
+static void ImGui_ImplMetal_InitPlatformInterface()
+{
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    platform_io.Renderer_CreateWindow = ImGui_ImplMetal_CreateWindow;
+    platform_io.Renderer_DestroyWindow = ImGui_ImplMetal_DestroyWindow;
+    platform_io.Renderer_SetWindowSize = ImGui_ImplMetal_SetWindowSize;
+    platform_io.Renderer_RenderWindow = ImGui_ImplMetal_RenderWindow;
+}
+
+static void ImGui_ImplMetal_ShutdownPlatformInterface()
+{
+    ImGui::DestroyPlatformWindows();
+}
+
+static void ImGui_ImplMetal_CreateDeviceObjectsForPlatformWindows()
+{
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    for (int i = 1; i < platform_io.Viewports.Size; i++)
+        if (!platform_io.Viewports[i]->RendererUserData)
+            ImGui_ImplMetal_CreateWindow(platform_io.Viewports[i]);
+}
+
+static void ImGui_ImplMetal_InvalidateDeviceObjectsForPlatformWindows()
+{
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    for (int i = 1; i < platform_io.Viewports.Size; i++)
+        if (platform_io.Viewports[i]->RendererUserData)
+            ImGui_ImplMetal_DestroyWindow(platform_io.Viewports[i]);
+}
+
 #pragma mark - MetalBuffer implementation
 
 @implementation MetalBuffer
diff --git a/backends/imgui_impl_opengl2.cpp b/backends/imgui_impl_opengl2.cpp
index 3eb092a..4c4832e 100644
--- a/backends/imgui_impl_opengl2.cpp
+++ b/backends/imgui_impl_opengl2.cpp
@@ -3,6 +3,7 @@
 
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'GLuint' OpenGL texture identifier as void*/ImTextureID. Read the FAQ about ImTextureID!
+//  [X] Renderer: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
@@ -22,6 +23,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2024-XX-XX: Platform: Added support for multiple windows via the ImGuiPlatformIO interface.
 //  2022-10-11: Using 'nullptr' instead of 'NULL' as per our switch to C++11.
 //  2021-12-08: OpenGL: Fixed mishandling of the ImDrawCmd::IdxOffset field! This is an old bug but it never had an effect until some internal rendering changes in 1.86.
 //  2021-06-29: Reorganized backend to pull data from a single structure to facilitate usage with multiple-contexts (all g_XXXX access changed to bd->XXXX).
@@ -79,6 +81,10 @@
     return ImGui::GetCurrentContext() ? (ImGui_ImplOpenGL2_Data*)ImGui::GetIO().BackendRendererUserData : nullptr;
 }
 
+// Forward Declarations
+static void ImGui_ImplOpenGL2_InitPlatformInterface();
+static void ImGui_ImplOpenGL2_ShutdownPlatformInterface();
+
 // Functions
 bool    ImGui_ImplOpenGL2_Init()
 {
@@ -90,6 +96,10 @@
     ImGui_ImplOpenGL2_Data* bd = IM_NEW(ImGui_ImplOpenGL2_Data)();
     io.BackendRendererUserData = (void*)bd;
     io.BackendRendererName = "imgui_impl_opengl2";
+    io.BackendFlags |= ImGuiBackendFlags_RendererHasViewports;    // We can create multi-viewports on the Renderer side (optional)
+
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        ImGui_ImplOpenGL2_InitPlatformInterface();
 
     return true;
 }
@@ -100,9 +110,11 @@
     IM_ASSERT(bd != nullptr && "No renderer backend to shutdown, or already shutdown?");
     ImGuiIO& io = ImGui::GetIO();
 
+    ImGui_ImplOpenGL2_ShutdownPlatformInterface();
     ImGui_ImplOpenGL2_DestroyDeviceObjects();
     io.BackendRendererName = nullptr;
     io.BackendRendererUserData = nullptr;
+    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasViewports;
     IM_DELETE(bd);
 }
 
@@ -294,6 +306,35 @@
     ImGui_ImplOpenGL2_DestroyFontsTexture();
 }
 
+
+//--------------------------------------------------------------------------------------------------------
+// MULTI-VIEWPORT / PLATFORM INTERFACE SUPPORT
+// This is an _advanced_ and _optional_ feature, allowing the backend to create and handle multiple viewports simultaneously.
+// If you are new to dear imgui or creating a new binding for dear imgui, it is recommended that you completely ignore this section first..
+//--------------------------------------------------------------------------------------------------------
+
+static void ImGui_ImplOpenGL2_RenderWindow(ImGuiViewport* viewport, void*)
+{
+    if (!(viewport->Flags & ImGuiViewportFlags_NoRendererClear))
+    {
+        ImVec4 clear_color = ImVec4(0.0f, 0.0f, 0.0f, 1.0f);
+        glClearColor(clear_color.x, clear_color.y, clear_color.z, clear_color.w);
+        glClear(GL_COLOR_BUFFER_BIT);
+    }
+    ImGui_ImplOpenGL2_RenderDrawData(viewport->DrawData);
+}
+
+static void ImGui_ImplOpenGL2_InitPlatformInterface()
+{
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    platform_io.Renderer_RenderWindow = ImGui_ImplOpenGL2_RenderWindow;
+}
+
+static void ImGui_ImplOpenGL2_ShutdownPlatformInterface()
+{
+    ImGui::DestroyPlatformWindows();
+}
+
 //-----------------------------------------------------------------------------
 
 #if defined(__clang__)
diff --git a/backends/imgui_impl_opengl2.h b/backends/imgui_impl_opengl2.h
index 9c756c7..be8fb6c 100644
--- a/backends/imgui_impl_opengl2.h
+++ b/backends/imgui_impl_opengl2.h
@@ -3,6 +3,7 @@
 
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'GLuint' OpenGL texture identifier as void*/ImTextureID. Read the FAQ about ImTextureID!
+//  [X] Renderer: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
diff --git a/backends/imgui_impl_opengl3.cpp b/backends/imgui_impl_opengl3.cpp
index 58603a0..2a4b1d7 100644
--- a/backends/imgui_impl_opengl3.cpp
+++ b/backends/imgui_impl_opengl3.cpp
@@ -5,7 +5,8 @@
 
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'GLuint' OpenGL texture identifier as void*/ImTextureID. Read the FAQ about ImTextureID!
-//  [x] Renderer: Large meshes support (64k+ vertices) with 16-bit indices (Desktop OpenGL only).
+//  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices (Desktop OpenGL only).
+//  [X] Renderer: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
 
 // About WebGL/ES:
 // - You need to '#define IMGUI_IMPL_OPENGL_ES2' or '#define IMGUI_IMPL_OPENGL_ES3' to use WebGL or OpenGL ES.
@@ -22,6 +23,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2024-XX-XX: Platform: Added support for multiple windows via the ImGuiPlatformIO interface.
 //  2024-05-07: OpenGL: Update loader for Linux to support EGL/GLVND. (#7562)
 //  2024-04-16: OpenGL: Detect ES3 contexts on desktop based on version string, to e.g. avoid calling glPolygonMode() on them. (#7447)
 //  2024-01-09: OpenGL: Update GL3W based imgui_impl_opengl3_loader.h to load "libGL.so" and variants, fixing regression on distros missing a symlink.
@@ -247,6 +249,10 @@
     return ImGui::GetCurrentContext() ? (ImGui_ImplOpenGL3_Data*)ImGui::GetIO().BackendRendererUserData : nullptr;
 }
 
+// Forward Declarations
+static void ImGui_ImplOpenGL3_InitPlatformInterface();
+static void ImGui_ImplOpenGL3_ShutdownPlatformInterface();
+
 // OpenGL vertex attribute state (for ES 1.0 and ES 2.0 only)
 #ifndef IMGUI_IMPL_OPENGL_USE_VERTEX_ARRAY
 struct ImGui_ImplOpenGL3_VtxAttribState
@@ -339,6 +345,7 @@
     if (bd->GlVersion >= 320)
         io.BackendFlags |= ImGuiBackendFlags_RendererHasVtxOffset;  // We can honor the ImDrawCmd::VtxOffset field, allowing for large meshes.
 #endif
+    io.BackendFlags |= ImGuiBackendFlags_RendererHasViewports;  // We can create multi-viewports on the Renderer side (optional)
 
     // Store GLSL version string so we can refer to it later in case we recreate shaders.
     // Note: GLSL version is NOT the same as GL version. Leave this to nullptr if unsure.
@@ -379,6 +386,9 @@
     }
 #endif
 
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        ImGui_ImplOpenGL3_InitPlatformInterface();
+
     return true;
 }
 
@@ -388,10 +398,11 @@
     IM_ASSERT(bd != nullptr && "No renderer backend to shutdown, or already shutdown?");
     ImGuiIO& io = ImGui::GetIO();
 
+    ImGui_ImplOpenGL3_ShutdownPlatformInterface();
     ImGui_ImplOpenGL3_DestroyDeviceObjects();
     io.BackendRendererName = nullptr;
     io.BackendRendererUserData = nullptr;
-    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;
+    io.BackendFlags &= ~(ImGuiBackendFlags_RendererHasVtxOffset | ImGuiBackendFlags_RendererHasViewports);
     IM_DELETE(bd);
 }
 
@@ -945,6 +956,34 @@
     ImGui_ImplOpenGL3_DestroyFontsTexture();
 }
 
+//--------------------------------------------------------------------------------------------------------
+// MULTI-VIEWPORT / PLATFORM INTERFACE SUPPORT
+// This is an _advanced_ and _optional_ feature, allowing the backend to create and handle multiple viewports simultaneously.
+// If you are new to dear imgui or creating a new binding for dear imgui, it is recommended that you completely ignore this section first..
+//--------------------------------------------------------------------------------------------------------
+
+static void ImGui_ImplOpenGL3_RenderWindow(ImGuiViewport* viewport, void*)
+{
+    if (!(viewport->Flags & ImGuiViewportFlags_NoRendererClear))
+    {
+        ImVec4 clear_color = ImVec4(0.0f, 0.0f, 0.0f, 1.0f);
+        glClearColor(clear_color.x, clear_color.y, clear_color.z, clear_color.w);
+        glClear(GL_COLOR_BUFFER_BIT);
+    }
+    ImGui_ImplOpenGL3_RenderDrawData(viewport->DrawData);
+}
+
+static void ImGui_ImplOpenGL3_InitPlatformInterface()
+{
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    platform_io.Renderer_RenderWindow = ImGui_ImplOpenGL3_RenderWindow;
+}
+
+static void ImGui_ImplOpenGL3_ShutdownPlatformInterface()
+{
+    ImGui::DestroyPlatformWindows();
+}
+
 //-----------------------------------------------------------------------------
 
 #if defined(__GNUC__)
diff --git a/backends/imgui_impl_opengl3.h b/backends/imgui_impl_opengl3.h
index d66a15e..ae718d8 100644
--- a/backends/imgui_impl_opengl3.h
+++ b/backends/imgui_impl_opengl3.h
@@ -5,7 +5,8 @@
 
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'GLuint' OpenGL texture identifier as void*/ImTextureID. Read the FAQ about ImTextureID!
-//  [x] Renderer: Large meshes support (64k+ vertices) with 16-bit indices (Desktop OpenGL only).
+//  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices (Desktop OpenGL only).
+//  [X] Renderer: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
 
 // About WebGL/ES:
 // - You need to '#define IMGUI_IMPL_OPENGL_ES2' or '#define IMGUI_IMPL_OPENGL_ES3' to use WebGL or OpenGL ES.
diff --git a/backends/imgui_impl_osx.h b/backends/imgui_impl_osx.h
index 4033ad9..1f2254b 100644
--- a/backends/imgui_impl_osx.h
+++ b/backends/imgui_impl_osx.h
@@ -10,6 +10,10 @@
 //  [X] Platform: OSX clipboard is supported within core Dear ImGui (no specific code in this backend).
 //  [X] Platform: Gamepad support. Enabled with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
 //  [X] Platform: IME support.
+//  [x] Platform: Multi-viewport / platform windows.
+// Issues:
+//  [ ] Platform: Multi-viewport: Window size not correctly reported when enabling io.ConfigViewportsNoDecoration
+//  [ ] Platform: Multi-viewport: ParentViewportID not honored, and so io.ConfigViewportsNoDefaultParent has no effect (minor).
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
diff --git a/backends/imgui_impl_osx.mm b/backends/imgui_impl_osx.mm
index 3227980..a96027d 100644
--- a/backends/imgui_impl_osx.mm
+++ b/backends/imgui_impl_osx.mm
@@ -10,6 +10,10 @@
 //  [X] Platform: OSX clipboard is supported within core Dear ImGui (no specific code in this backend).
 //  [X] Platform: Gamepad support. Enabled with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
 //  [X] Platform: IME support.
+//  [x] Platform: Multi-viewport / platform windows.
+// Issues:
+//  [ ] Platform: Multi-viewport: Window size not correctly reported when enabling io.ConfigViewportsNoDecoration
+//  [ ] Platform: Multi-viewport: ParentViewportID not honored, and so io.ConfigViewportsNoDefaultParent has no effect (minor).
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
@@ -29,6 +33,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2024-XX-XX: Added support for multiple windows via the ImGuiPlatformIO interface.
 //  2023-10-05: Inputs: Added support for extra ImGuiKey values: F13 to F20 function keys. Stopped mapping F13 into PrintScreen.
 //  2023-04-09: Inputs: Added support for io.AddMouseSourceEvent() to discriminate ImGuiMouseSource_Mouse/ImGuiMouseSource_Pen.
 //  2023-02-01: Fixed scroll wheel scaling for devices emitting events with hasPreciseScrollingDeltas==false (e.g. non-Apple mices).
@@ -80,6 +85,7 @@
     KeyEventResponder*          KeyEventResponder;
     NSTextInputContext*         InputContext;
     id                          Monitor;
+    NSWindow*                   Window;
 
     ImGui_ImplOSX_Data()        { memset(this, 0, sizeof(*this)); }
 };
@@ -90,6 +96,9 @@
 static inline CFTimeInterval    GetMachAbsoluteTimeInSeconds()      { return (CFTimeInterval)(double)(clock_gettime_nsec_np(CLOCK_UPTIME_RAW) / 1e9); }
 
 // Forward Declarations
+static void ImGui_ImplOSX_InitPlatformInterface();
+static void ImGui_ImplOSX_ShutdownPlatformInterface();
+static void ImGui_ImplOSX_UpdateMonitors();
 static void ImGui_ImplOSX_AddTrackingArea(NSView* _Nonnull view);
 static bool ImGui_ImplOSX_HandleEvent(NSEvent* event, NSView* view);
 
@@ -133,12 +142,28 @@
 
 - (void)updateImePosWithView:(NSView *)view
 {
-    NSWindow *window = view.window;
+    NSWindow* window = view.window;
     if (!window)
         return;
-    NSRect contentRect = [window contentRectForFrameRect:window.frame];
-    NSRect rect = NSMakeRect(_posX, contentRect.size.height - _posY, 0, 0);
-    _imeRect = [window convertRectToScreen:rect];
+
+    ImGuiIO& io = ImGui::GetIO();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        NSRect frame = window.frame;
+        NSRect contentRect = window.contentLayoutRect;
+        if (window.styleMask & NSWindowStyleMaskFullSizeContentView) // No title bar windows should be considered.
+            contentRect = frame;
+
+        NSRect firstScreenFrame = NSScreen.screens[0].frame;
+        _imeRect = NSMakeRect(_posX, _posY, 0, 0);
+        _imeRect.origin.y = firstScreenFrame.size.height - _imeRect.size.height - _imeRect.origin.y; // Opposite of ConvertNSRect()
+    }
+    else
+    {
+        NSRect contentRect = [window contentRectForFrameRect:window.frame];
+        NSRect rect = NSMakeRect(_posX, contentRect.size.height - _posY, 0, 0);
+        _imeRect = [window convertRectToScreen:rect];
+    }
 }
 
 - (void)viewDidMoveToWindow
@@ -233,6 +258,7 @@
 
 - (void)onApplicationBecomeActive:(NSNotification*)aNotification;
 - (void)onApplicationBecomeInactive:(NSNotification*)aNotification;
+- (void)displaysDidChange:(NSNotification*)aNotification;
 
 @end
 
@@ -250,6 +276,11 @@
     io.AddFocusEvent(false);
 }
 
+- (void)displaysDidChange:(NSNotification*)aNotification
+{
+    ImGui_ImplOSX_UpdateMonitors();
+}
+
 @end
 
 // Functions
@@ -400,8 +431,16 @@
     io.BackendPlatformName = "imgui_impl_osx";
     io.BackendFlags |= ImGuiBackendFlags_HasMouseCursors;           // We can honor GetMouseCursor() values (optional)
     //io.BackendFlags |= ImGuiBackendFlags_HasSetMousePos;          // We can honor io.WantSetMousePos requests (optional, rarely used)
+    io.BackendFlags |= ImGuiBackendFlags_PlatformHasViewports;      // We can create multi-viewports on the Platform side (optional)
+    //io.BackendFlags |= ImGuiBackendFlags_HasMouseHoveredViewport; // We can call io.AddMouseViewportEvent() with correct data (optional)
 
     bd->Observer = [ImGuiObserver new];
+    bd->Window = view.window ?: NSApp.orderedWindows.firstObject;
+    ImGuiViewport* main_viewport = ImGui::GetMainViewport();
+    main_viewport->PlatformHandle = main_viewport->PlatformHandleRaw = (__bridge_retained void*)bd->Window;
+    ImGui_ImplOSX_UpdateMonitors();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        ImGui_ImplOSX_InitPlatformInterface();
 
     // Load cursors. Some of them are undocumented.
     bd->MouseCursorHidden = false;
@@ -491,12 +530,12 @@
         bd->Monitor = nullptr;
     }
 
+    ImGui_ImplOSX_ShutdownPlatformInterface();
     ImGui_ImplOSX_DestroyBackendData();
-
     ImGuiIO& io = ImGui::GetIO();
     io.BackendPlatformName = nullptr;
     io.BackendPlatformUserData = nullptr;
-    io.BackendFlags &= ~(ImGuiBackendFlags_HasMouseCursors | ImGuiBackendFlags_HasGamepad);
+    io.BackendFlags &= ~(ImGuiBackendFlags_HasMouseCursors | ImGuiBackendFlags_HasGamepad | ImGuiBackendFlags_PlatformHasViewports);
 }
 
 static void ImGui_ImplOSX_UpdateMouseCursor()
@@ -673,14 +712,23 @@
 
     if (event.type == NSEventTypeMouseMoved || event.type == NSEventTypeLeftMouseDragged || event.type == NSEventTypeRightMouseDragged || event.type == NSEventTypeOtherMouseDragged)
     {
-        NSPoint mousePoint = event.locationInWindow;
-        if (event.window == nil)
-            mousePoint = [[view window] convertPointFromScreen:mousePoint];
-        mousePoint = [view convertPoint:mousePoint fromView:nil];
-        if ([view isFlipped])
-            mousePoint = NSMakePoint(mousePoint.x, mousePoint.y);
+        NSPoint mousePoint;
+        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        {
+            mousePoint = NSEvent.mouseLocation;
+            mousePoint.y = CGDisplayPixelsHigh(kCGDirectMainDisplay) - mousePoint.y; // Normalize y coordinate to top-left of main display.
+        }
         else
-            mousePoint = NSMakePoint(mousePoint.x, view.bounds.size.height - mousePoint.y);
+        {
+            mousePoint = event.locationInWindow;
+            if (event.window == nil)
+                mousePoint = [[view window] convertPointFromScreen:mousePoint];
+            mousePoint = [view convertPoint:mousePoint fromView:nil]; // Convert to local coordinates of view
+            if ([view isFlipped])
+                mousePoint = NSMakePoint(mousePoint.x, mousePoint.y);
+            else
+                mousePoint = NSMakePoint(mousePoint.x, view.bounds.size.height - mousePoint.y);
+        }
         io.AddMouseSourceEvent(GetMouseSource(event));
         io.AddMousePosEvent((float)mousePoint.x, (float)mousePoint.y);
         return io.WantCaptureMouse;
@@ -808,6 +856,294 @@
     }];
 }
 
+//--------------------------------------------------------------------------------------------------------
+// MULTI-VIEWPORT / PLATFORM INTERFACE SUPPORT
+// This is an _advanced_ and _optional_ feature, allowing the back-end to create and handle multiple viewports simultaneously.
+// If you are new to dear imgui or creating a new binding for dear imgui, it is recommended that you completely ignore this section first..
+//--------------------------------------------------------------------------------------------------------
+
+struct ImGuiViewportDataOSX
+{
+    NSWindow*               Window;
+    bool                    WindowOwned;
+
+    ImGuiViewportDataOSX()  { WindowOwned = false; }
+    ~ImGuiViewportDataOSX() { IM_ASSERT(Window == nil); }
+};
+
+@interface ImGui_ImplOSX_Window: NSWindow
+@end
+
+@implementation ImGui_ImplOSX_Window
+
+- (BOOL)canBecomeKeyWindow
+{
+    return YES;
+}
+
+@end
+
+static void ConvertNSRect(NSRect* r)
+{
+    NSRect firstScreenFrame = NSScreen.screens[0].frame;
+    IM_ASSERT(firstScreenFrame.origin.x == 0 && firstScreenFrame.origin.y == 0);
+    r->origin.y = firstScreenFrame.size.height - r->origin.y - r->size.height;
+}
+
+static void ImGui_ImplOSX_CreateWindow(ImGuiViewport* viewport)
+{
+    ImGui_ImplOSX_Data* bd = ImGui_ImplOSX_GetBackendData();
+    ImGuiViewportDataOSX* data = IM_NEW(ImGuiViewportDataOSX)();
+    viewport->PlatformUserData = data;
+
+    NSScreen* screen = bd->Window.screen;
+    NSRect rect = NSMakeRect(viewport->Pos.x, viewport->Pos.y, viewport->Size.x, viewport->Size.y);
+    ConvertNSRect(&rect);
+
+    NSWindowStyleMask styleMask = 0;
+    if (viewport->Flags & ImGuiViewportFlags_NoDecoration)
+        styleMask |= NSWindowStyleMaskBorderless;
+    else
+        styleMask |= NSWindowStyleMaskTitled | NSWindowStyleMaskResizable | NSWindowStyleMaskClosable | NSWindowStyleMaskMiniaturizable;
+
+    NSWindow* window = [[ImGui_ImplOSX_Window alloc] initWithContentRect:rect
+                                                               styleMask:styleMask
+                                                                 backing:NSBackingStoreBuffered
+                                                                   defer:YES
+                                                                  screen:screen];
+    if (viewport->Flags & ImGuiViewportFlags_TopMost)
+        [window setLevel:NSFloatingWindowLevel];
+
+    window.title = @"Untitled";
+    window.opaque = YES;
+
+    KeyEventResponder* view = [[KeyEventResponder alloc] initWithFrame:rect];
+    if (floor(NSAppKitVersionNumber) > NSAppKitVersionNumber10_6)
+        [view setWantsBestResolutionOpenGLSurface:YES];
+
+    window.contentView = view;
+
+    data->Window = window;
+    data->WindowOwned = true;
+    viewport->PlatformRequestResize = false;
+    viewport->PlatformHandle = viewport->PlatformHandleRaw = (__bridge_retained void*)window;
+}
+
+static void ImGui_ImplOSX_DestroyWindow(ImGuiViewport* viewport)
+{
+    NSWindow* window = (__bridge_transfer NSWindow*)viewport->PlatformHandleRaw;
+    window = nil;
+
+    if (ImGuiViewportDataOSX* data = (ImGuiViewportDataOSX*)viewport->PlatformUserData)
+    {
+        NSWindow* window = data->Window;
+        if (window != nil && data->WindowOwned)
+        {
+            window.contentView = nil;
+            window.contentViewController = nil;
+            [window orderOut:nil];
+        }
+        data->Window = nil;
+        IM_DELETE(data);
+    }
+    viewport->PlatformUserData = viewport->PlatformHandle = viewport->PlatformHandleRaw = nullptr;
+}
+
+static void ImGui_ImplOSX_ShowWindow(ImGuiViewport* viewport)
+{
+    ImGuiViewportDataOSX* data = (ImGuiViewportDataOSX*)viewport->PlatformUserData;
+    IM_ASSERT(data->Window != 0);
+
+    if (viewport->Flags & ImGuiViewportFlags_NoFocusOnAppearing)
+        [data->Window orderFront:nil];
+    else
+        [data->Window makeKeyAndOrderFront:nil];
+
+    [data->Window setIsVisible:YES];
+}
+
+static ImVec2 ImGui_ImplOSX_GetWindowPos(ImGuiViewport* viewport)
+{
+    ImGuiViewportDataOSX* data = (ImGuiViewportDataOSX*)viewport->PlatformUserData;
+    IM_ASSERT(data->Window != 0);
+
+    NSWindow* window = data->Window;
+    NSRect frame = window.frame;
+    NSRect contentRect = window.contentLayoutRect;
+    if (window.styleMask & NSWindowStyleMaskFullSizeContentView) // No title bar windows should be considered.
+        contentRect = frame;
+
+    NSRect firstScreenFrame = NSScreen.screens[0].frame;
+    return ImVec2(frame.origin.x, firstScreenFrame.size.height - frame.origin.y - contentRect.size.height);
+}
+
+static void ImGui_ImplOSX_SetWindowPos(ImGuiViewport* viewport, ImVec2 pos)
+{
+    ImGuiViewportDataOSX* data = (ImGuiViewportDataOSX*)viewport->PlatformUserData;
+    IM_ASSERT(data->Window != 0);
+
+    NSWindow* window = data->Window;
+    NSSize size = window.frame.size;
+
+    NSRect r = NSMakeRect(pos.x, pos.y, size.width, size.height);
+    ConvertNSRect(&r);
+    [window setFrameOrigin:r.origin];
+}
+
+static ImVec2 ImGui_ImplOSX_GetWindowSize(ImGuiViewport* viewport)
+{
+    ImGuiViewportDataOSX* data = (ImGuiViewportDataOSX*)viewport->PlatformUserData;
+    IM_ASSERT(data->Window != 0);
+
+    NSWindow* window = data->Window;
+    NSSize size = window.contentLayoutRect.size;
+    return ImVec2(size.width, size.height);
+}
+
+static void ImGui_ImplOSX_SetWindowSize(ImGuiViewport* viewport, ImVec2 size)
+{
+    ImGuiViewportDataOSX* data = (ImGuiViewportDataOSX*)viewport->PlatformUserData;
+    IM_ASSERT(data->Window != 0);
+
+    NSWindow* window = data->Window;
+    NSRect rect = window.frame;
+    rect.origin.y -= (size.y - rect.size.height);
+    rect.size.width = size.x;
+    rect.size.height = size.y;
+    [window setFrame:rect display:YES];
+}
+
+static void ImGui_ImplOSX_SetWindowFocus(ImGuiViewport* viewport)
+{
+    ImGui_ImplOSX_Data* bd = ImGui_ImplOSX_GetBackendData();
+    ImGuiViewportDataOSX* data = (ImGuiViewportDataOSX*)viewport->PlatformUserData;
+    IM_ASSERT(data->Window != 0);
+    [data->Window makeKeyAndOrderFront:bd->Window];
+}
+
+static bool ImGui_ImplOSX_GetWindowFocus(ImGuiViewport* viewport)
+{
+    ImGuiViewportDataOSX* data = (ImGuiViewportDataOSX*)viewport->PlatformUserData;
+    IM_ASSERT(data->Window != 0);
+
+    return data->Window.isKeyWindow;
+}
+
+static bool ImGui_ImplOSX_GetWindowMinimized(ImGuiViewport* viewport)
+{
+    ImGuiViewportDataOSX* data = (ImGuiViewportDataOSX*)viewport->PlatformUserData;
+    IM_ASSERT(data->Window != 0);
+
+    return data->Window.isMiniaturized;
+}
+
+static void ImGui_ImplOSX_SetWindowTitle(ImGuiViewport* viewport, const char* title)
+{
+    ImGuiViewportDataOSX* data = (ImGuiViewportDataOSX*)viewport->PlatformUserData;
+    IM_ASSERT(data->Window != 0);
+
+    data->Window.title = [NSString stringWithUTF8String:title];
+}
+
+static void ImGui_ImplOSX_SetWindowAlpha(ImGuiViewport* viewport, float alpha)
+{
+    ImGuiViewportDataOSX* data = (ImGuiViewportDataOSX*)viewport->PlatformUserData;
+    IM_ASSERT(data->Window != 0);
+    IM_ASSERT(alpha >= 0.0f && alpha <= 1.0f);
+
+    data->Window.alphaValue = alpha;
+}
+
+static float ImGui_ImplOSX_GetWindowDpiScale(ImGuiViewport* viewport)
+{
+    ImGuiViewportDataOSX* data = (ImGuiViewportDataOSX*)viewport->PlatformUserData;
+    IM_ASSERT(data->Window != 0);
+
+    return data->Window.backingScaleFactor;
+}
+
+static void ImGui_ImplOSX_UpdateMonitors()
+{
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    platform_io.Monitors.resize(0);
+
+    NSRect firstScreenFrame = NSScreen.screens[0].frame;
+    IM_ASSERT(firstScreenFrame.origin.x == 0 && firstScreenFrame.origin.y == 0);
+
+    for (NSScreen* screen in NSScreen.screens)
+    {
+        NSRect frame = screen.frame;
+        NSRect visibleFrame = screen.visibleFrame;
+        ConvertNSRect(&frame);
+        ConvertNSRect(&visibleFrame);
+
+        ImGuiPlatformMonitor imgui_monitor;
+        imgui_monitor.MainPos = ImVec2(frame.origin.x, frame.origin.y);
+        imgui_monitor.MainSize = ImVec2(frame.size.width, frame.size.height);
+        imgui_monitor.WorkPos = ImVec2(visibleFrame.origin.x, visibleFrame.origin.y);
+        imgui_monitor.WorkSize = ImVec2(visibleFrame.size.width, visibleFrame.size.height);
+        imgui_monitor.DpiScale = screen.backingScaleFactor;
+        imgui_monitor.PlatformHandle = (__bridge_retained void*)screen;
+
+        platform_io.Monitors.push_back(imgui_monitor);
+    }
+}
+
+static void ImGui_ImplOSX_InitPlatformInterface()
+{
+    ImGui_ImplOSX_Data* bd = ImGui_ImplOSX_GetBackendData();
+
+    // Register platform interface (will be coupled with a renderer interface)
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    platform_io.Platform_CreateWindow = ImGui_ImplOSX_CreateWindow;
+    platform_io.Platform_DestroyWindow = ImGui_ImplOSX_DestroyWindow;
+    platform_io.Platform_ShowWindow = ImGui_ImplOSX_ShowWindow;
+    platform_io.Platform_SetWindowPos = ImGui_ImplOSX_SetWindowPos;
+    platform_io.Platform_GetWindowPos = ImGui_ImplOSX_GetWindowPos;
+    platform_io.Platform_SetWindowSize = ImGui_ImplOSX_SetWindowSize;
+    platform_io.Platform_GetWindowSize = ImGui_ImplOSX_GetWindowSize;
+    platform_io.Platform_SetWindowFocus = ImGui_ImplOSX_SetWindowFocus;
+    platform_io.Platform_GetWindowFocus = ImGui_ImplOSX_GetWindowFocus;
+    platform_io.Platform_GetWindowMinimized = ImGui_ImplOSX_GetWindowMinimized;
+    platform_io.Platform_SetWindowTitle = ImGui_ImplOSX_SetWindowTitle;
+    platform_io.Platform_SetWindowAlpha = ImGui_ImplOSX_SetWindowAlpha;
+    platform_io.Platform_GetWindowDpiScale = ImGui_ImplOSX_GetWindowDpiScale; // FIXME-DPI
+
+    // Register main window handle (which is owned by the main application, not by us)
+    ImGuiViewport* main_viewport = ImGui::GetMainViewport();
+    ImGuiViewportDataOSX* data = IM_NEW(ImGuiViewportDataOSX)();
+    data->Window = bd->Window;
+    data->WindowOwned = false;
+    main_viewport->PlatformUserData = data;
+    main_viewport->PlatformHandle = (__bridge void*)bd->Window;
+
+    [NSNotificationCenter.defaultCenter addObserver:bd->Observer
+                                           selector:@selector(displaysDidChange:)
+                                               name:NSApplicationDidChangeScreenParametersNotification
+                                             object:nil];
+}
+
+static void ImGui_ImplOSX_ShutdownPlatformInterface()
+{
+    ImGui_ImplOSX_Data* bd = ImGui_ImplOSX_GetBackendData();
+    [NSNotificationCenter.defaultCenter removeObserver:bd->Observer
+                                                  name:NSApplicationDidChangeScreenParametersNotification
+                                                object:nil];
+    bd->Observer = nullptr;
+    bd->Window = nullptr;
+    if (bd->Monitor != nullptr)
+    {
+        [NSEvent removeMonitor:bd->Monitor];
+        bd->Monitor = nullptr;
+    }
+
+    ImGuiViewport* main_viewport = ImGui::GetMainViewport();
+    ImGuiViewportDataOSX* data = (ImGuiViewportDataOSX*)main_viewport->PlatformUserData;
+    IM_DELETE(data);
+    main_viewport->PlatformUserData = nullptr;
+    ImGui::DestroyPlatformWindows();
+}
+
 //-----------------------------------------------------------------------------
 
 #endif // #ifndef IMGUI_DISABLE
diff --git a/backends/imgui_impl_sdl2.cpp b/backends/imgui_impl_sdl2.cpp
index 892fe90..38c31a5 100644
--- a/backends/imgui_impl_sdl2.cpp
+++ b/backends/imgui_impl_sdl2.cpp
@@ -9,7 +9,11 @@
 //  [X] Platform: Keyboard support. Since 1.87 we are using the io.AddKeyEvent() function. Pass ImGuiKey values to all key functions e.g. ImGui::IsKeyPressed(ImGuiKey_Space). [Legacy SDL_SCANCODE_* values will also be supported unless IMGUI_DISABLE_OBSOLETE_KEYIO is set]
 //  [X] Platform: Gamepad support. Enabled with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
 //  [X] Platform: Mouse cursor shape and visibility. Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange'.
-//  [X] Platform: Basic IME support. App needs to call 'SDL_SetHint(SDL_HINT_IME_SHOW_UI, "1");' before SDL_CreateWindow()!.
+//  [X] Platform: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
+// Issues:
+//  [ ] Platform: Multi-viewport: Minimized windows seems to break mouse wheel events (at least under Windows).
+//  [ ] Platform: Multi-viewport: ParentViewportID not honored, and so io.ConfigViewportsNoDefaultParent has no effect (minor).
+//  [x] Platform: Basic IME support. App needs to call 'SDL_SetHint(SDL_HINT_IME_SHOW_UI, "1");' before SDL_CreateWindow()!.
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
@@ -21,6 +25,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2024-XX-XX: Platform: Added support for multiple windows via the ImGuiPlatformIO interface.
 //  2024-02-14: Inputs: Handle gamepad disconnection. Added ImGui_ImplSDL2_SetGamepadMode().
 //  2023-10-05: Inputs: Added support for extra ImGuiKey values: F13 to F24 function keys, app back/forward keys.
 //  2023-04-06: Inputs: Avoid calling SDL_StartTextInput()/SDL_StopTextInput() as they don't only pertain to IME. It's unclear exactly what their relation is to IME. (#6306)
@@ -47,7 +52,7 @@
 //  2022-01-10: Inputs: calling new io.AddKeyEvent(), io.AddKeyModsEvent() + io.SetKeyEventNativeData() API (1.87+). Support for full ImGuiKey range.
 //  2021-08-17: Calling io.AddFocusEvent() on SDL_WINDOWEVENT_FOCUS_GAINED/SDL_WINDOWEVENT_FOCUS_LOST.
 //  2021-07-29: Inputs: MousePos is correctly reported when the host platform window is hovered but not focused (using SDL_GetMouseFocus() + SDL_HINT_MOUSE_FOCUS_CLICKTHROUGH, requires SDL 2.0.5+)
-//  2021-06-29: *BREAKING CHANGE* Removed 'SDL_Window* window' parameter to ImGui_ImplSDL2_NewFrame() which was unnecessary.
+//  2021-06:29: *BREAKING CHANGE* Removed 'SDL_Window* window' parameter to ImGui_ImplSDL2_NewFrame() which was unnecessary.
 //  2021-06-29: Reorganized backend to pull data from a single structure to facilitate usage with multiple-contexts (all g_XXXX access changed to bd->XXXX).
 //  2021-03-22: Rework global mouse pos availability check listing supported platforms explicitly, effectively fixing mouse access on Raspberry Pi. (#2837, #3950)
 //  2020-05-25: Misc: Report a zero display-size when window is minimized, to be consistent with other backends.
@@ -88,6 +93,7 @@
 #endif
 
 // SDL
+// (the multi-viewports feature requires SDL features supported from SDL 2.0.4+. SDL 2.0.5+ is highly recommended)
 #include <SDL.h>
 #include <SDL_syswm.h>
 #if defined(__APPLE__)
@@ -99,7 +105,15 @@
 #else
 #define SDL_HAS_CAPTURE_AND_GLOBAL_MOUSE    0
 #endif
+#define SDL_HAS_WINDOW_ALPHA                SDL_VERSION_ATLEAST(2,0,5)
+#define SDL_HAS_ALWAYS_ON_TOP               SDL_VERSION_ATLEAST(2,0,5)
+#define SDL_HAS_USABLE_DISPLAY_BOUNDS       SDL_VERSION_ATLEAST(2,0,5)
+#define SDL_HAS_PER_MONITOR_DPI             SDL_VERSION_ATLEAST(2,0,4)
 #define SDL_HAS_VULKAN                      SDL_VERSION_ATLEAST(2,0,6)
+#define SDL_HAS_DISPLAY_EVENT               SDL_VERSION_ATLEAST(2,0,9)
+#if !SDL_HAS_VULKAN
+static const Uint32 SDL_WINDOW_VULKAN = 0x10000000;
+#endif
 
 // SDL Data
 struct ImGui_ImplSDL2_Data
@@ -108,6 +122,8 @@
     SDL_Renderer*           Renderer;
     Uint64                  Time;
     char*                   ClipboardTextData;
+    bool                    UseVulkan;
+    bool                    WantUpdateMonitors;
 
     // Mouse handling
     Uint32                  MouseWindowID;
@@ -116,6 +132,7 @@
     SDL_Cursor*             MouseLastCursor;
     int                     MouseLastLeaveFrame;
     bool                    MouseCanUseGlobalState;
+    bool                    MouseCanReportHoveredViewport;  // This is hard to use/unreliable on SDL so we'll set ImGuiBackendFlags_HasMouseHoveredViewport dynamically based on state.
 
     // Gamepad handling
     ImVector<SDL_GameController*> Gamepads;
@@ -134,6 +151,11 @@
     return ImGui::GetCurrentContext() ? (ImGui_ImplSDL2_Data*)ImGui::GetIO().BackendPlatformUserData : nullptr;
 }
 
+// Forward Declarations
+static void ImGui_ImplSDL2_UpdateMonitors();
+static void ImGui_ImplSDL2_InitPlatformInterface(SDL_Window* window, void* sdl_gl_context);
+static void ImGui_ImplSDL2_ShutdownPlatformInterface();
+
 // Functions
 static const char* ImGui_ImplSDL2_GetClipboardText(void*)
 {
@@ -150,13 +172,13 @@
 }
 
 // Note: native IME will only display if user calls SDL_SetHint(SDL_HINT_IME_SHOW_UI, "1") _before_ SDL_CreateWindow().
-static void ImGui_ImplSDL2_SetPlatformImeData(ImGuiViewport*, ImGuiPlatformImeData* data)
+static void ImGui_ImplSDL2_SetPlatformImeData(ImGuiViewport* viewport, ImGuiPlatformImeData* data)
 {
     if (data->WantVisible)
     {
         SDL_Rect r;
-        r.x = (int)data->InputPos.x;
-        r.y = (int)data->InputPos.y;
+        r.x = (int)(data->InputPos.x - viewport->Pos.x);
+        r.y = (int)(data->InputPos.y - viewport->Pos.y + data->InputLineHeight);
         r.w = 1;
         r.h = (int)data->InputLineHeight;
         SDL_SetTextInputRect(&r);
@@ -315,6 +337,13 @@
         case SDL_MOUSEMOTION:
         {
             ImVec2 mouse_pos((float)event->motion.x, (float)event->motion.y);
+            if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+            {
+                int window_x, window_y;
+                SDL_GetWindowPosition(SDL_GetWindowFromID(event->motion.windowID), &window_x, &window_y);
+                mouse_pos.x += window_x;
+                mouse_pos.y += window_y;
+            }
             io.AddMouseSourceEvent(event->motion.which == SDL_TOUCH_MOUSEID ? ImGuiMouseSource_TouchScreen : ImGuiMouseSource_Mouse);
             io.AddMousePosEvent(mouse_pos.x, mouse_pos.y);
             return true;
@@ -366,6 +395,15 @@
             io.SetKeyEventNativeData(key, event->key.keysym.sym, event->key.keysym.scancode, event->key.keysym.scancode); // To support legacy indexing (<1.87 user code). Legacy backend uses SDLK_*** as indices to IsKeyXXX() functions.
             return true;
         }
+#if SDL_HAS_DISPLAY_EVENT
+        case SDL_DISPLAYEVENT:
+        {
+            // 2.0.26 has SDL_DISPLAYEVENT_CONNECTED/SDL_DISPLAYEVENT_DISCONNECTED/SDL_DISPLAYEVENT_ORIENTATION,
+            // so change of DPI/Scaling are not reflected in this event. (SDL3 has it)
+            bd->WantUpdateMonitors = true;
+            return true;
+        }
+#endif
         case SDL_WINDOWEVENT:
         {
             // - When capturing mouse, SDL will send a bunch of conflicting LEAVE/ENTER event on every mouse move, but the final ENTER tends to be right.
@@ -383,8 +421,19 @@
                 bd->MouseLastLeaveFrame = ImGui::GetFrameCount() + 1;
             if (window_event == SDL_WINDOWEVENT_FOCUS_GAINED)
                 io.AddFocusEvent(true);
-            else if (event->window.event == SDL_WINDOWEVENT_FOCUS_LOST)
+            else if (window_event == SDL_WINDOWEVENT_FOCUS_LOST)
                 io.AddFocusEvent(false);
+            if (window_event == SDL_WINDOWEVENT_CLOSE || window_event == SDL_WINDOWEVENT_MOVED || window_event == SDL_WINDOWEVENT_RESIZED)
+                if (ImGuiViewport* viewport = ImGui::FindViewportByPlatformHandle((void*)SDL_GetWindowFromID(event->window.windowID)))
+                {
+                    if (window_event == SDL_WINDOWEVENT_CLOSE)
+                        viewport->PlatformRequestClose = true;
+                    if (window_event == SDL_WINDOWEVENT_MOVED)
+                        viewport->PlatformRequestMove = true;
+                    if (window_event == SDL_WINDOWEVENT_RESIZED)
+                        viewport->PlatformRequestResize = true;
+                    return true;
+                }
             return true;
         }
         case SDL_CONTROLLERDEVICEADDED:
@@ -397,7 +446,7 @@
     return false;
 }
 
-static bool ImGui_ImplSDL2_Init(SDL_Window* window, SDL_Renderer* renderer)
+static bool ImGui_ImplSDL2_Init(SDL_Window* window, SDL_Renderer* renderer, void* sdl_gl_context)
 {
     ImGuiIO& io = ImGui::GetIO();
     IMGUI_CHECKVERSION();
@@ -418,12 +467,23 @@
     ImGui_ImplSDL2_Data* bd = IM_NEW(ImGui_ImplSDL2_Data)();
     io.BackendPlatformUserData = (void*)bd;
     io.BackendPlatformName = "imgui_impl_sdl2";
-    io.BackendFlags |= ImGuiBackendFlags_HasMouseCursors;       // We can honor GetMouseCursor() values (optional)
-    io.BackendFlags |= ImGuiBackendFlags_HasSetMousePos;        // We can honor io.WantSetMousePos requests (optional, rarely used)
+    io.BackendFlags |= ImGuiBackendFlags_HasMouseCursors;           // We can honor GetMouseCursor() values (optional)
+    io.BackendFlags |= ImGuiBackendFlags_HasSetMousePos;            // We can honor io.WantSetMousePos requests (optional, rarely used)
+    if (mouse_can_use_global_state)
+        io.BackendFlags |= ImGuiBackendFlags_PlatformHasViewports;  // We can create multi-viewports on the Platform side (optional)
 
     bd->Window = window;
     bd->Renderer = renderer;
+
+    // SDL on Linux/OSX doesn't report events for unfocused windows (see https://github.com/ocornut/imgui/issues/4960)
+    // We will use 'MouseCanReportHoveredViewport' to set 'ImGuiBackendFlags_HasMouseHoveredViewport' dynamically each frame.
     bd->MouseCanUseGlobalState = mouse_can_use_global_state;
+#ifndef __APPLE__
+    bd->MouseCanReportHoveredViewport = bd->MouseCanUseGlobalState;
+#else
+    bd->MouseCanReportHoveredViewport = false;
+#endif
+    bd->WantUpdateMonitors = true;
 
     io.SetClipboardTextFn = ImGui_ImplSDL2_SetClipboardText;
     io.GetClipboardTextFn = ImGui_ImplSDL2_GetClipboardText;
@@ -448,6 +508,7 @@
     // Set platform dependent data in viewport
     // Our mouse update function expect PlatformHandle to be filled for the main viewport
     ImGuiViewport* main_viewport = ImGui::GetMainViewport();
+    main_viewport->PlatformHandle = (void*)window;
     main_viewport->PlatformHandleRaw = nullptr;
     SDL_SysWMinfo info;
     SDL_VERSION(&info.version);
@@ -481,13 +542,17 @@
     SDL_SetHint(SDL_HINT_MOUSE_AUTO_CAPTURE, "0");
 #endif
 
+    // We need SDL_CaptureMouse(), SDL_GetGlobalMouseState() from SDL 2.0.4+ to support multiple viewports.
+    // We left the call to ImGui_ImplSDL2_InitPlatformInterface() outside of #ifdef to avoid unused-function warnings.
+    if ((io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable) && (io.BackendFlags & ImGuiBackendFlags_PlatformHasViewports))
+        ImGui_ImplSDL2_InitPlatformInterface(window, sdl_gl_context);
+
     return true;
 }
 
 bool ImGui_ImplSDL2_InitForOpenGL(SDL_Window* window, void* sdl_gl_context)
 {
-    IM_UNUSED(sdl_gl_context); // Viewport branch will need this.
-    return ImGui_ImplSDL2_Init(window, nullptr);
+    return ImGui_ImplSDL2_Init(window, nullptr, sdl_gl_context);
 }
 
 bool ImGui_ImplSDL2_InitForVulkan(SDL_Window* window)
@@ -495,7 +560,11 @@
 #if !SDL_HAS_VULKAN
     IM_ASSERT(0 && "Unsupported");
 #endif
-    return ImGui_ImplSDL2_Init(window, nullptr);
+    if (!ImGui_ImplSDL2_Init(window, nullptr, nullptr))
+        return false;
+    ImGui_ImplSDL2_Data* bd = ImGui_ImplSDL2_GetBackendData();
+    bd->UseVulkan = true;
+    return true;
 }
 
 bool ImGui_ImplSDL2_InitForD3D(SDL_Window* window)
@@ -503,22 +572,22 @@
 #if !defined(_WIN32)
     IM_ASSERT(0 && "Unsupported");
 #endif
-    return ImGui_ImplSDL2_Init(window, nullptr);
+    return ImGui_ImplSDL2_Init(window, nullptr, nullptr);
 }
 
 bool ImGui_ImplSDL2_InitForMetal(SDL_Window* window)
 {
-    return ImGui_ImplSDL2_Init(window, nullptr);
+    return ImGui_ImplSDL2_Init(window, nullptr, nullptr);
 }
 
 bool ImGui_ImplSDL2_InitForSDLRenderer(SDL_Window* window, SDL_Renderer* renderer)
 {
-    return ImGui_ImplSDL2_Init(window, renderer);
+    return ImGui_ImplSDL2_Init(window, renderer, nullptr);
 }
 
 bool ImGui_ImplSDL2_InitForOther(SDL_Window* window)
 {
-    return ImGui_ImplSDL2_Init(window, nullptr);
+    return ImGui_ImplSDL2_Init(window, nullptr, nullptr);
 }
 
 static void ImGui_ImplSDL2_CloseGamepads();
@@ -529,6 +598,8 @@
     IM_ASSERT(bd != nullptr && "No platform backend to shutdown, or already shutdown?");
     ImGuiIO& io = ImGui::GetIO();
 
+    ImGui_ImplSDL2_ShutdownPlatformInterface();
+
     if (bd->ClipboardTextData)
         SDL_free(bd->ClipboardTextData);
     for (ImGuiMouseCursor cursor_n = 0; cursor_n < ImGuiMouseCursor_COUNT; cursor_n++)
@@ -537,10 +608,11 @@
 
     io.BackendPlatformName = nullptr;
     io.BackendPlatformUserData = nullptr;
-    io.BackendFlags &= ~(ImGuiBackendFlags_HasMouseCursors | ImGuiBackendFlags_HasSetMousePos | ImGuiBackendFlags_HasGamepad);
+    io.BackendFlags &= ~(ImGuiBackendFlags_HasMouseCursors | ImGuiBackendFlags_HasSetMousePos | ImGuiBackendFlags_HasGamepad | ImGuiBackendFlags_PlatformHasViewports | ImGuiBackendFlags_HasMouseHoveredViewport);
     IM_DELETE(bd);
 }
 
+// This code is incredibly messy because some of the functions we need for full viewport support are not available in SDL < 2.0.4.
 static void ImGui_ImplSDL2_UpdateMouseData()
 {
     ImGui_ImplSDL2_Data* bd = ImGui_ImplSDL2_GetBackendData();
@@ -551,25 +623,57 @@
     // SDL_CaptureMouse() let the OS know e.g. that our imgui drag outside the SDL window boundaries shouldn't e.g. trigger other operations outside
     SDL_CaptureMouse((bd->MouseButtonsDown != 0) ? SDL_TRUE : SDL_FALSE);
     SDL_Window* focused_window = SDL_GetKeyboardFocus();
-    const bool is_app_focused = (bd->Window == focused_window);
+    const bool is_app_focused = (focused_window && (bd->Window == focused_window || ImGui::FindViewportByPlatformHandle((void*)focused_window)));
 #else
+    SDL_Window* focused_window = bd->Window;
     const bool is_app_focused = (SDL_GetWindowFlags(bd->Window) & SDL_WINDOW_INPUT_FOCUS) != 0; // SDL 2.0.3 and non-windowed systems: single-viewport only
 #endif
+
     if (is_app_focused)
     {
         // (Optional) Set OS mouse position from Dear ImGui if requested (rarely used, only when ImGuiConfigFlags_NavEnableSetMousePos is enabled by user)
         if (io.WantSetMousePos)
-            SDL_WarpMouseInWindow(bd->Window, (int)io.MousePos.x, (int)io.MousePos.y);
+        {
+#if SDL_HAS_CAPTURE_AND_GLOBAL_MOUSE
+            if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+                SDL_WarpMouseGlobal((int)io.MousePos.x, (int)io.MousePos.y);
+            else
+#endif
+                SDL_WarpMouseInWindow(bd->Window, (int)io.MousePos.x, (int)io.MousePos.y);
+        }
 
         // (Optional) Fallback to provide mouse position when focused (SDL_MOUSEMOTION already provides this when hovered or captured)
         if (bd->MouseCanUseGlobalState && bd->MouseButtonsDown == 0)
         {
-            int window_x, window_y, mouse_x_global, mouse_y_global;
-            SDL_GetGlobalMouseState(&mouse_x_global, &mouse_y_global);
-            SDL_GetWindowPosition(bd->Window, &window_x, &window_y);
-            io.AddMousePosEvent((float)(mouse_x_global - window_x), (float)(mouse_y_global - window_y));
+            // Single-viewport mode: mouse position in client window coordinates (io.MousePos is (0,0) when the mouse is on the upper-left corner of the app window)
+            // Multi-viewport mode: mouse position in OS absolute coordinates (io.MousePos is (0,0) when the mouse is on the upper-left of the primary monitor)
+            int mouse_x, mouse_y, window_x, window_y;
+            SDL_GetGlobalMouseState(&mouse_x, &mouse_y);
+            if (!(io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable))
+            {
+                SDL_GetWindowPosition(focused_window, &window_x, &window_y);
+                mouse_x -= window_x;
+                mouse_y -= window_y;
+            }
+            io.AddMousePosEvent((float)mouse_x, (float)mouse_y);
         }
     }
+
+    // (Optional) When using multiple viewports: call io.AddMouseViewportEvent() with the viewport the OS mouse cursor is hovering.
+    // If ImGuiBackendFlags_HasMouseHoveredViewport is not set by the backend, Dear imGui will ignore this field and infer the information using its flawed heuristic.
+    // - [!] SDL backend does NOT correctly ignore viewports with the _NoInputs flag.
+    //       Some backend are not able to handle that correctly. If a backend report an hovered viewport that has the _NoInputs flag (e.g. when dragging a window
+    //       for docking, the viewport has the _NoInputs flag in order to allow us to find the viewport under), then Dear ImGui is forced to ignore the value reported
+    //       by the backend, and use its flawed heuristic to guess the viewport behind.
+    // - [X] SDL backend correctly reports this regardless of another viewport behind focused and dragged from (we need this to find a useful drag and drop target).
+    if (io.BackendFlags & ImGuiBackendFlags_HasMouseHoveredViewport)
+    {
+        ImGuiID mouse_viewport_id = 0;
+        if (SDL_Window* sdl_mouse_window = SDL_GetWindowFromID(bd->MouseWindowID))
+            if (ImGuiViewport* mouse_viewport = ImGui::FindViewportByPlatformHandle((void*)sdl_mouse_window))
+                mouse_viewport_id = mouse_viewport->ID;
+        io.AddMouseViewportEvent(mouse_viewport_id);
+    }
 }
 
 static void ImGui_ImplSDL2_UpdateMouseCursor()
@@ -703,6 +807,39 @@
     ImGui_ImplSDL2_UpdateGamepadAnalog(bd, io, ImGuiKey_GamepadRStickDown,  SDL_CONTROLLER_AXIS_RIGHTY, +thumb_dead_zone, +32767);
 }
 
+// FIXME: Note that doesn't update with DPI/Scaling change only as SDL2 doesn't have an event for it (SDL3 has).
+static void ImGui_ImplSDL2_UpdateMonitors()
+{
+    ImGui_ImplSDL2_Data* bd = ImGui_ImplSDL2_GetBackendData();
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    platform_io.Monitors.resize(0);
+    bd->WantUpdateMonitors = false;
+    int display_count = SDL_GetNumVideoDisplays();
+    for (int n = 0; n < display_count; n++)
+    {
+        // Warning: the validity of monitor DPI information on Windows depends on the application DPI awareness settings, which generally needs to be set in the manifest or at runtime.
+        ImGuiPlatformMonitor monitor;
+        SDL_Rect r;
+        SDL_GetDisplayBounds(n, &r);
+        monitor.MainPos = monitor.WorkPos = ImVec2((float)r.x, (float)r.y);
+        monitor.MainSize = monitor.WorkSize = ImVec2((float)r.w, (float)r.h);
+#if SDL_HAS_USABLE_DISPLAY_BOUNDS
+        SDL_GetDisplayUsableBounds(n, &r);
+        monitor.WorkPos = ImVec2((float)r.x, (float)r.y);
+        monitor.WorkSize = ImVec2((float)r.w, (float)r.h);
+#endif
+#if SDL_HAS_PER_MONITOR_DPI
+        // FIXME-VIEWPORT: On MacOS SDL reports actual monitor DPI scale, ignoring OS configuration. We may want to set
+        //  DpiScale to cocoa_window.backingScaleFactor here.
+        float dpi = 0.0f;
+        if (!SDL_GetDisplayDPI(n, &dpi, nullptr, nullptr))
+            monitor.DpiScale = dpi / 96.0f;
+#endif
+        monitor.PlatformHandle = (void*)(intptr_t)n;
+        platform_io.Monitors.push_back(monitor);
+    }
+}
+
 void ImGui_ImplSDL2_NewFrame()
 {
     ImGui_ImplSDL2_Data* bd = ImGui_ImplSDL2_GetBackendData();
@@ -723,6 +860,10 @@
     if (w > 0 && h > 0)
         io.DisplayFramebufferScale = ImVec2((float)display_w / w, (float)display_h / h);
 
+    // Update monitors
+    if (bd->WantUpdateMonitors)
+        ImGui_ImplSDL2_UpdateMonitors();
+
     // Setup time step (we don't use SDL_GetTicks() because it is using millisecond resolution)
     // (Accept SDL_GetPerformanceCounter() not returning a monotonically increasing value. Happens in VMs and Emscripten, see #6189, #6114, #3644)
     static Uint64 frequency = SDL_GetPerformanceFrequency();
@@ -739,6 +880,13 @@
         io.AddMousePosEvent(-FLT_MAX, -FLT_MAX);
     }
 
+    // Our io.AddMouseViewportEvent() calls will only be valid when not capturing.
+    // Technically speaking testing for 'bd->MouseButtonsDown == 0' would be more rygorous, but testing for payload reduces noise and potential side-effects.
+    if (bd->MouseCanReportHoveredViewport && ImGui::GetDragDropPayload() == nullptr)
+        io.BackendFlags |= ImGuiBackendFlags_HasMouseHoveredViewport;
+    else
+        io.BackendFlags &= ~ImGuiBackendFlags_HasMouseHoveredViewport;
+
     ImGui_ImplSDL2_UpdateMouseData();
     ImGui_ImplSDL2_UpdateMouseCursor();
 
@@ -746,6 +894,253 @@
     ImGui_ImplSDL2_UpdateGamepads();
 }
 
+//--------------------------------------------------------------------------------------------------------
+// MULTI-VIEWPORT / PLATFORM INTERFACE SUPPORT
+// This is an _advanced_ and _optional_ feature, allowing the backend to create and handle multiple viewports simultaneously.
+// If you are new to dear imgui or creating a new binding for dear imgui, it is recommended that you completely ignore this section first..
+//--------------------------------------------------------------------------------------------------------
+
+// Helper structure we store in the void* RendererUserData field of each ImGuiViewport to easily retrieve our backend data.
+struct ImGui_ImplSDL2_ViewportData
+{
+    SDL_Window*     Window;
+    Uint32          WindowID;
+    bool            WindowOwned;
+    SDL_GLContext   GLContext;
+
+    ImGui_ImplSDL2_ViewportData() { Window = nullptr; WindowID = 0; WindowOwned = false; GLContext = nullptr; }
+    ~ImGui_ImplSDL2_ViewportData() { IM_ASSERT(Window == nullptr && GLContext == nullptr); }
+};
+
+static void ImGui_ImplSDL2_CreateWindow(ImGuiViewport* viewport)
+{
+    ImGui_ImplSDL2_Data* bd = ImGui_ImplSDL2_GetBackendData();
+    ImGui_ImplSDL2_ViewportData* vd = IM_NEW(ImGui_ImplSDL2_ViewportData)();
+    viewport->PlatformUserData = vd;
+
+    ImGuiViewport* main_viewport = ImGui::GetMainViewport();
+    ImGui_ImplSDL2_ViewportData* main_viewport_data = (ImGui_ImplSDL2_ViewportData*)main_viewport->PlatformUserData;
+
+    // Share GL resources with main context
+    bool use_opengl = (main_viewport_data->GLContext != nullptr);
+    SDL_GLContext backup_context = nullptr;
+    if (use_opengl)
+    {
+        backup_context = SDL_GL_GetCurrentContext();
+        SDL_GL_SetAttribute(SDL_GL_SHARE_WITH_CURRENT_CONTEXT, 1);
+        SDL_GL_MakeCurrent(main_viewport_data->Window, main_viewport_data->GLContext);
+    }
+
+    Uint32 sdl_flags = 0;
+    sdl_flags |= use_opengl ? SDL_WINDOW_OPENGL : (bd->UseVulkan ? SDL_WINDOW_VULKAN : 0);
+    sdl_flags |= SDL_GetWindowFlags(bd->Window) & SDL_WINDOW_ALLOW_HIGHDPI;
+    sdl_flags |= SDL_WINDOW_HIDDEN;
+    sdl_flags |= (viewport->Flags & ImGuiViewportFlags_NoDecoration) ? SDL_WINDOW_BORDERLESS : 0;
+    sdl_flags |= (viewport->Flags & ImGuiViewportFlags_NoDecoration) ? 0 : SDL_WINDOW_RESIZABLE;
+#if !defined(_WIN32)
+    // See SDL hack in ImGui_ImplSDL2_ShowWindow().
+    sdl_flags |= (viewport->Flags & ImGuiViewportFlags_NoTaskBarIcon) ? SDL_WINDOW_SKIP_TASKBAR : 0;
+#endif
+#if SDL_HAS_ALWAYS_ON_TOP
+    sdl_flags |= (viewport->Flags & ImGuiViewportFlags_TopMost) ? SDL_WINDOW_ALWAYS_ON_TOP : 0;
+#endif
+    vd->Window = SDL_CreateWindow("No Title Yet", (int)viewport->Pos.x, (int)viewport->Pos.y, (int)viewport->Size.x, (int)viewport->Size.y, sdl_flags);
+    vd->WindowOwned = true;
+    if (use_opengl)
+    {
+        vd->GLContext = SDL_GL_CreateContext(vd->Window);
+        SDL_GL_SetSwapInterval(0);
+    }
+    if (use_opengl && backup_context)
+        SDL_GL_MakeCurrent(vd->Window, backup_context);
+
+    viewport->PlatformHandle = (void*)vd->Window;
+    viewport->PlatformHandleRaw = nullptr;
+    SDL_SysWMinfo info;
+    SDL_VERSION(&info.version);
+    if (SDL_GetWindowWMInfo(vd->Window, &info))
+    {
+#if defined(SDL_VIDEO_DRIVER_WINDOWS)
+        viewport->PlatformHandleRaw = info.info.win.window;
+#elif defined(__APPLE__) && defined(SDL_VIDEO_DRIVER_COCOA)
+        viewport->PlatformHandleRaw = (void*)info.info.cocoa.window;
+#endif
+    }
+}
+
+static void ImGui_ImplSDL2_DestroyWindow(ImGuiViewport* viewport)
+{
+    if (ImGui_ImplSDL2_ViewportData* vd = (ImGui_ImplSDL2_ViewportData*)viewport->PlatformUserData)
+    {
+        if (vd->GLContext && vd->WindowOwned)
+            SDL_GL_DeleteContext(vd->GLContext);
+        if (vd->Window && vd->WindowOwned)
+            SDL_DestroyWindow(vd->Window);
+        vd->GLContext = nullptr;
+        vd->Window = nullptr;
+        IM_DELETE(vd);
+    }
+    viewport->PlatformUserData = viewport->PlatformHandle = nullptr;
+}
+
+static void ImGui_ImplSDL2_ShowWindow(ImGuiViewport* viewport)
+{
+    ImGui_ImplSDL2_ViewportData* vd = (ImGui_ImplSDL2_ViewportData*)viewport->PlatformUserData;
+#if defined(_WIN32)
+    HWND hwnd = (HWND)viewport->PlatformHandleRaw;
+
+    // SDL hack: Hide icon from task bar
+    // Note: SDL 2.0.6+ has a SDL_WINDOW_SKIP_TASKBAR flag which is supported under Windows but the way it create the window breaks our seamless transition.
+    if (viewport->Flags & ImGuiViewportFlags_NoTaskBarIcon)
+    {
+        LONG ex_style = ::GetWindowLong(hwnd, GWL_EXSTYLE);
+        ex_style &= ~WS_EX_APPWINDOW;
+        ex_style |= WS_EX_TOOLWINDOW;
+        ::SetWindowLong(hwnd, GWL_EXSTYLE, ex_style);
+    }
+
+    // SDL hack: SDL always activate/focus windows :/
+    if (viewport->Flags & ImGuiViewportFlags_NoFocusOnAppearing)
+    {
+        ::ShowWindow(hwnd, SW_SHOWNA);
+        return;
+    }
+#endif
+
+    SDL_ShowWindow(vd->Window);
+}
+
+static ImVec2 ImGui_ImplSDL2_GetWindowPos(ImGuiViewport* viewport)
+{
+    ImGui_ImplSDL2_ViewportData* vd = (ImGui_ImplSDL2_ViewportData*)viewport->PlatformUserData;
+    int x = 0, y = 0;
+    SDL_GetWindowPosition(vd->Window, &x, &y);
+    return ImVec2((float)x, (float)y);
+}
+
+static void ImGui_ImplSDL2_SetWindowPos(ImGuiViewport* viewport, ImVec2 pos)
+{
+    ImGui_ImplSDL2_ViewportData* vd = (ImGui_ImplSDL2_ViewportData*)viewport->PlatformUserData;
+    SDL_SetWindowPosition(vd->Window, (int)pos.x, (int)pos.y);
+}
+
+static ImVec2 ImGui_ImplSDL2_GetWindowSize(ImGuiViewport* viewport)
+{
+    ImGui_ImplSDL2_ViewportData* vd = (ImGui_ImplSDL2_ViewportData*)viewport->PlatformUserData;
+    int w = 0, h = 0;
+    SDL_GetWindowSize(vd->Window, &w, &h);
+    return ImVec2((float)w, (float)h);
+}
+
+static void ImGui_ImplSDL2_SetWindowSize(ImGuiViewport* viewport, ImVec2 size)
+{
+    ImGui_ImplSDL2_ViewportData* vd = (ImGui_ImplSDL2_ViewportData*)viewport->PlatformUserData;
+    SDL_SetWindowSize(vd->Window, (int)size.x, (int)size.y);
+}
+
+static void ImGui_ImplSDL2_SetWindowTitle(ImGuiViewport* viewport, const char* title)
+{
+    ImGui_ImplSDL2_ViewportData* vd = (ImGui_ImplSDL2_ViewportData*)viewport->PlatformUserData;
+    SDL_SetWindowTitle(vd->Window, title);
+}
+
+#if SDL_HAS_WINDOW_ALPHA
+static void ImGui_ImplSDL2_SetWindowAlpha(ImGuiViewport* viewport, float alpha)
+{
+    ImGui_ImplSDL2_ViewportData* vd = (ImGui_ImplSDL2_ViewportData*)viewport->PlatformUserData;
+    SDL_SetWindowOpacity(vd->Window, alpha);
+}
+#endif
+
+static void ImGui_ImplSDL2_SetWindowFocus(ImGuiViewport* viewport)
+{
+    ImGui_ImplSDL2_ViewportData* vd = (ImGui_ImplSDL2_ViewportData*)viewport->PlatformUserData;
+    SDL_RaiseWindow(vd->Window);
+}
+
+static bool ImGui_ImplSDL2_GetWindowFocus(ImGuiViewport* viewport)
+{
+    ImGui_ImplSDL2_ViewportData* vd = (ImGui_ImplSDL2_ViewportData*)viewport->PlatformUserData;
+    return (SDL_GetWindowFlags(vd->Window) & SDL_WINDOW_INPUT_FOCUS) != 0;
+}
+
+static bool ImGui_ImplSDL2_GetWindowMinimized(ImGuiViewport* viewport)
+{
+    ImGui_ImplSDL2_ViewportData* vd = (ImGui_ImplSDL2_ViewportData*)viewport->PlatformUserData;
+    return (SDL_GetWindowFlags(vd->Window) & SDL_WINDOW_MINIMIZED) != 0;
+}
+
+static void ImGui_ImplSDL2_RenderWindow(ImGuiViewport* viewport, void*)
+{
+    ImGui_ImplSDL2_ViewportData* vd = (ImGui_ImplSDL2_ViewportData*)viewport->PlatformUserData;
+    if (vd->GLContext)
+        SDL_GL_MakeCurrent(vd->Window, vd->GLContext);
+}
+
+static void ImGui_ImplSDL2_SwapBuffers(ImGuiViewport* viewport, void*)
+{
+    ImGui_ImplSDL2_ViewportData* vd = (ImGui_ImplSDL2_ViewportData*)viewport->PlatformUserData;
+    if (vd->GLContext)
+    {
+        SDL_GL_MakeCurrent(vd->Window, vd->GLContext);
+        SDL_GL_SwapWindow(vd->Window);
+    }
+}
+
+// Vulkan support (the Vulkan renderer needs to call a platform-side support function to create the surface)
+// SDL is graceful enough to _not_ need <vulkan/vulkan.h> so we can safely include this.
+#if SDL_HAS_VULKAN
+#include <SDL_vulkan.h>
+static int ImGui_ImplSDL2_CreateVkSurface(ImGuiViewport* viewport, ImU64 vk_instance, const void* vk_allocator, ImU64* out_vk_surface)
+{
+    ImGui_ImplSDL2_ViewportData* vd = (ImGui_ImplSDL2_ViewportData*)viewport->PlatformUserData;
+    (void)vk_allocator;
+    SDL_bool ret = SDL_Vulkan_CreateSurface(vd->Window, (VkInstance)vk_instance, (VkSurfaceKHR*)out_vk_surface);
+    return ret ? 0 : 1; // ret ? VK_SUCCESS : VK_NOT_READY
+}
+#endif // SDL_HAS_VULKAN
+
+static void ImGui_ImplSDL2_InitPlatformInterface(SDL_Window* window, void* sdl_gl_context)
+{
+    // Register platform interface (will be coupled with a renderer interface)
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    platform_io.Platform_CreateWindow = ImGui_ImplSDL2_CreateWindow;
+    platform_io.Platform_DestroyWindow = ImGui_ImplSDL2_DestroyWindow;
+    platform_io.Platform_ShowWindow = ImGui_ImplSDL2_ShowWindow;
+    platform_io.Platform_SetWindowPos = ImGui_ImplSDL2_SetWindowPos;
+    platform_io.Platform_GetWindowPos = ImGui_ImplSDL2_GetWindowPos;
+    platform_io.Platform_SetWindowSize = ImGui_ImplSDL2_SetWindowSize;
+    platform_io.Platform_GetWindowSize = ImGui_ImplSDL2_GetWindowSize;
+    platform_io.Platform_SetWindowFocus = ImGui_ImplSDL2_SetWindowFocus;
+    platform_io.Platform_GetWindowFocus = ImGui_ImplSDL2_GetWindowFocus;
+    platform_io.Platform_GetWindowMinimized = ImGui_ImplSDL2_GetWindowMinimized;
+    platform_io.Platform_SetWindowTitle = ImGui_ImplSDL2_SetWindowTitle;
+    platform_io.Platform_RenderWindow = ImGui_ImplSDL2_RenderWindow;
+    platform_io.Platform_SwapBuffers = ImGui_ImplSDL2_SwapBuffers;
+#if SDL_HAS_WINDOW_ALPHA
+    platform_io.Platform_SetWindowAlpha = ImGui_ImplSDL2_SetWindowAlpha;
+#endif
+#if SDL_HAS_VULKAN
+    platform_io.Platform_CreateVkSurface = ImGui_ImplSDL2_CreateVkSurface;
+#endif
+
+    // Register main window handle (which is owned by the main application, not by us)
+    // This is mostly for simplicity and consistency, so that our code (e.g. mouse handling etc.) can use same logic for main and secondary viewports.
+    ImGuiViewport* main_viewport = ImGui::GetMainViewport();
+    ImGui_ImplSDL2_ViewportData* vd = IM_NEW(ImGui_ImplSDL2_ViewportData)();
+    vd->Window = window;
+    vd->WindowID = SDL_GetWindowID(window);
+    vd->WindowOwned = false;
+    vd->GLContext = sdl_gl_context;
+    main_viewport->PlatformUserData = vd;
+    main_viewport->PlatformHandle = vd->Window;
+}
+
+static void ImGui_ImplSDL2_ShutdownPlatformInterface()
+{
+    ImGui::DestroyPlatformWindows();
+}
+
 //-----------------------------------------------------------------------------
 
 #if defined(__clang__)
diff --git a/backends/imgui_impl_sdl2.h b/backends/imgui_impl_sdl2.h
index 7020a29..1fba66c 100644
--- a/backends/imgui_impl_sdl2.h
+++ b/backends/imgui_impl_sdl2.h
@@ -8,7 +8,11 @@
 //  [X] Platform: Keyboard support. Since 1.87 we are using the io.AddKeyEvent() function. Pass ImGuiKey values to all key functions e.g. ImGui::IsKeyPressed(ImGuiKey_Space). [Legacy SDL_SCANCODE_* values will also be supported unless IMGUI_DISABLE_OBSOLETE_KEYIO is set]
 //  [X] Platform: Gamepad support. Enabled with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
 //  [X] Platform: Mouse cursor shape and visibility. Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange'.
-//  [X] Platform: Basic IME support. App needs to call 'SDL_SetHint(SDL_HINT_IME_SHOW_UI, "1");' before SDL_CreateWindow()!.
+//  [X] Platform: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
+// Issues:
+//  [ ] Platform: Multi-viewport: Minimized windows seems to break mouse wheel events (at least under Windows).
+//  [ ] Platform: Multi-viewport: ParentViewportID not honored, and so io.ConfigViewportsNoDefaultParent has no effect (minor).
+//  [x] Platform: Basic IME support. App needs to call 'SDL_SetHint(SDL_HINT_IME_SHOW_UI, "1");' before SDL_CreateWindow()!.
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
diff --git a/backends/imgui_impl_sdl3.cpp b/backends/imgui_impl_sdl3.cpp
index 0838766..8922487 100644
--- a/backends/imgui_impl_sdl3.cpp
+++ b/backends/imgui_impl_sdl3.cpp
@@ -9,7 +9,10 @@
 //  [X] Platform: Keyboard support. Since 1.87 we are using the io.AddKeyEvent() function. Pass ImGuiKey values to all key functions e.g. ImGui::IsKeyPressed(ImGuiKey_Space). [Legacy SDL_SCANCODE_* values will also be supported unless IMGUI_DISABLE_OBSOLETE_KEYIO is set]
 //  [X] Platform: Gamepad support. Enabled with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
 //  [X] Platform: Mouse cursor shape and visibility. Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange'.
-// Missing features:
+//  [x] Platform: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable' -> the OS animation effect when window gets created/destroyed is problematic. SDL2 backend doesn't have issue.
+// Issues:
+//  [ ] Platform: Multi-viewport: Minimized windows seems to break mouse wheel events (at least under Windows).
+//  [ ] Platform: Multi-viewport: ParentViewportID not honored, and so io.ConfigViewportsNoDefaultParent has no effect (minor).
 //  [ ] Platform: IME SUPPORT IS BROKEN IN SDL3 BECAUSE INPUTS GETS SENT TO BOTH APP AND IME + app needs to call 'SDL_SetHint(SDL_HINT_IME_SHOW_UI, "1");' before SDL_CreateWindow()!.
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
@@ -22,6 +25,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2024-XX-XX: Platform: Added support for multiple windows via the ImGuiPlatformIO interface.
 //  2024-04-15: Inputs: Re-enable calling SDL_StartTextInput()/SDL_StopTextInput() as SDL3 no longer enables it by default and should play nicer with IME.
 //  2024-02-13: Inputs: Fixed gamepad support. Handle gamepad disconnection. Added ImGui_ImplSDL3_SetGamepadMode().
 //  2023-11-13: Updated for recent SDL3 API changes.
@@ -75,6 +79,8 @@
     SDL_Renderer*           Renderer;
     Uint64                  Time;
     char*                   ClipboardTextData;
+    bool                    UseVulkan;
+    bool                    WantUpdateMonitors;
 
     // Mouse handling
     Uint32                  MouseWindowID;
@@ -83,11 +89,12 @@
     SDL_Cursor*             MouseLastCursor;
     int                     MousePendingLeaveFrame;
     bool                    MouseCanUseGlobalState;
+    bool                    MouseCanReportHoveredViewport;  // This is hard to use/unreliable on SDL so we'll set ImGuiBackendFlags_HasMouseHoveredViewport dynamically based on state.
 
     // Gamepad handling
-    ImVector<SDL_Gamepad*>      Gamepads;
+    ImVector<SDL_Gamepad*>  Gamepads;
     ImGui_ImplSDL3_GamepadMode  GamepadMode;
-    bool                        WantUpdateGamepadsList;
+    bool                    WantUpdateGamepadsList;
 
     ImGui_ImplSDL3_Data()   { memset((void*)this, 0, sizeof(*this)); }
 };
@@ -101,6 +108,11 @@
     return ImGui::GetCurrentContext() ? (ImGui_ImplSDL3_Data*)ImGui::GetIO().BackendPlatformUserData : nullptr;
 }
 
+// Forward Declarations
+static void ImGui_ImplSDL3_UpdateMonitors();
+static void ImGui_ImplSDL3_InitPlatformInterface(SDL_Window* window, void* sdl_gl_context);
+static void ImGui_ImplSDL3_ShutdownPlatformInterface();
+
 // Functions
 static const char* ImGui_ImplSDL3_GetClipboardText(void*)
 {
@@ -116,13 +128,13 @@
     SDL_SetClipboardText(text);
 }
 
-static void ImGui_ImplSDL3_SetPlatformImeData(ImGuiViewport*, ImGuiPlatformImeData* data)
+static void ImGui_ImplSDL3_SetPlatformImeData(ImGuiViewport* viewport, ImGuiPlatformImeData* data)
 {
     if (data->WantVisible)
     {
         SDL_Rect r;
-        r.x = (int)data->InputPos.x;
-        r.y = (int)data->InputPos.y;
+        r.x = (int)(data->InputPos.x - viewport->Pos.x);
+        r.y = (int)(data->InputPos.y - viewport->Pos.y + data->InputLineHeight);
         r.w = 1;
         r.h = (int)data->InputLineHeight;
         SDL_SetTextInputRect(&r);
@@ -286,6 +298,13 @@
         case SDL_EVENT_MOUSE_MOTION:
         {
             ImVec2 mouse_pos((float)event->motion.x, (float)event->motion.y);
+            if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+            {
+                int window_x, window_y;
+                SDL_GetWindowPosition(SDL_GetWindowFromID(event->motion.windowID), &window_x, &window_y);
+                mouse_pos.x += window_x;
+                mouse_pos.y += window_y;
+            }
             io.AddMouseSourceEvent(event->motion.which == SDL_TOUCH_MOUSEID ? ImGuiMouseSource_TouchScreen : ImGuiMouseSource_Mouse);
             io.AddMousePosEvent(mouse_pos.x, mouse_pos.y);
             return true;
@@ -332,6 +351,15 @@
             io.SetKeyEventNativeData(key, event->key.keysym.sym, event->key.keysym.scancode, event->key.keysym.scancode); // To support legacy indexing (<1.87 user code). Legacy backend uses SDLK_*** as indices to IsKeyXXX() functions.
             return true;
         }
+        case SDL_EVENT_DISPLAY_ORIENTATION:
+        case SDL_EVENT_DISPLAY_ADDED:
+        case SDL_EVENT_DISPLAY_REMOVED:
+        case SDL_EVENT_DISPLAY_MOVED:
+        case SDL_EVENT_DISPLAY_CONTENT_SCALE_CHANGED:
+        {
+            bd->WantUpdateMonitors = true;
+            return true;
+        }
         case SDL_EVENT_WINDOW_MOUSE_ENTER:
         {
             bd->MouseWindowID = event->window.windowID;
@@ -353,6 +381,20 @@
         case SDL_EVENT_WINDOW_FOCUS_LOST:
             io.AddFocusEvent(false);
             return true;
+        case SDL_EVENT_WINDOW_CLOSE_REQUESTED:
+        case SDL_EVENT_WINDOW_MOVED:
+        case SDL_EVENT_WINDOW_RESIZED:
+            if (ImGuiViewport* viewport = ImGui::FindViewportByPlatformHandle((void*)SDL_GetWindowFromID(event->window.windowID)))
+            {
+                if (event->type == SDL_EVENT_WINDOW_CLOSE_REQUESTED)
+                    viewport->PlatformRequestClose = true;
+                if (event->type == SDL_EVENT_WINDOW_MOVED)
+                    viewport->PlatformRequestMove = true;
+                if (event->type == SDL_EVENT_WINDOW_RESIZED)
+                    viewport->PlatformRequestResize = true;
+                return true;
+            }
+            return true;
         case SDL_EVENT_GAMEPAD_ADDED:
         case SDL_EVENT_GAMEPAD_REMOVED:
         {
@@ -365,7 +407,7 @@
 
 static void ImGui_ImplSDL3_SetupPlatformHandles(ImGuiViewport* viewport, SDL_Window* window)
 {
-    IM_UNUSED(window);
+    viewport->PlatformHandle = window;
     viewport->PlatformHandleRaw = nullptr;
 #if defined(__WIN32__) && !defined(__WINRT__)
     viewport->PlatformHandleRaw = (HWND)SDL_GetProperty(SDL_GetWindowProperties(window), "SDL.window.win32.hwnd", nullptr);
@@ -398,10 +440,21 @@
     io.BackendPlatformName = "imgui_impl_sdl3";
     io.BackendFlags |= ImGuiBackendFlags_HasMouseCursors;           // We can honor GetMouseCursor() values (optional)
     io.BackendFlags |= ImGuiBackendFlags_HasSetMousePos;            // We can honor io.WantSetMousePos requests (optional, rarely used)
+    if (mouse_can_use_global_state)
+        io.BackendFlags |= ImGuiBackendFlags_PlatformHasViewports;  // We can create multi-viewports on the Platform side (optional)
 
     bd->Window = window;
     bd->Renderer = renderer;
+
+    // SDL on Linux/OSX doesn't report events for unfocused windows (see https://github.com/ocornut/imgui/issues/4960)
+    // We will use 'MouseCanReportHoveredViewport' to set 'ImGuiBackendFlags_HasMouseHoveredViewport' dynamically each frame.
     bd->MouseCanUseGlobalState = mouse_can_use_global_state;
+#ifndef __APPLE__
+    bd->MouseCanReportHoveredViewport = bd->MouseCanUseGlobalState;
+#else
+    bd->MouseCanReportHoveredViewport = false;
+#endif
+    bd->WantUpdateMonitors = true;
 
     io.SetClipboardTextFn = ImGui_ImplSDL3_SetClipboardText;
     io.GetClipboardTextFn = ImGui_ImplSDL3_GetClipboardText;
@@ -433,27 +486,34 @@
     // (This is unfortunately a global SDL setting, so enabling it might have a side-effect on your application.
     // It is unlikely to make a difference, but if your app absolutely needs to ignore the initial on-focus click:
     // you can ignore SDL_EVENT_MOUSE_BUTTON_DOWN events coming right after a SDL_WINDOWEVENT_FOCUS_GAINED)
-#ifdef SDL_HINT_MOUSE_FOCUS_CLICKTHROUGH
     SDL_SetHint(SDL_HINT_MOUSE_FOCUS_CLICKTHROUGH, "1");
-#endif
 
     // From 2.0.22: Disable auto-capture, this is preventing drag and drop across multiple windows (see #5710)
-#ifdef SDL_HINT_MOUSE_AUTO_CAPTURE
     SDL_SetHint(SDL_HINT_MOUSE_AUTO_CAPTURE, "0");
-#endif
+
+    // SDL 3.x : see https://github.com/libsdl-org/SDL/issues/6659
+    SDL_SetHint("SDL_BORDERLESS_WINDOWED_STYLE", "0");
+
+    // We need SDL_CaptureMouse(), SDL_GetGlobalMouseState() from SDL 2.0.4+ to support multiple viewports.
+    // We left the call to ImGui_ImplSDL3_InitPlatformInterface() outside of #ifdef to avoid unused-function warnings.
+    if ((io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable) && (io.BackendFlags & ImGuiBackendFlags_PlatformHasViewports))
+        ImGui_ImplSDL3_InitPlatformInterface(window, sdl_gl_context);
 
     return true;
 }
 
 bool ImGui_ImplSDL3_InitForOpenGL(SDL_Window* window, void* sdl_gl_context)
 {
-    IM_UNUSED(sdl_gl_context); // Viewport branch will need this.
     return ImGui_ImplSDL3_Init(window, nullptr, sdl_gl_context);
 }
 
 bool ImGui_ImplSDL3_InitForVulkan(SDL_Window* window)
 {
-    return ImGui_ImplSDL3_Init(window, nullptr, nullptr);
+    if (!ImGui_ImplSDL3_Init(window, nullptr, nullptr))
+        return false;
+    ImGui_ImplSDL3_Data* bd = ImGui_ImplSDL3_GetBackendData();
+    bd->UseVulkan = true;
+    return true;
 }
 
 bool ImGui_ImplSDL3_InitForD3D(SDL_Window* window)
@@ -487,6 +547,8 @@
     IM_ASSERT(bd != nullptr && "No platform backend to shutdown, or already shutdown?");
     ImGuiIO& io = ImGui::GetIO();
 
+    ImGui_ImplSDL3_ShutdownPlatformInterface();
+
     if (bd->ClipboardTextData)
         SDL_free(bd->ClipboardTextData);
     for (ImGuiMouseCursor cursor_n = 0; cursor_n < ImGuiMouseCursor_COUNT; cursor_n++)
@@ -495,10 +557,11 @@
 
     io.BackendPlatformName = nullptr;
     io.BackendPlatformUserData = nullptr;
-    io.BackendFlags &= ~(ImGuiBackendFlags_HasMouseCursors | ImGuiBackendFlags_HasSetMousePos | ImGuiBackendFlags_HasGamepad);
+    io.BackendFlags &= ~(ImGuiBackendFlags_HasMouseCursors | ImGuiBackendFlags_HasSetMousePos | ImGuiBackendFlags_HasGamepad | ImGuiBackendFlags_PlatformHasViewports | ImGuiBackendFlags_HasMouseHoveredViewport);
     IM_DELETE(bd);
 }
 
+// This code is incredibly messy because some of the functions we need for full viewport support are not available in SDL < 2.0.4.
 static void ImGui_ImplSDL3_UpdateMouseData()
 {
     ImGui_ImplSDL3_Data* bd = ImGui_ImplSDL3_GetBackendData();
@@ -509,7 +572,7 @@
     // SDL_CaptureMouse() let the OS know e.g. that our imgui drag outside the SDL window boundaries shouldn't e.g. trigger other operations outside
     SDL_CaptureMouse((bd->MouseButtonsDown != 0) ? SDL_TRUE : SDL_FALSE);
     SDL_Window* focused_window = SDL_GetKeyboardFocus();
-    const bool is_app_focused = (bd->Window == focused_window);
+    const bool is_app_focused = (focused_window && (bd->Window == focused_window || ImGui::FindViewportByPlatformHandle((void*)focused_window)));
 #else
     SDL_Window* focused_window = bd->Window;
     const bool is_app_focused = (SDL_GetWindowFlags(bd->Window) & SDL_WINDOW_INPUT_FOCUS) != 0; // SDL 2.0.3 and non-windowed systems: single-viewport only
@@ -518,19 +581,48 @@
     {
         // (Optional) Set OS mouse position from Dear ImGui if requested (rarely used, only when ImGuiConfigFlags_NavEnableSetMousePos is enabled by user)
         if (io.WantSetMousePos)
-            SDL_WarpMouseInWindow(bd->Window, io.MousePos.x, io.MousePos.y);
+        {
+#if SDL_HAS_CAPTURE_AND_GLOBAL_MOUSE
+            if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+                SDL_WarpMouseGlobal(io.MousePos.x, io.MousePos.y);
+            else
+#endif
+                SDL_WarpMouseInWindow(bd->Window, io.MousePos.x, io.MousePos.y);
+        }
 
         // (Optional) Fallback to provide mouse position when focused (SDL_EVENT_MOUSE_MOTION already provides this when hovered or captured)
         if (bd->MouseCanUseGlobalState && bd->MouseButtonsDown == 0)
         {
             // Single-viewport mode: mouse position in client window coordinates (io.MousePos is (0,0) when the mouse is on the upper-left corner of the app window)
-            float mouse_x_global, mouse_y_global;
+            // Multi-viewport mode: mouse position in OS absolute coordinates (io.MousePos is (0,0) when the mouse is on the upper-left of the primary monitor)
+            float mouse_x, mouse_y;
             int window_x, window_y;
-            SDL_GetGlobalMouseState(&mouse_x_global, &mouse_y_global);
-            SDL_GetWindowPosition(focused_window, &window_x, &window_y);
-            io.AddMousePosEvent(mouse_x_global - window_x, mouse_y_global - window_y);
+            SDL_GetGlobalMouseState(&mouse_x, &mouse_y);
+            if (!(io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable))
+            {
+                SDL_GetWindowPosition(focused_window, &window_x, &window_y);
+                mouse_x -= window_x;
+                mouse_y -= window_y;
+            }
+            io.AddMousePosEvent((float)mouse_x, (float)mouse_y);
         }
     }
+
+    // (Optional) When using multiple viewports: call io.AddMouseViewportEvent() with the viewport the OS mouse cursor is hovering.
+    // If ImGuiBackendFlags_HasMouseHoveredViewport is not set by the backend, Dear imGui will ignore this field and infer the information using its flawed heuristic.
+    // - [!] SDL backend does NOT correctly ignore viewports with the _NoInputs flag.
+    //       Some backend are not able to handle that correctly. If a backend report an hovered viewport that has the _NoInputs flag (e.g. when dragging a window
+    //       for docking, the viewport has the _NoInputs flag in order to allow us to find the viewport under), then Dear ImGui is forced to ignore the value reported
+    //       by the backend, and use its flawed heuristic to guess the viewport behind.
+    // - [X] SDL backend correctly reports this regardless of another viewport behind focused and dragged from (we need this to find a useful drag and drop target).
+    if (io.BackendFlags & ImGuiBackendFlags_HasMouseHoveredViewport)
+    {
+        ImGuiID mouse_viewport_id = 0;
+        if (SDL_Window* sdl_mouse_window = SDL_GetWindowFromID(bd->MouseWindowID))
+            if (ImGuiViewport* mouse_viewport = ImGui::FindViewportByPlatformHandle((void*)sdl_mouse_window))
+                mouse_viewport_id = mouse_viewport->ID;
+        io.AddMouseViewportEvent(mouse_viewport_id);
+    }
 }
 
 static void ImGui_ImplSDL3_UpdateMouseCursor()
@@ -665,6 +757,35 @@
     ImGui_ImplSDL3_UpdateGamepadAnalog(bd, io, ImGuiKey_GamepadRStickDown,  SDL_GAMEPAD_AXIS_RIGHTY, +thumb_dead_zone, +32767);
 }
 
+static void ImGui_ImplSDL3_UpdateMonitors()
+{
+    ImGui_ImplSDL3_Data* bd = ImGui_ImplSDL3_GetBackendData();
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    platform_io.Monitors.resize(0);
+    bd->WantUpdateMonitors = false;
+
+    int display_count;
+    SDL_DisplayID* displays = SDL_GetDisplays(&display_count);
+    for (int n = 0; n < display_count; n++)
+    {
+        // Warning: the validity of monitor DPI information on Windows depends on the application DPI awareness settings, which generally needs to be set in the manifest or at runtime.
+        SDL_DisplayID display_id = displays[n];
+        ImGuiPlatformMonitor monitor;
+        SDL_Rect r;
+        SDL_GetDisplayBounds(display_id, &r);
+        monitor.MainPos = monitor.WorkPos = ImVec2((float)r.x, (float)r.y);
+        monitor.MainSize = monitor.WorkSize = ImVec2((float)r.w, (float)r.h);
+        SDL_GetDisplayUsableBounds(display_id, &r);
+        monitor.WorkPos = ImVec2((float)r.x, (float)r.y);
+        monitor.WorkSize = ImVec2((float)r.w, (float)r.h);
+        // FIXME-VIEWPORT: On MacOS SDL reports actual monitor DPI scale, ignoring OS configuration. We may want to set
+        //  DpiScale to cocoa_window.backingScaleFactor here.
+        monitor.DpiScale = SDL_GetDisplayContentScale(display_id);
+        monitor.PlatformHandle = (void*)(intptr_t)n;
+        platform_io.Monitors.push_back(monitor);
+    }
+}
+
 void ImGui_ImplSDL3_NewFrame()
 {
     ImGui_ImplSDL3_Data* bd = ImGui_ImplSDL3_GetBackendData();
@@ -682,6 +803,10 @@
     if (w > 0 && h > 0)
         io.DisplayFramebufferScale = ImVec2((float)display_w / w, (float)display_h / h);
 
+    // Update monitors
+    if (bd->WantUpdateMonitors)
+        ImGui_ImplSDL3_UpdateMonitors();
+
     // Setup time step (we don't use SDL_GetTicks() because it is using millisecond resolution)
     // (Accept SDL_GetPerformanceCounter() not returning a monotonically increasing value. Happens in VMs and Emscripten, see #6189, #6114, #3644)
     static Uint64 frequency = SDL_GetPerformanceFrequency();
@@ -698,6 +823,13 @@
         io.AddMousePosEvent(-FLT_MAX, -FLT_MAX);
     }
 
+    // Our io.AddMouseViewportEvent() calls will only be valid when not capturing.
+    // Technically speaking testing for 'bd->MouseButtonsDown == 0' would be more rygorous, but testing for payload reduces noise and potential side-effects.
+    if (bd->MouseCanReportHoveredViewport && ImGui::GetDragDropPayload() == nullptr)
+        io.BackendFlags |= ImGuiBackendFlags_HasMouseHoveredViewport;
+    else
+        io.BackendFlags &= ~ImGuiBackendFlags_HasMouseHoveredViewport;
+
     ImGui_ImplSDL3_UpdateMouseData();
     ImGui_ImplSDL3_UpdateMouseCursor();
 
@@ -705,6 +837,232 @@
     ImGui_ImplSDL3_UpdateGamepads();
 }
 
+//--------------------------------------------------------------------------------------------------------
+// MULTI-VIEWPORT / PLATFORM INTERFACE SUPPORT
+// This is an _advanced_ and _optional_ feature, allowing the backend to create and handle multiple viewports simultaneously.
+// If you are new to dear imgui or creating a new binding for dear imgui, it is recommended that you completely ignore this section first..
+//--------------------------------------------------------------------------------------------------------
+
+// Helper structure we store in the void* RendererUserData field of each ImGuiViewport to easily retrieve our backend data.
+struct ImGui_ImplSDL3_ViewportData
+{
+    SDL_Window*     Window;
+    Uint32          WindowID;
+    bool            WindowOwned;
+    SDL_GLContext   GLContext;
+
+    ImGui_ImplSDL3_ViewportData() { Window = nullptr; WindowID = 0; WindowOwned = false; GLContext = nullptr; }
+    ~ImGui_ImplSDL3_ViewportData() { IM_ASSERT(Window == nullptr && GLContext == nullptr); }
+};
+
+static void ImGui_ImplSDL3_CreateWindow(ImGuiViewport* viewport)
+{
+    ImGui_ImplSDL3_Data* bd = ImGui_ImplSDL3_GetBackendData();
+    ImGui_ImplSDL3_ViewportData* vd = IM_NEW(ImGui_ImplSDL3_ViewportData)();
+    viewport->PlatformUserData = vd;
+
+    ImGuiViewport* main_viewport = ImGui::GetMainViewport();
+    ImGui_ImplSDL3_ViewportData* main_viewport_data = (ImGui_ImplSDL3_ViewportData*)main_viewport->PlatformUserData;
+
+    // Share GL resources with main context
+    bool use_opengl = (main_viewport_data->GLContext != nullptr);
+    SDL_GLContext backup_context = nullptr;
+    if (use_opengl)
+    {
+        backup_context = SDL_GL_GetCurrentContext();
+        SDL_GL_SetAttribute(SDL_GL_SHARE_WITH_CURRENT_CONTEXT, 1);
+        SDL_GL_MakeCurrent(main_viewport_data->Window, main_viewport_data->GLContext);
+    }
+
+    Uint32 sdl_flags = 0;
+    sdl_flags |= use_opengl ? SDL_WINDOW_OPENGL : (bd->UseVulkan ? SDL_WINDOW_VULKAN : 0);
+    sdl_flags |= SDL_GetWindowFlags(bd->Window);
+    sdl_flags |= (viewport->Flags & ImGuiViewportFlags_NoDecoration) ? SDL_WINDOW_BORDERLESS : 0;
+    sdl_flags |= (viewport->Flags & ImGuiViewportFlags_NoDecoration) ? 0 : SDL_WINDOW_RESIZABLE;
+#if !defined(_WIN32)
+    // See SDL hack in ImGui_ImplSDL3_ShowWindow().
+    sdl_flags |= (viewport->Flags & ImGuiViewportFlags_NoTaskBarIcon) ? SDL_WINDOW_UTILITY : 0;
+#endif
+    sdl_flags |= (viewport->Flags & ImGuiViewportFlags_TopMost) ? SDL_WINDOW_ALWAYS_ON_TOP : 0;
+    vd->Window = SDL_CreateWindow("No Title Yet", (int)viewport->Size.x, (int)viewport->Size.y, sdl_flags);
+    SDL_SetWindowPosition(vd->Window, (int)viewport->Pos.x, (int)viewport->Pos.y);
+    vd->WindowOwned = true;
+    if (use_opengl)
+    {
+        vd->GLContext = SDL_GL_CreateContext(vd->Window);
+        SDL_GL_SetSwapInterval(0);
+    }
+    if (use_opengl && backup_context)
+        SDL_GL_MakeCurrent(vd->Window, backup_context);
+
+    ImGui_ImplSDL3_SetupPlatformHandles(viewport, vd->Window);
+}
+
+static void ImGui_ImplSDL3_DestroyWindow(ImGuiViewport* viewport)
+{
+    if (ImGui_ImplSDL3_ViewportData* vd = (ImGui_ImplSDL3_ViewportData*)viewport->PlatformUserData)
+    {
+        if (vd->GLContext && vd->WindowOwned)
+            SDL_GL_DeleteContext(vd->GLContext);
+        if (vd->Window && vd->WindowOwned)
+            SDL_DestroyWindow(vd->Window);
+        vd->GLContext = nullptr;
+        vd->Window = nullptr;
+        IM_DELETE(vd);
+    }
+    viewport->PlatformUserData = viewport->PlatformHandle = nullptr;
+}
+
+static void ImGui_ImplSDL3_ShowWindow(ImGuiViewport* viewport)
+{
+    ImGui_ImplSDL3_ViewportData* vd = (ImGui_ImplSDL3_ViewportData*)viewport->PlatformUserData;
+#if defined(_WIN32)
+    HWND hwnd = (HWND)viewport->PlatformHandleRaw;
+
+    // SDL hack: Hide icon from task bar
+    // Note: SDL 3.0.0+ has a SDL_WINDOW_UTILITY flag which is supported under Windows but the way it create the window breaks our seamless transition.
+    if (viewport->Flags & ImGuiViewportFlags_NoTaskBarIcon)
+    {
+        LONG ex_style = ::GetWindowLong(hwnd, GWL_EXSTYLE);
+        ex_style &= ~WS_EX_APPWINDOW;
+        ex_style |= WS_EX_TOOLWINDOW;
+        ::SetWindowLong(hwnd, GWL_EXSTYLE, ex_style);
+    }
+
+    // SDL hack: SDL always activate/focus windows :/
+    if (viewport->Flags & ImGuiViewportFlags_NoFocusOnAppearing)
+    {
+        ::ShowWindow(hwnd, SW_SHOWNA);
+        return;
+    }
+#endif
+
+    SDL_ShowWindow(vd->Window);
+}
+
+static ImVec2 ImGui_ImplSDL3_GetWindowPos(ImGuiViewport* viewport)
+{
+    ImGui_ImplSDL3_ViewportData* vd = (ImGui_ImplSDL3_ViewportData*)viewport->PlatformUserData;
+    int x = 0, y = 0;
+    SDL_GetWindowPosition(vd->Window, &x, &y);
+    return ImVec2((float)x, (float)y);
+}
+
+static void ImGui_ImplSDL3_SetWindowPos(ImGuiViewport* viewport, ImVec2 pos)
+{
+    ImGui_ImplSDL3_ViewportData* vd = (ImGui_ImplSDL3_ViewportData*)viewport->PlatformUserData;
+    SDL_SetWindowPosition(vd->Window, (int)pos.x, (int)pos.y);
+}
+
+static ImVec2 ImGui_ImplSDL3_GetWindowSize(ImGuiViewport* viewport)
+{
+    ImGui_ImplSDL3_ViewportData* vd = (ImGui_ImplSDL3_ViewportData*)viewport->PlatformUserData;
+    int w = 0, h = 0;
+    SDL_GetWindowSize(vd->Window, &w, &h);
+    return ImVec2((float)w, (float)h);
+}
+
+static void ImGui_ImplSDL3_SetWindowSize(ImGuiViewport* viewport, ImVec2 size)
+{
+    ImGui_ImplSDL3_ViewportData* vd = (ImGui_ImplSDL3_ViewportData*)viewport->PlatformUserData;
+    SDL_SetWindowSize(vd->Window, (int)size.x, (int)size.y);
+}
+
+static void ImGui_ImplSDL3_SetWindowTitle(ImGuiViewport* viewport, const char* title)
+{
+    ImGui_ImplSDL3_ViewportData* vd = (ImGui_ImplSDL3_ViewportData*)viewport->PlatformUserData;
+    SDL_SetWindowTitle(vd->Window, title);
+}
+
+static void ImGui_ImplSDL3_SetWindowAlpha(ImGuiViewport* viewport, float alpha)
+{
+    ImGui_ImplSDL3_ViewportData* vd = (ImGui_ImplSDL3_ViewportData*)viewport->PlatformUserData;
+    SDL_SetWindowOpacity(vd->Window, alpha);
+}
+
+static void ImGui_ImplSDL3_SetWindowFocus(ImGuiViewport* viewport)
+{
+    ImGui_ImplSDL3_ViewportData* vd = (ImGui_ImplSDL3_ViewportData*)viewport->PlatformUserData;
+    SDL_RaiseWindow(vd->Window);
+}
+
+static bool ImGui_ImplSDL3_GetWindowFocus(ImGuiViewport* viewport)
+{
+    ImGui_ImplSDL3_ViewportData* vd = (ImGui_ImplSDL3_ViewportData*)viewport->PlatformUserData;
+    return (SDL_GetWindowFlags(vd->Window) & SDL_WINDOW_INPUT_FOCUS) != 0;
+}
+
+static bool ImGui_ImplSDL3_GetWindowMinimized(ImGuiViewport* viewport)
+{
+    ImGui_ImplSDL3_ViewportData* vd = (ImGui_ImplSDL3_ViewportData*)viewport->PlatformUserData;
+    return (SDL_GetWindowFlags(vd->Window) & SDL_WINDOW_MINIMIZED) != 0;
+}
+
+static void ImGui_ImplSDL3_RenderWindow(ImGuiViewport* viewport, void*)
+{
+    ImGui_ImplSDL3_ViewportData* vd = (ImGui_ImplSDL3_ViewportData*)viewport->PlatformUserData;
+    if (vd->GLContext)
+        SDL_GL_MakeCurrent(vd->Window, vd->GLContext);
+}
+
+static void ImGui_ImplSDL3_SwapBuffers(ImGuiViewport* viewport, void*)
+{
+    ImGui_ImplSDL3_ViewportData* vd = (ImGui_ImplSDL3_ViewportData*)viewport->PlatformUserData;
+    if (vd->GLContext)
+    {
+        SDL_GL_MakeCurrent(vd->Window, vd->GLContext);
+        SDL_GL_SwapWindow(vd->Window);
+    }
+}
+
+// Vulkan support (the Vulkan renderer needs to call a platform-side support function to create the surface)
+// SDL is graceful enough to _not_ need <vulkan/vulkan.h> so we can safely include this.
+#include <SDL3/SDL_vulkan.h>
+static int ImGui_ImplSDL3_CreateVkSurface(ImGuiViewport* viewport, ImU64 vk_instance, const void* vk_allocator, ImU64* out_vk_surface)
+{
+    ImGui_ImplSDL3_ViewportData* vd = (ImGui_ImplSDL3_ViewportData*)viewport->PlatformUserData;
+    (void)vk_allocator;
+    SDL_bool ret = SDL_Vulkan_CreateSurface(vd->Window, (VkInstance)vk_instance, (VkAllocationCallbacks*)vk_allocator, (VkSurfaceKHR*)out_vk_surface);
+    return ret ? 0 : 1; // ret ? VK_SUCCESS : VK_NOT_READY
+}
+
+static void ImGui_ImplSDL3_InitPlatformInterface(SDL_Window* window, void* sdl_gl_context)
+{
+    // Register platform interface (will be coupled with a renderer interface)
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    platform_io.Platform_CreateWindow = ImGui_ImplSDL3_CreateWindow;
+    platform_io.Platform_DestroyWindow = ImGui_ImplSDL3_DestroyWindow;
+    platform_io.Platform_ShowWindow = ImGui_ImplSDL3_ShowWindow;
+    platform_io.Platform_SetWindowPos = ImGui_ImplSDL3_SetWindowPos;
+    platform_io.Platform_GetWindowPos = ImGui_ImplSDL3_GetWindowPos;
+    platform_io.Platform_SetWindowSize = ImGui_ImplSDL3_SetWindowSize;
+    platform_io.Platform_GetWindowSize = ImGui_ImplSDL3_GetWindowSize;
+    platform_io.Platform_SetWindowFocus = ImGui_ImplSDL3_SetWindowFocus;
+    platform_io.Platform_GetWindowFocus = ImGui_ImplSDL3_GetWindowFocus;
+    platform_io.Platform_GetWindowMinimized = ImGui_ImplSDL3_GetWindowMinimized;
+    platform_io.Platform_SetWindowTitle = ImGui_ImplSDL3_SetWindowTitle;
+    platform_io.Platform_RenderWindow = ImGui_ImplSDL3_RenderWindow;
+    platform_io.Platform_SwapBuffers = ImGui_ImplSDL3_SwapBuffers;
+    platform_io.Platform_SetWindowAlpha = ImGui_ImplSDL3_SetWindowAlpha;
+    platform_io.Platform_CreateVkSurface = ImGui_ImplSDL3_CreateVkSurface;
+
+    // Register main window handle (which is owned by the main application, not by us)
+    // This is mostly for simplicity and consistency, so that our code (e.g. mouse handling etc.) can use same logic for main and secondary viewports.
+    ImGuiViewport* main_viewport = ImGui::GetMainViewport();
+    ImGui_ImplSDL3_ViewportData* vd = IM_NEW(ImGui_ImplSDL3_ViewportData)();
+    vd->Window = window;
+    vd->WindowID = SDL_GetWindowID(window);
+    vd->WindowOwned = false;
+    vd->GLContext = sdl_gl_context;
+    main_viewport->PlatformUserData = vd;
+    main_viewport->PlatformHandle = vd->Window;
+}
+
+static void ImGui_ImplSDL3_ShutdownPlatformInterface()
+{
+    ImGui::DestroyPlatformWindows();
+}
+
 //-----------------------------------------------------------------------------
 
 #if defined(__clang__)
diff --git a/backends/imgui_impl_sdl3.h b/backends/imgui_impl_sdl3.h
index eafb347..ef5497e 100644
--- a/backends/imgui_impl_sdl3.h
+++ b/backends/imgui_impl_sdl3.h
@@ -9,7 +9,11 @@
 //  [X] Platform: Keyboard support. Since 1.87 we are using the io.AddKeyEvent() function. Pass ImGuiKey values to all key functions e.g. ImGui::IsKeyPressed(ImGuiKey_Space). [Legacy SDL_SCANCODE_* values will also be supported unless IMGUI_DISABLE_OBSOLETE_KEYIO is set]
 //  [X] Platform: Gamepad support. Enabled with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
 //  [X] Platform: Mouse cursor shape and visibility. Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange'.
-// Missing features:
+//  [x] Platform: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable' -> the OS animation effect when window gets created/destroyed is problematic. SDL2 backend doesn't have issue.
+// Issues:
+//  [ ] Platform: Multi-viewport: Minimized windows seems to break mouse wheel events (at least under Windows).
+//  [ ] Platform: Multi-viewport: ParentViewportID not honored, and so io.ConfigViewportsNoDefaultParent has no effect (minor).
+//  [x] Platform: Basic IME support. Position somehow broken in SDL3 + app needs to call 'SDL_SetHint(SDL_HINT_IME_SHOW_UI, "1");' before SDL_CreateWindow()!.
 //  [ ] Platform: IME SUPPORT IS BROKEN IN SDL3 BECAUSE INPUTS GETS SENT TO BOTH APP AND IME + app needs to call 'SDL_SetHint(SDL_HINT_IME_SHOW_UI, "1");' before SDL_CreateWindow()!.
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
diff --git a/backends/imgui_impl_sdlrenderer2.cpp b/backends/imgui_impl_sdlrenderer2.cpp
index 3d538df..a046ed9 100644
--- a/backends/imgui_impl_sdlrenderer2.cpp
+++ b/backends/imgui_impl_sdlrenderer2.cpp
@@ -10,6 +10,8 @@
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'SDL_Texture*' as ImTextureID. Read the FAQ about ImTextureID!
 //  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.
+// Missing features:
+//  [ ] Renderer: Multi-viewport support (multiple windows).
 
 // You can copy and use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
diff --git a/backends/imgui_impl_sdlrenderer2.h b/backends/imgui_impl_sdlrenderer2.h
index aee4052..7c662ca 100644
--- a/backends/imgui_impl_sdlrenderer2.h
+++ b/backends/imgui_impl_sdlrenderer2.h
@@ -10,6 +10,8 @@
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'SDL_Texture*' as ImTextureID. Read the FAQ about ImTextureID!
 //  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.
+// Missing features:
+//  [ ] Renderer: Multi-viewport support (multiple windows).
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
diff --git a/backends/imgui_impl_sdlrenderer3.cpp b/backends/imgui_impl_sdlrenderer3.cpp
index ae75b7c..2d1bf01 100644
--- a/backends/imgui_impl_sdlrenderer3.cpp
+++ b/backends/imgui_impl_sdlrenderer3.cpp
@@ -10,6 +10,8 @@
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'SDL_Texture*' as ImTextureID. Read the FAQ about ImTextureID!
 //  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.
+// Missing features:
+//  [ ] Renderer: Multi-viewport support (multiple windows).
 
 // You can copy and use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
diff --git a/backends/imgui_impl_sdlrenderer3.h b/backends/imgui_impl_sdlrenderer3.h
index 968ec08..a284743 100644
--- a/backends/imgui_impl_sdlrenderer3.h
+++ b/backends/imgui_impl_sdlrenderer3.h
@@ -10,6 +10,8 @@
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'SDL_Texture*' as ImTextureID. Read the FAQ about ImTextureID!
 //  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.
+// Missing features:
+//  [ ] Renderer: Multi-viewport support (multiple windows).
 
 // You can copy and use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
diff --git a/backends/imgui_impl_vulkan.cpp b/backends/imgui_impl_vulkan.cpp
index 3b757eb..036307a 100644
--- a/backends/imgui_impl_vulkan.cpp
+++ b/backends/imgui_impl_vulkan.cpp
@@ -2,8 +2,9 @@
 // This needs to be used along with a Platform Backend (e.g. GLFW, SDL, Win32, custom..)
 
 // Implemented features:
-//  [!] Renderer: User texture binding. Use 'VkDescriptorSet' as ImTextureID. Read the FAQ about ImTextureID! See https://github.com/ocornut/imgui/pull/914 for discussions.
+//  [x] Renderer: User texture binding. Use 'VkDescriptorSet' as ImTextureID. Read the FAQ about ImTextureID! See https://github.com/ocornut/imgui/pull/914 for discussions.
 //  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.
+//  [x] Renderer: Multi-viewport / platform windows. With issues (flickering when creating a new viewport).
 
 // Important: on 32-bit systems, user texture binding is only supported if your imconfig file has '#define ImTextureID ImU64'.
 // This is because we need ImTextureID to carry a 64-bit value and by default ImTextureID is defined as void*.
@@ -33,6 +34,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2024-XX-XX: Platform: Added support for multiple windows via the ImGuiPlatformIO interface.
 //  2024-04-19: Vulkan: Added convenience support for Volk via IMGUI_IMPL_VULKAN_USE_VOLK define (you can also use IMGUI_IMPL_VULKAN_NO_PROTOTYPES + wrap Volk via ImGui_ImplVulkan_LoadFunctions().)
 //  2024-02-14: *BREAKING CHANGE*: Moved RenderPass parameter from ImGui_ImplVulkan_Init() function to ImGui_ImplVulkan_InitInfo structure. Not required when using dynamic rendering.
 //  2024-02-12: *BREAKING CHANGE*: Dynamic rendering now require filling PipelineRenderingCreateInfo structure.
@@ -104,6 +106,7 @@
 void ImGui_ImplVulkan_DestroyWindowRenderBuffers(VkDevice device, ImGui_ImplVulkan_WindowRenderBuffers* buffers, const VkAllocationCallbacks* allocator);
 void ImGui_ImplVulkanH_DestroyFrame(VkDevice device, ImGui_ImplVulkanH_Frame* fd, const VkAllocationCallbacks* allocator);
 void ImGui_ImplVulkanH_DestroyFrameSemaphores(VkDevice device, ImGui_ImplVulkanH_FrameSemaphores* fsd, const VkAllocationCallbacks* allocator);
+void ImGui_ImplVulkanH_DestroyAllViewportsRenderBuffers(VkDevice device, const VkAllocationCallbacks* allocator);
 void ImGui_ImplVulkanH_CreateWindowSwapChain(VkPhysicalDevice physical_device, VkDevice device, ImGui_ImplVulkanH_Window* wd, const VkAllocationCallbacks* allocator, int w, int h, uint32_t min_image_count);
 void ImGui_ImplVulkanH_CreateWindowCommandBuffers(VkPhysicalDevice physical_device, VkDevice device, ImGui_ImplVulkanH_Window* wd, uint32_t queue_family, const VkAllocationCallbacks* allocator);
 
@@ -120,15 +123,18 @@
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkAllocateCommandBuffers) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkAllocateDescriptorSets) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkAllocateMemory) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkAcquireNextImageKHR) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkBeginCommandBuffer) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkBindBufferMemory) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkBindImageMemory) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdBeginRenderPass) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdBindDescriptorSets) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdBindIndexBuffer) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdBindPipeline) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdBindVertexBuffers) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdCopyBufferToImage) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdDrawIndexed) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdEndRenderPass) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdPipelineBarrier) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdPushConstants) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdSetScissor) \
@@ -174,13 +180,17 @@
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkGetPhysicalDeviceSurfaceCapabilitiesKHR) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkGetPhysicalDeviceSurfaceFormatsKHR) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkGetPhysicalDeviceSurfacePresentModesKHR) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkGetPhysicalDeviceSurfaceSupportKHR) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkGetSwapchainImagesKHR) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkMapMemory) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkQueuePresentKHR) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkQueueSubmit) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkQueueWaitIdle) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkResetCommandPool) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkResetFences) \
     IMGUI_VULKAN_FUNC_MAP_MACRO(vkUnmapMemory) \
-    IMGUI_VULKAN_FUNC_MAP_MACRO(vkUpdateDescriptorSets)
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkUpdateDescriptorSets) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkWaitForFences)
 
 // Define function pointers
 #define IMGUI_VULKAN_FUNC_DEF(func) static PFN_##func func;
@@ -214,6 +224,19 @@
     ImGui_ImplVulkan_FrameRenderBuffers* FrameRenderBuffers;
 };
 
+// For multi-viewport support:
+// Helper structure we store in the void* RendererUserData field of each ImGuiViewport to easily retrieve our backend data.
+struct ImGui_ImplVulkan_ViewportData
+{
+    ImGui_ImplVulkanH_Window                Window;                 // Used by secondary viewports only
+    ImGui_ImplVulkan_WindowRenderBuffers    RenderBuffers;          // Used by all viewports
+    bool                                    WindowOwned;
+    bool                                    SwapChainNeedRebuild;   // Flag when viewport swapchain resized in the middle of processing a frame
+
+    ImGui_ImplVulkan_ViewportData()         { WindowOwned = SwapChainNeedRebuild = false; memset(&RenderBuffers, 0, sizeof(RenderBuffers)); }
+    ~ImGui_ImplVulkan_ViewportData()        { }
+};
+
 // Vulkan data
 struct ImGui_ImplVulkan_Data
 {
@@ -222,7 +245,8 @@
     VkPipelineCreateFlags       PipelineCreateFlags;
     VkDescriptorSetLayout       DescriptorSetLayout;
     VkPipelineLayout            PipelineLayout;
-    VkPipeline                  Pipeline;
+    VkPipeline                  Pipeline;               // pipeline for main render pass (created by app)
+    VkPipeline                  PipelineForViewports;   // pipeline for secondary viewports (created by backend)
     VkShaderModule              ShaderModuleVert;
     VkShaderModule              ShaderModuleFrag;
 
@@ -249,6 +273,10 @@
 // SHADERS
 //-----------------------------------------------------------------------------
 
+// Forward Declarations
+static void ImGui_ImplVulkan_InitPlatformInterface();
+static void ImGui_ImplVulkan_ShutdownPlatformInterface();
+
 // backends/vulkan/glsl_shader.vert, compiled with:
 // # glslangValidator -V -x -o glsl_shader.vert.u32 glsl_shader.vert
 /*
@@ -486,8 +514,10 @@
     if (pipeline == VK_NULL_HANDLE)
         pipeline = bd->Pipeline;
 
-    // Allocate array to store enough vertex/index buffers
-    ImGui_ImplVulkan_WindowRenderBuffers* wrb = &bd->MainWindowRenderBuffers;
+    // Allocate array to store enough vertex/index buffers. Each unique viewport gets its own storage.
+    ImGui_ImplVulkan_ViewportData* viewport_renderer_data = (ImGui_ImplVulkan_ViewportData*)draw_data->OwnerViewport->RendererUserData;
+    IM_ASSERT(viewport_renderer_data != nullptr);
+    ImGui_ImplVulkan_WindowRenderBuffers* wrb = &viewport_renderer_data->RenderBuffers;
     if (wrb->FrameRenderBuffers == nullptr)
     {
         wrb->Index = 0;
@@ -1032,7 +1062,7 @@
 {
     ImGui_ImplVulkan_Data* bd = ImGui_ImplVulkan_GetBackendData();
     ImGui_ImplVulkan_InitInfo* v = &bd->VulkanInitInfo;
-    ImGui_ImplVulkan_DestroyWindowRenderBuffers(v->Device, &bd->MainWindowRenderBuffers, v->Allocator);
+    ImGui_ImplVulkanH_DestroyAllViewportsRenderBuffers(v->Device, v->Allocator);
     ImGui_ImplVulkan_DestroyFontsTexture();
 
     if (bd->FontCommandBuffer)    { vkFreeCommandBuffers(v->Device, bd->FontCommandPool, 1, &bd->FontCommandBuffer); bd->FontCommandBuffer = VK_NULL_HANDLE; }
@@ -1043,6 +1073,7 @@
     if (bd->DescriptorSetLayout)  { vkDestroyDescriptorSetLayout(v->Device, bd->DescriptorSetLayout, v->Allocator); bd->DescriptorSetLayout = VK_NULL_HANDLE; }
     if (bd->PipelineLayout)       { vkDestroyPipelineLayout(v->Device, bd->PipelineLayout, v->Allocator); bd->PipelineLayout = VK_NULL_HANDLE; }
     if (bd->Pipeline)             { vkDestroyPipeline(v->Device, bd->Pipeline, v->Allocator); bd->Pipeline = VK_NULL_HANDLE; }
+    if (bd->PipelineForViewports) { vkDestroyPipeline(v->Device, bd->PipelineForViewports, v->Allocator); bd->PipelineForViewports = VK_NULL_HANDLE; }
 }
 
 bool    ImGui_ImplVulkan_LoadFunctions(PFN_vkVoidFunction(*loader_func)(const char* function_name, void* user_data), void* user_data)
@@ -1100,6 +1131,7 @@
     io.BackendRendererUserData = (void*)bd;
     io.BackendRendererName = "imgui_impl_vulkan";
     io.BackendFlags |= ImGuiBackendFlags_RendererHasVtxOffset;  // We can honor the ImDrawCmd::VtxOffset field, allowing for large meshes.
+    io.BackendFlags |= ImGuiBackendFlags_RendererHasViewports;  // We can create multi-viewports on the Renderer side (optional)
 
     IM_ASSERT(info->Instance != VK_NULL_HANDLE);
     IM_ASSERT(info->PhysicalDevice != VK_NULL_HANDLE);
@@ -1115,6 +1147,13 @@
 
     ImGui_ImplVulkan_CreateDeviceObjects();
 
+    // Our render function expect RendererUserData to be storing the window render buffer we need (for the main viewport we won't use ->Window)
+    ImGuiViewport* main_viewport = ImGui::GetMainViewport();
+    main_viewport->RendererUserData = IM_NEW(ImGui_ImplVulkan_ViewportData)();
+
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        ImGui_ImplVulkan_InitPlatformInterface();
+
     return true;
 }
 
@@ -1124,10 +1163,21 @@
     IM_ASSERT(bd != nullptr && "No renderer backend to shutdown, or already shutdown?");
     ImGuiIO& io = ImGui::GetIO();
 
+    // First destroy objects in all viewports
     ImGui_ImplVulkan_DestroyDeviceObjects();
+
+    // Manually delete main viewport render data in-case we haven't initialized for viewports
+    ImGuiViewport* main_viewport = ImGui::GetMainViewport();
+    if (ImGui_ImplVulkan_ViewportData* vd = (ImGui_ImplVulkan_ViewportData*)main_viewport->RendererUserData)
+        IM_DELETE(vd);
+    main_viewport->RendererUserData = nullptr;
+
+    // Clean up windows
+    ImGui_ImplVulkan_ShutdownPlatformInterface();
+
     io.BackendRendererName = nullptr;
     io.BackendRendererUserData = nullptr;
-    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;
+    io.BackendFlags &= ~(ImGuiBackendFlags_RendererHasVtxOffset | ImGuiBackendFlags_RendererHasViewports);
     IM_DELETE(bd);
 }
 
@@ -1147,10 +1197,12 @@
     if (bd->VulkanInitInfo.MinImageCount == min_image_count)
         return;
 
+    IM_ASSERT(0); // FIXME-VIEWPORT: Unsupported. Need to recreate all swap chains!
     ImGui_ImplVulkan_InitInfo* v = &bd->VulkanInitInfo;
     VkResult err = vkDeviceWaitIdle(v->Device);
     check_vk_result(err);
-    ImGui_ImplVulkan_DestroyWindowRenderBuffers(v->Device, &bd->MainWindowRenderBuffers, v->Allocator);
+    ImGui_ImplVulkanH_DestroyAllViewportsRenderBuffers(v->Device, v->Allocator);
+
     bd->VulkanInitInfo.MinImageCount = min_image_count;
 }
 
@@ -1385,8 +1437,6 @@
     wd->ImageCount = 0;
     if (wd->RenderPass)
         vkDestroyRenderPass(device, wd->RenderPass, allocator);
-    if (wd->Pipeline)
-        vkDestroyPipeline(device, wd->Pipeline, allocator);
 
     // If min image count was not specified, request different count of images dependent on selected present mode
     if (min_image_count == 0)
@@ -1539,6 +1589,7 @@
     IM_ASSERT(g_FunctionsLoaded && "Need to call ImGui_ImplVulkan_LoadFunctions() if IMGUI_IMPL_VULKAN_NO_PROTOTYPES or VK_NO_PROTOTYPES are set!");
     (void)instance;
     ImGui_ImplVulkanH_CreateWindowSwapChain(physical_device, device, wd, allocator, width, height, min_image_count);
+    //ImGui_ImplVulkan_CreatePipeline(device, allocator, VK_NULL_HANDLE, wd->RenderPass, VK_SAMPLE_COUNT_1_BIT, &wd->Pipeline, g_VulkanInitInfo.Subpass);
     ImGui_ImplVulkanH_CreateWindowCommandBuffers(physical_device, device, wd, queue_family, allocator);
 }
 
@@ -1555,7 +1606,6 @@
     IM_FREE(wd->FrameSemaphores);
     wd->Frames = nullptr;
     wd->FrameSemaphores = nullptr;
-    vkDestroyPipeline(device, wd->Pipeline, allocator);
     vkDestroyRenderPass(device, wd->RenderPass, allocator);
     vkDestroySwapchainKHR(device, wd->Swapchain, allocator);
     vkDestroySurfaceKHR(instance, wd->Surface, allocator);
@@ -1583,6 +1633,293 @@
     fsd->ImageAcquiredSemaphore = fsd->RenderCompleteSemaphore = VK_NULL_HANDLE;
 }
 
+void ImGui_ImplVulkanH_DestroyAllViewportsRenderBuffers(VkDevice device, const VkAllocationCallbacks* allocator)
+{
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    for (int n = 0; n < platform_io.Viewports.Size; n++)
+        if (ImGui_ImplVulkan_ViewportData* vd = (ImGui_ImplVulkan_ViewportData*)platform_io.Viewports[n]->RendererUserData)
+            ImGui_ImplVulkan_DestroyWindowRenderBuffers(device, &vd->RenderBuffers, allocator);
+}
+
+//--------------------------------------------------------------------------------------------------------
+// MULTI-VIEWPORT / PLATFORM INTERFACE SUPPORT
+// This is an _advanced_ and _optional_ feature, allowing the backend to create and handle multiple viewports simultaneously.
+// If you are new to dear imgui or creating a new binding for dear imgui, it is recommended that you completely ignore this section first..
+//--------------------------------------------------------------------------------------------------------
+
+static void ImGui_ImplVulkan_CreateWindow(ImGuiViewport* viewport)
+{
+    ImGui_ImplVulkan_Data* bd = ImGui_ImplVulkan_GetBackendData();
+    ImGui_ImplVulkan_ViewportData* vd = IM_NEW(ImGui_ImplVulkan_ViewportData)();
+    viewport->RendererUserData = vd;
+    ImGui_ImplVulkanH_Window* wd = &vd->Window;
+    ImGui_ImplVulkan_InitInfo* v = &bd->VulkanInitInfo;
+
+    // Create surface
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    VkResult err = (VkResult)platform_io.Platform_CreateVkSurface(viewport, (ImU64)v->Instance, (const void*)v->Allocator, (ImU64*)&wd->Surface);
+    check_vk_result(err);
+
+    // Check for WSI support
+    VkBool32 res;
+    vkGetPhysicalDeviceSurfaceSupportKHR(v->PhysicalDevice, v->QueueFamily, wd->Surface, &res);
+    if (res != VK_TRUE)
+    {
+        IM_ASSERT(0); // Error: no WSI support on physical device
+        return;
+    }
+
+    // Select Surface Format
+    ImVector<VkFormat> requestSurfaceImageFormats;
+#ifdef IMGUI_IMPL_VULKAN_HAS_DYNAMIC_RENDERING
+    for (uint32_t n = 0; n < v->PipelineRenderingCreateInfo.colorAttachmentCount; n++)
+        requestSurfaceImageFormats.push_back(v->PipelineRenderingCreateInfo.pColorAttachmentFormats[n]);
+#endif
+    const VkFormat defaultFormats[] = { VK_FORMAT_B8G8R8A8_UNORM, VK_FORMAT_R8G8B8A8_UNORM, VK_FORMAT_B8G8R8_UNORM, VK_FORMAT_R8G8B8_UNORM };
+    for (VkFormat format : defaultFormats)
+        requestSurfaceImageFormats.push_back(format);
+
+    const VkColorSpaceKHR requestSurfaceColorSpace = VK_COLORSPACE_SRGB_NONLINEAR_KHR;
+    wd->SurfaceFormat = ImGui_ImplVulkanH_SelectSurfaceFormat(v->PhysicalDevice, wd->Surface, requestSurfaceImageFormats.Data, (size_t)requestSurfaceImageFormats.Size, requestSurfaceColorSpace);
+
+    // Select Present Mode
+    // FIXME-VULKAN: Even thought mailbox seems to get us maximum framerate with a single window, it halves framerate with a second window etc. (w/ Nvidia and SDK 1.82.1)
+    VkPresentModeKHR present_modes[] = { VK_PRESENT_MODE_MAILBOX_KHR, VK_PRESENT_MODE_IMMEDIATE_KHR, VK_PRESENT_MODE_FIFO_KHR };
+    wd->PresentMode = ImGui_ImplVulkanH_SelectPresentMode(v->PhysicalDevice, wd->Surface, &present_modes[0], IM_ARRAYSIZE(present_modes));
+    //printf("[vulkan] Secondary window selected PresentMode = %d\n", wd->PresentMode);
+
+    // Create SwapChain, RenderPass, Framebuffer, etc.
+    wd->ClearEnable = (viewport->Flags & ImGuiViewportFlags_NoRendererClear) ? false : true;
+    wd->UseDynamicRendering = v->UseDynamicRendering;
+    ImGui_ImplVulkanH_CreateOrResizeWindow(v->Instance, v->PhysicalDevice, v->Device, wd, v->QueueFamily, v->Allocator, (int)viewport->Size.x, (int)viewport->Size.y, v->MinImageCount);
+    vd->WindowOwned = true;
+
+    // Create pipeline (shared by all secondary viewports)
+    if (bd->PipelineForViewports == VK_NULL_HANDLE)
+        ImGui_ImplVulkan_CreatePipeline(v->Device, v->Allocator, VK_NULL_HANDLE, wd->RenderPass, VK_SAMPLE_COUNT_1_BIT, &bd->PipelineForViewports, 0);
+}
+
+static void ImGui_ImplVulkan_DestroyWindow(ImGuiViewport* viewport)
+{
+    // The main viewport (owned by the application) will always have RendererUserData == 0 since we didn't create the data for it.
+    ImGui_ImplVulkan_Data* bd = ImGui_ImplVulkan_GetBackendData();
+    if (ImGui_ImplVulkan_ViewportData* vd = (ImGui_ImplVulkan_ViewportData*)viewport->RendererUserData)
+    {
+        ImGui_ImplVulkan_InitInfo* v = &bd->VulkanInitInfo;
+        if (vd->WindowOwned)
+            ImGui_ImplVulkanH_DestroyWindow(v->Instance, v->Device, &vd->Window, v->Allocator);
+        ImGui_ImplVulkan_DestroyWindowRenderBuffers(v->Device, &vd->RenderBuffers, v->Allocator);
+        IM_DELETE(vd);
+    }
+    viewport->RendererUserData = nullptr;
+}
+
+static void ImGui_ImplVulkan_SetWindowSize(ImGuiViewport* viewport, ImVec2 size)
+{
+    ImGui_ImplVulkan_Data* bd = ImGui_ImplVulkan_GetBackendData();
+    ImGui_ImplVulkan_ViewportData* vd = (ImGui_ImplVulkan_ViewportData*)viewport->RendererUserData;
+    if (vd == nullptr) // This is nullptr for the main viewport (which is left to the user/app to handle)
+        return;
+    ImGui_ImplVulkan_InitInfo* v = &bd->VulkanInitInfo;
+    vd->Window.ClearEnable = (viewport->Flags & ImGuiViewportFlags_NoRendererClear) ? false : true;
+    ImGui_ImplVulkanH_CreateOrResizeWindow(v->Instance, v->PhysicalDevice, v->Device, &vd->Window, v->QueueFamily, v->Allocator, (int)size.x, (int)size.y, v->MinImageCount);
+}
+
+static void ImGui_ImplVulkan_RenderWindow(ImGuiViewport* viewport, void*)
+{
+    ImGui_ImplVulkan_Data* bd = ImGui_ImplVulkan_GetBackendData();
+    ImGui_ImplVulkan_ViewportData* vd = (ImGui_ImplVulkan_ViewportData*)viewport->RendererUserData;
+    ImGui_ImplVulkanH_Window* wd = &vd->Window;
+    ImGui_ImplVulkan_InitInfo* v = &bd->VulkanInitInfo;
+    VkResult err;
+
+    if (vd->SwapChainNeedRebuild)
+    {
+        ImGui_ImplVulkanH_CreateOrResizeWindow(v->Instance, v->PhysicalDevice, v->Device, wd, v->QueueFamily, v->Allocator, (int)viewport->Size.x, (int)viewport->Size.y, v->MinImageCount);
+        vd->SwapChainNeedRebuild = false;
+    }
+
+    ImGui_ImplVulkanH_Frame* fd = &wd->Frames[wd->FrameIndex];
+    ImGui_ImplVulkanH_FrameSemaphores* fsd = &wd->FrameSemaphores[wd->SemaphoreIndex];
+    {
+        {
+            err = vkAcquireNextImageKHR(v->Device, wd->Swapchain, UINT64_MAX, fsd->ImageAcquiredSemaphore, VK_NULL_HANDLE, &wd->FrameIndex);
+            if (err == VK_ERROR_OUT_OF_DATE_KHR)
+            {
+                // Since we are not going to swap this frame anyway, it's ok that recreation happens on next frame.
+                vd->SwapChainNeedRebuild = true;
+                return;
+            }
+            check_vk_result(err);
+            fd = &wd->Frames[wd->FrameIndex];
+        }
+        for (;;)
+        {
+            err = vkWaitForFences(v->Device, 1, &fd->Fence, VK_TRUE, 100);
+            if (err == VK_SUCCESS) break;
+            if (err == VK_TIMEOUT) continue;
+            check_vk_result(err);
+        }
+        {
+            err = vkResetCommandPool(v->Device, fd->CommandPool, 0);
+            check_vk_result(err);
+            VkCommandBufferBeginInfo info = {};
+            info.sType = VK_STRUCTURE_TYPE_COMMAND_BUFFER_BEGIN_INFO;
+            info.flags |= VK_COMMAND_BUFFER_USAGE_ONE_TIME_SUBMIT_BIT;
+            err = vkBeginCommandBuffer(fd->CommandBuffer, &info);
+            check_vk_result(err);
+        }
+        {
+            ImVec4 clear_color = ImVec4(0.0f, 0.0f, 0.0f, 1.0f);
+            memcpy(&wd->ClearValue.color.float32[0], &clear_color, 4 * sizeof(float));
+        }
+#ifdef IMGUI_IMPL_VULKAN_HAS_DYNAMIC_RENDERING
+        if (v->UseDynamicRendering)
+        {
+            // Transition swapchain image to a layout suitable for drawing.
+            VkImageMemoryBarrier barrier = {};
+            barrier.sType = VK_STRUCTURE_TYPE_IMAGE_MEMORY_BARRIER;
+            barrier.dstAccessMask = VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT;
+            barrier.oldLayout = VK_IMAGE_LAYOUT_UNDEFINED;
+            barrier.newLayout = VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL;
+            barrier.image = fd->Backbuffer;
+            barrier.subresourceRange.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
+            barrier.subresourceRange.levelCount = 1;
+            barrier.subresourceRange.layerCount = 1;
+            vkCmdPipelineBarrier(fd->CommandBuffer, VK_PIPELINE_STAGE_TOP_OF_PIPE_BIT, VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT, 0, 0, nullptr, 0, nullptr, 1, &barrier);
+
+            VkRenderingAttachmentInfo attachmentInfo = {};
+            attachmentInfo.sType = VK_STRUCTURE_TYPE_RENDERING_ATTACHMENT_INFO_KHR;
+            attachmentInfo.imageView = fd->BackbufferView;
+            attachmentInfo.imageLayout = VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL;
+            attachmentInfo.resolveMode = VK_RESOLVE_MODE_NONE;
+            attachmentInfo.loadOp = VK_ATTACHMENT_LOAD_OP_CLEAR;
+            attachmentInfo.storeOp = VK_ATTACHMENT_STORE_OP_STORE;
+            attachmentInfo.clearValue = wd->ClearValue;
+
+            VkRenderingInfo renderingInfo = {};
+            renderingInfo.sType = VK_STRUCTURE_TYPE_RENDERING_INFO_KHR;
+            renderingInfo.renderArea.extent.width = wd->Width;
+            renderingInfo.renderArea.extent.height = wd->Height;
+            renderingInfo.layerCount = 1;
+            renderingInfo.viewMask = 0;
+            renderingInfo.colorAttachmentCount = 1;
+            renderingInfo.pColorAttachments = &attachmentInfo;
+
+            ImGuiImplVulkanFuncs_vkCmdBeginRenderingKHR(fd->CommandBuffer, &renderingInfo);
+        }
+        else
+#endif
+        {
+            VkRenderPassBeginInfo info = {};
+            info.sType = VK_STRUCTURE_TYPE_RENDER_PASS_BEGIN_INFO;
+            info.renderPass = wd->RenderPass;
+            info.framebuffer = fd->Framebuffer;
+            info.renderArea.extent.width = wd->Width;
+            info.renderArea.extent.height = wd->Height;
+            info.clearValueCount = (viewport->Flags & ImGuiViewportFlags_NoRendererClear) ? 0 : 1;
+            info.pClearValues = (viewport->Flags & ImGuiViewportFlags_NoRendererClear) ? nullptr : &wd->ClearValue;
+            vkCmdBeginRenderPass(fd->CommandBuffer, &info, VK_SUBPASS_CONTENTS_INLINE);
+        }
+    }
+
+    ImGui_ImplVulkan_RenderDrawData(viewport->DrawData, fd->CommandBuffer, bd->PipelineForViewports);
+
+    {
+#ifdef IMGUI_IMPL_VULKAN_HAS_DYNAMIC_RENDERING
+        if (v->UseDynamicRendering)
+        {
+            ImGuiImplVulkanFuncs_vkCmdEndRenderingKHR(fd->CommandBuffer);
+
+            // Transition image to a layout suitable for presentation
+            VkImageMemoryBarrier barrier = {};
+            barrier.sType = VK_STRUCTURE_TYPE_IMAGE_MEMORY_BARRIER;
+            barrier.srcAccessMask = VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT;
+            barrier.oldLayout = VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL;
+            barrier.newLayout = VK_IMAGE_LAYOUT_PRESENT_SRC_KHR;
+            barrier.image = fd->Backbuffer;
+            barrier.subresourceRange.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
+            barrier.subresourceRange.levelCount = 1;
+            barrier.subresourceRange.layerCount = 1;
+            vkCmdPipelineBarrier(fd->CommandBuffer, VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT, VK_PIPELINE_STAGE_BOTTOM_OF_PIPE_BIT, 0, 0, nullptr, 0, nullptr, 1, &barrier);
+        }
+        else
+#endif
+        {
+            vkCmdEndRenderPass(fd->CommandBuffer);
+        }
+        {
+            VkPipelineStageFlags wait_stage = VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT;
+            VkSubmitInfo info = {};
+            info.sType = VK_STRUCTURE_TYPE_SUBMIT_INFO;
+            info.waitSemaphoreCount = 1;
+            info.pWaitSemaphores = &fsd->ImageAcquiredSemaphore;
+            info.pWaitDstStageMask = &wait_stage;
+            info.commandBufferCount = 1;
+            info.pCommandBuffers = &fd->CommandBuffer;
+            info.signalSemaphoreCount = 1;
+            info.pSignalSemaphores = &fsd->RenderCompleteSemaphore;
+
+            err = vkEndCommandBuffer(fd->CommandBuffer);
+            check_vk_result(err);
+            err = vkResetFences(v->Device, 1, &fd->Fence);
+            check_vk_result(err);
+            err = vkQueueSubmit(v->Queue, 1, &info, fd->Fence);
+            check_vk_result(err);
+        }
+    }
+}
+
+static void ImGui_ImplVulkan_SwapBuffers(ImGuiViewport* viewport, void*)
+{
+    ImGui_ImplVulkan_Data* bd = ImGui_ImplVulkan_GetBackendData();
+    ImGui_ImplVulkan_ViewportData* vd = (ImGui_ImplVulkan_ViewportData*)viewport->RendererUserData;
+    ImGui_ImplVulkanH_Window* wd = &vd->Window;
+    ImGui_ImplVulkan_InitInfo* v = &bd->VulkanInitInfo;
+
+    if (vd->SwapChainNeedRebuild) // Frame data became invalid in the middle of rendering
+        return;
+
+    VkResult err;
+    uint32_t present_index = wd->FrameIndex;
+
+    ImGui_ImplVulkanH_FrameSemaphores* fsd = &wd->FrameSemaphores[wd->SemaphoreIndex];
+    VkPresentInfoKHR info = {};
+    info.sType = VK_STRUCTURE_TYPE_PRESENT_INFO_KHR;
+    info.waitSemaphoreCount = 1;
+    info.pWaitSemaphores = &fsd->RenderCompleteSemaphore;
+    info.swapchainCount = 1;
+    info.pSwapchains = &wd->Swapchain;
+    info.pImageIndices = &present_index;
+    err = vkQueuePresentKHR(v->Queue, &info);
+    if (err == VK_ERROR_OUT_OF_DATE_KHR || err == VK_SUBOPTIMAL_KHR)
+    {
+        vd->SwapChainNeedRebuild = true;
+        return;
+    }
+    check_vk_result(err);
+
+    wd->FrameIndex = (wd->FrameIndex + 1) % wd->ImageCount;             // This is for the next vkWaitForFences()
+    wd->SemaphoreIndex = (wd->SemaphoreIndex + 1) % wd->SemaphoreCount; // Now we can use the next set of semaphores
+}
+
+void ImGui_ImplVulkan_InitPlatformInterface()
+{
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    if (ImGui::GetIO().ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        IM_ASSERT(platform_io.Platform_CreateVkSurface != nullptr && "Platform needs to setup the CreateVkSurface handler.");
+    platform_io.Renderer_CreateWindow = ImGui_ImplVulkan_CreateWindow;
+    platform_io.Renderer_DestroyWindow = ImGui_ImplVulkan_DestroyWindow;
+    platform_io.Renderer_SetWindowSize = ImGui_ImplVulkan_SetWindowSize;
+    platform_io.Renderer_RenderWindow = ImGui_ImplVulkan_RenderWindow;
+    platform_io.Renderer_SwapBuffers = ImGui_ImplVulkan_SwapBuffers;
+}
+
+void ImGui_ImplVulkan_ShutdownPlatformInterface()
+{
+    ImGui::DestroyPlatformWindows();
+}
+
 //-----------------------------------------------------------------------------
 
 #endif // #ifndef IMGUI_DISABLE
diff --git a/backends/imgui_impl_vulkan.h b/backends/imgui_impl_vulkan.h
index c174a6c..2bb32c8 100644
--- a/backends/imgui_impl_vulkan.h
+++ b/backends/imgui_impl_vulkan.h
@@ -2,8 +2,9 @@
 // This needs to be used along with a Platform Backend (e.g. GLFW, SDL, Win32, custom..)
 
 // Implemented features:
-//  [!] Renderer: User texture binding. Use 'VkDescriptorSet' as ImTextureID. Read the FAQ about ImTextureID! See https://github.com/ocornut/imgui/pull/914 for discussions.
+//  [x] Renderer: User texture binding. Use 'VkDescriptorSet' as ImTextureID. Read the FAQ about ImTextureID! See https://github.com/ocornut/imgui/pull/914 for discussions.
 //  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.
+//  [x] Renderer: Multi-viewport / platform windows. With issues (flickering when creating a new viewport).
 
 // Important: on 32-bit systems, user texture binding is only supported if your imconfig file has '#define ImTextureID ImU64'.
 // See imgui_impl_vulkan.cpp file for details.
@@ -137,8 +138,8 @@
 struct ImGui_ImplVulkanH_Window;
 
 // Helpers
-IMGUI_IMPL_API void                 ImGui_ImplVulkanH_CreateOrResizeWindow(VkInstance instance, VkPhysicalDevice physical_device, VkDevice device, ImGui_ImplVulkanH_Window* wnd, uint32_t queue_family, const VkAllocationCallbacks* allocator, int w, int h, uint32_t min_image_count);
-IMGUI_IMPL_API void                 ImGui_ImplVulkanH_DestroyWindow(VkInstance instance, VkDevice device, ImGui_ImplVulkanH_Window* wnd, const VkAllocationCallbacks* allocator);
+IMGUI_IMPL_API void                 ImGui_ImplVulkanH_CreateOrResizeWindow(VkInstance instance, VkPhysicalDevice physical_device, VkDevice device, ImGui_ImplVulkanH_Window* wd, uint32_t queue_family, const VkAllocationCallbacks* allocator, int w, int h, uint32_t min_image_count);
+IMGUI_IMPL_API void                 ImGui_ImplVulkanH_DestroyWindow(VkInstance instance, VkDevice device, ImGui_ImplVulkanH_Window* wd, const VkAllocationCallbacks* allocator);
 IMGUI_IMPL_API VkSurfaceFormatKHR   ImGui_ImplVulkanH_SelectSurfaceFormat(VkPhysicalDevice physical_device, VkSurfaceKHR surface, const VkFormat* request_formats, int request_formats_count, VkColorSpaceKHR request_color_space);
 IMGUI_IMPL_API VkPresentModeKHR     ImGui_ImplVulkanH_SelectPresentMode(VkPhysicalDevice physical_device, VkSurfaceKHR surface, const VkPresentModeKHR* request_modes, int request_modes_count);
 IMGUI_IMPL_API int                  ImGui_ImplVulkanH_GetMinImageCountFromPresentMode(VkPresentModeKHR present_mode);
@@ -173,7 +174,6 @@
     VkSurfaceFormatKHR  SurfaceFormat;
     VkPresentModeKHR    PresentMode;
     VkRenderPass        RenderPass;
-    VkPipeline          Pipeline;               // The window pipeline may uses a different VkRenderPass than the one passed in ImGui_ImplVulkan_InitInfo
     bool                UseDynamicRendering;
     bool                ClearEnable;
     VkClearValue        ClearValue;
diff --git a/backends/imgui_impl_wgpu.cpp b/backends/imgui_impl_wgpu.cpp
index bf741e1..ceee552 100644
--- a/backends/imgui_impl_wgpu.cpp
+++ b/backends/imgui_impl_wgpu.cpp
@@ -5,6 +5,8 @@
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'WGPUTextureView' as ImTextureID. Read the FAQ about ImTextureID!
 //  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.
+// Missing features:
+//  [ ] Renderer: Multi-viewport support (multiple windows). Not meaningful on the web.
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
diff --git a/backends/imgui_impl_wgpu.h b/backends/imgui_impl_wgpu.h
index 2e19ea3..a43f34c 100644
--- a/backends/imgui_impl_wgpu.h
+++ b/backends/imgui_impl_wgpu.h
@@ -5,6 +5,8 @@
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'WGPUTextureView' as ImTextureID. Read the FAQ about ImTextureID!
 //  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.
+// Missing features:
+//  [ ] Renderer: Multi-viewport support (multiple windows). Not meaningful on the web.
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
diff --git a/backends/imgui_impl_win32.cpp b/backends/imgui_impl_win32.cpp
index 3e59b62..c079a2b 100644
--- a/backends/imgui_impl_win32.cpp
+++ b/backends/imgui_impl_win32.cpp
@@ -7,6 +7,7 @@
 //  [X] Platform: Keyboard support. Since 1.87 we are using the io.AddKeyEvent() function. Pass ImGuiKey values to all key functions e.g. ImGui::IsKeyPressed(ImGuiKey_Space). [Legacy VK_* values will also be supported unless IMGUI_DISABLE_OBSOLETE_KEYIO is set]
 //  [X] Platform: Gamepad support. Enabled with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
 //  [X] Platform: Mouse cursor shape and visibility. Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange'.
+//  [X] Platform: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
@@ -21,6 +22,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2024-XX-XX: Platform: Added support for multiple windows via the ImGuiPlatformIO interface.
 //  2023-10-05: Inputs: Added support for extra ImGuiKey values: F13 to F24 function keys, app back/forward keys.
 //  2023-09-25: Inputs: Synthesize key-down event on key-up for VK_SNAPSHOT / ImGuiKey_PrintScreen as Windows doesn't emit it (same behavior as GLFW/SDL).
 //  2023-09-07: Inputs: Added support for keyboard codepage conversion for when application is compiled in MBCS mode and using a non-Unicode window.
@@ -101,6 +103,11 @@
 #pragma GCC diagnostic ignored "-Wcast-function-type"       // warning: cast between incompatible function types (for loader)
 #endif
 
+// Forward Declarations
+static void ImGui_ImplWin32_InitPlatformInterface(bool platform_has_own_dc);
+static void ImGui_ImplWin32_ShutdownPlatformInterface();
+static void ImGui_ImplWin32_UpdateMonitors();
+
 struct ImGui_ImplWin32_Data
 {
     HWND                        hWnd;
@@ -111,6 +118,7 @@
     INT64                       TicksPerSecond;
     ImGuiMouseCursor            LastMouseCursor;
     UINT32                      KeyboardCodePage;
+    bool                        WantUpdateMonitors;
 
 #ifndef IMGUI_IMPL_WIN32_DISABLE_GAMEPAD
     bool                        HasGamepad;
@@ -161,16 +169,21 @@
     io.BackendPlatformName = "imgui_impl_win32";
     io.BackendFlags |= ImGuiBackendFlags_HasMouseCursors;         // We can honor GetMouseCursor() values (optional)
     io.BackendFlags |= ImGuiBackendFlags_HasSetMousePos;          // We can honor io.WantSetMousePos requests (optional, rarely used)
+    io.BackendFlags |= ImGuiBackendFlags_PlatformHasViewports;    // We can create multi-viewports on the Platform side (optional)
+    io.BackendFlags |= ImGuiBackendFlags_HasMouseHoveredViewport; // We can call io.AddMouseViewportEvent() with correct data (optional)
 
     bd->hWnd = (HWND)hwnd;
+    bd->WantUpdateMonitors = true;
     bd->TicksPerSecond = perf_frequency;
     bd->Time = perf_counter;
     bd->LastMouseCursor = ImGuiMouseCursor_COUNT;
     ImGui_ImplWin32_UpdateKeyboardCodePage();
 
-    // Set platform dependent data in viewport
-    ImGui::GetMainViewport()->PlatformHandleRaw = (void*)hwnd;
-    IM_UNUSED(platform_has_own_dc); // Used in 'docking' branch
+    // Our mouse update function expect PlatformHandle to be filled for the main viewport
+    ImGuiViewport* main_viewport = ImGui::GetMainViewport();
+    main_viewport->PlatformHandle = main_viewport->PlatformHandleRaw = (void*)bd->hWnd;
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        ImGui_ImplWin32_InitPlatformInterface(platform_has_own_dc);
 
     // Dynamically load XInput library
 #ifndef IMGUI_IMPL_WIN32_DISABLE_GAMEPAD
@@ -213,6 +226,8 @@
     IM_ASSERT(bd != nullptr && "No platform backend to shutdown, or already shutdown?");
     ImGuiIO& io = ImGui::GetIO();
 
+    ImGui_ImplWin32_ShutdownPlatformInterface();
+
     // Unload XInput library
 #ifndef IMGUI_IMPL_WIN32_DISABLE_GAMEPAD
     if (bd->XInputDLL)
@@ -221,7 +236,7 @@
 
     io.BackendPlatformName = nullptr;
     io.BackendPlatformUserData = nullptr;
-    io.BackendFlags &= ~(ImGuiBackendFlags_HasMouseCursors | ImGuiBackendFlags_HasSetMousePos | ImGuiBackendFlags_HasGamepad);
+    io.BackendFlags &= ~(ImGuiBackendFlags_HasMouseCursors | ImGuiBackendFlags_HasSetMousePos | ImGuiBackendFlags_HasGamepad | ImGuiBackendFlags_PlatformHasViewports | ImGuiBackendFlags_HasMouseHoveredViewport);
     IM_DELETE(bd);
 }
 
@@ -295,33 +310,59 @@
     io.AddKeyEvent(ImGuiMod_Super, IsVkDown(VK_APPS));
 }
 
+// This code supports multi-viewports (multiple OS Windows mapped into different Dear ImGui viewports)
+// Because of that, it is a little more complicated than your typical single-viewport binding code!
 static void ImGui_ImplWin32_UpdateMouseData()
 {
     ImGui_ImplWin32_Data* bd = ImGui_ImplWin32_GetBackendData();
     ImGuiIO& io = ImGui::GetIO();
     IM_ASSERT(bd->hWnd != 0);
 
+    POINT mouse_screen_pos;
+    bool has_mouse_screen_pos = ::GetCursorPos(&mouse_screen_pos) != 0;
+
     HWND focused_window = ::GetForegroundWindow();
-    const bool is_app_focused = (focused_window == bd->hWnd);
+    const bool is_app_focused = (focused_window && (focused_window == bd->hWnd || ::IsChild(focused_window, bd->hWnd) || ImGui::FindViewportByPlatformHandle((void*)focused_window)));
     if (is_app_focused)
     {
         // (Optional) Set OS mouse position from Dear ImGui if requested (rarely used, only when ImGuiConfigFlags_NavEnableSetMousePos is enabled by user)
+        // When multi-viewports are enabled, all Dear ImGui positions are same as OS positions.
         if (io.WantSetMousePos)
         {
             POINT pos = { (int)io.MousePos.x, (int)io.MousePos.y };
-            if (::ClientToScreen(bd->hWnd, &pos))
-                ::SetCursorPos(pos.x, pos.y);
+            if ((io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable) == 0)
+                ::ClientToScreen(focused_window, &pos);
+            ::SetCursorPos(pos.x, pos.y);
         }
 
         // (Optional) Fallback to provide mouse position when focused (WM_MOUSEMOVE already provides this when hovered or captured)
         // This also fills a short gap when clicking non-client area: WM_NCMOUSELEAVE -> modal OS move -> gap -> WM_NCMOUSEMOVE
-        if (!io.WantSetMousePos && bd->MouseTrackedArea == 0)
+        if (!io.WantSetMousePos && bd->MouseTrackedArea == 0 && has_mouse_screen_pos)
         {
-            POINT pos;
-            if (::GetCursorPos(&pos) && ::ScreenToClient(bd->hWnd, &pos))
-                io.AddMousePosEvent((float)pos.x, (float)pos.y);
+            // Single viewport mode: mouse position in client window coordinates (io.MousePos is (0,0) when the mouse is on the upper-left corner of the app window)
+            // (This is the position you can get with ::GetCursorPos() + ::ScreenToClient() or WM_MOUSEMOVE.)
+            // Multi-viewport mode: mouse position in OS absolute coordinates (io.MousePos is (0,0) when the mouse is on the upper-left of the primary monitor)
+            // (This is the position you can get with ::GetCursorPos() or WM_MOUSEMOVE + ::ClientToScreen(). In theory adding viewport->Pos to a client position would also be the same.)
+            POINT mouse_pos = mouse_screen_pos;
+            if (!(io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable))
+                ::ScreenToClient(bd->hWnd, &mouse_pos);
+            io.AddMousePosEvent((float)mouse_pos.x, (float)mouse_pos.y);
         }
     }
+
+    // (Optional) When using multiple viewports: call io.AddMouseViewportEvent() with the viewport the OS mouse cursor is hovering.
+    // If ImGuiBackendFlags_HasMouseHoveredViewport is not set by the backend, Dear imGui will ignore this field and infer the information using its flawed heuristic.
+    // - [X] Win32 backend correctly ignore viewports with the _NoInputs flag (here using ::WindowFromPoint with WM_NCHITTEST + HTTRANSPARENT in WndProc does that)
+    //       Some backend are not able to handle that correctly. If a backend report an hovered viewport that has the _NoInputs flag (e.g. when dragging a window
+    //       for docking, the viewport has the _NoInputs flag in order to allow us to find the viewport under), then Dear ImGui is forced to ignore the value reported
+    //       by the backend, and use its flawed heuristic to guess the viewport behind.
+    // - [X] Win32 backend correctly reports this regardless of another viewport behind focused and dragged from (we need this to find a useful drag and drop target).
+    ImGuiID mouse_viewport_id = 0;
+    if (has_mouse_screen_pos)
+        if (HWND hovered_hwnd = ::WindowFromPoint(mouse_screen_pos))
+            if (ImGuiViewport* viewport = ImGui::FindViewportByPlatformHandle((void*)hovered_hwnd))
+                mouse_viewport_id = viewport->ID;
+    io.AddMouseViewportEvent(mouse_viewport_id);
 }
 
 // Gamepad navigation mapping
@@ -381,6 +422,35 @@
 #endif // #ifndef IMGUI_IMPL_WIN32_DISABLE_GAMEPAD
 }
 
+static BOOL CALLBACK ImGui_ImplWin32_UpdateMonitors_EnumFunc(HMONITOR monitor, HDC, LPRECT, LPARAM)
+{
+    MONITORINFO info = {};
+    info.cbSize = sizeof(MONITORINFO);
+    if (!::GetMonitorInfo(monitor, &info))
+        return TRUE;
+    ImGuiPlatformMonitor imgui_monitor;
+    imgui_monitor.MainPos = ImVec2((float)info.rcMonitor.left, (float)info.rcMonitor.top);
+    imgui_monitor.MainSize = ImVec2((float)(info.rcMonitor.right - info.rcMonitor.left), (float)(info.rcMonitor.bottom - info.rcMonitor.top));
+    imgui_monitor.WorkPos = ImVec2((float)info.rcWork.left, (float)info.rcWork.top);
+    imgui_monitor.WorkSize = ImVec2((float)(info.rcWork.right - info.rcWork.left), (float)(info.rcWork.bottom - info.rcWork.top));
+    imgui_monitor.DpiScale = ImGui_ImplWin32_GetDpiScaleForMonitor(monitor);
+    imgui_monitor.PlatformHandle = (void*)monitor;
+    ImGuiPlatformIO& io = ImGui::GetPlatformIO();
+    if (info.dwFlags & MONITORINFOF_PRIMARY)
+        io.Monitors.push_front(imgui_monitor);
+    else
+        io.Monitors.push_back(imgui_monitor);
+    return TRUE;
+}
+
+static void ImGui_ImplWin32_UpdateMonitors()
+{
+    ImGui_ImplWin32_Data* bd = ImGui_ImplWin32_GetBackendData();
+    ImGui::GetPlatformIO().Monitors.resize(0);
+    ::EnumDisplayMonitors(nullptr, nullptr, ImGui_ImplWin32_UpdateMonitors_EnumFunc, 0);
+    bd->WantUpdateMonitors = false;
+}
+
 void    ImGui_ImplWin32_NewFrame()
 {
     ImGui_ImplWin32_Data* bd = ImGui_ImplWin32_GetBackendData();
@@ -391,6 +461,8 @@
     RECT rect = { 0, 0, 0, 0 };
     ::GetClientRect(bd->hWnd, &rect);
     io.DisplaySize = ImVec2((float)(rect.right - rect.left), (float)(rect.bottom - rect.top));
+    if (bd->WantUpdateMonitors)
+        ImGui_ImplWin32_UpdateMonitors();
 
     // Setup time step
     INT64 current_time = 0;
@@ -607,8 +679,11 @@
             bd->MouseTrackedArea = area;
         }
         POINT mouse_pos = { (LONG)GET_X_LPARAM(lParam), (LONG)GET_Y_LPARAM(lParam) };
-        if (msg == WM_NCMOUSEMOVE && ::ScreenToClient(hwnd, &mouse_pos) == FALSE) // WM_NCMOUSEMOVE are provided in absolute coordinates.
-            return 0;
+        bool want_absolute_pos = (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable) != 0;
+        if (msg == WM_MOUSEMOVE && want_absolute_pos)    // WM_MOUSEMOVE are client-relative coordinates.
+            ::ClientToScreen(hwnd, &mouse_pos);
+        if (msg == WM_NCMOUSEMOVE && !want_absolute_pos) // WM_NCMOUSEMOVE are absolute coordinates.
+            ::ScreenToClient(hwnd, &mouse_pos);
         io.AddMouseSourceEvent(mouse_source);
         io.AddMousePosEvent((float)mouse_pos.x, (float)mouse_pos.y);
         return 0;
@@ -747,6 +822,9 @@
             bd->WantUpdateHasGamepad = true;
 #endif
         return 0;
+    case WM_DISPLAYCHANGE:
+        bd->WantUpdateMonitors = true;
+        return 0;
     }
     return 0;
 }
@@ -811,6 +889,10 @@
 // Helper function to enable DPI awareness without setting up a manifest
 void ImGui_ImplWin32_EnableDpiAwareness()
 {
+    // Make sure monitors will be updated with latest correct scaling
+    if (ImGui_ImplWin32_Data* bd = ImGui_ImplWin32_GetBackendData())
+        bd->WantUpdateMonitors = true;
+
     if (_IsWindows10OrGreater())
     {
         static HINSTANCE user32_dll = ::LoadLibraryA("user32.dll"); // Reference counted per-process
@@ -911,6 +993,358 @@
 }
 
 //---------------------------------------------------------------------------------------------------------
+// MULTI-VIEWPORT / PLATFORM INTERFACE SUPPORT
+// This is an _advanced_ and _optional_ feature, allowing the backend to create and handle multiple viewports simultaneously.
+// If you are new to dear imgui or creating a new binding for dear imgui, it is recommended that you completely ignore this section first..
+//--------------------------------------------------------------------------------------------------------
+
+// Helper structure we store in the void* RendererUserData field of each ImGuiViewport to easily retrieve our backend data.
+struct ImGui_ImplWin32_ViewportData
+{
+    HWND    Hwnd;
+    HWND    HwndParent;
+    bool    HwndOwned;
+    DWORD   DwStyle;
+    DWORD   DwExStyle;
+
+    ImGui_ImplWin32_ViewportData() { Hwnd = HwndParent = nullptr; HwndOwned = false;  DwStyle = DwExStyle = 0; }
+    ~ImGui_ImplWin32_ViewportData() { IM_ASSERT(Hwnd == nullptr); }
+};
+
+static void ImGui_ImplWin32_GetWin32StyleFromViewportFlags(ImGuiViewportFlags flags, DWORD* out_style, DWORD* out_ex_style)
+{
+    if (flags & ImGuiViewportFlags_NoDecoration)
+        *out_style = WS_POPUP;
+    else
+        *out_style = WS_OVERLAPPEDWINDOW;
+
+    if (flags & ImGuiViewportFlags_NoTaskBarIcon)
+        *out_ex_style = WS_EX_TOOLWINDOW;
+    else
+        *out_ex_style = WS_EX_APPWINDOW;
+
+    if (flags & ImGuiViewportFlags_TopMost)
+        *out_ex_style |= WS_EX_TOPMOST;
+}
+
+static HWND ImGui_ImplWin32_GetHwndFromViewportID(ImGuiID viewport_id)
+{
+    if (viewport_id != 0)
+        if (ImGuiViewport* viewport = ImGui::FindViewportByID(viewport_id))
+            return (HWND)viewport->PlatformHandle;
+    return nullptr;
+}
+
+static void ImGui_ImplWin32_CreateWindow(ImGuiViewport* viewport)
+{
+    ImGui_ImplWin32_ViewportData* vd = IM_NEW(ImGui_ImplWin32_ViewportData)();
+    viewport->PlatformUserData = vd;
+
+    // Select style and parent window
+    ImGui_ImplWin32_GetWin32StyleFromViewportFlags(viewport->Flags, &vd->DwStyle, &vd->DwExStyle);
+    vd->HwndParent = ImGui_ImplWin32_GetHwndFromViewportID(viewport->ParentViewportId);
+
+    // Create window
+    RECT rect = { (LONG)viewport->Pos.x, (LONG)viewport->Pos.y, (LONG)(viewport->Pos.x + viewport->Size.x), (LONG)(viewport->Pos.y + viewport->Size.y) };
+    ::AdjustWindowRectEx(&rect, vd->DwStyle, FALSE, vd->DwExStyle);
+    vd->Hwnd = ::CreateWindowEx(
+        vd->DwExStyle, _T("ImGui Platform"), _T("Untitled"), vd->DwStyle,       // Style, class name, window name
+        rect.left, rect.top, rect.right - rect.left, rect.bottom - rect.top,    // Window area
+        vd->HwndParent, nullptr, ::GetModuleHandle(nullptr), nullptr);          // Owner window, Menu, Instance, Param
+    vd->HwndOwned = true;
+    viewport->PlatformRequestResize = false;
+    viewport->PlatformHandle = viewport->PlatformHandleRaw = vd->Hwnd;
+}
+
+static void ImGui_ImplWin32_DestroyWindow(ImGuiViewport* viewport)
+{
+    ImGui_ImplWin32_Data* bd = ImGui_ImplWin32_GetBackendData();
+    if (ImGui_ImplWin32_ViewportData* vd = (ImGui_ImplWin32_ViewportData*)viewport->PlatformUserData)
+    {
+        if (::GetCapture() == vd->Hwnd)
+        {
+            // Transfer capture so if we started dragging from a window that later disappears, we'll still receive the MOUSEUP event.
+            ::ReleaseCapture();
+            ::SetCapture(bd->hWnd);
+        }
+        if (vd->Hwnd && vd->HwndOwned)
+            ::DestroyWindow(vd->Hwnd);
+        vd->Hwnd = nullptr;
+        IM_DELETE(vd);
+    }
+    viewport->PlatformUserData = viewport->PlatformHandle = nullptr;
+}
+
+static void ImGui_ImplWin32_ShowWindow(ImGuiViewport* viewport)
+{
+    ImGui_ImplWin32_ViewportData* vd = (ImGui_ImplWin32_ViewportData*)viewport->PlatformUserData;
+    IM_ASSERT(vd->Hwnd != 0);
+
+    // ShowParent() also brings parent to front, which is not always desirable,
+    // so we temporarily disable parenting. (#7354)
+    if (vd->HwndParent != NULL)
+        ::SetWindowLongPtr(vd->Hwnd, GWLP_HWNDPARENT, (LONG_PTR)nullptr);
+
+    if (viewport->Flags & ImGuiViewportFlags_NoFocusOnAppearing)
+        ::ShowWindow(vd->Hwnd, SW_SHOWNA);
+    else
+        ::ShowWindow(vd->Hwnd, SW_SHOW);
+
+    // Restore
+    if (vd->HwndParent != NULL)
+        ::SetWindowLongPtr(vd->Hwnd, GWLP_HWNDPARENT, (LONG_PTR)vd->HwndParent);
+}
+
+static void ImGui_ImplWin32_UpdateWindow(ImGuiViewport* viewport)
+{
+    ImGui_ImplWin32_ViewportData* vd = (ImGui_ImplWin32_ViewportData*)viewport->PlatformUserData;
+    IM_ASSERT(vd->Hwnd != 0);
+
+    // Update Win32 parent if it changed _after_ creation
+    // Unlike style settings derived from configuration flags, this is more likely to change for advanced apps that are manipulating ParentViewportID manually.
+    HWND new_parent = ImGui_ImplWin32_GetHwndFromViewportID(viewport->ParentViewportId);
+    if (new_parent != vd->HwndParent)
+    {
+        // Win32 windows can either have a "Parent" (for WS_CHILD window) or an "Owner" (which among other thing keeps window above its owner).
+        // Our Dear Imgui-side concept of parenting only mostly care about what Win32 call "Owner".
+        // The parent parameter of CreateWindowEx() sets up Parent OR Owner depending on WS_CHILD flag. In our case an Owner as we never use WS_CHILD.
+        // Calling ::SetParent() here would be incorrect: it will create a full child relation, alter coordinate system and clipping.
+        // Calling ::SetWindowLongPtr() with GWLP_HWNDPARENT seems correct although poorly documented.
+        // https://devblogs.microsoft.com/oldnewthing/20100315-00/?p=14613
+        vd->HwndParent = new_parent;
+        ::SetWindowLongPtr(vd->Hwnd, GWLP_HWNDPARENT, (LONG_PTR)vd->HwndParent);
+    }
+
+    // (Optional) Update Win32 style if it changed _after_ creation.
+    // Generally they won't change unless configuration flags are changed, but advanced uses (such as manually rewriting viewport flags) make this useful.
+    DWORD new_style;
+    DWORD new_ex_style;
+    ImGui_ImplWin32_GetWin32StyleFromViewportFlags(viewport->Flags, &new_style, &new_ex_style);
+
+    // Only reapply the flags that have been changed from our point of view (as other flags are being modified by Windows)
+    if (vd->DwStyle != new_style || vd->DwExStyle != new_ex_style)
+    {
+        // (Optional) Update TopMost state if it changed _after_ creation
+        bool top_most_changed = (vd->DwExStyle & WS_EX_TOPMOST) != (new_ex_style & WS_EX_TOPMOST);
+        HWND insert_after = top_most_changed ? ((viewport->Flags & ImGuiViewportFlags_TopMost) ? HWND_TOPMOST : HWND_NOTOPMOST) : 0;
+        UINT swp_flag = top_most_changed ? 0 : SWP_NOZORDER;
+
+        // Apply flags and position (since it is affected by flags)
+        vd->DwStyle = new_style;
+        vd->DwExStyle = new_ex_style;
+        ::SetWindowLong(vd->Hwnd, GWL_STYLE, vd->DwStyle);
+        ::SetWindowLong(vd->Hwnd, GWL_EXSTYLE, vd->DwExStyle);
+        RECT rect = { (LONG)viewport->Pos.x, (LONG)viewport->Pos.y, (LONG)(viewport->Pos.x + viewport->Size.x), (LONG)(viewport->Pos.y + viewport->Size.y) };
+        ::AdjustWindowRectEx(&rect, vd->DwStyle, FALSE, vd->DwExStyle); // Client to Screen
+        ::SetWindowPos(vd->Hwnd, insert_after, rect.left, rect.top, rect.right - rect.left, rect.bottom - rect.top, swp_flag | SWP_NOACTIVATE | SWP_FRAMECHANGED);
+        ::ShowWindow(vd->Hwnd, SW_SHOWNA); // This is necessary when we alter the style
+        viewport->PlatformRequestMove = viewport->PlatformRequestResize = true;
+    }
+}
+
+static ImVec2 ImGui_ImplWin32_GetWindowPos(ImGuiViewport* viewport)
+{
+    ImGui_ImplWin32_ViewportData* vd = (ImGui_ImplWin32_ViewportData*)viewport->PlatformUserData;
+    IM_ASSERT(vd->Hwnd != 0);
+    POINT pos = { 0, 0 };
+    ::ClientToScreen(vd->Hwnd, &pos);
+    return ImVec2((float)pos.x, (float)pos.y);
+}
+
+static void ImGui_ImplWin32_SetWindowPos(ImGuiViewport* viewport, ImVec2 pos)
+{
+    ImGui_ImplWin32_ViewportData* vd = (ImGui_ImplWin32_ViewportData*)viewport->PlatformUserData;
+    IM_ASSERT(vd->Hwnd != 0);
+    RECT rect = { (LONG)pos.x, (LONG)pos.y, (LONG)pos.x, (LONG)pos.y };
+    ::AdjustWindowRectEx(&rect, vd->DwStyle, FALSE, vd->DwExStyle);
+    ::SetWindowPos(vd->Hwnd, nullptr, rect.left, rect.top, 0, 0, SWP_NOZORDER | SWP_NOSIZE | SWP_NOACTIVATE);
+}
+
+static ImVec2 ImGui_ImplWin32_GetWindowSize(ImGuiViewport* viewport)
+{
+    ImGui_ImplWin32_ViewportData* vd = (ImGui_ImplWin32_ViewportData*)viewport->PlatformUserData;
+    IM_ASSERT(vd->Hwnd != 0);
+    RECT rect;
+    ::GetClientRect(vd->Hwnd, &rect);
+    return ImVec2(float(rect.right - rect.left), float(rect.bottom - rect.top));
+}
+
+static void ImGui_ImplWin32_SetWindowSize(ImGuiViewport* viewport, ImVec2 size)
+{
+    ImGui_ImplWin32_ViewportData* vd = (ImGui_ImplWin32_ViewportData*)viewport->PlatformUserData;
+    IM_ASSERT(vd->Hwnd != 0);
+    RECT rect = { 0, 0, (LONG)size.x, (LONG)size.y };
+    ::AdjustWindowRectEx(&rect, vd->DwStyle, FALSE, vd->DwExStyle); // Client to Screen
+    ::SetWindowPos(vd->Hwnd, nullptr, 0, 0, rect.right - rect.left, rect.bottom - rect.top, SWP_NOZORDER | SWP_NOMOVE | SWP_NOACTIVATE);
+}
+
+static void ImGui_ImplWin32_SetWindowFocus(ImGuiViewport* viewport)
+{
+    ImGui_ImplWin32_ViewportData* vd = (ImGui_ImplWin32_ViewportData*)viewport->PlatformUserData;
+    IM_ASSERT(vd->Hwnd != 0);
+    ::BringWindowToTop(vd->Hwnd);
+    ::SetForegroundWindow(vd->Hwnd);
+    ::SetFocus(vd->Hwnd);
+}
+
+static bool ImGui_ImplWin32_GetWindowFocus(ImGuiViewport* viewport)
+{
+    ImGui_ImplWin32_ViewportData* vd = (ImGui_ImplWin32_ViewportData*)viewport->PlatformUserData;
+    IM_ASSERT(vd->Hwnd != 0);
+    return ::GetForegroundWindow() == vd->Hwnd;
+}
+
+static bool ImGui_ImplWin32_GetWindowMinimized(ImGuiViewport* viewport)
+{
+    ImGui_ImplWin32_ViewportData* vd = (ImGui_ImplWin32_ViewportData*)viewport->PlatformUserData;
+    IM_ASSERT(vd->Hwnd != 0);
+    return ::IsIconic(vd->Hwnd) != 0;
+}
+
+static void ImGui_ImplWin32_SetWindowTitle(ImGuiViewport* viewport, const char* title)
+{
+    // ::SetWindowTextA() doesn't properly handle UTF-8 so we explicitely convert our string.
+    ImGui_ImplWin32_ViewportData* vd = (ImGui_ImplWin32_ViewportData*)viewport->PlatformUserData;
+    IM_ASSERT(vd->Hwnd != 0);
+    int n = ::MultiByteToWideChar(CP_UTF8, 0, title, -1, nullptr, 0);
+    ImVector<wchar_t> title_w;
+    title_w.resize(n);
+    ::MultiByteToWideChar(CP_UTF8, 0, title, -1, title_w.Data, n);
+    ::SetWindowTextW(vd->Hwnd, title_w.Data);
+}
+
+static void ImGui_ImplWin32_SetWindowAlpha(ImGuiViewport* viewport, float alpha)
+{
+    ImGui_ImplWin32_ViewportData* vd = (ImGui_ImplWin32_ViewportData*)viewport->PlatformUserData;
+    IM_ASSERT(vd->Hwnd != 0);
+    IM_ASSERT(alpha >= 0.0f && alpha <= 1.0f);
+    if (alpha < 1.0f)
+    {
+        DWORD style = ::GetWindowLongW(vd->Hwnd, GWL_EXSTYLE) | WS_EX_LAYERED;
+        ::SetWindowLongW(vd->Hwnd, GWL_EXSTYLE, style);
+        ::SetLayeredWindowAttributes(vd->Hwnd, 0, (BYTE)(255 * alpha), LWA_ALPHA);
+    }
+    else
+    {
+        DWORD style = ::GetWindowLongW(vd->Hwnd, GWL_EXSTYLE) & ~WS_EX_LAYERED;
+        ::SetWindowLongW(vd->Hwnd, GWL_EXSTYLE, style);
+    }
+}
+
+static float ImGui_ImplWin32_GetWindowDpiScale(ImGuiViewport* viewport)
+{
+    ImGui_ImplWin32_ViewportData* vd = (ImGui_ImplWin32_ViewportData*)viewport->PlatformUserData;
+    IM_ASSERT(vd->Hwnd != 0);
+    return ImGui_ImplWin32_GetDpiScaleForHwnd(vd->Hwnd);
+}
+
+// FIXME-DPI: Testing DPI related ideas
+static void ImGui_ImplWin32_OnChangedViewport(ImGuiViewport* viewport)
+{
+    (void)viewport;
+#if 0
+    ImGuiStyle default_style;
+    //default_style.WindowPadding = ImVec2(0, 0);
+    //default_style.WindowBorderSize = 0.0f;
+    //default_style.ItemSpacing.y = 3.0f;
+    //default_style.FramePadding = ImVec2(0, 0);
+    default_style.ScaleAllSizes(viewport->DpiScale);
+    ImGuiStyle& style = ImGui::GetStyle();
+    style = default_style;
+#endif
+}
+
+static LRESULT CALLBACK ImGui_ImplWin32_WndProcHandler_PlatformWindow(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
+{
+    if (ImGui_ImplWin32_WndProcHandler(hWnd, msg, wParam, lParam))
+        return true;
+
+    if (ImGuiViewport* viewport = ImGui::FindViewportByPlatformHandle((void*)hWnd))
+    {
+        switch (msg)
+        {
+        case WM_CLOSE:
+            viewport->PlatformRequestClose = true;
+            return 0;
+        case WM_MOVE:
+            viewport->PlatformRequestMove = true;
+            break;
+        case WM_SIZE:
+            viewport->PlatformRequestResize = true;
+            break;
+        case WM_MOUSEACTIVATE:
+            if (viewport->Flags & ImGuiViewportFlags_NoFocusOnClick)
+                return MA_NOACTIVATE;
+            break;
+        case WM_NCHITTEST:
+            // Let mouse pass-through the window. This will allow the backend to call io.AddMouseViewportEvent() correctly. (which is optional).
+            // The ImGuiViewportFlags_NoInputs flag is set while dragging a viewport, as want to detect the window behind the one we are dragging.
+            // If you cannot easily access those viewport flags from your windowing/event code: you may manually synchronize its state e.g. in
+            // your main loop after calling UpdatePlatformWindows(). Iterate all viewports/platform windows and pass the flag to your windowing system.
+            if (viewport->Flags & ImGuiViewportFlags_NoInputs)
+                return HTTRANSPARENT;
+            break;
+        }
+    }
+
+    return DefWindowProc(hWnd, msg, wParam, lParam);
+}
+
+static void ImGui_ImplWin32_InitPlatformInterface(bool platform_has_own_dc)
+{
+    WNDCLASSEX wcex;
+    wcex.cbSize = sizeof(WNDCLASSEX);
+    wcex.style = CS_HREDRAW | CS_VREDRAW | (platform_has_own_dc ? CS_OWNDC : 0);
+    wcex.lpfnWndProc = ImGui_ImplWin32_WndProcHandler_PlatformWindow;
+    wcex.cbClsExtra = 0;
+    wcex.cbWndExtra = 0;
+    wcex.hInstance = ::GetModuleHandle(nullptr);
+    wcex.hIcon = nullptr;
+    wcex.hCursor = nullptr;
+    wcex.hbrBackground = (HBRUSH)(COLOR_BACKGROUND + 1);
+    wcex.lpszMenuName = nullptr;
+    wcex.lpszClassName = _T("ImGui Platform");
+    wcex.hIconSm = nullptr;
+    ::RegisterClassEx(&wcex);
+
+    ImGui_ImplWin32_UpdateMonitors();
+
+    // Register platform interface (will be coupled with a renderer interface)
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    platform_io.Platform_CreateWindow = ImGui_ImplWin32_CreateWindow;
+    platform_io.Platform_DestroyWindow = ImGui_ImplWin32_DestroyWindow;
+    platform_io.Platform_ShowWindow = ImGui_ImplWin32_ShowWindow;
+    platform_io.Platform_SetWindowPos = ImGui_ImplWin32_SetWindowPos;
+    platform_io.Platform_GetWindowPos = ImGui_ImplWin32_GetWindowPos;
+    platform_io.Platform_SetWindowSize = ImGui_ImplWin32_SetWindowSize;
+    platform_io.Platform_GetWindowSize = ImGui_ImplWin32_GetWindowSize;
+    platform_io.Platform_SetWindowFocus = ImGui_ImplWin32_SetWindowFocus;
+    platform_io.Platform_GetWindowFocus = ImGui_ImplWin32_GetWindowFocus;
+    platform_io.Platform_GetWindowMinimized = ImGui_ImplWin32_GetWindowMinimized;
+    platform_io.Platform_SetWindowTitle = ImGui_ImplWin32_SetWindowTitle;
+    platform_io.Platform_SetWindowAlpha = ImGui_ImplWin32_SetWindowAlpha;
+    platform_io.Platform_UpdateWindow = ImGui_ImplWin32_UpdateWindow;
+    platform_io.Platform_GetWindowDpiScale = ImGui_ImplWin32_GetWindowDpiScale; // FIXME-DPI
+    platform_io.Platform_OnChangedViewport = ImGui_ImplWin32_OnChangedViewport; // FIXME-DPI
+
+    // Register main window handle (which is owned by the main application, not by us)
+    // This is mostly for simplicity and consistency, so that our code (e.g. mouse handling etc.) can use same logic for main and secondary viewports.
+    ImGuiViewport* main_viewport = ImGui::GetMainViewport();
+    ImGui_ImplWin32_Data* bd = ImGui_ImplWin32_GetBackendData();
+    ImGui_ImplWin32_ViewportData* vd = IM_NEW(ImGui_ImplWin32_ViewportData)();
+    vd->Hwnd = bd->hWnd;
+    vd->HwndOwned = false;
+    main_viewport->PlatformUserData = vd;
+    main_viewport->PlatformHandle = (void*)bd->hWnd;
+}
+
+static void ImGui_ImplWin32_ShutdownPlatformInterface()
+{
+    ::UnregisterClass(_T("ImGui Platform"), ::GetModuleHandle(nullptr));
+    ImGui::DestroyPlatformWindows();
+}
+
+//---------------------------------------------------------------------------------------------------------
 
 #if defined(__GNUC__)
 #pragma GCC diagnostic pop
diff --git a/backends/imgui_impl_win32.h b/backends/imgui_impl_win32.h
index be56271..cebe661 100644
--- a/backends/imgui_impl_win32.h
+++ b/backends/imgui_impl_win32.h
@@ -7,6 +7,7 @@
 //  [X] Platform: Keyboard support. Since 1.87 we are using the io.AddKeyEvent() function. Pass ImGuiKey values to all key functions e.g. ImGui::IsKeyPressed(ImGuiKey_Space). [Legacy VK_* values will also be supported unless IMGUI_DISABLE_OBSOLETE_KEYIO is set]
 //  [X] Platform: Gamepad support. Enabled with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
 //  [X] Platform: Mouse cursor shape and visibility. Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange'.
+//  [X] Platform: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
diff --git a/docs/CHANGELOG.txt b/docs/CHANGELOG.txt
index 0a3263e..b05fc85 100644
--- a/docs/CHANGELOG.txt
+++ b/docs/CHANGELOG.txt
@@ -120,6 +120,16 @@
   Added asserts for valid flags in various functions to detect _some_ misuses, BUT NOT ALL.
 
 
+Docking+Viewports Branch:
+
+- Docking: *BREAKING* changed signature of DockSpaceOverViewport() to allow passing
+  an explicit dockspace id if desired. (#7611)
+    Before: DockSpaceOverViewport(const ImGuiViewport* viewport = NULL, ImGuiDockNodeFlags flags = 0, ...);
+    After:  DockSpaceOverViewport(ImGuiID dockspace_id = 0, const ImGuiViewport* viewport = NULL, ImGuiDockNodeFlags flags = 0, ...);
+  Simply add a leading 0 to your existing calls to DockSpaceOverViewport() if you have any.
+- Tables: resizing border hit-rect scales according to current monitor dpi scale.
+
+
 -----------------------------------------------------------------------
  VERSION 1.90.6 (Released 2024-05-08)
 -----------------------------------------------------------------------
@@ -177,6 +187,18 @@
 - Examples: GLFW+WebGPU: Added support for WebGPU-native/Dawn (#7435, #7132) [@eliasdaler, @Zelif]
 - Examples: GLFW+WebGPU: Renamed example_emscripten_wgpu/ to example_glfw_wgpu/. (#7435, #7132)
 
+Docking+Viewports Branch:
+
+- Docking: when io.ConfigDockingWithShift is enabled, fixed help tooltip erroneously
+  reading SetNextWindowXXX() data. (#6709, #4643, #7491) [@ocornut, @cfillion]
+- Viewports: fixed outer-right edge of MenuBar clipping rectangle off by one when window
+  is located on a monitor with negative coordinates. (#6861, #2884) [@cfillion]
+- Backends: Vulkan: reworked swap-chain resize handling for secondary viewports, fix for
+  typical Linux setups. (#2626, #3390, #3758, #7508, #7513) [@RoryO, @InsideBSITheSecond]
+- Backends: Vulkan: create a custom pipeline for secondary viewports. Fixes issues
+  when user created main viewport uses a different renderpass. (#6325, #6305, #7398,
+  #3459, #3253, #3522) [@skaman, @FunMiles]
+
 
 -----------------------------------------------------------------------
  VERSION 1.90.5 (Released 2024-04-11)
@@ -233,6 +255,11 @@
     Adding a link to the crawlable version, even though it is not intended for humans,
     to increase its search rank.
 
+Docking+Viewports Branch:
+
+- Backends: Win32: made it so that an appearing viewport showing up doesn't bring
+  its parent to front. (#7354)
+
 
 -----------------------------------------------------------------------
  VERSION 1.90.4 (Released 2024-02-22)
@@ -266,6 +293,13 @@
 - Demo: Custom Rendering: better demonstrate PathArcTo(), PathBezierQuadraticCurveTo(),
   PathBezierCubicCurveTo(), PathStroke(), PathFillConvex() functions.
 
+Docking+Viewports Branch:
+
+- Backends: GLFW: enable ImGuiBackendFlags_HasMouseHoveredViewport support with GLFW 3.3.x,
+  as required specs for it was relaxed in 1.87. This enable better viewport hovering detection
+  without GLFW 3.4's GLFW_MOUSE_PASSTHROUGH, with less reliance on dear imgui's own heuristic
+  of platform windows order. (#7316)
+
 
 -----------------------------------------------------------------------
  VERSION 1.90.3 (Released 2024-02-14)
@@ -354,6 +388,18 @@
   Often requested in some form (#6962, #5219, #3290, #4627, #5054, #3878, #2881, #1506, #1216, #968),
   and useful for interactive completion/suggestions popups (#2057, #718)
 
+Docking+Viewports Branch:
+
+- Added ImGuiWindowClass::FocusRouteParentWindowId as a way to connect the focus route between
+  a tool window to a parent document window, so that Shortcuts in the documents are routed when the
+  tool is focused (regardless of whether the tool is docked or in a floating viewport, etc.) (#6798)
+- Added ImGuiDockNodeFlags_DockedWindowsInFocusRoute to automatically make a dockspace connect
+  the focus route of its docked window. This is provided a convenience in case you have windows
+  where a connection is not explicit. (#6798)
+- Viewports: Fixed moving accross monitors when io.ConfigWindowsMoveFromTitleBarOnly is set. (#7299, #3071)
+- Backends: OSX: Fixed not submitting Monitors info when viewports are not enabled, leading to
+  missing e.g. DpiScale info. (#7257) [@actboy168]
+
 
 -----------------------------------------------------------------------
  VERSION 1.90.1 (Released 2024-01-10)
@@ -458,6 +504,15 @@
     (#6751) [@Traveller23, @ypujante]
   - Examples: SDL3: Minor fixes following recent SDL3 in-progress development.
 
+Docking+Viewports Branch:
+
+- Windows: Fixed ImGuiCol_TitleBg/Active alpha being used for viewport-owned windows. (#7181) [@PathogenDavid]
+- Backends: DX12: Changed swapchain scaling mode to DXGI_SCALING_NONE to reduce artifacts as
+  queued frames aren't synchronized with platform window resizes. (#7152, #7153) [@SuperWangKai]
+- Backends: OSX: Fixed monitor and window position by correctly transforming Y origin on multi-viewports
+  multi-monitor setups. (#7028, #7101, #6009, #6432) [@dmirty-kuzmenko, @734vin]
+- Backends: OSX: Fixed IME position in multi-monitor multi-viewports setups. (#7028) [@734vin]
+
 
 -----------------------------------------------------------------------
  VERSION 1.90.0 (Released 2023-11-15)
@@ -650,6 +705,8 @@
   Fixed leaks, and added ImGui_ImplVulkan_DestroyFontsTexture() (probably no need to call this directly).
   (#6943, #6715, #6327, #3743, #4618)
   [@helynranta, @thomasherzog, @guybrush77, @albin-johansson, @MiroKaku, @benbatya-fb, @ocornut]
+- Backends: Vulkan: use specified ColorAttachmentFormat when creating a secondary window when enabling
+  UseDynamicRendering option. (#6999, #5446, #5037) [@raaaviol]
 - Backends: GLFW: Clear emscripten's MouseWheel callback before shutdown. (#6790, #6096, #4019) [@halx99]
 - Backends: GLFW: Added support for F13 to F24 function keys. (#6891)
 - Backends: SDL2, SDL3: Added support for F13 to F24 function keys, AppBack, AppForward. (#6891)
@@ -667,6 +724,31 @@
 - Examples: GLFW+Vulkan, SDL+Vulkan: Simplified and removed code due to backend improvements.
 - Internals: Renamed ImFloor() to ImTrunc(). Renamed ImFloorSigned() to ImFloor(). (#6861)
 
+Docking+Viewports Branch:
+
+- Viewports: Fixed window inner clipping rectangle off by one when window is located on a monitor
+  with negative coordinates. While it is expected that other small issues with arise from this
+  situation, at the moment we are fixing the most noticeable one. (#6861, #2884) [@Vuhdo, @alektron]
+- Docking: revised undocking to reduce accidental whole-node undocking:
+  - cannot undock a whole node by dragging from empty space in tab-bar.
+  - can undock whole node by dragging from window/collapse menu button.
+  - can undock single window by dragging from its tab.
+  - can still move (but not undock) whole node or whole hierarchy when node is part of a
+    floating hierarchy.
+  - added tooltip when hovering the collapse/window menu button, to faciliate understanding
+    that whole dock node may be undocked or grabbed from here.
+- Docking: Fixed an issue leading to incorrect restoration of selected tab in dock nodes that
+  don't carry the currently focused window. (#2304)
+- Docking: added ImGuiDockNodeFlags_NoUndocking. (#2999, #6823, #6780, #3492)
+- Docking: renamed ImGuiDockNodeFlags_NoSplit to ImGuiDockNodeFlags_NoDockingSplit.
+- Docking: renamed ImGuiDockNodeFlags_NoDockingInCentralNode to ImGuiDockNodeFlags_NoDockingOverCentralNode.
+- Docking: Internals: renamed ImGuiDockNodeFlags_NoDockingSplitMe to ImGuiDockNodeFlags_NoDockingSplit.
+- Docking: Fixed a bug where ClassId compare tests (when using SetNextWindowClass) on success would
+  prevent further filter from running, namely the one that prevent docking over a popup.
+- Backends: GLFW: Fixed an assertion in situation where the WndProc handler is different between
+  main and secondary viewport (may happen due to third-party hooks). (#6889)
+- Backends: DX9: Fixed incorrect assert triggering on reopening session with minimized windows. (#3424)
+
 
 -----------------------------------------------------------------------
  VERSION 1.89.9 (Released 2023-09-04)
@@ -724,6 +806,11 @@
 - Examples: Emscripten+WebGPU: Fixed WGPUInstance creation process + use preferred
   framebuffer format. (#6640, #6748) [@smileorigin]
 
+Docking+Viewports Branch:
+
+- Docking: when io.ConfigDockingWithShift is enabled, staying stationary while moving
+  a window displays an help tooltip to increase affordance. (#6709, #4643)
+
 
 -----------------------------------------------------------------------
  VERSION 1.89.8 (Released 2023-08-01)
@@ -792,6 +879,16 @@
 - Examples: Vulkan: Creating minimal descriptor pools to fit only what is needed by
   example. (#6642) [@SaschaWillem]
 
+Docking+Viewports Branch:
+
+- Docking, Style: resizing separators use same colors as window borders (ImGuiCol_Border)
+  for consistency. With default styles it doesn't make a big difference. (#2522) [@rmitton]
+  In the future if we promote using thick value for inner/outer docking padding we may
+  need to introduce new colors for it.
+- Docking: added style.DockingSeparatorSize, ImGuiStyleVar_DockingSeparatorSize. Now
+  also scaled by style.ScaleAllSizes(). (#3481, #4721, #2522) [@PossiblyAShrub, @wobbier]
+- Docking: fixed rendering of docked-window scrollbar above outer border. (#2522)
+
 
 -----------------------------------------------------------------------
  VERSION 1.89.7 (Released 2023-07-04)
@@ -887,6 +984,23 @@
 - Examples: Win32+OpenGL3: Changed DefWindowProc() to DefWindowProcW() to match other examples
   and support the example app being compiled without UNICODE. (#6516, #5725, #5961, #5975) [@yenixing]
 
+Docking+Viewports Branch:
+
+- Viewports+Docking: Fixed extraneous viewport+platform-window recreation in various
+  combination of showing or hiding windows, docking with/without split, undocking.
+  While with some backends and without OS decorations, some extraneous window recreation
+  were visibly not noticeable, they would typically become noticeable when enabling
+  OS decorations on those windows (e.g. Windows title bar fade-in/animation).
+- Viewports: Closing a viewport via OS/platform means (e.g. OS close button or task-bar menu),
+  mark all windows in this viewport as closed.
+- Docking: Fixed one-frame flickering on reappearing windows binding to a dock node
+  where a later-submitted window was already bound.
+- Docking: Fixed dragging from title-bar empty space (regression from 1.88 related to
+  keeping ID alive when calling low-level ButtonBehavior() directly). (#5181, #2645)
+- Docking: [Internal] DockBuilderDockWindow() API calls don't clear docking order
+  if the target node is same as existing one.
+- Backends: Win32: Added support for changing ParentViewportID after viewport creation.
+
 
 -----------------------------------------------------------------------
  VERSION 1.89.6 (Released 2023-05-31)
@@ -956,6 +1070,23 @@
 - Examples: Added SDL3+SDL_Renderer example. (#6286)
 - Examples: Updated all Visual Studio projects and batches to use /utf-8 argument.
 
+Docking+Viewports Branch:
+
+- Viewports: Fixed platform-side focus (e.g. Alt+Tab) from leading to accidental
+  closure of Modal windows. Regression from 1.89.5. (#6357, #6299)
+- Viewports: Fixed loss of imgui-side focus when dragging a secondary viewport back in
+  main viewport, due to platform-side handling changes. Regression from 1.89.5 (#6299)
+- Viewports: Avoid applying imgui-side focus when focus change is due to a viewport
+  destruction. Fixes erroneous popup closure on closing a previous popup. (#6462, #6299)
+- Viewports: Added void* ImGuiPlatformMonitor::PlatformHandle field (backend-dependant),
+  for usage by user code.
+- Backends: GLFW: Preserve monitor list when there are no monitor, may briefly
+  happen when recovering from macOS sleeping mode. (#5683) [@Guistac]
+- Backends: SDL2: Update monitor list when receiving a display event. (#6348)
+  Note however that SDL2 currently doesn't have an event for a DPI/Scaling change,
+  so monitor data won't be updated in this situation.
+- Backends: SDL3: Update monitor list when receiving a display event. (#6348)
+
 
 -----------------------------------------------------------------------
  VERSION 1.89.5 (Released 2023-04-13)
@@ -1013,7 +1144,6 @@
   is to other IME function such as SDL_SetTextInputRect(). (#6306, #6071, #1953)
 - Backends: GLFW: Added support on Win32 only for io.AddMouseSourceEvent() to discriminate
   Mouse/TouchScreen/Pen. (#2334, #2702)
-- Backends: GLFW: Fixed key modifiers handling on secondary viewports. (#6248, #6034) [@aiekick]
 - Backends: Android: Added support for io.AddMouseSourceEvent() to discriminate Mouse/TouchScreen/Pen.
   (#6315) [@PathogenDavid]
 - Backends: OSX: Added support for io.AddMouseSourceEvent() to discriminate Mouse/Pen.
@@ -1029,6 +1159,16 @@
 - TestSuite: Added variety of new regression tests and improved/amended existing ones
   in imgui_test_engine/ repo. [@PathogenDavid, @ocornut]
 
+Docking+Viewports Branch:
+
+- Viewports: Setting focus from Platform/OS (e.g. via decoration, or Alt-Tab) sets corresponding
+  focus at Dear ImGui level (generally last focused window in the viewport). (#6299)
+- Docking: Fixed using GetItemXXX() or IsItemXXX() functions after a DockSpace(). (#6217)
+- Backends: GLFW: Fixed key modifiers handling on secondary viewports. (#6248, #6034) [@aiekick]
+- Backends: GLFW: Fixed Emscripten erroneously enabling multi-viewport support, leading to assert. (#5683)
+- Backends: SDL2/SDL3: Fixed IME text input rectangle position with viewports. (#6071, #1953)
+- Backends: SDL3: Fixed for compilation with multi-viewports. (#6255) [@P3RK4N]
+
 
 -----------------------------------------------------------------------
  VERSION 1.89.4 (Released 2023-03-14)
@@ -1103,7 +1243,6 @@
   and ImGuiConfigFlags_NavEnableGamepad by default. (#787)
 - Internals: Misc tweaks to facilitate applying an explicit-context patch. (#5856) [@Dragnalith]
 
-
 -----------------------------------------------------------------------
  VERSION 1.89.3 (Released 2023-02-14)
 -----------------------------------------------------------------------
@@ -1204,6 +1343,10 @@
 - Examples: SDL2+SDL_Renderer: Added call to SDL_RenderSetScale() to fix display on a
   Retina display (albeit lower-res as our other unmodified examples). (#6121, #6065, #5931).
 
+Docking+Viewports Branch:
+
+- Backends: GLFW: Handle unsupported glfwGetVideoMode() for Emscripten. (#6096)
+
 
 -----------------------------------------------------------------------
  VERSION 1.89.2 (Released 2023-01-05)
@@ -1254,6 +1397,17 @@
 - Backends: Vulkan: Fixed sampler passed to ImGui_ImplVulkan_AddTexture() not being honored as we were using
   an immutable sampler. (#5502, #6001, #914) [@martin-ejdestig, @rytisss]
 
+Docking+Viewports Branch:
+
+- Docking: Internals: fixed DockBuilderCopyDockSpace() crashing when windows not in the
+  remapping list are docked on the left or top side of a split. (#6035)
+- Docking: fixed DockSpace() with ImGuiDockNodeFlags_KeepAliveOnly marking current window
+  as written to, even if it doesn't technically submit an item. This allow using KeepAliveOnly
+  from any window location. (#6037)
+- Backends: OSX: fixed typo in ImGui_ImplOSX_GetWindowSize that would cause issues when resiing
+  from OS decorations, if they are enabled on secondary viewports. (#6009) [@sivu]
+- Backends: Metal: fixed secondary viewport rendering. (#6015) [@dmirty-kuzmenko]
+
 
 -----------------------------------------------------------------------
  VERSION 1.89.1 (Released 2022-11-24)
@@ -1280,6 +1434,13 @@
 - Backends: GLFW: cancel out errors emitted by glfwGetKeyName() when a name is missing. (#5908)
 - Backends: WebGPU: fixed validation error with default depth buffer settings. (#5869, #5914) [@kdchambers]
 
+Docking+Viewports Branch:
+
+- Viewports: Fixed collapsed windows setting ImGuiViewportFlags_NoRendererClear without
+  making title bar color opaque, leading to potential texture/fb garbage being visible.
+  Right now as we don't fully support transparent viewports (#2766), so we turn that
+  'TitleBgCollapsed' color opaque just lke we do for 'WindowBG' on uncollapsed windows.
+
 
 -----------------------------------------------------------------------
  VERSION 1.89 (Released 2022-11-15)
@@ -1471,6 +1632,23 @@
 - Backends: Vulkan: Added experimental ImGui_ImplVulkan_RemoveTexture() for api symmetry. (#914, #5738).
 - Backends: WebGPU: fixed rendering when a depth buffer is enabled. (#5869) [@brainlag]
 
+Docking+Viewports Branch:
+
+- Docking: Fixed incorrect focus highlight on docking node when focusing a menu. (#5702)
+- Docking, Nav: Fixed using gamepad/keyboard navigation not being able enter menu layer when
+  it only contained the standard Collapse/Close buttons and no actual menu. (#5463, #4792)
+- Docking: Fixed regression introduced in v1.87 when docked window content not rendered
+  while switching between with CTRL+Tab. [@rokups]
+- Docking: Fixed amending into an existing tab bar from rendering invisible items. (#5515)
+- Docking: Made spacing between dock nodes not a dropping gap. When hovering it only
+  outer-docking drop markers are visible.
+- Docking+Viewports: Fixed undocking window node causing parent viewports to become unresponsive
+  in certain situation (e.g. hidden tab bar). (#5503) [@rokups]
+- Backends: SDL: Fixed building backend under non-OSX Apple targets (e.g. iPhone). (#5665)
+- Backends: SDL: Fixed drag'n drop crossing a viewport border losing mouse coordinates. (#5710, #5012)
+- Backends: GLFW: Fixed leftover static variable preventing from changing or
+  reinitializing backend while application is running. (#4616, #5434) [@rtoumazet]
+
 
 -----------------------------------------------------------------------
  VERSION 1.88 (Released 2022-06-21)
@@ -1605,6 +1783,26 @@
 - Examples: Emscripten+WebGPU: Fix building for latest WebGPU specs. (#3632)
 - Examples: OSX+Metal, OSX+OpenGL: Removed now-unnecessary calls to ImGui_ImplOSX_HandleEvent(). (#4821)
 
+Docking+Viewports Branch:
+
+- Docking: Fixed floating docked nodes not being clamped into viewport workrect to stay reachable
+  when io.ConfigWindowsMoveFromTitleBarOnly is true and multi-viewports are disabled. (#5044)
+- Docking: Fixed a regression where moving window would be interrupted after undocking a tab
+  when io.ConfigDockingAlwaysTabBar is true. (#5324) [@rokups]
+- Docking: Fixed incorrect focus highlight on docking node when focusing empty central node
+  or a child window which was manually injected into a dockspace window.
+- Docking, Modal: Fixed a crash when opening popup from a parent which is being docked on the same frame. (#5401)
+- Viewports: Fixed an issue where MouseViewport was lagging by a frame when using 1.87 Input Queue.
+  A common side-effect would be that when releasing a window drag the underlying window would highlight
+  for a frame. (#5837, #4921) [@cfillion]
+- Viewports: Fixed translating a host viewport from briefly altering the size of AlwaysAutoResize windows. (#5057)
+- Viewports: Fixed main viewport size not matching ImDrawData::DisplaySize for one frame during resize
+  when multi-viewports are disabled. (#4900)
+- Backends: SDL: Fixed dragging out main viewport broken on some SDL setups. (#5012) [@rokups]
+- Backends: OSX: Added support for multi-viewports. [@stuartcarnie, @metarutaiga] (#4821, #2778)
+- Backends: Metal: Added support for multi-viewports. [@stuartcarnie, @metarutaiga] (#4821, #2778)
+- Examples: OSX+Metal, SDL+Metal, GLFW+Metal: Added support for multi-viewports. [@rokups]
+
 
 -----------------------------------------------------------------------
  VERSION 1.87 (Released 2022-02-07)
@@ -1747,6 +1945,29 @@
 - Backends: WebGPU: Fixed incorrect size parameters in wgpuRenderPassEncoderSetIndexBuffer() and
   wgpuRenderPassEncoderSetVertexBuffer() calls. (#4891) [@FeepsDev]
 
+Docking+Viewports Branch:
+
+- Docking: Fixed a CTRL+TAB crash when aiming at an empty docked window. (#4792)
+- Docking: Tabs use their own identifier instead of the Window identifier.
+  (This will invalidate some stored .ini data such as last selected tab, sorry!)
+- Docking: Fixed size constraints not working on single window holding on a dock id (still doesn't work on docked windows).
+- Docking: Fixed CTRL+TAB back into a docked window not selecting menu layer when no item are on main layer.
+- Viewports, IO: Added io.AddMouseViewportEvent() function to queue hovered viewport change (when known by backend).
+- Viewports: Relaxed specs for backend supporting ImGuiBackendFlags_HasMouseHoveredViewport: it is now _optional_
+  for the backend to have to ignore viewports with the _NoInputs flag when call io.AddMouseViewportEvent(). It is
+  much better if they can (Win32 and GLFW 3.3+ backends can, SDL and GLFW 3.2 backends cannot, they are lacking data).
+  A concrete example is: when dragging a viewport for docking, the viewport is marked with _NoInputs to allow us
+  to pick the target viewports for docking. If the backend reports a viewport with _NoInputs when calling the
+  io.AddMouseViewportEvent() function, then Dear ImGui will revert to its flawed heuristic to find the viewport under.
+  By lowering those specs, we allow the SDL and more backend to support this, only relying on the heuristic in a few
+  drag and drop situations rather that relying on it everywhere.
+- Viewports: Fixed a CTRL+TAB crash with viewports enabled when the window list needs to appears in
+  its own viewport (regression from 1.86). (#4023, #787)
+- Viewports: Fixed active InputText() from preventing viewports to merge. (#4212)
+- Backends: SDL: Added support for ImGuiBackendFlags_HasMouseHoveredViewport now that its specs have been lowered.
+- (Breaking) Removed ImGuiPlatformIO::Platform_SetImeInputPos() in favor of newly standardized
+  io.SetPlatformImeDataFn() function. Should not affect more than default backends.
+
 
 -----------------------------------------------------------------------
  VERSION 1.86 (Released 2021-12-22)
@@ -1845,6 +2066,24 @@
   wgpuRenderPassEncoderSetIndexBuffer() functions as validation layers appears to not do what the
   in-flux specs says. (#4766) [@meshula]
 
+Docking+Viewports Branch:
+
+- Docking: Revert removal of io.ConfigDockingWithShift config option (removed in 1.83). (#4643)
+- Docking: Fixed a bug undocking windows docked into a non-visible or _KeepAliveOnly dockspace
+  when unrelated windows submitted before the dockspace have dynamic visibility. (#4757)
+- Docking, Style: Docked windows honor ImGuiCol_WindowBg. (#2700, #2539)
+- Docking, Style: Docked windows honor display their border properly. (#2522)
+- Docking: Fixed incorrectly rounded tab bars for dock node that are not at the top of their dock tree.
+- Docking: Fixed single-frame node pos/size inconsistencies when window stop or start being submitted.
+- Docking: Prevent docking any window created above a popup/modal. (#4317)
+- Viewports: Made it possible to explicitly assign ImGuiWindowClass::ParentViewportId to 0 in order
+  to ensure a window is not parented. Previously this would use the global default (which might be 0,
+  but not always as it would depend on io.ConfigViewportsNoDefaultParent). (#3152, #2871)
+- Viewports: Fixed tooltip in own viewport over modal from being incorrectly dimmed. (#4729)
+- Viewports: Fixed CTRL+TAB highlight outline on docked windows not always fitting in host viewport.
+- Backends: Made it possible to shutdown default Platform Backends before the Renderer backends. (#4656)
+- Disabled: Fixed nested BeginDisabled()/EndDisabled() bug in Docking branch due to bad merge. (#4655, #4452, #4453, #4462)
+
 
 -----------------------------------------------------------------------
  VERSION 1.85 (Released 2021-10-12)
@@ -1863,6 +2102,10 @@
   Can use 'GetWindowContentRegionMax().x - GetWindowContentRegionMin().x' instead but it's not
   very useful in practice, and the only use of it in the demo was illfit.
   Using 'GetContentRegionAvail().x' is generally a better choice.
+- (Docking branch) IsWindowFocused() and IsWindowHovered() with only the _ChildWindows flag
+  and without the _RootWindow flag used to leak docking hierarchy, so a docked window would
+  return as the child of the window hosting the dockspace. This was inconsistent and incorrect
+  with other behaviors so we fixed it. Added a new _DockHierarchy flag to opt-in this behavior.
 
 Other Changes:
 
@@ -1936,6 +2179,29 @@
 - Backends: All renderers: Normalize clipping rect handling across backends. (#4464)
 - Examples: Added SDL + SDL_Renderer example in "examples/example_sdl_sdlrenderer/" folder. (#3926) [@1bsyl]
 
+Docking+Viewports Branch:
+
+- IsWindowFocused: Fixed using ImGuiFocusedFlags_ChildWindows (without _RootWindow) from leaking the
+  docking hierarchy. Added ImGuiFocusedFlags_DockHierarchy flag to consider docking hierarchy in the test.
+- IsWindowHovered: Fixed using ImGuiHoveredFlags_ChildWindows (without _RootWindow) from leaking the
+  docking hierarchy. Added ImGuiHoveredFlags_DockHierarchy flag to consider docking hierarchy in the test.
+- Nav: Fixed an issue with losing focus on docked windows when pressing Alt while keyboard navigation
+  is disabled. (#4547, #4439) [@PathogenDavid]
+- Docking: Fixed IsItemHovered() and functions depending on it (e.g. BeginPopupContextItem()) when
+  called after Begin() on a docked window (broken 2021/03/04). (#3851)
+- Docking: Improved resizing system so that non-central zone are better at keeping their fixed size.
+  The algorithm is still not handling the allocation of size ideally for nested sibling, but it got better.
+- Docking: Fixed settings load issue when mouse wheeling. (#4310)
+- Docking: Fixed manually created floating node with a central node from not hiding when windows are gone.
+- Docking + Drag and Drop: Fixed using BeginDragDropSource() or BeginDragDropTarget() inside a Begin()
+  that returned false because the window is docked. (#4515)
+- Viewports: Fixed a crash while a window owning its viewport disappear while being dragged.
+  It would manifest when e.g. reconfiguring dock nodes while dragging.
+- Viewports: Fixed unnecessary creation of temporary viewports when multiple docked windows
+  got reassigned to a new node (created mid-frame) which already has a HostWindow.
+- Viewports: Fixed window with viewport ini data immediately merged into a host viewport from
+  leaving a temporary viewport alive for a frame (would leak into backend).
+
 
 -----------------------------------------------------------------------
  VERSION 1.84.2 (Released 2021-08-23)
@@ -2072,6 +2338,25 @@
 - Examples: Updated all .vcxproj to VS2015 (toolset v140) to facilitate usage with vcpkg.
 - Examples: SDL2: Accommodate  for vcpkg install having headers in SDL2/SDL.h vs SDL.h.
 
+Docking+Viewports Branch:
+
+- Docking: Clicking on the right-most close button of a docking node closes all windows. (#4186)
+- Docking: Fix IsWindowAppearing() and ImGuiCond_Appearing on docked windows. (#4177, #3982, #1497, #1061)
+- Docking: Fix crash using DockBuilderRemoveNode() in some situations. (#3111, #3179, #3203, #4295) [@hsimyu]
+- Docking: Fix crash when a dock node gets re-qualified as dockspace>floating>dockspace, which tends to happen
+  when incorrectly calling DockBuilderAddNode() without ImGuiDockNodeFlags_Dockspace and using it as a Dockspace
+  on the next frame after the floating window hosting the node has been automatically created. (#3203, #4295)
+- Docking: Reworked node flags saving/inheritance so that flags enforced by docked windows via the
+  DockNodeFlagsOverrideSet mechanism are are not left in empty dockspace nodes once the windows gets undocked.
+  (#4292, #3834, #3633, #3521, #3492, #3335, #2999, #2648)
+- Docking: (Internal/Experimental) Removed DockNodeFlagsOverrideClear flags from ImGuiWindowClass as
+  it is ambiguous how to apply them and we haven't got a use out of them yet.
+- Docking: Fixed ImGuiWindowFlags_UnsavedDocument clipping label in docked windows when there are
+  no close button. (#5745)
+- Viewports: Fix popup/tooltip created without a parent window from being given a ParentViewportId value
+  from the implicit/fallback window. (#4236, #2409)
+- Backends: Vulkan: Fix the use of the incorrect fence for secondary viewports. (#4208) [@FunMiles]
+
 
 -----------------------------------------------------------------------
  VERSION 1.83 (Released 2021-05-24)
@@ -2156,6 +2441,22 @@
 - Docs: Improvements to description of using colored glyphs/emojis. (#4169, #3369)
 - Docs: Improvements to minor mistakes in documentation comments (#3923) [@ANF-Studios]
 
+Docking+Viewports Branch:
+
+- [Breaking] Removed io.ConfigDockingWithShift config option. Behavior always equivalent to having the
+  option set to false (dock/undock by default, hold shift to avoid docking). (#2109)
+- Docking: DockSpace() returns its node ID.
+- Docking: Dockspace() never draws a background. (#3924)
+- Docking: Undocking nodes/windows covering most of the monitor max their size down to 90% to ease manipulations.
+- Docking: Docking node tab bar honors ItemInnerSpacing.x before first tab. (#4130)
+- Docking: Tweak rendering and alignment of dock node menu marker. (#4130)
+- Docking: Fixed restoring of tab order within a dockspace or a split node.
+- Docking: Fixed reappearing docked windows with no close button showing a tab with extraneous space for one frame.
+- Docking: Fixed multiple simultaneously reappearing window from appearing undocked for one frame.
+- Viewports: Hotfix for crash in monitor array access, caused by 4b9bc4902. (#3967)
+- Backends, Viewports: GLFW: Add a workaround for stuck keys after closing a GLFW window (#3837).
+- Backends, Viewports: Vulkan: Rebuild swapchain on VK_SUBOPTIMAL_KHR. (#3881)
+
 
 -----------------------------------------------------------------------
  VERSION 1.82 (Released 2021-02-15)
@@ -2251,6 +2552,13 @@
   scheduled builds builds are not required. [@rokups]
 - Log/Capture: Added LogTextV, a va_list variant of LogText. [@PathogenDavid]
 
+Docking+Viewports Branch:
+
+- Viewports: Fix setting of ImGuiViewportFlags_NoRendererClear. (#3213)
+- Viewports: Added GetViewportPlatformMonitor() with a safety net to keep code portable.
+- Viewports, Backends: SDL: Fix missing ImGuiBackendFlags_HasSetMousePos flag in docking branch.
+- Viewports, Backends: GLFW: Fix application of WantSetMousePos. (#1542, #787)
+
 
 -----------------------------------------------------------------------
  VERSION 1.81 (Released 2021-02-10)
@@ -2332,6 +2640,17 @@
 - Examples: WebGPU: Added Emscripten+WebGPU example. (#3632) [@bfierz]
 - Backends: GLFW: Added ImGui_ImplGlfw_InitForOther() initialization call to use with non OpenGL API. (#3632)
 
+Docking+Viewports Branch:
+
+- Docking: Fix losing docking information on closed windows for which the hosting node was split. (#3716) [@GamingMinds-DanielC]
+- Docking: Fix gap in hit test hole when using ImGuiDockNodeFlags_PassthruCentralNode touching the edge of a viewport. (#3733)
+- Viewports: (Breaking) removed ImGuiPlatformIO::MainViewport which is now pretty much unused and duplicate
+  (and misleading as we will evolve the concept).
+- Viewports: (Breaking) turned ImGuiViewport::GetWorkPos(), ImGuiViewport::GetWorkSize() into regular fields
+  (WorkPos, WorkSize) before exposing in master branch.
+- Viewports: Fix issue inferring viewport z-order when new popups gets created. (#3734) + Metrics updates.
+- Viewports, Backends: Vulkan: handle VK_ERROR_OUT_OF_DATE_KHR when resizing secondary viewport (#3766, #3758)
+
 
 -----------------------------------------------------------------------
  VERSION 1.80 (Released 2021-01-21)
@@ -2451,6 +2770,14 @@
 - Docs: Split examples/README.txt into docs/BACKENDS.md and docs/EXAMPLES.md, and improved them.
 - Docs: Consistently renamed all occurrences of "binding" and "back-end" to "backend" in comments and docs.
 
+Docking+Viewports Branch:
+
+- Docking: Docked windows honor change of tab and text colors. (#2771)
+- Docking: Support for appending into existing tab-bar made to work with Docking + internal helper DockNodeBeginAmendTabBar().
+- Docking: Added experimental TabItemFlagsOverrideSet to ImGuiWindowClass.
+- Viewports: Fixed incorrect whitening of popups above a modal if both use their own viewport.
+- Viewports: Backends: Vulkan: Fixed build, removed extraneous pipeline creation. (#3459, #3579)
+
 
 -----------------------------------------------------------------------
  VERSION 1.79 (Released 2020-10-08)
@@ -2545,6 +2872,21 @@
 - Examples: DX12: Added '#define ImTextureID ImU64' in project and build files to also allow building
   on 32-bit systems. Added project to default Visual Studio solution file. (#301)
 
+Docking+Viewports Branch:
+
+- Docking: DockSpace() emits ItemSize() properly (useful when not filling all space).
+- Docking: Fixed docking while hovering a child window. (#3420) broken by 85a661d. Improve metrics debugging.
+- Docking: Fix honoring payload filter with overlapping nodes (we incorrectly over-relied on g.HoveredDockNode
+  when making change for #3398).
+- Docking: Fix handling of WindowMenuButtonPosition == ImGuiDir_None in Docking Nodes. (#3499)
+- Viewports: Fixed a rare edge-case if the window targeted by CTRL+Tab stops being rendered.
+- Viewports, Backends: DX12: Make secondary viewport format match main viewport one (#3462) {@BeastLe9enD]
+- Viewports: Backends: Vulkan: Removed unused shader code. Fix leaks. Avoid unnecessary pipeline creation for main
+  viewport. (#3459) + Add ImGui_ImplVulkanH_CreateWindowSwapChain in ImGui_ImplVulkanH_CreateOrResizeWindow().
+- Viewports: Backends: DirectX9: Recover from D3DERR_DEVICELOST on secondary viewports. (#3424)
+- Viewports, Backends: Win32: Fix toggling of ImGuiViewportFlags_TopMost (#3477) [@Kodokuna]
+- Viewports: Backends: GLFW: Workaround for cases where glfwGetMonitorWorkarea fails (#3457) [@dougbinks]
+
 
 -----------------------------------------------------------------------
  VERSION 1.78 (Released 2020-08-18)
@@ -2646,6 +2988,23 @@
 - Examples: Vulkan: Fixed GLFW+Vulkan and SDL+Vulkan clear color not being set. (#3390) [@RoryO]
 - CI: Emscripten has stopped their support for their fastcomp backend, switching to latest sdk [@Xipiryon]
 
+Docking+Viewports Branch:
+
+- Docking: Made DockBuilderAddNode() automatically call DockBuilderRemoveNode(). (#3399, #2109)
+- Docking: Storing HoveredDockNode in context which can be useful for easily detecting e.g. hovering an
+  empty node. (#3398)
+- Docking: Fixed docking overlay bits appearing at (0,0), because of 43bd80a. Most typically noticeable
+  when disabling multi-viewport.
+- Docking: Workaround recovery for node created without the _DockSpace flags later becoming a DockSpace. (#3340)
+- Docking: Rework size allocations to recover when there's no enough room for nodes + do not hold on
+  _WantLockSizeOnce forever. (#3328)
+- Docking: Rework size allocation to allow user code to override node sizes. Not all edge cases will be
+  properly handled but this is a step toward toolbar emitting size constraints.
+- Docking: Added experimental flags to perform more docking filtering and disable resize per axis.
+  Designed for toolbar patterns.
+- Viewports, Backends, GLFW: Use GLFW_MOUSE_PASSTHROUGH when available.
+- Viewports, Backends: DX12: Fixed issue on shutdown when viewports are disabled. (#3347)
+
 
 -----------------------------------------------------------------------
  VERSION 1.77 (Released 2020-06-29)
@@ -2737,6 +3096,17 @@
 - Examples: Apple: Fixed example_apple_metal and example_apple_opengl2 using imgui_impl_osx.mm
   not forwarding right and center mouse clicks. (#3260) [@nburrus]
 
+Docking+Viewports Branch:
+
+- Viewports: Don't set ImGuiViewportFlags_NoRendererClear when ImGuiWindowFlags_NoBackground is set. (#3213)
+- Viewports: Report minimized viewports as zero DisplaySize to be consistent with main branch. (#1542)
+- Docking, Settings: Allow reload of settings data at runtime. (#2573)
+- Backends, GLFW: Fix windows resizing incorrectly on Linux due to GLFW firing window positioning
+  callbacks on next frame after window is resized manually. (#2117)
+- Backends: DX12: Fix OBJECT_DELETED_WHILE_STILL_IN_USE on viewport resizing. (#3210)
+- Backends: DX12: Fix for crash caused by early resource release. (#3121)
+- Backends, Win32: Request monitor update when DPI awareness is enabled to make sure they have the correct DPI settings.
+
 
 -----------------------------------------------------------------------
  VERSION 1.76 (Released 2020-04-12)
@@ -2809,6 +3179,20 @@
 - Examples: SDL+DX11: Fixed resizing main window. (#3057) [@joeslay]
 - Examples: Added SDL+Metal example application. (#3017) [@coding-jackalope]
 
+Docking+Viewports Branch:
+
+- Docking: Fixed assert preventing dockspace from being created instead a hidden tab. (#3101)
+- Viewports: Fixed secondary viewports accidentally merging into a minimized host viewport. (#3118)
+- Viewports, Docking: Added per-viewport work area system for e.g. menu-bars. Fixed DockspaceOverViewport()
+  and demo code (overlay etc) accordingly. (#3035, #2889, #2474, #1542, #2109)
+- Viewports: Improve menu positioning in multi-monitor setups. [@rokups]
+- Viewports: Software mouse cursor is also scaled by current DpiScale. (amend #939)
+- Viewports: Avoid manually clipping resize grips and borders, which messes up with automation ability
+  to locate those items. Also simpler and more standard.
+- Viewports: Fix for UWP in the imgui_impl_win32.cpp IME handler. (#2895, #2892).
+- Viewports: Bunch of extra of comments to facilitate setting up multi-viewports.
+- Viewports, GLFW: Avoid using window positioning workaround for GLFW 3.3+ versions that have it fixed.
+
 
 -----------------------------------------------------------------------
  VERSION 1.75 (Released 2020-02-10)
@@ -2907,6 +3291,21 @@
 - Examples: Metal: Wrapped main loop in @autoreleasepool block to ensure allocations get freed
   even if underlying system event loop gets paused due to app nap. (#2910, #2917) [@bear24rw]
 
+Docking+Viewports Branch:
+
+- Docking + Nav: Fixed messed up Ctrl+Tab order with docked windows.
+- Docking + Nav: Fixed failing to restore NavId when refocusing a child within a docked window.
+- Docking + Nav: Fixed failing to restore NavId when refocusing due to missing nav window (when
+  it stops being submitted).
+- Docking: Fixed a bug where the tab bar of a hidden dockspace would keep requesting focus. (#2960)
+- Docking: Added experimental DockNodeFlagsOverrideSet/DockNodeFlagsOverrideClear flags in ImGuiWindowClass
+  (currently experimenting with toolbar idioms).
+- Viewports: Fix resizing viewport-owning windows when mouse pos is outside the InnerClipRect
+  (can happen with OS decoration enabled).
+- Viewports: Preserve last known size for minimized main viewport to be consistent with secondary viewports.
+- Backends: SDL: Honor NoTaskBarIcon flag under non Win32 OS. (#2117)
+- Backends: GLFW, SDL: Platform monitors declared properly even if multi-viewport is not enabled.
+
 
 -----------------------------------------------------------------------
  VERSION 1.74 (Released 2019-11-25)
@@ -2986,6 +3385,14 @@
 - CI: Set up a bunch of continuous-integration tests using GitHub Actions. We now compile many of the example
   applications on Windows, Linux, MacOS, iOS, Emscripten. Removed Travis integration. (#2865) [@rokups]
 
+Docking+Viewports Branch:
+
+- Docking: Can undock from the small triangle button. (#2109,. #2645)
+- Docking: Fixed node->HasCloseButton not honoring ImGuiDockNodeFlags_NoCloseButton in a floating node,
+  leading to empty space at the right of tab-bars with those flags. (#2109)
+- Docking: Made docked windows not use style.ChildRounding.
+- Multi-viewports: Added multi-viewport support in the DX12 back-end. (#2851) [@obfuscate]
+
 
 -----------------------------------------------------------------------
  VERSION 1.73 (Released 2019-09-24)
@@ -3048,6 +3455,28 @@
 - Misc: Updated stb_rect_pack.h from 0.99 to 1.00 (fixes by @rygorous: off-by-1 bug in best-fit heuristic,
   fix handling of rectangles too large to fit inside texture). (#2762) [@tido64]
 
+Docking+Viewports Branch:
+
+- Docking: Fix BeginDocked() path that creates node so that SetNextWindowDockID() doesn't immediately discard the node. (#2109)
+- Docking: Fix for node created at the same time as windows that are still resizing (typically with
+  io.ConfigDockingAlwaysTabBar) to not be zero/min sized. (#2109). The fix delays their visibility by one frame,
+  which is not ideal but not very problematic as the .ini data gets populated after that.
+- Docking: Fix a crash that could occur with a malformed ini file (DockNode Parent value pointing to a missing node).
+- Viewport: Fix modal/popup window being stuck in unowned hidden viewport associated to fallback window without stealing
+  it back. Fix modal reference viewport when opened outside of another window. (#1542)
+- Viewport: Modals don't need to set ImGuiViewportFlags_NoFocusOnClick, this also mitigate the issue described by #2445,
+  which becomes particularly bad with unfocused modal. (#1542)
+- Viewport: better case case where host window gets moved and resized simultaneous (toggling maximized state).
+  There's no perfect solution there, than using io.ConfigViewportsNoAutoMerge = false. (#1542)
+- Viewport, Docking: Fixed incorrect assignment of IsFallbackWindow which would tag dock node host windows created
+  in NewFrame() as such, messing with popup viewport inheritance.
+- Viewport: Fixed issue where resize grip would display as hovered while mouse is still off the OS bounds so a click
+  would miss it and focus the OS window behind expected one. (#1542)
+- Viewport: Fix to allow multiple shutdown / calls to DestroyPlatformWindows(). (#2769)
+- Viewport: Backends: GLFW: Fix setting window size on macOS (#2767, #2117) [@rokups]
+- Viewport: Backends: GLFW+Linux: Fix window having incorrect size after uncollapse. (#2756, #2117) [@rokups]
+- Viewport: Backends: DirectX9: Workaround for windows not refreshing when main viewport has no draw call. (#2560)
+
 
 -----------------------------------------------------------------------
  VERSION 1.72b (Released 2019-07-31)
@@ -3150,6 +3579,25 @@
   (#2482, #2632) [@josiahmanson]
 - Examples: Added SDL2+DirectX11 example application. (#2632, #2612, #2482) [@vincenthamm]
 
+Docking+Viewports Branch:
+
+- Docking: Making it possible to undock a node by clicking on the tab bar / title bar for the node. (#2645).
+- Docking: Explicitly inhibit constraint when docked for now. Fix clipping issue related to constraints. (#2690).
+- Docking: Fixed dragging/resizing from OS decoration not marking settings as dirty.
+- Docking: Renamed io.ConfigDockingTabBarOnSingleWindows to io.ConfigDockingAlwaysTabBar.
+  Added ImGuiWindowClass::DockingAlwaysTabBar to set on individual windows.
+- Docking: Perform simple check: assert if Docking or Viewport are enabled exactly on frame 1 (instead of frame 0
+  or later), which is a common user error leading to loss of .ini data on load.
+- Docking: Fix so that an appearing window making a dock node reappear won't have a zero-size on its first frame.
+- Docking: Fixed using ImGuiDockNodeFlags_AutoHideTabBar with io.ConfigDockingTabBarOnSingleWindows.
+- Docking: Added ImGuiDockNode to .natvis file.
+- Docking: Fixed support for large meshes in GetBackgroundDrawList(), GetForegroundDrawList(). (#2638)
+- Viewport: Fix monitor dpi info not being copied to main viewport when multi-viewports are not enabled. (#2621, #1676)
+- Viewport: Refactored ImGuiWindowClass's ViewportFlagsOverrideMask + ViewportFlagsOverrideValue into
+  ViewportFlagsOverrideSet + ViewportFlagsOverrideClear which appears easier to grasp. (#1542)
+- Viewport: Added ImGuiViewportFlags_NoAutoMerge to prevent merging into host viewport in a per-window basis
+  via the ImGuiWindowClass override mechanism. (#1542)
+
 
 -----------------------------------------------------------------------
  VERSION 1.71 (Released 2019-06-12)
@@ -3489,6 +3937,7 @@
 - Renamed ImFontAtlas::GlyphRangesBuilder to ImFontGlyphRangesBuilder. Kept redirection typedef (will obsolete).
 
 Other Changes:
+
 - Added BETA api for Tab Bar/Tabs widgets: (#261, #351)
   - Added BeginTabBar(), EndTabBar(), BeginTabItem(), EndTabItem(), SetTabItemClosed() API.
   - Added ImGuiTabBarFlags flags for BeginTabBar().
diff --git a/docs/TODO.txt b/docs/TODO.txt
index 80f4e30..4df57e5 100644
--- a/docs/TODO.txt
+++ b/docs/TODO.txt
@@ -129,7 +129,35 @@
  - separator: width, thickness, centering (#1643, #2657)
  - splitter: formalize the splitter idiom into an official api (we want to handle n-way split) (#319)
 
- - docking: merge docking branch (#2109)
+ - docking: B: ordering currently held in tab bar should be implicitly held by windows themselves (also see #2304)
+ - docking: B- tab bar: the order/focus restoring code could be part of TabBar and not DockNode? (#8)
+ - docking: B~ rework code to be able to lazily create tab bar instance in a single place. The _Unsorted tab flag could be replacing a trailing-counter in DockNode?
+ - docking: B~ fully track windows/settings reference in dock nodes. perhaps find a representation that allows facilitate use of dock builder functions.
+ - docking: B~ Unreal style document system (requires low-level controls of dockspace serialization fork/copy/delete). this is mostly working but the DockBuilderXXX api are not exposed/finished.
+ - docking: B: when docking outer, perform size locking on neighbors nodes the same way we do it with splitters, so other nodes are not resized.
+ - docking: B~ central node resizing behavior incorrect.
+ - docking: B: changing title font/style per-window is not supported as dock nodes are created in NewFrame.
+ - docking: B- dock node inside its own viewports creates 1 temporary viewport per window on startup before ditching them (doesn't affect the user nor request platform windows to be created, but unnecessary)
+ - docking: B- resize sibling locking behavior may be less desirable if we merged same-axis sibling in a same node level?
+ - docking: B- single visible node part of a hidden split hierarchy (OnlyNodeWithWindows != NULL) should show a normal title bar (not a tab bar)
+ - docking: B~ SetNextWindowDock() calls (with conditional) -> defer everything to DockContextUpdate (repro: Documents->[X]Windows->Dock 1 elsewhere->Click Redock All
+ - docking: B~ tidy up tab list popup buttons features (available with manual tab-bar, see ImGuiTabBarFlags_NoTabListPopupButton code, not used by docking nodes)
+ - docking: B- SetNextWindowDockId(0) with a second Begin() in the frame will asserts
+ - docking: B: resize grip drawn in host window typically appears under scrollbar.
+ - docking: B: resize grip auto-resize on multiple node hierarchy doesn't make much sense or should be improved?
+ - docking: B- SetNextWindowFocus() doesn't seem to apply if the window is hidden this frame, need repro (#4)
+ - docking: B- resizing a dock tree small currently has glitches (overlapping collapse and close button, etc.)
+ - docking: B- dpi: look at interaction with the hi-dpi and multi-dpi stuff.
+ - docking: B- tab bar: appearing on first frame with a dumb layout would do less harm that not appearing? (when behind dynamic branch) or store titles + render in EndTabBar()
+ - docking: B- tab bar: make selected tab always shows its full title?
+ - docking: B- hide close button on single tab bar?
+ - docking: B- nav: design interactions so nav controls can dock/undock
+ - docking: B- dockspace: flag to lock the dock tree and/or sizes (ImGuiDockNodeFlags_Locked?)
+ - docking: B- reintroduce collapsing a floating dock node. also collapsing a docked dock node!
+ - docking: B- allow dragging a non-floating dock node by clicking on the title-bar-looking section (not just the collapse/menu button)
+ - docking: B- option to remember undocked window size? (instead of keeping their docked size) (relate to #2104)
+ - docking: C- nav: CTRL+TAB highlighting tabs shows the mismatch between focus-stack and tab-order (not visible in VS because it doesn't highlight the tabs)
+ - docking: C- after a dock/undock, the Scrollbar Status update in Begin() should use an updated e.g. size_y_for_scrollbars to avoid a 1 frame scrollbar flicker.
 
  - tabs: "there is currently a problem because TabItem() will try to submit their own tooltip after 0.50 second, and this will have the effect of making your tooltip flicker once." -> tooltip priority work (WIP branch)
  - tabs: make EndTabBar fail if users doesn't respect BeginTabBar return value, for consistency/future-proofing.
@@ -303,6 +331,20 @@
  - nav/windowing: Resizing window will currently fail with certain types of resizing constraints/callback applied
  - focus: preserve ActiveId/focus stack state, e.g. when opening a menu and close it, previously selected InputText() focus gets restored (#622)
 
+ - viewport: make it possible to have no main/hosting viewport
+ - viewport: We set ImGuiViewportFlags_NoFocusOnAppearing in a way that is required for GLFW/SDL binding, but could be handled better without
+   on a custom e.g. Win32 bindings. It prevents newly dragged-out viewports from taking the focus, which makes ALT+F4 more ambiguous.
+ - viewport: not focusing newly undocked viewport means clicking back on previous one doesn't bring OS window to front.
+ - viewport: with platform decoration enabled, platform may force constraint (e.g. minimum size)
+ - viewport: use getfocus/setfocus api to synchronize imgui<>platform focus better (e.g imgui-side ctrl-tab can focus os window, OS initial setup and alt-tab can focus imgui window etc.)
+ - viewport: store per-viewport/monitor DPI in .ini file so an application reload or main window changing DPI on reload can be properly patched for.
+ - viewport: implicit/fallback Debug window can hog a zombie viewport (harmless, noisy?) > could at least clear out the reference on a per session basis?
+ - viewport: need to clarify how to use GetMousePos() from a user point of view.
+ - platform: glfw: no support for ImGuiBackendFlags_HasMouseHoveredViewport.
+ - platform: sdl: no support for ImGuiBackendFlags_HasMouseHoveredViewport. maybe we could use SDL_GetMouseFocus() / SDL_WINDOW_MOUSE_FOCUS if imgui could fallback on its heuristic when NoInputs is set
+ - platform: sdl: no refresh of monitor/display (SDL doesn't seem to have an event for it).
+ - platform: sdl: multi-viewport + minimized window seems to break mouse wheel events (at least under Win32).
+
  - inputs: support track pad style scrolling & slider edit.
  - inputs/io: backspace and arrows in the context of a text input could use system repeat rate.
  - inputs/io: clarify/standardize/expose repeat rate and repeat delays (#1808)
diff --git a/examples/example_allegro5/main.cpp b/examples/example_allegro5/main.cpp
index 3ca061c..298c845 100644
--- a/examples/example_allegro5/main.cpp
+++ b/examples/example_allegro5/main.cpp
@@ -40,6 +40,7 @@
     ImGui::CreateContext();
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;  // Enable Keyboard Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;      // Enable Docking
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
diff --git a/examples/example_apple_metal/example_apple_metal.xcodeproj/project.pbxproj b/examples/example_apple_metal/example_apple_metal.xcodeproj/project.pbxproj
index 4bb4fc2..3ebf9cc 100644
--- a/examples/example_apple_metal/example_apple_metal.xcodeproj/project.pbxproj
+++ b/examples/example_apple_metal/example_apple_metal.xcodeproj/project.pbxproj
@@ -7,7 +7,10 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		050450AB2768052600AB6805 /* imgui_tables.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 5079822D257677DB0038A28D /* imgui_tables.cpp */; };
+		050450AD276863B000AB6805 /* QuartzCore.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 050450AC276863B000AB6805 /* QuartzCore.framework */; };
 		05318E0F274C397200A8DE2E /* GameController.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 05318E0E274C397200A8DE2E /* GameController.framework */; };
+		05A275442773BEA20084EF39 /* QuartzCore.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 05A275432773BEA20084EF39 /* QuartzCore.framework */; };
 		07A82ED82139413D0078D120 /* imgui_widgets.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 07A82ED72139413C0078D120 /* imgui_widgets.cpp */; };
 		07A82ED92139418F0078D120 /* imgui_widgets.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 07A82ED72139413C0078D120 /* imgui_widgets.cpp */; };
 		5079822E257677DB0038A28D /* imgui_tables.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 5079822D257677DB0038A28D /* imgui_tables.cpp */; };
@@ -33,7 +36,11 @@
 /* End PBXBuildFile section */
 
 /* Begin PBXFileReference section */
+		050450AC276863B000AB6805 /* QuartzCore.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = QuartzCore.framework; path = System/Library/Frameworks/QuartzCore.framework; sourceTree = SDKROOT; };
 		05318E0E274C397200A8DE2E /* GameController.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = GameController.framework; path = System/Library/Frameworks/GameController.framework; sourceTree = SDKROOT; };
+		05A2754027728F5B0084EF39 /* imgui_impl_metal.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = imgui_impl_metal.h; path = ../../backends/imgui_impl_metal.h; sourceTree = "<group>"; };
+		05A2754127728F5B0084EF39 /* imgui_impl_osx.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = imgui_impl_osx.h; path = ../../backends/imgui_impl_osx.h; sourceTree = "<group>"; };
+		05A275432773BEA20084EF39 /* QuartzCore.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = QuartzCore.framework; path = Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS15.2.sdk/System/Library/Frameworks/QuartzCore.framework; sourceTree = DEVELOPER_DIR; };
 		07A82ED62139413C0078D120 /* imgui_internal.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = imgui_internal.h; path = ../../imgui_internal.h; sourceTree = "<group>"; };
 		07A82ED72139413C0078D120 /* imgui_widgets.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = imgui_widgets.cpp; path = ../../imgui_widgets.cpp; sourceTree = "<group>"; };
 		5079822D257677DB0038A28D /* imgui_tables.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = imgui_tables.cpp; path = ../../imgui_tables.cpp; sourceTree = "<group>"; };
@@ -66,6 +73,7 @@
 			isa = PBXFrameworksBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				05A275442773BEA20084EF39 /* QuartzCore.framework in Frameworks */,
 				8309BD8F253CCAAA0045E2A1 /* UIKit.framework in Frameworks */,
 				83BBE9E720EB46BD00295997 /* MetalKit.framework in Frameworks */,
 				83BBE9E520EB46B900295997 /* Metal.framework in Frameworks */,
@@ -76,6 +84,7 @@
 			isa = PBXFrameworksBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				050450AD276863B000AB6805 /* QuartzCore.framework in Frameworks */,
 				8309BDC6253CCCFE0045E2A1 /* AppKit.framework in Frameworks */,
 				83BBE9EC20EB471700295997 /* MetalKit.framework in Frameworks */,
 				05318E0F274C397200A8DE2E /* GameController.framework in Frameworks */,
@@ -136,6 +145,8 @@
 		83BBE9E320EB46B800295997 /* Frameworks */ = {
 			isa = PBXGroup;
 			children = (
+				050450AC276863B000AB6805 /* QuartzCore.framework */,
+				05A275432773BEA20084EF39 /* QuartzCore.framework */,
 				05318E0E274C397200A8DE2E /* GameController.framework */,
 				8309BDC5253CCCFE0045E2A1 /* AppKit.framework */,
 				8309BD8E253CCAAA0045E2A1 /* UIKit.framework */,
@@ -153,7 +164,9 @@
 			isa = PBXGroup;
 			children = (
 				5079822D257677DB0038A28D /* imgui_tables.cpp */,
+				05A2754027728F5B0084EF39 /* imgui_impl_metal.h */,
 				8309BDB5253CCC9D0045E2A1 /* imgui_impl_metal.mm */,
+				05A2754127728F5B0084EF39 /* imgui_impl_osx.h */,
 				8309BDB6253CCC9D0045E2A1 /* imgui_impl_osx.mm */,
 				83BBEA0420EB54E700295997 /* imconfig.h */,
 				83BBEA0320EB54E700295997 /* imgui.cpp */,
@@ -268,9 +281,9 @@
 				8309BDBB253CCCAD0045E2A1 /* imgui_impl_metal.mm in Sources */,
 				83BBEA0920EB54E700295997 /* imgui.cpp in Sources */,
 				83BBEA0720EB54E700295997 /* imgui_demo.cpp in Sources */,
-                83BBEA0520EB54E700295997 /* imgui_draw.cpp in Sources */,
+				83BBEA0520EB54E700295997 /* imgui_draw.cpp in Sources */,
 				5079822E257677DB0038A28D /* imgui_tables.cpp in Sources */,
-                07A82ED82139413D0078D120 /* imgui_widgets.cpp in Sources */,
+				07A82ED82139413D0078D120 /* imgui_widgets.cpp in Sources */,
 				8309BDA5253CCC070045E2A1 /* main.mm in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
@@ -281,10 +294,10 @@
 			files = (
 				8309BDBE253CCCB60045E2A1 /* imgui_impl_metal.mm in Sources */,
 				8309BDBF253CCCB60045E2A1 /* imgui_impl_osx.mm in Sources */,
-                83BBEA0A20EB54E700295997 /* imgui.cpp in Sources */,
-                83BBEA0820EB54E700295997 /* imgui_demo.cpp in Sources */,
-                83BBEA0620EB54E700295997 /* imgui_draw.cpp in Sources */,
-                5079822E257677DB0038A28D /* imgui_tables.cpp in Sources */,
+				83BBEA0A20EB54E700295997 /* imgui.cpp in Sources */,
+				83BBEA0820EB54E700295997 /* imgui_demo.cpp in Sources */,
+				83BBEA0620EB54E700295997 /* imgui_draw.cpp in Sources */,
+				050450AB2768052600AB6805 /* imgui_tables.cpp in Sources */,
 				07A82ED92139418F0078D120 /* imgui_widgets.cpp in Sources */,
 				8309BDA8253CCC080045E2A1 /* main.mm in Sources */,
 			);
diff --git a/examples/example_apple_metal/main.mm b/examples/example_apple_metal/main.mm
index 109ef61..d184dd6 100644
--- a/examples/example_apple_metal/main.mm
+++ b/examples/example_apple_metal/main.mm
@@ -60,11 +60,21 @@
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
+    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
     //ImGui::StyleColorsLight();
 
+    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
+    ImGuiStyle& style = ImGui::GetStyle();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        style.WindowRounding = 0.0f;
+        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
+    }
+
     // Setup Renderer backend
     ImGui_ImplMetal_Init(_device);
 
@@ -195,6 +205,13 @@
 	// Present
     [commandBuffer presentDrawable:view.currentDrawable];
     [commandBuffer commit];
+
+    // Update and Render additional Platform Windows
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        ImGui::UpdatePlatformWindows();
+        ImGui::RenderPlatformWindowsDefault();
+    }
 }
 
 -(void)mtkView:(MTKView*)view drawableSizeWillChange:(CGSize)size
diff --git a/examples/example_apple_opengl2/main.mm b/examples/example_apple_opengl2/main.mm
index 815c0f7..11829a8 100644
--- a/examples/example_apple_opengl2/main.mm
+++ b/examples/example_apple_opengl2/main.mm
@@ -47,11 +47,21 @@
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
+    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
     //ImGui::StyleColorsLight();
 
+    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
+    ImGuiStyle& style = ImGui::GetStyle();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        style.WindowRounding = 0.0f;
+        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
+    }
+
     // Setup Platform/Renderer backends
     ImGui_ImplOSX_Init(self);
     ImGui_ImplOpenGL2_Init();
@@ -136,6 +146,13 @@
 
     ImGui_ImplOpenGL2_RenderDrawData(draw_data);
 
+    // Update and Render additional Platform Windows
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        ImGui::UpdatePlatformWindows();
+        ImGui::RenderPlatformWindowsDefault();
+    }
+
     // Present
     [[self openGLContext] flushBuffer];
 
diff --git a/examples/example_glfw_metal/main.mm b/examples/example_glfw_metal/main.mm
index e9bc63a..2f346ff 100644
--- a/examples/example_glfw_metal/main.mm
+++ b/examples/example_glfw_metal/main.mm
@@ -33,11 +33,21 @@
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;  // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;   // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;      // Enable Docking
+    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;    // Enable Multi-Viewport / Platform Windows
 
     // Setup style
     ImGui::StyleColorsDark();
     //ImGui::StyleColorsLight();
 
+    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
+    ImGuiStyle& style = ImGui::GetStyle();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        style.WindowRounding = 0.0f;
+        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
+    }
+
     // Load Fonts
     // - If no fonts are loaded, dear imgui will use the default font. You can also load multiple fonts and use ImGui::PushFont()/PopFont() to select them.
     // - AddFontFromFileTTF() will return the ImFont* so you can store it if you need to select the font among multiple.
@@ -69,7 +79,7 @@
     id <MTLCommandQueue> commandQueue = [device newCommandQueue];
 
     // Setup Platform/Renderer backends
-    ImGui_ImplGlfw_InitForOpenGL(window, true);
+    ImGui_ImplGlfw_InitForOther(window, true);
     ImGui_ImplMetal_Init(device);
 
     NSWindow *nswin = glfwGetCocoaWindow(window);
@@ -157,6 +167,13 @@
             ImGui::Render();
             ImGui_ImplMetal_RenderDrawData(ImGui::GetDrawData(), commandBuffer, renderEncoder);
 
+            // Update and Render additional Platform Windows
+            if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+            {
+                ImGui::UpdatePlatformWindows();
+                ImGui::RenderPlatformWindowsDefault();
+            }
+
             [renderEncoder popDebugGroup];
             [renderEncoder endEncoding];
 
diff --git a/examples/example_glfw_opengl2/main.cpp b/examples/example_glfw_opengl2/main.cpp
index 5e47b00..1ed2083 100644
--- a/examples/example_glfw_opengl2/main.cpp
+++ b/examples/example_glfw_opengl2/main.cpp
@@ -52,11 +52,23 @@
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
+    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows
+    //io.ConfigViewportsNoAutoMerge = true;
+    //io.ConfigViewportsNoTaskBarIcon = true;
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
     //ImGui::StyleColorsLight();
 
+    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
+    ImGuiStyle& style = ImGui::GetStyle();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        style.WindowRounding = 0.0f;
+        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
+    }
+
     // Setup Platform/Renderer backends
     ImGui_ImplGlfw_InitForOpenGL(window, true);
     ImGui_ImplOpenGL2_Init();
@@ -150,6 +162,17 @@
         ImGui_ImplOpenGL2_RenderDrawData(ImGui::GetDrawData());
         //glUseProgram(last_program);
 
+        // Update and Render additional Platform Windows
+        // (Platform functions may change the current OpenGL context, so we save/restore it to make it easier to paste this code elsewhere.
+        //  For this specific demo app we could also call glfwMakeContextCurrent(window) directly)
+        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        {
+            GLFWwindow* backup_current_context = glfwGetCurrentContext();
+            ImGui::UpdatePlatformWindows();
+            ImGui::RenderPlatformWindowsDefault();
+            glfwMakeContextCurrent(backup_current_context);
+        }
+
         glfwMakeContextCurrent(window);
         glfwSwapBuffers(window);
     }
diff --git a/examples/example_glfw_opengl3/main.cpp b/examples/example_glfw_opengl3/main.cpp
index 4438fa5..4aaf406 100644
--- a/examples/example_glfw_opengl3/main.cpp
+++ b/examples/example_glfw_opengl3/main.cpp
@@ -77,11 +77,23 @@
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
+    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows
+    //io.ConfigViewportsNoAutoMerge = true;
+    //io.ConfigViewportsNoTaskBarIcon = true;
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
     //ImGui::StyleColorsLight();
 
+    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
+    ImGuiStyle& style = ImGui::GetStyle();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        style.WindowRounding = 0.0f;
+        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
+    }
+
     // Setup Platform/Renderer backends
     ImGui_ImplGlfw_InitForOpenGL(window, true);
 #ifdef __EMSCRIPTEN__
@@ -179,6 +191,17 @@
         glClear(GL_COLOR_BUFFER_BIT);
         ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
 
+        // Update and Render additional Platform Windows
+        // (Platform functions may change the current OpenGL context, so we save/restore it to make it easier to paste this code elsewhere.
+        //  For this specific demo app we could also call glfwMakeContextCurrent(window) directly)
+        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        {
+            GLFWwindow* backup_current_context = glfwGetCurrentContext();
+            ImGui::UpdatePlatformWindows();
+            ImGui::RenderPlatformWindowsDefault();
+            glfwMakeContextCurrent(backup_current_context);
+        }
+
         glfwSwapBuffers(window);
     }
 #ifdef __EMSCRIPTEN__
diff --git a/examples/example_glfw_vulkan/main.cpp b/examples/example_glfw_vulkan/main.cpp
index b6e53ed..0389003 100644
--- a/examples/example_glfw_vulkan/main.cpp
+++ b/examples/example_glfw_vulkan/main.cpp
@@ -429,11 +429,23 @@
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
+    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows
+    //io.ConfigViewportsNoAutoMerge = true;
+    //io.ConfigViewportsNoTaskBarIcon = true;
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
     //ImGui::StyleColorsLight();
 
+    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
+    ImGuiStyle& style = ImGui::GetStyle();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        style.WindowRounding = 0.0f;
+        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
+    }
+
     // Setup Platform/Renderer backends
     ImGui_ImplGlfw_InitForVulkan(window, true);
     ImGui_ImplVulkan_InitInfo init_info = {};
@@ -542,17 +554,25 @@
 
         // Rendering
         ImGui::Render();
-        ImDrawData* draw_data = ImGui::GetDrawData();
-        const bool is_minimized = (draw_data->DisplaySize.x <= 0.0f || draw_data->DisplaySize.y <= 0.0f);
-        if (!is_minimized)
+        ImDrawData* main_draw_data = ImGui::GetDrawData();
+        const bool main_is_minimized = (main_draw_data->DisplaySize.x <= 0.0f || main_draw_data->DisplaySize.y <= 0.0f);
+        wd->ClearValue.color.float32[0] = clear_color.x * clear_color.w;
+        wd->ClearValue.color.float32[1] = clear_color.y * clear_color.w;
+        wd->ClearValue.color.float32[2] = clear_color.z * clear_color.w;
+        wd->ClearValue.color.float32[3] = clear_color.w;
+        if (!main_is_minimized)
+            FrameRender(wd, main_draw_data);
+
+        // Update and Render additional Platform Windows
+        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
         {
-            wd->ClearValue.color.float32[0] = clear_color.x * clear_color.w;
-            wd->ClearValue.color.float32[1] = clear_color.y * clear_color.w;
-            wd->ClearValue.color.float32[2] = clear_color.z * clear_color.w;
-            wd->ClearValue.color.float32[3] = clear_color.w;
-            FrameRender(wd, draw_data);
-            FramePresent(wd);
+            ImGui::UpdatePlatformWindows();
+            ImGui::RenderPlatformWindowsDefault();
         }
+
+        // Present Main Platform Window
+        if (!main_is_minimized)
+            FramePresent(wd);
     }
 
     // Cleanup
diff --git a/examples/example_glfw_wgpu/main.cpp b/examples/example_glfw_wgpu/main.cpp
index 4e47b83..9a079f5 100644
--- a/examples/example_glfw_wgpu/main.cpp
+++ b/examples/example_glfw_wgpu/main.cpp
@@ -93,6 +93,7 @@
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
diff --git a/examples/example_glut_opengl2/main.cpp b/examples/example_glut_opengl2/main.cpp
index 58539ca..4edae6f 100644
--- a/examples/example_glut_opengl2/main.cpp
+++ b/examples/example_glut_opengl2/main.cpp
@@ -61,6 +61,7 @@
     ImGui::CreateContext();
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
@@ -78,7 +79,6 @@
     // Generally you may always pass all inputs to dear imgui, and hide them from your application based on those two flags.
     ImGui_ImplGLUT_InstallFuncs();
 
-
     // Load Fonts
     // - If no fonts are loaded, dear imgui will use the default font. You can also load multiple fonts and use ImGui::PushFont()/PopFont() to select them.
     // - AddFontFromFileTTF() will return the ImFont* so you can store it if you need to select the font among multiple.
diff --git a/examples/example_sdl2_directx11/main.cpp b/examples/example_sdl2_directx11/main.cpp
index 3275baf..70fc5f8 100644
--- a/examples/example_sdl2_directx11/main.cpp
+++ b/examples/example_sdl2_directx11/main.cpp
@@ -71,11 +71,23 @@
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
+    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows
+    //io.ConfigViewportsNoAutoMerge = true;
+    //io.ConfigViewportsNoTaskBarIcon = true;
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
     //ImGui::StyleColorsLight();
 
+    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
+    ImGuiStyle& style = ImGui::GetStyle();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        style.WindowRounding = 0.0f;
+        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
+    }
+
     // Setup Platform/Renderer backends
     ImGui_ImplSDL2_InitForD3D(window);
     ImGui_ImplDX11_Init(g_pd3dDevice, g_pd3dDeviceContext);
@@ -176,6 +188,13 @@
         g_pd3dDeviceContext->ClearRenderTargetView(g_mainRenderTargetView, clear_color_with_alpha);
         ImGui_ImplDX11_RenderDrawData(ImGui::GetDrawData());
 
+        // Update and Render additional Platform Windows
+        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        {
+            ImGui::UpdatePlatformWindows();
+            ImGui::RenderPlatformWindowsDefault();
+        }
+
         g_pSwapChain->Present(1, 0); // Present with vsync
         //g_pSwapChain->Present(0, 0); // Present without vsync
     }
diff --git a/examples/example_sdl2_metal/main.mm b/examples/example_sdl2_metal/main.mm
index d548127..5cd7043 100644
--- a/examples/example_sdl2_metal/main.mm
+++ b/examples/example_sdl2_metal/main.mm
@@ -24,11 +24,21 @@
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;  // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;   // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;      // Enable Docking
+    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;    // Enable Multi-Viewport / Platform Windows
 
     // Setup style
     ImGui::StyleColorsDark();
     //ImGui::StyleColorsLight();
 
+    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
+    ImGuiStyle& style = ImGui::GetStyle();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        style.WindowRounding = 0.0f;
+        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
+    }
+
     // Load Fonts
     // - If no fonts are loaded, dear imgui will use the default font. You can also load multiple fonts and use ImGui::PushFont()/PopFont() to select them.
     // - AddFontFromFileTTF() will return the ImFont* so you can store it if you need to select the font among multiple.
@@ -168,6 +178,13 @@
             ImGui::Render();
             ImGui_ImplMetal_RenderDrawData(ImGui::GetDrawData(), commandBuffer, renderEncoder);
 
+            // Update and Render additional Platform Windows
+            if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+            {
+                ImGui::UpdatePlatformWindows();
+                ImGui::RenderPlatformWindowsDefault();
+            }
+
             [renderEncoder popDebugGroup];
             [renderEncoder endEncoding];
 
diff --git a/examples/example_sdl2_opengl2/main.cpp b/examples/example_sdl2_opengl2/main.cpp
index efb28ed..f92c54e 100644
--- a/examples/example_sdl2_opengl2/main.cpp
+++ b/examples/example_sdl2_opengl2/main.cpp
@@ -57,11 +57,23 @@
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
+    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows
+    //io.ConfigViewportsNoAutoMerge = true;
+    //io.ConfigViewportsNoTaskBarIcon = true;
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
     //ImGui::StyleColorsLight();
 
+    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
+    ImGuiStyle& style = ImGui::GetStyle();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        style.WindowRounding = 0.0f;
+        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
+    }
+
     // Setup Platform/Renderer backends
     ImGui_ImplSDL2_InitForOpenGL(window, gl_context);
     ImGui_ImplOpenGL2_Init();
@@ -155,6 +167,19 @@
         glClear(GL_COLOR_BUFFER_BIT);
         //glUseProgram(0); // You may want this if using this code in an OpenGL 3+ context where shaders may be bound
         ImGui_ImplOpenGL2_RenderDrawData(ImGui::GetDrawData());
+
+        // Update and Render additional Platform Windows
+        // (Platform functions may change the current OpenGL context, so we save/restore it to make it easier to paste this code elsewhere.
+        //  For this specific demo app we could also call SDL_GL_MakeCurrent(window, gl_context) directly)
+        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        {
+            SDL_Window* backup_current_window = SDL_GL_GetCurrentWindow();
+            SDL_GLContext backup_current_context = SDL_GL_GetCurrentContext();
+            ImGui::UpdatePlatformWindows();
+            ImGui::RenderPlatformWindowsDefault();
+            SDL_GL_MakeCurrent(backup_current_window, backup_current_context);
+        }
+
         SDL_GL_SwapWindow(window);
     }
 
diff --git a/examples/example_sdl2_opengl3/main.cpp b/examples/example_sdl2_opengl3/main.cpp
index d748c13..9f983d9 100644
--- a/examples/example_sdl2_opengl3/main.cpp
+++ b/examples/example_sdl2_opengl3/main.cpp
@@ -84,11 +84,23 @@
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
+    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows
+    //io.ConfigViewportsNoAutoMerge = true;
+    //io.ConfigViewportsNoTaskBarIcon = true;
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
     //ImGui::StyleColorsLight();
 
+    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
+    ImGuiStyle& style = ImGui::GetStyle();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        style.WindowRounding = 0.0f;
+        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
+    }
+
     // Setup Platform/Renderer backends
     ImGui_ImplSDL2_InitForOpenGL(window, gl_context);
     ImGui_ImplOpenGL3_Init(glsl_version);
@@ -189,6 +201,19 @@
         glClearColor(clear_color.x * clear_color.w, clear_color.y * clear_color.w, clear_color.z * clear_color.w, clear_color.w);
         glClear(GL_COLOR_BUFFER_BIT);
         ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
+
+        // Update and Render additional Platform Windows
+        // (Platform functions may change the current OpenGL context, so we save/restore it to make it easier to paste this code elsewhere.
+        //  For this specific demo app we could also call SDL_GL_MakeCurrent(window, gl_context) directly)
+        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        {
+            SDL_Window* backup_current_window = SDL_GL_GetCurrentWindow();
+            SDL_GLContext backup_current_context = SDL_GL_GetCurrentContext();
+            ImGui::UpdatePlatformWindows();
+            ImGui::RenderPlatformWindowsDefault();
+            SDL_GL_MakeCurrent(backup_current_window, backup_current_context);
+        }
+
         SDL_GL_SwapWindow(window);
     }
 #ifdef __EMSCRIPTEN__
diff --git a/examples/example_sdl2_sdlrenderer2/main.cpp b/examples/example_sdl2_sdlrenderer2/main.cpp
index 8bb3099..4d0ebff 100644
--- a/examples/example_sdl2_sdlrenderer2/main.cpp
+++ b/examples/example_sdl2_sdlrenderer2/main.cpp
@@ -59,6 +59,7 @@
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
diff --git a/examples/example_sdl2_vulkan/main.cpp b/examples/example_sdl2_vulkan/main.cpp
index df0db4d..9ecaea2 100644
--- a/examples/example_sdl2_vulkan/main.cpp
+++ b/examples/example_sdl2_vulkan/main.cpp
@@ -429,11 +429,23 @@
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
+    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows
+    //io.ConfigFlags |= ImGuiConfigFlags_ViewportsNoTaskBarIcons;
+    //io.ConfigFlags |= ImGuiConfigFlags_ViewportsNoMerge;
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
     //ImGui::StyleColorsLight();
 
+    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
+    ImGuiStyle& style = ImGui::GetStyle();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        style.WindowRounding = 0.0f;
+        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
+    }
+
     // Setup Platform/Renderer backends
     ImGui_ImplSDL2_InitForVulkan(window);
     ImGui_ImplVulkan_InitInfo init_info = {};
@@ -551,17 +563,25 @@
 
         // Rendering
         ImGui::Render();
-        ImDrawData* draw_data = ImGui::GetDrawData();
-        const bool is_minimized = (draw_data->DisplaySize.x <= 0.0f || draw_data->DisplaySize.y <= 0.0f);
-        if (!is_minimized)
+        ImDrawData* main_draw_data = ImGui::GetDrawData();
+        const bool main_is_minimized = (main_draw_data->DisplaySize.x <= 0.0f || main_draw_data->DisplaySize.y <= 0.0f);
+        wd->ClearValue.color.float32[0] = clear_color.x * clear_color.w;
+        wd->ClearValue.color.float32[1] = clear_color.y * clear_color.w;
+        wd->ClearValue.color.float32[2] = clear_color.z * clear_color.w;
+        wd->ClearValue.color.float32[3] = clear_color.w;
+        if (!main_is_minimized)
+            FrameRender(wd, main_draw_data);
+
+        // Update and Render additional Platform Windows
+        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
         {
-            wd->ClearValue.color.float32[0] = clear_color.x * clear_color.w;
-            wd->ClearValue.color.float32[1] = clear_color.y * clear_color.w;
-            wd->ClearValue.color.float32[2] = clear_color.z * clear_color.w;
-            wd->ClearValue.color.float32[3] = clear_color.w;
-            FrameRender(wd, draw_data);
-            FramePresent(wd);
+            ImGui::UpdatePlatformWindows();
+            ImGui::RenderPlatformWindowsDefault();
         }
+
+        // Present Main Platform Window
+        if (!main_is_minimized)
+            FramePresent(wd);
     }
 
     // Cleanup
diff --git a/examples/example_sdl3_opengl3/main.cpp b/examples/example_sdl3_opengl3/main.cpp
index da12589..da88b7f 100644
--- a/examples/example_sdl3_opengl3/main.cpp
+++ b/examples/example_sdl3_opengl3/main.cpp
@@ -83,11 +83,23 @@
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
+    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows
+    //io.ConfigViewportsNoAutoMerge = true;
+    //io.ConfigViewportsNoTaskBarIcon = true;
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
     //ImGui::StyleColorsLight();
 
+    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
+    ImGuiStyle& style = ImGui::GetStyle();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        style.WindowRounding = 0.0f;
+        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
+    }
+
     // Setup Platform/Renderer backends
     ImGui_ImplSDL3_InitForOpenGL(window, gl_context);
     ImGui_ImplOpenGL3_Init(glsl_version);
@@ -188,6 +200,19 @@
         glClearColor(clear_color.x * clear_color.w, clear_color.y * clear_color.w, clear_color.z * clear_color.w, clear_color.w);
         glClear(GL_COLOR_BUFFER_BIT);
         ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
+
+        // Update and Render additional Platform Windows
+        // (Platform functions may change the current OpenGL context, so we save/restore it to make it easier to paste this code elsewhere.
+        //  For this specific demo app we could also call SDL_GL_MakeCurrent(window, gl_context) directly)
+        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        {
+            SDL_Window* backup_current_window = SDL_GL_GetCurrentWindow();
+            SDL_GLContext backup_current_context = SDL_GL_GetCurrentContext();
+            ImGui::UpdatePlatformWindows();
+            ImGui::RenderPlatformWindowsDefault();
+            SDL_GL_MakeCurrent(backup_current_window, backup_current_context);
+        }
+
         SDL_GL_SwapWindow(window);
     }
 #ifdef __EMSCRIPTEN__
diff --git a/examples/example_sdl3_sdlrenderer3/main.cpp b/examples/example_sdl3_sdlrenderer3/main.cpp
index baa7cd7..890c269 100644
--- a/examples/example_sdl3_sdlrenderer3/main.cpp
+++ b/examples/example_sdl3_sdlrenderer3/main.cpp
@@ -58,6 +58,7 @@
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
diff --git a/examples/example_win32_directx10/main.cpp b/examples/example_win32_directx10/main.cpp
index 21198da..a9e5e31 100644
--- a/examples/example_win32_directx10/main.cpp
+++ b/examples/example_win32_directx10/main.cpp
@@ -54,11 +54,23 @@
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
+    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows
+    //io.ConfigViewportsNoAutoMerge = true;
+    //io.ConfigViewportsNoTaskBarIcon = true;
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
     //ImGui::StyleColorsLight();
 
+    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
+    ImGuiStyle& style = ImGui::GetStyle();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        style.WindowRounding = 0.0f;
+        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
+    }
+
     // Setup Platform/Renderer backends
     ImGui_ImplWin32_Init(hwnd);
     ImGui_ImplDX10_Init(g_pd3dDevice);
@@ -167,6 +179,13 @@
         g_pd3dDevice->ClearRenderTargetView(g_mainRenderTargetView, clear_color_with_alpha);
         ImGui_ImplDX10_RenderDrawData(ImGui::GetDrawData());
 
+        // Update and Render additional Platform Windows
+        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        {
+            ImGui::UpdatePlatformWindows();
+            ImGui::RenderPlatformWindowsDefault();
+        }
+
         // Present
         HRESULT hr = g_pSwapChain->Present(1, 0);   // Present with vsync
         //HRESULT hr = g_pSwapChain->Present(0, 0); // Present without vsync
@@ -186,7 +205,6 @@
 }
 
 // Helper functions
-
 bool CreateDeviceD3D(HWND hWnd)
 {
     // Setup swap chain
diff --git a/examples/example_win32_directx11/main.cpp b/examples/example_win32_directx11/main.cpp
index 5285df1..d25213b 100644
--- a/examples/example_win32_directx11/main.cpp
+++ b/examples/example_win32_directx11/main.cpp
@@ -54,11 +54,28 @@
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
+    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows
+    //io.ConfigViewportsNoAutoMerge = true;
+    //io.ConfigViewportsNoTaskBarIcon = true;
+    //io.ConfigViewportsNoDefaultParent = true;
+    //io.ConfigDockingAlwaysTabBar = true;
+    //io.ConfigDockingTransparentPayload = true;
+    //io.ConfigFlags |= ImGuiConfigFlags_DpiEnableScaleFonts;     // FIXME-DPI: Experimental. THIS CURRENTLY DOESN'T WORK AS EXPECTED. DON'T USE IN USER APP!
+    //io.ConfigFlags |= ImGuiConfigFlags_DpiEnableScaleViewports; // FIXME-DPI: Experimental.
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
     //ImGui::StyleColorsLight();
 
+    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
+    ImGuiStyle& style = ImGui::GetStyle();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        style.WindowRounding = 0.0f;
+        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
+    }
+
     // Setup Platform/Renderer backends
     ImGui_ImplWin32_Init(hwnd);
     ImGui_ImplDX11_Init(g_pd3dDevice, g_pd3dDeviceContext);
@@ -167,6 +184,13 @@
         g_pd3dDeviceContext->ClearRenderTargetView(g_mainRenderTargetView, clear_color_with_alpha);
         ImGui_ImplDX11_RenderDrawData(ImGui::GetDrawData());
 
+        // Update and Render additional Platform Windows
+        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        {
+            ImGui::UpdatePlatformWindows();
+            ImGui::RenderPlatformWindowsDefault();
+        }
+
         // Present
         HRESULT hr = g_pSwapChain->Present(1, 0);   // Present with vsync
         //HRESULT hr = g_pSwapChain->Present(0, 0); // Present without vsync
@@ -186,7 +210,6 @@
 }
 
 // Helper functions
-
 bool CreateDeviceD3D(HWND hWnd)
 {
     // Setup swap chain
@@ -241,6 +264,10 @@
     if (g_mainRenderTargetView) { g_mainRenderTargetView->Release(); g_mainRenderTargetView = nullptr; }
 }
 
+#ifndef WM_DPICHANGED
+#define WM_DPICHANGED 0x02E0 // From Windows SDK 8.1+ headers
+#endif
+
 // Forward declare message handler from imgui_impl_win32.cpp
 extern IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandler(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);
 
@@ -269,6 +296,15 @@
     case WM_DESTROY:
         ::PostQuitMessage(0);
         return 0;
+    case WM_DPICHANGED:
+        if (ImGui::GetIO().ConfigFlags & ImGuiConfigFlags_DpiEnableScaleViewports)
+        {
+            //const int dpi = HIWORD(wParam);
+            //printf("WM_DPICHANGED to %d (%.0f%%)\n", dpi, (float)dpi / 96.0f * 100.0f);
+            const RECT* suggested_rect = (RECT*)lParam;
+            ::SetWindowPos(hWnd, nullptr, suggested_rect->left, suggested_rect->top, suggested_rect->right - suggested_rect->left, suggested_rect->bottom - suggested_rect->top, SWP_NOZORDER | SWP_NOACTIVATE);
+        }
+        break;
     }
     return ::DefWindowProcW(hWnd, msg, wParam, lParam);
 }
diff --git a/examples/example_win32_directx12/main.cpp b/examples/example_win32_directx12/main.cpp
index 57a481c..9479b43 100644
--- a/examples/example_win32_directx12/main.cpp
+++ b/examples/example_win32_directx12/main.cpp
@@ -90,11 +90,23 @@
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
+    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows
+    //io.ConfigViewportsNoAutoMerge = true;
+    //io.ConfigViewportsNoTaskBarIcon = true;
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
     //ImGui::StyleColorsLight();
 
+    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
+    ImGuiStyle& style = ImGui::GetStyle();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        style.WindowRounding = 0.0f;
+        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
+    }
+
     // Setup Platform/Renderer backends
     ImGui_ImplWin32_Init(hwnd);
     ImGui_ImplDX12_Init(g_pd3dDevice, NUM_FRAMES_IN_FLIGHT,
@@ -220,6 +232,13 @@
 
         g_pd3dCommandQueue->ExecuteCommandLists(1, (ID3D12CommandList* const*)&g_pd3dCommandList);
 
+        // Update and Render additional Platform Windows
+        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        {
+            ImGui::UpdatePlatformWindows();
+            ImGui::RenderPlatformWindowsDefault(nullptr, (void*)g_pd3dCommandList);
+        }
+
         // Present
         HRESULT hr = g_pSwapChain->Present(1, 0);   // Present with vsync
         //HRESULT hr = g_pSwapChain->Present(0, 0); // Present without vsync
@@ -246,7 +265,6 @@
 }
 
 // Helper functions
-
 bool CreateDeviceD3D(HWND hWnd)
 {
     // Setup swap chain
diff --git a/examples/example_win32_directx9/main.cpp b/examples/example_win32_directx9/main.cpp
index 422248b..8063636 100644
--- a/examples/example_win32_directx9/main.cpp
+++ b/examples/example_win32_directx9/main.cpp
@@ -52,11 +52,23 @@
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
+    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows
+    //io.ConfigViewportsNoAutoMerge = true;
+    //io.ConfigViewportsNoTaskBarIcon = true;
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
     //ImGui::StyleColorsLight();
 
+    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
+    ImGuiStyle& style = ImGui::GetStyle();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        style.WindowRounding = 0.0f;
+        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
+    }
+
     // Setup Platform/Renderer backends
     ImGui_ImplWin32_Init(hwnd);
     ImGui_ImplDX9_Init(g_pd3dDevice);
@@ -177,6 +189,14 @@
             ImGui_ImplDX9_RenderDrawData(ImGui::GetDrawData());
             g_pd3dDevice->EndScene();
         }
+
+        // Update and Render additional Platform Windows
+        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        {
+            ImGui::UpdatePlatformWindows();
+            ImGui::RenderPlatformWindowsDefault();
+        }
+
         HRESULT result = g_pd3dDevice->Present(nullptr, nullptr, nullptr, nullptr);
         if (result == D3DERR_DEVICELOST)
             g_DeviceLost = true;
@@ -195,7 +215,6 @@
 }
 
 // Helper functions
-
 bool CreateDeviceD3D(HWND hWnd)
 {
     if ((g_pD3D = Direct3DCreate9(D3D_SDK_VERSION)) == nullptr)
@@ -231,6 +250,10 @@
     ImGui_ImplDX9_CreateDeviceObjects();
 }
 
+#ifndef WM_DPICHANGED
+#define WM_DPICHANGED 0x02E0 // From Windows SDK 8.1+ headers
+#endif
+
 // Forward declare message handler from imgui_impl_win32.cpp
 extern IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandler(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);
 
@@ -259,6 +282,15 @@
     case WM_DESTROY:
         ::PostQuitMessage(0);
         return 0;
+    case WM_DPICHANGED:
+        if (ImGui::GetIO().ConfigFlags & ImGuiConfigFlags_DpiEnableScaleViewports)
+        {
+            //const int dpi = HIWORD(wParam);
+            //printf("WM_DPICHANGED to %d (%.0f%%)\n", dpi, (float)dpi / 96.0f * 100.0f);
+            const RECT* suggested_rect = (RECT*)lParam;
+            ::SetWindowPos(hWnd, nullptr, suggested_rect->left, suggested_rect->top, suggested_rect->right - suggested_rect->left, suggested_rect->bottom - suggested_rect->top, SWP_NOZORDER | SWP_NOACTIVATE);
+        }
+        break;
     }
     return ::DefWindowProcW(hWnd, msg, wParam, lParam);
 }
diff --git a/examples/example_win32_opengl3/main.cpp b/examples/example_win32_opengl3/main.cpp
index 594931d..a6af3fd 100644
--- a/examples/example_win32_opengl3/main.cpp
+++ b/examples/example_win32_opengl3/main.cpp
@@ -33,6 +33,42 @@
 void ResetDeviceWGL();
 LRESULT WINAPI WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);
 
+// Support function for multi-viewports
+// Unlike most other backend combination, we need specific hooks to combine Win32+OpenGL.
+// We could in theory decide to support Win32-specific code in OpenGL backend via e.g. an hypothetical ImGui_ImplOpenGL3_InitForRawWin32().
+static void Hook_Renderer_CreateWindow(ImGuiViewport* viewport)
+{
+    assert(viewport->RendererUserData == NULL);
+
+    WGL_WindowData* data = IM_NEW(WGL_WindowData);
+    CreateDeviceWGL((HWND)viewport->PlatformHandle, data);
+    viewport->RendererUserData = data;
+}
+
+static void Hook_Renderer_DestroyWindow(ImGuiViewport* viewport)
+{
+    if (viewport->RendererUserData != NULL)
+    {
+        WGL_WindowData* data = (WGL_WindowData*)viewport->RendererUserData;
+        CleanupDeviceWGL((HWND)viewport->PlatformHandle, data);
+        IM_DELETE(data);
+        viewport->RendererUserData = NULL;
+    }
+}
+
+static void Hook_Platform_RenderWindow(ImGuiViewport* viewport, void*)
+{
+    // Activate the platform window DC in the OpenGL rendering context
+    if (WGL_WindowData* data = (WGL_WindowData*)viewport->RendererUserData)
+        wglMakeCurrent(data->hDC, g_hRC);
+}
+
+static void Hook_Renderer_SwapBuffers(ImGuiViewport* viewport, void*)
+{
+    if (WGL_WindowData* data = (WGL_WindowData*)viewport->RendererUserData)
+        ::SwapBuffers(data->hDC);
+}
+
 // Main code
 int main(int, char**)
 {
@@ -62,15 +98,39 @@
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;   // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;    // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;       // Enable Docking
+    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;     // Enable Multi-Viewport / Platform Windows
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
     //ImGui::StyleColorsClassic();
 
+    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
+    ImGuiStyle& style = ImGui::GetStyle();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        style.WindowRounding = 0.0f;
+        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
+    }
+
     // Setup Platform/Renderer backends
     ImGui_ImplWin32_InitForOpenGL(hwnd);
     ImGui_ImplOpenGL3_Init();
 
+    // Win32+GL needs specific hooks for viewport, as there are specific things needed to tie Win32 and GL api.
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+        IM_ASSERT(platform_io.Renderer_CreateWindow == NULL);
+        IM_ASSERT(platform_io.Renderer_DestroyWindow == NULL);
+        IM_ASSERT(platform_io.Renderer_SwapBuffers == NULL);
+        IM_ASSERT(platform_io.Platform_RenderWindow == NULL);
+        platform_io.Renderer_CreateWindow = Hook_Renderer_CreateWindow;
+        platform_io.Renderer_DestroyWindow = Hook_Renderer_DestroyWindow;
+        platform_io.Renderer_SwapBuffers = Hook_Renderer_SwapBuffers;
+        platform_io.Platform_RenderWindow = Hook_Platform_RenderWindow;
+    }
+
     // Load Fonts
     // - If no fonts are loaded, dear imgui will use the default font. You can also load multiple fonts and use ImGui::PushFont()/PopFont() to select them.
     // - AddFontFromFileTTF() will return the ImFont* so you can store it if you need to select the font among multiple.
@@ -158,6 +218,16 @@
         glClear(GL_COLOR_BUFFER_BIT);
         ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
 
+        // Update and Render additional Platform Windows
+        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        {
+            ImGui::UpdatePlatformWindows();
+            ImGui::RenderPlatformWindowsDefault();
+
+            // Restore the OpenGL rendering context to the main window DC, since platform windows might have changed it.
+            wglMakeCurrent(g_MainWindow.hDC, g_hRC);
+        }
+
         // Present
         ::SwapBuffers(g_MainWindow.hDC);
     }
diff --git a/imgui.cpp b/imgui.cpp
index 2a719d4..683d236 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -91,6 +91,7 @@
 // [SECTION] SETTINGS
 // [SECTION] LOCALIZATION
 // [SECTION] VIEWPORTS, PLATFORM WINDOWS
+// [SECTION] DOCKING
 // [SECTION] PLATFORM DEPENDENT HELPERS
 // [SECTION] METRICS/DEBUGGER WINDOW
 // [SECTION] DEBUG LOG WINDOW
@@ -430,6 +431,13 @@
  When you are not sure about an old symbol or function name, try using the Search/Find function of your IDE to look for comments or references in all imgui files.
  You can read releases logs https://github.com/ocornut/imgui/releases for more details.
 
+(Docking/Viewport Branch)
+ - 2024/XX/XX (1.XXXX) - when multi-viewports are enabled, all positions will be in your natural OS coordinates space. It means that:
+                          - reference to hard-coded positions such as in SetNextWindowPos(ImVec2(0,0)) are probably not what you want anymore.
+                            you may use GetMainViewport()->Pos to offset hard-coded positions, e.g. SetNextWindowPos(GetMainViewport()->Pos)
+                          - likewise io.MousePos and GetMousePos() will use OS coordinates.
+                            If you query mouse positions to interact with non-imgui coordinates you will need to offset them, e.g. subtract GetWindowViewport()->Pos.
+
  - 2024/05/22 (1.90.7) - inputs (internals): renamed ImGuiKeyOwner_None to ImGuiKeyOwner_NoOwner, to make use more explicit and reduce confusion with the default it is a non-zero value and cannot be the default value (never made public, but disclosing as I expect a few users caught on owner-aware inputs).
                        - inputs (internals): Shortcut(), SetShortcutRouting(): swapped last two parameters order in function signatures:
                             - old: Shortcut(ImGuiKeyChord key_chord, ImGuiID owner_id = 0, ImGuiInputFlags flags = 0);
@@ -441,6 +449,9 @@
                             - new: IsMouseClicked(ImGuiMouseButton button, ImGuiInputFlags flags, ImGuiID owner_id = 0);
                          for various reasons those changes makes sense. They are being made because making some of those API public.
                          only past users of imgui_internal.h with the extra parameters will be affected. Added asserts for valid flags in various functions to detect _some_ misuses, BUT NOT ALL.
+ - 2024/05/21 (1.90.7) - docking: changed signature of DockSpaceOverViewport() to add explicit dockspace id if desired. pass 0 to use old behavior. (#7611)
+                           - old: DockSpaceOverViewport(const ImGuiViewport* viewport = NULL, ImGuiDockNodeFlags flags = 0, ...);
+                           - new: DockSpaceOverViewport(ImGuiID dockspace_id = 0, const ImGuiViewport* viewport = NULL, ImGuiDockNodeFlags flags = 0, ...);
  - 2024/05/16 (1.90.7) - inputs: on macOS X, Cmd and Ctrl keys are now automatically swapped by io.AddKeyEvent() as this naturally align with how macOS X uses those keys.
                            - it shouldn't really affect you unless you had custom shortcut swapping in place for macOS X apps.
                            - removed ImGuiMod_Shortcut which was previously dynamically remapping to Ctrl or Cmd/Super. It is now unnecessary to specific cross-platform idiomatic shortcuts. (#2343, #4084, #5923, #456)
@@ -1088,6 +1099,9 @@
 // Tooltip offset
 static const ImVec2 TOOLTIP_DEFAULT_OFFSET = ImVec2(16, 10);            // Multiplied by g.Style.MouseCursorScale
 
+// Docking
+static const float DOCKING_TRANSPARENT_PAYLOAD_ALPHA        = 0.50f;    // For use with io.ConfigDockingTransparentPayload. Apply to Viewport _or_ WindowBg in host viewport.
+
 //-------------------------------------------------------------------------
 // [SECTION] FORWARD DECLARATIONS
 //-------------------------------------------------------------------------
@@ -1161,7 +1175,18 @@
 
 // Viewports
 const ImGuiID           IMGUI_VIEWPORT_DEFAULT_ID = 0x11111111; // Using an arbitrary constant instead of e.g. ImHashStr("ViewportDefault", 0); so it's easier to spot in the debugger. The exact value doesn't matter.
+static ImGuiViewportP*  AddUpdateViewport(ImGuiWindow* window, ImGuiID id, const ImVec2& platform_pos, const ImVec2& size, ImGuiViewportFlags flags);
+static void             DestroyViewport(ImGuiViewportP* viewport);
 static void             UpdateViewportsNewFrame();
+static void             UpdateViewportsEndFrame();
+static void             WindowSelectViewport(ImGuiWindow* window);
+static void             WindowSyncOwnedViewport(ImGuiWindow* window, ImGuiWindow* parent_window_in_stack);
+static bool             UpdateTryMergeWindowIntoHostViewport(ImGuiWindow* window, ImGuiViewportP* host_viewport);
+static bool             UpdateTryMergeWindowIntoHostViewports(ImGuiWindow* window);
+static bool             GetWindowAlwaysWantOwnViewport(ImGuiWindow* window);
+static int              FindPlatformMonitorForPos(const ImVec2& pos);
+static int              FindPlatformMonitorForRect(const ImRect& r);
+static void             UpdateViewportPlatformMonitor(ImGuiViewportP* viewport);
 
 }
 
@@ -1253,6 +1278,7 @@
     SeparatorTextPadding        = ImVec2(20.0f,3.f);// Horizontal offset of text from each edge of the separator + spacing on other axis. Generally small values. .y is recommended to be == FramePadding.y.
     DisplayWindowPadding        = ImVec2(19,19);    // Window position are clamped to be visible within the display area or monitors by at least this amount. Only applies to regular windows.
     DisplaySafeAreaPadding      = ImVec2(3,3);      // If you cannot see the edge of your screen (e.g. on a TV) increase the safe area padding. Covers popups/tooltips as well regular windows.
+    DockingSeparatorSize        = 2.0f;             // Thickness of resizing border between docked windows
     MouseCursorScale            = 1.0f;             // Scale software rendered mouse cursor (when io.MouseDrawCursor is enabled). May be removed later.
     AntiAliasedLines            = true;             // Enable anti-aliased lines/borders. Disable if you are really tight on CPU/GPU.
     AntiAliasedLinesUseTex      = true;             // Enable anti-aliased lines/borders using textures where possible. Require backend to render with bilinear filtering (NOT point/nearest filtering).
@@ -1296,6 +1322,7 @@
     TabRounding = ImTrunc(TabRounding * scale_factor);
     TabMinWidthForCloseButton = (TabMinWidthForCloseButton != FLT_MAX) ? ImTrunc(TabMinWidthForCloseButton * scale_factor) : FLT_MAX;
     SeparatorTextPadding = ImTrunc(SeparatorTextPadding * scale_factor);
+    DockingSeparatorSize = ImTrunc(DockingSeparatorSize * scale_factor);
     DisplayWindowPadding = ImTrunc(DisplayWindowPadding * scale_factor);
     DisplaySafeAreaPadding = ImTrunc(DisplaySafeAreaPadding * scale_factor);
     MouseCursorScale = ImTrunc(MouseCursorScale * scale_factor);
@@ -1327,11 +1354,17 @@
     FontAllowUserScaling = false;
     DisplayFramebufferScale = ImVec2(1.0f, 1.0f);
 
-    MouseDoubleClickTime = 0.30f;
-    MouseDoubleClickMaxDist = 6.0f;
-    MouseDragThreshold = 6.0f;
-    KeyRepeatDelay = 0.275f;
-    KeyRepeatRate = 0.050f;
+    // Docking options (when ImGuiConfigFlags_DockingEnable is set)
+    ConfigDockingNoSplit = false;
+    ConfigDockingWithShift = false;
+    ConfigDockingAlwaysTabBar = false;
+    ConfigDockingTransparentPayload = false;
+
+    // Viewport options (when ImGuiConfigFlags_ViewportsEnable is set)
+    ConfigViewportsNoAutoMerge = false;
+    ConfigViewportsNoTaskBarIcon = false;
+    ConfigViewportsNoDecoration = true;
+    ConfigViewportsNoDefaultParent = false;
 
     // Miscellaneous options
     MouseDrawCursor = false;
@@ -1350,6 +1383,13 @@
     ConfigDebugBeginReturnValueOnce = false;
     ConfigDebugBeginReturnValueLoop = false;
 
+    // Inputs Behaviors
+    MouseDoubleClickTime = 0.30f;
+    MouseDoubleClickMaxDist = 6.0f;
+    MouseDragThreshold = 6.0f;
+    KeyRepeatDelay = 0.275f;
+    KeyRepeatRate = 0.050f;
+
     // Platform Functions
     // Note: Initialize() will setup default clipboard/ime handlers.
     BackendPlatformName = BackendRendererName = NULL;
@@ -1691,6 +1731,27 @@
     g.InputEventsNextMouseSource = source;
 }
 
+void ImGuiIO::AddMouseViewportEvent(ImGuiID viewport_id)
+{
+    IM_ASSERT(Ctx != NULL);
+    ImGuiContext& g = *Ctx;
+    //IM_ASSERT(g.IO.BackendFlags & ImGuiBackendFlags_HasMouseHoveredViewport);
+    if (!AppAcceptingEvents)
+        return;
+
+    // Filter duplicate
+    const ImGuiInputEvent* latest_event = FindLatestInputEvent(&g, ImGuiInputEventType_MouseViewport);
+    const ImGuiID latest_viewport_id = latest_event ? latest_event->MouseViewport.HoveredViewportID : g.IO.MouseHoveredViewport;
+    if (latest_viewport_id == viewport_id)
+        return;
+
+    ImGuiInputEvent e;
+    e.Type = ImGuiInputEventType_MouseViewport;
+    e.Source = ImGuiInputSource_Mouse;
+    e.MouseViewport.HoveredViewportID = viewport_id;
+    g.InputEventsQueue.push_back(e);
+}
+
 void ImGuiIO::AddFocusEvent(bool focused)
 {
     IM_ASSERT(Ctx != NULL);
@@ -3181,6 +3242,11 @@
     }
 }
 
+static const ImGuiCol GWindowDockStyleColors[ImGuiWindowDockStyleCol_COUNT] =
+{
+    ImGuiCol_Text, ImGuiCol_Tab, ImGuiCol_TabHovered, ImGuiCol_TabActive, ImGuiCol_TabUnfocused, ImGuiCol_TabUnfocusedActive
+};
+
 static const ImGuiDataVarInfo GStyleVarInfo[] =
 {
     { ImGuiDataType_Float, 1, (ImU32)offsetof(ImGuiStyle, Alpha) },                     // ImGuiStyleVar_Alpha
@@ -3215,6 +3281,7 @@
     { ImGuiDataType_Float, 1, (ImU32)offsetof(ImGuiStyle, SeparatorTextBorderSize)},    // ImGuiStyleVar_SeparatorTextBorderSize
     { ImGuiDataType_Float, 2, (ImU32)offsetof(ImGuiStyle, SeparatorTextAlign) },        // ImGuiStyleVar_SeparatorTextAlign
     { ImGuiDataType_Float, 2, (ImU32)offsetof(ImGuiStyle, SeparatorTextPadding) },      // ImGuiStyleVar_SeparatorTextPadding
+    { ImGuiDataType_Float, 1, (ImU32)offsetof(ImGuiStyle, DockingSeparatorSize) },      // ImGuiStyleVar_DockingSeparatorSize
 };
 
 const ImGuiDataVarInfo* ImGui::GetStyleVarInfo(ImGuiStyleVar idx)
@@ -3316,6 +3383,8 @@
     case ImGuiCol_TabActive: return "TabActive";
     case ImGuiCol_TabUnfocused: return "TabUnfocused";
     case ImGuiCol_TabUnfocusedActive: return "TabUnfocusedActive";
+    case ImGuiCol_DockingPreview: return "DockingPreview";
+    case ImGuiCol_DockingEmptyBg: return "DockingEmptyBg";
     case ImGuiCol_PlotLines: return "PlotLines";
     case ImGuiCol_PlotLinesHovered: return "PlotLinesHovered";
     case ImGuiCol_PlotHistogram: return "PlotHistogram";
@@ -3576,7 +3645,7 @@
         if (!font_atlas->GetMouseCursorTexData(mouse_cursor, &offset, &size, &uv[0], &uv[2]))
             continue;
         const ImVec2 pos = base_pos - offset;
-        const float scale = base_scale;
+        const float scale = base_scale * viewport->DpiScale;
         if (!viewport->GetMainRect().Overlaps(ImRect(pos, pos + ImVec2(size.x + 2, size.y + 2) * scale)))
             continue;
         ImDrawList* draw_list = GetForegroundDrawList(viewport);
@@ -3658,6 +3727,9 @@
     { ImGuiLocKey_WindowingMainMenuBar, "(Main menu bar)"                       },
     { ImGuiLocKey_WindowingPopup,       "(Popup)"                               },
     { ImGuiLocKey_WindowingUntitled,    "(Untitled)"                            },
+    { ImGuiLocKey_DockingHideTabBar,    "Hide tab bar###HideTabBar"             },
+    { ImGuiLocKey_DockingHoldShiftToDock,       "Hold SHIFT to enable Docking window."  },
+    { ImGuiLocKey_DockingDragToUndockOrMoveNode,"Click and drag to move or undock whole node."    },
 };
 
 void ImGui::Initialize()
@@ -3691,8 +3763,13 @@
     // Create default viewport
     ImGuiViewportP* viewport = IM_NEW(ImGuiViewportP)();
     viewport->ID = IMGUI_VIEWPORT_DEFAULT_ID;
+    viewport->Idx = 0;
+    viewport->PlatformWindowCreated = true;
+    viewport->Flags = ImGuiViewportFlags_OwnedByApp;
     g.Viewports.push_back(viewport);
     g.TempBuffer.resize(1024 * 3 + 1, 0);
+    g.ViewportCreatedCount++;
+    g.PlatformIO.Viewports.push_back(g.Viewports[0]);
 
     // Build KeysMayBeCharInput[] lookup table (1 bool per named key)
     for (ImGuiKey key = ImGuiKey_NamedKey_BEGIN; key < ImGuiKey_NamedKey_END; key = (ImGuiKey)(key + 1))
@@ -3703,6 +3780,8 @@
             g.KeysMayBeCharInput.SetBit(key);
 
 #ifdef IMGUI_HAS_DOCK
+    // Initialize Docking
+    DockContextInitialize(&g);
 #endif
 
     g.Initialized = true;
@@ -3732,6 +3811,12 @@
     if (g.SettingsLoaded && g.IO.IniFilename != NULL)
         SaveIniSettingsToDisk(g.IO.IniFilename);
 
+    // Destroy platform windows
+    DestroyPlatformWindows();
+
+    // Shutdown extensions
+    DockContextShutdown(&g);
+
     CallContextHooks(&g, ImGuiContextHookType_Shutdown);
 
     // Clear everything else
@@ -3755,6 +3840,7 @@
     g.BeginPopupStack.clear();
     g.NavTreeNodeStack.clear();
 
+    g.CurrentViewport = g.MouseViewport = g.MouseLastHoveredViewport = NULL;
     g.Viewports.clear_delete();
 
     g.TabBars.Clear();
@@ -3834,21 +3920,27 @@
     NameBufLen = (int)strlen(name) + 1;
     ID = ImHashStr(name);
     IDStack.push_back(ID);
+    ViewportAllowPlatformMonitorExtend = -1;
+    ViewportPos = ImVec2(FLT_MAX, FLT_MAX);
     MoveId = GetID("#MOVE");
+    TabId = GetID("#TAB");
     ScrollTarget = ImVec2(FLT_MAX, FLT_MAX);
     ScrollTargetCenterRatio = ImVec2(0.5f, 0.5f);
     AutoFitFramesX = AutoFitFramesY = -1;
     AutoPosLastDirection = ImGuiDir_None;
-    SetWindowPosAllowFlags = SetWindowSizeAllowFlags = SetWindowCollapsedAllowFlags = 0;
+    SetWindowPosAllowFlags = SetWindowSizeAllowFlags = SetWindowCollapsedAllowFlags = SetWindowDockAllowFlags = 0;
     SetWindowPosVal = SetWindowPosPivot = ImVec2(FLT_MAX, FLT_MAX);
     LastFrameActive = -1;
+    LastFrameJustFocused = -1;
     LastTimeActive = -1.0f;
-    FontWindowScale = 1.0f;
+    FontWindowScale = FontDpiScale = 1.0f;
     SettingsOffset = -1;
+    DockOrder = -1;
     DrawList = &DrawListInst;
     DrawList->_Data = &Ctx->DrawListSharedData;
     DrawList->_OwnerName = Name;
     NavPreferredScoringPosRel[0] = NavPreferredScoringPosRel[1] = ImVec2(FLT_MAX, FLT_MAX);
+    IM_PLACEMENT_NEW(&WindowClass) ImGuiWindowClass();
 }
 
 ImGuiWindow::~ImGuiWindow()
@@ -3863,7 +3955,6 @@
     ImGuiContext& g = *GImGui;
     g.CurrentWindow = window;
     g.CurrentTable = window && window->DC.CurrentTableIdx != -1 ? g.Tables.GetByIndex(window->DC.CurrentTableIdx) : NULL;
-    g.CurrentDpiScale = 1.0f; // FIXME-DPI: WIP this is modified in docking
     if (window)
     {
         g.FontSize = g.DrawListSharedData.FontSize = window->CalcFontSize();
@@ -4012,8 +4103,8 @@
     // FIXME-OPT: This could be cached/stored within the window.
     ImGuiContext& g = *GImGui;
     if (g.NavWindow)
-        if (ImGuiWindow* focused_root_window = g.NavWindow->RootWindow)
-            if (focused_root_window->WasActive && focused_root_window != window->RootWindow)
+        if (ImGuiWindow* focused_root_window = g.NavWindow->RootWindowDockTree)
+            if (focused_root_window->WasActive && focused_root_window != window->RootWindowDockTree)
             {
                 // For the purpose of those flags we differentiate "standard popup" from "modal popup"
                 // NB: The 'else' is important because Modal windows are also Popups.
@@ -4028,6 +4119,12 @@
                     if (!IsWindowWithinBeginStackOf(window->RootWindow, focused_root_window))
                         return false;
             }
+
+    // Filter by viewport
+    if (window->Viewport != g.MouseViewport)
+        if (g.MovingWindow == NULL || window->RootWindowDockTree != g.MovingWindow->RootWindowDockTree)
+            return false;
+
     return true;
 }
 
@@ -4078,7 +4175,7 @@
         if (flags & ImGuiHoveredFlags_ForTooltip)
             flags = ApplyHoverFlagsForTooltip(flags, g.Style.HoverFlagsForTooltipMouse);
 
-        IM_ASSERT((flags & (ImGuiHoveredFlags_AnyWindow | ImGuiHoveredFlags_RootWindow | ImGuiHoveredFlags_ChildWindows | ImGuiHoveredFlags_NoPopupHierarchy)) == 0);   // Flags not supported by this function
+        IM_ASSERT((flags & (ImGuiHoveredFlags_AnyWindow | ImGuiHoveredFlags_RootWindow | ImGuiHoveredFlags_ChildWindows | ImGuiHoveredFlags_NoPopupHierarchy | ImGuiHoveredFlags_DockHierarchy)) == 0);   // Flags not supported by this function
 
         // Done with rectangle culling so we can perform heavier checks now
         // Test if we are hovering the right window (our window could be behind another window)
@@ -4093,8 +4190,9 @@
         // Test if another item is active (e.g. being dragged)
         const ImGuiID id = g.LastItemData.ID;
         if ((flags & ImGuiHoveredFlags_AllowWhenBlockedByActiveItem) == 0)
-            if (g.ActiveId != 0 && g.ActiveId != id && !g.ActiveIdAllowOverlap && g.ActiveId != window->MoveId)
-                return false;
+            if (g.ActiveId != 0 && g.ActiveId != id && !g.ActiveIdAllowOverlap)
+                if (g.ActiveId != window->MoveId && g.ActiveId != window->TabId)
+                    return false;
 
         // Test if interactions on this window are blocked by an active popup or modal.
         // The ImGuiHoveredFlags_AllowWhenBlockedByPopup flag will be tested here.
@@ -4106,7 +4204,8 @@
             return false;
 
         // Special handling for calling after Begin() which represent the title bar or tab.
-        // When the window is skipped/collapsed (SkipItems==true) that last item will never be overwritten so we need to detect the case.
+        // When the window is skipped/collapsed (SkipItems==true) that last item (always ->MoveId submitted by Begin)
+        // will never be overwritten so we need to detect the case.
         if (id == window->MoveId && window->WriteAccessed)
             return false;
 
@@ -4343,6 +4442,12 @@
     return GImGui->IO;
 }
 
+ImGuiPlatformIO& ImGui::GetPlatformIO()
+{
+    IM_ASSERT(GImGui != NULL && "No current context. Did you call ImGui::CreateContext() or ImGui::SetCurrentContext()?");
+    return GImGui->PlatformIO;
+}
+
 // Pass this to your backend rendering function! Valid after Render() and until the next call to NewFrame()
 ImDrawData* ImGui::GetDrawData()
 {
@@ -4393,7 +4498,7 @@
 ImDrawList* ImGui::GetBackgroundDrawList()
 {
     ImGuiContext& g = *GImGui;
-    return GetBackgroundDrawList(g.Viewports[0]);
+    return GetBackgroundDrawList(g.CurrentWindow->Viewport);
 }
 
 ImDrawList* ImGui::GetForegroundDrawList(ImGuiViewport* viewport)
@@ -4404,7 +4509,7 @@
 ImDrawList* ImGui::GetForegroundDrawList()
 {
     ImGuiContext& g = *GImGui;
-    return GetForegroundDrawList(g.Viewports[0]);
+    return GetForegroundDrawList(g.CurrentWindow->Viewport);
 }
 
 ImDrawListSharedData* ImGui::GetDrawListSharedData()
@@ -4421,17 +4526,43 @@
     FocusWindow(window);
     SetActiveID(window->MoveId, window);
     g.NavDisableHighlight = true;
-    g.ActiveIdClickOffset = g.IO.MouseClickedPos[0] - window->RootWindow->Pos;
+    g.ActiveIdClickOffset = g.IO.MouseClickedPos[0] - window->RootWindowDockTree->Pos;
     g.ActiveIdNoClearOnFocusLoss = true;
     SetActiveIdUsingAllKeyboardKeys();
 
     bool can_move_window = true;
-    if ((window->Flags & ImGuiWindowFlags_NoMove) || (window->RootWindow->Flags & ImGuiWindowFlags_NoMove))
+    if ((window->Flags & ImGuiWindowFlags_NoMove) || (window->RootWindowDockTree->Flags & ImGuiWindowFlags_NoMove))
         can_move_window = false;
+    if (ImGuiDockNode* node = window->DockNodeAsHost)
+        if (node->VisibleWindow && (node->VisibleWindow->Flags & ImGuiWindowFlags_NoMove))
+            can_move_window = false;
     if (can_move_window)
         g.MovingWindow = window;
 }
 
+// We use 'undock == false' when dragging from title bar to allow moving groups of floating nodes without undocking them.
+void ImGui::StartMouseMovingWindowOrNode(ImGuiWindow* window, ImGuiDockNode* node, bool undock)
+{
+    ImGuiContext& g = *GImGui;
+    bool can_undock_node = false;
+    if (undock && node != NULL && node->VisibleWindow && (node->VisibleWindow->Flags & ImGuiWindowFlags_NoMove) == 0 && (node->MergedFlags & ImGuiDockNodeFlags_NoUndocking) == 0)
+    {
+        // Can undock if:
+        // - part of a hierarchy with more than one visible node (if only one is visible, we'll just move the root window)
+        // - part of a dockspace node hierarchy: so we can undock the last single visible node too (trivia: undocking from a fixed/central node will create a new node and copy windows)
+        ImGuiDockNode* root_node = DockNodeGetRootNode(node);
+        if (root_node->OnlyNodeWithWindows != node || root_node->CentralNode != NULL)   // -V1051 PVS-Studio thinks node should be root_node and is wrong about that.
+            can_undock_node = true;
+    }
+
+    const bool clicked = IsMouseClicked(0);
+    const bool dragging = IsMouseDragging(0);
+    if (can_undock_node && dragging)
+        DockContextQueueUndockNode(&g, node); // Will lead to DockNodeStartMouseMovingWindow() -> StartMouseMovingWindow() being called next frame
+    else if (!can_undock_node && (clicked || dragging) && g.MovingWindow != window)
+        StartMouseMovingWindow(window);
+}
+
 // Handle mouse moving window
 // Note: moving window with the navigation keys (Square + d-pad / CTRL+TAB + Arrows) are processed in NavUpdateWindowing()
 // FIXME: We don't have strong guarantee that g.MovingWindow stay synched with g.ActiveId == g.MovingWindow->MoveId.
@@ -4445,16 +4576,43 @@
         // We actually want to move the root window. g.MovingWindow == window we clicked on (could be a child window).
         // We track it to preserve Focus and so that generally ActiveIdWindow == MovingWindow and ActiveId == MovingWindow->MoveId for consistency.
         KeepAliveID(g.ActiveId);
-        IM_ASSERT(g.MovingWindow && g.MovingWindow->RootWindow);
-        ImGuiWindow* moving_window = g.MovingWindow->RootWindow;
-        if (g.IO.MouseDown[0] && IsMousePosValid(&g.IO.MousePos))
+        IM_ASSERT(g.MovingWindow && g.MovingWindow->RootWindowDockTree);
+        ImGuiWindow* moving_window = g.MovingWindow->RootWindowDockTree;
+
+        // When a window stop being submitted while being dragged, it may will its viewport until next Begin()
+        const bool window_disappared = (!moving_window->WasActive && !moving_window->Active);
+        if (g.IO.MouseDown[0] && IsMousePosValid(&g.IO.MousePos) && !window_disappared)
         {
             ImVec2 pos = g.IO.MousePos - g.ActiveIdClickOffset;
-            SetWindowPos(moving_window, pos, ImGuiCond_Always);
+            if (moving_window->Pos.x != pos.x || moving_window->Pos.y != pos.y)
+            {
+                SetWindowPos(moving_window, pos, ImGuiCond_Always);
+                if (moving_window->Viewport && moving_window->ViewportOwned) // Synchronize viewport immediately because some overlays may relies on clipping rectangle before we Begin() into the window.
+                {
+                    moving_window->Viewport->Pos = pos;
+                    moving_window->Viewport->UpdateWorkRect();
+                }
+            }
             FocusWindow(g.MovingWindow);
         }
         else
         {
+            if (!window_disappared)
+            {
+                // Try to merge the window back into the main viewport.
+                // This works because MouseViewport should be != MovingWindow->Viewport on release (as per code in UpdateViewports)
+                if (g.ConfigFlagsCurrFrame & ImGuiConfigFlags_ViewportsEnable)
+                    UpdateTryMergeWindowIntoHostViewport(moving_window, g.MouseViewport);
+
+                // Restore the mouse viewport so that we don't hover the viewport _under_ the moved window during the frame we released the mouse button.
+                if (moving_window->Viewport && !IsDragDropPayloadBeingAccepted())
+                    g.MouseViewport = moving_window->Viewport;
+
+                // Clear the NoInput window flag set by the Viewport system
+                if (moving_window->Viewport)
+                    moving_window->Viewport->Flags &= ~ImGuiViewportFlags_NoInputs;
+            }
+
             g.MovingWindow = NULL;
             ClearActiveID();
         }
@@ -4484,7 +4642,7 @@
         return;
 
     // Click on empty space to focus window and start moving
-    // (after we're done with all our widgets)
+    // (after we're done with all our widgets, so e.g. clicking on docking tab-bar which have set HoveredId already and not get us here!)
     if (g.IO.MouseClicked[0])
     {
         // Handle the edge case of a popup being closed while clicking in its empty space.
@@ -4497,9 +4655,10 @@
             StartMouseMovingWindow(g.HoveredWindow); //-V595
 
             // Cancel moving if clicked outside of title bar
-            if (g.IO.ConfigWindowsMoveFromTitleBarOnly && !(root_window->Flags & ImGuiWindowFlags_NoTitleBar))
-                if (!root_window->TitleBarRect().Contains(g.IO.MouseClickedPos[0]))
-                    g.MovingWindow = NULL;
+            if (g.IO.ConfigWindowsMoveFromTitleBarOnly)
+                if (!(root_window->Flags & ImGuiWindowFlags_NoTitleBar) || root_window->DockIsActive)
+                    if (!root_window->TitleBarRect().Contains(g.IO.MouseClickedPos[0]))
+                        g.MovingWindow = NULL;
 
             // Cancel moving if clicked over an item which was disabled or inhibited by popups (note that we know HoveredId == 0 already)
             if (g.HoveredIdDisabled)
@@ -4525,6 +4684,29 @@
     }
 }
 
+// This is called during NewFrame()->UpdateViewportsNewFrame() only.
+// Need to keep in sync with SetWindowPos()
+static void TranslateWindow(ImGuiWindow* window, const ImVec2& delta)
+{
+    window->Pos += delta;
+    window->ClipRect.Translate(delta);
+    window->OuterRectClipped.Translate(delta);
+    window->InnerRect.Translate(delta);
+    window->DC.CursorPos += delta;
+    window->DC.CursorStartPos += delta;
+    window->DC.CursorMaxPos += delta;
+    window->DC.IdealMaxPos += delta;
+}
+
+static void ScaleWindow(ImGuiWindow* window, float scale)
+{
+    ImVec2 origin = window->Viewport->Pos;
+    window->Pos = ImFloor((window->Pos - origin) * scale + origin);
+    window->Size = ImTrunc(window->Size * scale);
+    window->SizeFull = ImTrunc(window->SizeFull * scale);
+    window->ContentSize = ImTrunc(window->ContentSize * scale);
+}
+
 static bool IsWindowActiveAndVisible(ImGuiWindow* window)
 {
     return (window->Active) && (!window->Hidden);
@@ -4546,10 +4728,11 @@
     // - We also support the moved window toggling the NoInputs flag after moving has started in order to be able to detect windows below it, which is useful for e.g. docking mechanisms.
     bool clear_hovered_windows = false;
     FindHoveredWindowEx(g.IO.MousePos, false, &g.HoveredWindow, &g.HoveredWindowUnderMovingWindow);
+    IM_ASSERT(g.HoveredWindow == NULL || g.HoveredWindow == g.MovingWindow || g.HoveredWindow->Viewport == g.MouseViewport);
 
     // Modal windows prevents mouse from hovering behind them.
     ImGuiWindow* modal_window = GetTopMostPopupModal();
-    if (modal_window && g.HoveredWindow && !IsWindowWithinBeginStackOf(g.HoveredWindow->RootWindow, modal_window))
+    if (modal_window && g.HoveredWindow && !IsWindowWithinBeginStackOf(g.HoveredWindow->RootWindow, modal_window)) // FIXME-MERGE: RootWindowDockTree ?
         clear_hovered_windows = true;
 
     // Disabled mouse?
@@ -4644,7 +4827,9 @@
     CallContextHooks(&g, ImGuiContextHookType_NewFramePre);
 
     // Check and assert for various common IO and Configuration mistakes
+    g.ConfigFlagsLastFrame = g.ConfigFlagsCurrFrame;
     ErrorCheckNewFrameSanityChecks();
+    g.ConfigFlagsCurrFrame = g.IO.ConfigFlags;
 
     // Load settings on first frame, save settings when modified (after a delay)
     UpdateSettings();
@@ -4671,6 +4856,7 @@
     UpdateViewportsNewFrame();
 
     // Setup current font and draw list shared data
+    // FIXME-VIEWPORT: the concept of a single ClipRectFullscreen is not ideal!
     g.IO.Fonts->Locked = true;
     SetupDrawListSharedData();
     SetCurrentFont(GetDefaultFont());
@@ -4678,7 +4864,10 @@
 
     // Mark rendering data as invalid to prevent user who may have a handle on it to use it.
     for (ImGuiViewportP* viewport : g.Viewports)
+    {
+        viewport->DrawData = NULL;
         viewport->DrawDataP.Valid = false;
+    }
 
     // Drag and drop keep the source ID alive so even if the source disappear our state is consistent
     if (g.DragDropActive && g.DragDropPayload.SourceId == g.ActiveId)
@@ -4798,6 +4987,10 @@
     // Update mouse input state
     UpdateMouseInputs();
 
+    // Undocking
+    // (needs to be before UpdateMouseMovingWindowNewFrame so the window is already offset and following the mouse on the detaching frame)
+    DockContextNewFrameUpdateUndocking(&g);
+
     // Find hovered window
     // (needs to be before UpdateMouseMovingWindowNewFrame so we fill g.HoveredWindowUnderMovingWindow on the mouse release frame)
     UpdateHoveredWindowAndCaptureFlags();
@@ -4860,6 +5053,9 @@
     g.ItemFlagsStack.push_back(ImGuiItemFlags_None);
     g.GroupStack.resize(0);
 
+    // Docking
+    DockContextNewFrameUpdateDocking(&g);
+
     // [DEBUG] Update debug features
 #ifndef IMGUI_DISABLE_DEBUG_TOOLS
     UpdateDebugToolItemPicker();
@@ -4929,7 +5125,8 @@
 static void AddWindowToDrawData(ImGuiWindow* window, int layer)
 {
     ImGuiContext& g = *GImGui;
-    ImGuiViewportP* viewport = g.Viewports[0];
+    ImGuiViewportP* viewport = window->Viewport;
+    IM_ASSERT(viewport != NULL);
     g.IO.MetricsRenderWindows++;
     if (window->DrawList->_Splitter._Count > 1)
         window->DrawList->ChannelsMerge(); // Merge if user forgot to merge back. Also required in Docking branch for ImGuiWindowFlags_DockNodeHost windows.
@@ -4973,17 +5170,25 @@
     ImGuiIO& io = ImGui::GetIO();
     ImDrawData* draw_data = &viewport->DrawDataP;
 
+    viewport->DrawData = draw_data; // Make publicly accessible
     viewport->DrawDataBuilder.Layers[0] = &draw_data->CmdLists;
     viewport->DrawDataBuilder.Layers[1] = &viewport->DrawDataBuilder.LayerData1;
     viewport->DrawDataBuilder.Layers[0]->resize(0);
     viewport->DrawDataBuilder.Layers[1]->resize(0);
 
+    // When minimized, we report draw_data->DisplaySize as zero to be consistent with non-viewport mode,
+    // and to allow applications/backends to easily skip rendering.
+    // FIXME: Note that we however do NOT attempt to report "zero drawlist / vertices" into the ImDrawData structure.
+    // This is because the work has been done already, and its wasted! We should fix that and add optimizations for
+    // it earlier in the pipeline, rather than pretend to hide the data at the end of the pipeline.
+    const bool is_minimized = (viewport->Flags & ImGuiViewportFlags_IsMinimized) != 0;
+
     draw_data->Valid = true;
     draw_data->CmdListsCount = 0;
     draw_data->TotalVtxCount = draw_data->TotalIdxCount = 0;
     draw_data->DisplayPos = viewport->Pos;
-    draw_data->DisplaySize = viewport->Size;
-    draw_data->FramebufferScale = io.DisplayFramebufferScale;
+    draw_data->DisplaySize = is_minimized ? ImVec2(0.0f, 0.0f) : viewport->Size;
+    draw_data->FramebufferScale = io.DisplayFramebufferScale; // FIXME-VIEWPORT: This may vary on a per-monitor/viewport basis?
     draw_data->OwnerViewport = viewport;
 }
 
@@ -5007,20 +5212,28 @@
     window->ClipRect = window->DrawList->_ClipRectStack.back();
 }
 
+static ImGuiWindow* FindFrontMostVisibleChildWindow(ImGuiWindow* window)
+{
+    for (int n = window->DC.ChildWindows.Size - 1; n >= 0; n--)
+        if (IsWindowActiveAndVisible(window->DC.ChildWindows[n]))
+            return FindFrontMostVisibleChildWindow(window->DC.ChildWindows[n]);
+    return window;
+}
+
 static void ImGui::RenderDimmedBackgroundBehindWindow(ImGuiWindow* window, ImU32 col)
 {
     if ((col & IM_COL32_A_MASK) == 0)
         return;
 
-    ImGuiViewportP* viewport = (ImGuiViewportP*)GetMainViewport();
+    ImGuiViewportP* viewport = window->Viewport;
     ImRect viewport_rect = viewport->GetMainRect();
 
     // Draw behind window by moving the draw command at the FRONT of the draw list
     {
-        // We've already called AddWindowToDrawData() which called DrawList->ChannelsMerge() on DockNodeHost windows,
-        // and draw list have been trimmed already, hence the explicit recreation of a draw command if missing.
+        // Draw list have been trimmed already, hence the explicit recreation of a draw command if missing.
         // FIXME: This is creating complication, might be simpler if we could inject a drawlist in drawdata at a given position and not attempt to manipulate ImDrawCmd order.
-        ImDrawList* draw_list = window->RootWindow->DrawList;
+        ImDrawList* draw_list = window->RootWindowDockTree->DrawList;
+        draw_list->ChannelsMerge();
         if (draw_list->CmdBuffer.Size == 0)
             draw_list->AddDrawCmd();
         draw_list->PushClipRect(viewport_rect.Min - ImVec2(1, 1), viewport_rect.Max + ImVec2(1, 1), false); // FIXME: Need to stricty ensure ImDrawCmd are not merged (ElemCount==6 checks below will verify that)
@@ -5032,6 +5245,18 @@
         draw_list->AddDrawCmd(); // We need to create a command as CmdBuffer.back().IdxOffset won't be correct if we append to same command.
         draw_list->PopClipRect();
     }
+
+    // Draw over sibling docking nodes in a same docking tree
+    if (window->RootWindow->DockIsActive)
+    {
+        ImDrawList* draw_list = FindFrontMostVisibleChildWindow(window->RootWindowDockTree)->DrawList;
+        draw_list->ChannelsMerge();
+        if (draw_list->CmdBuffer.Size == 0)
+            draw_list->AddDrawCmd();
+        draw_list->PushClipRect(viewport_rect.Min, viewport_rect.Max, false);
+        RenderRectFilledWithHole(draw_list, window->RootWindowDockTree->Rect(), window->RootWindow->Rect(), col, 0.0f);// window->RootWindowDockTree->WindowRounding);
+        draw_list->PopClipRect();
+    }
 }
 
 ImGuiWindow* ImGui::FindBottomMostVisibleWindowWithinBeginStack(ImGuiWindow* parent_window)
@@ -5051,6 +5276,8 @@
     return bottom_most_visible_window;
 }
 
+// Important: AddWindowToDrawData() has not been called yet, meaning DockNodeHost windows needs a DrawList->ChannelsMerge() before usage.
+// We call ChannelsMerge() lazily here at it is faster that doing a full iteration of g.Windows[] prior to calling RenderDimmedBackgrounds().
 static void ImGui::RenderDimmedBackgrounds()
 {
     ImGuiContext& g = *GImGui;
@@ -5062,31 +5289,50 @@
     if (!dim_bg_for_modal && !dim_bg_for_window_list)
         return;
 
+    ImGuiViewport* viewports_already_dimmed[2] = { NULL, NULL };
     if (dim_bg_for_modal)
     {
         // Draw dimming behind modal or a begin stack child, whichever comes first in draw order.
         ImGuiWindow* dim_behind_window = FindBottomMostVisibleWindowWithinBeginStack(modal_window);
         RenderDimmedBackgroundBehindWindow(dim_behind_window, GetColorU32(modal_window->DC.ModalDimBgColor, g.DimBgRatio));
+        viewports_already_dimmed[0] = modal_window->Viewport;
     }
     else if (dim_bg_for_window_list)
     {
-        // Draw dimming behind CTRL+Tab target window
+        // Draw dimming behind CTRL+Tab target window and behind CTRL+Tab UI window
         RenderDimmedBackgroundBehindWindow(g.NavWindowingTargetAnim, GetColorU32(ImGuiCol_NavWindowingDimBg, g.DimBgRatio));
+        if (g.NavWindowingListWindow != NULL && g.NavWindowingListWindow->Viewport && g.NavWindowingListWindow->Viewport != g.NavWindowingTargetAnim->Viewport)
+            RenderDimmedBackgroundBehindWindow(g.NavWindowingListWindow, GetColorU32(ImGuiCol_NavWindowingDimBg, g.DimBgRatio));
+        viewports_already_dimmed[0] = g.NavWindowingTargetAnim->Viewport;
+        viewports_already_dimmed[1] = g.NavWindowingListWindow ? g.NavWindowingListWindow->Viewport : NULL;
 
         // Draw border around CTRL+Tab target window
         ImGuiWindow* window = g.NavWindowingTargetAnim;
-        ImGuiViewport* viewport = GetMainViewport();
+        ImGuiViewport* viewport = window->Viewport;
         float distance = g.FontSize;
         ImRect bb = window->Rect();
         bb.Expand(distance);
         if (bb.GetWidth() >= viewport->Size.x && bb.GetHeight() >= viewport->Size.y)
             bb.Expand(-distance - 1.0f); // If a window fits the entire viewport, adjust its highlight inward
+        window->DrawList->ChannelsMerge();
         if (window->DrawList->CmdBuffer.Size == 0)
             window->DrawList->AddDrawCmd();
         window->DrawList->PushClipRect(viewport->Pos, viewport->Pos + viewport->Size);
         window->DrawList->AddRect(bb.Min, bb.Max, GetColorU32(ImGuiCol_NavWindowingHighlight, g.NavWindowingHighlightAlpha), window->WindowRounding, 0, 3.0f);
         window->DrawList->PopClipRect();
     }
+
+    // Draw dimming background on _other_ viewports than the ones our windows are in
+    for (ImGuiViewportP* viewport : g.Viewports)
+    {
+        if (viewport == viewports_already_dimmed[0] || viewport == viewports_already_dimmed[1])
+            continue;
+        if (modal_window && viewport->Window && IsWindowAbove(viewport->Window, modal_window))
+            continue;
+        ImDrawList* draw_list = GetForegroundDrawList(viewport);
+        const ImU32 dim_bg_col = GetColorU32(dim_bg_for_modal ? ImGuiCol_ModalWindowDimBg : ImGuiCol_NavWindowingDimBg, g.DimBgRatio);
+        draw_list->AddRectFilled(viewport->Pos, viewport->Pos + viewport->Size, dim_bg_col);
+    }
 }
 
 // This is normally called by Render(). You may want to call it directly if you want to avoid calling Render() but the gain will be very minimal.
@@ -5108,8 +5354,10 @@
     ImGuiPlatformImeData* ime_data = &g.PlatformImeData;
     if (g.IO.SetPlatformImeDataFn && memcmp(ime_data, &g.PlatformImeDataPrev, sizeof(ImGuiPlatformImeData)) != 0)
     {
+        ImGuiViewport* viewport = FindViewportByID(g.PlatformImeViewport);
         IMGUI_DEBUG_LOG_IO("[io] Calling io.SetPlatformImeDataFn(): WantVisible: %d, InputPos (%.2f,%.2f)\n", ime_data->WantVisible, ime_data->InputPos.x, ime_data->InputPos.y);
-        ImGuiViewport* viewport = GetMainViewport();
+        if (viewport == NULL)
+            viewport = GetMainViewport();
         g.IO.SetPlatformImeDataFn(viewport, ime_data);
     }
 
@@ -5122,6 +5370,11 @@
     // Update navigation: CTRL+Tab, wrap-around requests
     NavEndFrame();
 
+    // Update docking
+    DockContextEndFrame(&g);
+
+    SetCurrentViewport(NULL, NULL);
+
     // Drag and Drop: Elapse payload (if delivered, or if source stops being submitted)
     if (g.DragDropActive)
     {
@@ -5146,6 +5399,9 @@
     // Initiate moving window + handle left-click and right-click focus
     UpdateMouseMovingWindowEndFrame();
 
+    // Update user-facing viewport list (g.Viewports -> g.PlatformIO.Viewports after filtering out some)
+    UpdateViewportsEndFrame();
+
     // Sort the window list so that all child windows are after their parent
     // We cannot do that on FocusWindow() because children may not exist yet
     g.WindowsTempSortBuffer.resize(0);
@@ -5191,9 +5447,6 @@
     g.IO.MetricsRenderWindows = 0;
     CallContextHooks(&g, ImGuiContextHookType_RenderPre);
 
-    // Draw modal/window whitening backgrounds
-    RenderDimmedBackgrounds();
-
     // Add background ImDrawList (for each active viewport)
     for (ImGuiViewportP* viewport : g.Viewports)
     {
@@ -5202,9 +5455,12 @@
             AddDrawListToDrawDataEx(&viewport->DrawDataP, viewport->DrawDataBuilder.Layers[0], GetBackgroundDrawList(viewport));
     }
 
+    // Draw modal/window whitening backgrounds
+    RenderDimmedBackgrounds();
+
     // Add ImDrawList to render
     ImGuiWindow* windows_to_render_top_most[2];
-    windows_to_render_top_most[0] = (g.NavWindowingTarget && !(g.NavWindowingTarget->Flags & ImGuiWindowFlags_NoBringToFrontOnFocus)) ? g.NavWindowingTarget->RootWindow : NULL;
+    windows_to_render_top_most[0] = (g.NavWindowingTarget && !(g.NavWindowingTarget->Flags & ImGuiWindowFlags_NoBringToFrontOnFocus)) ? g.NavWindowingTarget->RootWindowDockTree : NULL;
     windows_to_render_top_most[1] = (g.NavWindowingTarget ? g.NavWindowingListWindow : NULL);
     for (ImGuiWindow* window : g.Windows)
     {
@@ -5283,8 +5539,15 @@
     ImGuiWindow* hovered_window = NULL;
     ImGuiWindow* hovered_window_under_moving_window = NULL;
 
-    if (find_first_and_in_any_viewport == false && g.MovingWindow && !(g.MovingWindow->Flags & ImGuiWindowFlags_NoMouseInputs))
-        hovered_window = g.MovingWindow;
+    // Special handling for the window being moved: Ignore the mouse viewport check (because it may reset/lose its viewport during the undocking frame)
+    ImGuiViewportP* backup_moving_window_viewport = NULL;
+    if (find_first_and_in_any_viewport == false && g.MovingWindow)
+    {
+        backup_moving_window_viewport = g.MovingWindow->Viewport;
+        g.MovingWindow->Viewport = g.MouseViewport;
+        if (!(g.MovingWindow->Flags & ImGuiWindowFlags_NoMouseInputs))
+            hovered_window = g.MovingWindow;
+    }
 
     ImVec2 padding_regular = g.Style.TouchExtraPadding;
     ImVec2 padding_for_resize = g.IO.ConfigWindowsResizeFromEdges ? g.WindowsHoverPadding : padding_regular;
@@ -5296,6 +5559,9 @@
             continue;
         if (window->Flags & ImGuiWindowFlags_NoMouseInputs)
             continue;
+        IM_ASSERT(window->Viewport);
+        if (window->Viewport != g.MouseViewport)
+            continue;
 
         // Using the clipped AABB, a child window will typically be clipped by its parent (not always)
         ImVec2 hit_padding = (window->Flags & (ImGuiWindowFlags_NoResize | ImGuiWindowFlags_AlwaysAutoResize)) ? padding_regular : padding_for_resize;
@@ -5322,7 +5588,7 @@
             if (hovered_window == NULL)
                 hovered_window = window;
             IM_MSVC_WARNING_SUPPRESS(28182); // [Static Analyzer] Dereferencing NULL pointer.
-            if (hovered_window_under_moving_window == NULL && (!g.MovingWindow || window->RootWindow != g.MovingWindow->RootWindow))
+            if (hovered_window_under_moving_window == NULL && (!g.MovingWindow || window->RootWindowDockTree != g.MovingWindow->RootWindowDockTree))
                 hovered_window_under_moving_window = window;
             if (hovered_window && hovered_window_under_moving_window)
                 break;
@@ -5332,6 +5598,8 @@
     *out_hovered_window = hovered_window;
     if (out_hovered_window_under_moving_window != NULL)
         *out_hovered_window_under_moving_window = hovered_window_under_moving_window;
+    if (find_first_and_in_any_viewport == false && g.MovingWindow)
+        g.MovingWindow->Viewport = backup_moving_window_viewport;
 }
 
 bool ImGui::IsItemActive()
@@ -5371,6 +5639,13 @@
     ImGuiContext& g = *GImGui;
     if (g.NavId != g.LastItemData.ID || g.NavId == 0)
         return false;
+
+    // Special handling for the dummy item after Begin() which represent the title bar or tab.
+    // When the window is collapsed (SkipItems==true) that last item will never be overwritten so we need to detect the case.
+    ImGuiWindow* window = g.CurrentWindow;
+    if (g.LastItemData.ID == window->ID && window->WriteAccessed)
+        return false;
+
     return true;
 }
 
@@ -5522,7 +5797,7 @@
         child_flags &= ~ImGuiChildFlags_ResizeY;
 
     // Set window flags
-    window_flags |= ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_NoTitleBar;
+    window_flags |= ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoDocking;
     window_flags |= (parent_window->Flags & ImGuiWindowFlags_NoMove); // Inherit the NoMove flag
     if (child_flags & (ImGuiChildFlags_AutoResizeX | ImGuiChildFlags_AutoResizeY | ImGuiChildFlags_AlwaysAutoResize))
         window_flags |= ImGuiWindowFlags_AlwaysAutoResize;
@@ -5651,6 +5926,7 @@
     window->SetWindowPosAllowFlags       = enabled ? (window->SetWindowPosAllowFlags       | flags) : (window->SetWindowPosAllowFlags       & ~flags);
     window->SetWindowSizeAllowFlags      = enabled ? (window->SetWindowSizeAllowFlags      | flags) : (window->SetWindowSizeAllowFlags      & ~flags);
     window->SetWindowCollapsedAllowFlags = enabled ? (window->SetWindowCollapsedAllowFlags | flags) : (window->SetWindowCollapsedAllowFlags & ~flags);
+    window->SetWindowDockAllowFlags      = enabled ? (window->SetWindowDockAllowFlags      | flags) : (window->SetWindowDockAllowFlags      & ~flags);
 }
 
 ImGuiWindow* ImGui::FindWindowByID(ImGuiID id)
@@ -5667,10 +5943,19 @@
 
 static void ApplyWindowSettings(ImGuiWindow* window, ImGuiWindowSettings* settings)
 {
-    window->Pos = ImTrunc(ImVec2(settings->Pos.x, settings->Pos.y));
+    const ImGuiViewport* main_viewport = ImGui::GetMainViewport();
+    window->ViewportPos = main_viewport->Pos;
+    if (settings->ViewportId)
+    {
+        window->ViewportId = settings->ViewportId;
+        window->ViewportPos = ImVec2(settings->ViewportPos.x, settings->ViewportPos.y);
+    }
+    window->Pos = ImTrunc(ImVec2(settings->Pos.x + window->ViewportPos.x, settings->Pos.y + window->ViewportPos.y));
     if (settings->Size.x > 0 && settings->Size.y > 0)
         window->Size = window->SizeFull = ImTrunc(ImVec2(settings->Size.x, settings->Size.y));
     window->Collapsed = settings->Collapsed;
+    window->DockId = settings->DockId;
+    window->DockOrder = settings->DockOrder;
 }
 
 static void UpdateWindowInFocusOrderList(ImGuiWindow* window, bool just_created, ImGuiWindowFlags new_flags)
@@ -5703,7 +5988,8 @@
     const ImGuiViewport* main_viewport = ImGui::GetMainViewport();
     window->Pos = main_viewport->Pos + ImVec2(60, 60);
     window->Size = window->SizeFull = ImVec2(0, 0);
-    window->SetWindowPosAllowFlags = window->SetWindowSizeAllowFlags = window->SetWindowCollapsedAllowFlags = ImGuiCond_Always | ImGuiCond_Once | ImGuiCond_FirstUseEver | ImGuiCond_Appearing;
+    window->ViewportPos = main_viewport->Pos;
+    window->SetWindowPosAllowFlags = window->SetWindowSizeAllowFlags = window->SetWindowCollapsedAllowFlags = window->SetWindowDockAllowFlags = ImGuiCond_Always | ImGuiCond_Once | ImGuiCond_FirstUseEver | ImGuiCond_Appearing;
 
     if (settings != NULL)
     {
@@ -5751,6 +6037,16 @@
     return window;
 }
 
+static ImGuiWindow* GetWindowForTitleDisplay(ImGuiWindow* window)
+{
+    return window->DockNodeAsHost ? window->DockNodeAsHost->VisibleWindow : window;
+}
+
+static ImGuiWindow* GetWindowForTitleAndMenuHeight(ImGuiWindow* window)
+{
+    return (window->DockNodeAsHost && window->DockNodeAsHost->VisibleWindow) ? window->DockNodeAsHost->VisibleWindow : window;
+}
+
 static inline ImVec2 CalcWindowMinSize(ImGuiWindow* window)
 {
     // We give windows non-zero minimum size to facilitate understanding problematic cases (e.g. empty popups)
@@ -5770,7 +6066,7 @@
     }
 
     // Reduce artifacts with very small windows
-    ImGuiWindow* window_for_height = window;
+    ImGuiWindow* window_for_height = GetWindowForTitleAndMenuHeight(window);
     size_min.y = ImMax(size_min.y, window_for_height->TitleBarHeight() + window_for_height->MenuBarHeight() + ImMax(0.0f, g.Style.WindowRounding - 1.0f));
     return size_min;
 }
@@ -5841,8 +6137,11 @@
     {
         // Maximum window size is determined by the viewport size or monitor size
         ImVec2 size_min = CalcWindowMinSize(window);
-        ImVec2 size_max = ((window->Flags & ImGuiWindowFlags_ChildWindow) && !(window->Flags & ImGuiWindowFlags_Popup)) ? ImVec2(FLT_MAX, FLT_MAX) : ImGui::GetMainViewport()->WorkSize - style.DisplaySafeAreaPadding * 2.0f;
-        ImVec2 size_auto_fit = ImClamp(size_desired, size_min, size_max);
+        ImVec2 size_max = (window->ViewportOwned || ((window->Flags & ImGuiWindowFlags_ChildWindow) && !(window->Flags & ImGuiWindowFlags_Popup))) ? ImVec2(FLT_MAX, FLT_MAX) : ImGui::GetMainViewport()->WorkSize - style.DisplaySafeAreaPadding * 2.0f;
+        const int monitor_idx = window->ViewportAllowPlatformMonitorExtend;
+        if (monitor_idx >= 0 && monitor_idx < g.PlatformIO.Monitors.Size && (window->Flags & ImGuiWindowFlags_ChildWindow) == 0)
+            size_max = g.PlatformIO.Monitors[monitor_idx].WorkSize - style.DisplaySafeAreaPadding * 2.0f;
+        ImVec2 size_auto_fit = ImClamp(size_desired, size_min, ImMax(size_min, size_max));
 
         // When the window cannot fit all contents (either because of constraints, either because screen is too small),
         // we are growing the size on the other axis to compensate for expected scrollbar. FIXME: Might turn bigger than ViewportSize-WindowPadding.
@@ -5871,7 +6170,7 @@
 {
     if (window->Flags & (ImGuiWindowFlags_Tooltip | ImGuiWindowFlags_Popup))
         return ImGuiCol_PopupBg;
-    if (window->Flags & ImGuiWindowFlags_ChildWindow)
+    if ((window->Flags & ImGuiWindowFlags_ChildWindow) && !window->DockIsActive)
         return ImGuiCol_ChildBg;
     return ImGuiCol_WindowBg;
 }
@@ -5937,7 +6236,7 @@
 ImGuiID ImGui::GetWindowResizeCornerID(ImGuiWindow* window, int n)
 {
     IM_ASSERT(n >= 0 && n < 4);
-    ImGuiID id = window->ID;
+    ImGuiID id = window->DockIsActive ? window->DockNode->HostWindow->ID : window->ID;
     id = ImHashStr("#RESIZE", 0, id);
     id = ImHashData(&n, sizeof(int), id);
     return id;
@@ -5948,7 +6247,7 @@
 {
     IM_ASSERT(dir >= 0 && dir < 4);
     int n = (int)dir + 4;
-    ImGuiID id = window->ID;
+    ImGuiID id = window->DockIsActive ? window->DockNode->HostWindow->ID : window->ID;
     id = ImHashStr("#RESIZE", 0, id);
     id = ImHashData(&n, sizeof(int), id);
     return id;
@@ -5979,6 +6278,16 @@
     ImVec2 pos_target(FLT_MAX, FLT_MAX);
     ImVec2 size_target(FLT_MAX, FLT_MAX);
 
+    // Clip mouse interaction rectangles within the viewport rectangle (in practice the narrowing is going to happen most of the time).
+    // - Not narrowing would mostly benefit the situation where OS windows _without_ decoration have a threshold for hovering when outside their limits.
+    //   This is however not the case with current backends under Win32, but a custom borderless window implementation would benefit from it.
+    // - When decoration are enabled we typically benefit from that distance, but then our resize elements would be conflicting with OS resize elements, so we also narrow.
+    // - Note that we are unable to tell if the platform setup allows hovering with a distance threshold (on Win32, decorated window have such threshold).
+    // We only clip interaction so we overwrite window->ClipRect, cannot call PushClipRect() yet as DrawList is not yet setup.
+    const bool clip_with_viewport_rect = !(g.IO.BackendFlags & ImGuiBackendFlags_HasMouseHoveredViewport) || (g.IO.MouseHoveredViewport != window->ViewportId) || !(window->Viewport->Flags & ImGuiViewportFlags_NoDecoration);
+    if (clip_with_viewport_rect)
+        window->ClipRect = window->Viewport->GetMainRect();
+
     // Resize grips and borders are on layer 1
     window->DC.NavLayerCurrent = ImGuiNavLayer_Menu;
 
@@ -6063,7 +6372,7 @@
             // Switch to relative resizing mode when border geometry moved (e.g. resizing a child altering parent scroll), in order to avoid resizing feedback loop.
             // Currently only using relative mode on resizable child windows, as the problem to solve is more likely noticeable for them, but could apply for all windows eventually.
             // FIXME: May want to generalize this idiom at lower-level, so more widgets can use it!
-            const bool just_scrolled_manually_while_resizing = (g.WheelingWindow != NULL && g.WheelingWindowScrolledFrame == g.FrameCount && IsWindowChildOf(window, g.WheelingWindow, false));
+            const bool just_scrolled_manually_while_resizing = (g.WheelingWindow != NULL && g.WheelingWindowScrolledFrame == g.FrameCount && IsWindowChildOf(window, g.WheelingWindow, false, true));
             if (g.ActiveIdIsJustActivated || just_scrolled_manually_while_resizing)
             {
                 g.WindowResizeBorderExpectedRect = border_rect;
@@ -6120,7 +6429,7 @@
     // Navigation resize (keyboard/gamepad)
     // FIXME: This cannot be moved to NavUpdateWindowing() because CalcWindowSizeAfterConstraint() need to callback into user.
     // Not even sure the callback works here.
-    if (g.NavWindowingTarget && g.NavWindowingTarget->RootWindow == window)
+    if (g.NavWindowingTarget && g.NavWindowingTarget->RootWindowDockTree == window)
     {
         ImVec2 nav_resize_dir;
         if (g.NavInputSource == ImGuiInputSource_Keyboard && g.IO.KeyShift)
@@ -6171,8 +6480,8 @@
 {
     ImGuiContext& g = *GImGui;
     ImVec2 size_for_clamping = window->Size;
-    if (g.IO.ConfigWindowsMoveFromTitleBarOnly && !(window->Flags & ImGuiWindowFlags_NoTitleBar))
-        size_for_clamping.y = window->TitleBarHeight();
+    if (g.IO.ConfigWindowsMoveFromTitleBarOnly && (!(window->Flags & ImGuiWindowFlags_NoTitleBar) || window->DockNodeAsHost))
+        size_for_clamping.y = ImGui::GetFrameHeight(); // Not using window->TitleBarHeight() as DockNodeAsHost will report 0.0f here.
     window->Pos = ImClamp(window->Pos, visibility_rect.Min - size_for_clamping, visibility_rect.Max);
 }
 
@@ -6206,7 +6515,7 @@
         const ImU32 border_col_resizing = GetColorU32((window->ResizeBorderHeld != -1) ? ImGuiCol_SeparatorActive : ImGuiCol_SeparatorHovered);
         RenderWindowOuterSingleBorder(window, border_n, border_col_resizing, ImMax(2.0f, window->WindowBorderSize)); // Thicker than usual
     }
-    if (g.Style.FrameBorderSize > 0 && !(window->Flags & ImGuiWindowFlags_NoTitleBar))
+    if (g.Style.FrameBorderSize > 0 && !(window->Flags & ImGuiWindowFlags_NoTitleBar) && !window->DockIsActive)
     {
         float y = window->Pos.y + window->TitleBarHeight() - 1;
         window->DrawList->AddLine(ImVec2(window->Pos.x + border_size, y), ImVec2(window->Pos.x + window->Size.x - border_size, y), border_col, g.Style.FrameBorderSize);
@@ -6235,6 +6544,8 @@
         const float backup_border_size = style.FrameBorderSize;
         g.Style.FrameBorderSize = window->WindowBorderSize;
         ImU32 title_bar_col = GetColorU32((title_bar_is_highlight && !g.NavDisableHighlight) ? ImGuiCol_TitleBgActive : ImGuiCol_TitleBgCollapsed);
+        if (window->ViewportOwned)
+            title_bar_col |= IM_COL32_A_MASK; // No alpha (we don't support is_docking_transparent_payload here because simpler and less meaningful, but could with a bit of code shuffle/reuse)
         RenderFrame(title_bar_rect.Min, title_bar_rect.Max, title_bar_col, true, window_rounding);
         g.Style.FrameBorderSize = backup_border_size;
     }
@@ -6243,23 +6554,58 @@
         // Window background
         if (!(flags & ImGuiWindowFlags_NoBackground))
         {
+            bool is_docking_transparent_payload = false;
+            if (g.DragDropActive && (g.FrameCount - g.DragDropAcceptFrameCount) <= 1 && g.IO.ConfigDockingTransparentPayload)
+                if (g.DragDropPayload.IsDataType(IMGUI_PAYLOAD_TYPE_WINDOW) && *(ImGuiWindow**)g.DragDropPayload.Data == window)
+                    is_docking_transparent_payload = true;
+
             ImU32 bg_col = GetColorU32(GetWindowBgColorIdx(window));
-            bool override_alpha = false;
-            float alpha = 1.0f;
-            if (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasBgAlpha)
+            if (window->ViewportOwned)
             {
-                alpha = g.NextWindowData.BgAlphaVal;
-                override_alpha = true;
+                bg_col |= IM_COL32_A_MASK; // No alpha
+                if (is_docking_transparent_payload)
+                    window->Viewport->Alpha *= DOCKING_TRANSPARENT_PAYLOAD_ALPHA;
             }
-            if (override_alpha)
-                bg_col = (bg_col & ~IM_COL32_A_MASK) | (IM_F32_TO_INT8_SAT(alpha) << IM_COL32_A_SHIFT);
-            window->DrawList->AddRectFilled(window->Pos + ImVec2(0, window->TitleBarHeight()), window->Pos + window->Size, bg_col, window_rounding, (flags & ImGuiWindowFlags_NoTitleBar) ? 0 : ImDrawFlags_RoundCornersBottom);
+            else
+            {
+                // Adjust alpha. For docking
+                bool override_alpha = false;
+                float alpha = 1.0f;
+                if (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasBgAlpha)
+                {
+                    alpha = g.NextWindowData.BgAlphaVal;
+                    override_alpha = true;
+                }
+                if (is_docking_transparent_payload)
+                {
+                    alpha *= DOCKING_TRANSPARENT_PAYLOAD_ALPHA; // FIXME-DOCK: Should that be an override?
+                    override_alpha = true;
+                }
+                if (override_alpha)
+                    bg_col = (bg_col & ~IM_COL32_A_MASK) | (IM_F32_TO_INT8_SAT(alpha) << IM_COL32_A_SHIFT);
+            }
+
+            // Render, for docked windows and host windows we ensure bg goes before decorations
+            if (window->DockIsActive)
+                window->DockNode->LastBgColor = bg_col;
+            ImDrawList* bg_draw_list = window->DockIsActive ? window->DockNode->HostWindow->DrawList : window->DrawList;
+            if (window->DockIsActive || (flags & ImGuiWindowFlags_DockNodeHost))
+                bg_draw_list->ChannelsSetCurrent(DOCKING_HOST_DRAW_CHANNEL_BG);
+            bg_draw_list->AddRectFilled(window->Pos + ImVec2(0, window->TitleBarHeight()), window->Pos + window->Size, bg_col, window_rounding, (flags & ImGuiWindowFlags_NoTitleBar) ? 0 : ImDrawFlags_RoundCornersBottom);
+            if (window->DockIsActive || (flags & ImGuiWindowFlags_DockNodeHost))
+                bg_draw_list->ChannelsSetCurrent(DOCKING_HOST_DRAW_CHANNEL_FG);
         }
+        if (window->DockIsActive)
+            window->DockNode->IsBgDrawnThisFrame = true;
 
         // Title bar
-        if (!(flags & ImGuiWindowFlags_NoTitleBar))
+        // (when docked, DockNode are drawing their own title bar. Individual windows however do NOT set the _NoTitleBar flag,
+        // in order for their pos/size to be matching their undocking state.)
+        if (!(flags & ImGuiWindowFlags_NoTitleBar) && !window->DockIsActive)
         {
             ImU32 title_bar_col = GetColorU32(title_bar_is_highlight ? ImGuiCol_TitleBgActive : ImGuiCol_TitleBg);
+            if (window->ViewportOwned)
+                title_bar_col |= IM_COL32_A_MASK; // No alpha
             window->DrawList->AddRectFilled(title_bar_rect.Min, title_bar_rect.Max, title_bar_col, window_rounding, ImDrawFlags_RoundCornersTop);
         }
 
@@ -6273,6 +6619,27 @@
                 window->DrawList->AddLine(menu_bar_rect.GetBL(), menu_bar_rect.GetBR(), GetColorU32(ImGuiCol_Border), style.FrameBorderSize);
         }
 
+        // Docking: Unhide tab bar (small triangle in the corner), drag from small triangle to quickly undock
+        ImGuiDockNode* node = window->DockNode;
+        if (window->DockIsActive && node->IsHiddenTabBar() && !node->IsNoTabBar())
+        {
+            float unhide_sz_draw = ImTrunc(g.FontSize * 0.70f);
+            float unhide_sz_hit = ImTrunc(g.FontSize * 0.55f);
+            ImVec2 p = node->Pos;
+            ImRect r(p, p + ImVec2(unhide_sz_hit, unhide_sz_hit));
+            ImGuiID unhide_id = window->GetID("#UNHIDE");
+            KeepAliveID(unhide_id);
+            bool hovered, held;
+            if (ButtonBehavior(r, unhide_id, &hovered, &held, ImGuiButtonFlags_FlattenChildren))
+                node->WantHiddenTabBarToggle = true;
+            else if (held && IsMouseDragging(0))
+                StartMouseMovingWindowOrNode(window, node, true); // Undock from tab-bar triangle = same as window/collapse menu button
+
+            // FIXME-DOCK: Ideally we'd use ImGuiCol_TitleBgActive/ImGuiCol_TitleBg here, but neither is guaranteed to be visible enough at this sort of size..
+            ImU32 col = GetColorU32(((held && hovered) || (node->IsFocused && !hovered)) ? ImGuiCol_ButtonActive : hovered ? ImGuiCol_ButtonHovered : ImGuiCol_Button);
+            window->DrawList->AddTriangleFilled(p, p + ImVec2(unhide_sz_draw, 0.0f), p + ImVec2(0.0f, unhide_sz_draw), col);
+        }
+
         // Scrollbars
         if (window->ScrollbarX)
             Scrollbar(ImGuiAxis_X);
@@ -6296,12 +6663,13 @@
             }
         }
 
-        // Borders
-        if (handle_borders_and_resize_grips)
+        // Borders (for dock node host they will be rendered over after the tab bar)
+        if (handle_borders_and_resize_grips && !window->DockNodeAsHost)
             RenderWindowOuterBorders(window);
     }
 }
 
+// When inside a dock node, this is handled in DockNodeCalcTabBarLayout() instead.
 // Render title text, collapse button, close button
 void ImGui::RenderWindowTitleBarContents(ImGuiWindow* window, const ImRect& title_bar_rect, const char* name, bool* p_open)
 {
@@ -6343,7 +6711,7 @@
 
     // Collapse button (submitting first so it gets priority when choosing a navigation init fallback)
     if (has_collapse_button)
-        if (CollapseButton(window->GetID("#COLLAPSE"), collapse_button_pos))
+        if (CollapseButton(window->GetID("#COLLAPSE"), collapse_button_pos, NULL))
             window->WantCollapseToggle = true; // Defer actual collapsing to next frame as we are too far in the Begin() function
 
     // Close button
@@ -6394,12 +6762,16 @@
 void ImGui::UpdateWindowParentAndRootLinks(ImGuiWindow* window, ImGuiWindowFlags flags, ImGuiWindow* parent_window)
 {
     window->ParentWindow = parent_window;
-    window->RootWindow = window->RootWindowPopupTree = window->RootWindowForTitleBarHighlight = window->RootWindowForNav = window;
+    window->RootWindow = window->RootWindowPopupTree = window->RootWindowDockTree = window->RootWindowForTitleBarHighlight = window->RootWindowForNav = window;
     if (parent_window && (flags & ImGuiWindowFlags_ChildWindow) && !(flags & ImGuiWindowFlags_Tooltip))
-        window->RootWindow = parent_window->RootWindow;
+    {
+        window->RootWindowDockTree = parent_window->RootWindowDockTree;
+        if (!window->DockIsActive && !(parent_window->Flags & ImGuiWindowFlags_DockNodeHost))
+            window->RootWindow = parent_window->RootWindow;
+    }
     if (parent_window && (flags & ImGuiWindowFlags_Popup))
         window->RootWindowPopupTree = parent_window->RootWindowPopupTree;
-    if (parent_window && !(flags & ImGuiWindowFlags_Modal) && (flags & (ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_Popup)))
+    if (parent_window && !(flags & ImGuiWindowFlags_Modal) && (flags & (ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_Popup))) // FIXME: simply use _NoTitleBar ?
         window->RootWindowForTitleBarHighlight = parent_window->RootWindowForTitleBarHighlight;
     while (window->RootWindowForNav->Flags & ImGuiWindowFlags_NavFlattened)
     {
@@ -6504,22 +6876,24 @@
     const bool first_begin_of_the_frame = (window->LastFrameActive != current_frame);
     window->IsFallbackWindow = (g.CurrentWindowStack.Size == 0 && g.WithinFrameScopeWithImplicitWindow);
 
-    // Update the Appearing flag
-    bool window_just_activated_by_user = (window->LastFrameActive < current_frame - 1);   // Not using !WasActive because the implicit "Debug" window would always toggle off->on
+    // Update the Appearing flag (note: the BeginDocked() path may also set this to true later)
+    bool window_just_activated_by_user = (window->LastFrameActive < current_frame - 1); // Not using !WasActive because the implicit "Debug" window would always toggle off->on
     if (flags & ImGuiWindowFlags_Popup)
     {
         ImGuiPopupData& popup_ref = g.OpenPopupStack[g.BeginPopupStack.Size];
         window_just_activated_by_user |= (window->PopupId != popup_ref.PopupId); // We recycle popups so treat window as activated if popup id changed
         window_just_activated_by_user |= (window != popup_ref.Window);
     }
-    window->Appearing = window_just_activated_by_user;
-    if (window->Appearing)
-        SetWindowConditionAllowFlags(window, ImGuiCond_Appearing, true);
 
     // Update Flags, LastFrameActive, BeginOrderXXX fields
+    const bool window_was_appearing = window->Appearing;
     if (first_begin_of_the_frame)
     {
         UpdateWindowInFocusOrderList(window, window_just_created, flags);
+        window->Appearing = window_just_activated_by_user;
+        if (window->Appearing)
+            SetWindowConditionAllowFlags(window, ImGuiCond_Appearing, true);
+        window->FlagsPreviousFrame = window->Flags;
         window->Flags = (ImGuiWindowFlags)flags;
         window->ChildFlags = (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasChildFlags) ? g.NextWindowData.ChildFlags : 0;
         window->LastFrameActive = current_frame;
@@ -6532,8 +6906,42 @@
         flags = window->Flags;
     }
 
+    // Docking
+    // (NB: during the frame dock nodes are created, it is possible that (window->DockIsActive == false) even though (window->DockNode->Windows.Size > 1)
+    IM_ASSERT(window->DockNode == NULL || window->DockNodeAsHost == NULL); // Cannot be both
+    if (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasDock)
+        SetWindowDock(window, g.NextWindowData.DockId, g.NextWindowData.DockCond);
+    if (first_begin_of_the_frame)
+    {
+        bool has_dock_node = (window->DockId != 0 || window->DockNode != NULL);
+        bool new_auto_dock_node = !has_dock_node && GetWindowAlwaysWantOwnTabBar(window);
+        bool dock_node_was_visible = window->DockNodeIsVisible;
+        bool dock_tab_was_visible = window->DockTabIsVisible;
+        if (has_dock_node || new_auto_dock_node)
+        {
+            BeginDocked(window, p_open);
+            flags = window->Flags;
+            if (window->DockIsActive)
+            {
+                IM_ASSERT(window->DockNode != NULL);
+                g.NextWindowData.Flags &= ~ImGuiNextWindowDataFlags_HasSizeConstraint; // Docking currently override constraints
+            }
+
+            // Amend the Appearing flag
+            if (window->DockTabIsVisible && !dock_tab_was_visible && dock_node_was_visible && !window->Appearing && !window_was_appearing)
+            {
+                window->Appearing = true;
+                SetWindowConditionAllowFlags(window, ImGuiCond_Appearing, true);
+            }
+        }
+        else
+        {
+            window->DockIsActive = window->DockNodeIsVisible = window->DockTabIsVisible = false;
+        }
+    }
+
     // Parent window is latched only on the first call to Begin() of the frame, so further append-calls can be done from a different window stack
-    ImGuiWindow* parent_window_in_stack = g.CurrentWindowStack.empty() ? NULL : g.CurrentWindowStack.back().Window;
+    ImGuiWindow* parent_window_in_stack = (window->DockIsActive && window->DockNode->HostWindow) ? window->DockNode->HostWindow : g.CurrentWindowStack.empty() ? NULL : g.CurrentWindowStack.back().Window;
     ImGuiWindow* parent_window = first_begin_of_the_frame ? ((flags & (ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_Popup)) ? parent_window_in_stack : NULL) : window->ParentWindow;
     IM_ASSERT(parent_window != NULL || !(flags & ImGuiWindowFlags_ChildWindow));
 
@@ -6557,9 +6965,20 @@
         UpdateWindowParentAndRootLinks(window, flags, parent_window);
         window->ParentWindowInBeginStack = parent_window_in_stack;
 
+        // Focus route
         // There's little point to expose a flag to set this: because the interesting cases won't be using parent_window_in_stack,
-        // e.g. linking a tool window in a standalone viewport to a document window, regardless of their Begin() stack parenting. (#6798)
-        window->ParentWindowForFocusRoute = (flags & ImGuiWindowFlags_ChildWindow) ? parent_window_in_stack : NULL;
+        // Use for e.g. linking a tool window in a standalone viewport to a document window, regardless of their Begin() stack parenting. (#6798)
+        window->ParentWindowForFocusRoute = (window->RootWindow != window) ? parent_window_in_stack : NULL;
+        if (window->ParentWindowForFocusRoute == NULL && window->DockNode != NULL)
+            if (window->DockNode->MergedFlags & ImGuiDockNodeFlags_DockedWindowsInFocusRoute)
+                window->ParentWindowForFocusRoute = window->DockNode->HostWindow;
+
+        // Override with SetNextWindowClass() field or direct call to SetWindowParentWindowForFocusRoute()
+        if (window->WindowClass.FocusRouteParentWindowId != 0)
+        {
+            window->ParentWindowForFocusRoute = FindWindowByID(window->WindowClass.FocusRouteParentWindowId);
+            IM_ASSERT(window->ParentWindowForFocusRoute != 0); // Invalid value for FocusRouteParentWindowId.
+        }
     }
 
     // Add to focus scope stack
@@ -6623,6 +7042,8 @@
         window->ContentSizeExplicit = g.NextWindowData.ContentSizeVal;
     else if (first_begin_of_the_frame)
         window->ContentSizeExplicit = ImVec2(0.0f, 0.0f);
+    if (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasWindowClass)
+        window->WindowClass = g.NextWindowData.WindowClass;
     if (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasCollapsed)
         SetWindowCollapsed(window, g.NextWindowData.CollapsedVal, g.NextWindowData.CollapsedCond);
     if (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasFocus)
@@ -6648,6 +7069,11 @@
         window->IDStack.resize(1);
         window->DrawList->_ResetForNewFrame();
         window->DC.CurrentTableIdx = -1;
+        if (flags & ImGuiWindowFlags_DockNodeHost)
+        {
+            window->DrawList->ChannelsSplit(2);
+            window->DrawList->ChannelsSetCurrent(DOCKING_HOST_DRAW_CHANNEL_FG); // Render decorations on channel 1 as we will render the backgrounds manually later
+        }
 
         // Restore buffer capacity when woken from a compacted state, to avoid
         if (window->MemoryCompacted)
@@ -6656,7 +7082,9 @@
         // Update stored window name when it changes (which can _only_ happen with the "###" operator, so the ID would stay unchanged).
         // The title bar always display the 'name' parameter, so we only update the string storage if it needs to be visible to the end-user elsewhere.
         bool window_title_visible_elsewhere = false;
-        if (g.NavWindowingListWindow != NULL && (window->Flags & ImGuiWindowFlags_NoNavFocus) == 0)   // Window titles visible when using CTRL+TAB
+        if ((window->Viewport && window->Viewport->Window == window) || (window->DockIsActive))
+            window_title_visible_elsewhere = true;
+        else if (g.NavWindowingListWindow != NULL && (window->Flags & ImGuiWindowFlags_NoNavFocus) == 0)   // Window titles visible when using CTRL+TAB
             window_title_visible_elsewhere = true;
         if (window_title_visible_elsewhere && !window_just_created && strcmp(name, window->Name) != 0)
         {
@@ -6669,6 +7097,10 @@
 
         // Update contents size from last frame for auto-fitting (or use explicit size)
         CalcWindowContentSizes(window, &window->ContentSize, &window->ContentSizeIdeal);
+
+        // FIXME: These flags are decremented before they are used. This means that in order to have these fields produce their intended behaviors
+        // for one frame we must set them to at least 2, which is counter-intuitive. HiddenFramesCannotSkipItems is a more complicated case because
+        // it has a single usage before this code block and may be set below before it is finally checked.
         if (window->HiddenFramesCanSkipItems > 0)
             window->HiddenFramesCanSkipItems--;
         if (window->HiddenFramesCannotSkipItems > 0)
@@ -6696,20 +7128,23 @@
         }
 
         // SELECT VIEWPORT
-        // FIXME-VIEWPORT: In the docking/viewport branch, this is the point where we select the current viewport (which may affect the style)
+        // We need to do this before using any style/font sizes, as viewport with a different DPI may affect font sizes.
 
-        ImGuiViewportP* viewport = (ImGuiViewportP*)(void*)GetMainViewport();
-        SetWindowViewport(window, viewport);
+        WindowSelectViewport(window);
+        SetCurrentViewport(window, window->Viewport);
+        window->FontDpiScale = (g.IO.ConfigFlags & ImGuiConfigFlags_DpiEnableScaleFonts) ? window->Viewport->DpiScale : 1.0f;
         SetCurrentWindow(window);
+        flags = window->Flags;
 
         // LOCK BORDER SIZE AND PADDING FOR THE FRAME (so that altering them doesn't cause inconsistencies)
+        // We read Style data after the call to UpdateSelectWindowViewport() which might be swapping the style.
 
-        if (flags & ImGuiWindowFlags_ChildWindow)
+        if (!window->DockIsActive && (flags & ImGuiWindowFlags_ChildWindow))
             window->WindowBorderSize = style.ChildBorderSize;
         else
             window->WindowBorderSize = ((flags & (ImGuiWindowFlags_Popup | ImGuiWindowFlags_Tooltip)) && !(flags & ImGuiWindowFlags_Modal)) ? style.PopupBorderSize : style.WindowBorderSize;
         window->WindowPadding = style.WindowPadding;
-        if ((flags & ImGuiWindowFlags_ChildWindow) && !(flags & ImGuiWindowFlags_Popup) && !(window->ChildFlags & ImGuiChildFlags_AlwaysUseWindowPadding) && window->WindowBorderSize == 0.0f)
+        if (!window->DockIsActive && (flags & ImGuiWindowFlags_ChildWindow) && !(flags & ImGuiWindowFlags_Popup) && !(window->ChildFlags & ImGuiChildFlags_AlwaysUseWindowPadding) && window->WindowBorderSize == 0.0f)
             window->WindowPadding = ImVec2(0.0f, (flags & ImGuiWindowFlags_MenuBar) ? style.WindowPadding.y : 0.0f);
 
         // Lock menu offset so size calculation can use it as menu-bar windows need a minimum size.
@@ -6727,7 +7162,7 @@
 
         // Collapse window by double-clicking on title bar
         // At this point we don't have a clipping rectangle setup yet, so we can use the title bar area for hit detection and drawing
-        if (!(flags & ImGuiWindowFlags_NoTitleBar) && !(flags & ImGuiWindowFlags_NoCollapse))
+        if (!(flags & ImGuiWindowFlags_NoTitleBar) && !(flags & ImGuiWindowFlags_NoCollapse) && !window->DockIsActive)
         {
             // We don't use a regular button+id to test for double-click on title bar (mostly due to legacy reason, could be fixed), so verify that we don't have items over the title bar.
             ImRect title_bar_rect = window->TitleBarRect();
@@ -6827,23 +7262,66 @@
         else if ((flags & ImGuiWindowFlags_Tooltip) != 0 && !window_pos_set_by_api && !window_is_child_tooltip)
             window->Pos = FindBestWindowPosForPopup(window);
 
+        // Late create viewport if we don't fit within our current host viewport.
+        if (window->ViewportAllowPlatformMonitorExtend >= 0 && !window->ViewportOwned && !(window->Viewport->Flags & ImGuiViewportFlags_IsMinimized))
+            if (!window->Viewport->GetMainRect().Contains(window->Rect()))
+            {
+                // This is based on the assumption that the DPI will be known ahead (same as the DPI of the selection done in UpdateSelectWindowViewport)
+                //ImGuiViewport* old_viewport = window->Viewport;
+                window->Viewport = AddUpdateViewport(window, window->ID, window->Pos, window->Size, ImGuiViewportFlags_NoFocusOnAppearing);
+
+                // FIXME-DPI
+                //IM_ASSERT(old_viewport->DpiScale == window->Viewport->DpiScale); // FIXME-DPI: Something went wrong
+                SetCurrentViewport(window, window->Viewport);
+                window->FontDpiScale = (g.IO.ConfigFlags & ImGuiConfigFlags_DpiEnableScaleFonts) ? window->Viewport->DpiScale : 1.0f;
+                SetCurrentWindow(window);
+            }
+
+        if (window->ViewportOwned)
+            WindowSyncOwnedViewport(window, parent_window_in_stack);
+
         // Calculate the range of allowed position for that window (to be movable and visible past safe area padding)
         // When clamping to stay visible, we will enforce that window->Pos stays inside of visibility_rect.
-        ImRect viewport_rect(viewport->GetMainRect());
-        ImRect viewport_work_rect(viewport->GetWorkRect());
+        ImRect viewport_rect(window->Viewport->GetMainRect());
+        ImRect viewport_work_rect(window->Viewport->GetWorkRect());
         ImVec2 visibility_padding = ImMax(style.DisplayWindowPadding, style.DisplaySafeAreaPadding);
         ImRect visibility_rect(viewport_work_rect.Min + visibility_padding, viewport_work_rect.Max - visibility_padding);
 
         // Clamp position/size so window stays visible within its viewport or monitor
         // Ignore zero-sized display explicitly to avoid losing positions if a window manager reports zero-sized window when initializing or minimizing.
+        // FIXME: Similar to code in GetWindowAllowedExtentRect()
         if (!window_pos_set_by_api && !(flags & ImGuiWindowFlags_ChildWindow))
-            if (viewport_rect.GetWidth() > 0.0f && viewport_rect.GetHeight() > 0.0f)
+        {
+            if (!window->ViewportOwned && viewport_rect.GetWidth() > 0 && viewport_rect.GetHeight() > 0.0f)
+            {
                 ClampWindowPos(window, visibility_rect);
+            }
+            else if (window->ViewportOwned && g.PlatformIO.Monitors.Size > 0)
+            {
+                if (g.MovingWindow != NULL && window->RootWindowDockTree == g.MovingWindow->RootWindowDockTree)
+                {
+                    // While moving windows we allow them to straddle monitors (#7299, #3071)
+                    visibility_rect = g.PlatformMonitorsFullWorkRect;
+                }
+                else
+                {
+                    // When not moving ensure visible in its monitor
+                    // Lost windows (e.g. a monitor disconnected) will naturally moved to the fallback/dummy monitor aka the main viewport.
+                    const ImGuiPlatformMonitor* monitor = GetViewportPlatformMonitor(window->Viewport);
+                    visibility_rect = ImRect(monitor->WorkPos, monitor->WorkPos + monitor->WorkSize);
+                }
+                visibility_rect.Expand(-visibility_padding);
+                ClampWindowPos(window, visibility_rect);
+            }
+        }
         window->Pos = ImTrunc(window->Pos);
 
         // Lock window rounding for the frame (so that altering them doesn't cause inconsistencies)
         // Large values tend to lead to variety of artifacts and are not recommended.
-        window->WindowRounding = (flags & ImGuiWindowFlags_ChildWindow) ? style.ChildRounding : ((flags & ImGuiWindowFlags_Popup) && !(flags & ImGuiWindowFlags_Modal)) ? style.PopupRounding : style.WindowRounding;
+        if (window->ViewportOwned || window->DockIsActive)
+            window->WindowRounding = 0.0f;
+        else
+            window->WindowRounding = (flags & ImGuiWindowFlags_ChildWindow) ? style.ChildRounding : ((flags & ImGuiWindowFlags_Popup) && !(flags & ImGuiWindowFlags_Modal)) ? style.PopupRounding : style.WindowRounding;
 
         // For windows with title bar or menu bar, we clamp to FrameHeight(FontSize + FramePadding.y * 2.0f) to completely hide artifacts.
         //if ((window->Flags & ImGuiWindowFlags_MenuBar) || !(window->Flags & ImGuiWindowFlags_NoTitleBar))
@@ -6855,7 +7333,7 @@
         {
             if (flags & ImGuiWindowFlags_Popup)
                 want_focus = true;
-            else if ((flags & (ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_Tooltip)) == 0)
+            else if ((window->DockIsActive || (flags & ImGuiWindowFlags_ChildWindow) == 0) && !(flags & ImGuiWindowFlags_Tooltip))
                 want_focus = true;
         }
 
@@ -6871,12 +7349,15 @@
         }
 #endif
 
+        // Decide if we are going to handle borders and resize grips
+        const bool handle_borders_and_resize_grips = (window->DockNodeAsHost || !window->DockIsActive);
+
         // Handle manual resize: Resize Grips, Borders, Gamepad
         int border_hovered = -1, border_held = -1;
         ImU32 resize_grip_col[4] = {};
         const int resize_grip_count = ((flags & ImGuiWindowFlags_ChildWindow) && !(flags & ImGuiWindowFlags_Popup)) ? 0 : g.IO.ConfigWindowsResizeFromEdges ? 2 : 1; // Allow resize from lower-left if we have the mouse cursor feedback for it.
         const float resize_grip_draw_size = IM_TRUNC(ImMax(g.FontSize * 1.10f, window->WindowRounding + 1.0f + g.FontSize * 0.2f));
-        if (!window->Collapsed)
+        if (handle_borders_and_resize_grips && !window->Collapsed)
             if (int auto_fit_mask = UpdateWindowManualResize(window, size_auto_fit, &border_hovered, &border_held, resize_grip_count, &resize_grip_col[0], visibility_rect))
             {
                 if (auto_fit_mask & (1 << ImGuiAxis_X))
@@ -6887,6 +7368,20 @@
         window->ResizeBorderHovered = (signed char)border_hovered;
         window->ResizeBorderHeld = (signed char)border_held;
 
+        // Synchronize window --> viewport again and one last time (clamping and manual resize may have affected either)
+        if (window->ViewportOwned)
+        {
+            if (!window->Viewport->PlatformRequestMove)
+                window->Viewport->Pos = window->Pos;
+            if (!window->Viewport->PlatformRequestResize)
+                window->Viewport->Size = window->Size;
+            window->Viewport->UpdateWorkRect();
+            viewport_rect = window->Viewport->GetMainRect();
+        }
+
+        // Save last known viewport position within the window itself (so it can be saved in .ini file and restored)
+        window->ViewportPos = window->Viewport->Pos;
+
         // SCROLLBAR VISIBILITY
 
         // Update scrollbar visibility (based on the Size that was effective during last frame or the auto-resized Size).
@@ -6925,6 +7420,8 @@
         const ImRect outer_rect = window->Rect();
         const ImRect title_bar_rect = window->TitleBarRect();
         window->OuterRectClipped = outer_rect;
+        if (window->DockIsActive)
+            window->OuterRectClipped.Min.y += window->TitleBarHeight();
         window->OuterRectClipped.ClipWith(host_rect);
 
         // Inner rectangle
@@ -6983,6 +7480,8 @@
         // Child windows can render their decoration (bg color, border, scrollbars, etc.) within their parent to save a draw call (since 1.71)
         // When using overlapping child windows, this will break the assumption that child z-order is mapped to submission order.
         // FIXME: User code may rely on explicit sorting of overlapping child window and would need to disable this somehow. Please get in contact if you are affected (github #4493)
+        const bool is_undocked_or_docked_visible = !window->DockIsActive || window->DockTabIsVisible;
+        if (is_undocked_or_docked_visible)
         {
             bool render_decorations_in_parent = false;
             if ((flags & ImGuiWindowFlags_ChildWindow) && !(flags & ImGuiWindowFlags_Popup) && !window_is_child_tooltip)
@@ -7000,8 +7499,7 @@
 
             // Handle title bar, scrollbar, resize grips and resize borders
             const ImGuiWindow* window_to_highlight = g.NavWindowingTarget ? g.NavWindowingTarget : g.NavWindow;
-            const bool title_bar_is_highlight = want_focus || (window_to_highlight && window->RootWindowForTitleBarHighlight == window_to_highlight->RootWindowForTitleBarHighlight);
-            const bool handle_borders_and_resize_grips = true; // This exists to facilitate merge with 'docking' branch.
+            const bool title_bar_is_highlight = want_focus || (window_to_highlight && (window->RootWindowForTitleBarHighlight == window_to_highlight->RootWindowForTitleBarHighlight || (window->DockNode && window->DockNode == window_to_highlight->DockNode)));
             RenderWindowDecorations(window, title_bar_rect, title_bar_is_highlight, handle_borders_and_resize_grips, resize_grip_count, resize_grip_col, resize_grip_draw_size);
 
             if (render_decorations_in_parent)
@@ -7084,6 +7582,9 @@
         if (window->AutoFitFramesY > 0)
             window->AutoFitFramesY--;
 
+        // Clear SetNextWindowXXX data (can aim to move this higher in the function)
+        g.NextWindowData.ClearFlags();
+
         // Apply focus (we need to call FocusWindow() AFTER setting DC.CursorStartPos so our initial navigation reference rectangle can start around there)
         // We ImGuiFocusRequestFlags_UnlessBelowModal to:
         // - Avoid focusing a window that is created outside of a modal. This will prevent active modal from being closed.
@@ -7093,8 +7594,16 @@
         if (want_focus && window == g.NavWindow)
             NavInitWindow(window, false); // <-- this is in the way for us to be able to defer and sort reappearing FocusWindow() calls
 
+        // Close requested by platform window (apply to all windows in this viewport)
+        if (p_open != NULL && window->Viewport->PlatformRequestClose && window->Viewport != GetMainViewport())
+        {
+            IMGUI_DEBUG_LOG_VIEWPORT("[viewport] Window '%s' closed by PlatformRequestClose\n", window->Name);
+            *p_open = false;
+            g.NavWindowingToggleLayer = false; // Assume user mapped PlatformRequestClose on ALT-F4 so we disable ALT for menu toggle. False positive not an issue. // FIXME-NAV: Try removing.
+        }
+
         // Title bar
-        if (!(flags & ImGuiWindowFlags_NoTitleBar))
+        if (!(flags & ImGuiWindowFlags_NoTitleBar) && !window->DockIsActive)
             RenderWindowTitleBarContents(window, ImRect(title_bar_rect.Min.x + window->WindowBorderSize, title_bar_rect.Min.y, title_bar_rect.Max.x - window->WindowBorderSize, title_bar_rect.Max.y), name, p_open);
 
         // Clear hit test shape every frame
@@ -7110,6 +7619,20 @@
                 LogToClipboard();
         */
 
+        if (g.IO.ConfigFlags & ImGuiConfigFlags_DockingEnable)
+        {
+            // Docking: Dragging a dockable window (or any of its child) turns it into a drag and drop source.
+            // We need to do this _before_ we overwrite window->DC.LastItemId below because BeginDockableDragDropSource() also overwrites it.
+            if (g.MovingWindow == window && (window->RootWindowDockTree->Flags & ImGuiWindowFlags_NoDocking) == 0)
+                BeginDockableDragDropSource(window);
+
+            // Docking: Any dockable window can act as a target. For dock node hosts we call BeginDockableDragDropTarget() in DockNodeUpdate() instead.
+            if (g.DragDropActive && !(flags & ImGuiWindowFlags_NoDocking))
+                if (g.MovingWindow == NULL || g.MovingWindow->RootWindowDockTree != window)
+                    if ((window == window->RootWindowDockTree) && !(window->Flags & ImGuiWindowFlags_DockNodeHost))
+                        BeginDockableDragDropTarget(window);
+        }
+
         // We fill last item data based on Title Bar/Tab, in order for IsItemHovered() and IsItemActive() to be usable after Begin().
         // This is useful to allow creating context menus on title bar only, etc.
         SetLastItemDataForWindow(window, title_bar_rect);
@@ -7133,26 +7656,39 @@
             window->Active = true;
 
         // Append
+        SetCurrentViewport(window, window->Viewport);
         SetCurrentWindow(window);
+        g.NextWindowData.ClearFlags();
         SetLastItemDataForWindow(window, window->TitleBarRect());
     }
 
-    if (!window->SkipRefresh)
+    if (!(flags & ImGuiWindowFlags_DockNodeHost) && !window->SkipRefresh)
         PushClipRect(window->InnerClipRect.Min, window->InnerClipRect.Max, true);
 
     // Clear 'accessed' flag last thing (After PushClipRect which will set the flag. We want the flag to stay false when the default "Debug" window is unused)
     window->WriteAccessed = false;
     window->BeginCount++;
-    g.NextWindowData.ClearFlags();
 
     // Update visibility
     if (first_begin_of_the_frame && !window->SkipRefresh)
     {
+        // When we are about to select this tab (which will only be visible on the _next frame_), flag it with a non-zero HiddenFramesCannotSkipItems.
+        // This will have the important effect of actually returning true in Begin() and not setting SkipItems, allowing an earlier submission of the window contents.
+        // This is analogous to regular windows being hidden from one frame.
+        // It is especially important as e.g. nested TabBars would otherwise generate flicker in the form of one empty frame, or focus requests won't be processed.
+        if (window->DockIsActive && !window->DockTabIsVisible)
+        {
+            if (window->LastFrameJustFocused == g.FrameCount)
+                window->HiddenFramesCannotSkipItems = 1;
+            else
+                window->HiddenFramesCanSkipItems = 1;
+        }
+
         if ((flags & ImGuiWindowFlags_ChildWindow) && !(flags & ImGuiWindowFlags_ChildMenu))
         {
             // Child window can be out of sight and have "negative" clip windows.
             // Mark them as collapsed so commands are skipped earlier (we can't manually collapse them because they have no title bar).
-            IM_ASSERT((flags & ImGuiWindowFlags_NoTitleBar) != 0);
+            IM_ASSERT((flags& ImGuiWindowFlags_NoTitleBar) != 0 || window->DockIsActive);
             const bool nav_request = (flags & ImGuiWindowFlags_NavFlattened) && (g.NavAnyRequest && g.NavWindow && g.NavWindow->RootWindowForNav == window->RootWindowForNav);
             if (!g.LogEnabled && !nav_request)
                 if (window->OuterRectClipped.Min.x >= window->OuterRectClipped.Max.x || window->OuterRectClipped.Min.y >= window->OuterRectClipped.Max.y)
@@ -7191,6 +7727,16 @@
             if (window->AutoFitFramesX <= 0 && window->AutoFitFramesY <= 0 && window->HiddenFramesCannotSkipItems <= 0)
                 skip_items = true;
         window->SkipItems = skip_items;
+
+        // Restore NavLayersActiveMaskNext to previous value when not visible, so a CTRL+Tab back can use a safe value.
+        if (window->SkipItems)
+            window->DC.NavLayersActiveMaskNext = window->DC.NavLayersActiveMask;
+
+        // Sanity check: there are two spots which can set Appearing = true
+        // - when 'window_just_activated_by_user' is set -> HiddenFramesCannotSkipItems is set -> SkipItems always false
+        // - in BeginDocked() path when DockNodeIsVisible == DockTabIsVisible == true -> hidden _should_ be all zero // FIXME: Not formally proven, hence the assert.
+        if (window->SkipItems && !window->Appearing)
+            IM_ASSERT(window->Appearing == false); // Please report on GitHub if this triggers: https://github.com/ocornut/imgui/issues/4177
     }
     else if (first_begin_of_the_frame)
     {
@@ -7216,7 +7762,10 @@
 static void ImGui::SetLastItemDataForWindow(ImGuiWindow* window, const ImRect& rect)
 {
     ImGuiContext& g = *GImGui;
-    SetLastItemData(window->MoveId, g.CurrentItemFlags, IsMouseHoveringRect(rect.Min, rect.Max, false) ? ImGuiItemStatusFlags_HoveredRect : 0, rect);
+    if (window->DockIsActive)
+        SetLastItemData(window->MoveId, g.CurrentItemFlags, window->DockTabItemStatusFlags, window->DockTabItemRect);
+    else
+        SetLastItemData(window->MoveId, g.CurrentItemFlags, IsMouseHoveringRect(rect.Min, rect.Max, false) ? ImGuiItemStatusFlags_HoveredRect : 0, rect);
 }
 
 void ImGui::End()
@@ -7233,14 +7782,14 @@
     IM_ASSERT(g.CurrentWindowStack.Size > 0);
 
     // Error checking: verify that user doesn't directly call End() on a child window.
-    if (window->Flags & ImGuiWindowFlags_ChildWindow)
+    if ((window->Flags & ImGuiWindowFlags_ChildWindow) && !(window->Flags & ImGuiWindowFlags_DockNodeHost) && !window->DockIsActive)
         IM_ASSERT_USER_ERROR(g.WithinEndChild, "Must call EndChild() and not End()!");
 
     // Close anything that is open
     if (window->DC.CurrentColumns)
         EndColumns();
-    if (!window->SkipRefresh)
-        PopClipRect();   // Inner window clip rectangle
+    if (!(window->Flags & ImGuiWindowFlags_DockNodeHost) && !window->SkipRefresh)   // Pop inner window clip rectangle
+        PopClipRect();
     PopFocusScope();
 
     if (window->SkipRefresh)
@@ -7256,6 +7805,11 @@
     if (window->DC.IsSetPos)
         ErrorCheckUsingSetCursorPosToExtendParentBoundaries();
 
+    // Docking: report contents sizes to parent to allow for auto-resize
+    if (window->DockNode && window->DockTabIsVisible)
+        if (ImGuiWindow* host_window = window->DockNode->HostWindow)         // FIXME-DOCK
+            host_window->DC.CursorMaxPos = window->DC.CursorMaxPos + window->WindowPadding - host_window->WindowPadding;
+
     // Pop from window stack
     g.LastItemData = g.CurrentWindowStack.back().ParentLastItemDataBackup;
     if (window->Flags & ImGuiWindowFlags_ChildMenu)
@@ -7265,6 +7819,8 @@
     g.CurrentWindowStack.back().StackSizesOnBegin.CompareWithContextState(&g);
     g.CurrentWindowStack.pop_back();
     SetCurrentWindow(g.CurrentWindowStack.Size == 0 ? NULL : g.CurrentWindowStack.back().Window);
+    if (g.CurrentWindow)
+        SetCurrentViewport(g.CurrentWindow, g.CurrentWindow->Viewport);
 }
 
 void ImGui::BringWindowToFocusFront(ImGuiWindow* window)
@@ -7292,7 +7848,7 @@
 {
     ImGuiContext& g = *GImGui;
     ImGuiWindow* current_front_window = g.Windows.back();
-    if (current_front_window == window || current_front_window->RootWindow == window) // Cheap early out (could be better)
+    if (current_front_window == window || current_front_window->RootWindowDockTree == window) // Cheap early out (could be better)
         return;
     for (int i = g.Windows.Size - 2; i >= 0; i--) // We can ignore the top-most window
         if (g.Windows[i] == window)
@@ -7381,31 +7937,39 @@
     }
 
     // Move the root window to the top of the pile
-    IM_ASSERT(window == NULL || window->RootWindow != NULL);
-    ImGuiWindow* focus_front_window = window ? window->RootWindow : NULL; // NB: In docking branch this is window->RootWindowDockStop
-    ImGuiWindow* display_front_window = window ? window->RootWindow : NULL;
+    IM_ASSERT(window == NULL || window->RootWindowDockTree != NULL);
+    ImGuiWindow* focus_front_window = window ? window->RootWindow : NULL;
+    ImGuiWindow* display_front_window = window ? window->RootWindowDockTree : NULL;
+    ImGuiDockNode* dock_node = window ? window->DockNode : NULL;
+    bool active_id_window_is_dock_node_host = (g.ActiveIdWindow && dock_node && dock_node->HostWindow == g.ActiveIdWindow);
 
     // Steal active widgets. Some of the cases it triggers includes:
     // - Focus a window while an InputText in another window is active, if focus happens before the old InputText can run.
     // - When using Nav to activate menu items (due to timing of activating on press->new window appears->losing ActiveId)
+    // - Using dock host items (tab, collapse button) can trigger this before we redirect the ActiveIdWindow toward the child window.
     if (g.ActiveId != 0 && g.ActiveIdWindow && g.ActiveIdWindow->RootWindow != focus_front_window)
-        if (!g.ActiveIdNoClearOnFocusLoss)
+        if (!g.ActiveIdNoClearOnFocusLoss && !active_id_window_is_dock_node_host)
             ClearActiveID();
 
     // Passing NULL allow to disable keyboard focus
     if (!window)
         return;
+    window->LastFrameJustFocused = g.FrameCount;
+
+    // Select in dock node
+    // For #2304 we avoid applying focus immediately before the tabbar is visible.
+    //if (dock_node && dock_node->TabBar)
+    //    dock_node->TabBar->SelectedTabId = dock_node->TabBar->NextSelectedTabId = window->TabId;
 
     // Bring to front
     BringWindowToFocusFront(focus_front_window);
-    if (((window->Flags | display_front_window->Flags) & ImGuiWindowFlags_NoBringToFrontOnFocus) == 0)
+    if (((window->Flags | focus_front_window->Flags | display_front_window->Flags) & ImGuiWindowFlags_NoBringToFrontOnFocus) == 0)
         BringWindowToDisplayFront(display_front_window);
 }
 
 void ImGui::FocusTopMostWindowUnderOne(ImGuiWindow* under_this_window, ImGuiWindow* ignore_window, ImGuiViewport* filter_viewport, ImGuiFocusRequestFlags flags)
 {
     ImGuiContext& g = *GImGui;
-    IM_UNUSED(filter_viewport); // Unused in master branch.
     int start_idx = g.WindowsFocusOrder.Size - 1;
     if (under_this_window != NULL)
     {
@@ -7424,8 +7988,15 @@
         ImGuiWindow* window = g.WindowsFocusOrder[i];
         if (window == ignore_window || !window->WasActive)
             continue;
+        if (filter_viewport != NULL && window->Viewport != filter_viewport)
+            continue;
         if ((window->Flags & (ImGuiWindowFlags_NoMouseInputs | ImGuiWindowFlags_NoNavInputs)) != (ImGuiWindowFlags_NoMouseInputs | ImGuiWindowFlags_NoNavInputs))
         {
+            // FIXME-DOCK: When ImGuiFocusRequestFlags_RestoreFocusedChild is set...
+            // This is failing (lagging by one frame) for docked windows.
+            // If A and B are docked into window and B disappear, at the NewFrame() call site window->NavLastChildNavWindow will still point to B.
+            // We might leverage the tab order implicitly stored in window->DockNodeAsHost->TabBar (essentially the 'most_recently_selected_tab' code in tab bar will do that but on next update)
+            // to tell which is the "previous" window. Or we may leverage 'LastFrameFocused/LastFrameJustFocused' and have this function handle child window itself?
             FocusWindow(window, flags);
             return;
         }
@@ -7557,7 +8128,7 @@
     window->DC.TextWrapPosStack.pop_back();
 }
 
-static ImGuiWindow* GetCombinedRootWindow(ImGuiWindow* window, bool popup_hierarchy)
+static ImGuiWindow* GetCombinedRootWindow(ImGuiWindow* window, bool popup_hierarchy, bool dock_hierarchy)
 {
     ImGuiWindow* last_window = NULL;
     while (last_window != window)
@@ -7566,13 +8137,15 @@
         window = window->RootWindow;
         if (popup_hierarchy)
             window = window->RootWindowPopupTree;
-    }
+		if (dock_hierarchy)
+			window = window->RootWindowDockTree;
+	}
     return window;
 }
 
-bool ImGui::IsWindowChildOf(ImGuiWindow* window, ImGuiWindow* potential_parent, bool popup_hierarchy)
+bool ImGui::IsWindowChildOf(ImGuiWindow* window, ImGuiWindow* potential_parent, bool popup_hierarchy, bool dock_hierarchy)
 {
-    ImGuiWindow* window_root = GetCombinedRootWindow(window, popup_hierarchy);
+    ImGuiWindow* window_root = GetCombinedRootWindow(window, popup_hierarchy, dock_hierarchy);
     if (window_root == potential_parent)
         return true;
     while (window != NULL)
@@ -7637,12 +8210,13 @@
     {
         IM_ASSERT(cur_window); // Not inside a Begin()/End()
         const bool popup_hierarchy = (flags & ImGuiHoveredFlags_NoPopupHierarchy) == 0;
+        const bool dock_hierarchy = (flags & ImGuiHoveredFlags_DockHierarchy) != 0;
         if (flags & ImGuiHoveredFlags_RootWindow)
-            cur_window = GetCombinedRootWindow(cur_window, popup_hierarchy);
+            cur_window = GetCombinedRootWindow(cur_window, popup_hierarchy, dock_hierarchy);
 
         bool result;
         if (flags & ImGuiHoveredFlags_ChildWindows)
-            result = IsWindowChildOf(ref_window, cur_window, popup_hierarchy);
+            result = IsWindowChildOf(ref_window, cur_window, popup_hierarchy, dock_hierarchy);
         else
             result = (ref_window == cur_window);
         if (!result)
@@ -7681,15 +8255,28 @@
 
     IM_ASSERT(cur_window); // Not inside a Begin()/End()
     const bool popup_hierarchy = (flags & ImGuiFocusedFlags_NoPopupHierarchy) == 0;
+    const bool dock_hierarchy = (flags & ImGuiFocusedFlags_DockHierarchy) != 0;
     if (flags & ImGuiHoveredFlags_RootWindow)
-        cur_window = GetCombinedRootWindow(cur_window, popup_hierarchy);
+        cur_window = GetCombinedRootWindow(cur_window, popup_hierarchy, dock_hierarchy);
 
     if (flags & ImGuiHoveredFlags_ChildWindows)
-        return IsWindowChildOf(ref_window, cur_window, popup_hierarchy);
+        return IsWindowChildOf(ref_window, cur_window, popup_hierarchy, dock_hierarchy);
     else
         return (ref_window == cur_window);
 }
 
+ImGuiID ImGui::GetWindowDockID()
+{
+    ImGuiContext& g = *GImGui;
+    return g.CurrentWindow->DockId;
+}
+
+bool ImGui::IsWindowDocked()
+{
+    ImGuiContext& g = *GImGui;
+    return g.CurrentWindow->DockIsActive;
+}
+
 // Can we focus this window with CTRL+TAB (or PadMenu + PadFocusPrev/PadFocusNext)
 // Note that NoNavFocus makes the window not reachable with CTRL+TAB but it can still be focused with mouse or programmatically.
 // If you want a window to never be focused, you may use the e.g. NoInputs flag.
@@ -7734,6 +8321,7 @@
     if (offset.x == 0.0f && offset.y == 0.0f)
         return;
     MarkIniSettingsDirty(window);
+    // FIXME: share code with TranslateWindow(), need to confirm whether the 3 rect modified by TranslateWindow() are desirable here.
     window->DC.CursorPos += offset;         // As we happen to move the window while it is being appended to (which is a bad idea - will smear) let's at least offset the cursor
     window->DC.CursorMaxPos += offset;      // And more importantly we need to offset CursorMaxPos/CursorStartPos this so ContentSize calculation doesn't get affected.
     window->DC.IdealMaxPos += offset;
@@ -7871,6 +8459,7 @@
     g.NextWindowData.PosVal = pos;
     g.NextWindowData.PosPivotVal = pivot;
     g.NextWindowData.PosCond = cond ? cond : ImGuiCond_Always;
+    g.NextWindowData.PosUndock = true;
 }
 
 void ImGui::SetNextWindowSize(const ImVec2& size, ImGuiCond cond)
@@ -7933,6 +8522,29 @@
     g.NextWindowData.BgAlphaVal = alpha;
 }
 
+void ImGui::SetNextWindowViewport(ImGuiID id)
+{
+    ImGuiContext& g = *GImGui;
+    g.NextWindowData.Flags |= ImGuiNextWindowDataFlags_HasViewport;
+    g.NextWindowData.ViewportId = id;
+}
+
+void ImGui::SetNextWindowDockID(ImGuiID id, ImGuiCond cond)
+{
+    ImGuiContext& g = *GImGui;
+    g.NextWindowData.Flags |= ImGuiNextWindowDataFlags_HasDock;
+    g.NextWindowData.DockCond = cond ? cond : ImGuiCond_Always;
+    g.NextWindowData.DockId = id;
+}
+
+void ImGui::SetNextWindowClass(const ImGuiWindowClass* window_class)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT((window_class->ViewportFlagsOverrideSet & window_class->ViewportFlagsOverrideClear) == 0); // Cannot set both set and clear for the same bit
+    g.NextWindowData.Flags |= ImGuiNextWindowDataFlags_HasWindowClass;
+    g.NextWindowData.WindowClass = *window_class;
+}
+
 // This is experimental and meant to be a toy for exploring a future/wider range of features.
 void ImGui::SetNextWindowRefreshPolicy(ImGuiWindowRefreshFlags flags)
 {
@@ -7947,6 +8559,19 @@
     return window->DrawList;
 }
 
+float ImGui::GetWindowDpiScale()
+{
+    ImGuiContext& g = *GImGui;
+    return g.CurrentDpiScale;
+}
+
+ImGuiViewport* ImGui::GetWindowViewport()
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(g.CurrentViewport != NULL && g.CurrentViewport == g.CurrentWindow->Viewport);
+    return g.CurrentViewport;
+}
+
 ImFont* ImGui::GetFont()
 {
     return GImGui->Font;
@@ -8907,6 +9532,8 @@
     // Hit testing, expanded for touch input
     if (!rect_clipped.ContainsWithPad(g.IO.MousePos, g.Style.TouchExtraPadding))
         return false;
+    if (!g.MouseViewport->GetMainRect().Overlaps(rect_clipped))
+        return false;
     return true;
 }
 
@@ -9225,13 +9852,16 @@
             io.MouseClickedTime[i] = g.Time;
             io.MouseClickedPos[i] = io.MousePos;
             io.MouseClickedCount[i] = io.MouseClickedLastCount[i];
+            io.MouseDragMaxDistanceAbs[i] = ImVec2(0.0f, 0.0f);
             io.MouseDragMaxDistanceSqr[i] = 0.0f;
         }
         else if (io.MouseDown[i])
         {
             // Maintain the maximum distance we reaching from the initial click position, which is used with dragging threshold
-            float delta_sqr_click_pos = IsMousePosValid(&io.MousePos) ? ImLengthSqr(io.MousePos - io.MouseClickedPos[i]) : 0.0f;
-            io.MouseDragMaxDistanceSqr[i] = ImMax(io.MouseDragMaxDistanceSqr[i], delta_sqr_click_pos);
+            ImVec2 delta_from_click_pos = IsMousePosValid(&io.MousePos) ? (io.MousePos - io.MouseClickedPos[i]) : ImVec2(0.0f, 0.0f);
+            io.MouseDragMaxDistanceSqr[i] = ImMax(io.MouseDragMaxDistanceSqr[i], ImLengthSqr(delta_from_click_pos));
+            io.MouseDragMaxDistanceAbs[i].x = ImMax(io.MouseDragMaxDistanceAbs[i].x, delta_from_click_pos.x < 0.0f ? -delta_from_click_pos.x : delta_from_click_pos.x);
+            io.MouseDragMaxDistanceAbs[i].y = ImMax(io.MouseDragMaxDistanceAbs[i].y, delta_from_click_pos.y < 0.0f ? -delta_from_click_pos.y : delta_from_click_pos.y);
         }
 
         // We provide io.MouseDoubleClicked[] as a legacy service
@@ -9421,6 +10051,7 @@
     if (e->Type == ImGuiInputEventType_MousePos)    { if (e->MousePos.PosX == -FLT_MAX && e->MousePos.PosY == -FLT_MAX) IMGUI_DEBUG_LOG_IO("[io] %s: MousePos (-FLT_MAX, -FLT_MAX)\n", prefix); else IMGUI_DEBUG_LOG_IO("[io] %s: MousePos (%.1f, %.1f) (%s)\n", prefix, e->MousePos.PosX, e->MousePos.PosY, GetMouseSourceName(e->MousePos.MouseSource)); return; }
     if (e->Type == ImGuiInputEventType_MouseButton) { IMGUI_DEBUG_LOG_IO("[io] %s: MouseButton %d %s (%s)\n", prefix, e->MouseButton.Button, e->MouseButton.Down ? "Down" : "Up", GetMouseSourceName(e->MouseButton.MouseSource)); return; }
     if (e->Type == ImGuiInputEventType_MouseWheel)  { IMGUI_DEBUG_LOG_IO("[io] %s: MouseWheel (%.3f, %.3f) (%s)\n", prefix, e->MouseWheel.WheelX, e->MouseWheel.WheelY, GetMouseSourceName(e->MouseWheel.MouseSource)); return; }
+    if (e->Type == ImGuiInputEventType_MouseViewport){IMGUI_DEBUG_LOG_IO("[io] %s: MouseViewport (0x%08X)\n", prefix, e->MouseViewport.HoveredViewportID); return; }
     if (e->Type == ImGuiInputEventType_Key)         { IMGUI_DEBUG_LOG_IO("[io] %s: Key \"%s\" %s\n", prefix, ImGui::GetKeyName(e->Key.Key), e->Key.Down ? "Down" : "Up"); return; }
     if (e->Type == ImGuiInputEventType_Text)        { IMGUI_DEBUG_LOG_IO("[io] %s: Text: %c (U+%08X)\n", prefix, e->Text.Char, e->Text.Char); return; }
     if (e->Type == ImGuiInputEventType_Focus)       { IMGUI_DEBUG_LOG_IO("[io] %s: AppFocused %d\n", prefix, e->AppFocused.Focused); return; }
@@ -9484,6 +10115,10 @@
             io.MouseSource = e->MouseWheel.MouseSource;
             mouse_wheeled = true;
         }
+        else if (e->Type == ImGuiInputEventType_MouseViewport)
+        {
+            io.MouseHoveredViewport = e->MouseViewport.HoveredViewportID;
+        }
         else if (e->Type == ImGuiInputEventType_Key)
         {
             // Trickling Rule: Stop processing queued events if we got multiple action on the same button
@@ -9851,6 +10486,45 @@
     // Check: the io.ConfigWindowsResizeFromEdges option requires backend to honor mouse cursor changes and set the ImGuiBackendFlags_HasMouseCursors flag accordingly.
     if (g.IO.ConfigWindowsResizeFromEdges && !(g.IO.BackendFlags & ImGuiBackendFlags_HasMouseCursors))
         g.IO.ConfigWindowsResizeFromEdges = false;
+
+    // Perform simple check: error if Docking or Viewport are enabled _exactly_ on frame 1 (instead of frame 0 or later), which is a common error leading to loss of .ini data.
+    if (g.FrameCount == 1 && (g.IO.ConfigFlags & ImGuiConfigFlags_DockingEnable) && (g.ConfigFlagsLastFrame & ImGuiConfigFlags_DockingEnable) == 0)
+        IM_ASSERT(0 && "Please set DockingEnable before the first call to NewFrame()! Otherwise you will lose your .ini settings!");
+    if (g.FrameCount == 1 && (g.IO.ConfigFlags & ImGuiConfigFlags_ViewportsEnable) && (g.ConfigFlagsLastFrame & ImGuiConfigFlags_ViewportsEnable) == 0)
+        IM_ASSERT(0 && "Please set ViewportsEnable before the first call to NewFrame()! Otherwise you will lose your .ini settings!");
+
+    // Perform simple checks: multi-viewport and platform windows support
+    if (g.IO.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        if ((g.IO.BackendFlags & ImGuiBackendFlags_PlatformHasViewports) && (g.IO.BackendFlags & ImGuiBackendFlags_RendererHasViewports))
+        {
+            IM_ASSERT((g.FrameCount == 0 || g.FrameCount == g.FrameCountPlatformEnded) && "Forgot to call UpdatePlatformWindows() in main loop after EndFrame()? Check examples/ applications for reference.");
+            IM_ASSERT(g.PlatformIO.Platform_CreateWindow  != NULL && "Platform init didn't install handlers?");
+            IM_ASSERT(g.PlatformIO.Platform_DestroyWindow != NULL && "Platform init didn't install handlers?");
+            IM_ASSERT(g.PlatformIO.Platform_GetWindowPos  != NULL && "Platform init didn't install handlers?");
+            IM_ASSERT(g.PlatformIO.Platform_SetWindowPos  != NULL && "Platform init didn't install handlers?");
+            IM_ASSERT(g.PlatformIO.Platform_GetWindowSize != NULL && "Platform init didn't install handlers?");
+            IM_ASSERT(g.PlatformIO.Platform_SetWindowSize != NULL && "Platform init didn't install handlers?");
+            IM_ASSERT(g.PlatformIO.Monitors.Size > 0 && "Platform init didn't setup Monitors list?");
+            IM_ASSERT((g.Viewports[0]->PlatformUserData != NULL || g.Viewports[0]->PlatformHandle != NULL) && "Platform init didn't setup main viewport.");
+            if (g.IO.ConfigDockingTransparentPayload && (g.IO.ConfigFlags & ImGuiConfigFlags_DockingEnable))
+                IM_ASSERT(g.PlatformIO.Platform_SetWindowAlpha != NULL && "Platform_SetWindowAlpha handler is required to use io.ConfigDockingTransparent!");
+        }
+        else
+        {
+            // Disable feature, our backends do not support it
+            g.IO.ConfigFlags &= ~ImGuiConfigFlags_ViewportsEnable;
+        }
+
+        // Perform simple checks on platform monitor data + compute a total bounding box for quick early outs
+        for (ImGuiPlatformMonitor& mon : g.PlatformIO.Monitors)
+        {
+            IM_UNUSED(mon);
+            IM_ASSERT(mon.MainSize.x > 0.0f && mon.MainSize.y > 0.0f && "Monitor main bounds not setup properly.");
+            IM_ASSERT(ImRect(mon.MainPos, mon.MainPos + mon.MainSize).Contains(ImRect(mon.WorkPos, mon.WorkPos + mon.WorkSize)) && "Monitor work bounds not setup properly. If you don't have work area information, just copy MainPos/MainSize into them.");
+            IM_ASSERT(mon.DpiScale != 0.0f);
+        }
+    }
 }
 
 static void ImGui::ErrorCheckEndFrameSanityChecks()
@@ -10856,7 +11530,7 @@
                 SetWindowHiddenAndSkipItemsForCurrentFrame(window);
                 ImFormatString(window_name, IM_ARRAYSIZE(window_name), "##Tooltip_%02d", ++g.TooltipOverrideCount);
             }
-    ImGuiWindowFlags flags = ImGuiWindowFlags_Tooltip | ImGuiWindowFlags_NoInputs | ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_AlwaysAutoResize;
+    ImGuiWindowFlags flags = ImGuiWindowFlags_Tooltip | ImGuiWindowFlags_NoInputs | ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_AlwaysAutoResize | ImGuiWindowFlags_NoDocking;
     Begin(window_name, NULL, flags | extra_window_flags);
     // 2023-03-09: Added bool return value to the API, but currently always returning true.
     // If this ever returns false we need to update BeginDragDropSource() accordingly.
@@ -10929,8 +11603,8 @@
         if (popup_flags & ImGuiPopupFlags_AnyPopupLevel)
         {
             // Return true if the popup is open anywhere in the popup stack
-            for (int n = 0; n < g.OpenPopupStack.Size; n++)
-                if (g.OpenPopupStack[n].PopupId == id)
+            for (ImGuiPopupData& popup_data : g.OpenPopupStack)
+                if (popup_data.PopupId == id)
                     return true;
             return false;
         }
@@ -11069,12 +11743,13 @@
             //     Window -> Popup1 -> Window2(Ref)
             // - Clicking/focusing Popup1 will close Popup2 and Popup3:
             //     Window -> Popup1(Ref) -> Popup2 -> Popup3
-            // - Each popups may contain child windows, which is why we compare ->RootWindow!
+            // - Each popups may contain child windows, which is why we compare ->RootWindowDockTree!
             //     Window -> Popup1 -> Popup1_Child -> Popup2 -> Popup2_Child
             // We step through every popup from bottom to top to validate their position relative to reference window.
             bool ref_window_is_descendent_of_popup = false;
             for (int n = popup_count_to_keep; n < g.OpenPopupStack.Size; n++)
                 if (ImGuiWindow* popup_window = g.OpenPopupStack[n].Window)
+                    //if (popup_window->RootWindowDockTree == ref_window->RootWindowDockTree) // FIXME-MERGE
                     if (IsWindowWithinBeginStackOf(ref_window, popup_window))
                     {
                         ref_window_is_descendent_of_popup = true;
@@ -11175,7 +11850,7 @@
     else
         ImFormatString(name, IM_ARRAYSIZE(name), "##Popup_%08x", id); // Not recycling, so we can close/open during the same frame
 
-    flags |= ImGuiWindowFlags_Popup;
+    flags |= ImGuiWindowFlags_Popup | ImGuiWindowFlags_NoDocking;
     bool is_open = Begin(name, NULL, flags);
     if (!is_open) // NB: Begin can return false when the popup is completely clipped (e.g. zero size display)
         EndPopup();
@@ -11220,11 +11895,11 @@
     // FIXME: Should test for (PosCond & window->SetWindowPosAllowFlags) with the upcoming window.
     if ((g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasPos) == 0)
     {
-        const ImGuiViewport* viewport = GetMainViewport();
+        const ImGuiViewport* viewport = window->WasActive ? window->Viewport : GetMainViewport(); // FIXME-VIEWPORT: What may be our reference viewport?
         SetNextWindowPos(viewport->GetCenter(), ImGuiCond_FirstUseEver, ImVec2(0.5f, 0.5f));
     }
 
-    flags |= ImGuiWindowFlags_Popup | ImGuiWindowFlags_Modal | ImGuiWindowFlags_NoCollapse;
+    flags |= ImGuiWindowFlags_Popup | ImGuiWindowFlags_Modal | ImGuiWindowFlags_NoCollapse | ImGuiWindowFlags_NoDocking;
     const bool is_open = Begin(name, p_open, flags);
     if (!is_open || (p_open && !*p_open)) // NB: is_open can be 'false' when the popup is completely clipped (e.g. zero size display)
     {
@@ -11411,8 +12086,19 @@
 ImRect ImGui::GetPopupAllowedExtentRect(ImGuiWindow* window)
 {
     ImGuiContext& g = *GImGui;
-    IM_UNUSED(window);
-    ImRect r_screen = ((ImGuiViewportP*)(void*)GetMainViewport())->GetMainRect();
+    ImRect r_screen;
+    if (window->ViewportAllowPlatformMonitorExtend >= 0)
+    {
+        // Extent with be in the frame of reference of the given viewport (so Min is likely to be negative here)
+        const ImGuiPlatformMonitor& monitor = g.PlatformIO.Monitors[window->ViewportAllowPlatformMonitorExtend];
+        r_screen.Min = monitor.WorkPos;
+        r_screen.Max = monitor.WorkPos + monitor.WorkSize;
+    }
+    else
+    {
+        // Use the full viewport area (not work area) for popups
+        r_screen = window->Viewport->GetMainRect();
+    }
     ImVec2 padding = g.Style.DisplaySafeAreaPadding;
     r_screen.Expand(ImVec2((r_screen.GetWidth() > padding.x * 2) ? -padding.x : 0.0f, (r_screen.GetHeight() > padding.y * 2) ? -padding.y : 0.0f));
     return r_screen;
@@ -11427,8 +12113,7 @@
     {
         // Child menus typically request _any_ position within the parent menu item, and then we move the new menu outside the parent bounds.
         // This is how we end up with child menus appearing (most-commonly) on the right of the parent menu.
-        IM_ASSERT(g.CurrentWindow == window);
-        ImGuiWindow* parent_window = g.CurrentWindowStack[g.CurrentWindowStack.Size - 2].Window;
+        ImGuiWindow* parent_window = window->ParentWindow;
         float horizontal_overlap = g.Style.ItemInnerSpacing.x; // We want some overlap to convey the relative depth of each menu (currently the amount of overlap is hard-coded to style.ItemSpacing.x).
         ImRect r_avoid;
         if (parent_window->DC.MenuBarAppending)
@@ -11966,6 +12651,9 @@
 {
     if (window->NavLastChildNavWindow && window->NavLastChildNavWindow->WasActive)
         return window->NavLastChildNavWindow;
+    if (window->DockNodeAsHost && window->DockNodeAsHost->TabBar)
+        if (ImGuiTabItem* tab = TabBarFindMostRecentlySelectedTabForActiveWindow(window->DockNodeAsHost->TabBar))
+            return tab->Window;
     return window;
 }
 
@@ -12010,6 +12698,7 @@
 // This needs to be called before we submit any widget (aka in or before Begin)
 void ImGui::NavInitWindow(ImGuiWindow* window, bool force_reinit)
 {
+    // FIXME: ChildWindow test here is wrong for docking
     ImGuiContext& g = *GImGui;
     IM_ASSERT(window == g.NavWindow);
 
@@ -12070,7 +12759,7 @@
             ref_rect.Translate(window->Scroll - next_scroll);
         }
         ImVec2 pos = ImVec2(ref_rect.Min.x + ImMin(g.Style.FramePadding.x * 4, ref_rect.GetWidth()), ref_rect.Max.y - ImMin(g.Style.FramePadding.y, ref_rect.GetHeight()));
-        ImGuiViewport* viewport = GetMainViewport();
+        ImGuiViewport* viewport = window->Viewport;
         return ImTrunc(ImClamp(pos, viewport->Pos, viewport->Pos + viewport->Size)); // ImTrunc() is important because non-integer mouse position application in backend might be lossy and result in undesirable non-zero delta.
     }
 }
@@ -12941,7 +13630,7 @@
             ImVec2 accum_floored = ImTrunc(g.NavWindowingAccumDeltaPos);
             if (accum_floored.x != 0.0f || accum_floored.y != 0.0f)
             {
-                ImGuiWindow* moving_window = g.NavWindowingTarget->RootWindow;
+                ImGuiWindow* moving_window = g.NavWindowingTarget->RootWindowDockTree;
                 SetWindowPos(moving_window, moving_window->Pos + accum_floored, ImGuiCond_Always);
                 g.NavWindowingAccumDeltaPos -= accum_floored;
             }
@@ -12951,6 +13640,9 @@
     // Apply final focus
     if (apply_focus_window && (g.NavWindow == NULL || apply_focus_window != g.NavWindow->RootWindow))
     {
+        // FIXME: Many actions here could be part of a higher-level/reused function. Why aren't they in FocusWindow()
+        // Investigate for each of them: ClearActiveID(), NavRestoreHighlightAfterMove(), NavRestoreLastChildNavWindow(), ClosePopupsOverWindow(), NavInitWindow()
+        ImGuiViewport* previous_viewport = g.NavWindow ? g.NavWindow->Viewport : NULL;
         ClearActiveID();
         NavRestoreHighlightAfterMove();
         ClosePopupsOverWindow(apply_focus_window, false);
@@ -12968,6 +13660,10 @@
         // won't be valid.
         if (apply_focus_window->DC.NavLayersActiveMaskNext == (1 << ImGuiNavLayer_Menu))
             g.NavLayer = ImGuiNavLayer_Menu;
+
+        // Request OS level focus
+        if (apply_focus_window->Viewport != previous_viewport && g.PlatformIO.Platform_SetWindowFocus)
+            g.PlatformIO.Platform_SetWindowFocus(apply_focus_window->Viewport);
     }
     if (apply_focus_window)
         g.NavWindowingTarget = NULL;
@@ -12996,7 +13692,8 @@
         if (new_nav_layer != g.NavLayer)
         {
             // Reinitialize navigation when entering menu bar with the Alt key (FIXME: could be a properly of the layer?)
-            if (new_nav_layer == ImGuiNavLayer_Menu)
+            const bool preserve_layer_1_nav_id = (new_nav_window->DockNodeAsHost != NULL);
+            if (new_nav_layer == ImGuiNavLayer_Menu && !preserve_layer_1_nav_id)
                 g.NavWindow->NavLastIds[new_nav_layer] = 0;
             NavRestoreLayer(new_nav_layer);
             NavRestoreHighlightAfterMove();
@@ -13011,6 +13708,8 @@
         return ImGui::LocalizeGetMsg(ImGuiLocKey_WindowingPopup);
     if ((window->Flags & ImGuiWindowFlags_MenuBar) && strcmp(window->Name, "##MainMenuBar") == 0)
         return ImGui::LocalizeGetMsg(ImGuiLocKey_WindowingMainMenuBar);
+    if (window->DockNodeAsHost)
+        return "(Dock node)"; // Not normally shown to user.
     return ImGui::LocalizeGetMsg(ImGuiLocKey_WindowingUntitled);
 }
 
@@ -13025,7 +13724,7 @@
 
     if (g.NavWindowingListWindow == NULL)
         g.NavWindowingListWindow = FindWindowByName("###NavWindowingList");
-    const ImGuiViewport* viewport = GetMainViewport();
+    const ImGuiViewport* viewport = /*g.NavWindow ? g.NavWindow->Viewport :*/ GetMainViewport();
     SetNextWindowSizeConstraints(ImVec2(viewport->Size.x * 0.20f, viewport->Size.y * 0.20f), ImVec2(FLT_MAX, FLT_MAX));
     SetNextWindowPos(viewport->GetCenter(), ImGuiCond_Always, ImVec2(0.5f, 0.5f));
     PushStyleVar(ImGuiStyleVar_WindowPadding, g.Style.WindowPadding * 2.0f);
@@ -13266,7 +13965,7 @@
 
     ImGuiWindow* window = g.CurrentWindow;
     ImGuiWindow* hovered_window = g.HoveredWindowUnderMovingWindow;
-    if (hovered_window == NULL || window->RootWindow != hovered_window->RootWindow)
+    if (hovered_window == NULL || window->RootWindowDockTree != hovered_window->RootWindowDockTree)
         return false;
     IM_ASSERT(id != 0);
     if (!IsMouseHoveringRect(bb.Min, bb.Max) || (id == g.DragDropPayload.SourceId))
@@ -13296,7 +13995,7 @@
     if (!(g.LastItemData.StatusFlags & ImGuiItemStatusFlags_HoveredRect))
         return false;
     ImGuiWindow* hovered_window = g.HoveredWindowUnderMovingWindow;
-    if (hovered_window == NULL || window->RootWindow != hovered_window->RootWindow || window->SkipItems)
+    if (hovered_window == NULL || window->RootWindowDockTree != hovered_window->RootWindowDockTree || window->SkipItems)
         return false;
 
     const ImRect& display_rect = (g.LastItemData.StatusFlags & ImGuiItemStatusFlags_HasDisplayRect) ? g.LastItemData.DisplayRect : g.LastItemData.Rect;
@@ -13897,11 +14596,14 @@
 void ImGui::ClearWindowSettings(const char* name)
 {
     //IMGUI_DEBUG_LOG("ClearWindowSettings('%s')\n", name);
+    ImGuiContext& g = *GImGui;
     ImGuiWindow* window = FindWindowByName(name);
     if (window != NULL)
     {
         window->Flags |= ImGuiWindowFlags_NoSavedSettings;
         InitOrLoadWindowSettings(window, NULL);
+        if (window->DockId != 0)
+            DockContextProcessUndockWindow(&g, window, true);
     }
     if (ImGuiWindowSettings* settings = window ? FindWindowSettingsByWindow(window) : FindWindowSettingsByID(ImHashStr(name)))
         settings->WantDelete = true;
@@ -13933,10 +14635,16 @@
     ImGuiWindowSettings* settings = (ImGuiWindowSettings*)entry;
     int x, y;
     int i;
-    if (sscanf(line, "Pos=%i,%i", &x, &y) == 2)         { settings->Pos = ImVec2ih((short)x, (short)y); }
-    else if (sscanf(line, "Size=%i,%i", &x, &y) == 2)   { settings->Size = ImVec2ih((short)x, (short)y); }
-    else if (sscanf(line, "Collapsed=%d", &i) == 1)     { settings->Collapsed = (i != 0); }
-    else if (sscanf(line, "IsChild=%d", &i) == 1)       { settings->IsChild = (i != 0); }
+    ImU32 u1;
+    if (sscanf(line, "Pos=%i,%i", &x, &y) == 2)             { settings->Pos = ImVec2ih((short)x, (short)y); }
+    else if (sscanf(line, "Size=%i,%i", &x, &y) == 2)       { settings->Size = ImVec2ih((short)x, (short)y); }
+    else if (sscanf(line, "ViewportId=0x%08X", &u1) == 1)   { settings->ViewportId = u1; }
+    else if (sscanf(line, "ViewportPos=%i,%i", &x, &y) == 2){ settings->ViewportPos = ImVec2ih((short)x, (short)y); }
+    else if (sscanf(line, "Collapsed=%d", &i) == 1)         { settings->Collapsed = (i != 0); }
+    else if (sscanf(line, "IsChild=%d", &i) == 1)           { settings->IsChild = (i != 0); }
+    else if (sscanf(line, "DockId=0x%X,%d", &u1, &i) == 2)  { settings->DockId = u1; settings->DockOrder = (short)i; }
+    else if (sscanf(line, "DockId=0x%X", &u1) == 1)         { settings->DockId = u1; settings->DockOrder = -1; }
+    else if (sscanf(line, "ClassId=0x%X", &u1) == 1)        { settings->ClassId = u1; }
 }
 
 // Apply to existing windows (if any)
@@ -13969,10 +14677,16 @@
             window->SettingsOffset = g.SettingsWindows.offset_from_ptr(settings);
         }
         IM_ASSERT(settings->ID == window->ID);
-        settings->Pos = ImVec2ih(window->Pos);
+        settings->Pos = ImVec2ih(window->Pos - window->ViewportPos);
         settings->Size = ImVec2ih(window->SizeFull);
-        settings->IsChild = (window->Flags & ImGuiWindowFlags_ChildWindow) != 0;
+        settings->ViewportId = window->ViewportId;
+        settings->ViewportPos = ImVec2ih(window->ViewportPos);
+        IM_ASSERT(window->DockNode == NULL || window->DockNode->ID == window->DockId);
+        settings->DockId = window->DockId;
+        settings->ClassId = window->WindowClass.ClassId;
+        settings->DockOrder = window->DockOrder;
         settings->Collapsed = window->Collapsed;
+        settings->IsChild = (window->RootWindow != window); // Cannot rely on ImGuiWindowFlags_ChildWindow here as docked windows have this set.
         settings->WantDelete = false;
     }
 
@@ -13991,10 +14705,26 @@
         }
         else
         {
-            buf->appendf("Pos=%d,%d\n", settings->Pos.x, settings->Pos.y);
-            buf->appendf("Size=%d,%d\n", settings->Size.x, settings->Size.y);
-            if (settings->Collapsed)
-                buf->appendf("Collapsed=1\n");
+            if (settings->ViewportId != 0 && settings->ViewportId != ImGui::IMGUI_VIEWPORT_DEFAULT_ID)
+            {
+                buf->appendf("ViewportPos=%d,%d\n", settings->ViewportPos.x, settings->ViewportPos.y);
+                buf->appendf("ViewportId=0x%08X\n", settings->ViewportId);
+            }
+            if (settings->Pos.x != 0 || settings->Pos.y != 0 || settings->ViewportId == ImGui::IMGUI_VIEWPORT_DEFAULT_ID)
+                buf->appendf("Pos=%d,%d\n", settings->Pos.x, settings->Pos.y);
+            if (settings->Size.x != 0 || settings->Size.y != 0)
+                buf->appendf("Size=%d,%d\n", settings->Size.x, settings->Size.y);
+            buf->appendf("Collapsed=%d\n", settings->Collapsed);
+            if (settings->DockId != 0)
+            {
+                //buf->appendf("TabId=0x%08X\n", ImHashStr("#TAB", 4, settings->ID)); // window->TabId: this is not read back but writing it makes "debugging" the .ini data easier.
+                if (settings->DockOrder == -1)
+                    buf->appendf("DockId=0x%08X\n", settings->DockId);
+                else
+                    buf->appendf("DockId=0x%08X,%d\n", settings->DockId, settings->DockOrder);
+                if (settings->ClassId != 0)
+                    buf->appendf("ClassId=0x%08X\n", settings->ClassId);
+            }
         }
         buf->append("\n");
     }
@@ -14017,9 +14747,28 @@
 // [SECTION] VIEWPORTS, PLATFORM WINDOWS
 //-----------------------------------------------------------------------------
 // - GetMainViewport()
+// - FindViewportByID()
+// - FindViewportByPlatformHandle()
+// - SetCurrentViewport() [Internal]
 // - SetWindowViewport() [Internal]
+// - GetWindowAlwaysWantOwnViewport() [Internal]
+// - UpdateTryMergeWindowIntoHostViewport() [Internal]
+// - UpdateTryMergeWindowIntoHostViewports() [Internal]
+// - TranslateWindowsInViewport() [Internal]
+// - ScaleWindowsInViewport() [Internal]
+// - FindHoveredViewportFromPlatformWindowStack() [Internal]
 // - UpdateViewportsNewFrame() [Internal]
-// (this section is more complete in the 'docking' branch)
+// - UpdateViewportsEndFrame() [Internal]
+// - AddUpdateViewport() [Internal]
+// - WindowSelectViewport() [Internal]
+// - WindowSyncOwnedViewport() [Internal]
+// - UpdatePlatformWindows()
+// - RenderPlatformWindowsDefault()
+// - FindPlatformMonitorForPos() [Internal]
+// - FindPlatformMonitorForRect() [Internal]
+// - UpdateViewportPlatformMonitor() [Internal]
+// - DestroyPlatformWindow() [Internal]
+// - DestroyPlatformWindows()
 //-----------------------------------------------------------------------------
 
 ImGuiViewport* ImGui::GetMainViewport()
@@ -14028,39 +14777,4910 @@
     return g.Viewports[0];
 }
 
+// FIXME: This leaks access to viewports not listed in PlatformIO.Viewports[]. Problematic? (#4236)
+ImGuiViewport* ImGui::FindViewportByID(ImGuiID id)
+{
+    ImGuiContext& g = *GImGui;
+    for (ImGuiViewportP* viewport : g.Viewports)
+        if (viewport->ID == id)
+            return viewport;
+    return NULL;
+}
+
+ImGuiViewport* ImGui::FindViewportByPlatformHandle(void* platform_handle)
+{
+    ImGuiContext& g = *GImGui;
+    for (ImGuiViewportP* viewport : g.Viewports)
+        if (viewport->PlatformHandle == platform_handle)
+            return viewport;
+    return NULL;
+}
+
+void ImGui::SetCurrentViewport(ImGuiWindow* current_window, ImGuiViewportP* viewport)
+{
+    ImGuiContext& g = *GImGui;
+    (void)current_window;
+
+    if (viewport)
+        viewport->LastFrameActive = g.FrameCount;
+    if (g.CurrentViewport == viewport)
+        return;
+    g.CurrentDpiScale = viewport ? viewport->DpiScale : 1.0f;
+    g.CurrentViewport = viewport;
+    //IMGUI_DEBUG_LOG_VIEWPORT("[viewport] SetCurrentViewport changed '%s' 0x%08X\n", current_window ? current_window->Name : NULL, viewport ? viewport->ID : 0);
+
+    // Notify platform layer of viewport changes
+    // FIXME-DPI: This is only currently used for experimenting with handling of multiple DPI
+    if (g.CurrentViewport && g.PlatformIO.Platform_OnChangedViewport)
+        g.PlatformIO.Platform_OnChangedViewport(g.CurrentViewport);
+}
+
 void ImGui::SetWindowViewport(ImGuiWindow* window, ImGuiViewportP* viewport)
 {
+    // Abandon viewport
+    if (window->ViewportOwned && window->Viewport->Window == window)
+        window->Viewport->Size = ImVec2(0.0f, 0.0f);
+
     window->Viewport = viewport;
+    window->ViewportId = viewport->ID;
+    window->ViewportOwned = (viewport->Window == window);
+}
+
+static bool ImGui::GetWindowAlwaysWantOwnViewport(ImGuiWindow* window)
+{
+    // Tooltips and menus are not automatically forced into their own viewport when the NoMerge flag is set, however the multiplication of viewports makes them more likely to protrude and create their own.
+    ImGuiContext& g = *GImGui;
+    if (g.IO.ConfigViewportsNoAutoMerge || (window->WindowClass.ViewportFlagsOverrideSet & ImGuiViewportFlags_NoAutoMerge))
+        if (g.ConfigFlagsCurrFrame & ImGuiConfigFlags_ViewportsEnable)
+            if (!window->DockIsActive)
+                if ((window->Flags & (ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_ChildMenu | ImGuiWindowFlags_Tooltip)) == 0)
+                    if ((window->Flags & ImGuiWindowFlags_Popup) == 0 || (window->Flags & ImGuiWindowFlags_Modal) != 0)
+                        return true;
+    return false;
+}
+
+static bool ImGui::UpdateTryMergeWindowIntoHostViewport(ImGuiWindow* window, ImGuiViewportP* viewport)
+{
+    ImGuiContext& g = *GImGui;
+    if (window->Viewport == viewport)
+        return false;
+    if ((viewport->Flags & ImGuiViewportFlags_CanHostOtherWindows) == 0)
+        return false;
+    if ((viewport->Flags & ImGuiViewportFlags_IsMinimized) != 0)
+        return false;
+    if (!viewport->GetMainRect().Contains(window->Rect()))
+        return false;
+    if (GetWindowAlwaysWantOwnViewport(window))
+        return false;
+
+    // FIXME: Can't use g.WindowsFocusOrder[] for root windows only as we care about Z order. If we maintained a DisplayOrder along with FocusOrder we could..
+    for (ImGuiWindow* window_behind : g.Windows)
+    {
+        if (window_behind == window)
+            break;
+        if (window_behind->WasActive && window_behind->ViewportOwned && !(window_behind->Flags & ImGuiWindowFlags_ChildWindow))
+            if (window_behind->Viewport->GetMainRect().Overlaps(window->Rect()))
+                return false;
+    }
+
+    // Move to the existing viewport, Move child/hosted windows as well (FIXME-OPT: iterate child)
+    ImGuiViewportP* old_viewport = window->Viewport;
+    if (window->ViewportOwned)
+        for (int n = 0; n < g.Windows.Size; n++)
+            if (g.Windows[n]->Viewport == old_viewport)
+                SetWindowViewport(g.Windows[n], viewport);
+    SetWindowViewport(window, viewport);
+    BringWindowToDisplayFront(window);
+
+    return true;
+}
+
+// FIXME: handle 0 to N host viewports
+static bool ImGui::UpdateTryMergeWindowIntoHostViewports(ImGuiWindow* window)
+{
+    ImGuiContext& g = *GImGui;
+    return UpdateTryMergeWindowIntoHostViewport(window, g.Viewports[0]);
+}
+
+// Translate Dear ImGui windows when a Host Viewport has been moved
+// (This additionally keeps windows at the same place when ImGuiConfigFlags_ViewportsEnable is toggled!)
+void ImGui::TranslateWindowsInViewport(ImGuiViewportP* viewport, const ImVec2& old_pos, const ImVec2& new_pos)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(viewport->Window == NULL && (viewport->Flags & ImGuiViewportFlags_CanHostOtherWindows));
+
+    // 1) We test if ImGuiConfigFlags_ViewportsEnable was just toggled, which allows us to conveniently
+    // translate imgui windows from OS-window-local to absolute coordinates or vice-versa.
+    // 2) If it's not going to fit into the new size, keep it at same absolute position.
+    // One problem with this is that most Win32 applications doesn't update their render while dragging,
+    // and so the window will appear to teleport when releasing the mouse.
+    const bool translate_all_windows = (g.ConfigFlagsCurrFrame & ImGuiConfigFlags_ViewportsEnable) != (g.ConfigFlagsLastFrame & ImGuiConfigFlags_ViewportsEnable);
+    ImRect test_still_fit_rect(old_pos, old_pos + viewport->Size);
+    ImVec2 delta_pos = new_pos - old_pos;
+    for (ImGuiWindow* window : g.Windows) // FIXME-OPT
+        if (translate_all_windows || (window->Viewport == viewport && test_still_fit_rect.Contains(window->Rect())))
+            TranslateWindow(window, delta_pos);
+}
+
+// Scale all windows (position, size). Use when e.g. changing DPI. (This is a lossy operation!)
+void ImGui::ScaleWindowsInViewport(ImGuiViewportP* viewport, float scale)
+{
+    ImGuiContext& g = *GImGui;
+    if (viewport->Window)
+    {
+        ScaleWindow(viewport->Window, scale);
+    }
+    else
+    {
+        for (ImGuiWindow* window : g.Windows)
+            if (window->Viewport == viewport)
+                ScaleWindow(window, scale);
+    }
+}
+
+// If the backend doesn't set MouseLastHoveredViewport or doesn't honor ImGuiViewportFlags_NoInputs, we do a search ourselves.
+// A) It won't take account of the possibility that non-imgui windows may be in-between our dragged window and our target window.
+// B) It requires Platform_GetWindowFocus to be implemented by backend.
+ImGuiViewportP* ImGui::FindHoveredViewportFromPlatformWindowStack(const ImVec2& mouse_platform_pos)
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiViewportP* best_candidate = NULL;
+    for (ImGuiViewportP* viewport : g.Viewports)
+        if (!(viewport->Flags & (ImGuiViewportFlags_NoInputs | ImGuiViewportFlags_IsMinimized)) && viewport->GetMainRect().Contains(mouse_platform_pos))
+            if (best_candidate == NULL || best_candidate->LastFocusedStampCount < viewport->LastFocusedStampCount)
+                best_candidate = viewport;
+    return best_candidate;
 }
 
 // Update viewports and monitor infos
+// Note that this is running even if 'ImGuiConfigFlags_ViewportsEnable' is not set, in order to clear unused viewports (if any) and update monitor info.
 static void ImGui::UpdateViewportsNewFrame()
 {
     ImGuiContext& g = *GImGui;
-    IM_ASSERT(g.Viewports.Size == 1);
+    IM_ASSERT(g.PlatformIO.Viewports.Size <= g.Viewports.Size);
 
-    // Update main viewport with current platform position.
+    // Update Minimized status (we need it first in order to decide if we'll apply Pos/Size of the main viewport)
+    // Update Focused status
+    const bool viewports_enabled = (g.ConfigFlagsCurrFrame & ImGuiConfigFlags_ViewportsEnable) != 0;
+    if (viewports_enabled)
+    {
+        ImGuiViewportP* focused_viewport = NULL;
+        for (ImGuiViewportP* viewport : g.Viewports)
+        {
+            const bool platform_funcs_available = viewport->PlatformWindowCreated;
+            if (g.PlatformIO.Platform_GetWindowMinimized && platform_funcs_available)
+            {
+                bool is_minimized = g.PlatformIO.Platform_GetWindowMinimized(viewport);
+                if (is_minimized)
+                    viewport->Flags |= ImGuiViewportFlags_IsMinimized;
+                else
+                    viewport->Flags &= ~ImGuiViewportFlags_IsMinimized;
+            }
+
+            // Update our implicit z-order knowledge of platform windows, which is used when the backend cannot provide io.MouseHoveredViewport.
+            // When setting Platform_GetWindowFocus, it is expected that the platform backend can handle calls without crashing if it doesn't have data stored.
+            if (g.PlatformIO.Platform_GetWindowFocus && platform_funcs_available)
+            {
+                bool is_focused = g.PlatformIO.Platform_GetWindowFocus(viewport);
+                if (is_focused)
+                    viewport->Flags |= ImGuiViewportFlags_IsFocused;
+                else
+                    viewport->Flags &= ~ImGuiViewportFlags_IsFocused;
+                if (is_focused)
+                    focused_viewport = viewport;
+            }
+        }
+
+        // Focused viewport has changed?
+        if (focused_viewport && g.PlatformLastFocusedViewportId != focused_viewport->ID)
+        {
+            IMGUI_DEBUG_LOG_VIEWPORT("[viewport] Focused viewport changed %08X -> %08X, attempting to apply our focus.\n", g.PlatformLastFocusedViewportId, focused_viewport->ID);
+            const ImGuiViewport* prev_focused_viewport = FindViewportByID(g.PlatformLastFocusedViewportId);
+            const bool prev_focused_has_been_destroyed = (prev_focused_viewport == NULL) || (prev_focused_viewport->PlatformWindowCreated == false);
+
+            // Store a tag so we can infer z-order easily from all our windows
+            // We compare PlatformLastFocusedViewportId so newly created viewports with _NoFocusOnAppearing flag
+            // will keep the front most stamp instead of losing it back to their parent viewport.
+            if (focused_viewport->LastFocusedStampCount != g.ViewportFocusedStampCount)
+                focused_viewport->LastFocusedStampCount = ++g.ViewportFocusedStampCount;
+            g.PlatformLastFocusedViewportId = focused_viewport->ID;
+
+            // Focus associated dear imgui window
+            // - if focus didn't happen with a click within imgui boundaries, e.g. Clicking platform title bar. (#6299)
+            // - if focus didn't happen because we destroyed another window (#6462)
+            // FIXME: perhaps 'FocusTopMostWindowUnderOne()' can handle the 'focused_window->Window != NULL' case as well.
+            const bool apply_imgui_focus_on_focused_viewport = !IsAnyMouseDown() && !prev_focused_has_been_destroyed;
+            if (apply_imgui_focus_on_focused_viewport)
+            {
+                focused_viewport->LastFocusedHadNavWindow |= (g.NavWindow != NULL) && (g.NavWindow->Viewport == focused_viewport); // Update so a window changing viewport won't lose focus.
+                ImGuiFocusRequestFlags focus_request_flags = ImGuiFocusRequestFlags_UnlessBelowModal | ImGuiFocusRequestFlags_RestoreFocusedChild;
+                if (focused_viewport->Window != NULL)
+                    FocusWindow(focused_viewport->Window, focus_request_flags);
+                else if (focused_viewport->LastFocusedHadNavWindow)
+                    FocusTopMostWindowUnderOne(NULL, NULL, focused_viewport, focus_request_flags); // Focus top most in viewport
+                else
+                    FocusWindow(NULL, focus_request_flags); // No window had focus last time viewport was focused
+            }
+        }
+        if (focused_viewport)
+            focused_viewport->LastFocusedHadNavWindow = (g.NavWindow != NULL) && (g.NavWindow->Viewport == focused_viewport);
+    }
+
+    // Create/update main viewport with current platform position.
     // FIXME-VIEWPORT: Size is driven by backend/user code for backward-compatibility but we should aim to make this more consistent.
     ImGuiViewportP* main_viewport = g.Viewports[0];
-    main_viewport->Flags = ImGuiViewportFlags_IsPlatformWindow | ImGuiViewportFlags_OwnedByApp;
-    main_viewport->Pos = ImVec2(0.0f, 0.0f);
-    main_viewport->Size = g.IO.DisplaySize;
-
-    for (ImGuiViewportP* viewport : g.Viewports)
+    IM_ASSERT(main_viewport->ID == IMGUI_VIEWPORT_DEFAULT_ID);
+    IM_ASSERT(main_viewport->Window == NULL);
+    ImVec2 main_viewport_pos = viewports_enabled ? g.PlatformIO.Platform_GetWindowPos(main_viewport) : ImVec2(0.0f, 0.0f);
+    ImVec2 main_viewport_size = g.IO.DisplaySize;
+    if (viewports_enabled && (main_viewport->Flags & ImGuiViewportFlags_IsMinimized))
     {
-        // Lock down space taken by menu bars and status bars, reset the offset for fucntions like BeginMainMenuBar() to alter them again.
+        main_viewport_pos = main_viewport->Pos;    // Preserve last pos/size when minimized (FIXME: We don't do the same for Size outside of the viewport path)
+        main_viewport_size = main_viewport->Size;
+    }
+    AddUpdateViewport(NULL, IMGUI_VIEWPORT_DEFAULT_ID, main_viewport_pos, main_viewport_size, ImGuiViewportFlags_OwnedByApp | ImGuiViewportFlags_CanHostOtherWindows);
+
+    g.CurrentDpiScale = 0.0f;
+    g.CurrentViewport = NULL;
+    g.MouseViewport = NULL;
+    for (int n = 0; n < g.Viewports.Size; n++)
+    {
+        ImGuiViewportP* viewport = g.Viewports[n];
+        viewport->Idx = n;
+
+        // Erase unused viewports
+        if (n > 0 && viewport->LastFrameActive < g.FrameCount - 2)
+        {
+            DestroyViewport(viewport);
+            n--;
+            continue;
+        }
+
+        const bool platform_funcs_available = viewport->PlatformWindowCreated;
+        if (viewports_enabled)
+        {
+            // Update Position and Size (from Platform Window to ImGui) if requested.
+            // We do it early in the frame instead of waiting for UpdatePlatformWindows() to avoid a frame of lag when moving/resizing using OS facilities.
+            if (!(viewport->Flags & ImGuiViewportFlags_IsMinimized) && platform_funcs_available)
+            {
+                // Viewport->WorkPos and WorkSize will be updated below
+                if (viewport->PlatformRequestMove)
+                    viewport->Pos = viewport->LastPlatformPos = g.PlatformIO.Platform_GetWindowPos(viewport);
+                if (viewport->PlatformRequestResize)
+                    viewport->Size = viewport->LastPlatformSize = g.PlatformIO.Platform_GetWindowSize(viewport);
+            }
+        }
+
+        // Update/copy monitor info
+        UpdateViewportPlatformMonitor(viewport);
+
+        // Lock down space taken by menu bars and status bars, reset the offset for functions like BeginMainMenuBar() to alter them again.
         viewport->WorkOffsetMin = viewport->BuildWorkOffsetMin;
         viewport->WorkOffsetMax = viewport->BuildWorkOffsetMax;
         viewport->BuildWorkOffsetMin = viewport->BuildWorkOffsetMax = ImVec2(0.0f, 0.0f);
         viewport->UpdateWorkRect();
+
+        // Reset alpha every frame. Users of transparency (docking) needs to request a lower alpha back.
+        viewport->Alpha = 1.0f;
+
+        // Translate Dear ImGui windows when a Host Viewport has been moved
+        // (This additionally keeps windows at the same place when ImGuiConfigFlags_ViewportsEnable is toggled!)
+        const ImVec2 viewport_delta_pos = viewport->Pos - viewport->LastPos;
+        if ((viewport->Flags & ImGuiViewportFlags_CanHostOtherWindows) && (viewport_delta_pos.x != 0.0f || viewport_delta_pos.y != 0.0f))
+            TranslateWindowsInViewport(viewport, viewport->LastPos, viewport->Pos);
+
+        // Update DPI scale
+        float new_dpi_scale;
+        if (g.PlatformIO.Platform_GetWindowDpiScale && platform_funcs_available)
+            new_dpi_scale = g.PlatformIO.Platform_GetWindowDpiScale(viewport);
+        else if (viewport->PlatformMonitor != -1)
+            new_dpi_scale = g.PlatformIO.Monitors[viewport->PlatformMonitor].DpiScale;
+        else
+            new_dpi_scale = (viewport->DpiScale != 0.0f) ? viewport->DpiScale : 1.0f;
+        if (viewport->DpiScale != 0.0f && new_dpi_scale != viewport->DpiScale)
+        {
+            float scale_factor = new_dpi_scale / viewport->DpiScale;
+            if (g.IO.ConfigFlags & ImGuiConfigFlags_DpiEnableScaleViewports)
+                ScaleWindowsInViewport(viewport, scale_factor);
+            //if (viewport == GetMainViewport())
+            //    g.PlatformInterface.SetWindowSize(viewport, viewport->Size * scale_factor);
+
+            // Scale our window moving pivot so that the window will rescale roughly around the mouse position.
+            // FIXME-VIEWPORT: This currently creates a resizing feedback loop when a window is straddling a DPI transition border.
+            // (Minor: since our sizes do not perfectly linearly scale, deferring the click offset scale until we know the actual window scale ratio may get us slightly more precise mouse positioning.)
+            //if (g.MovingWindow != NULL && g.MovingWindow->Viewport == viewport)
+            //    g.ActiveIdClickOffset = ImTrunc(g.ActiveIdClickOffset * scale_factor);
+        }
+        viewport->DpiScale = new_dpi_scale;
+    }
+
+    // Update fallback monitor
+    g.PlatformMonitorsFullWorkRect = ImRect(+FLT_MAX, +FLT_MAX, -FLT_MAX, -FLT_MAX);
+    if (g.PlatformIO.Monitors.Size == 0)
+    {
+        ImGuiPlatformMonitor* monitor = &g.FallbackMonitor;
+        monitor->MainPos = main_viewport->Pos;
+        monitor->MainSize = main_viewport->Size;
+        monitor->WorkPos = main_viewport->WorkPos;
+        monitor->WorkSize = main_viewport->WorkSize;
+        monitor->DpiScale = main_viewport->DpiScale;
+        g.PlatformMonitorsFullWorkRect.Add(monitor->WorkPos);
+        g.PlatformMonitorsFullWorkRect.Add(monitor->WorkPos + monitor->WorkSize);
+    }
+    for (ImGuiPlatformMonitor& monitor : g.PlatformIO.Monitors)
+    {
+        g.PlatformMonitorsFullWorkRect.Add(monitor.WorkPos);
+        g.PlatformMonitorsFullWorkRect.Add(monitor.WorkPos + monitor.WorkSize);
+    }
+
+    if (!viewports_enabled)
+    {
+        g.MouseViewport = main_viewport;
+        return;
+    }
+
+    // Mouse handling: decide on the actual mouse viewport for this frame between the active/focused viewport and the hovered viewport.
+    // Note that 'viewport_hovered' should skip over any viewport that has the ImGuiViewportFlags_NoInputs flags set.
+    ImGuiViewportP* viewport_hovered = NULL;
+    if (g.IO.BackendFlags & ImGuiBackendFlags_HasMouseHoveredViewport)
+    {
+        viewport_hovered = g.IO.MouseHoveredViewport ? (ImGuiViewportP*)FindViewportByID(g.IO.MouseHoveredViewport) : NULL;
+        if (viewport_hovered && (viewport_hovered->Flags & ImGuiViewportFlags_NoInputs))
+            viewport_hovered = FindHoveredViewportFromPlatformWindowStack(g.IO.MousePos); // Backend failed to handle _NoInputs viewport: revert to our fallback.
+    }
+    else
+    {
+        // If the backend doesn't know how to honor ImGuiViewportFlags_NoInputs, we do a search ourselves. Note that this search:
+        // A) won't take account of the possibility that non-imgui windows may be in-between our dragged window and our target window.
+        // B) won't take account of how the backend apply parent<>child relationship to secondary viewports, which affects their Z order.
+        // C) uses LastFrameAsRefViewport as a flawed replacement for the last time a window was focused (we could/should fix that by introducing Focus functions in PlatformIO)
+        viewport_hovered = FindHoveredViewportFromPlatformWindowStack(g.IO.MousePos);
+    }
+    if (viewport_hovered != NULL)
+        g.MouseLastHoveredViewport = viewport_hovered;
+    else if (g.MouseLastHoveredViewport == NULL)
+        g.MouseLastHoveredViewport = g.Viewports[0];
+
+    // Update mouse reference viewport
+    // (when moving a window we aim at its viewport, but this will be overwritten below if we go in drag and drop mode)
+    // (MovingViewport->Viewport will be NULL in the rare situation where the window disappared while moving, set UpdateMouseMovingWindowNewFrame() for details)
+    if (g.MovingWindow && g.MovingWindow->Viewport)
+        g.MouseViewport = g.MovingWindow->Viewport;
+    else
+        g.MouseViewport = g.MouseLastHoveredViewport;
+
+    // When dragging something, always refer to the last hovered viewport.
+    // - when releasing a moving window we will revert to aiming behind (at viewport_hovered)
+    // - when we are between viewports, our dragged preview will tend to show in the last viewport _even_ if we don't have tooltips in their viewports (when lacking monitor info)
+    // - consider the case of holding on a menu item to browse child menus: even thou a mouse button is held, there's no active id because menu items only react on mouse release.
+    // FIXME-VIEWPORT: This is essentially broken, when ImGuiBackendFlags_HasMouseHoveredViewport is set we want to trust when viewport_hovered==NULL and use that.
+    const bool is_mouse_dragging_with_an_expected_destination = g.DragDropActive;
+    if (is_mouse_dragging_with_an_expected_destination && viewport_hovered == NULL)
+        viewport_hovered = g.MouseLastHoveredViewport;
+    if (is_mouse_dragging_with_an_expected_destination || g.ActiveId == 0 || !IsAnyMouseDown())
+        if (viewport_hovered != NULL && viewport_hovered != g.MouseViewport && !(viewport_hovered->Flags & ImGuiViewportFlags_NoInputs))
+            g.MouseViewport = viewport_hovered;
+
+    IM_ASSERT(g.MouseViewport != NULL);
+}
+
+// Update user-facing viewport list (g.Viewports -> g.PlatformIO.Viewports after filtering out some)
+static void ImGui::UpdateViewportsEndFrame()
+{
+    ImGuiContext& g = *GImGui;
+    g.PlatformIO.Viewports.resize(0);
+    for (int i = 0; i < g.Viewports.Size; i++)
+    {
+        ImGuiViewportP* viewport = g.Viewports[i];
+        viewport->LastPos = viewport->Pos;
+        if (viewport->LastFrameActive < g.FrameCount || viewport->Size.x <= 0.0f || viewport->Size.y <= 0.0f)
+            if (i > 0) // Always include main viewport in the list
+                continue;
+        if (viewport->Window && !IsWindowActiveAndVisible(viewport->Window))
+            continue;
+        if (i > 0)
+            IM_ASSERT(viewport->Window != NULL);
+        g.PlatformIO.Viewports.push_back(viewport);
+    }
+    g.Viewports[0]->ClearRequestFlags(); // Clear main viewport flags because UpdatePlatformWindows() won't do it and may not even be called
+}
+
+// FIXME: We should ideally refactor the system to call this every frame (we currently don't)
+ImGuiViewportP* ImGui::AddUpdateViewport(ImGuiWindow* window, ImGuiID id, const ImVec2& pos, const ImVec2& size, ImGuiViewportFlags flags)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(id != 0);
+
+    flags |= ImGuiViewportFlags_IsPlatformWindow;
+    if (window != NULL)
+    {
+        if (g.MovingWindow && g.MovingWindow->RootWindowDockTree == window)
+            flags |= ImGuiViewportFlags_NoInputs | ImGuiViewportFlags_NoFocusOnAppearing;
+        if ((window->Flags & ImGuiWindowFlags_NoMouseInputs) && (window->Flags & ImGuiWindowFlags_NoNavInputs))
+            flags |= ImGuiViewportFlags_NoInputs;
+        if (window->Flags & ImGuiWindowFlags_NoFocusOnAppearing)
+            flags |= ImGuiViewportFlags_NoFocusOnAppearing;
+    }
+
+    ImGuiViewportP* viewport = (ImGuiViewportP*)FindViewportByID(id);
+    if (viewport)
+    {
+        // Always update for main viewport as we are already pulling correct platform pos/size (see #4900)
+        if (!viewport->PlatformRequestMove || viewport->ID == IMGUI_VIEWPORT_DEFAULT_ID)
+            viewport->Pos = pos;
+        if (!viewport->PlatformRequestResize || viewport->ID == IMGUI_VIEWPORT_DEFAULT_ID)
+            viewport->Size = size;
+        viewport->Flags = flags | (viewport->Flags & (ImGuiViewportFlags_IsMinimized | ImGuiViewportFlags_IsFocused)); // Preserve existing flags
+    }
+    else
+    {
+        // New viewport
+        viewport = IM_NEW(ImGuiViewportP)();
+        viewport->ID = id;
+        viewport->Idx = g.Viewports.Size;
+        viewport->Pos = viewport->LastPos = pos;
+        viewport->Size = size;
+        viewport->Flags = flags;
+        UpdateViewportPlatformMonitor(viewport);
+        g.Viewports.push_back(viewport);
+        g.ViewportCreatedCount++;
+        IMGUI_DEBUG_LOG_VIEWPORT("[viewport] Add Viewport %08X '%s'\n", id, window ? window->Name : "<NULL>");
+
+        // We normally setup for all viewports in NewFrame() but here need to handle the mid-frame creation of a new viewport.
+        // We need to extend the fullscreen clip rect so the OverlayDrawList clip is correct for that the first frame
+        g.DrawListSharedData.ClipRectFullscreen.x = ImMin(g.DrawListSharedData.ClipRectFullscreen.x, viewport->Pos.x);
+        g.DrawListSharedData.ClipRectFullscreen.y = ImMin(g.DrawListSharedData.ClipRectFullscreen.y, viewport->Pos.y);
+        g.DrawListSharedData.ClipRectFullscreen.z = ImMax(g.DrawListSharedData.ClipRectFullscreen.z, viewport->Pos.x + viewport->Size.x);
+        g.DrawListSharedData.ClipRectFullscreen.w = ImMax(g.DrawListSharedData.ClipRectFullscreen.w, viewport->Pos.y + viewport->Size.y);
+
+        // Store initial DpiScale before the OS platform window creation, based on expected monitor data.
+        // This is so we can select an appropriate font size on the first frame of our window lifetime
+        if (viewport->PlatformMonitor != -1)
+            viewport->DpiScale = g.PlatformIO.Monitors[viewport->PlatformMonitor].DpiScale;
+    }
+
+    viewport->Window = window;
+    viewport->LastFrameActive = g.FrameCount;
+    viewport->UpdateWorkRect();
+    IM_ASSERT(window == NULL || viewport->ID == window->ID);
+
+    if (window != NULL)
+        window->ViewportOwned = true;
+
+    return viewport;
+}
+
+static void ImGui::DestroyViewport(ImGuiViewportP* viewport)
+{
+    // Clear references to this viewport in windows (window->ViewportId becomes the master data)
+    ImGuiContext& g = *GImGui;
+    for (ImGuiWindow* window : g.Windows)
+    {
+        if (window->Viewport != viewport)
+            continue;
+        window->Viewport = NULL;
+        window->ViewportOwned = false;
+    }
+    if (viewport == g.MouseLastHoveredViewport)
+        g.MouseLastHoveredViewport = NULL;
+
+    // Destroy
+    IMGUI_DEBUG_LOG_VIEWPORT("[viewport] Delete Viewport %08X '%s'\n", viewport->ID, viewport->Window ? viewport->Window->Name : "n/a");
+    DestroyPlatformWindow(viewport); // In most circumstances the platform window will already be destroyed here.
+    IM_ASSERT(g.PlatformIO.Viewports.contains(viewport) == false);
+    IM_ASSERT(g.Viewports[viewport->Idx] == viewport);
+    g.Viewports.erase(g.Viewports.Data + viewport->Idx);
+    IM_DELETE(viewport);
+}
+
+// FIXME-VIEWPORT: This is all super messy and ought to be clarified or rewritten.
+static void ImGui::WindowSelectViewport(ImGuiWindow* window)
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiWindowFlags flags = window->Flags;
+    window->ViewportAllowPlatformMonitorExtend = -1;
+
+    // Restore main viewport if multi-viewport is not supported by the backend
+    ImGuiViewportP* main_viewport = (ImGuiViewportP*)(void*)GetMainViewport();
+    if (!(g.ConfigFlagsCurrFrame & ImGuiConfigFlags_ViewportsEnable))
+    {
+        SetWindowViewport(window, main_viewport);
+        return;
+    }
+    window->ViewportOwned = false;
+
+    // Appearing popups reset their viewport so they can inherit again
+    if ((flags & (ImGuiWindowFlags_Popup | ImGuiWindowFlags_Tooltip)) && window->Appearing)
+    {
+        window->Viewport = NULL;
+        window->ViewportId = 0;
+    }
+
+    if ((g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasViewport) == 0)
+    {
+        // By default inherit from parent window
+        if (window->Viewport == NULL && window->ParentWindow && (!window->ParentWindow->IsFallbackWindow || window->ParentWindow->WasActive))
+            window->Viewport = window->ParentWindow->Viewport;
+
+        // Attempt to restore saved viewport id (= window that hasn't been activated yet), try to restore the viewport based on saved 'window->ViewportPos' restored from .ini file
+        if (window->Viewport == NULL && window->ViewportId != 0)
+        {
+            window->Viewport = (ImGuiViewportP*)FindViewportByID(window->ViewportId);
+            if (window->Viewport == NULL && window->ViewportPos.x != FLT_MAX && window->ViewportPos.y != FLT_MAX)
+                window->Viewport = AddUpdateViewport(window, window->ID, window->ViewportPos, window->Size, ImGuiViewportFlags_None);
+        }
+    }
+
+    bool lock_viewport = false;
+    if (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasViewport)
+    {
+        // Code explicitly request a viewport
+        window->Viewport = (ImGuiViewportP*)FindViewportByID(g.NextWindowData.ViewportId);
+        window->ViewportId = g.NextWindowData.ViewportId; // Store ID even if Viewport isn't resolved yet.
+        if (window->Viewport && (window->Flags & ImGuiWindowFlags_DockNodeHost) != 0 && window->Viewport->Window != NULL)
+        {
+            window->Viewport->Window = window;
+            window->Viewport->ID = window->ViewportId = window->ID; // Overwrite ID (always owned by node)
+        }
+        lock_viewport = true;
+    }
+    else if ((flags & ImGuiWindowFlags_ChildWindow) || (flags & ImGuiWindowFlags_ChildMenu))
+    {
+        // Always inherit viewport from parent window
+        if (window->DockNode && window->DockNode->HostWindow)
+            IM_ASSERT(window->DockNode->HostWindow->Viewport == window->ParentWindow->Viewport);
+        window->Viewport = window->ParentWindow->Viewport;
+    }
+    else if (window->DockNode && window->DockNode->HostWindow)
+    {
+        // This covers the "always inherit viewport from parent window" case for when a window reattach to a node that was just created mid-frame
+        window->Viewport = window->DockNode->HostWindow->Viewport;
+    }
+    else if (flags & ImGuiWindowFlags_Tooltip)
+    {
+        window->Viewport = g.MouseViewport;
+    }
+    else if (GetWindowAlwaysWantOwnViewport(window))
+    {
+        window->Viewport = AddUpdateViewport(window, window->ID, window->Pos, window->Size, ImGuiViewportFlags_None);
+    }
+    else if (g.MovingWindow && g.MovingWindow->RootWindowDockTree == window && IsMousePosValid())
+    {
+        if (window->Viewport != NULL && window->Viewport->Window == window)
+            window->Viewport = AddUpdateViewport(window, window->ID, window->Pos, window->Size, ImGuiViewportFlags_None);
+    }
+    else
+    {
+        // Merge into host viewport?
+        // We cannot test window->ViewportOwned as it set lower in the function.
+        // Testing (g.ActiveId == 0 || g.ActiveIdAllowOverlap) to avoid merging during a short-term widget interaction. Main intent was to avoid during resize (see #4212)
+        bool try_to_merge_into_host_viewport = (window->Viewport && window == window->Viewport->Window && (g.ActiveId == 0 || g.ActiveIdAllowOverlap));
+        if (try_to_merge_into_host_viewport)
+            UpdateTryMergeWindowIntoHostViewports(window);
+    }
+
+    // Fallback: merge in default viewport if z-order matches, otherwise create a new viewport
+    if (window->Viewport == NULL)
+        if (!UpdateTryMergeWindowIntoHostViewport(window, main_viewport))
+            window->Viewport = AddUpdateViewport(window, window->ID, window->Pos, window->Size, ImGuiViewportFlags_None);
+
+    // Mark window as allowed to protrude outside of its viewport and into the current monitor
+    if (!lock_viewport)
+    {
+        if (flags & (ImGuiWindowFlags_Tooltip | ImGuiWindowFlags_Popup))
+        {
+            // We need to take account of the possibility that mouse may become invalid.
+            // Popups/Tooltip always set ViewportAllowPlatformMonitorExtend so GetWindowAllowedExtentRect() will return full monitor bounds.
+            ImVec2 mouse_ref = (flags & ImGuiWindowFlags_Tooltip) ? g.IO.MousePos : g.BeginPopupStack.back().OpenMousePos;
+            bool use_mouse_ref = (g.NavDisableHighlight || !g.NavDisableMouseHover || !g.NavWindow);
+            bool mouse_valid = IsMousePosValid(&mouse_ref);
+            if ((window->Appearing || (flags & (ImGuiWindowFlags_Tooltip | ImGuiWindowFlags_ChildMenu))) && (!use_mouse_ref || mouse_valid))
+                window->ViewportAllowPlatformMonitorExtend = FindPlatformMonitorForPos((use_mouse_ref && mouse_valid) ? mouse_ref : NavCalcPreferredRefPos());
+            else
+                window->ViewportAllowPlatformMonitorExtend = window->Viewport->PlatformMonitor;
+        }
+        else if (window->Viewport && window != window->Viewport->Window && window->Viewport->Window && !(flags & ImGuiWindowFlags_ChildWindow) && window->DockNode == NULL)
+        {
+            // When called from Begin() we don't have access to a proper version of the Hidden flag yet, so we replicate this code.
+            const bool will_be_visible = (window->DockIsActive && !window->DockTabIsVisible) ? false : true;
+            if ((window->Flags & ImGuiWindowFlags_DockNodeHost) && window->Viewport->LastFrameActive < g.FrameCount && will_be_visible)
+            {
+                // Steal/transfer ownership
+                IMGUI_DEBUG_LOG_VIEWPORT("[viewport] Window '%s' steal Viewport %08X from Window '%s'\n", window->Name, window->Viewport->ID, window->Viewport->Window->Name);
+                window->Viewport->Window = window;
+                window->Viewport->ID = window->ID;
+                window->Viewport->LastNameHash = 0;
+            }
+            else if (!UpdateTryMergeWindowIntoHostViewports(window)) // Merge?
+            {
+                // New viewport
+                window->Viewport = AddUpdateViewport(window, window->ID, window->Pos, window->Size, ImGuiViewportFlags_NoFocusOnAppearing);
+            }
+        }
+        else if (window->ViewportAllowPlatformMonitorExtend < 0 && (flags & ImGuiWindowFlags_ChildWindow) == 0)
+        {
+            // Regular (non-child, non-popup) windows by default are also allowed to protrude
+            // Child windows are kept contained within their parent.
+            window->ViewportAllowPlatformMonitorExtend = window->Viewport->PlatformMonitor;
+        }
+    }
+
+    // Update flags
+    window->ViewportOwned = (window == window->Viewport->Window);
+    window->ViewportId = window->Viewport->ID;
+
+    // If the OS window has a title bar, hide our imgui title bar
+    //if (window->ViewportOwned && !(window->Viewport->Flags & ImGuiViewportFlags_NoDecoration))
+    //    window->Flags |= ImGuiWindowFlags_NoTitleBar;
+}
+
+void ImGui::WindowSyncOwnedViewport(ImGuiWindow* window, ImGuiWindow* parent_window_in_stack)
+{
+    ImGuiContext& g = *GImGui;
+
+    bool viewport_rect_changed = false;
+
+    // Synchronize window --> viewport in most situations
+    // Synchronize viewport -> window in case the platform window has been moved or resized from the OS/WM
+    if (window->Viewport->PlatformRequestMove)
+    {
+        window->Pos = window->Viewport->Pos;
+        MarkIniSettingsDirty(window);
+    }
+    else if (memcmp(&window->Viewport->Pos, &window->Pos, sizeof(window->Pos)) != 0)
+    {
+        viewport_rect_changed = true;
+        window->Viewport->Pos = window->Pos;
+    }
+
+    if (window->Viewport->PlatformRequestResize)
+    {
+        window->Size = window->SizeFull = window->Viewport->Size;
+        MarkIniSettingsDirty(window);
+    }
+    else if (memcmp(&window->Viewport->Size, &window->Size, sizeof(window->Size)) != 0)
+    {
+        viewport_rect_changed = true;
+        window->Viewport->Size = window->Size;
+    }
+    window->Viewport->UpdateWorkRect();
+
+    // The viewport may have changed monitor since the global update in UpdateViewportsNewFrame()
+    // Either a SetNextWindowPos() call in the current frame or a SetWindowPos() call in the previous frame may have this effect.
+    if (viewport_rect_changed)
+        UpdateViewportPlatformMonitor(window->Viewport);
+
+    // Update common viewport flags
+    const ImGuiViewportFlags viewport_flags_to_clear = ImGuiViewportFlags_TopMost | ImGuiViewportFlags_NoTaskBarIcon | ImGuiViewportFlags_NoDecoration | ImGuiViewportFlags_NoRendererClear;
+    ImGuiViewportFlags viewport_flags = window->Viewport->Flags & ~viewport_flags_to_clear;
+    ImGuiWindowFlags window_flags = window->Flags;
+    const bool is_modal = (window_flags & ImGuiWindowFlags_Modal) != 0;
+    const bool is_short_lived_floating_window = (window_flags & (ImGuiWindowFlags_ChildMenu | ImGuiWindowFlags_Tooltip | ImGuiWindowFlags_Popup)) != 0;
+    if (window_flags & ImGuiWindowFlags_Tooltip)
+        viewport_flags |= ImGuiViewportFlags_TopMost;
+    if ((g.IO.ConfigViewportsNoTaskBarIcon || is_short_lived_floating_window) && !is_modal)
+        viewport_flags |= ImGuiViewportFlags_NoTaskBarIcon;
+    if (g.IO.ConfigViewportsNoDecoration || is_short_lived_floating_window)
+        viewport_flags |= ImGuiViewportFlags_NoDecoration;
+
+    // Not correct to set modal as topmost because:
+    // - Because other popups can be stacked above a modal (e.g. combo box in a modal)
+    // - ImGuiViewportFlags_TopMost is currently handled different in backends: in Win32 it is "appear top most" whereas in GLFW and SDL it is "stay topmost"
+    //if (flags & ImGuiWindowFlags_Modal)
+    //    viewport_flags |= ImGuiViewportFlags_TopMost;
+
+    // For popups and menus that may be protruding out of their parent viewport, we enable _NoFocusOnClick so that clicking on them
+    // won't steal the OS focus away from their parent window (which may be reflected in OS the title bar decoration).
+    // Setting _NoFocusOnClick would technically prevent us from bringing back to front in case they are being covered by an OS window from a different app,
+    // but it shouldn't be much of a problem considering those are already popups that are closed when clicking elsewhere.
+    if (is_short_lived_floating_window && !is_modal)
+        viewport_flags |= ImGuiViewportFlags_NoFocusOnAppearing | ImGuiViewportFlags_NoFocusOnClick;
+
+    // We can overwrite viewport flags using ImGuiWindowClass (advanced users)
+    if (window->WindowClass.ViewportFlagsOverrideSet)
+        viewport_flags |= window->WindowClass.ViewportFlagsOverrideSet;
+    if (window->WindowClass.ViewportFlagsOverrideClear)
+        viewport_flags &= ~window->WindowClass.ViewportFlagsOverrideClear;
+
+    // We can also tell the backend that clearing the platform window won't be necessary,
+    // as our window background is filling the viewport and we have disabled BgAlpha.
+    // FIXME: Work on support for per-viewport transparency (#2766)
+    if (!(window_flags & ImGuiWindowFlags_NoBackground))
+        viewport_flags |= ImGuiViewportFlags_NoRendererClear;
+
+    window->Viewport->Flags = viewport_flags;
+
+    // Update parent viewport ID
+    // (the !IsFallbackWindow test mimic the one done in WindowSelectViewport())
+    if (window->WindowClass.ParentViewportId != (ImGuiID)-1)
+        window->Viewport->ParentViewportId = window->WindowClass.ParentViewportId;
+    else if ((window_flags & (ImGuiWindowFlags_Popup | ImGuiWindowFlags_Tooltip)) && parent_window_in_stack && (!parent_window_in_stack->IsFallbackWindow || parent_window_in_stack->WasActive))
+        window->Viewport->ParentViewportId = parent_window_in_stack->Viewport->ID;
+    else
+        window->Viewport->ParentViewportId = g.IO.ConfigViewportsNoDefaultParent ? 0 : IMGUI_VIEWPORT_DEFAULT_ID;
+}
+
+// Called by user at the end of the main loop, after EndFrame()
+// This will handle the creation/update of all OS windows via function defined in the ImGuiPlatformIO api.
+void ImGui::UpdatePlatformWindows()
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(g.FrameCountEnded == g.FrameCount && "Forgot to call Render() or EndFrame() before UpdatePlatformWindows()?");
+    IM_ASSERT(g.FrameCountPlatformEnded < g.FrameCount);
+    g.FrameCountPlatformEnded = g.FrameCount;
+    if (!(g.ConfigFlagsCurrFrame & ImGuiConfigFlags_ViewportsEnable))
+        return;
+
+    // Create/resize/destroy platform windows to match each active viewport.
+    // Skip the main viewport (index 0), which is always fully handled by the application!
+    for (int i = 1; i < g.Viewports.Size; i++)
+    {
+        ImGuiViewportP* viewport = g.Viewports[i];
+
+        // Destroy platform window if the viewport hasn't been submitted or if it is hosting a hidden window
+        // (the implicit/fallback Debug##Default window will be registering its viewport then be disabled, causing a dummy DestroyPlatformWindow to be made each frame)
+        bool destroy_platform_window = false;
+        destroy_platform_window |= (viewport->LastFrameActive < g.FrameCount - 1);
+        destroy_platform_window |= (viewport->Window && !IsWindowActiveAndVisible(viewport->Window));
+        if (destroy_platform_window)
+        {
+            DestroyPlatformWindow(viewport);
+            continue;
+        }
+
+        // New windows that appears directly in a new viewport won't always have a size on their first frame
+        if (viewport->LastFrameActive < g.FrameCount || viewport->Size.x <= 0 || viewport->Size.y <= 0)
+            continue;
+
+        // Create window
+        const bool is_new_platform_window = (viewport->PlatformWindowCreated == false);
+        if (is_new_platform_window)
+        {
+            IMGUI_DEBUG_LOG_VIEWPORT("[viewport] Create Platform Window %08X '%s'\n", viewport->ID, viewport->Window ? viewport->Window->Name : "n/a");
+            g.PlatformIO.Platform_CreateWindow(viewport);
+            if (g.PlatformIO.Renderer_CreateWindow != NULL)
+                g.PlatformIO.Renderer_CreateWindow(viewport);
+            g.PlatformWindowsCreatedCount++;
+            viewport->LastNameHash = 0;
+            viewport->LastPlatformPos = viewport->LastPlatformSize = ImVec2(FLT_MAX, FLT_MAX); // By clearing those we'll enforce a call to Platform_SetWindowPos/Size below, before Platform_ShowWindow (FIXME: Is that necessary?)
+            viewport->LastRendererSize = viewport->Size;                                       // We don't need to call Renderer_SetWindowSize() as it is expected Renderer_CreateWindow() already did it.
+            viewport->PlatformWindowCreated = true;
+        }
+
+        // Apply Position and Size (from ImGui to Platform/Renderer backends)
+        if ((viewport->LastPlatformPos.x != viewport->Pos.x || viewport->LastPlatformPos.y != viewport->Pos.y) && !viewport->PlatformRequestMove)
+            g.PlatformIO.Platform_SetWindowPos(viewport, viewport->Pos);
+        if ((viewport->LastPlatformSize.x != viewport->Size.x || viewport->LastPlatformSize.y != viewport->Size.y) && !viewport->PlatformRequestResize)
+            g.PlatformIO.Platform_SetWindowSize(viewport, viewport->Size);
+        if ((viewport->LastRendererSize.x != viewport->Size.x || viewport->LastRendererSize.y != viewport->Size.y) && g.PlatformIO.Renderer_SetWindowSize)
+            g.PlatformIO.Renderer_SetWindowSize(viewport, viewport->Size);
+        viewport->LastPlatformPos = viewport->Pos;
+        viewport->LastPlatformSize = viewport->LastRendererSize = viewport->Size;
+
+        // Update title bar (if it changed)
+        if (ImGuiWindow* window_for_title = GetWindowForTitleDisplay(viewport->Window))
+        {
+            const char* title_begin = window_for_title->Name;
+            char* title_end = (char*)(intptr_t)FindRenderedTextEnd(title_begin);
+            const ImGuiID title_hash = ImHashStr(title_begin, title_end - title_begin);
+            if (viewport->LastNameHash != title_hash)
+            {
+                char title_end_backup_c = *title_end;
+                *title_end = 0; // Cut existing buffer short instead of doing an alloc/free, no small gain.
+                g.PlatformIO.Platform_SetWindowTitle(viewport, title_begin);
+                *title_end = title_end_backup_c;
+                viewport->LastNameHash = title_hash;
+            }
+        }
+
+        // Update alpha (if it changed)
+        if (viewport->LastAlpha != viewport->Alpha && g.PlatformIO.Platform_SetWindowAlpha)
+            g.PlatformIO.Platform_SetWindowAlpha(viewport, viewport->Alpha);
+        viewport->LastAlpha = viewport->Alpha;
+
+        // Optional, general purpose call to allow the backend to perform general book-keeping even if things haven't changed.
+        if (g.PlatformIO.Platform_UpdateWindow)
+            g.PlatformIO.Platform_UpdateWindow(viewport);
+
+        if (is_new_platform_window)
+        {
+            // On startup ensure new platform window don't steal focus (give it a few frames, as nested contents may lead to viewport being created a few frames late)
+            if (g.FrameCount < 3)
+                viewport->Flags |= ImGuiViewportFlags_NoFocusOnAppearing;
+
+            // Show window
+            g.PlatformIO.Platform_ShowWindow(viewport);
+
+            // Even without focus, we assume the window becomes front-most.
+            // This is useful for our platform z-order heuristic when io.MouseHoveredViewport is not available.
+            if (viewport->LastFocusedStampCount != g.ViewportFocusedStampCount)
+                viewport->LastFocusedStampCount = ++g.ViewportFocusedStampCount;
+        }
+
+        // Clear request flags
+        viewport->ClearRequestFlags();
     }
 }
 
+// This is a default/basic function for performing the rendering/swap of multiple Platform Windows.
+// Custom renderers may prefer to not call this function at all, and instead iterate the publicly exposed platform data and handle rendering/sync themselves.
+// The Render/Swap functions stored in ImGuiPlatformIO are merely here to allow for this helper to exist, but you can do it yourself:
+//
+//    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+//    for (int i = 1; i < platform_io.Viewports.Size; i++)
+//        if ((platform_io.Viewports[i]->Flags & ImGuiViewportFlags_Minimized) == 0)
+//            MyRenderFunction(platform_io.Viewports[i], my_args);
+//    for (int i = 1; i < platform_io.Viewports.Size; i++)
+//        if ((platform_io.Viewports[i]->Flags & ImGuiViewportFlags_Minimized) == 0)
+//            MySwapBufferFunction(platform_io.Viewports[i], my_args);
+//
+void ImGui::RenderPlatformWindowsDefault(void* platform_render_arg, void* renderer_render_arg)
+{
+    // Skip the main viewport (index 0), which is always fully handled by the application!
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    for (int i = 1; i < platform_io.Viewports.Size; i++)
+    {
+        ImGuiViewport* viewport = platform_io.Viewports[i];
+        if (viewport->Flags & ImGuiViewportFlags_IsMinimized)
+            continue;
+        if (platform_io.Platform_RenderWindow) platform_io.Platform_RenderWindow(viewport, platform_render_arg);
+        if (platform_io.Renderer_RenderWindow) platform_io.Renderer_RenderWindow(viewport, renderer_render_arg);
+    }
+    for (int i = 1; i < platform_io.Viewports.Size; i++)
+    {
+        ImGuiViewport* viewport = platform_io.Viewports[i];
+        if (viewport->Flags & ImGuiViewportFlags_IsMinimized)
+            continue;
+        if (platform_io.Platform_SwapBuffers) platform_io.Platform_SwapBuffers(viewport, platform_render_arg);
+        if (platform_io.Renderer_SwapBuffers) platform_io.Renderer_SwapBuffers(viewport, renderer_render_arg);
+    }
+}
+
+static int ImGui::FindPlatformMonitorForPos(const ImVec2& pos)
+{
+    ImGuiContext& g = *GImGui;
+    for (int monitor_n = 0; monitor_n < g.PlatformIO.Monitors.Size; monitor_n++)
+    {
+        const ImGuiPlatformMonitor& monitor = g.PlatformIO.Monitors[monitor_n];
+        if (ImRect(monitor.MainPos, monitor.MainPos + monitor.MainSize).Contains(pos))
+            return monitor_n;
+    }
+    return -1;
+}
+
+// Search for the monitor with the largest intersection area with the given rectangle
+// We generally try to avoid searching loops but the monitor count should be very small here
+// FIXME-OPT: We could test the last monitor used for that viewport first, and early
+static int ImGui::FindPlatformMonitorForRect(const ImRect& rect)
+{
+    ImGuiContext& g = *GImGui;
+
+    const int monitor_count = g.PlatformIO.Monitors.Size;
+    if (monitor_count <= 1)
+        return monitor_count - 1;
+
+    // Use a minimum threshold of 1.0f so a zero-sized rect won't false positive, and will still find the correct monitor given its position.
+    // This is necessary for tooltips which always resize down to zero at first.
+    const float surface_threshold = ImMax(rect.GetWidth() * rect.GetHeight() * 0.5f, 1.0f);
+    int best_monitor_n = -1;
+    float best_monitor_surface = 0.001f;
+
+    for (int monitor_n = 0; monitor_n < g.PlatformIO.Monitors.Size && best_monitor_surface < surface_threshold; monitor_n++)
+    {
+        const ImGuiPlatformMonitor& monitor = g.PlatformIO.Monitors[monitor_n];
+        const ImRect monitor_rect = ImRect(monitor.MainPos, monitor.MainPos + monitor.MainSize);
+        if (monitor_rect.Contains(rect))
+            return monitor_n;
+        ImRect overlapping_rect = rect;
+        overlapping_rect.ClipWithFull(monitor_rect);
+        float overlapping_surface = overlapping_rect.GetWidth() * overlapping_rect.GetHeight();
+        if (overlapping_surface < best_monitor_surface)
+            continue;
+        best_monitor_surface = overlapping_surface;
+        best_monitor_n = monitor_n;
+    }
+    return best_monitor_n;
+}
+
+// Update monitor from viewport rectangle (we'll use this info to clamp windows and save windows lost in a removed monitor)
+static void ImGui::UpdateViewportPlatformMonitor(ImGuiViewportP* viewport)
+{
+    viewport->PlatformMonitor = (short)FindPlatformMonitorForRect(viewport->GetMainRect());
+}
+
+// Return value is always != NULL, but don't hold on it across frames.
+const ImGuiPlatformMonitor* ImGui::GetViewportPlatformMonitor(ImGuiViewport* viewport_p)
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiViewportP* viewport = (ImGuiViewportP*)(void*)viewport_p;
+    int monitor_idx = viewport->PlatformMonitor;
+    if (monitor_idx >= 0 && monitor_idx < g.PlatformIO.Monitors.Size)
+        return &g.PlatformIO.Monitors[monitor_idx];
+    return &g.FallbackMonitor;
+}
+
+void ImGui::DestroyPlatformWindow(ImGuiViewportP* viewport)
+{
+    ImGuiContext& g = *GImGui;
+    if (viewport->PlatformWindowCreated)
+    {
+        IMGUI_DEBUG_LOG_VIEWPORT("[viewport] Destroy Platform Window %08X '%s'\n", viewport->ID, viewport->Window ? viewport->Window->Name : "n/a");
+        if (g.PlatformIO.Renderer_DestroyWindow)
+            g.PlatformIO.Renderer_DestroyWindow(viewport);
+        if (g.PlatformIO.Platform_DestroyWindow)
+            g.PlatformIO.Platform_DestroyWindow(viewport);
+        IM_ASSERT(viewport->RendererUserData == NULL && viewport->PlatformUserData == NULL);
+
+        // Don't clear PlatformWindowCreated for the main viewport, as we initially set that up to true in Initialize()
+        // The righter way may be to leave it to the backend to set this flag all-together, and made the flag public.
+        if (viewport->ID != IMGUI_VIEWPORT_DEFAULT_ID)
+            viewport->PlatformWindowCreated = false;
+    }
+    else
+    {
+        IM_ASSERT(viewport->RendererUserData == NULL && viewport->PlatformUserData == NULL && viewport->PlatformHandle == NULL);
+    }
+    viewport->RendererUserData = viewport->PlatformUserData = viewport->PlatformHandle = NULL;
+    viewport->ClearRequestFlags();
+}
+
+void ImGui::DestroyPlatformWindows()
+{
+    // We call the destroy window on every viewport (including the main viewport, index 0) to give a chance to the backend
+    // to clear any data they may have stored in e.g. PlatformUserData, RendererUserData.
+    // It is convenient for the platform backend code to store something in the main viewport, in order for e.g. the mouse handling
+    // code to operator a consistent manner.
+    // It is expected that the backend can handle calls to Renderer_DestroyWindow/Platform_DestroyWindow without
+    // crashing if it doesn't have data stored.
+    ImGuiContext& g = *GImGui;
+    for (ImGuiViewportP* viewport : g.Viewports)
+        DestroyPlatformWindow(viewport);
+}
+
+
 //-----------------------------------------------------------------------------
 // [SECTION] DOCKING
 //-----------------------------------------------------------------------------
+// Docking: Internal Types
+// Docking: Forward Declarations
+// Docking: ImGuiDockContext
+// Docking: ImGuiDockContext Docking/Undocking functions
+// Docking: ImGuiDockNode
+// Docking: ImGuiDockNode Tree manipulation functions
+// Docking: Public Functions (SetWindowDock, DockSpace, DockSpaceOverViewport)
+// Docking: Builder Functions
+// Docking: Begin/End Support Functions (called from Begin/End)
+// Docking: Settings
+//-----------------------------------------------------------------------------
 
-// (this section is filled in the 'docking' branch)
+//-----------------------------------------------------------------------------
+// Typical Docking call flow: (root level is generally public API):
+//-----------------------------------------------------------------------------
+// - NewFrame()                               new dear imgui frame
+//    | DockContextNewFrameUpdateUndocking()  - process queued undocking requests
+//    | - DockContextProcessUndockWindow()    - process one window undocking request
+//    | - DockContextProcessUndockNode()      - process one whole node undocking request
+//    | DockContextNewFrameUpdateUndocking()  - process queue docking requests, create floating dock nodes
+//    | - update g.HoveredDockNode            - [debug] update node hovered by mouse
+//    | - DockContextProcessDock()            - process one docking request
+//    | - DockNodeUpdate()
+//    |   - DockNodeUpdateForRootNode()
+//    |     - DockNodeUpdateFlagsAndCollapse()
+//    |     - DockNodeFindInfo()
+//    |   - destroy unused node or tab bar
+//    |   - create dock node host window
+//    |      - Begin() etc.
+//    |   - DockNodeStartMouseMovingWindow()
+//    |   - DockNodeTreeUpdatePosSize()
+//    |   - DockNodeTreeUpdateSplitter()
+//    |   - draw node background
+//    |   - DockNodeUpdateTabBar()            - create/update tab bar for a docking node
+//    |     - DockNodeAddTabBar()
+//    |     - DockNodeWindowMenuUpdate()
+//    |     - DockNodeCalcTabBarLayout()
+//    |     - BeginTabBarEx()
+//    |     - TabItemEx() calls
+//    |     - EndTabBar()
+//    |   - BeginDockableDragDropTarget()
+//    |      - DockNodeUpdate()               - recurse into child nodes...
+//-----------------------------------------------------------------------------
+// - DockSpace()                              user submit a dockspace into a window
+//    | Begin(Child)                          - create a child window
+//    | DockNodeUpdate()                      - call main dock node update function
+//    | End(Child)
+//    | ItemSize()
+//-----------------------------------------------------------------------------
+// - Begin()
+//    | BeginDocked()
+//    | BeginDockableDragDropSource()
+//    | BeginDockableDragDropTarget()
+//    | - DockNodePreviewDockRender()
+//-----------------------------------------------------------------------------
+// - EndFrame()
+//    | DockContextEndFrame()
+//-----------------------------------------------------------------------------
+
+//-----------------------------------------------------------------------------
+// Docking: Internal Types
+//-----------------------------------------------------------------------------
+// - ImGuiDockRequestType
+// - ImGuiDockRequest
+// - ImGuiDockPreviewData
+// - ImGuiDockNodeSettings
+// - ImGuiDockContext
+//-----------------------------------------------------------------------------
+
+enum ImGuiDockRequestType
+{
+    ImGuiDockRequestType_None = 0,
+    ImGuiDockRequestType_Dock,
+    ImGuiDockRequestType_Undock,
+    ImGuiDockRequestType_Split                  // Split is the same as Dock but without a DockPayload
+};
+
+struct ImGuiDockRequest
+{
+    ImGuiDockRequestType    Type;
+    ImGuiWindow*            DockTargetWindow;   // Destination/Target Window to dock into (may be a loose window or a DockNode, might be NULL in which case DockTargetNode cannot be NULL)
+    ImGuiDockNode*          DockTargetNode;     // Destination/Target Node to dock into
+    ImGuiWindow*            DockPayload;        // Source/Payload window to dock (may be a loose window or a DockNode), [Optional]
+    ImGuiDir                DockSplitDir;
+    float                   DockSplitRatio;
+    bool                    DockSplitOuter;
+    ImGuiWindow*            UndockTargetWindow;
+    ImGuiDockNode*          UndockTargetNode;
+
+    ImGuiDockRequest()
+    {
+        Type = ImGuiDockRequestType_None;
+        DockTargetWindow = DockPayload = UndockTargetWindow = NULL;
+        DockTargetNode = UndockTargetNode = NULL;
+        DockSplitDir = ImGuiDir_None;
+        DockSplitRatio = 0.5f;
+        DockSplitOuter = false;
+    }
+};
+
+struct ImGuiDockPreviewData
+{
+    ImGuiDockNode   FutureNode;
+    bool            IsDropAllowed;
+    bool            IsCenterAvailable;
+    bool            IsSidesAvailable;           // Hold your breath, grammar freaks..
+    bool            IsSplitDirExplicit;         // Set when hovered the drop rect (vs. implicit SplitDir==None when hovered the window)
+    ImGuiDockNode*  SplitNode;
+    ImGuiDir        SplitDir;
+    float           SplitRatio;
+    ImRect          DropRectsDraw[ImGuiDir_COUNT + 1];  // May be slightly different from hit-testing drop rects used in DockNodeCalcDropRects()
+
+    ImGuiDockPreviewData() : FutureNode(0) { IsDropAllowed = IsCenterAvailable = IsSidesAvailable = IsSplitDirExplicit = false; SplitNode = NULL; SplitDir = ImGuiDir_None; SplitRatio = 0.f; for (int n = 0; n < IM_ARRAYSIZE(DropRectsDraw); n++) DropRectsDraw[n] = ImRect(+FLT_MAX, +FLT_MAX, -FLT_MAX, -FLT_MAX); }
+};
+
+// Persistent Settings data, stored contiguously in SettingsNodes (sizeof() ~32 bytes)
+struct ImGuiDockNodeSettings
+{
+    ImGuiID             ID;
+    ImGuiID             ParentNodeId;
+    ImGuiID             ParentWindowId;
+    ImGuiID             SelectedTabId;
+    signed char         SplitAxis;
+    char                Depth;
+    ImGuiDockNodeFlags  Flags;                  // NB: We save individual flags one by one in ascii format (ImGuiDockNodeFlags_SavedFlagsMask_)
+    ImVec2ih            Pos;
+    ImVec2ih            Size;
+    ImVec2ih            SizeRef;
+    ImGuiDockNodeSettings() { memset(this, 0, sizeof(*this)); SplitAxis = ImGuiAxis_None; }
+};
+
+//-----------------------------------------------------------------------------
+// Docking: Forward Declarations
+//-----------------------------------------------------------------------------
+
+namespace ImGui
+{
+    // ImGuiDockContext
+    static ImGuiDockNode*   DockContextAddNode(ImGuiContext* ctx, ImGuiID id);
+    static void             DockContextRemoveNode(ImGuiContext* ctx, ImGuiDockNode* node, bool merge_sibling_into_parent_node);
+    static void             DockContextQueueNotifyRemovedNode(ImGuiContext* ctx, ImGuiDockNode* node);
+    static void             DockContextProcessDock(ImGuiContext* ctx, ImGuiDockRequest* req);
+    static void             DockContextPruneUnusedSettingsNodes(ImGuiContext* ctx);
+    static ImGuiDockNode*   DockContextBindNodeToWindow(ImGuiContext* ctx, ImGuiWindow* window);
+    static void             DockContextBuildNodesFromSettings(ImGuiContext* ctx, ImGuiDockNodeSettings* node_settings_array, int node_settings_count);
+    static void             DockContextBuildAddWindowsToNodes(ImGuiContext* ctx, ImGuiID root_id);                            // Use root_id==0 to add all
+
+    // ImGuiDockNode
+    static void             DockNodeAddWindow(ImGuiDockNode* node, ImGuiWindow* window, bool add_to_tab_bar);
+    static void             DockNodeMoveWindows(ImGuiDockNode* dst_node, ImGuiDockNode* src_node);
+    static void             DockNodeMoveChildNodes(ImGuiDockNode* dst_node, ImGuiDockNode* src_node);
+    static ImGuiWindow*     DockNodeFindWindowByID(ImGuiDockNode* node, ImGuiID id);
+    static void             DockNodeApplyPosSizeToWindows(ImGuiDockNode* node);
+    static void             DockNodeRemoveWindow(ImGuiDockNode* node, ImGuiWindow* window, ImGuiID save_dock_id);
+    static void             DockNodeHideHostWindow(ImGuiDockNode* node);
+    static void             DockNodeUpdate(ImGuiDockNode* node);
+    static void             DockNodeUpdateForRootNode(ImGuiDockNode* node);
+    static void             DockNodeUpdateFlagsAndCollapse(ImGuiDockNode* node);
+    static void             DockNodeUpdateHasCentralNodeChild(ImGuiDockNode* node);
+    static void             DockNodeUpdateTabBar(ImGuiDockNode* node, ImGuiWindow* host_window);
+    static void             DockNodeAddTabBar(ImGuiDockNode* node);
+    static void             DockNodeRemoveTabBar(ImGuiDockNode* node);
+    static void             DockNodeWindowMenuUpdate(ImGuiDockNode* node, ImGuiTabBar* tab_bar);
+    static void             DockNodeUpdateVisibleFlag(ImGuiDockNode* node);
+    static void             DockNodeStartMouseMovingWindow(ImGuiDockNode* node, ImGuiWindow* window);
+    static bool             DockNodeIsDropAllowed(ImGuiWindow* host_window, ImGuiWindow* payload_window);
+    static void             DockNodePreviewDockSetup(ImGuiWindow* host_window, ImGuiDockNode* host_node, ImGuiWindow* payload_window, ImGuiDockNode* payload_node, ImGuiDockPreviewData* preview_data, bool is_explicit_target, bool is_outer_docking);
+    static void             DockNodePreviewDockRender(ImGuiWindow* host_window, ImGuiDockNode* host_node, ImGuiWindow* payload_window, const ImGuiDockPreviewData* preview_data);
+    static void             DockNodeCalcTabBarLayout(const ImGuiDockNode* node, ImRect* out_title_rect, ImRect* out_tab_bar_rect, ImVec2* out_window_menu_button_pos, ImVec2* out_close_button_pos);
+    static void             DockNodeCalcSplitRects(ImVec2& pos_old, ImVec2& size_old, ImVec2& pos_new, ImVec2& size_new, ImGuiDir dir, ImVec2 size_new_desired);
+    static bool             DockNodeCalcDropRectsAndTestMousePos(const ImRect& parent, ImGuiDir dir, ImRect& out_draw, bool outer_docking, ImVec2* test_mouse_pos);
+    static const char*      DockNodeGetHostWindowTitle(ImGuiDockNode* node, char* buf, int buf_size) { ImFormatString(buf, buf_size, "##DockNode_%02X", node->ID); return buf; }
+    static int              DockNodeGetTabOrder(ImGuiWindow* window);
+
+    // ImGuiDockNode tree manipulations
+    static void             DockNodeTreeSplit(ImGuiContext* ctx, ImGuiDockNode* parent_node, ImGuiAxis split_axis, int split_first_child, float split_ratio, ImGuiDockNode* new_node);
+    static void             DockNodeTreeMerge(ImGuiContext* ctx, ImGuiDockNode* parent_node, ImGuiDockNode* merge_lead_child);
+    static void             DockNodeTreeUpdatePosSize(ImGuiDockNode* node, ImVec2 pos, ImVec2 size, ImGuiDockNode* only_write_to_single_node = NULL);
+    static void             DockNodeTreeUpdateSplitter(ImGuiDockNode* node);
+    static ImGuiDockNode*   DockNodeTreeFindVisibleNodeByPos(ImGuiDockNode* node, ImVec2 pos);
+    static ImGuiDockNode*   DockNodeTreeFindFallbackLeafNode(ImGuiDockNode* node);
+
+    // Settings
+    static void             DockSettingsRenameNodeReferences(ImGuiID old_node_id, ImGuiID new_node_id);
+    static void             DockSettingsRemoveNodeReferences(ImGuiID* node_ids, int node_ids_count);
+    static ImGuiDockNodeSettings*   DockSettingsFindNodeSettings(ImGuiContext* ctx, ImGuiID node_id);
+    static void             DockSettingsHandler_ClearAll(ImGuiContext*, ImGuiSettingsHandler*);
+    static void             DockSettingsHandler_ApplyAll(ImGuiContext*, ImGuiSettingsHandler*);
+    static void*            DockSettingsHandler_ReadOpen(ImGuiContext*, ImGuiSettingsHandler*, const char* name);
+    static void             DockSettingsHandler_ReadLine(ImGuiContext*, ImGuiSettingsHandler*, void* entry, const char* line);
+    static void             DockSettingsHandler_WriteAll(ImGuiContext* imgui_ctx, ImGuiSettingsHandler* handler, ImGuiTextBuffer* buf);
+}
+
+//-----------------------------------------------------------------------------
+// Docking: ImGuiDockContext
+//-----------------------------------------------------------------------------
+// The lifetime model is different from the one of regular windows: we always create a ImGuiDockNode for each ImGuiDockNodeSettings,
+// or we always hold the entire docking node tree. Nodes are frequently hidden, e.g. if the window(s) or child nodes they host are not active.
+// At boot time only, we run a simple GC to remove nodes that have no references.
+// Because dock node settings (which are small, contiguous structures) are always mirrored by their corresponding dock nodes (more complete structures),
+// we can also very easily recreate the nodes from scratch given the settings data (this is what DockContextRebuild() does).
+// This is convenient as docking reconfiguration can be implemented by mostly poking at the simpler settings data.
+//-----------------------------------------------------------------------------
+// - DockContextInitialize()
+// - DockContextShutdown()
+// - DockContextClearNodes()
+// - DockContextRebuildNodes()
+// - DockContextNewFrameUpdateUndocking()
+// - DockContextNewFrameUpdateDocking()
+// - DockContextEndFrame()
+// - DockContextFindNodeByID()
+// - DockContextBindNodeToWindow()
+// - DockContextGenNodeID()
+// - DockContextAddNode()
+// - DockContextRemoveNode()
+// - ImGuiDockContextPruneNodeData
+// - DockContextPruneUnusedSettingsNodes()
+// - DockContextBuildNodesFromSettings()
+// - DockContextBuildAddWindowsToNodes()
+//-----------------------------------------------------------------------------
+
+void ImGui::DockContextInitialize(ImGuiContext* ctx)
+{
+    ImGuiContext& g = *ctx;
+
+    // Add .ini handle for persistent docking data
+    ImGuiSettingsHandler ini_handler;
+    ini_handler.TypeName = "Docking";
+    ini_handler.TypeHash = ImHashStr("Docking");
+    ini_handler.ClearAllFn = DockSettingsHandler_ClearAll;
+    ini_handler.ReadInitFn = DockSettingsHandler_ClearAll; // Also clear on read
+    ini_handler.ReadOpenFn = DockSettingsHandler_ReadOpen;
+    ini_handler.ReadLineFn = DockSettingsHandler_ReadLine;
+    ini_handler.ApplyAllFn = DockSettingsHandler_ApplyAll;
+    ini_handler.WriteAllFn = DockSettingsHandler_WriteAll;
+    g.SettingsHandlers.push_back(ini_handler);
+
+    g.DockNodeWindowMenuHandler = &DockNodeWindowMenuHandler_Default;
+}
+
+void ImGui::DockContextShutdown(ImGuiContext* ctx)
+{
+    ImGuiDockContext* dc = &ctx->DockContext;
+    for (int n = 0; n < dc->Nodes.Data.Size; n++)
+        if (ImGuiDockNode* node = (ImGuiDockNode*)dc->Nodes.Data[n].val_p)
+            IM_DELETE(node);
+}
+
+void ImGui::DockContextClearNodes(ImGuiContext* ctx, ImGuiID root_id, bool clear_settings_refs)
+{
+    IM_UNUSED(ctx);
+    IM_ASSERT(ctx == GImGui);
+    DockBuilderRemoveNodeDockedWindows(root_id, clear_settings_refs);
+    DockBuilderRemoveNodeChildNodes(root_id);
+}
+
+// [DEBUG] This function also acts as a defacto test to make sure we can rebuild from scratch without a glitch
+// (Different from DockSettingsHandler_ClearAll() + DockSettingsHandler_ApplyAll() because this reuses current settings!)
+void ImGui::DockContextRebuildNodes(ImGuiContext* ctx)
+{
+    ImGuiContext& g = *ctx;
+    ImGuiDockContext* dc = &ctx->DockContext;
+    IMGUI_DEBUG_LOG_DOCKING("[docking] DockContextRebuildNodes\n");
+    SaveIniSettingsToMemory();
+    ImGuiID root_id = 0; // Rebuild all
+    DockContextClearNodes(ctx, root_id, false);
+    DockContextBuildNodesFromSettings(ctx, dc->NodesSettings.Data, dc->NodesSettings.Size);
+    DockContextBuildAddWindowsToNodes(ctx, root_id);
+}
+
+// Docking context update function, called by NewFrame()
+void ImGui::DockContextNewFrameUpdateUndocking(ImGuiContext* ctx)
+{
+    ImGuiContext& g = *ctx;
+    ImGuiDockContext* dc = &ctx->DockContext;
+    if (!(g.IO.ConfigFlags & ImGuiConfigFlags_DockingEnable))
+    {
+        if (dc->Nodes.Data.Size > 0 || dc->Requests.Size > 0)
+            DockContextClearNodes(ctx, 0, true);
+        return;
+    }
+
+    // Setting NoSplit at runtime merges all nodes
+    if (g.IO.ConfigDockingNoSplit)
+        for (int n = 0; n < dc->Nodes.Data.Size; n++)
+            if (ImGuiDockNode* node = (ImGuiDockNode*)dc->Nodes.Data[n].val_p)
+                if (node->IsRootNode() && node->IsSplitNode())
+                {
+                    DockBuilderRemoveNodeChildNodes(node->ID);
+                    //dc->WantFullRebuild = true;
+                }
+
+    // Process full rebuild
+#if 0
+    if (ImGui::IsKeyPressed(ImGui::GetKeyIndex(ImGuiKey_C)))
+        dc->WantFullRebuild = true;
+#endif
+    if (dc->WantFullRebuild)
+    {
+        DockContextRebuildNodes(ctx);
+        dc->WantFullRebuild = false;
+    }
+
+    // Process Undocking requests (we need to process them _before_ the UpdateMouseMovingWindowNewFrame call in NewFrame)
+    for (ImGuiDockRequest& req : dc->Requests)
+    {
+        if (req.Type == ImGuiDockRequestType_Undock && req.UndockTargetWindow)
+            DockContextProcessUndockWindow(ctx, req.UndockTargetWindow);
+        else if (req.Type == ImGuiDockRequestType_Undock && req.UndockTargetNode)
+            DockContextProcessUndockNode(ctx, req.UndockTargetNode);
+    }
+}
+
+// Docking context update function, called by NewFrame()
+void ImGui::DockContextNewFrameUpdateDocking(ImGuiContext* ctx)
+{
+    ImGuiContext& g = *ctx;
+    ImGuiDockContext* dc = &ctx->DockContext;
+    if (!(g.IO.ConfigFlags & ImGuiConfigFlags_DockingEnable))
+        return;
+
+    // [DEBUG] Store hovered dock node.
+    // We could in theory use DockNodeTreeFindVisibleNodeByPos() on the root host dock node, but using ->DockNode is a good shortcut.
+    // Note this is mostly a debug thing and isn't actually used for docking target, because docking involve more detailed filtering.
+    g.DebugHoveredDockNode = NULL;
+    if (ImGuiWindow* hovered_window = g.HoveredWindowUnderMovingWindow)
+    {
+        if (hovered_window->DockNodeAsHost)
+            g.DebugHoveredDockNode = DockNodeTreeFindVisibleNodeByPos(hovered_window->DockNodeAsHost, g.IO.MousePos);
+        else if (hovered_window->RootWindow->DockNode)
+            g.DebugHoveredDockNode = hovered_window->RootWindow->DockNode;
+    }
+
+    // Process Docking requests
+    for (ImGuiDockRequest& req : dc->Requests)
+        if (req.Type == ImGuiDockRequestType_Dock)
+            DockContextProcessDock(ctx, &req);
+    dc->Requests.resize(0);
+
+    // Create windows for each automatic docking nodes
+    // We can have NULL pointers when we delete nodes, but because ID are recycled this should amortize nicely (and our node count will never be very high)
+    for (int n = 0; n < dc->Nodes.Data.Size; n++)
+        if (ImGuiDockNode* node = (ImGuiDockNode*)dc->Nodes.Data[n].val_p)
+            if (node->IsFloatingNode())
+                DockNodeUpdate(node);
+}
+
+void ImGui::DockContextEndFrame(ImGuiContext* ctx)
+{
+    // Draw backgrounds of node missing their window
+    ImGuiContext& g = *ctx;
+    ImGuiDockContext* dc = &g.DockContext;
+    for (int n = 0; n < dc->Nodes.Data.Size; n++)
+        if (ImGuiDockNode* node = (ImGuiDockNode*)dc->Nodes.Data[n].val_p)
+            if (node->LastFrameActive == g.FrameCount && node->IsVisible && node->HostWindow && node->IsLeafNode() && !node->IsBgDrawnThisFrame)
+            {
+                ImRect bg_rect(node->Pos + ImVec2(0.0f, GetFrameHeight()), node->Pos + node->Size);
+                ImDrawFlags bg_rounding_flags = CalcRoundingFlagsForRectInRect(bg_rect, node->HostWindow->Rect(), g.Style.DockingSeparatorSize);
+                node->HostWindow->DrawList->ChannelsSetCurrent(DOCKING_HOST_DRAW_CHANNEL_BG);
+                node->HostWindow->DrawList->AddRectFilled(bg_rect.Min, bg_rect.Max, node->LastBgColor, node->HostWindow->WindowRounding, bg_rounding_flags);
+            }
+}
+
+ImGuiDockNode* ImGui::DockContextFindNodeByID(ImGuiContext* ctx, ImGuiID id)
+{
+    return (ImGuiDockNode*)ctx->DockContext.Nodes.GetVoidPtr(id);
+}
+
+ImGuiID ImGui::DockContextGenNodeID(ImGuiContext* ctx)
+{
+    // Generate an ID for new node (the exact ID value doesn't matter as long as it is not already used)
+    // FIXME-OPT FIXME-DOCK: This is suboptimal, even if the node count is small enough not to be a worry.0
+    // We should poke in ctx->Nodes to find a suitable ID faster. Even more so trivial that ctx->Nodes lookup is already sorted.
+    ImGuiID id = 0x0001;
+    while (DockContextFindNodeByID(ctx, id) != NULL)
+        id++;
+    return id;
+}
+
+static ImGuiDockNode* ImGui::DockContextAddNode(ImGuiContext* ctx, ImGuiID id)
+{
+    // Generate an ID for the new node (the exact ID value doesn't matter as long as it is not already used) and add the first window.
+    ImGuiContext& g = *ctx;
+    if (id == 0)
+        id = DockContextGenNodeID(ctx);
+    else
+        IM_ASSERT(DockContextFindNodeByID(ctx, id) == NULL);
+
+    // We don't set node->LastFrameAlive on construction. Nodes are always created at all time to reflect .ini settings!
+    IMGUI_DEBUG_LOG_DOCKING("[docking] DockContextAddNode 0x%08X\n", id);
+    ImGuiDockNode* node = IM_NEW(ImGuiDockNode)(id);
+    ctx->DockContext.Nodes.SetVoidPtr(node->ID, node);
+    return node;
+}
+
+static void ImGui::DockContextRemoveNode(ImGuiContext* ctx, ImGuiDockNode* node, bool merge_sibling_into_parent_node)
+{
+    ImGuiContext& g = *ctx;
+    ImGuiDockContext* dc = &ctx->DockContext;
+
+    IMGUI_DEBUG_LOG_DOCKING("[docking] DockContextRemoveNode 0x%08X\n", node->ID);
+    IM_ASSERT(DockContextFindNodeByID(ctx, node->ID) == node);
+    IM_ASSERT(node->ChildNodes[0] == NULL && node->ChildNodes[1] == NULL);
+    IM_ASSERT(node->Windows.Size == 0);
+
+    if (node->HostWindow)
+        node->HostWindow->DockNodeAsHost = NULL;
+
+    ImGuiDockNode* parent_node = node->ParentNode;
+    const bool merge = (merge_sibling_into_parent_node && parent_node != NULL);
+    if (merge)
+    {
+        IM_ASSERT(parent_node->ChildNodes[0] == node || parent_node->ChildNodes[1] == node);
+        ImGuiDockNode* sibling_node = (parent_node->ChildNodes[0] == node ? parent_node->ChildNodes[1] : parent_node->ChildNodes[0]);
+        DockNodeTreeMerge(&g, parent_node, sibling_node);
+    }
+    else
+    {
+        for (int n = 0; parent_node && n < IM_ARRAYSIZE(parent_node->ChildNodes); n++)
+            if (parent_node->ChildNodes[n] == node)
+                node->ParentNode->ChildNodes[n] = NULL;
+        dc->Nodes.SetVoidPtr(node->ID, NULL);
+        IM_DELETE(node);
+    }
+}
+
+static int IMGUI_CDECL DockNodeComparerDepthMostFirst(const void* lhs, const void* rhs)
+{
+    const ImGuiDockNode* a = *(const ImGuiDockNode* const*)lhs;
+    const ImGuiDockNode* b = *(const ImGuiDockNode* const*)rhs;
+    return ImGui::DockNodeGetDepth(b) - ImGui::DockNodeGetDepth(a);
+}
+
+// Pre C++0x doesn't allow us to use a function-local type (without linkage) as template parameter, so we moved this here.
+struct ImGuiDockContextPruneNodeData
+{
+    int         CountWindows, CountChildWindows, CountChildNodes;
+    ImGuiID     RootId;
+    ImGuiDockContextPruneNodeData() { CountWindows = CountChildWindows = CountChildNodes = 0; RootId = 0; }
+};
+
+// Garbage collect unused nodes (run once at init time)
+static void ImGui::DockContextPruneUnusedSettingsNodes(ImGuiContext* ctx)
+{
+    ImGuiContext& g = *ctx;
+    ImGuiDockContext* dc = &ctx->DockContext;
+    IM_ASSERT(g.Windows.Size == 0);
+
+    ImPool<ImGuiDockContextPruneNodeData> pool;
+    pool.Reserve(dc->NodesSettings.Size);
+
+    // Count child nodes and compute RootID
+    for (int settings_n = 0; settings_n < dc->NodesSettings.Size; settings_n++)
+    {
+        ImGuiDockNodeSettings* settings = &dc->NodesSettings[settings_n];
+        ImGuiDockContextPruneNodeData* parent_data = settings->ParentNodeId ? pool.GetByKey(settings->ParentNodeId) : 0;
+        pool.GetOrAddByKey(settings->ID)->RootId = parent_data ? parent_data->RootId : settings->ID;
+        if (settings->ParentNodeId)
+            pool.GetOrAddByKey(settings->ParentNodeId)->CountChildNodes++;
+    }
+
+    // Count reference to dock ids from dockspaces
+    // We track the 'auto-DockNode <- manual-Window <- manual-DockSpace' in order to avoid 'auto-DockNode' being ditched by DockContextPruneUnusedSettingsNodes()
+    for (int settings_n = 0; settings_n < dc->NodesSettings.Size; settings_n++)
+    {
+        ImGuiDockNodeSettings* settings = &dc->NodesSettings[settings_n];
+        if (settings->ParentWindowId != 0)
+            if (ImGuiWindowSettings* window_settings = FindWindowSettingsByID(settings->ParentWindowId))
+                if (window_settings->DockId)
+                    if (ImGuiDockContextPruneNodeData* data = pool.GetByKey(window_settings->DockId))
+                        data->CountChildNodes++;
+    }
+
+    // Count reference to dock ids from window settings
+    // We guard against the possibility of an invalid .ini file (RootID may point to a missing node)
+    for (ImGuiWindowSettings* settings = g.SettingsWindows.begin(); settings != NULL; settings = g.SettingsWindows.next_chunk(settings))
+        if (ImGuiID dock_id = settings->DockId)
+            if (ImGuiDockContextPruneNodeData* data = pool.GetByKey(dock_id))
+            {
+                data->CountWindows++;
+                if (ImGuiDockContextPruneNodeData* data_root = (data->RootId == dock_id) ? data : pool.GetByKey(data->RootId))
+                    data_root->CountChildWindows++;
+            }
+
+    // Prune
+    for (int settings_n = 0; settings_n < dc->NodesSettings.Size; settings_n++)
+    {
+        ImGuiDockNodeSettings* settings = &dc->NodesSettings[settings_n];
+        ImGuiDockContextPruneNodeData* data = pool.GetByKey(settings->ID);
+        if (data->CountWindows > 1)
+            continue;
+        ImGuiDockContextPruneNodeData* data_root = (data->RootId == settings->ID) ? data : pool.GetByKey(data->RootId);
+
+        bool remove = false;
+        remove |= (data->CountWindows == 1 && settings->ParentNodeId == 0 && data->CountChildNodes == 0 && !(settings->Flags & ImGuiDockNodeFlags_CentralNode));  // Floating root node with only 1 window
+        remove |= (data->CountWindows == 0 && settings->ParentNodeId == 0 && data->CountChildNodes == 0); // Leaf nodes with 0 window
+        remove |= (data_root->CountChildWindows == 0);
+        if (remove)
+        {
+            IMGUI_DEBUG_LOG_DOCKING("[docking] DockContextPruneUnusedSettingsNodes: Prune 0x%08X\n", settings->ID);
+            DockSettingsRemoveNodeReferences(&settings->ID, 1);
+            settings->ID = 0;
+        }
+    }
+}
+
+static void ImGui::DockContextBuildNodesFromSettings(ImGuiContext* ctx, ImGuiDockNodeSettings* node_settings_array, int node_settings_count)
+{
+    // Build nodes
+    for (int node_n = 0; node_n < node_settings_count; node_n++)
+    {
+        ImGuiDockNodeSettings* settings = &node_settings_array[node_n];
+        if (settings->ID == 0)
+            continue;
+        ImGuiDockNode* node = DockContextAddNode(ctx, settings->ID);
+        node->ParentNode = settings->ParentNodeId ? DockContextFindNodeByID(ctx, settings->ParentNodeId) : NULL;
+        node->Pos = ImVec2(settings->Pos.x, settings->Pos.y);
+        node->Size = ImVec2(settings->Size.x, settings->Size.y);
+        node->SizeRef = ImVec2(settings->SizeRef.x, settings->SizeRef.y);
+        node->AuthorityForPos = node->AuthorityForSize = node->AuthorityForViewport = ImGuiDataAuthority_DockNode;
+        if (node->ParentNode && node->ParentNode->ChildNodes[0] == NULL)
+            node->ParentNode->ChildNodes[0] = node;
+        else if (node->ParentNode && node->ParentNode->ChildNodes[1] == NULL)
+            node->ParentNode->ChildNodes[1] = node;
+        node->SelectedTabId = settings->SelectedTabId;
+        node->SplitAxis = (ImGuiAxis)settings->SplitAxis;
+        node->SetLocalFlags(settings->Flags & ImGuiDockNodeFlags_SavedFlagsMask_);
+
+        // Bind host window immediately if it already exist (in case of a rebuild)
+        // This is useful as the RootWindowForTitleBarHighlight links necessary to highlight the currently focused node requires node->HostWindow to be set.
+        char host_window_title[20];
+        ImGuiDockNode* root_node = DockNodeGetRootNode(node);
+        node->HostWindow = FindWindowByName(DockNodeGetHostWindowTitle(root_node, host_window_title, IM_ARRAYSIZE(host_window_title)));
+    }
+}
+
+void ImGui::DockContextBuildAddWindowsToNodes(ImGuiContext* ctx, ImGuiID root_id)
+{
+    // Rebind all windows to nodes (they can also lazily rebind but we'll have a visible glitch during the first frame)
+    ImGuiContext& g = *ctx;
+    for (ImGuiWindow* window : g.Windows)
+    {
+        if (window->DockId == 0 || window->LastFrameActive < g.FrameCount - 1)
+            continue;
+        if (window->DockNode != NULL)
+            continue;
+
+        ImGuiDockNode* node = DockContextFindNodeByID(ctx, window->DockId);
+        IM_ASSERT(node != NULL);   // This should have been called after DockContextBuildNodesFromSettings()
+        if (root_id == 0 || DockNodeGetRootNode(node)->ID == root_id)
+            DockNodeAddWindow(node, window, true);
+    }
+}
+
+//-----------------------------------------------------------------------------
+// Docking: ImGuiDockContext Docking/Undocking functions
+//-----------------------------------------------------------------------------
+// - DockContextQueueDock()
+// - DockContextQueueUndockWindow()
+// - DockContextQueueUndockNode()
+// - DockContextQueueNotifyRemovedNode()
+// - DockContextProcessDock()
+// - DockContextProcessUndockWindow()
+// - DockContextProcessUndockNode()
+// - DockContextCalcDropPosForDocking()
+//-----------------------------------------------------------------------------
+
+void ImGui::DockContextQueueDock(ImGuiContext* ctx, ImGuiWindow* target, ImGuiDockNode* target_node, ImGuiWindow* payload, ImGuiDir split_dir, float split_ratio, bool split_outer)
+{
+    IM_ASSERT(target != payload);
+    ImGuiDockRequest req;
+    req.Type = ImGuiDockRequestType_Dock;
+    req.DockTargetWindow = target;
+    req.DockTargetNode = target_node;
+    req.DockPayload = payload;
+    req.DockSplitDir = split_dir;
+    req.DockSplitRatio = split_ratio;
+    req.DockSplitOuter = split_outer;
+    ctx->DockContext.Requests.push_back(req);
+}
+
+void ImGui::DockContextQueueUndockWindow(ImGuiContext* ctx, ImGuiWindow* window)
+{
+    ImGuiDockRequest req;
+    req.Type = ImGuiDockRequestType_Undock;
+    req.UndockTargetWindow = window;
+    ctx->DockContext.Requests.push_back(req);
+}
+
+void ImGui::DockContextQueueUndockNode(ImGuiContext* ctx, ImGuiDockNode* node)
+{
+    ImGuiDockRequest req;
+    req.Type = ImGuiDockRequestType_Undock;
+    req.UndockTargetNode = node;
+    ctx->DockContext.Requests.push_back(req);
+}
+
+void ImGui::DockContextQueueNotifyRemovedNode(ImGuiContext* ctx, ImGuiDockNode* node)
+{
+    ImGuiDockContext* dc = &ctx->DockContext;
+    for (ImGuiDockRequest& req : dc->Requests)
+        if (req.DockTargetNode == node)
+            req.Type = ImGuiDockRequestType_None;
+}
+
+void ImGui::DockContextProcessDock(ImGuiContext* ctx, ImGuiDockRequest* req)
+{
+    IM_ASSERT((req->Type == ImGuiDockRequestType_Dock && req->DockPayload != NULL) || (req->Type == ImGuiDockRequestType_Split && req->DockPayload == NULL));
+    IM_ASSERT(req->DockTargetWindow != NULL || req->DockTargetNode != NULL);
+
+    ImGuiContext& g = *ctx;
+    IM_UNUSED(g);
+
+    ImGuiWindow* payload_window = req->DockPayload;     // Optional
+    ImGuiWindow* target_window = req->DockTargetWindow;
+    ImGuiDockNode* node = req->DockTargetNode;
+    if (payload_window)
+        IMGUI_DEBUG_LOG_DOCKING("[docking] DockContextProcessDock node 0x%08X target '%s' dock window '%s', split_dir %d\n", node ? node->ID : 0, target_window ? target_window->Name : "NULL", payload_window->Name, req->DockSplitDir);
+    else
+        IMGUI_DEBUG_LOG_DOCKING("[docking] DockContextProcessDock node 0x%08X, split_dir %d\n", node ? node->ID : 0, req->DockSplitDir);
+
+    // Decide which Tab will be selected at the end of the operation
+    ImGuiID next_selected_id = 0;
+    ImGuiDockNode* payload_node = NULL;
+    if (payload_window)
+    {
+        payload_node = payload_window->DockNodeAsHost;
+        payload_window->DockNodeAsHost = NULL; // Important to clear this as the node will have its life as a child which might be merged/deleted later.
+        if (payload_node && payload_node->IsLeafNode())
+            next_selected_id = payload_node->TabBar->NextSelectedTabId ? payload_node->TabBar->NextSelectedTabId : payload_node->TabBar->SelectedTabId;
+        if (payload_node == NULL)
+            next_selected_id = payload_window->TabId;
+    }
+
+    // FIXME-DOCK: When we are trying to dock an existing single-window node into a loose window, transfer Node ID as well
+    // When processing an interactive split, usually LastFrameAlive will be < g.FrameCount. But DockBuilder operations can make it ==.
+    if (node)
+        IM_ASSERT(node->LastFrameAlive <= g.FrameCount);
+    if (node && target_window && node == target_window->DockNodeAsHost)
+        IM_ASSERT(node->Windows.Size > 0 || node->IsSplitNode() || node->IsCentralNode());
+
+    // Create new node and add existing window to it
+    if (node == NULL)
+    {
+        node = DockContextAddNode(ctx, 0);
+        node->Pos = target_window->Pos;
+        node->Size = target_window->Size;
+        if (target_window->DockNodeAsHost == NULL)
+        {
+            DockNodeAddWindow(node, target_window, true);
+            node->TabBar->Tabs[0].Flags &= ~ImGuiTabItemFlags_Unsorted;
+            target_window->DockIsActive = true;
+        }
+    }
+
+    ImGuiDir split_dir = req->DockSplitDir;
+    if (split_dir != ImGuiDir_None)
+    {
+        // Split into two, one side will be our payload node unless we are dropping a loose window
+        const ImGuiAxis split_axis = (split_dir == ImGuiDir_Left || split_dir == ImGuiDir_Right) ? ImGuiAxis_X : ImGuiAxis_Y;
+        const int split_inheritor_child_idx = (split_dir == ImGuiDir_Left || split_dir == ImGuiDir_Up) ? 1 : 0; // Current contents will be moved to the opposite side
+        const float split_ratio = req->DockSplitRatio;
+        DockNodeTreeSplit(ctx, node, split_axis, split_inheritor_child_idx, split_ratio, payload_node);  // payload_node may be NULL here!
+        ImGuiDockNode* new_node = node->ChildNodes[split_inheritor_child_idx ^ 1];
+        new_node->HostWindow = node->HostWindow;
+        node = new_node;
+    }
+    node->SetLocalFlags(node->LocalFlags & ~ImGuiDockNodeFlags_HiddenTabBar);
+
+    if (node != payload_node)
+    {
+        // Create tab bar before we call DockNodeMoveWindows (which would attempt to move the old tab-bar, which would lead us to payload tabs wrongly appearing before target tabs!)
+        if (node->Windows.Size > 0 && node->TabBar == NULL)
+        {
+            DockNodeAddTabBar(node);
+            for (int n = 0; n < node->Windows.Size; n++)
+                TabBarAddTab(node->TabBar, ImGuiTabItemFlags_None, node->Windows[n]);
+        }
+
+        if (payload_node != NULL)
+        {
+            // Transfer full payload node (with 1+ child windows or child nodes)
+            if (payload_node->IsSplitNode())
+            {
+                if (node->Windows.Size > 0)
+                {
+                    // We can dock a split payload into a node that already has windows _only_ if our payload is a node tree with a single visible node.
+                    // In this situation, we move the windows of the target node into the currently visible node of the payload.
+                    // This allows us to preserve some of the underlying dock tree settings nicely.
+                    IM_ASSERT(payload_node->OnlyNodeWithWindows != NULL); // The docking should have been blocked by DockNodePreviewDockSetup() early on and never submitted.
+                    ImGuiDockNode* visible_node = payload_node->OnlyNodeWithWindows;
+                    if (visible_node->TabBar)
+                        IM_ASSERT(visible_node->TabBar->Tabs.Size > 0);
+                    DockNodeMoveWindows(node, visible_node);
+                    DockNodeMoveWindows(visible_node, node);
+                    DockSettingsRenameNodeReferences(node->ID, visible_node->ID);
+                }
+                if (node->IsCentralNode())
+                {
+                    // Central node property needs to be moved to a leaf node, pick the last focused one.
+                    // FIXME-DOCK: If we had to transfer other flags here, what would the policy be?
+                    ImGuiDockNode* last_focused_node = DockContextFindNodeByID(ctx, payload_node->LastFocusedNodeId);
+                    IM_ASSERT(last_focused_node != NULL);
+                    ImGuiDockNode* last_focused_root_node = DockNodeGetRootNode(last_focused_node);
+                    IM_ASSERT(last_focused_root_node == DockNodeGetRootNode(payload_node));
+                    last_focused_node->SetLocalFlags(last_focused_node->LocalFlags | ImGuiDockNodeFlags_CentralNode);
+                    node->SetLocalFlags(node->LocalFlags & ~ImGuiDockNodeFlags_CentralNode);
+                    last_focused_root_node->CentralNode = last_focused_node;
+                }
+
+                IM_ASSERT(node->Windows.Size == 0);
+                DockNodeMoveChildNodes(node, payload_node);
+            }
+            else
+            {
+                const ImGuiID payload_dock_id = payload_node->ID;
+                DockNodeMoveWindows(node, payload_node);
+                DockSettingsRenameNodeReferences(payload_dock_id, node->ID);
+            }
+            DockContextRemoveNode(ctx, payload_node, true);
+        }
+        else if (payload_window)
+        {
+            // Transfer single window
+            const ImGuiID payload_dock_id = payload_window->DockId;
+            node->VisibleWindow = payload_window;
+            DockNodeAddWindow(node, payload_window, true);
+            if (payload_dock_id != 0)
+                DockSettingsRenameNodeReferences(payload_dock_id, node->ID);
+        }
+    }
+    else
+    {
+        // When docking a floating single window node we want to reevaluate auto-hiding of the tab bar
+        node->WantHiddenTabBarUpdate = true;
+    }
+
+    // Update selection immediately
+    if (ImGuiTabBar* tab_bar = node->TabBar)
+        tab_bar->NextSelectedTabId = next_selected_id;
+    MarkIniSettingsDirty();
+}
+
+// Problem:
+//   Undocking a large (~full screen) window would leave it so large that the bottom right sizing corner would more
+//   than likely be off the screen and the window would be hard to resize to fit on screen. This can be particularly problematic
+//   with 'ConfigWindowsMoveFromTitleBarOnly=true' and/or with 'ConfigWindowsResizeFromEdges=false' as well (the later can be
+//   due to missing ImGuiBackendFlags_HasMouseCursors backend flag).
+// Solution:
+//   When undocking a window we currently force its maximum size to 90% of the host viewport or monitor.
+// Reevaluate this when we implement preserving docked/undocked size ("docking_wip/undocked_size" branch).
+static ImVec2 FixLargeWindowsWhenUndocking(const ImVec2& size, ImGuiViewport* ref_viewport)
+{
+    if (ref_viewport == NULL)
+        return size;
+
+    ImGuiContext& g = *GImGui;
+    ImVec2 max_size = ImTrunc(ref_viewport->WorkSize * 0.90f);
+    if (g.ConfigFlagsCurrFrame & ImGuiConfigFlags_ViewportsEnable)
+    {
+        const ImGuiPlatformMonitor* monitor = ImGui::GetViewportPlatformMonitor(ref_viewport);
+        max_size = ImTrunc(monitor->WorkSize * 0.90f);
+    }
+    return ImMin(size, max_size);
+}
+
+void ImGui::DockContextProcessUndockWindow(ImGuiContext* ctx, ImGuiWindow* window, bool clear_persistent_docking_ref)
+{
+    ImGuiContext& g = *ctx;
+    IMGUI_DEBUG_LOG_DOCKING("[docking] DockContextProcessUndockWindow window '%s', clear_persistent_docking_ref = %d\n", window->Name, clear_persistent_docking_ref);
+    if (window->DockNode)
+        DockNodeRemoveWindow(window->DockNode, window, clear_persistent_docking_ref ? 0 : window->DockId);
+    else
+        window->DockId = 0;
+    window->Collapsed = false;
+    window->DockIsActive = false;
+    window->DockNodeIsVisible = window->DockTabIsVisible = false;
+    window->Size = window->SizeFull = FixLargeWindowsWhenUndocking(window->SizeFull, window->Viewport);
+
+    MarkIniSettingsDirty();
+}
+
+void ImGui::DockContextProcessUndockNode(ImGuiContext* ctx, ImGuiDockNode* node)
+{
+    ImGuiContext& g = *ctx;
+    IMGUI_DEBUG_LOG_DOCKING("[docking] DockContextProcessUndockNode node %08X\n", node->ID);
+    IM_ASSERT(node->IsLeafNode());
+    IM_ASSERT(node->Windows.Size >= 1);
+
+    if (node->IsRootNode() || node->IsCentralNode())
+    {
+        // In the case of a root node or central node, the node will have to stay in place. Create a new node to receive the payload.
+        ImGuiDockNode* new_node = DockContextAddNode(ctx, 0);
+        new_node->Pos = node->Pos;
+        new_node->Size = node->Size;
+        new_node->SizeRef = node->SizeRef;
+        DockNodeMoveWindows(new_node, node);
+        DockSettingsRenameNodeReferences(node->ID, new_node->ID);
+        node = new_node;
+    }
+    else
+    {
+        // Otherwise extract our node and merge our sibling back into the parent node.
+        IM_ASSERT(node->ParentNode->ChildNodes[0] == node || node->ParentNode->ChildNodes[1] == node);
+        int index_in_parent = (node->ParentNode->ChildNodes[0] == node) ? 0 : 1;
+        node->ParentNode->ChildNodes[index_in_parent] = NULL;
+        DockNodeTreeMerge(ctx, node->ParentNode, node->ParentNode->ChildNodes[index_in_parent ^ 1]);
+        node->ParentNode->AuthorityForViewport = ImGuiDataAuthority_Window; // The node that stays in place keeps the viewport, so our newly dragged out node will create a new viewport
+        node->ParentNode = NULL;
+    }
+    for (ImGuiWindow* window : node->Windows)
+    {
+        window->Flags &= ~ImGuiWindowFlags_ChildWindow;
+        if (window->ParentWindow)
+            window->ParentWindow->DC.ChildWindows.find_erase(window);
+        UpdateWindowParentAndRootLinks(window, window->Flags, NULL);
+    }
+    node->AuthorityForPos = node->AuthorityForSize = ImGuiDataAuthority_DockNode;
+    node->Size = FixLargeWindowsWhenUndocking(node->Size, node->Windows[0]->Viewport);
+    node->WantMouseMove = true;
+    MarkIniSettingsDirty();
+}
+
+// This is mostly used for automation.
+bool ImGui::DockContextCalcDropPosForDocking(ImGuiWindow* target, ImGuiDockNode* target_node, ImGuiWindow* payload_window, ImGuiDockNode* payload_node, ImGuiDir split_dir, bool split_outer, ImVec2* out_pos)
+{
+    if (target != NULL && target_node == NULL)
+        target_node = target->DockNode;
+
+    // In DockNodePreviewDockSetup() for a root central node instead of showing both "inner" and "outer" drop rects
+    // (which would be functionally identical) we only show the outer one. Reflect this here.
+    if (target_node && target_node->ParentNode == NULL && target_node->IsCentralNode() && split_dir != ImGuiDir_None)
+        split_outer = true;
+    ImGuiDockPreviewData split_data;
+    DockNodePreviewDockSetup(target, target_node, payload_window, payload_node, &split_data, false, split_outer);
+    if (split_data.DropRectsDraw[split_dir+1].IsInverted())
+        return false;
+    *out_pos = split_data.DropRectsDraw[split_dir+1].GetCenter();
+    return true;
+}
+
+//-----------------------------------------------------------------------------
+// Docking: ImGuiDockNode
+//-----------------------------------------------------------------------------
+// - DockNodeGetTabOrder()
+// - DockNodeAddWindow()
+// - DockNodeRemoveWindow()
+// - DockNodeMoveChildNodes()
+// - DockNodeMoveWindows()
+// - DockNodeApplyPosSizeToWindows()
+// - DockNodeHideHostWindow()
+// - ImGuiDockNodeFindInfoResults
+// - DockNodeFindInfo()
+// - DockNodeFindWindowByID()
+// - DockNodeUpdateFlagsAndCollapse()
+// - DockNodeUpdateHasCentralNodeFlag()
+// - DockNodeUpdateVisibleFlag()
+// - DockNodeStartMouseMovingWindow()
+// - DockNodeUpdate()
+// - DockNodeUpdateWindowMenu()
+// - DockNodeBeginAmendTabBar()
+// - DockNodeEndAmendTabBar()
+// - DockNodeUpdateTabBar()
+// - DockNodeAddTabBar()
+// - DockNodeRemoveTabBar()
+// - DockNodeIsDropAllowedOne()
+// - DockNodeIsDropAllowed()
+// - DockNodeCalcTabBarLayout()
+// - DockNodeCalcSplitRects()
+// - DockNodeCalcDropRectsAndTestMousePos()
+// - DockNodePreviewDockSetup()
+// - DockNodePreviewDockRender()
+//-----------------------------------------------------------------------------
+
+ImGuiDockNode::ImGuiDockNode(ImGuiID id)
+{
+    ID = id;
+    SharedFlags = LocalFlags = LocalFlagsInWindows = MergedFlags = ImGuiDockNodeFlags_None;
+    ParentNode = ChildNodes[0] = ChildNodes[1] = NULL;
+    TabBar = NULL;
+    SplitAxis = ImGuiAxis_None;
+
+    State = ImGuiDockNodeState_Unknown;
+    LastBgColor = IM_COL32_WHITE;
+    HostWindow = VisibleWindow = NULL;
+    CentralNode = OnlyNodeWithWindows = NULL;
+    CountNodeWithWindows = 0;
+    LastFrameAlive = LastFrameActive = LastFrameFocused = -1;
+    LastFocusedNodeId = 0;
+    SelectedTabId = 0;
+    WantCloseTabId = 0;
+    RefViewportId = 0;
+    AuthorityForPos = AuthorityForSize = ImGuiDataAuthority_DockNode;
+    AuthorityForViewport = ImGuiDataAuthority_Auto;
+    IsVisible = true;
+    IsFocused = HasCloseButton = HasWindowMenuButton = HasCentralNodeChild = false;
+    IsBgDrawnThisFrame = false;
+    WantCloseAll = WantLockSizeOnce = WantMouseMove = WantHiddenTabBarUpdate = WantHiddenTabBarToggle = false;
+}
+
+ImGuiDockNode::~ImGuiDockNode()
+{
+    IM_DELETE(TabBar);
+    TabBar = NULL;
+    ChildNodes[0] = ChildNodes[1] = NULL;
+}
+
+int ImGui::DockNodeGetTabOrder(ImGuiWindow* window)
+{
+    ImGuiTabBar* tab_bar = window->DockNode->TabBar;
+    if (tab_bar == NULL)
+        return -1;
+    ImGuiTabItem* tab = TabBarFindTabByID(tab_bar, window->TabId);
+    return tab ? TabBarGetTabOrder(tab_bar, tab) : -1;
+}
+
+static void DockNodeHideWindowDuringHostWindowCreation(ImGuiWindow* window)
+{
+    window->Hidden = true;
+    window->HiddenFramesCanSkipItems = window->Active ? 1 : 2;
+}
+
+static void ImGui::DockNodeAddWindow(ImGuiDockNode* node, ImGuiWindow* window, bool add_to_tab_bar)
+{
+    ImGuiContext& g = *GImGui; (void)g;
+    if (window->DockNode)
+    {
+        // Can overwrite an existing window->DockNode (e.g. pointing to a disabled DockSpace node)
+        IM_ASSERT(window->DockNode->ID != node->ID);
+        DockNodeRemoveWindow(window->DockNode, window, 0);
+    }
+    IM_ASSERT(window->DockNode == NULL || window->DockNodeAsHost == NULL);
+    IMGUI_DEBUG_LOG_DOCKING("[docking] DockNodeAddWindow node 0x%08X window '%s'\n", node->ID, window->Name);
+
+    // If more than 2 windows appeared on the same frame leading to the creation of a new hosting window,
+    // we'll hide windows until the host window is ready. Hide the 1st window after its been output (so it is not visible for one frame).
+    // We will call DockNodeHideWindowDuringHostWindowCreation() on ourselves in Begin()
+    if (node->HostWindow == NULL && node->Windows.Size == 1 && node->Windows[0]->WasActive == false)
+        DockNodeHideWindowDuringHostWindowCreation(node->Windows[0]);
+
+    node->Windows.push_back(window);
+    node->WantHiddenTabBarUpdate = true;
+    window->DockNode = node;
+    window->DockId = node->ID;
+    window->DockIsActive = (node->Windows.Size > 1);
+    window->DockTabWantClose = false;
+
+    // When reactivating a node with one or two loose window, the window pos/size/viewport are authoritative over the node storage.
+    // In particular it is important we init the viewport from the first window so we don't create two viewports and drop one.
+    if (node->HostWindow == NULL && node->IsFloatingNode())
+    {
+        if (node->AuthorityForPos == ImGuiDataAuthority_Auto)
+            node->AuthorityForPos = ImGuiDataAuthority_Window;
+        if (node->AuthorityForSize == ImGuiDataAuthority_Auto)
+            node->AuthorityForSize = ImGuiDataAuthority_Window;
+        if (node->AuthorityForViewport == ImGuiDataAuthority_Auto)
+            node->AuthorityForViewport = ImGuiDataAuthority_Window;
+    }
+
+    // Add to tab bar if requested
+    if (add_to_tab_bar)
+    {
+        if (node->TabBar == NULL)
+        {
+            DockNodeAddTabBar(node);
+            node->TabBar->SelectedTabId = node->TabBar->NextSelectedTabId = node->SelectedTabId;
+
+            // Add existing windows
+            for (int n = 0; n < node->Windows.Size - 1; n++)
+                TabBarAddTab(node->TabBar, ImGuiTabItemFlags_None, node->Windows[n]);
+        }
+        TabBarAddTab(node->TabBar, ImGuiTabItemFlags_Unsorted, window);
+    }
+
+    DockNodeUpdateVisibleFlag(node);
+
+    // Update this without waiting for the next time we Begin() in the window, so our host window will have the proper title bar color on its first frame.
+    if (node->HostWindow)
+        UpdateWindowParentAndRootLinks(window, window->Flags | ImGuiWindowFlags_ChildWindow, node->HostWindow);
+}
+
+static void ImGui::DockNodeRemoveWindow(ImGuiDockNode* node, ImGuiWindow* window, ImGuiID save_dock_id)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(window->DockNode == node);
+    //IM_ASSERT(window->RootWindowDockTree == node->HostWindow);
+    //IM_ASSERT(window->LastFrameActive < g.FrameCount);    // We may call this from Begin()
+    IM_ASSERT(save_dock_id == 0 || save_dock_id == node->ID);
+    IMGUI_DEBUG_LOG_DOCKING("[docking] DockNodeRemoveWindow node 0x%08X window '%s'\n", node->ID, window->Name);
+
+    window->DockNode = NULL;
+    window->DockIsActive = window->DockTabWantClose = false;
+    window->DockId = save_dock_id;
+    window->Flags &= ~ImGuiWindowFlags_ChildWindow;
+    if (window->ParentWindow)
+        window->ParentWindow->DC.ChildWindows.find_erase(window);
+    UpdateWindowParentAndRootLinks(window, window->Flags, NULL); // Update immediately
+
+    if (node->HostWindow && node->HostWindow->ViewportOwned)
+    {
+        // When undocking from a user interaction this will always run in NewFrame() and have not much effect.
+        // But mid-frame, if we clear viewport we need to mark window as hidden as well.
+        window->Viewport = NULL;
+        window->ViewportId = 0;
+        window->ViewportOwned = false;
+        window->Hidden = true;
+    }
+
+    // Remove window
+    bool erased = false;
+    for (int n = 0; n < node->Windows.Size; n++)
+        if (node->Windows[n] == window)
+        {
+            node->Windows.erase(node->Windows.Data + n);
+            erased = true;
+            break;
+        }
+    if (!erased)
+        IM_ASSERT(erased);
+    if (node->VisibleWindow == window)
+        node->VisibleWindow = NULL;
+
+    // Remove tab and possibly tab bar
+    node->WantHiddenTabBarUpdate = true;
+    if (node->TabBar)
+    {
+        TabBarRemoveTab(node->TabBar, window->TabId);
+        const int tab_count_threshold_for_tab_bar = node->IsCentralNode() ? 1 : 2;
+        if (node->Windows.Size < tab_count_threshold_for_tab_bar)
+            DockNodeRemoveTabBar(node);
+    }
+
+    if (node->Windows.Size == 0 && !node->IsCentralNode() && !node->IsDockSpace() && window->DockId != node->ID)
+    {
+        // Automatic dock node delete themselves if they are not holding at least one tab
+        DockContextRemoveNode(&g, node, true);
+        return;
+    }
+
+    if (node->Windows.Size == 1 && !node->IsCentralNode() && node->HostWindow)
+    {
+        ImGuiWindow* remaining_window = node->Windows[0];
+        // Note: we used to transport viewport ownership here.
+        remaining_window->Collapsed = node->HostWindow->Collapsed;
+    }
+
+    // Update visibility immediately is required so the DockNodeUpdateRemoveInactiveChilds() processing can reflect changes up the tree
+    DockNodeUpdateVisibleFlag(node);
+}
+
+static void ImGui::DockNodeMoveChildNodes(ImGuiDockNode* dst_node, ImGuiDockNode* src_node)
+{
+    IM_ASSERT(dst_node->Windows.Size == 0);
+    dst_node->ChildNodes[0] = src_node->ChildNodes[0];
+    dst_node->ChildNodes[1] = src_node->ChildNodes[1];
+    if (dst_node->ChildNodes[0])
+        dst_node->ChildNodes[0]->ParentNode = dst_node;
+    if (dst_node->ChildNodes[1])
+        dst_node->ChildNodes[1]->ParentNode = dst_node;
+    dst_node->SplitAxis = src_node->SplitAxis;
+    dst_node->SizeRef = src_node->SizeRef;
+    src_node->ChildNodes[0] = src_node->ChildNodes[1] = NULL;
+}
+
+static void ImGui::DockNodeMoveWindows(ImGuiDockNode* dst_node, ImGuiDockNode* src_node)
+{
+    // Insert tabs in the same orders as currently ordered (node->Windows isn't ordered)
+    IM_ASSERT(src_node && dst_node && dst_node != src_node);
+    ImGuiTabBar* src_tab_bar = src_node->TabBar;
+    if (src_tab_bar != NULL)
+        IM_ASSERT(src_node->Windows.Size <= src_node->TabBar->Tabs.Size);
+
+    // If the dst_node is empty we can just move the entire tab bar (to preserve selection, scrolling, etc.)
+    bool move_tab_bar = (src_tab_bar != NULL) && (dst_node->TabBar == NULL);
+    if (move_tab_bar)
+    {
+        dst_node->TabBar = src_node->TabBar;
+        src_node->TabBar = NULL;
+    }
+
+    // Tab order is not important here, it is preserved by sorting in DockNodeUpdateTabBar().
+    for (ImGuiWindow* window : src_node->Windows)
+    {
+        window->DockNode = NULL;
+        window->DockIsActive = false;
+        DockNodeAddWindow(dst_node, window, !move_tab_bar);
+    }
+    src_node->Windows.clear();
+
+    if (!move_tab_bar && src_node->TabBar)
+    {
+        if (dst_node->TabBar)
+            dst_node->TabBar->SelectedTabId = src_node->TabBar->SelectedTabId;
+        DockNodeRemoveTabBar(src_node);
+    }
+}
+
+static void ImGui::DockNodeApplyPosSizeToWindows(ImGuiDockNode* node)
+{
+    for (ImGuiWindow* window : node->Windows)
+    {
+        SetWindowPos(window, node->Pos, ImGuiCond_Always); // We don't assign directly to Pos because it can break the calculation of SizeContents on next frame
+        SetWindowSize(window, node->Size, ImGuiCond_Always);
+    }
+}
+
+static void ImGui::DockNodeHideHostWindow(ImGuiDockNode* node)
+{
+    if (node->HostWindow)
+    {
+        if (node->HostWindow->DockNodeAsHost == node)
+            node->HostWindow->DockNodeAsHost = NULL;
+        node->HostWindow = NULL;
+    }
+
+    if (node->Windows.Size == 1)
+    {
+        node->VisibleWindow = node->Windows[0];
+        node->Windows[0]->DockIsActive = false;
+    }
+
+    if (node->TabBar)
+        DockNodeRemoveTabBar(node);
+}
+
+// Search function called once by root node in DockNodeUpdate()
+struct ImGuiDockNodeTreeInfo
+{
+    ImGuiDockNode*      CentralNode;
+    ImGuiDockNode*      FirstNodeWithWindows;
+    int                 CountNodesWithWindows;
+    //ImGuiWindowClass  WindowClassForMerges;
+
+    ImGuiDockNodeTreeInfo() { memset(this, 0, sizeof(*this)); }
+};
+
+static void DockNodeFindInfo(ImGuiDockNode* node, ImGuiDockNodeTreeInfo* info)
+{
+    if (node->Windows.Size > 0)
+    {
+        if (info->FirstNodeWithWindows == NULL)
+            info->FirstNodeWithWindows = node;
+        info->CountNodesWithWindows++;
+    }
+    if (node->IsCentralNode())
+    {
+        IM_ASSERT(info->CentralNode == NULL); // Should be only one
+        IM_ASSERT(node->IsLeafNode() && "If you get this assert: please submit .ini file + repro of actions leading to this.");
+        info->CentralNode = node;
+    }
+    if (info->CountNodesWithWindows > 1 && info->CentralNode != NULL)
+        return;
+    if (node->ChildNodes[0])
+        DockNodeFindInfo(node->ChildNodes[0], info);
+    if (node->ChildNodes[1])
+        DockNodeFindInfo(node->ChildNodes[1], info);
+}
+
+static ImGuiWindow* ImGui::DockNodeFindWindowByID(ImGuiDockNode* node, ImGuiID id)
+{
+    IM_ASSERT(id != 0);
+    for (ImGuiWindow* window : node->Windows)
+        if (window->ID == id)
+            return window;
+    return NULL;
+}
+
+// - Remove inactive windows/nodes.
+// - Update visibility flag.
+static void ImGui::DockNodeUpdateFlagsAndCollapse(ImGuiDockNode* node)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(node->ParentNode == NULL || node->ParentNode->ChildNodes[0] == node || node->ParentNode->ChildNodes[1] == node);
+
+    // Inherit most flags
+    if (node->ParentNode)
+        node->SharedFlags = node->ParentNode->SharedFlags & ImGuiDockNodeFlags_SharedFlagsInheritMask_;
+
+    // Recurse into children
+    // There is the possibility that one of our child becoming empty will delete itself and moving its sibling contents into 'node'.
+    // If 'node->ChildNode[0]' delete itself, then 'node->ChildNode[1]->Windows' will be moved into 'node'
+    // If 'node->ChildNode[1]' delete itself, then 'node->ChildNode[0]->Windows' will be moved into 'node' and the "remove inactive windows" loop will have run twice on those windows (harmless)
+    node->HasCentralNodeChild = false;
+    if (node->ChildNodes[0])
+        DockNodeUpdateFlagsAndCollapse(node->ChildNodes[0]);
+    if (node->ChildNodes[1])
+        DockNodeUpdateFlagsAndCollapse(node->ChildNodes[1]);
+
+    // Remove inactive windows, collapse nodes
+    // Merge node flags overrides stored in windows
+    node->LocalFlagsInWindows = ImGuiDockNodeFlags_None;
+    for (int window_n = 0; window_n < node->Windows.Size; window_n++)
+    {
+        ImGuiWindow* window = node->Windows[window_n];
+        IM_ASSERT(window->DockNode == node);
+
+        bool node_was_active = (node->LastFrameActive + 1 == g.FrameCount);
+        bool remove = false;
+        remove |= node_was_active && (window->LastFrameActive + 1 < g.FrameCount);
+        remove |= node_was_active && (node->WantCloseAll || node->WantCloseTabId == window->TabId) && window->HasCloseButton && !(window->Flags & ImGuiWindowFlags_UnsavedDocument);  // Submit all _expected_ closure from last frame
+        remove |= (window->DockTabWantClose);
+        if (remove)
+        {
+            window->DockTabWantClose = false;
+            if (node->Windows.Size == 1 && !node->IsCentralNode())
+            {
+                DockNodeHideHostWindow(node);
+                node->State = ImGuiDockNodeState_HostWindowHiddenBecauseSingleWindow;
+                DockNodeRemoveWindow(node, window, node->ID); // Will delete the node so it'll be invalid on return
+                return;
+            }
+            DockNodeRemoveWindow(node, window, node->ID);
+            window_n--;
+            continue;
+        }
+
+        // FIXME-DOCKING: Missing policies for conflict resolution, hence the "Experimental" tag on this.
+        //node->LocalFlagsInWindow &= ~window->WindowClass.DockNodeFlagsOverrideClear;
+        node->LocalFlagsInWindows |= window->WindowClass.DockNodeFlagsOverrideSet;
+    }
+    node->UpdateMergedFlags();
+
+    // Auto-hide tab bar option
+    ImGuiDockNodeFlags node_flags = node->MergedFlags;
+    if (node->WantHiddenTabBarUpdate && node->Windows.Size == 1 && (node_flags & ImGuiDockNodeFlags_AutoHideTabBar) && !node->IsHiddenTabBar())
+        node->WantHiddenTabBarToggle = true;
+    node->WantHiddenTabBarUpdate = false;
+
+    // Cancel toggling if we know our tab bar is enforced to be hidden at all times
+    if (node->WantHiddenTabBarToggle && node->VisibleWindow && (node->VisibleWindow->WindowClass.DockNodeFlagsOverrideSet & ImGuiDockNodeFlags_HiddenTabBar))
+        node->WantHiddenTabBarToggle = false;
+
+    // Apply toggles at a single point of the frame (here!)
+    if (node->Windows.Size > 1)
+        node->SetLocalFlags(node->LocalFlags & ~ImGuiDockNodeFlags_HiddenTabBar);
+    else if (node->WantHiddenTabBarToggle)
+        node->SetLocalFlags(node->LocalFlags ^ ImGuiDockNodeFlags_HiddenTabBar);
+    node->WantHiddenTabBarToggle = false;
+
+    DockNodeUpdateVisibleFlag(node);
+}
+
+// This is rarely called as DockNodeUpdateForRootNode() generally does it most frames.
+static void ImGui::DockNodeUpdateHasCentralNodeChild(ImGuiDockNode* node)
+{
+    node->HasCentralNodeChild = false;
+    if (node->ChildNodes[0])
+        DockNodeUpdateHasCentralNodeChild(node->ChildNodes[0]);
+    if (node->ChildNodes[1])
+        DockNodeUpdateHasCentralNodeChild(node->ChildNodes[1]);
+    if (node->IsRootNode())
+    {
+        ImGuiDockNode* mark_node = node->CentralNode;
+        while (mark_node)
+        {
+            mark_node->HasCentralNodeChild = true;
+            mark_node = mark_node->ParentNode;
+        }
+    }
+}
+
+static void ImGui::DockNodeUpdateVisibleFlag(ImGuiDockNode* node)
+{
+    // Update visibility flag
+    bool is_visible = (node->ParentNode == NULL) ? node->IsDockSpace() : node->IsCentralNode();
+    is_visible |= (node->Windows.Size > 0);
+    is_visible |= (node->ChildNodes[0] && node->ChildNodes[0]->IsVisible);
+    is_visible |= (node->ChildNodes[1] && node->ChildNodes[1]->IsVisible);
+    node->IsVisible = is_visible;
+}
+
+static void ImGui::DockNodeStartMouseMovingWindow(ImGuiDockNode* node, ImGuiWindow* window)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(node->WantMouseMove == true);
+    StartMouseMovingWindow(window);
+    g.ActiveIdClickOffset = g.IO.MouseClickedPos[0] - node->Pos;
+    g.MovingWindow = window; // If we are docked into a non moveable root window, StartMouseMovingWindow() won't set g.MovingWindow. Override that decision.
+    node->WantMouseMove = false;
+}
+
+// Update CentralNode, OnlyNodeWithWindows, LastFocusedNodeID. Copy window class.
+static void ImGui::DockNodeUpdateForRootNode(ImGuiDockNode* node)
+{
+    DockNodeUpdateFlagsAndCollapse(node);
+
+    // - Setup central node pointers
+    // - Find if there's only a single visible window in the hierarchy (in which case we need to display a regular title bar -> FIXME-DOCK: that last part is not done yet!)
+    // Cannot merge this with DockNodeUpdateFlagsAndCollapse() because FirstNodeWithWindows is found after window removal and child collapsing
+    ImGuiDockNodeTreeInfo info;
+    DockNodeFindInfo(node, &info);
+    node->CentralNode = info.CentralNode;
+    node->OnlyNodeWithWindows = (info.CountNodesWithWindows == 1) ? info.FirstNodeWithWindows : NULL;
+    node->CountNodeWithWindows = info.CountNodesWithWindows;
+    if (node->LastFocusedNodeId == 0 && info.FirstNodeWithWindows != NULL)
+        node->LastFocusedNodeId = info.FirstNodeWithWindows->ID;
+
+    // Copy the window class from of our first window so it can be used for proper dock filtering.
+    // When node has mixed windows, prioritize the class with the most constraint (DockingAllowUnclassed = false) as the reference to copy.
+    // FIXME-DOCK: We don't recurse properly, this code could be reworked to work from DockNodeUpdateScanRec.
+    if (ImGuiDockNode* first_node_with_windows = info.FirstNodeWithWindows)
+    {
+        node->WindowClass = first_node_with_windows->Windows[0]->WindowClass;
+        for (int n = 1; n < first_node_with_windows->Windows.Size; n++)
+            if (first_node_with_windows->Windows[n]->WindowClass.DockingAllowUnclassed == false)
+            {
+                node->WindowClass = first_node_with_windows->Windows[n]->WindowClass;
+                break;
+            }
+    }
+
+    ImGuiDockNode* mark_node = node->CentralNode;
+    while (mark_node)
+    {
+        mark_node->HasCentralNodeChild = true;
+        mark_node = mark_node->ParentNode;
+    }
+}
+
+static void DockNodeSetupHostWindow(ImGuiDockNode* node, ImGuiWindow* host_window)
+{
+    // Remove ourselves from any previous different host window
+    // This can happen if a user mistakenly does (see #4295 for details):
+    //  - N+0: DockBuilderAddNode(id, 0)    // missing ImGuiDockNodeFlags_DockSpace
+    //  - N+1: NewFrame()                   // will create floating host window for that node
+    //  - N+1: DockSpace(id)                // requalify node as dockspace, moving host window
+    if (node->HostWindow && node->HostWindow != host_window && node->HostWindow->DockNodeAsHost == node)
+        node->HostWindow->DockNodeAsHost = NULL;
+
+    host_window->DockNodeAsHost = node;
+    node->HostWindow = host_window;
+}
+
+static void ImGui::DockNodeUpdate(ImGuiDockNode* node)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(node->LastFrameActive != g.FrameCount);
+    node->LastFrameAlive = g.FrameCount;
+    node->IsBgDrawnThisFrame = false;
+
+    node->CentralNode = node->OnlyNodeWithWindows = NULL;
+    if (node->IsRootNode())
+        DockNodeUpdateForRootNode(node);
+
+    // Remove tab bar if not needed
+    if (node->TabBar && node->IsNoTabBar())
+        DockNodeRemoveTabBar(node);
+
+    // Early out for hidden root dock nodes (when all DockId references are in inactive windows, or there is only 1 floating window holding on the DockId)
+    bool want_to_hide_host_window = false;
+    if (node->IsFloatingNode())
+    {
+        if (node->Windows.Size <= 1 && node->IsLeafNode())
+            if (!g.IO.ConfigDockingAlwaysTabBar && (node->Windows.Size == 0 || !node->Windows[0]->WindowClass.DockingAlwaysTabBar))
+                want_to_hide_host_window = true;
+        if (node->CountNodeWithWindows == 0)
+            want_to_hide_host_window = true;
+    }
+    if (want_to_hide_host_window)
+    {
+        if (node->Windows.Size == 1)
+        {
+            // Floating window pos/size is authoritative
+            ImGuiWindow* single_window = node->Windows[0];
+            node->Pos = single_window->Pos;
+            node->Size = single_window->SizeFull;
+            node->AuthorityForPos = node->AuthorityForSize = node->AuthorityForViewport = ImGuiDataAuthority_Window;
+
+            // Transfer focus immediately so when we revert to a regular window it is immediately selected
+            if (node->HostWindow && g.NavWindow == node->HostWindow)
+                FocusWindow(single_window);
+            if (node->HostWindow)
+            {
+                IMGUI_DEBUG_LOG_VIEWPORT("[viewport] Node %08X transfer Viewport %08X->%08X to Window '%s'\n", node->ID, node->HostWindow->Viewport->ID, single_window->ID, single_window->Name);
+                single_window->Viewport = node->HostWindow->Viewport;
+                single_window->ViewportId = node->HostWindow->ViewportId;
+                if (node->HostWindow->ViewportOwned)
+                {
+                    single_window->Viewport->ID = single_window->ID;
+                    single_window->Viewport->Window = single_window;
+                    single_window->ViewportOwned = true;
+                }
+            }
+            node->RefViewportId = single_window->ViewportId;
+        }
+
+        DockNodeHideHostWindow(node);
+        node->State = ImGuiDockNodeState_HostWindowHiddenBecauseSingleWindow;
+        node->WantCloseAll = false;
+        node->WantCloseTabId = 0;
+        node->HasCloseButton = node->HasWindowMenuButton = false;
+        node->LastFrameActive = g.FrameCount;
+
+        if (node->WantMouseMove && node->Windows.Size == 1)
+            DockNodeStartMouseMovingWindow(node, node->Windows[0]);
+        return;
+    }
+
+    // In some circumstance we will defer creating the host window (so everything will be kept hidden),
+    // while the expected visible window is resizing itself.
+    // This is important for first-time (no ini settings restored) single window when io.ConfigDockingAlwaysTabBar is enabled,
+    // otherwise the node ends up using the minimum window size. Effectively those windows will take an extra frame to show up:
+    //   N+0: Begin(): window created (with no known size), node is created
+    //   N+1: DockNodeUpdate(): node skip creating host window / Begin(): window size applied, not visible
+    //   N+2: DockNodeUpdate(): node can create host window / Begin(): window becomes visible
+    // We could remove this frame if we could reliably calculate the expected window size during node update, before the Begin() code.
+    // It would require a generalization of CalcWindowExpectedSize(), probably extracting code away from Begin().
+    // In reality it isn't very important as user quickly ends up with size data in .ini file.
+    if (node->IsVisible && node->HostWindow == NULL && node->IsFloatingNode() && node->IsLeafNode())
+    {
+        IM_ASSERT(node->Windows.Size > 0);
+        ImGuiWindow* ref_window = NULL;
+        if (node->SelectedTabId != 0) // Note that we prune single-window-node settings on .ini loading, so this is generally 0 for them!
+            ref_window = DockNodeFindWindowByID(node, node->SelectedTabId);
+        if (ref_window == NULL)
+            ref_window = node->Windows[0];
+        if (ref_window->AutoFitFramesX > 0 || ref_window->AutoFitFramesY > 0)
+        {
+            node->State = ImGuiDockNodeState_HostWindowHiddenBecauseWindowsAreResizing;
+            return;
+        }
+    }
+
+    const ImGuiDockNodeFlags node_flags = node->MergedFlags;
+
+    // Decide if the node will have a close button and a window menu button
+    node->HasWindowMenuButton = (node->Windows.Size > 0) && (node_flags & ImGuiDockNodeFlags_NoWindowMenuButton) == 0;
+    node->HasCloseButton = false;
+    for (ImGuiWindow* window : node->Windows)
+    {
+        // FIXME-DOCK: Setting DockIsActive here means that for single active window in a leaf node, DockIsActive will be cleared until the next Begin() call.
+        node->HasCloseButton |= window->HasCloseButton;
+        window->DockIsActive = (node->Windows.Size > 1);
+    }
+    if (node_flags & ImGuiDockNodeFlags_NoCloseButton)
+        node->HasCloseButton = false;
+
+    // Bind or create host window
+    ImGuiWindow* host_window = NULL;
+    bool beginned_into_host_window = false;
+    if (node->IsDockSpace())
+    {
+        // [Explicit root dockspace node]
+        IM_ASSERT(node->HostWindow);
+        host_window = node->HostWindow;
+    }
+    else
+    {
+        // [Automatic root or child nodes]
+        if (node->IsRootNode() && node->IsVisible)
+        {
+            ImGuiWindow* ref_window = (node->Windows.Size > 0) ? node->Windows[0] : NULL;
+
+            // Sync Pos
+            if (node->AuthorityForPos == ImGuiDataAuthority_Window && ref_window)
+                SetNextWindowPos(ref_window->Pos);
+            else if (node->AuthorityForPos == ImGuiDataAuthority_DockNode)
+                SetNextWindowPos(node->Pos);
+
+            // Sync Size
+            if (node->AuthorityForSize == ImGuiDataAuthority_Window && ref_window)
+                SetNextWindowSize(ref_window->SizeFull);
+            else if (node->AuthorityForSize == ImGuiDataAuthority_DockNode)
+                SetNextWindowSize(node->Size);
+
+            // Sync Collapsed
+            if (node->AuthorityForSize == ImGuiDataAuthority_Window && ref_window)
+                SetNextWindowCollapsed(ref_window->Collapsed);
+
+            // Sync Viewport
+            if (node->AuthorityForViewport == ImGuiDataAuthority_Window && ref_window)
+                SetNextWindowViewport(ref_window->ViewportId);
+            else if (node->AuthorityForViewport == ImGuiDataAuthority_Window && node->RefViewportId != 0)
+                SetNextWindowViewport(node->RefViewportId);
+
+            SetNextWindowClass(&node->WindowClass);
+
+            // Begin into the host window
+            char window_label[20];
+            DockNodeGetHostWindowTitle(node, window_label, IM_ARRAYSIZE(window_label));
+            ImGuiWindowFlags window_flags = ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoScrollWithMouse | ImGuiWindowFlags_DockNodeHost;
+            window_flags |= ImGuiWindowFlags_NoFocusOnAppearing;
+            window_flags |= ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_NoNavFocus | ImGuiWindowFlags_NoCollapse;
+            window_flags |= ImGuiWindowFlags_NoTitleBar;
+
+            SetNextWindowBgAlpha(0.0f); // Don't set ImGuiWindowFlags_NoBackground because it disables borders
+            PushStyleVar(ImGuiStyleVar_WindowPadding, ImVec2(0, 0));
+            Begin(window_label, NULL, window_flags);
+            PopStyleVar();
+            beginned_into_host_window = true;
+
+            host_window = g.CurrentWindow;
+            DockNodeSetupHostWindow(node, host_window);
+            host_window->DC.CursorPos = host_window->Pos;
+            node->Pos = host_window->Pos;
+            node->Size = host_window->Size;
+
+            // We set ImGuiWindowFlags_NoFocusOnAppearing because we don't want the host window to take full focus (e.g. steal NavWindow)
+            // But we still it bring it to the front of display. There's no way to choose this precise behavior via window flags.
+            // One simple case to ponder if: window A has a toggle to create windows B/C/D. Dock B/C/D together, clear the toggle and enable it again.
+            // When reappearing B/C/D will request focus and be moved to the top of the display pile, but they are not linked to the dock host window
+            // during the frame they appear. The dock host window would keep its old display order, and the sorting in EndFrame would move B/C/D back
+            // after the dock host window, losing their top-most status.
+            if (node->HostWindow->Appearing)
+                BringWindowToDisplayFront(node->HostWindow);
+
+            node->AuthorityForPos = node->AuthorityForSize = node->AuthorityForViewport = ImGuiDataAuthority_Auto;
+        }
+        else if (node->ParentNode)
+        {
+            node->HostWindow = host_window = node->ParentNode->HostWindow;
+            node->AuthorityForPos = node->AuthorityForSize = node->AuthorityForViewport = ImGuiDataAuthority_Auto;
+        }
+        if (node->WantMouseMove && node->HostWindow)
+            DockNodeStartMouseMovingWindow(node, node->HostWindow);
+    }
+    node->RefViewportId = 0; // Clear when we have a host window
+
+    // Update focused node (the one whose title bar is highlight) within a node tree
+    if (node->IsSplitNode())
+        IM_ASSERT(node->TabBar == NULL);
+    if (node->IsRootNode())
+        if (ImGuiWindow* p_window = g.NavWindow ? g.NavWindow->RootWindow : NULL)
+            while (p_window != NULL && p_window->DockNode != NULL)
+            {
+                ImGuiDockNode* p_node = DockNodeGetRootNode(p_window->DockNode);
+                if (p_node == node)
+                {
+                    node->LastFocusedNodeId = p_window->DockNode->ID; // Note: not using root node ID!
+                    break;
+                }
+                p_window = p_node->HostWindow ? p_node->HostWindow->RootWindow : NULL;
+            }
+
+    // Register a hit-test hole in the window unless we are currently dragging a window that is compatible with our dockspace
+    ImGuiDockNode* central_node = node->CentralNode;
+    const bool central_node_hole = node->IsRootNode() && host_window && (node_flags & ImGuiDockNodeFlags_PassthruCentralNode) != 0 && central_node != NULL && central_node->IsEmpty();
+    bool central_node_hole_register_hit_test_hole = central_node_hole;
+    if (central_node_hole)
+        if (const ImGuiPayload* payload = ImGui::GetDragDropPayload())
+            if (payload->IsDataType(IMGUI_PAYLOAD_TYPE_WINDOW) && DockNodeIsDropAllowed(host_window, *(ImGuiWindow**)payload->Data))
+                central_node_hole_register_hit_test_hole = false;
+    if (central_node_hole_register_hit_test_hole)
+    {
+        // We add a little padding to match the "resize from edges" behavior and allow grabbing the splitter easily.
+        // (But we only add it if there's something else on the other side of the hole, otherwise for e.g. fullscreen
+        // covering passthru node we'd have a gap on the edge not covered by the hole)
+        IM_ASSERT(node->IsDockSpace()); // We cannot pass this flag without the DockSpace() api. Testing this because we also setup the hole in host_window->ParentNode
+        ImGuiDockNode* root_node = DockNodeGetRootNode(central_node);
+        ImRect root_rect(root_node->Pos, root_node->Pos + root_node->Size);
+        ImRect hole_rect(central_node->Pos, central_node->Pos + central_node->Size);
+        if (hole_rect.Min.x > root_rect.Min.x) { hole_rect.Min.x += WINDOWS_HOVER_PADDING; }
+        if (hole_rect.Max.x < root_rect.Max.x) { hole_rect.Max.x -= WINDOWS_HOVER_PADDING; }
+        if (hole_rect.Min.y > root_rect.Min.y) { hole_rect.Min.y += WINDOWS_HOVER_PADDING; }
+        if (hole_rect.Max.y < root_rect.Max.y) { hole_rect.Max.y -= WINDOWS_HOVER_PADDING; }
+        //GetForegroundDrawList()->AddRect(hole_rect.Min, hole_rect.Max, IM_COL32(255, 0, 0, 255));
+        if (central_node_hole && !hole_rect.IsInverted())
+        {
+            SetWindowHitTestHole(host_window, hole_rect.Min, hole_rect.Max - hole_rect.Min);
+            if (host_window->ParentWindow)
+                SetWindowHitTestHole(host_window->ParentWindow, hole_rect.Min, hole_rect.Max - hole_rect.Min);
+        }
+    }
+
+    // Update position/size, process and draw resizing splitters
+    if (node->IsRootNode() && host_window)
+    {
+        DockNodeTreeUpdatePosSize(node, host_window->Pos, host_window->Size);
+        PushStyleColor(ImGuiCol_Separator, g.Style.Colors[ImGuiCol_Border]);
+        PushStyleColor(ImGuiCol_SeparatorActive, g.Style.Colors[ImGuiCol_ResizeGripActive]);
+        PushStyleColor(ImGuiCol_SeparatorHovered, g.Style.Colors[ImGuiCol_ResizeGripHovered]);
+        DockNodeTreeUpdateSplitter(node);
+        PopStyleColor(3);
+    }
+
+    // Draw empty node background (currently can only be the Central Node)
+    if (host_window && node->IsEmpty() && node->IsVisible)
+    {
+        host_window->DrawList->ChannelsSetCurrent(DOCKING_HOST_DRAW_CHANNEL_BG);
+        node->LastBgColor = (node_flags & ImGuiDockNodeFlags_PassthruCentralNode) ? 0 : GetColorU32(ImGuiCol_DockingEmptyBg);
+        if (node->LastBgColor != 0)
+            host_window->DrawList->AddRectFilled(node->Pos, node->Pos + node->Size, node->LastBgColor);
+        node->IsBgDrawnThisFrame = true;
+    }
+
+    // Draw whole dockspace background if ImGuiDockNodeFlags_PassthruCentralNode if set.
+    // We need to draw a background at the root level if requested by ImGuiDockNodeFlags_PassthruCentralNode, but we will only know the correct pos/size
+    // _after_ processing the resizing splitters. So we are using the DrawList channel splitting facility to submit drawing primitives out of order!
+    const bool render_dockspace_bg = node->IsRootNode() && host_window && (node_flags & ImGuiDockNodeFlags_PassthruCentralNode) != 0;
+    if (render_dockspace_bg && node->IsVisible)
+    {
+        host_window->DrawList->ChannelsSetCurrent(DOCKING_HOST_DRAW_CHANNEL_BG);
+        if (central_node_hole)
+            RenderRectFilledWithHole(host_window->DrawList, node->Rect(), central_node->Rect(), GetColorU32(ImGuiCol_WindowBg), 0.0f);
+        else
+            host_window->DrawList->AddRectFilled(node->Pos, node->Pos + node->Size, GetColorU32(ImGuiCol_WindowBg), 0.0f);
+    }
+
+    // Draw and populate Tab Bar
+    if (host_window)
+        host_window->DrawList->ChannelsSetCurrent(DOCKING_HOST_DRAW_CHANNEL_FG);
+    if (host_window && node->Windows.Size > 0)
+    {
+        DockNodeUpdateTabBar(node, host_window);
+    }
+    else
+    {
+        node->WantCloseAll = false;
+        node->WantCloseTabId = 0;
+        node->IsFocused = false;
+    }
+    if (node->TabBar && node->TabBar->SelectedTabId)
+        node->SelectedTabId = node->TabBar->SelectedTabId;
+    else if (node->Windows.Size > 0)
+        node->SelectedTabId = node->Windows[0]->TabId;
+
+    // Draw payload drop target
+    if (host_window && node->IsVisible)
+        if (node->IsRootNode() && (g.MovingWindow == NULL || g.MovingWindow->RootWindowDockTree != host_window))
+            BeginDockableDragDropTarget(host_window);
+
+    // We update this after DockNodeUpdateTabBar()
+    node->LastFrameActive = g.FrameCount;
+
+    // Recurse into children
+    // FIXME-DOCK FIXME-OPT: Should not need to recurse into children
+    if (host_window)
+    {
+        if (node->ChildNodes[0])
+            DockNodeUpdate(node->ChildNodes[0]);
+        if (node->ChildNodes[1])
+            DockNodeUpdate(node->ChildNodes[1]);
+
+        // Render outer borders last (after the tab bar)
+        if (node->IsRootNode())
+            RenderWindowOuterBorders(host_window);
+    }
+
+    // End host window
+    if (beginned_into_host_window) //-V1020
+        End();
+}
+
+// Compare TabItem nodes given the last known DockOrder (will persist in .ini file as hint), used to sort tabs when multiple tabs are added on the same frame.
+static int IMGUI_CDECL TabItemComparerByDockOrder(const void* lhs, const void* rhs)
+{
+    ImGuiWindow* a = ((const ImGuiTabItem*)lhs)->Window;
+    ImGuiWindow* b = ((const ImGuiTabItem*)rhs)->Window;
+    if (int d = ((a->DockOrder == -1) ? INT_MAX : a->DockOrder) - ((b->DockOrder == -1) ? INT_MAX : b->DockOrder))
+        return d;
+    return (a->BeginOrderWithinContext - b->BeginOrderWithinContext);
+}
+
+// Default handler for g.DockNodeWindowMenuHandler(): display the list of windows for a given dock-node.
+// This is exceptionally stored in a function pointer to also user applications to tweak this menu (undocumented)
+// Custom overrides may want to decorate, group, sort entries.
+// Please note those are internal structures: if you copy this expect occasional breakage.
+// (if you don't need to modify the "Tabs.Size == 1" behavior/path it is recommend you call this function in your handler)
+void ImGui::DockNodeWindowMenuHandler_Default(ImGuiContext* ctx, ImGuiDockNode* node, ImGuiTabBar* tab_bar)
+{
+    IM_UNUSED(ctx);
+    if (tab_bar->Tabs.Size == 1)
+    {
+        // "Hide tab bar" option. Being one of our rare user-facing string we pull it from a table.
+        if (MenuItem(LocalizeGetMsg(ImGuiLocKey_DockingHideTabBar), NULL, node->IsHiddenTabBar()))
+            node->WantHiddenTabBarToggle = true;
+    }
+    else
+    {
+        // Display a selectable list of windows in this docking node
+        for (int tab_n = 0; tab_n < tab_bar->Tabs.Size; tab_n++)
+        {
+            ImGuiTabItem* tab = &tab_bar->Tabs[tab_n];
+            if (tab->Flags & ImGuiTabItemFlags_Button)
+                continue;
+            if (Selectable(TabBarGetTabName(tab_bar, tab), tab->ID == tab_bar->SelectedTabId))
+                TabBarQueueFocus(tab_bar, tab);
+            SameLine();
+            Text("   ");
+        }
+    }
+}
+
+static void ImGui::DockNodeWindowMenuUpdate(ImGuiDockNode* node, ImGuiTabBar* tab_bar)
+{
+    // Try to position the menu so it is more likely to stays within the same viewport
+    ImGuiContext& g = *GImGui;
+    if (g.Style.WindowMenuButtonPosition == ImGuiDir_Left)
+        SetNextWindowPos(ImVec2(node->Pos.x, node->Pos.y + GetFrameHeight()), ImGuiCond_Always, ImVec2(0.0f, 0.0f));
+    else
+        SetNextWindowPos(ImVec2(node->Pos.x + node->Size.x, node->Pos.y + GetFrameHeight()), ImGuiCond_Always, ImVec2(1.0f, 0.0f));
+    if (BeginPopup("#WindowMenu"))
+    {
+        node->IsFocused = true;
+        g.DockNodeWindowMenuHandler(&g, node, tab_bar);
+        EndPopup();
+    }
+}
+
+// User helper to append/amend into a dock node tab bar. Most commonly used to add e.g. a "+" button.
+bool ImGui::DockNodeBeginAmendTabBar(ImGuiDockNode* node)
+{
+    if (node->TabBar == NULL || node->HostWindow == NULL)
+        return false;
+    if (node->MergedFlags & ImGuiDockNodeFlags_KeepAliveOnly)
+        return false;
+    if (node->TabBar->ID == 0)
+        return false;
+    Begin(node->HostWindow->Name);
+    PushOverrideID(node->ID);
+    bool ret = BeginTabBarEx(node->TabBar, node->TabBar->BarRect, node->TabBar->Flags);
+    IM_UNUSED(ret);
+    IM_ASSERT(ret);
+    return true;
+}
+
+void ImGui::DockNodeEndAmendTabBar()
+{
+    EndTabBar();
+    PopID();
+    End();
+}
+
+static bool IsDockNodeTitleBarHighlighted(ImGuiDockNode* node, ImGuiDockNode* root_node)
+{
+    // CTRL+Tab highlight (only highlighting leaf node, not whole hierarchy)
+    ImGuiContext& g = *GImGui;
+    if (g.NavWindowingTarget)
+        return (g.NavWindowingTarget->DockNode == node);
+
+    // FIXME-DOCKING: May want alternative to treat central node void differently? e.g. if (g.NavWindow == host_window)
+    if (g.NavWindow && root_node->LastFocusedNodeId == node->ID)
+    {
+        // FIXME: This could all be backed in RootWindowForTitleBarHighlight? Probably need to reorganize for both dock nodes + other RootWindowForTitleBarHighlight users (not-node)
+        ImGuiWindow* parent_window = g.NavWindow->RootWindow;
+        while (parent_window->Flags & ImGuiWindowFlags_ChildMenu)
+            parent_window = parent_window->ParentWindow->RootWindow;
+        ImGuiDockNode* start_parent_node = parent_window->DockNodeAsHost ? parent_window->DockNodeAsHost : parent_window->DockNode;
+        for (ImGuiDockNode* parent_node = start_parent_node; parent_node != NULL; parent_node = parent_node->HostWindow ? parent_node->HostWindow->RootWindow->DockNode : NULL)
+            if ((parent_node = ImGui::DockNodeGetRootNode(parent_node)) == root_node)
+                return true;
+    }
+    return false;
+}
+
+// Submit the tab bar corresponding to a dock node and various housekeeping details.
+static void ImGui::DockNodeUpdateTabBar(ImGuiDockNode* node, ImGuiWindow* host_window)
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiStyle& style = g.Style;
+
+    const bool node_was_active = (node->LastFrameActive + 1 == g.FrameCount);
+    const bool closed_all = node->WantCloseAll && node_was_active;
+    const ImGuiID closed_one = node->WantCloseTabId && node_was_active;
+    node->WantCloseAll = false;
+    node->WantCloseTabId = 0;
+
+    // Decide if we should use a focused title bar color
+    bool is_focused = false;
+    ImGuiDockNode* root_node = DockNodeGetRootNode(node);
+    if (IsDockNodeTitleBarHighlighted(node, root_node))
+        is_focused = true;
+
+    // Hidden tab bar will show a triangle on the upper-left (in Begin)
+    if (node->IsHiddenTabBar() || node->IsNoTabBar())
+    {
+        node->VisibleWindow = (node->Windows.Size > 0) ? node->Windows[0] : NULL;
+        node->IsFocused = is_focused;
+        if (is_focused)
+            node->LastFrameFocused = g.FrameCount;
+        if (node->VisibleWindow)
+        {
+            // Notify root of visible window (used to display title in OS task bar)
+            if (is_focused || root_node->VisibleWindow == NULL)
+                root_node->VisibleWindow = node->VisibleWindow;
+            if (node->TabBar)
+                node->TabBar->VisibleTabId = node->VisibleWindow->TabId;
+        }
+        return;
+    }
+
+    // Move ourselves to the Menu layer (so we can be accessed by tapping Alt) + undo SkipItems flag in order to draw over the title bar even if the window is collapsed
+    bool backup_skip_item = host_window->SkipItems;
+    if (!node->IsDockSpace())
+    {
+        host_window->SkipItems = false;
+        host_window->DC.NavLayerCurrent = ImGuiNavLayer_Menu;
+    }
+
+    // Use PushOverrideID() instead of PushID() to use the node id _without_ the host window ID.
+    // This is to facilitate computing those ID from the outside, and will affect more or less only the ID of the collapse button, popup and tabs,
+    // as docked windows themselves will override the stack with their own root ID.
+    PushOverrideID(node->ID);
+    ImGuiTabBar* tab_bar = node->TabBar;
+    bool tab_bar_is_recreated = (tab_bar == NULL); // Tab bar are automatically destroyed when a node gets hidden
+    if (tab_bar == NULL)
+    {
+        DockNodeAddTabBar(node);
+        tab_bar = node->TabBar;
+    }
+
+    ImGuiID focus_tab_id = 0;
+    node->IsFocused = is_focused;
+
+    const ImGuiDockNodeFlags node_flags = node->MergedFlags;
+    const bool has_window_menu_button = (node_flags & ImGuiDockNodeFlags_NoWindowMenuButton) == 0 && (style.WindowMenuButtonPosition != ImGuiDir_None);
+
+    // In a dock node, the Collapse Button turns into the Window Menu button.
+    // FIXME-DOCK FIXME-OPT: Could we recycle popups id across multiple dock nodes?
+    if (has_window_menu_button && IsPopupOpen("#WindowMenu"))
+    {
+        ImGuiID next_selected_tab_id = tab_bar->NextSelectedTabId;
+        DockNodeWindowMenuUpdate(node, tab_bar);
+        if (tab_bar->NextSelectedTabId != 0 && tab_bar->NextSelectedTabId != next_selected_tab_id)
+            focus_tab_id = tab_bar->NextSelectedTabId;
+        is_focused |= node->IsFocused;
+    }
+
+    // Layout
+    ImRect title_bar_rect, tab_bar_rect;
+    ImVec2 window_menu_button_pos;
+    ImVec2 close_button_pos;
+    DockNodeCalcTabBarLayout(node, &title_bar_rect, &tab_bar_rect, &window_menu_button_pos, &close_button_pos);
+
+    // Submit new tabs, they will be added as Unsorted and sorted below based on relative DockOrder value.
+    const int tabs_count_old = tab_bar->Tabs.Size;
+    for (int window_n = 0; window_n < node->Windows.Size; window_n++)
+    {
+        ImGuiWindow* window = node->Windows[window_n];
+        if (TabBarFindTabByID(tab_bar, window->TabId) == NULL)
+            TabBarAddTab(tab_bar, ImGuiTabItemFlags_Unsorted, window);
+    }
+
+    // Title bar
+    if (is_focused)
+        node->LastFrameFocused = g.FrameCount;
+    ImU32 title_bar_col = GetColorU32(host_window->Collapsed ? ImGuiCol_TitleBgCollapsed : is_focused ? ImGuiCol_TitleBgActive : ImGuiCol_TitleBg);
+    ImDrawFlags rounding_flags = CalcRoundingFlagsForRectInRect(title_bar_rect, host_window->Rect(), g.Style.DockingSeparatorSize);
+    host_window->DrawList->AddRectFilled(title_bar_rect.Min, title_bar_rect.Max, title_bar_col, host_window->WindowRounding, rounding_flags);
+
+    // Docking/Collapse button
+    if (has_window_menu_button)
+    {
+        if (CollapseButton(host_window->GetID("#COLLAPSE"), window_menu_button_pos, node)) // == DockNodeGetWindowMenuButtonId(node)
+            OpenPopup("#WindowMenu");
+        if (IsItemActive())
+            focus_tab_id = tab_bar->SelectedTabId;
+        if (IsItemHovered(ImGuiHoveredFlags_ForTooltip | ImGuiHoveredFlags_DelayNormal) && g.HoveredIdTimer > 0.5f)
+            SetTooltip("%s", LocalizeGetMsg(ImGuiLocKey_DockingDragToUndockOrMoveNode));
+    }
+
+    // If multiple tabs are appearing on the same frame, sort them based on their persistent DockOrder value
+    int tabs_unsorted_start = tab_bar->Tabs.Size;
+    for (int tab_n = tab_bar->Tabs.Size - 1; tab_n >= 0 && (tab_bar->Tabs[tab_n].Flags & ImGuiTabItemFlags_Unsorted); tab_n--)
+    {
+        // FIXME-DOCK: Consider only clearing the flag after the tab has been alive for a few consecutive frames, allowing late comers to not break sorting?
+        tab_bar->Tabs[tab_n].Flags &= ~ImGuiTabItemFlags_Unsorted;
+        tabs_unsorted_start = tab_n;
+    }
+    if (tab_bar->Tabs.Size > tabs_unsorted_start)
+    {
+        IMGUI_DEBUG_LOG_DOCKING("[docking] In node 0x%08X: %d new appearing tabs:%s\n", node->ID, tab_bar->Tabs.Size - tabs_unsorted_start, (tab_bar->Tabs.Size > tabs_unsorted_start + 1) ? " (will sort)" : "");
+        for (int tab_n = tabs_unsorted_start; tab_n < tab_bar->Tabs.Size; tab_n++)
+        {
+            ImGuiTabItem* tab = &tab_bar->Tabs[tab_n];
+            IMGUI_DEBUG_LOG_DOCKING("[docking] - Tab 0x%08X '%s' Order %d\n", tab->ID, TabBarGetTabName(tab_bar, tab), tab->Window ? tab->Window->DockOrder : -1);
+        }
+        IMGUI_DEBUG_LOG_DOCKING("[docking] SelectedTabId = 0x%08X, NavWindow->TabId = 0x%08X\n", node->SelectedTabId, g.NavWindow ? g.NavWindow->TabId : -1);
+        if (tab_bar->Tabs.Size > tabs_unsorted_start + 1)
+            ImQsort(tab_bar->Tabs.Data + tabs_unsorted_start, tab_bar->Tabs.Size - tabs_unsorted_start, sizeof(ImGuiTabItem), TabItemComparerByDockOrder);
+    }
+
+    // Apply NavWindow focus back to the tab bar
+    if (g.NavWindow && g.NavWindow->RootWindow->DockNode == node)
+        tab_bar->SelectedTabId = g.NavWindow->RootWindow->TabId;
+
+    // Selected newly added tabs, or persistent tab ID if the tab bar was just recreated
+    if (tab_bar_is_recreated && TabBarFindTabByID(tab_bar, node->SelectedTabId) != NULL)
+        tab_bar->SelectedTabId = tab_bar->NextSelectedTabId = node->SelectedTabId;
+    else if (tab_bar->Tabs.Size > tabs_count_old)
+        tab_bar->SelectedTabId = tab_bar->NextSelectedTabId = tab_bar->Tabs.back().Window->TabId;
+
+    // Begin tab bar
+    ImGuiTabBarFlags tab_bar_flags = ImGuiTabBarFlags_Reorderable | ImGuiTabBarFlags_AutoSelectNewTabs; // | ImGuiTabBarFlags_NoTabListScrollingButtons);
+    tab_bar_flags |= ImGuiTabBarFlags_SaveSettings | ImGuiTabBarFlags_DockNode;// | ImGuiTabBarFlags_FittingPolicyScroll;
+    if (!host_window->Collapsed && is_focused)
+        tab_bar_flags |= ImGuiTabBarFlags_IsFocused;
+    tab_bar->ID = GetID("#TabBar");
+    tab_bar->SeparatorMinX = node->Pos.x + host_window->WindowBorderSize; // Separator cover the whole node width
+    tab_bar->SeparatorMaxX = node->Pos.x + node->Size.x - host_window->WindowBorderSize;
+    BeginTabBarEx(tab_bar, tab_bar_rect, tab_bar_flags);
+    //host_window->DrawList->AddRect(tab_bar_rect.Min, tab_bar_rect.Max, IM_COL32(255,0,255,255));
+
+    // Backup style colors
+    ImVec4 backup_style_cols[ImGuiWindowDockStyleCol_COUNT];
+    for (int color_n = 0; color_n < ImGuiWindowDockStyleCol_COUNT; color_n++)
+        backup_style_cols[color_n] = g.Style.Colors[GWindowDockStyleColors[color_n]];
+
+    // Submit actual tabs
+    node->VisibleWindow = NULL;
+    for (int window_n = 0; window_n < node->Windows.Size; window_n++)
+    {
+        ImGuiWindow* window = node->Windows[window_n];
+        if ((closed_all || closed_one == window->TabId) && window->HasCloseButton && !(window->Flags & ImGuiWindowFlags_UnsavedDocument))
+            continue;
+        if (window->LastFrameActive + 1 >= g.FrameCount || !node_was_active)
+        {
+            ImGuiTabItemFlags tab_item_flags = 0;
+            tab_item_flags |= window->WindowClass.TabItemFlagsOverrideSet;
+            if (window->Flags & ImGuiWindowFlags_UnsavedDocument)
+                tab_item_flags |= ImGuiTabItemFlags_UnsavedDocument;
+            if (tab_bar->Flags & ImGuiTabBarFlags_NoCloseWithMiddleMouseButton)
+                tab_item_flags |= ImGuiTabItemFlags_NoCloseWithMiddleMouseButton;
+
+            // Apply stored style overrides for the window
+            for (int color_n = 0; color_n < ImGuiWindowDockStyleCol_COUNT; color_n++)
+                g.Style.Colors[GWindowDockStyleColors[color_n]] = ColorConvertU32ToFloat4(window->DockStyle.Colors[color_n]);
+
+            // Note that TabItemEx() calls TabBarCalcTabID() so our tab item ID will ignore the current ID stack (rightly so)
+            bool tab_open = true;
+            TabItemEx(tab_bar, window->Name, window->HasCloseButton ? &tab_open : NULL, tab_item_flags, window);
+            if (!tab_open)
+                node->WantCloseTabId = window->TabId;
+            if (tab_bar->VisibleTabId == window->TabId)
+                node->VisibleWindow = window;
+
+            // Store last item data so it can be queried with IsItemXXX functions after the user Begin() call
+            window->DockTabItemStatusFlags = g.LastItemData.StatusFlags;
+            window->DockTabItemRect = g.LastItemData.Rect;
+
+            // Update navigation ID on menu layer
+            if (g.NavWindow && g.NavWindow->RootWindow == window && (window->DC.NavLayersActiveMask & (1 << ImGuiNavLayer_Menu)) == 0)
+                host_window->NavLastIds[1] = window->TabId;
+        }
+    }
+
+    // Restore style colors
+    for (int color_n = 0; color_n < ImGuiWindowDockStyleCol_COUNT; color_n++)
+        g.Style.Colors[GWindowDockStyleColors[color_n]] = backup_style_cols[color_n];
+
+    // Notify root of visible window (used to display title in OS task bar)
+    if (node->VisibleWindow)
+        if (is_focused || root_node->VisibleWindow == NULL)
+            root_node->VisibleWindow = node->VisibleWindow;
+
+    // Close button (after VisibleWindow was updated)
+    // Note that VisibleWindow may have been overrided by CTRL+Tabbing, so VisibleWindow->TabId may be != from tab_bar->SelectedTabId
+    const bool close_button_is_enabled = node->HasCloseButton && node->VisibleWindow && node->VisibleWindow->HasCloseButton;
+    const bool close_button_is_visible = node->HasCloseButton;
+    //const bool close_button_is_visible = close_button_is_enabled; // Most people would expect this behavior of not even showing the button (leaving a hole since we can't claim that space as other windows in the tba bar have one)
+    if (close_button_is_visible)
+    {
+        if (!close_button_is_enabled)
+        {
+            PushItemFlag(ImGuiItemFlags_Disabled, true);
+            PushStyleColor(ImGuiCol_Text, style.Colors[ImGuiCol_Text] * ImVec4(1.0f,1.0f,1.0f,0.4f));
+        }
+        if (CloseButton(host_window->GetID("#CLOSE"), close_button_pos))
+        {
+            node->WantCloseAll = true;
+            for (int n = 0; n < tab_bar->Tabs.Size; n++)
+                TabBarCloseTab(tab_bar, &tab_bar->Tabs[n]);
+        }
+        //if (IsItemActive())
+        //    focus_tab_id = tab_bar->SelectedTabId;
+        if (!close_button_is_enabled)
+        {
+            PopStyleColor();
+            PopItemFlag();
+        }
+    }
+
+    // When clicking on the title bar outside of tabs, we still focus the selected tab for that node
+    // FIXME: TabItems submitted earlier use AllowItemOverlap so we manually perform a more specific test for now (hovered || held) in order to not cover them.
+    ImGuiID title_bar_id = host_window->GetID("#TITLEBAR");
+    if (g.HoveredId == 0 || g.HoveredId == title_bar_id || g.ActiveId == title_bar_id)
+    {
+        // AllowOverlap mode required for appending into dock node tab bar,
+        // otherwise dragging window will steal HoveredId and amended tabs cannot get them.
+        bool held;
+        KeepAliveID(title_bar_id);
+        ButtonBehavior(title_bar_rect, title_bar_id, NULL, &held, ImGuiButtonFlags_AllowOverlap);
+        if (g.HoveredId == title_bar_id)
+        {
+            g.LastItemData.ID = title_bar_id;
+        }
+        if (held)
+        {
+            if (IsMouseClicked(0))
+                focus_tab_id = tab_bar->SelectedTabId;
+
+            // Forward moving request to selected window
+            if (ImGuiTabItem* tab = TabBarFindTabByID(tab_bar, tab_bar->SelectedTabId))
+                StartMouseMovingWindowOrNode(tab->Window ? tab->Window : node->HostWindow, node, false); // Undock from tab bar empty space
+        }
+    }
+
+    // Forward focus from host node to selected window
+    //if (is_focused && g.NavWindow == host_window && !g.NavWindowingTarget)
+    //    focus_tab_id = tab_bar->SelectedTabId;
+
+    // When clicked on a tab we requested focus to the docked child
+    // This overrides the value set by "forward focus from host node to selected window".
+    if (tab_bar->NextSelectedTabId)
+        focus_tab_id = tab_bar->NextSelectedTabId;
+
+    // Apply navigation focus
+    if (focus_tab_id != 0)
+        if (ImGuiTabItem* tab = TabBarFindTabByID(tab_bar, focus_tab_id))
+            if (tab->Window)
+            {
+                FocusWindow(tab->Window);
+                NavInitWindow(tab->Window, false);
+            }
+
+    EndTabBar();
+    PopID();
+
+    // Restore SkipItems flag
+    if (!node->IsDockSpace())
+    {
+        host_window->DC.NavLayerCurrent = ImGuiNavLayer_Main;
+        host_window->SkipItems = backup_skip_item;
+    }
+}
+
+static void ImGui::DockNodeAddTabBar(ImGuiDockNode* node)
+{
+    IM_ASSERT(node->TabBar == NULL);
+    node->TabBar = IM_NEW(ImGuiTabBar);
+}
+
+static void ImGui::DockNodeRemoveTabBar(ImGuiDockNode* node)
+{
+    if (node->TabBar == NULL)
+        return;
+    IM_DELETE(node->TabBar);
+    node->TabBar = NULL;
+}
+
+static bool DockNodeIsDropAllowedOne(ImGuiWindow* payload, ImGuiWindow* host_window)
+{
+    if (host_window->DockNodeAsHost && host_window->DockNodeAsHost->IsDockSpace() && payload->BeginOrderWithinContext < host_window->BeginOrderWithinContext)
+        return false;
+
+    ImGuiWindowClass* host_class = host_window->DockNodeAsHost ? &host_window->DockNodeAsHost->WindowClass : &host_window->WindowClass;
+    ImGuiWindowClass* payload_class = &payload->WindowClass;
+    if (host_class->ClassId != payload_class->ClassId)
+    {
+        bool pass = false;
+        if (host_class->ClassId != 0 && host_class->DockingAllowUnclassed && payload_class->ClassId == 0)
+            pass = true;
+        if (payload_class->ClassId != 0 && payload_class->DockingAllowUnclassed && host_class->ClassId == 0)
+            pass = true;
+        if (!pass)
+            return false;
+    }
+
+    // Prevent docking any window created above a popup
+    // Technically we should support it (e.g. in the case of a long-lived modal window that had fancy docking features),
+    // by e.g. adding a 'if (!ImGui::IsWindowWithinBeginStackOf(host_window, popup_window))' test.
+    // But it would requires more work on our end because the dock host windows is technically created in NewFrame()
+    // and our ->ParentXXX and ->RootXXX pointers inside windows are currently mislading or lacking.
+    ImGuiContext& g = *GImGui;
+    for (int i = g.OpenPopupStack.Size - 1; i >= 0; i--)
+        if (ImGuiWindow* popup_window = g.OpenPopupStack[i].Window)
+            if (ImGui::IsWindowWithinBeginStackOf(payload, popup_window))   // Payload is created from within a popup begin stack.
+                return false;
+
+    return true;
+}
+
+static bool ImGui::DockNodeIsDropAllowed(ImGuiWindow* host_window, ImGuiWindow* root_payload)
+{
+    if (root_payload->DockNodeAsHost && root_payload->DockNodeAsHost->IsSplitNode()) // FIXME-DOCK: Missing filtering
+        return true;
+
+    const int payload_count = root_payload->DockNodeAsHost ? root_payload->DockNodeAsHost->Windows.Size : 1;
+    for (int payload_n = 0; payload_n < payload_count; payload_n++)
+    {
+        ImGuiWindow* payload = root_payload->DockNodeAsHost ? root_payload->DockNodeAsHost->Windows[payload_n] : root_payload;
+        if (DockNodeIsDropAllowedOne(payload, host_window))
+            return true;
+    }
+    return false;
+}
+
+// window menu button == collapse button when not in a dock node.
+// FIXME: This is similar to RenderWindowTitleBarContents(), may want to share code.
+static void ImGui::DockNodeCalcTabBarLayout(const ImGuiDockNode* node, ImRect* out_title_rect, ImRect* out_tab_bar_rect, ImVec2* out_window_menu_button_pos, ImVec2* out_close_button_pos)
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiStyle& style = g.Style;
+
+    ImRect r = ImRect(node->Pos.x, node->Pos.y, node->Pos.x + node->Size.x, node->Pos.y + g.FontSize + g.Style.FramePadding.y * 2.0f);
+    if (out_title_rect) { *out_title_rect = r; }
+
+    r.Min.x += style.WindowBorderSize;
+    r.Max.x -= style.WindowBorderSize;
+
+    float button_sz = g.FontSize;
+    r.Min.x += style.FramePadding.x;
+    r.Max.x -= style.FramePadding.x;
+    ImVec2 window_menu_button_pos = ImVec2(r.Min.x, r.Min.y + style.FramePadding.y);
+    if (node->HasCloseButton)
+    {
+        if (out_close_button_pos) *out_close_button_pos = ImVec2(r.Max.x - button_sz, r.Min.y + style.FramePadding.y);
+        r.Max.x -= button_sz + style.ItemInnerSpacing.x;
+    }
+    if (node->HasWindowMenuButton && style.WindowMenuButtonPosition == ImGuiDir_Left)
+    {
+        r.Min.x += button_sz + style.ItemInnerSpacing.x;
+    }
+    else if (node->HasWindowMenuButton && style.WindowMenuButtonPosition == ImGuiDir_Right)
+    {
+        window_menu_button_pos = ImVec2(r.Max.x - button_sz, r.Min.y + style.FramePadding.y);
+        r.Max.x -= button_sz + style.ItemInnerSpacing.x;
+    }
+    if (out_tab_bar_rect) { *out_tab_bar_rect = r; }
+    if (out_window_menu_button_pos) { *out_window_menu_button_pos = window_menu_button_pos; }
+}
+
+void ImGui::DockNodeCalcSplitRects(ImVec2& pos_old, ImVec2& size_old, ImVec2& pos_new, ImVec2& size_new, ImGuiDir dir, ImVec2 size_new_desired)
+{
+    ImGuiContext& g = *GImGui;
+    const float dock_spacing = g.Style.ItemInnerSpacing.x;
+    const ImGuiAxis axis = (dir == ImGuiDir_Left || dir == ImGuiDir_Right) ? ImGuiAxis_X : ImGuiAxis_Y;
+    pos_new[axis ^ 1] = pos_old[axis ^ 1];
+    size_new[axis ^ 1] = size_old[axis ^ 1];
+
+    // Distribute size on given axis (with a desired size or equally)
+    const float w_avail = size_old[axis] - dock_spacing;
+    if (size_new_desired[axis] > 0.0f && size_new_desired[axis] <= w_avail * 0.5f)
+    {
+        size_new[axis] = size_new_desired[axis];
+        size_old[axis] = IM_TRUNC(w_avail - size_new[axis]);
+    }
+    else
+    {
+        size_new[axis] = IM_TRUNC(w_avail * 0.5f);
+        size_old[axis] = IM_TRUNC(w_avail - size_new[axis]);
+    }
+
+    // Position each node
+    if (dir == ImGuiDir_Right || dir == ImGuiDir_Down)
+    {
+        pos_new[axis] = pos_old[axis] + size_old[axis] + dock_spacing;
+    }
+    else if (dir == ImGuiDir_Left || dir == ImGuiDir_Up)
+    {
+        pos_new[axis] = pos_old[axis];
+        pos_old[axis] = pos_new[axis] + size_new[axis] + dock_spacing;
+    }
+}
+
+// Retrieve the drop rectangles for a given direction or for the center + perform hit testing.
+bool ImGui::DockNodeCalcDropRectsAndTestMousePos(const ImRect& parent, ImGuiDir dir, ImRect& out_r, bool outer_docking, ImVec2* test_mouse_pos)
+{
+    ImGuiContext& g = *GImGui;
+
+    const float parent_smaller_axis = ImMin(parent.GetWidth(), parent.GetHeight());
+    const float hs_for_central_nodes = ImMin(g.FontSize * 1.5f, ImMax(g.FontSize * 0.5f, parent_smaller_axis / 8.0f));
+    float hs_w; // Half-size, longer axis
+    float hs_h; // Half-size, smaller axis
+    ImVec2 off; // Distance from edge or center
+    if (outer_docking)
+    {
+        //hs_w = ImTrunc(ImClamp(parent_smaller_axis - hs_for_central_nodes * 4.0f, g.FontSize * 0.5f, g.FontSize * 8.0f));
+        //hs_h = ImTrunc(hs_w * 0.15f);
+        //off = ImVec2(ImTrunc(parent.GetWidth() * 0.5f - GetFrameHeightWithSpacing() * 1.4f - hs_h), ImTrunc(parent.GetHeight() * 0.5f - GetFrameHeightWithSpacing() * 1.4f - hs_h));
+        hs_w = ImTrunc(hs_for_central_nodes * 1.50f);
+        hs_h = ImTrunc(hs_for_central_nodes * 0.80f);
+        off = ImTrunc(ImVec2(parent.GetWidth() * 0.5f - hs_h, parent.GetHeight() * 0.5f - hs_h));
+    }
+    else
+    {
+        hs_w = ImTrunc(hs_for_central_nodes);
+        hs_h = ImTrunc(hs_for_central_nodes * 0.90f);
+        off = ImTrunc(ImVec2(hs_w * 2.40f, hs_w * 2.40f));
+    }
+
+    ImVec2 c = ImTrunc(parent.GetCenter());
+    if      (dir == ImGuiDir_None)  { out_r = ImRect(c.x - hs_w, c.y - hs_w,         c.x + hs_w, c.y + hs_w);         }
+    else if (dir == ImGuiDir_Up)    { out_r = ImRect(c.x - hs_w, c.y - off.y - hs_h, c.x + hs_w, c.y - off.y + hs_h); }
+    else if (dir == ImGuiDir_Down)  { out_r = ImRect(c.x - hs_w, c.y + off.y - hs_h, c.x + hs_w, c.y + off.y + hs_h); }
+    else if (dir == ImGuiDir_Left)  { out_r = ImRect(c.x - off.x - hs_h, c.y - hs_w, c.x - off.x + hs_h, c.y + hs_w); }
+    else if (dir == ImGuiDir_Right) { out_r = ImRect(c.x + off.x - hs_h, c.y - hs_w, c.x + off.x + hs_h, c.y + hs_w); }
+
+    if (test_mouse_pos == NULL)
+        return false;
+
+    ImRect hit_r = out_r;
+    if (!outer_docking)
+    {
+        // Custom hit testing for the 5-way selection, designed to reduce flickering when moving diagonally between sides
+        hit_r.Expand(ImTrunc(hs_w * 0.30f));
+        ImVec2 mouse_delta = (*test_mouse_pos - c);
+        float mouse_delta_len2 = ImLengthSqr(mouse_delta);
+        float r_threshold_center = hs_w * 1.4f;
+        float r_threshold_sides = hs_w * (1.4f + 1.2f);
+        if (mouse_delta_len2 < r_threshold_center * r_threshold_center)
+            return (dir == ImGuiDir_None);
+        if (mouse_delta_len2 < r_threshold_sides * r_threshold_sides)
+            return (dir == ImGetDirQuadrantFromDelta(mouse_delta.x, mouse_delta.y));
+    }
+    return hit_r.Contains(*test_mouse_pos);
+}
+
+// host_node may be NULL if the window doesn't have a DockNode already.
+// FIXME-DOCK: This is misnamed since it's also doing the filtering.
+static void ImGui::DockNodePreviewDockSetup(ImGuiWindow* host_window, ImGuiDockNode* host_node, ImGuiWindow* payload_window, ImGuiDockNode* payload_node, ImGuiDockPreviewData* data, bool is_explicit_target, bool is_outer_docking)
+{
+    ImGuiContext& g = *GImGui;
+
+    // There is an edge case when docking into a dockspace which only has inactive nodes.
+    // In this case DockNodeTreeFindNodeByPos() will have selected a leaf node which is inactive.
+    // Because the inactive leaf node doesn't have proper pos/size yet, we'll use the root node as reference.
+    if (payload_node == NULL)
+        payload_node = payload_window->DockNodeAsHost;
+    ImGuiDockNode* ref_node_for_rect = (host_node && !host_node->IsVisible) ? DockNodeGetRootNode(host_node) : host_node;
+    if (ref_node_for_rect)
+        IM_ASSERT(ref_node_for_rect->IsVisible == true);
+
+    // Filter, figure out where we are allowed to dock
+    ImGuiDockNodeFlags src_node_flags = payload_node ? payload_node->MergedFlags : payload_window->WindowClass.DockNodeFlagsOverrideSet;
+    ImGuiDockNodeFlags dst_node_flags = host_node ? host_node->MergedFlags : host_window->WindowClass.DockNodeFlagsOverrideSet;
+    data->IsCenterAvailable = true;
+    if (is_outer_docking)
+        data->IsCenterAvailable = false;
+    else if (dst_node_flags & ImGuiDockNodeFlags_NoDockingOverMe)
+        data->IsCenterAvailable = false;
+    else if (host_node && (dst_node_flags & ImGuiDockNodeFlags_NoDockingOverCentralNode) && host_node->IsCentralNode())
+        data->IsCenterAvailable = false;
+    else if ((!host_node || !host_node->IsEmpty()) && payload_node && payload_node->IsSplitNode() && (payload_node->OnlyNodeWithWindows == NULL)) // Is _visibly_ split?
+        data->IsCenterAvailable = false;
+    else if ((src_node_flags & ImGuiDockNodeFlags_NoDockingOverOther) && (!host_node || !host_node->IsEmpty()))
+        data->IsCenterAvailable = false;
+    else if ((src_node_flags & ImGuiDockNodeFlags_NoDockingOverEmpty) && host_node && host_node->IsEmpty())
+        data->IsCenterAvailable = false;
+
+    data->IsSidesAvailable = true;
+    if ((dst_node_flags & ImGuiDockNodeFlags_NoDockingSplit) || g.IO.ConfigDockingNoSplit)
+        data->IsSidesAvailable = false;
+    else if (!is_outer_docking && host_node && host_node->ParentNode == NULL && host_node->IsCentralNode())
+        data->IsSidesAvailable = false;
+    else if (src_node_flags & ImGuiDockNodeFlags_NoDockingSplitOther)
+        data->IsSidesAvailable = false;
+
+    // Build a tentative future node (reuse same structure because it is practical. Shape will be readjusted when previewing a split)
+    data->FutureNode.HasCloseButton = (host_node ? host_node->HasCloseButton : host_window->HasCloseButton) || (payload_window->HasCloseButton);
+    data->FutureNode.HasWindowMenuButton = host_node ? true : ((host_window->Flags & ImGuiWindowFlags_NoCollapse) == 0);
+    data->FutureNode.Pos = ref_node_for_rect ? ref_node_for_rect->Pos : host_window->Pos;
+    data->FutureNode.Size = ref_node_for_rect ? ref_node_for_rect->Size : host_window->Size;
+
+    // Calculate drop shapes geometry for allowed splitting directions
+    IM_ASSERT(ImGuiDir_None == -1);
+    data->SplitNode = host_node;
+    data->SplitDir = ImGuiDir_None;
+    data->IsSplitDirExplicit = false;
+    if (!host_window->Collapsed)
+        for (int dir = ImGuiDir_None; dir < ImGuiDir_COUNT; dir++)
+        {
+            if (dir == ImGuiDir_None && !data->IsCenterAvailable)
+                continue;
+            if (dir != ImGuiDir_None && !data->IsSidesAvailable)
+                continue;
+            if (DockNodeCalcDropRectsAndTestMousePos(data->FutureNode.Rect(), (ImGuiDir)dir, data->DropRectsDraw[dir+1], is_outer_docking, &g.IO.MousePos))
+            {
+                data->SplitDir = (ImGuiDir)dir;
+                data->IsSplitDirExplicit = true;
+            }
+        }
+
+    // When docking without holding Shift, we only allow and preview docking when hovering over a drop rect or over the title bar
+    data->IsDropAllowed = (data->SplitDir != ImGuiDir_None) || (data->IsCenterAvailable);
+    if (!is_explicit_target && !data->IsSplitDirExplicit && !g.IO.ConfigDockingWithShift)
+        data->IsDropAllowed = false;
+
+    // Calculate split area
+    data->SplitRatio = 0.0f;
+    if (data->SplitDir != ImGuiDir_None)
+    {
+        ImGuiDir split_dir = data->SplitDir;
+        ImGuiAxis split_axis = (split_dir == ImGuiDir_Left || split_dir == ImGuiDir_Right) ? ImGuiAxis_X : ImGuiAxis_Y;
+        ImVec2 pos_new, pos_old = data->FutureNode.Pos;
+        ImVec2 size_new, size_old = data->FutureNode.Size;
+        DockNodeCalcSplitRects(pos_old, size_old, pos_new, size_new, split_dir, payload_window->Size);
+
+        // Calculate split ratio so we can pass it down the docking request
+        float split_ratio = ImSaturate(size_new[split_axis] / data->FutureNode.Size[split_axis]);
+        data->FutureNode.Pos = pos_new;
+        data->FutureNode.Size = size_new;
+        data->SplitRatio = (split_dir == ImGuiDir_Right || split_dir == ImGuiDir_Down) ? (1.0f - split_ratio) : (split_ratio);
+    }
+}
+
+static void ImGui::DockNodePreviewDockRender(ImGuiWindow* host_window, ImGuiDockNode* host_node, ImGuiWindow* root_payload, const ImGuiDockPreviewData* data)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(g.CurrentWindow == host_window);   // Because we rely on font size to calculate tab sizes
+
+    // With this option, we only display the preview on the target viewport, and the payload viewport is made transparent.
+    // To compensate for the single layer obstructed by the payload, we'll increase the alpha of the preview nodes.
+    const bool is_transparent_payload = g.IO.ConfigDockingTransparentPayload;
+
+    // In case the two windows involved are on different viewports, we will draw the overlay on each of them.
+    int overlay_draw_lists_count = 0;
+    ImDrawList* overlay_draw_lists[2];
+    overlay_draw_lists[overlay_draw_lists_count++] = GetForegroundDrawList(host_window->Viewport);
+    if (host_window->Viewport != root_payload->Viewport && !is_transparent_payload)
+        overlay_draw_lists[overlay_draw_lists_count++] = GetForegroundDrawList(root_payload->Viewport);
+
+    // Draw main preview rectangle
+    const ImU32 overlay_col_main = GetColorU32(ImGuiCol_DockingPreview, is_transparent_payload ? 0.60f : 0.40f);
+    const ImU32 overlay_col_drop = GetColorU32(ImGuiCol_DockingPreview, is_transparent_payload ? 0.90f : 0.70f);
+    const ImU32 overlay_col_drop_hovered = GetColorU32(ImGuiCol_DockingPreview, is_transparent_payload ? 1.20f : 1.00f);
+    const ImU32 overlay_col_lines = GetColorU32(ImGuiCol_NavWindowingHighlight, is_transparent_payload ? 0.80f : 0.60f);
+
+    // Display area preview
+    const bool can_preview_tabs = (root_payload->DockNodeAsHost == NULL || root_payload->DockNodeAsHost->Windows.Size > 0);
+    if (data->IsDropAllowed)
+    {
+        ImRect overlay_rect = data->FutureNode.Rect();
+        if (data->SplitDir == ImGuiDir_None && can_preview_tabs)
+            overlay_rect.Min.y += GetFrameHeight();
+        if (data->SplitDir != ImGuiDir_None || data->IsCenterAvailable)
+            for (int overlay_n = 0; overlay_n < overlay_draw_lists_count; overlay_n++)
+                overlay_draw_lists[overlay_n]->AddRectFilled(overlay_rect.Min, overlay_rect.Max, overlay_col_main, host_window->WindowRounding, CalcRoundingFlagsForRectInRect(overlay_rect, host_window->Rect(), g.Style.DockingSeparatorSize));
+    }
+
+    // Display tab shape/label preview unless we are splitting node (it generally makes the situation harder to read)
+    if (data->IsDropAllowed && can_preview_tabs && data->SplitDir == ImGuiDir_None && data->IsCenterAvailable)
+    {
+        // Compute target tab bar geometry so we can locate our preview tabs
+        ImRect tab_bar_rect;
+        DockNodeCalcTabBarLayout(&data->FutureNode, NULL, &tab_bar_rect, NULL, NULL);
+        ImVec2 tab_pos = tab_bar_rect.Min;
+        if (host_node && host_node->TabBar)
+        {
+            if (!host_node->IsHiddenTabBar() && !host_node->IsNoTabBar())
+                tab_pos.x += host_node->TabBar->WidthAllTabs + g.Style.ItemInnerSpacing.x; // We don't use OffsetNewTab because when using non-persistent-order tab bar it is incremented with each Tab submission.
+            else
+                tab_pos.x += g.Style.ItemInnerSpacing.x + TabItemCalcSize(host_node->Windows[0]).x;
+        }
+        else if (!(host_window->Flags & ImGuiWindowFlags_DockNodeHost))
+        {
+            tab_pos.x += g.Style.ItemInnerSpacing.x + TabItemCalcSize(host_window).x; // Account for slight offset which will be added when changing from title bar to tab bar
+        }
+
+        // Draw tab shape/label preview (payload may be a loose window or a host window carrying multiple tabbed windows)
+        if (root_payload->DockNodeAsHost)
+            IM_ASSERT(root_payload->DockNodeAsHost->Windows.Size <= root_payload->DockNodeAsHost->TabBar->Tabs.Size);
+        ImGuiTabBar* tab_bar_with_payload = root_payload->DockNodeAsHost ? root_payload->DockNodeAsHost->TabBar : NULL;
+        const int payload_count = tab_bar_with_payload ? tab_bar_with_payload->Tabs.Size : 1;
+        for (int payload_n = 0; payload_n < payload_count; payload_n++)
+        {
+            // DockNode's TabBar may have non-window Tabs manually appended by user
+            ImGuiWindow* payload_window = tab_bar_with_payload ? tab_bar_with_payload->Tabs[payload_n].Window : root_payload;
+            if (tab_bar_with_payload && payload_window == NULL)
+                continue;
+            if (!DockNodeIsDropAllowedOne(payload_window, host_window))
+                continue;
+
+            // Calculate the tab bounding box for each payload window
+            ImVec2 tab_size = TabItemCalcSize(payload_window);
+            ImRect tab_bb(tab_pos.x, tab_pos.y, tab_pos.x + tab_size.x, tab_pos.y + tab_size.y);
+            tab_pos.x += tab_size.x + g.Style.ItemInnerSpacing.x;
+            const ImU32 overlay_col_text = GetColorU32(payload_window->DockStyle.Colors[ImGuiWindowDockStyleCol_Text]);
+            const ImU32 overlay_col_tabs = GetColorU32(payload_window->DockStyle.Colors[ImGuiWindowDockStyleCol_TabActive]);
+            PushStyleColor(ImGuiCol_Text, overlay_col_text);
+            for (int overlay_n = 0; overlay_n < overlay_draw_lists_count; overlay_n++)
+            {
+                ImGuiTabItemFlags tab_flags = (payload_window->Flags & ImGuiWindowFlags_UnsavedDocument) ? ImGuiTabItemFlags_UnsavedDocument : 0;
+                if (!tab_bar_rect.Contains(tab_bb))
+                    overlay_draw_lists[overlay_n]->PushClipRect(tab_bar_rect.Min, tab_bar_rect.Max);
+                TabItemBackground(overlay_draw_lists[overlay_n], tab_bb, tab_flags, overlay_col_tabs);
+                TabItemLabelAndCloseButton(overlay_draw_lists[overlay_n], tab_bb, tab_flags, g.Style.FramePadding, payload_window->Name, 0, 0, false, NULL, NULL);
+                if (!tab_bar_rect.Contains(tab_bb))
+                    overlay_draw_lists[overlay_n]->PopClipRect();
+            }
+            PopStyleColor();
+        }
+    }
+
+    // Display drop boxes
+    const float overlay_rounding = ImMax(3.0f, g.Style.FrameRounding);
+    for (int dir = ImGuiDir_None; dir < ImGuiDir_COUNT; dir++)
+    {
+        if (!data->DropRectsDraw[dir + 1].IsInverted())
+        {
+            ImRect draw_r = data->DropRectsDraw[dir + 1];
+            ImRect draw_r_in = draw_r;
+            draw_r_in.Expand(-2.0f);
+            ImU32 overlay_col = (data->SplitDir == (ImGuiDir)dir && data->IsSplitDirExplicit) ? overlay_col_drop_hovered : overlay_col_drop;
+            for (int overlay_n = 0; overlay_n < overlay_draw_lists_count; overlay_n++)
+            {
+                ImVec2 center = ImFloor(draw_r_in.GetCenter());
+                overlay_draw_lists[overlay_n]->AddRectFilled(draw_r.Min, draw_r.Max, overlay_col, overlay_rounding);
+                overlay_draw_lists[overlay_n]->AddRect(draw_r_in.Min, draw_r_in.Max, overlay_col_lines, overlay_rounding);
+                if (dir == ImGuiDir_Left || dir == ImGuiDir_Right)
+                    overlay_draw_lists[overlay_n]->AddLine(ImVec2(center.x, draw_r_in.Min.y), ImVec2(center.x, draw_r_in.Max.y), overlay_col_lines);
+                if (dir == ImGuiDir_Up || dir == ImGuiDir_Down)
+                    overlay_draw_lists[overlay_n]->AddLine(ImVec2(draw_r_in.Min.x, center.y), ImVec2(draw_r_in.Max.x, center.y), overlay_col_lines);
+            }
+        }
+
+        // Stop after ImGuiDir_None
+        if ((host_node && (host_node->MergedFlags & ImGuiDockNodeFlags_NoDockingSplit)) || g.IO.ConfigDockingNoSplit)
+            return;
+    }
+}
+
+//-----------------------------------------------------------------------------
+// Docking: ImGuiDockNode Tree manipulation functions
+//-----------------------------------------------------------------------------
+// - DockNodeTreeSplit()
+// - DockNodeTreeMerge()
+// - DockNodeTreeUpdatePosSize()
+// - DockNodeTreeUpdateSplitterFindTouchingNode()
+// - DockNodeTreeUpdateSplitter()
+// - DockNodeTreeFindFallbackLeafNode()
+// - DockNodeTreeFindNodeByPos()
+//-----------------------------------------------------------------------------
+
+void ImGui::DockNodeTreeSplit(ImGuiContext* ctx, ImGuiDockNode* parent_node, ImGuiAxis split_axis, int split_inheritor_child_idx, float split_ratio, ImGuiDockNode* new_node)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(split_axis != ImGuiAxis_None);
+
+    ImGuiDockNode* child_0 = (new_node && split_inheritor_child_idx != 0) ? new_node : DockContextAddNode(ctx, 0);
+    child_0->ParentNode = parent_node;
+
+    ImGuiDockNode* child_1 = (new_node && split_inheritor_child_idx != 1) ? new_node : DockContextAddNode(ctx, 0);
+    child_1->ParentNode = parent_node;
+
+    ImGuiDockNode* child_inheritor = (split_inheritor_child_idx == 0) ? child_0 : child_1;
+    DockNodeMoveChildNodes(child_inheritor, parent_node);
+    parent_node->ChildNodes[0] = child_0;
+    parent_node->ChildNodes[1] = child_1;
+    parent_node->ChildNodes[split_inheritor_child_idx]->VisibleWindow = parent_node->VisibleWindow;
+    parent_node->SplitAxis = split_axis;
+    parent_node->VisibleWindow = NULL;
+    parent_node->AuthorityForPos = parent_node->AuthorityForSize = ImGuiDataAuthority_DockNode;
+
+    float size_avail = (parent_node->Size[split_axis] - g.Style.DockingSeparatorSize);
+    size_avail = ImMax(size_avail, g.Style.WindowMinSize[split_axis] * 2.0f);
+    IM_ASSERT(size_avail > 0.0f); // If you created a node manually with DockBuilderAddNode(), you need to also call DockBuilderSetNodeSize() before splitting.
+    child_0->SizeRef = child_1->SizeRef = parent_node->Size;
+    child_0->SizeRef[split_axis] = ImTrunc(size_avail * split_ratio);
+    child_1->SizeRef[split_axis] = ImTrunc(size_avail - child_0->SizeRef[split_axis]);
+
+    DockNodeMoveWindows(parent_node->ChildNodes[split_inheritor_child_idx], parent_node);
+    DockSettingsRenameNodeReferences(parent_node->ID, parent_node->ChildNodes[split_inheritor_child_idx]->ID);
+    DockNodeUpdateHasCentralNodeChild(DockNodeGetRootNode(parent_node));
+    DockNodeTreeUpdatePosSize(parent_node, parent_node->Pos, parent_node->Size);
+
+    // Flags transfer (e.g. this is where we transfer the ImGuiDockNodeFlags_CentralNode property)
+    child_0->SharedFlags = parent_node->SharedFlags & ImGuiDockNodeFlags_SharedFlagsInheritMask_;
+    child_1->SharedFlags = parent_node->SharedFlags & ImGuiDockNodeFlags_SharedFlagsInheritMask_;
+    child_inheritor->LocalFlags = parent_node->LocalFlags & ImGuiDockNodeFlags_LocalFlagsTransferMask_;
+    parent_node->LocalFlags &= ~ImGuiDockNodeFlags_LocalFlagsTransferMask_;
+    child_0->UpdateMergedFlags();
+    child_1->UpdateMergedFlags();
+    parent_node->UpdateMergedFlags();
+    if (child_inheritor->IsCentralNode())
+        DockNodeGetRootNode(parent_node)->CentralNode = child_inheritor;
+}
+
+void ImGui::DockNodeTreeMerge(ImGuiContext* ctx, ImGuiDockNode* parent_node, ImGuiDockNode* merge_lead_child)
+{
+    // When called from DockContextProcessUndockNode() it is possible that one of the child is NULL.
+    ImGuiContext& g = *GImGui;
+    ImGuiDockNode* child_0 = parent_node->ChildNodes[0];
+    ImGuiDockNode* child_1 = parent_node->ChildNodes[1];
+    IM_ASSERT(child_0 || child_1);
+    IM_ASSERT(merge_lead_child == child_0 || merge_lead_child == child_1);
+    if ((child_0 && child_0->Windows.Size > 0) || (child_1 && child_1->Windows.Size > 0))
+    {
+        IM_ASSERT(parent_node->TabBar == NULL);
+        IM_ASSERT(parent_node->Windows.Size == 0);
+    }
+    IMGUI_DEBUG_LOG_DOCKING("[docking] DockNodeTreeMerge: 0x%08X + 0x%08X back into parent 0x%08X\n", child_0 ? child_0->ID : 0, child_1 ? child_1->ID : 0, parent_node->ID);
+
+    ImVec2 backup_last_explicit_size = parent_node->SizeRef;
+    DockNodeMoveChildNodes(parent_node, merge_lead_child);
+    if (child_0)
+    {
+        DockNodeMoveWindows(parent_node, child_0); // Generally only 1 of the 2 child node will have windows
+        DockSettingsRenameNodeReferences(child_0->ID, parent_node->ID);
+    }
+    if (child_1)
+    {
+        DockNodeMoveWindows(parent_node, child_1);
+        DockSettingsRenameNodeReferences(child_1->ID, parent_node->ID);
+    }
+    DockNodeApplyPosSizeToWindows(parent_node);
+    parent_node->AuthorityForPos = parent_node->AuthorityForSize = parent_node->AuthorityForViewport = ImGuiDataAuthority_Auto;
+    parent_node->VisibleWindow = merge_lead_child->VisibleWindow;
+    parent_node->SizeRef = backup_last_explicit_size;
+
+    // Flags transfer
+    parent_node->LocalFlags &= ~ImGuiDockNodeFlags_LocalFlagsTransferMask_; // Preserve Dockspace flag
+    parent_node->LocalFlags |= (child_0 ? child_0->LocalFlags : 0) & ImGuiDockNodeFlags_LocalFlagsTransferMask_;
+    parent_node->LocalFlags |= (child_1 ? child_1->LocalFlags : 0) & ImGuiDockNodeFlags_LocalFlagsTransferMask_;
+    parent_node->LocalFlagsInWindows = (child_0 ? child_0->LocalFlagsInWindows : 0) | (child_1 ? child_1->LocalFlagsInWindows : 0); // FIXME: Would be more consistent to update from actual windows
+    parent_node->UpdateMergedFlags();
+
+    if (child_0)
+    {
+        ctx->DockContext.Nodes.SetVoidPtr(child_0->ID, NULL);
+        IM_DELETE(child_0);
+    }
+    if (child_1)
+    {
+        ctx->DockContext.Nodes.SetVoidPtr(child_1->ID, NULL);
+        IM_DELETE(child_1);
+    }
+}
+
+// Update Pos/Size for a node hierarchy (don't affect child Windows yet)
+// (Depth-first, Pre-Order)
+void ImGui::DockNodeTreeUpdatePosSize(ImGuiDockNode* node, ImVec2 pos, ImVec2 size, ImGuiDockNode* only_write_to_single_node)
+{
+    // During the regular dock node update we write to all nodes.
+    // 'only_write_to_single_node' is only set when turning a node visible mid-frame and we need its size right-away.
+    ImGuiContext& g = *GImGui;
+    const bool write_to_node = only_write_to_single_node == NULL || only_write_to_single_node == node;
+    if (write_to_node)
+    {
+        node->Pos = pos;
+        node->Size = size;
+    }
+
+    if (node->IsLeafNode())
+        return;
+
+    ImGuiDockNode* child_0 = node->ChildNodes[0];
+    ImGuiDockNode* child_1 = node->ChildNodes[1];
+    ImVec2 child_0_pos = pos, child_1_pos = pos;
+    ImVec2 child_0_size = size, child_1_size = size;
+
+    const bool child_0_is_toward_single_node = (only_write_to_single_node != NULL && DockNodeIsInHierarchyOf(only_write_to_single_node, child_0));
+    const bool child_1_is_toward_single_node = (only_write_to_single_node != NULL && DockNodeIsInHierarchyOf(only_write_to_single_node, child_1));
+    const bool child_0_is_or_will_be_visible = child_0->IsVisible || child_0_is_toward_single_node;
+    const bool child_1_is_or_will_be_visible = child_1->IsVisible || child_1_is_toward_single_node;
+
+    if (child_0_is_or_will_be_visible && child_1_is_or_will_be_visible)
+    {
+        const float spacing = g.Style.DockingSeparatorSize;
+        const ImGuiAxis axis = (ImGuiAxis)node->SplitAxis;
+        const float size_avail = ImMax(size[axis] - spacing, 0.0f);
+
+        // Size allocation policy
+        // 1) The first 0..WindowMinSize[axis]*2 are allocated evenly to both windows.
+        const float size_min_each = ImTrunc(ImMin(size_avail, g.Style.WindowMinSize[axis] * 2.0f) * 0.5f);
+
+        // FIXME: Blocks 2) and 3) are essentially doing nearly the same thing.
+        // Difference are: write-back to SizeRef; application of a minimum size; rounding before ImTrunc()
+        // Clarify and rework differences between Size & SizeRef and purpose of WantLockSizeOnce
+
+        // 2) Process locked absolute size (during a splitter resize we preserve the child of nodes not touching the splitter edge)
+        if (child_0->WantLockSizeOnce && !child_1->WantLockSizeOnce)
+        {
+            child_0_size[axis] = child_0->SizeRef[axis] = ImMin(size_avail - 1.0f, child_0->Size[axis]);
+            child_1_size[axis] = child_1->SizeRef[axis] = (size_avail - child_0_size[axis]);
+            IM_ASSERT(child_0->SizeRef[axis] > 0.0f && child_1->SizeRef[axis] > 0.0f);
+        }
+        else if (child_1->WantLockSizeOnce && !child_0->WantLockSizeOnce)
+        {
+            child_1_size[axis] = child_1->SizeRef[axis] = ImMin(size_avail - 1.0f, child_1->Size[axis]);
+            child_0_size[axis] = child_0->SizeRef[axis] = (size_avail - child_1_size[axis]);
+            IM_ASSERT(child_0->SizeRef[axis] > 0.0f && child_1->SizeRef[axis] > 0.0f);
+        }
+        else if (child_0->WantLockSizeOnce && child_1->WantLockSizeOnce)
+        {
+            // FIXME-DOCK: We cannot honor the requested size, so apply ratio.
+            // Currently this path will only be taken if code programmatically sets WantLockSizeOnce
+            float split_ratio = child_0_size[axis] / (child_0_size[axis] + child_1_size[axis]);
+            child_0_size[axis] = child_0->SizeRef[axis] = ImTrunc(size_avail * split_ratio);
+            child_1_size[axis] = child_1->SizeRef[axis] = (size_avail - child_0_size[axis]);
+            IM_ASSERT(child_0->SizeRef[axis] > 0.0f && child_1->SizeRef[axis] > 0.0f);
+        }
+
+        // 3) If one window is the central node (~ use remaining space, should be made explicit!), use explicit size from the other, and remainder for the central node
+        else if (child_0->SizeRef[axis] != 0.0f && child_1->HasCentralNodeChild)
+        {
+            child_0_size[axis] = ImMin(size_avail - size_min_each, child_0->SizeRef[axis]);
+            child_1_size[axis] = (size_avail - child_0_size[axis]);
+        }
+        else if (child_1->SizeRef[axis] != 0.0f && child_0->HasCentralNodeChild)
+        {
+            child_1_size[axis] = ImMin(size_avail - size_min_each, child_1->SizeRef[axis]);
+            child_0_size[axis] = (size_avail - child_1_size[axis]);
+        }
+        else
+        {
+            // 4) Otherwise distribute according to the relative ratio of each SizeRef value
+            float split_ratio = child_0->SizeRef[axis] / (child_0->SizeRef[axis] + child_1->SizeRef[axis]);
+            child_0_size[axis] = ImMax(size_min_each, ImTrunc(size_avail * split_ratio + 0.5f));
+            child_1_size[axis] = (size_avail - child_0_size[axis]);
+        }
+
+        child_1_pos[axis] += spacing + child_0_size[axis];
+    }
+
+    if (only_write_to_single_node == NULL)
+        child_0->WantLockSizeOnce = child_1->WantLockSizeOnce = false;
+
+    const bool child_0_recurse = only_write_to_single_node ? child_0_is_toward_single_node : child_0->IsVisible;
+    const bool child_1_recurse = only_write_to_single_node ? child_1_is_toward_single_node : child_1->IsVisible;
+    if (child_0_recurse)
+        DockNodeTreeUpdatePosSize(child_0, child_0_pos, child_0_size);
+    if (child_1_recurse)
+        DockNodeTreeUpdatePosSize(child_1, child_1_pos, child_1_size);
+}
+
+static void DockNodeTreeUpdateSplitterFindTouchingNode(ImGuiDockNode* node, ImGuiAxis axis, int side, ImVector<ImGuiDockNode*>* touching_nodes)
+{
+    if (node->IsLeafNode())
+    {
+        touching_nodes->push_back(node);
+        return;
+    }
+    if (node->ChildNodes[0]->IsVisible)
+        if (node->SplitAxis != axis || side == 0 || !node->ChildNodes[1]->IsVisible)
+            DockNodeTreeUpdateSplitterFindTouchingNode(node->ChildNodes[0], axis, side, touching_nodes);
+    if (node->ChildNodes[1]->IsVisible)
+        if (node->SplitAxis != axis || side == 1 || !node->ChildNodes[0]->IsVisible)
+            DockNodeTreeUpdateSplitterFindTouchingNode(node->ChildNodes[1], axis, side, touching_nodes);
+}
+
+// (Depth-First, Pre-Order)
+void ImGui::DockNodeTreeUpdateSplitter(ImGuiDockNode* node)
+{
+    if (node->IsLeafNode())
+        return;
+
+    ImGuiContext& g = *GImGui;
+
+    ImGuiDockNode* child_0 = node->ChildNodes[0];
+    ImGuiDockNode* child_1 = node->ChildNodes[1];
+    if (child_0->IsVisible && child_1->IsVisible)
+    {
+        // Bounding box of the splitter cover the space between both nodes (w = Spacing, h = Size[xy^1] for when splitting horizontally)
+        const ImGuiAxis axis = (ImGuiAxis)node->SplitAxis;
+        IM_ASSERT(axis != ImGuiAxis_None);
+        ImRect bb;
+        bb.Min = child_0->Pos;
+        bb.Max = child_1->Pos;
+        bb.Min[axis] += child_0->Size[axis];
+        bb.Max[axis ^ 1] += child_1->Size[axis ^ 1];
+        //if (g.IO.KeyCtrl) GetForegroundDrawList(g.CurrentWindow->Viewport)->AddRect(bb.Min, bb.Max, IM_COL32(255,0,255,255));
+
+        const ImGuiDockNodeFlags merged_flags = child_0->MergedFlags | child_1->MergedFlags; // Merged flags for BOTH childs
+        const ImGuiDockNodeFlags no_resize_axis_flag = (axis == ImGuiAxis_X) ? ImGuiDockNodeFlags_NoResizeX : ImGuiDockNodeFlags_NoResizeY;
+        if ((merged_flags & ImGuiDockNodeFlags_NoResize) || (merged_flags & no_resize_axis_flag))
+        {
+            ImGuiWindow* window = g.CurrentWindow;
+            window->DrawList->AddRectFilled(bb.Min, bb.Max, GetColorU32(ImGuiCol_Separator), g.Style.FrameRounding);
+        }
+        else
+        {
+            //bb.Min[axis] += 1; // Display a little inward so highlight doesn't connect with nearby tabs on the neighbor node.
+            //bb.Max[axis] -= 1;
+            PushID(node->ID);
+
+            // Find resizing limits by gathering list of nodes that are touching the splitter line.
+            ImVector<ImGuiDockNode*> touching_nodes[2];
+            float min_size = g.Style.WindowMinSize[axis];
+            float resize_limits[2];
+            resize_limits[0] = node->ChildNodes[0]->Pos[axis] + min_size;
+            resize_limits[1] = node->ChildNodes[1]->Pos[axis] + node->ChildNodes[1]->Size[axis] - min_size;
+
+            ImGuiID splitter_id = GetID("##Splitter");
+            if (g.ActiveId == splitter_id) // Only process when splitter is active
+            {
+                DockNodeTreeUpdateSplitterFindTouchingNode(child_0, axis, 1, &touching_nodes[0]);
+                DockNodeTreeUpdateSplitterFindTouchingNode(child_1, axis, 0, &touching_nodes[1]);
+                for (int touching_node_n = 0; touching_node_n < touching_nodes[0].Size; touching_node_n++)
+                    resize_limits[0] = ImMax(resize_limits[0], touching_nodes[0][touching_node_n]->Rect().Min[axis] + min_size);
+                for (int touching_node_n = 0; touching_node_n < touching_nodes[1].Size; touching_node_n++)
+                    resize_limits[1] = ImMin(resize_limits[1], touching_nodes[1][touching_node_n]->Rect().Max[axis] - min_size);
+
+                // [DEBUG] Render touching nodes & limits
+                /*
+                ImDrawList* draw_list = node->HostWindow ? GetForegroundDrawList(node->HostWindow) : GetForegroundDrawList(GetMainViewport());
+                for (int n = 0; n < 2; n++)
+                {
+                    for (int touching_node_n = 0; touching_node_n < touching_nodes[n].Size; touching_node_n++)
+                        draw_list->AddRect(touching_nodes[n][touching_node_n]->Pos, touching_nodes[n][touching_node_n]->Pos + touching_nodes[n][touching_node_n]->Size, IM_COL32(0, 255, 0, 255));
+                    if (axis == ImGuiAxis_X)
+                        draw_list->AddLine(ImVec2(resize_limits[n], node->ChildNodes[n]->Pos.y), ImVec2(resize_limits[n], node->ChildNodes[n]->Pos.y + node->ChildNodes[n]->Size.y), IM_COL32(255, 0, 255, 255), 3.0f);
+                    else
+                        draw_list->AddLine(ImVec2(node->ChildNodes[n]->Pos.x, resize_limits[n]), ImVec2(node->ChildNodes[n]->Pos.x + node->ChildNodes[n]->Size.x, resize_limits[n]), IM_COL32(255, 0, 255, 255), 3.0f);
+                }
+                */
+            }
+
+            // Use a short delay before highlighting the splitter (and changing the mouse cursor) in order for regular mouse movement to not highlight many splitters
+            float cur_size_0 = child_0->Size[axis];
+            float cur_size_1 = child_1->Size[axis];
+            float min_size_0 = resize_limits[0] - child_0->Pos[axis];
+            float min_size_1 = child_1->Pos[axis] + child_1->Size[axis] - resize_limits[1];
+            ImU32 bg_col = GetColorU32(ImGuiCol_WindowBg);
+            if (SplitterBehavior(bb, GetID("##Splitter"), axis, &cur_size_0, &cur_size_1, min_size_0, min_size_1, WINDOWS_HOVER_PADDING, WINDOWS_RESIZE_FROM_EDGES_FEEDBACK_TIMER, bg_col))
+            {
+                if (touching_nodes[0].Size > 0 && touching_nodes[1].Size > 0)
+                {
+                    child_0->Size[axis] = child_0->SizeRef[axis] = cur_size_0;
+                    child_1->Pos[axis] -= cur_size_1 - child_1->Size[axis];
+                    child_1->Size[axis] = child_1->SizeRef[axis] = cur_size_1;
+
+                    // Lock the size of every node that is a sibling of the node we are touching
+                    // This might be less desirable if we can merge sibling of a same axis into the same parental level.
+                    for (int side_n = 0; side_n < 2; side_n++)
+                        for (int touching_node_n = 0; touching_node_n < touching_nodes[side_n].Size; touching_node_n++)
+                        {
+                            ImGuiDockNode* touching_node = touching_nodes[side_n][touching_node_n];
+                            //ImDrawList* draw_list = node->HostWindow ? GetForegroundDrawList(node->HostWindow) : GetForegroundDrawList(GetMainViewport());
+                            //draw_list->AddRect(touching_node->Pos, touching_node->Pos + touching_node->Size, IM_COL32(255, 128, 0, 255));
+                            while (touching_node->ParentNode != node)
+                            {
+                                if (touching_node->ParentNode->SplitAxis == axis)
+                                {
+                                    // Mark other node so its size will be preserved during the upcoming call to DockNodeTreeUpdatePosSize().
+                                    ImGuiDockNode* node_to_preserve = touching_node->ParentNode->ChildNodes[side_n];
+                                    node_to_preserve->WantLockSizeOnce = true;
+                                    //draw_list->AddRect(touching_node->Pos, touching_node->Rect().Max, IM_COL32(255, 0, 0, 255));
+                                    //draw_list->AddRectFilled(node_to_preserve->Pos, node_to_preserve->Rect().Max, IM_COL32(0, 255, 0, 100));
+                                }
+                                touching_node = touching_node->ParentNode;
+                            }
+                        }
+
+                    DockNodeTreeUpdatePosSize(child_0, child_0->Pos, child_0->Size);
+                    DockNodeTreeUpdatePosSize(child_1, child_1->Pos, child_1->Size);
+                    MarkIniSettingsDirty();
+                }
+            }
+            PopID();
+        }
+    }
+
+    if (child_0->IsVisible)
+        DockNodeTreeUpdateSplitter(child_0);
+    if (child_1->IsVisible)
+        DockNodeTreeUpdateSplitter(child_1);
+}
+
+ImGuiDockNode* ImGui::DockNodeTreeFindFallbackLeafNode(ImGuiDockNode* node)
+{
+    if (node->IsLeafNode())
+        return node;
+    if (ImGuiDockNode* leaf_node = DockNodeTreeFindFallbackLeafNode(node->ChildNodes[0]))
+        return leaf_node;
+    if (ImGuiDockNode* leaf_node = DockNodeTreeFindFallbackLeafNode(node->ChildNodes[1]))
+        return leaf_node;
+    return NULL;
+}
+
+ImGuiDockNode* ImGui::DockNodeTreeFindVisibleNodeByPos(ImGuiDockNode* node, ImVec2 pos)
+{
+    if (!node->IsVisible)
+        return NULL;
+
+    const float dock_spacing = 0.0f;// g.Style.ItemInnerSpacing.x; // FIXME: Relation to DOCKING_SPLITTER_SIZE?
+    ImRect r(node->Pos, node->Pos + node->Size);
+    r.Expand(dock_spacing * 0.5f);
+    bool inside = r.Contains(pos);
+    if (!inside)
+        return NULL;
+
+    if (node->IsLeafNode())
+        return node;
+    if (ImGuiDockNode* hovered_node = DockNodeTreeFindVisibleNodeByPos(node->ChildNodes[0], pos))
+        return hovered_node;
+    if (ImGuiDockNode* hovered_node = DockNodeTreeFindVisibleNodeByPos(node->ChildNodes[1], pos))
+        return hovered_node;
+
+    // This means we are hovering over the splitter/spacing of a parent node
+    return node;
+}
+
+//-----------------------------------------------------------------------------
+// Docking: Public Functions (SetWindowDock, DockSpace, DockSpaceOverViewport)
+//-----------------------------------------------------------------------------
+// - SetWindowDock() [Internal]
+// - DockSpace()
+// - DockSpaceOverViewport()
+//-----------------------------------------------------------------------------
+
+// [Internal] Called via SetNextWindowDockID()
+void ImGui::SetWindowDock(ImGuiWindow* window, ImGuiID dock_id, ImGuiCond cond)
+{
+    // Test condition (NB: bit 0 is always true) and clear flags for next time
+    if (cond && (window->SetWindowDockAllowFlags & cond) == 0)
+        return;
+    window->SetWindowDockAllowFlags &= ~(ImGuiCond_Once | ImGuiCond_FirstUseEver | ImGuiCond_Appearing);
+
+    if (window->DockId == dock_id)
+        return;
+
+    // If the user attempt to set a dock id that is a split node, we'll dig within to find a suitable docking spot
+    ImGuiContext& g = *GImGui;
+    if (ImGuiDockNode* new_node = DockContextFindNodeByID(&g, dock_id))
+        if (new_node->IsSplitNode())
+        {
+            // Policy: Find central node or latest focused node. We first move back to our root node.
+            new_node = DockNodeGetRootNode(new_node);
+            if (new_node->CentralNode)
+            {
+                IM_ASSERT(new_node->CentralNode->IsCentralNode());
+                dock_id = new_node->CentralNode->ID;
+            }
+            else
+            {
+                dock_id = new_node->LastFocusedNodeId;
+            }
+        }
+
+    if (window->DockId == dock_id)
+        return;
+
+    if (window->DockNode)
+        DockNodeRemoveWindow(window->DockNode, window, 0);
+    window->DockId = dock_id;
+}
+
+// Create an explicit dockspace node within an existing window. Also expose dock node flags and creates a CentralNode by default.
+// The Central Node is always displayed even when empty and shrink/extend according to the requested size of its neighbors.
+// DockSpace() needs to be submitted _before_ any window they can host. If you use a dockspace, submit it early in your app.
+// When ImGuiDockNodeFlags_KeepAliveOnly is set, nothing is submitted in the current window (function may be called from any location).
+ImGuiID ImGui::DockSpace(ImGuiID dockspace_id, const ImVec2& size_arg, ImGuiDockNodeFlags flags, const ImGuiWindowClass* window_class)
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiWindow* window = GetCurrentWindowRead();
+    if (!(g.IO.ConfigFlags & ImGuiConfigFlags_DockingEnable))
+        return 0;
+
+    // Early out if parent window is hidden/collapsed
+    // This is faster but also DockNodeUpdateTabBar() relies on TabBarLayout() running (which won't if SkipItems=true) to set NextSelectedTabId = 0). See #2960.
+    // If for whichever reason this is causing problem we would need to ensure that DockNodeUpdateTabBar() ends up clearing NextSelectedTabId even if SkipItems=true.
+    if (window->SkipItems)
+        flags |= ImGuiDockNodeFlags_KeepAliveOnly;
+    if ((flags & ImGuiDockNodeFlags_KeepAliveOnly) == 0)
+        window = GetCurrentWindow(); // call to set window->WriteAccessed = true;
+
+    IM_ASSERT((flags & ImGuiDockNodeFlags_DockSpace) == 0);
+    IM_ASSERT(dockspace_id != 0);
+    ImGuiDockNode* node = DockContextFindNodeByID(&g, dockspace_id);
+    if (node == NULL)
+    {
+        IMGUI_DEBUG_LOG_DOCKING("[docking] DockSpace: dockspace node 0x%08X created\n", dockspace_id);
+        node = DockContextAddNode(&g, dockspace_id);
+        node->SetLocalFlags(ImGuiDockNodeFlags_CentralNode);
+    }
+    if (window_class && window_class->ClassId != node->WindowClass.ClassId)
+        IMGUI_DEBUG_LOG_DOCKING("[docking] DockSpace: dockspace node 0x%08X: setup WindowClass 0x%08X -> 0x%08X\n", dockspace_id, node->WindowClass.ClassId, window_class->ClassId);
+    node->SharedFlags = flags;
+    node->WindowClass = window_class ? *window_class : ImGuiWindowClass();
+
+    // When a DockSpace transitioned form implicit to explicit this may be called a second time
+    // It is possible that the node has already been claimed by a docked window which appeared before the DockSpace() node, so we overwrite IsDockSpace again.
+    if (node->LastFrameActive == g.FrameCount && !(flags & ImGuiDockNodeFlags_KeepAliveOnly))
+    {
+        IM_ASSERT(node->IsDockSpace() == false && "Cannot call DockSpace() twice a frame with the same ID");
+        node->SetLocalFlags(node->LocalFlags | ImGuiDockNodeFlags_DockSpace);
+        return dockspace_id;
+    }
+    node->SetLocalFlags(node->LocalFlags | ImGuiDockNodeFlags_DockSpace);
+
+    // Keep alive mode, this is allow windows docked into this node so stay docked even if they are not visible
+    if (flags & ImGuiDockNodeFlags_KeepAliveOnly)
+    {
+        node->LastFrameAlive = g.FrameCount;
+        return dockspace_id;
+    }
+
+    const ImVec2 content_avail = GetContentRegionAvail();
+    ImVec2 size = ImTrunc(size_arg);
+    if (size.x <= 0.0f)
+        size.x = ImMax(content_avail.x + size.x, 4.0f); // Arbitrary minimum child size (0.0f causing too much issues)
+    if (size.y <= 0.0f)
+        size.y = ImMax(content_avail.y + size.y, 4.0f);
+    IM_ASSERT(size.x > 0.0f && size.y > 0.0f);
+
+    node->Pos = window->DC.CursorPos;
+    node->Size = node->SizeRef = size;
+    SetNextWindowPos(node->Pos);
+    SetNextWindowSize(node->Size);
+    g.NextWindowData.PosUndock = false;
+
+    // FIXME-DOCK: Why do we need a child window to host a dockspace, could we host it in the existing window?
+    // FIXME-DOCK: What is the reason for not simply calling BeginChild()? (OK to have a reason but should be commented)
+    ImGuiWindowFlags window_flags = ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_DockNodeHost;
+    window_flags |= ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoCollapse | ImGuiWindowFlags_NoTitleBar;
+    window_flags |= ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoScrollWithMouse;
+    window_flags |= ImGuiWindowFlags_NoBackground;
+
+    char title[256];
+    ImFormatString(title, IM_ARRAYSIZE(title), "%s/DockSpace_%08X", window->Name, dockspace_id);
+
+    PushStyleVar(ImGuiStyleVar_ChildBorderSize, 0.0f);
+    Begin(title, NULL, window_flags);
+    PopStyleVar();
+
+    ImGuiWindow* host_window = g.CurrentWindow;
+    DockNodeSetupHostWindow(node, host_window);
+    host_window->ChildId = window->GetID(title);
+    node->OnlyNodeWithWindows = NULL;
+
+    IM_ASSERT(node->IsRootNode());
+
+    // We need to handle the rare case were a central node is missing.
+    // This can happen if the node was first created manually with DockBuilderAddNode() but _without_ the ImGuiDockNodeFlags_Dockspace.
+    // Doing it correctly would set the _CentralNode flags, which would then propagate according to subsequent split.
+    // It would also be ambiguous to attempt to assign a central node while there are split nodes, so we wait until there's a single node remaining.
+    // The specific sub-property of _CentralNode we are interested in recovering here is the "Don't delete when empty" property,
+    // as it doesn't make sense for an empty dockspace to not have this property.
+    if (node->IsLeafNode() && !node->IsCentralNode())
+        node->SetLocalFlags(node->LocalFlags | ImGuiDockNodeFlags_CentralNode);
+
+    // Update the node
+    DockNodeUpdate(node);
+
+    End();
+
+    ImRect bb(node->Pos, node->Pos + size);
+    ItemSize(size);
+    ItemAdd(bb, dockspace_id, NULL, ImGuiItemFlags_NoNav); // Not a nav point (could be, would need to draw the nav rect and replicate/refactor activation from BeginChild(), but seems like CTRL+Tab works better here?)
+    if ((g.LastItemData.StatusFlags & ImGuiItemStatusFlags_HoveredRect) && IsWindowChildOf(g.HoveredWindow, host_window, false, true)) // To fullfill IsItemHovered(), similar to EndChild()
+        g.LastItemData.StatusFlags |= ImGuiItemStatusFlags_HoveredWindow;
+
+    return dockspace_id;
+}
+
+// Tips: Use with ImGuiDockNodeFlags_PassthruCentralNode!
+// The limitation with this call is that your window won't have a local menu bar, but you can also use BeginMainMenuBar().
+// Even though we could pass window flags, it would also require the user to be able to call BeginMenuBar() somehow meaning we can't Begin/End in a single function.
+// If you really want a menu bar inside the same window as the one hosting the dockspace, you will need to copy this code somewhere and tweak it.
+ImGuiID ImGui::DockSpaceOverViewport(ImGuiID dockspace_id, const ImGuiViewport* viewport, ImGuiDockNodeFlags dockspace_flags, const ImGuiWindowClass* window_class)
+{
+    if (viewport == NULL)
+        viewport = GetMainViewport();
+
+    // Submit a window filling the entire viewport
+    SetNextWindowPos(viewport->WorkPos);
+    SetNextWindowSize(viewport->WorkSize);
+    SetNextWindowViewport(viewport->ID);
+
+    ImGuiWindowFlags host_window_flags = 0;
+    host_window_flags |= ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoCollapse | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoDocking;
+    host_window_flags |= ImGuiWindowFlags_NoBringToFrontOnFocus | ImGuiWindowFlags_NoNavFocus;
+    if (dockspace_flags & ImGuiDockNodeFlags_PassthruCentralNode)
+        host_window_flags |= ImGuiWindowFlags_NoBackground;
+
+    char label[32];
+    ImFormatString(label, IM_ARRAYSIZE(label), "WindowOverViewport_%08X", viewport->ID);
+
+    PushStyleVar(ImGuiStyleVar_WindowRounding, 0.0f);
+    PushStyleVar(ImGuiStyleVar_WindowBorderSize, 0.0f);
+    PushStyleVar(ImGuiStyleVar_WindowPadding, ImVec2(0.0f, 0.0f));
+    Begin(label, NULL, host_window_flags);
+    PopStyleVar(3);
+
+    // Submit the dockspace
+    if (dockspace_id == 0)
+        dockspace_id = GetID("DockSpace");
+    DockSpace(dockspace_id, ImVec2(0.0f, 0.0f), dockspace_flags, window_class);
+
+    End();
+
+    return dockspace_id;
+}
+
+//-----------------------------------------------------------------------------
+// Docking: Builder Functions
+//-----------------------------------------------------------------------------
+// Very early end-user API to manipulate dock nodes.
+// Only available in imgui_internal.h. Expect this API to change/break!
+// It is expected that those functions are all called _before_ the dockspace node submission.
+//-----------------------------------------------------------------------------
+// - DockBuilderDockWindow()
+// - DockBuilderGetNode()
+// - DockBuilderSetNodePos()
+// - DockBuilderSetNodeSize()
+// - DockBuilderAddNode()
+// - DockBuilderRemoveNode()
+// - DockBuilderRemoveNodeChildNodes()
+// - DockBuilderRemoveNodeDockedWindows()
+// - DockBuilderSplitNode()
+// - DockBuilderCopyNodeRec()
+// - DockBuilderCopyNode()
+// - DockBuilderCopyWindowSettings()
+// - DockBuilderCopyDockSpace()
+// - DockBuilderFinish()
+//-----------------------------------------------------------------------------
+
+void ImGui::DockBuilderDockWindow(const char* window_name, ImGuiID node_id)
+{
+    // We don't preserve relative order of multiple docked windows (by clearing DockOrder back to -1)
+    ImGuiContext& g = *GImGui; IM_UNUSED(g);
+    IMGUI_DEBUG_LOG_DOCKING("[docking] DockBuilderDockWindow '%s' to node 0x%08X\n", window_name, node_id);
+    ImGuiID window_id = ImHashStr(window_name);
+    if (ImGuiWindow* window = FindWindowByID(window_id))
+    {
+        // Apply to created window
+        ImGuiID prev_node_id = window->DockId;
+        SetWindowDock(window, node_id, ImGuiCond_Always);
+        if (window->DockId != prev_node_id)
+            window->DockOrder = -1;
+    }
+    else
+    {
+        // Apply to settings
+        ImGuiWindowSettings* settings = FindWindowSettingsByID(window_id);
+        if (settings == NULL)
+            settings = CreateNewWindowSettings(window_name);
+        if (settings->DockId != node_id)
+            settings->DockOrder = -1;
+        settings->DockId = node_id;
+    }
+}
+
+ImGuiDockNode* ImGui::DockBuilderGetNode(ImGuiID node_id)
+{
+    ImGuiContext& g = *GImGui;
+    return DockContextFindNodeByID(&g, node_id);
+}
+
+void ImGui::DockBuilderSetNodePos(ImGuiID node_id, ImVec2 pos)
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiDockNode* node = DockContextFindNodeByID(&g, node_id);
+    if (node == NULL)
+        return;
+    node->Pos = pos;
+    node->AuthorityForPos = ImGuiDataAuthority_DockNode;
+}
+
+void ImGui::DockBuilderSetNodeSize(ImGuiID node_id, ImVec2 size)
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiDockNode* node = DockContextFindNodeByID(&g, node_id);
+    if (node == NULL)
+        return;
+    IM_ASSERT(size.x > 0.0f && size.y > 0.0f);
+    node->Size = node->SizeRef = size;
+    node->AuthorityForSize = ImGuiDataAuthority_DockNode;
+}
+
+// Make sure to use the ImGuiDockNodeFlags_DockSpace flag to create a dockspace node! Otherwise this will create a floating node!
+// - Floating node: you can then call DockBuilderSetNodePos()/DockBuilderSetNodeSize() to position and size the floating node.
+// - Dockspace node: calling DockBuilderSetNodePos() is unnecessary.
+// - If you intend to split a node immediately after creation using DockBuilderSplitNode(), make sure to call DockBuilderSetNodeSize() beforehand!
+//   For various reason, the splitting code currently needs a base size otherwise space may not be allocated as precisely as you would expect.
+// - Use (id == 0) to let the system allocate a node identifier.
+// - Existing node with a same id will be removed.
+ImGuiID ImGui::DockBuilderAddNode(ImGuiID node_id, ImGuiDockNodeFlags flags)
+{
+    ImGuiContext& g = *GImGui; IM_UNUSED(g);
+    IMGUI_DEBUG_LOG_DOCKING("[docking] DockBuilderAddNode 0x%08X flags=%08X\n", node_id, flags);
+
+    if (node_id != 0)
+        DockBuilderRemoveNode(node_id);
+
+    ImGuiDockNode* node = NULL;
+    if (flags & ImGuiDockNodeFlags_DockSpace)
+    {
+        DockSpace(node_id, ImVec2(0, 0), (flags & ~ImGuiDockNodeFlags_DockSpace) | ImGuiDockNodeFlags_KeepAliveOnly);
+        node = DockContextFindNodeByID(&g, node_id);
+    }
+    else
+    {
+        node = DockContextAddNode(&g, node_id);
+        node->SetLocalFlags(flags);
+    }
+    node->LastFrameAlive = g.FrameCount;   // Set this otherwise BeginDocked will undock during the same frame.
+    return node->ID;
+}
+
+void ImGui::DockBuilderRemoveNode(ImGuiID node_id)
+{
+    ImGuiContext& g = *GImGui; IM_UNUSED(g);
+    IMGUI_DEBUG_LOG_DOCKING("[docking] DockBuilderRemoveNode 0x%08X\n", node_id);
+
+    ImGuiDockNode* node = DockContextFindNodeByID(&g, node_id);
+    if (node == NULL)
+        return;
+    DockBuilderRemoveNodeDockedWindows(node_id, true);
+    DockBuilderRemoveNodeChildNodes(node_id);
+    // Node may have moved or deleted if e.g. any merge happened
+    node = DockContextFindNodeByID(&g, node_id);
+    if (node == NULL)
+        return;
+    if (node->IsCentralNode() && node->ParentNode)
+        node->ParentNode->SetLocalFlags(node->ParentNode->LocalFlags | ImGuiDockNodeFlags_CentralNode);
+    DockContextRemoveNode(&g, node, true);
+}
+
+// root_id = 0 to remove all, root_id != 0 to remove child of given node.
+void ImGui::DockBuilderRemoveNodeChildNodes(ImGuiID root_id)
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiDockContext* dc = &g.DockContext;
+
+    ImGuiDockNode* root_node = root_id ? DockContextFindNodeByID(&g, root_id) : NULL;
+    if (root_id && root_node == NULL)
+        return;
+    bool has_central_node = false;
+
+    ImGuiDataAuthority backup_root_node_authority_for_pos = root_node ? root_node->AuthorityForPos : ImGuiDataAuthority_Auto;
+    ImGuiDataAuthority backup_root_node_authority_for_size = root_node ? root_node->AuthorityForSize : ImGuiDataAuthority_Auto;
+
+    // Process active windows
+    ImVector<ImGuiDockNode*> nodes_to_remove;
+    for (int n = 0; n < dc->Nodes.Data.Size; n++)
+        if (ImGuiDockNode* node = (ImGuiDockNode*)dc->Nodes.Data[n].val_p)
+        {
+            bool want_removal = (root_id == 0) || (node->ID != root_id && DockNodeGetRootNode(node)->ID == root_id);
+            if (want_removal)
+            {
+                if (node->IsCentralNode())
+                    has_central_node = true;
+                if (root_id != 0)
+                    DockContextQueueNotifyRemovedNode(&g, node);
+                if (root_node)
+                {
+                    DockNodeMoveWindows(root_node, node);
+                    DockSettingsRenameNodeReferences(node->ID, root_node->ID);
+                }
+                nodes_to_remove.push_back(node);
+            }
+        }
+
+    // DockNodeMoveWindows->DockNodeAddWindow will normally set those when reaching two windows (which is only adequate during interactive merge)
+    // Make sure we don't lose our current pos/size. (FIXME-DOCK: Consider tidying up that code in DockNodeAddWindow instead)
+    if (root_node)
+    {
+        root_node->AuthorityForPos = backup_root_node_authority_for_pos;
+        root_node->AuthorityForSize = backup_root_node_authority_for_size;
+    }
+
+    // Apply to settings
+    for (ImGuiWindowSettings* settings = g.SettingsWindows.begin(); settings != NULL; settings = g.SettingsWindows.next_chunk(settings))
+        if (ImGuiID window_settings_dock_id = settings->DockId)
+            for (int n = 0; n < nodes_to_remove.Size; n++)
+                if (nodes_to_remove[n]->ID == window_settings_dock_id)
+                {
+                    settings->DockId = root_id;
+                    break;
+                }
+
+    // Not really efficient, but easier to destroy a whole hierarchy considering DockContextRemoveNode is attempting to merge nodes
+    if (nodes_to_remove.Size > 1)
+        ImQsort(nodes_to_remove.Data, nodes_to_remove.Size, sizeof(ImGuiDockNode*), DockNodeComparerDepthMostFirst);
+    for (int n = 0; n < nodes_to_remove.Size; n++)
+        DockContextRemoveNode(&g, nodes_to_remove[n], false);
+
+    if (root_id == 0)
+    {
+        dc->Nodes.Clear();
+        dc->Requests.clear();
+    }
+    else if (has_central_node)
+    {
+        root_node->CentralNode = root_node;
+        root_node->SetLocalFlags(root_node->LocalFlags | ImGuiDockNodeFlags_CentralNode);
+    }
+}
+
+void ImGui::DockBuilderRemoveNodeDockedWindows(ImGuiID root_id, bool clear_settings_refs)
+{
+    // Clear references in settings
+    ImGuiContext& g = *GImGui;
+    if (clear_settings_refs)
+    {
+        for (ImGuiWindowSettings* settings = g.SettingsWindows.begin(); settings != NULL; settings = g.SettingsWindows.next_chunk(settings))
+        {
+            bool want_removal = (root_id == 0) || (settings->DockId == root_id);
+            if (!want_removal && settings->DockId != 0)
+                if (ImGuiDockNode* node = DockContextFindNodeByID(&g, settings->DockId))
+                    if (DockNodeGetRootNode(node)->ID == root_id)
+                        want_removal = true;
+            if (want_removal)
+                settings->DockId = 0;
+        }
+    }
+
+    // Clear references in windows
+    for (int n = 0; n < g.Windows.Size; n++)
+    {
+        ImGuiWindow* window = g.Windows[n];
+        bool want_removal = (root_id == 0) || (window->DockNode && DockNodeGetRootNode(window->DockNode)->ID == root_id) || (window->DockNodeAsHost && window->DockNodeAsHost->ID == root_id);
+        if (want_removal)
+        {
+            const ImGuiID backup_dock_id = window->DockId;
+            IM_UNUSED(backup_dock_id);
+            DockContextProcessUndockWindow(&g, window, clear_settings_refs);
+            if (!clear_settings_refs)
+                IM_ASSERT(window->DockId == backup_dock_id);
+        }
+    }
+}
+
+// If 'out_id_at_dir' or 'out_id_at_opposite_dir' are non NULL, the function will write out the ID of the two new nodes created.
+// Return value is ID of the node at the specified direction, so same as (*out_id_at_dir) if that pointer is set.
+// FIXME-DOCK: We are not exposing nor using split_outer.
+ImGuiID ImGui::DockBuilderSplitNode(ImGuiID id, ImGuiDir split_dir, float size_ratio_for_node_at_dir, ImGuiID* out_id_at_dir, ImGuiID* out_id_at_opposite_dir)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(split_dir != ImGuiDir_None);
+    IMGUI_DEBUG_LOG_DOCKING("[docking] DockBuilderSplitNode: node 0x%08X, split_dir %d\n", id, split_dir);
+
+    ImGuiDockNode* node = DockContextFindNodeByID(&g, id);
+    if (node == NULL)
+    {
+        IM_ASSERT(node != NULL);
+        return 0;
+    }
+
+    IM_ASSERT(!node->IsSplitNode()); // Assert if already Split
+
+    ImGuiDockRequest req;
+    req.Type = ImGuiDockRequestType_Split;
+    req.DockTargetWindow = NULL;
+    req.DockTargetNode = node;
+    req.DockPayload = NULL;
+    req.DockSplitDir = split_dir;
+    req.DockSplitRatio = ImSaturate((split_dir == ImGuiDir_Left || split_dir == ImGuiDir_Up) ? size_ratio_for_node_at_dir : 1.0f - size_ratio_for_node_at_dir);
+    req.DockSplitOuter = false;
+    DockContextProcessDock(&g, &req);
+
+    ImGuiID id_at_dir = node->ChildNodes[(split_dir == ImGuiDir_Left || split_dir == ImGuiDir_Up) ? 0 : 1]->ID;
+    ImGuiID id_at_opposite_dir = node->ChildNodes[(split_dir == ImGuiDir_Left || split_dir == ImGuiDir_Up) ? 1 : 0]->ID;
+    if (out_id_at_dir)
+        *out_id_at_dir = id_at_dir;
+    if (out_id_at_opposite_dir)
+        *out_id_at_opposite_dir = id_at_opposite_dir;
+    return id_at_dir;
+}
+
+static ImGuiDockNode* DockBuilderCopyNodeRec(ImGuiDockNode* src_node, ImGuiID dst_node_id_if_known, ImVector<ImGuiID>* out_node_remap_pairs)
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiDockNode* dst_node = ImGui::DockContextAddNode(&g, dst_node_id_if_known);
+    dst_node->SharedFlags = src_node->SharedFlags;
+    dst_node->LocalFlags = src_node->LocalFlags;
+    dst_node->LocalFlagsInWindows = ImGuiDockNodeFlags_None;
+    dst_node->Pos = src_node->Pos;
+    dst_node->Size = src_node->Size;
+    dst_node->SizeRef = src_node->SizeRef;
+    dst_node->SplitAxis = src_node->SplitAxis;
+    dst_node->UpdateMergedFlags();
+
+    out_node_remap_pairs->push_back(src_node->ID);
+    out_node_remap_pairs->push_back(dst_node->ID);
+
+    for (int child_n = 0; child_n < IM_ARRAYSIZE(src_node->ChildNodes); child_n++)
+        if (src_node->ChildNodes[child_n])
+        {
+            dst_node->ChildNodes[child_n] = DockBuilderCopyNodeRec(src_node->ChildNodes[child_n], 0, out_node_remap_pairs);
+            dst_node->ChildNodes[child_n]->ParentNode = dst_node;
+        }
+
+    IMGUI_DEBUG_LOG_DOCKING("[docking] Fork node %08X -> %08X (%d childs)\n", src_node->ID, dst_node->ID, dst_node->IsSplitNode() ? 2 : 0);
+    return dst_node;
+}
+
+void ImGui::DockBuilderCopyNode(ImGuiID src_node_id, ImGuiID dst_node_id, ImVector<ImGuiID>* out_node_remap_pairs)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(src_node_id != 0);
+    IM_ASSERT(dst_node_id != 0);
+    IM_ASSERT(out_node_remap_pairs != NULL);
+
+    DockBuilderRemoveNode(dst_node_id);
+
+    ImGuiDockNode* src_node = DockContextFindNodeByID(&g, src_node_id);
+    IM_ASSERT(src_node != NULL);
+
+    out_node_remap_pairs->clear();
+    DockBuilderCopyNodeRec(src_node, dst_node_id, out_node_remap_pairs);
+
+    IM_ASSERT((out_node_remap_pairs->Size % 2) == 0);
+}
+
+void ImGui::DockBuilderCopyWindowSettings(const char* src_name, const char* dst_name)
+{
+    ImGuiWindow* src_window = FindWindowByName(src_name);
+    if (src_window == NULL)
+        return;
+    if (ImGuiWindow* dst_window = FindWindowByName(dst_name))
+    {
+        dst_window->Pos = src_window->Pos;
+        dst_window->Size = src_window->Size;
+        dst_window->SizeFull = src_window->SizeFull;
+        dst_window->Collapsed = src_window->Collapsed;
+    }
+    else
+    {
+        ImGuiWindowSettings* dst_settings = FindWindowSettingsByID(ImHashStr(dst_name));
+        if (!dst_settings)
+            dst_settings = CreateNewWindowSettings(dst_name);
+        ImVec2ih window_pos_2ih = ImVec2ih(src_window->Pos);
+        if (src_window->ViewportId != 0 && src_window->ViewportId != IMGUI_VIEWPORT_DEFAULT_ID)
+        {
+            dst_settings->ViewportPos = window_pos_2ih;
+            dst_settings->ViewportId = src_window->ViewportId;
+            dst_settings->Pos = ImVec2ih(0, 0);
+        }
+        else
+        {
+            dst_settings->Pos = window_pos_2ih;
+        }
+        dst_settings->Size = ImVec2ih(src_window->SizeFull);
+        dst_settings->Collapsed = src_window->Collapsed;
+    }
+}
+
+// FIXME: Will probably want to change this signature, in particular how the window remapping pairs are passed.
+void ImGui::DockBuilderCopyDockSpace(ImGuiID src_dockspace_id, ImGuiID dst_dockspace_id, ImVector<const char*>* in_window_remap_pairs)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(src_dockspace_id != 0);
+    IM_ASSERT(dst_dockspace_id != 0);
+    IM_ASSERT(in_window_remap_pairs != NULL);
+    IM_ASSERT((in_window_remap_pairs->Size % 2) == 0);
+
+    // Duplicate entire dock
+    // FIXME: When overwriting dst_dockspace_id, windows that aren't part of our dockspace window class but that are docked in a same node will be split apart,
+    // whereas we could attempt to at least keep them together in a new, same floating node.
+    ImVector<ImGuiID> node_remap_pairs;
+    DockBuilderCopyNode(src_dockspace_id, dst_dockspace_id, &node_remap_pairs);
+
+    // Attempt to transition all the upcoming windows associated to dst_dockspace_id into the newly created hierarchy of dock nodes
+    // (The windows associated to src_dockspace_id are staying in place)
+    ImVector<ImGuiID> src_windows;
+    for (int remap_window_n = 0; remap_window_n < in_window_remap_pairs->Size; remap_window_n += 2)
+    {
+        const char* src_window_name = (*in_window_remap_pairs)[remap_window_n];
+        const char* dst_window_name = (*in_window_remap_pairs)[remap_window_n + 1];
+        ImGuiID src_window_id = ImHashStr(src_window_name);
+        src_windows.push_back(src_window_id);
+
+        // Search in the remapping tables
+        ImGuiID src_dock_id = 0;
+        if (ImGuiWindow* src_window = FindWindowByID(src_window_id))
+            src_dock_id = src_window->DockId;
+        else if (ImGuiWindowSettings* src_window_settings = FindWindowSettingsByID(src_window_id))
+            src_dock_id = src_window_settings->DockId;
+        ImGuiID dst_dock_id = 0;
+        for (int dock_remap_n = 0; dock_remap_n < node_remap_pairs.Size; dock_remap_n += 2)
+            if (node_remap_pairs[dock_remap_n] == src_dock_id)
+            {
+                dst_dock_id = node_remap_pairs[dock_remap_n + 1];
+                //node_remap_pairs[dock_remap_n] = node_remap_pairs[dock_remap_n + 1] = 0; // Clear
+                break;
+            }
+
+        if (dst_dock_id != 0)
+        {
+            // Docked windows gets redocked into the new node hierarchy.
+            IMGUI_DEBUG_LOG_DOCKING("[docking] Remap live window '%s' 0x%08X -> '%s' 0x%08X\n", src_window_name, src_dock_id, dst_window_name, dst_dock_id);
+            DockBuilderDockWindow(dst_window_name, dst_dock_id);
+        }
+        else
+        {
+            // Floating windows gets their settings transferred (regardless of whether the new window already exist or not)
+            // When this is leading to a Copy and not a Move, we would get two overlapping floating windows. Could we possibly dock them together?
+            IMGUI_DEBUG_LOG_DOCKING("[docking] Remap window settings '%s' -> '%s'\n", src_window_name, dst_window_name);
+            DockBuilderCopyWindowSettings(src_window_name, dst_window_name);
+        }
+    }
+
+    // Anything else in the source nodes of 'node_remap_pairs' are windows that are not included in the remapping list.
+    // Find those windows and move to them to the cloned dock node. This may be optional?
+    // Dock those are a second step as undocking would invalidate source dock nodes.
+    struct DockRemainingWindowTask { ImGuiWindow* Window; ImGuiID DockId; DockRemainingWindowTask(ImGuiWindow* window, ImGuiID dock_id) { Window = window; DockId = dock_id; } };
+    ImVector<DockRemainingWindowTask> dock_remaining_windows;
+    for (int dock_remap_n = 0; dock_remap_n < node_remap_pairs.Size; dock_remap_n += 2)
+        if (ImGuiID src_dock_id = node_remap_pairs[dock_remap_n])
+        {
+            ImGuiID dst_dock_id = node_remap_pairs[dock_remap_n + 1];
+            ImGuiDockNode* node = DockBuilderGetNode(src_dock_id);
+            for (int window_n = 0; window_n < node->Windows.Size; window_n++)
+            {
+                ImGuiWindow* window = node->Windows[window_n];
+                if (src_windows.contains(window->ID))
+                    continue;
+
+                // Docked windows gets redocked into the new node hierarchy.
+                IMGUI_DEBUG_LOG_DOCKING("[docking] Remap window '%s' %08X -> %08X\n", window->Name, src_dock_id, dst_dock_id);
+                dock_remaining_windows.push_back(DockRemainingWindowTask(window, dst_dock_id));
+            }
+        }
+    for (const DockRemainingWindowTask& task : dock_remaining_windows)
+        DockBuilderDockWindow(task.Window->Name, task.DockId);
+}
+
+// FIXME-DOCK: This is awkward because in series of split user is likely to loose access to its root node.
+void ImGui::DockBuilderFinish(ImGuiID root_id)
+{
+    ImGuiContext& g = *GImGui;
+    //DockContextRebuild(&g);
+    DockContextBuildAddWindowsToNodes(&g, root_id);
+}
+
+//-----------------------------------------------------------------------------
+// Docking: Begin/End Support Functions (called from Begin/End)
+//-----------------------------------------------------------------------------
+// - GetWindowAlwaysWantOwnTabBar()
+// - DockContextBindNodeToWindow()
+// - BeginDocked()
+// - BeginDockableDragDropSource()
+// - BeginDockableDragDropTarget()
+//-----------------------------------------------------------------------------
+
+bool ImGui::GetWindowAlwaysWantOwnTabBar(ImGuiWindow* window)
+{
+    ImGuiContext& g = *GImGui;
+    if (g.IO.ConfigDockingAlwaysTabBar || window->WindowClass.DockingAlwaysTabBar)
+        if ((window->Flags & (ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoDocking)) == 0)
+            if (!window->IsFallbackWindow)    // We don't support AlwaysTabBar on the fallback/implicit window to avoid unused dock-node overhead/noise
+                return true;
+    return false;
+}
+
+static ImGuiDockNode* ImGui::DockContextBindNodeToWindow(ImGuiContext* ctx, ImGuiWindow* window)
+{
+    ImGuiContext& g = *ctx;
+    ImGuiDockNode* node = DockContextFindNodeByID(ctx, window->DockId);
+    IM_ASSERT(window->DockNode == NULL);
+
+    // We should not be docking into a split node (SetWindowDock should avoid this)
+    if (node && node->IsSplitNode())
+    {
+        DockContextProcessUndockWindow(ctx, window);
+        return NULL;
+    }
+
+    // Create node
+    if (node == NULL)
+    {
+        node = DockContextAddNode(ctx, window->DockId);
+        node->AuthorityForPos = node->AuthorityForSize = node->AuthorityForViewport = ImGuiDataAuthority_Window;
+        node->LastFrameAlive = g.FrameCount;
+    }
+
+    // If the node just turned visible and is part of a hierarchy, it doesn't have a Size assigned by DockNodeTreeUpdatePosSize() yet,
+    // so we're forcing a Pos/Size update from the first ancestor that is already visible (often it will be the root node).
+    // If we don't do this, the window will be assigned a zero-size on its first frame, which won't ideally warm up the layout.
+    // This is a little wonky because we don't normally update the Pos/Size of visible node mid-frame.
+    if (!node->IsVisible)
+    {
+        ImGuiDockNode* ancestor_node = node;
+        while (!ancestor_node->IsVisible && ancestor_node->ParentNode)
+            ancestor_node = ancestor_node->ParentNode;
+        IM_ASSERT(ancestor_node->Size.x > 0.0f && ancestor_node->Size.y > 0.0f);
+        DockNodeUpdateHasCentralNodeChild(DockNodeGetRootNode(ancestor_node));
+        DockNodeTreeUpdatePosSize(ancestor_node, ancestor_node->Pos, ancestor_node->Size, node);
+    }
+
+    // Add window to node
+    bool node_was_visible = node->IsVisible;
+    DockNodeAddWindow(node, window, true);
+    node->IsVisible = node_was_visible; // Don't mark visible right away (so DockContextEndFrame() doesn't render it, maybe other side effects? will see)
+    IM_ASSERT(node == window->DockNode);
+    return node;
+}
+
+static void StoreDockStyleForWindow(ImGuiWindow* window)
+{
+    ImGuiContext& g = *GImGui;
+    for (int color_n = 0; color_n < ImGuiWindowDockStyleCol_COUNT; color_n++)
+        window->DockStyle.Colors[color_n] = ImGui::ColorConvertFloat4ToU32(g.Style.Colors[GWindowDockStyleColors[color_n]]);
+}
+
+void ImGui::BeginDocked(ImGuiWindow* window, bool* p_open)
+{
+    ImGuiContext& g = *GImGui;
+
+    // Clear fields ahead so most early-out paths don't have to do it
+    window->DockIsActive = window->DockNodeIsVisible = window->DockTabIsVisible = false;
+
+    const bool auto_dock_node = GetWindowAlwaysWantOwnTabBar(window);
+    if (auto_dock_node)
+    {
+        if (window->DockId == 0)
+        {
+            IM_ASSERT(window->DockNode == NULL);
+            window->DockId = DockContextGenNodeID(&g);
+        }
+    }
+    else
+    {
+        // Calling SetNextWindowPos() undock windows by default (by setting PosUndock)
+        bool want_undock = false;
+        want_undock |= (window->Flags & ImGuiWindowFlags_NoDocking) != 0;
+        want_undock |= (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasPos) && (window->SetWindowPosAllowFlags & g.NextWindowData.PosCond) && g.NextWindowData.PosUndock;
+        if (want_undock)
+        {
+            DockContextProcessUndockWindow(&g, window);
+            return;
+        }
+    }
+
+    // Bind to our dock node
+    ImGuiDockNode* node = window->DockNode;
+    if (node != NULL)
+        IM_ASSERT(window->DockId == node->ID);
+    if (window->DockId != 0 && node == NULL)
+    {
+        node = DockContextBindNodeToWindow(&g, window);
+        if (node == NULL)
+            return;
+    }
+
+#if 0
+    // Undock if the ImGuiDockNodeFlags_NoDockingInCentralNode got set
+    if (node->IsCentralNode && (node->Flags & ImGuiDockNodeFlags_NoDockingInCentralNode))
+    {
+        DockContextProcessUndockWindow(ctx, window);
+        return;
+    }
+#endif
+
+    // Undock if our dockspace node disappeared
+    // Note how we are testing for LastFrameAlive and NOT LastFrameActive. A DockSpace node can be maintained alive while being inactive with ImGuiDockNodeFlags_KeepAliveOnly.
+    if (node->LastFrameAlive < g.FrameCount)
+    {
+        // If the window has been orphaned, transition the docknode to an implicit node processed in DockContextNewFrameUpdateDocking()
+        ImGuiDockNode* root_node = DockNodeGetRootNode(node);
+        if (root_node->LastFrameAlive < g.FrameCount)
+            DockContextProcessUndockWindow(&g, window);
+        else
+            window->DockIsActive = true;
+        return;
+    }
+
+    // Store style overrides
+    StoreDockStyleForWindow(window);
+
+    // Fast path return. It is common for windows to hold on a persistent DockId but be the only visible window,
+    // and never create neither a host window neither a tab bar.
+    // FIXME-DOCK: replace ->HostWindow NULL compare with something more explicit (~was initially intended as a first frame test)
+    if (node->HostWindow == NULL)
+    {
+        if (node->State == ImGuiDockNodeState_HostWindowHiddenBecauseWindowsAreResizing)
+            window->DockIsActive = true;
+        if (node->Windows.Size > 1 && window->Appearing) // Only hide appearing window
+            DockNodeHideWindowDuringHostWindowCreation(window);
+        return;
+    }
+
+    // We can have zero-sized nodes (e.g. children of a small-size dockspace)
+    IM_ASSERT(node->HostWindow);
+    IM_ASSERT(node->IsLeafNode());
+    IM_ASSERT(node->Size.x >= 0.0f && node->Size.y >= 0.0f);
+    node->State = ImGuiDockNodeState_HostWindowVisible;
+
+    // Undock if we are submitted earlier than the host window
+    if (!(node->MergedFlags & ImGuiDockNodeFlags_KeepAliveOnly) && window->BeginOrderWithinContext < node->HostWindow->BeginOrderWithinContext)
+    {
+        DockContextProcessUndockWindow(&g, window);
+        return;
+    }
+
+    // Position/Size window
+    SetNextWindowPos(node->Pos);
+    SetNextWindowSize(node->Size);
+    g.NextWindowData.PosUndock = false; // Cancel implicit undocking of SetNextWindowPos()
+    window->DockIsActive = true;
+    window->DockNodeIsVisible = true;
+    window->DockTabIsVisible = false;
+    if (node->MergedFlags & ImGuiDockNodeFlags_KeepAliveOnly)
+        return;
+
+    // When the window is selected we mark it as visible.
+    if (node->VisibleWindow == window)
+        window->DockTabIsVisible = true;
+
+    // Update window flag
+    IM_ASSERT((window->Flags & ImGuiWindowFlags_ChildWindow) == 0);
+    window->Flags |= ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_NoResize;
+    window->ChildFlags |= ImGuiChildFlags_AlwaysUseWindowPadding;
+    if (node->IsHiddenTabBar() || node->IsNoTabBar())
+        window->Flags |= ImGuiWindowFlags_NoTitleBar;
+    else
+        window->Flags &= ~ImGuiWindowFlags_NoTitleBar;      // Clear the NoTitleBar flag in case the user set it: confusingly enough we need a title bar height so we are correctly offset, but it won't be displayed!
+
+    // Save new dock order only if the window has been visible once already
+    // This allows multiple windows to be created in the same frame and have their respective dock orders preserved.
+    if (node->TabBar && window->WasActive)
+        window->DockOrder = (short)DockNodeGetTabOrder(window);
+
+    if ((node->WantCloseAll || node->WantCloseTabId == window->TabId) && p_open != NULL)
+        *p_open = false;
+
+    // Update ChildId to allow returning from Child to Parent with Escape
+    ImGuiWindow* parent_window = window->DockNode->HostWindow;
+    window->ChildId = parent_window->GetID(window->Name);
+}
+
+void ImGui::BeginDockableDragDropSource(ImGuiWindow* window)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(g.ActiveId == window->MoveId);
+    IM_ASSERT(g.MovingWindow == window);
+    IM_ASSERT(g.CurrentWindow == window);
+
+    // 0: Hold SHIFT to disable docking, 1: Hold SHIFT to enable docking.
+    if (g.IO.ConfigDockingWithShift != g.IO.KeyShift)
+    {
+        // When ConfigDockingWithShift is set, display a tooltip to increase UI affordance.
+        // We cannot set for HoveredWindowUnderMovingWindow != NULL here, as it is only valid/useful when drag and drop is already active
+        // (because of the 'is_mouse_dragging_with_an_expected_destination' logic in UpdateViewportsNewFrame() function)
+        IM_ASSERT(g.NextWindowData.Flags == 0);
+        if (g.IO.ConfigDockingWithShift && g.MouseStationaryTimer >= 1.0f && g.ActiveId >= 1.0f)
+            SetTooltip("%s", LocalizeGetMsg(ImGuiLocKey_DockingHoldShiftToDock));
+        return;
+    }
+
+    g.LastItemData.ID = window->MoveId;
+    window = window->RootWindowDockTree;
+    IM_ASSERT((window->Flags & ImGuiWindowFlags_NoDocking) == 0);
+    bool is_drag_docking = (g.IO.ConfigDockingWithShift) || ImRect(0, 0, window->SizeFull.x, GetFrameHeight()).Contains(g.ActiveIdClickOffset); // FIXME-DOCKING: Need to make this stateful and explicit
+    if (is_drag_docking && BeginDragDropSource(ImGuiDragDropFlags_SourceNoPreviewTooltip | ImGuiDragDropFlags_SourceNoHoldToOpenOthers | ImGuiDragDropFlags_SourceAutoExpirePayload))
+    {
+        SetDragDropPayload(IMGUI_PAYLOAD_TYPE_WINDOW, &window, sizeof(window));
+        EndDragDropSource();
+        StoreDockStyleForWindow(window); // Store style overrides while dragging (even when not docked) because docking preview may need it.
+    }
+}
+
+void ImGui::BeginDockableDragDropTarget(ImGuiWindow* window)
+{
+    ImGuiContext& g = *GImGui;
+
+    //IM_ASSERT(window->RootWindowDockTree == window); // May also be a DockSpace
+    IM_ASSERT((window->Flags & ImGuiWindowFlags_NoDocking) == 0);
+    if (!g.DragDropActive)
+        return;
+    //GetForegroundDrawList(window)->AddRect(window->Pos, window->Pos + window->Size, IM_COL32(255, 255, 0, 255));
+    if (!BeginDragDropTargetCustom(window->Rect(), window->ID))
+        return;
+
+    // Peek into the payload before calling AcceptDragDropPayload() so we can handle overlapping dock nodes with filtering
+    // (this is a little unusual pattern, normally most code would call AcceptDragDropPayload directly)
+    const ImGuiPayload* payload = &g.DragDropPayload;
+    if (!payload->IsDataType(IMGUI_PAYLOAD_TYPE_WINDOW) || !DockNodeIsDropAllowed(window, *(ImGuiWindow**)payload->Data))
+    {
+        EndDragDropTarget();
+        return;
+    }
+
+    ImGuiWindow* payload_window = *(ImGuiWindow**)payload->Data;
+    if (AcceptDragDropPayload(IMGUI_PAYLOAD_TYPE_WINDOW, ImGuiDragDropFlags_AcceptBeforeDelivery | ImGuiDragDropFlags_AcceptNoDrawDefaultRect))
+    {
+        // Select target node
+        // (Important: we cannot use g.HoveredDockNode here! Because each of our target node have filters based on payload, each candidate drop target will do its own evaluation)
+        bool dock_into_floating_window = false;
+        ImGuiDockNode* node = NULL;
+        if (window->DockNodeAsHost)
+        {
+            // Cannot assume that node will != NULL even though we passed the rectangle test: it depends on padding/spacing handled by DockNodeTreeFindVisibleNodeByPos().
+            node = DockNodeTreeFindVisibleNodeByPos(window->DockNodeAsHost, g.IO.MousePos);
+
+            // There is an edge case when docking into a dockspace which only has _inactive_ nodes (because none of the windows are active)
+            // In this case we need to fallback into any leaf mode, possibly the central node.
+            // FIXME-20181220: We should not have to test for IsLeafNode() here but we have another bug to fix first.
+            if (node && node->IsDockSpace() && node->IsRootNode())
+                node = (node->CentralNode && node->IsLeafNode()) ? node->CentralNode : DockNodeTreeFindFallbackLeafNode(node);
+        }
+        else
+        {
+            if (window->DockNode)
+                node = window->DockNode;
+            else
+                dock_into_floating_window = true; // Dock into a regular window
+        }
+
+        const ImRect explicit_target_rect = (node && node->TabBar && !node->IsHiddenTabBar() && !node->IsNoTabBar()) ? node->TabBar->BarRect : ImRect(window->Pos, window->Pos + ImVec2(window->Size.x, GetFrameHeight()));
+        const bool is_explicit_target = g.IO.ConfigDockingWithShift || IsMouseHoveringRect(explicit_target_rect.Min, explicit_target_rect.Max);
+
+        // Preview docking request and find out split direction/ratio
+        //const bool do_preview = true;     // Ignore testing for payload->IsPreview() which removes one frame of delay, but breaks overlapping drop targets within the same window.
+        const bool do_preview = payload->IsPreview() || payload->IsDelivery();
+        if (do_preview && (node != NULL || dock_into_floating_window))
+        {
+            // If we have a non-leaf node it means we are hovering the border of a parent node, in which case only outer markers will appear.
+            ImGuiDockPreviewData split_inner;
+            ImGuiDockPreviewData split_outer;
+            ImGuiDockPreviewData* split_data = &split_inner;
+            if (node && (node->ParentNode || node->IsCentralNode() || !node->IsLeafNode()))
+                if (ImGuiDockNode* root_node = DockNodeGetRootNode(node))
+                {
+                    DockNodePreviewDockSetup(window, root_node, payload_window, NULL, &split_outer, is_explicit_target, true);
+                    if (split_outer.IsSplitDirExplicit)
+                        split_data = &split_outer;
+                }
+            if (!node || node->IsLeafNode())
+                DockNodePreviewDockSetup(window, node, payload_window, NULL, &split_inner, is_explicit_target, false);
+            if (split_data == &split_outer)
+                split_inner.IsDropAllowed = false;
+
+            // Draw inner then outer, so that previewed tab (in inner data) will be behind the outer drop boxes
+            DockNodePreviewDockRender(window, node, payload_window, &split_inner);
+            DockNodePreviewDockRender(window, node, payload_window, &split_outer);
+
+            // Queue docking request
+            if (split_data->IsDropAllowed && payload->IsDelivery())
+                DockContextQueueDock(&g, window, split_data->SplitNode, payload_window, split_data->SplitDir, split_data->SplitRatio, split_data == &split_outer);
+        }
+    }
+    EndDragDropTarget();
+}
+
+//-----------------------------------------------------------------------------
+// Docking: Settings
+//-----------------------------------------------------------------------------
+// - DockSettingsRenameNodeReferences()
+// - DockSettingsRemoveNodeReferences()
+// - DockSettingsFindNodeSettings()
+// - DockSettingsHandler_ApplyAll()
+// - DockSettingsHandler_ReadOpen()
+// - DockSettingsHandler_ReadLine()
+// - DockSettingsHandler_DockNodeToSettings()
+// - DockSettingsHandler_WriteAll()
+//-----------------------------------------------------------------------------
+
+static void ImGui::DockSettingsRenameNodeReferences(ImGuiID old_node_id, ImGuiID new_node_id)
+{
+    ImGuiContext& g = *GImGui;
+    IMGUI_DEBUG_LOG_DOCKING("[docking] DockSettingsRenameNodeReferences: from 0x%08X -> to 0x%08X\n", old_node_id, new_node_id);
+    for (int window_n = 0; window_n < g.Windows.Size; window_n++)
+    {
+        ImGuiWindow* window = g.Windows[window_n];
+        if (window->DockId == old_node_id && window->DockNode == NULL)
+            window->DockId = new_node_id;
+    }
+    //// FIXME-OPT: We could remove this loop by storing the index in the map
+    for (ImGuiWindowSettings* settings = g.SettingsWindows.begin(); settings != NULL; settings = g.SettingsWindows.next_chunk(settings))
+        if (settings->DockId == old_node_id)
+            settings->DockId = new_node_id;
+}
+
+// Remove references stored in ImGuiWindowSettings to the given ImGuiDockNodeSettings
+static void ImGui::DockSettingsRemoveNodeReferences(ImGuiID* node_ids, int node_ids_count)
+{
+    ImGuiContext& g = *GImGui;
+    int found = 0;
+    //// FIXME-OPT: We could remove this loop by storing the index in the map
+    for (ImGuiWindowSettings* settings = g.SettingsWindows.begin(); settings != NULL; settings = g.SettingsWindows.next_chunk(settings))
+        for (int node_n = 0; node_n < node_ids_count; node_n++)
+            if (settings->DockId == node_ids[node_n])
+            {
+                settings->DockId = 0;
+                settings->DockOrder = -1;
+                if (++found < node_ids_count)
+                    break;
+                return;
+            }
+}
+
+static ImGuiDockNodeSettings* ImGui::DockSettingsFindNodeSettings(ImGuiContext* ctx, ImGuiID id)
+{
+    // FIXME-OPT
+    ImGuiDockContext* dc = &ctx->DockContext;
+    for (int n = 0; n < dc->NodesSettings.Size; n++)
+        if (dc->NodesSettings[n].ID == id)
+            return &dc->NodesSettings[n];
+    return NULL;
+}
+
+// Clear settings data
+static void ImGui::DockSettingsHandler_ClearAll(ImGuiContext* ctx, ImGuiSettingsHandler*)
+{
+    ImGuiDockContext* dc = &ctx->DockContext;
+    dc->NodesSettings.clear();
+    DockContextClearNodes(ctx, 0, true);
+}
+
+// Recreate nodes based on settings data
+static void ImGui::DockSettingsHandler_ApplyAll(ImGuiContext* ctx, ImGuiSettingsHandler*)
+{
+    // Prune settings at boot time only
+    ImGuiDockContext* dc = &ctx->DockContext;
+    if (ctx->Windows.Size == 0)
+        DockContextPruneUnusedSettingsNodes(ctx);
+    DockContextBuildNodesFromSettings(ctx, dc->NodesSettings.Data, dc->NodesSettings.Size);
+    DockContextBuildAddWindowsToNodes(ctx, 0);
+}
+
+static void* ImGui::DockSettingsHandler_ReadOpen(ImGuiContext*, ImGuiSettingsHandler*, const char* name)
+{
+    if (strcmp(name, "Data") != 0)
+        return NULL;
+    return (void*)1;
+}
+
+static void ImGui::DockSettingsHandler_ReadLine(ImGuiContext* ctx, ImGuiSettingsHandler*, void*, const char* line)
+{
+    char c = 0;
+    int x = 0, y = 0;
+    int r = 0;
+
+    // Parsing, e.g.
+    // " DockNode   ID=0x00000001 Pos=383,193 Size=201,322 Split=Y,0.506 "
+    // "   DockNode ID=0x00000002 Parent=0x00000001 "
+    // Important: this code expect currently fields in a fixed order.
+    ImGuiDockNodeSettings node;
+    line = ImStrSkipBlank(line);
+    if      (strncmp(line, "DockNode", 8) == 0)  { line = ImStrSkipBlank(line + strlen("DockNode")); }
+    else if (strncmp(line, "DockSpace", 9) == 0) { line = ImStrSkipBlank(line + strlen("DockSpace")); node.Flags |= ImGuiDockNodeFlags_DockSpace; }
+    else return;
+    if (sscanf(line, "ID=0x%08X%n",      &node.ID, &r) == 1)            { line += r; } else return;
+    if (sscanf(line, " Parent=0x%08X%n", &node.ParentNodeId, &r) == 1)  { line += r; if (node.ParentNodeId == 0) return; }
+    if (sscanf(line, " Window=0x%08X%n", &node.ParentWindowId, &r) ==1) { line += r; if (node.ParentWindowId == 0) return; }
+    if (node.ParentNodeId == 0)
+    {
+        if (sscanf(line, " Pos=%i,%i%n",  &x, &y, &r) == 2)         { line += r; node.Pos = ImVec2ih((short)x, (short)y); } else return;
+        if (sscanf(line, " Size=%i,%i%n", &x, &y, &r) == 2)         { line += r; node.Size = ImVec2ih((short)x, (short)y); } else return;
+    }
+    else
+    {
+        if (sscanf(line, " SizeRef=%i,%i%n", &x, &y, &r) == 2)      { line += r; node.SizeRef = ImVec2ih((short)x, (short)y); }
+    }
+    if (sscanf(line, " Split=%c%n", &c, &r) == 1)                   { line += r; if (c == 'X') node.SplitAxis = ImGuiAxis_X; else if (c == 'Y') node.SplitAxis = ImGuiAxis_Y; }
+    if (sscanf(line, " NoResize=%d%n", &x, &r) == 1)                { line += r; if (x != 0) node.Flags |= ImGuiDockNodeFlags_NoResize; }
+    if (sscanf(line, " CentralNode=%d%n", &x, &r) == 1)             { line += r; if (x != 0) node.Flags |= ImGuiDockNodeFlags_CentralNode; }
+    if (sscanf(line, " NoTabBar=%d%n", &x, &r) == 1)                { line += r; if (x != 0) node.Flags |= ImGuiDockNodeFlags_NoTabBar; }
+    if (sscanf(line, " HiddenTabBar=%d%n", &x, &r) == 1)            { line += r; if (x != 0) node.Flags |= ImGuiDockNodeFlags_HiddenTabBar; }
+    if (sscanf(line, " NoWindowMenuButton=%d%n", &x, &r) == 1)      { line += r; if (x != 0) node.Flags |= ImGuiDockNodeFlags_NoWindowMenuButton; }
+    if (sscanf(line, " NoCloseButton=%d%n", &x, &r) == 1)           { line += r; if (x != 0) node.Flags |= ImGuiDockNodeFlags_NoCloseButton; }
+    if (sscanf(line, " Selected=0x%08X%n", &node.SelectedTabId,&r) == 1) { line += r; }
+    if (node.ParentNodeId != 0)
+        if (ImGuiDockNodeSettings* parent_settings = DockSettingsFindNodeSettings(ctx, node.ParentNodeId))
+            node.Depth = parent_settings->Depth + 1;
+    ctx->DockContext.NodesSettings.push_back(node);
+}
+
+static void DockSettingsHandler_DockNodeToSettings(ImGuiDockContext* dc, ImGuiDockNode* node, int depth)
+{
+    ImGuiDockNodeSettings node_settings;
+    IM_ASSERT(depth < (1 << (sizeof(node_settings.Depth) << 3)));
+    node_settings.ID = node->ID;
+    node_settings.ParentNodeId = node->ParentNode ? node->ParentNode->ID : 0;
+    node_settings.ParentWindowId = (node->IsDockSpace() && node->HostWindow && node->HostWindow->ParentWindow) ? node->HostWindow->ParentWindow->ID : 0;
+    node_settings.SelectedTabId = node->SelectedTabId;
+    node_settings.SplitAxis = (signed char)(node->IsSplitNode() ? node->SplitAxis : ImGuiAxis_None);
+    node_settings.Depth = (char)depth;
+    node_settings.Flags = (node->LocalFlags & ImGuiDockNodeFlags_SavedFlagsMask_);
+    node_settings.Pos = ImVec2ih(node->Pos);
+    node_settings.Size = ImVec2ih(node->Size);
+    node_settings.SizeRef = ImVec2ih(node->SizeRef);
+    dc->NodesSettings.push_back(node_settings);
+    if (node->ChildNodes[0])
+        DockSettingsHandler_DockNodeToSettings(dc, node->ChildNodes[0], depth + 1);
+    if (node->ChildNodes[1])
+        DockSettingsHandler_DockNodeToSettings(dc, node->ChildNodes[1], depth + 1);
+}
+
+static void ImGui::DockSettingsHandler_WriteAll(ImGuiContext* ctx, ImGuiSettingsHandler* handler, ImGuiTextBuffer* buf)
+{
+    ImGuiContext& g = *ctx;
+    ImGuiDockContext* dc = &ctx->DockContext;
+    if (!(g.IO.ConfigFlags & ImGuiConfigFlags_DockingEnable))
+        return;
+
+    // Gather settings data
+    // (unlike our windows settings, because nodes are always built we can do a full rewrite of the SettingsNode buffer)
+    dc->NodesSettings.resize(0);
+    dc->NodesSettings.reserve(dc->Nodes.Data.Size);
+    for (int n = 0; n < dc->Nodes.Data.Size; n++)
+        if (ImGuiDockNode* node = (ImGuiDockNode*)dc->Nodes.Data[n].val_p)
+            if (node->IsRootNode())
+                DockSettingsHandler_DockNodeToSettings(dc, node, 0);
+
+    int max_depth = 0;
+    for (int node_n = 0; node_n < dc->NodesSettings.Size; node_n++)
+        max_depth = ImMax((int)dc->NodesSettings[node_n].Depth, max_depth);
+
+    // Write to text buffer
+    buf->appendf("[%s][Data]\n", handler->TypeName);
+    for (int node_n = 0; node_n < dc->NodesSettings.Size; node_n++)
+    {
+        const int line_start_pos = buf->size(); (void)line_start_pos;
+        const ImGuiDockNodeSettings* node_settings = &dc->NodesSettings[node_n];
+        buf->appendf("%*s%s%*s", node_settings->Depth * 2, "", (node_settings->Flags & ImGuiDockNodeFlags_DockSpace) ? "DockSpace" : "DockNode ", (max_depth - node_settings->Depth) * 2, "");  // Text align nodes to facilitate looking at .ini file
+        buf->appendf(" ID=0x%08X", node_settings->ID);
+        if (node_settings->ParentNodeId)
+        {
+            buf->appendf(" Parent=0x%08X SizeRef=%d,%d", node_settings->ParentNodeId, node_settings->SizeRef.x, node_settings->SizeRef.y);
+        }
+        else
+        {
+            if (node_settings->ParentWindowId)
+                buf->appendf(" Window=0x%08X", node_settings->ParentWindowId);
+            buf->appendf(" Pos=%d,%d Size=%d,%d", node_settings->Pos.x, node_settings->Pos.y, node_settings->Size.x, node_settings->Size.y);
+        }
+        if (node_settings->SplitAxis != ImGuiAxis_None)
+            buf->appendf(" Split=%c", (node_settings->SplitAxis == ImGuiAxis_X) ? 'X' : 'Y');
+        if (node_settings->Flags & ImGuiDockNodeFlags_NoResize)
+            buf->appendf(" NoResize=1");
+        if (node_settings->Flags & ImGuiDockNodeFlags_CentralNode)
+            buf->appendf(" CentralNode=1");
+        if (node_settings->Flags & ImGuiDockNodeFlags_NoTabBar)
+            buf->appendf(" NoTabBar=1");
+        if (node_settings->Flags & ImGuiDockNodeFlags_HiddenTabBar)
+            buf->appendf(" HiddenTabBar=1");
+        if (node_settings->Flags & ImGuiDockNodeFlags_NoWindowMenuButton)
+            buf->appendf(" NoWindowMenuButton=1");
+        if (node_settings->Flags & ImGuiDockNodeFlags_NoCloseButton)
+            buf->appendf(" NoCloseButton=1");
+        if (node_settings->SelectedTabId)
+            buf->appendf(" Selected=0x%08X", node_settings->SelectedTabId);
+
+        // [DEBUG] Include comments in the .ini file to ease debugging (this makes saving slower!)
+        if (g.IO.ConfigDebugIniSettings)
+            if (ImGuiDockNode* node = DockContextFindNodeByID(ctx, node_settings->ID))
+            {
+                buf->appendf("%*s", ImMax(2, (line_start_pos + 92) - buf->size()), "");     // Align everything
+                if (node->IsDockSpace() && node->HostWindow && node->HostWindow->ParentWindow)
+                    buf->appendf(" ; in '%s'", node->HostWindow->ParentWindow->Name);
+                // Iterate settings so we can give info about windows that didn't exist during the session.
+                int contains_window = 0;
+                for (ImGuiWindowSettings* settings = g.SettingsWindows.begin(); settings != NULL; settings = g.SettingsWindows.next_chunk(settings))
+                    if (settings->DockId == node_settings->ID)
+                    {
+                        if (contains_window++ == 0)
+                            buf->appendf(" ; contains ");
+                        buf->appendf("'%s' ", settings->GetName());
+                    }
+            }
+
+        buf->appendf("\n");
+    }
+    buf->appendf("\n");
+}
 
 
 //-----------------------------------------------------------------------------
@@ -14212,14 +19832,14 @@
     if (HIMC himc = ::ImmGetContext(hwnd))
     {
         COMPOSITIONFORM composition_form = {};
-        composition_form.ptCurrentPos.x = (LONG)data->InputPos.x;
-        composition_form.ptCurrentPos.y = (LONG)data->InputPos.y;
+        composition_form.ptCurrentPos.x = (LONG)(data->InputPos.x - viewport->Pos.x);
+        composition_form.ptCurrentPos.y = (LONG)(data->InputPos.y - viewport->Pos.y);
         composition_form.dwStyle = CFS_FORCE_POSITION;
         ::ImmSetCompositionWindow(himc, &composition_form);
         CANDIDATEFORM candidate_form = {};
         candidate_form.dwStyle = CFS_CANDIDATEPOS;
-        candidate_form.ptCurrentPos.x = (LONG)data->InputPos.x;
-        candidate_form.ptCurrentPos.y = (LONG)data->InputPos.y;
+        candidate_form.ptCurrentPos.x = (LONG)(data->InputPos.x - viewport->Pos.x);
+        candidate_form.ptCurrentPos.y = (LONG)(data->InputPos.y - viewport->Pos.y);
         ::ImmSetCandidateWindow(himc, &candidate_form);
         ::ImmReleaseContext(hwnd, himc);
     }
@@ -14241,6 +19861,7 @@
 // - ShowFontAtlas() [Internal]
 // - ShowMetricsWindow()
 // - DebugNodeColumns() [Internal]
+// - DebugNodeDockNode() [Internal]
 // - DebugNodeDrawList() [Internal]
 // - DebugNodeDrawCmdShowMeshAndBoundingBox() [Internal]
 // - DebugNodeFont() [Internal]
@@ -14263,12 +19884,14 @@
 
     ImVec2 scale = bb.GetSize() / viewport->Size;
     ImVec2 off = bb.Min - viewport->Pos * scale;
-    float alpha_mul = 1.0f;
+    float alpha_mul = (viewport->Flags & ImGuiViewportFlags_IsMinimized) ? 0.30f : 1.00f;
     window->DrawList->AddRectFilled(bb.Min, bb.Max, GetColorU32(ImGuiCol_Border, alpha_mul * 0.40f));
     for (ImGuiWindow* thumb_window : g.Windows)
     {
         if (!thumb_window->WasActive || (thumb_window->Flags & ImGuiWindowFlags_ChildWindow))
             continue;
+        if (thumb_window->Viewport != viewport)
+            continue;
 
         ImRect thumb_r = thumb_window->Rect();
         ImRect title_r = thumb_window->TitleBarRect();
@@ -14292,10 +19915,19 @@
     ImGuiContext& g = *GImGui;
     ImGuiWindow* window = g.CurrentWindow;
 
+    // Draw monitor and calculate their boundaries
     float SCALE = 1.0f / 8.0f;
-    ImRect bb_full(g.Viewports[0]->Pos, g.Viewports[0]->Pos + g.Viewports[0]->Size);
+    ImRect bb_full(FLT_MAX, FLT_MAX, -FLT_MAX, -FLT_MAX);
+    for (ImGuiPlatformMonitor& monitor : g.PlatformIO.Monitors)
+        bb_full.Add(ImRect(monitor.MainPos, monitor.MainPos + monitor.MainSize));
     ImVec2 p = window->DC.CursorPos;
     ImVec2 off = p - bb_full.Min * SCALE;
+    for (ImGuiPlatformMonitor& monitor : g.PlatformIO.Monitors)
+    {
+        ImRect monitor_draw_bb(off + (monitor.MainPos) * SCALE, off + (monitor.MainPos + monitor.MainSize) * SCALE);
+        window->DrawList->AddRect(monitor_draw_bb.Min, monitor_draw_bb.Max, (g.DebugMetricsConfig.HighlightMonitorIdx == g.PlatformIO.Monitors.index_from_ptr(&monitor)) ? IM_COL32(255, 255, 0, 255) : ImGui::GetColorU32(ImGuiCol_Border), 4.0f);
+        window->DrawList->AddRectFilled(monitor_draw_bb.Min, monitor_draw_bb.Max, ImGui::GetColorU32(ImGuiCol_Border, 0.10f), 4.0f);
+    }
 
     // Draw viewports
     for (ImGuiViewportP* viewport : g.Viewports)
@@ -14306,6 +19938,13 @@
     ImGui::Dummy(bb_full.GetSize() * SCALE);
 }
 
+static int IMGUI_CDECL ViewportComparerByLastFocusedStampCount(const void* lhs, const void* rhs)
+{
+    const ImGuiViewportP* a = *(const ImGuiViewportP* const*)lhs;
+    const ImGuiViewportP* b = *(const ImGuiViewportP* const*)rhs;
+    return b->LastFocusedStampCount - a->LastFocusedStampCount;
+}
+
 // Draw an arbitrary US keyboard layout to visualize translated keys
 void ImGui::DebugRenderKeyboardPreview(ImDrawList* draw_list)
 {
@@ -14668,14 +20307,41 @@
         Checkbox("Show ImDrawCmd mesh when hovering", &cfg->ShowDrawCmdMesh);
         Checkbox("Show ImDrawCmd bounding boxes when hovering", &cfg->ShowDrawCmdBoundingBoxes);
         for (ImGuiViewportP* viewport : g.Viewports)
+        {
+            bool viewport_has_drawlist = false;
             for (ImDrawList* draw_list : viewport->DrawDataP.CmdLists)
+            {
+                if (!viewport_has_drawlist)
+                    Text("Active DrawLists in Viewport #%d, ID: 0x%08X", viewport->Idx, viewport->ID);
+                viewport_has_drawlist = true;
                 DebugNodeDrawList(NULL, viewport, draw_list, "DrawList");
+            }
+        }
         TreePop();
     }
 
     // Viewports
     if (TreeNode("Viewports", "Viewports (%d)", g.Viewports.Size))
     {
+        cfg->HighlightMonitorIdx = -1;
+        bool open = TreeNode("Monitors", "Monitors (%d)", g.PlatformIO.Monitors.Size);
+        SameLine();
+        MetricsHelpMarker("Dear ImGui uses monitor data:\n- to query DPI settings on a per monitor basis\n- to position popup/tooltips so they don't straddle monitors.");
+        if (open)
+        {
+            for (int i = 0; i < g.PlatformIO.Monitors.Size; i++)
+            {
+                const ImGuiPlatformMonitor& mon = g.PlatformIO.Monitors[i];
+                BulletText("Monitor #%d: DPI %.0f%%\n MainMin (%.0f,%.0f), MainMax (%.0f,%.0f), MainSize (%.0f,%.0f)\n WorkMin (%.0f,%.0f), WorkMax (%.0f,%.0f), WorkSize (%.0f,%.0f)",
+                    i, mon.DpiScale * 100.0f,
+                    mon.MainPos.x, mon.MainPos.y, mon.MainPos.x + mon.MainSize.x, mon.MainPos.y + mon.MainSize.y, mon.MainSize.x, mon.MainSize.y,
+                    mon.WorkPos.x, mon.WorkPos.y, mon.WorkPos.x + mon.WorkSize.x, mon.WorkPos.y + mon.WorkSize.y, mon.WorkSize.x, mon.WorkSize.y);
+                if (IsItemHovered())
+                    cfg->HighlightMonitorIdx = i;
+            }
+            TreePop();
+        }
+
         SetNextItemOpen(true, ImGuiCond_Once);
         if (TreeNode("Windows Minimap"))
         {
@@ -14684,6 +20350,26 @@
         }
         cfg->HighlightViewportID = 0;
 
+        BulletText("MouseViewport: 0x%08X (UserHovered 0x%08X, LastHovered 0x%08X)", g.MouseViewport ? g.MouseViewport->ID : 0, g.IO.MouseHoveredViewport, g.MouseLastHoveredViewport ? g.MouseLastHoveredViewport->ID : 0);
+        if (TreeNode("Inferred Z order (front-to-back)"))
+        {
+            static ImVector<ImGuiViewportP*> viewports;
+            viewports.resize(g.Viewports.Size);
+            memcpy(viewports.Data, g.Viewports.Data, g.Viewports.size_in_bytes());
+            if (viewports.Size > 1)
+                ImQsort(viewports.Data, viewports.Size, sizeof(ImGuiViewport*), ViewportComparerByLastFocusedStampCount);
+            for (ImGuiViewportP* viewport : viewports)
+            {
+                BulletText("Viewport #%d, ID: 0x%08X, LastFocused = %08d, PlatformFocused = %s, Window: \"%s\"",
+                    viewport->Idx, viewport->ID, viewport->LastFocusedStampCount,
+                    (g.PlatformIO.Platform_GetWindowFocus && viewport->PlatformWindowCreated) ? (g.PlatformIO.Platform_GetWindowFocus(viewport) ? "1" : "0") : "N/A",
+                    viewport->Window ? viewport->Window->Name : "N/A");
+                if (IsItemHovered())
+                    cfg->HighlightViewportID = viewport->ID;
+            }
+            TreePop();
+        }
+
         for (ImGuiViewportP* viewport : g.Viewports)
             DebugNodeViewport(viewport);
         TreePop();
@@ -14751,6 +20437,17 @@
 #ifdef IMGUI_HAS_DOCK
     if (TreeNode("Docking"))
     {
+        static bool root_nodes_only = true;
+        ImGuiDockContext* dc = &g.DockContext;
+        Checkbox("List root nodes", &root_nodes_only);
+        Checkbox("Ctrl shows window dock info", &cfg->ShowDockingNodes);
+        if (SmallButton("Clear nodes")) { DockContextClearNodes(&g, 0, true); }
+        SameLine();
+        if (SmallButton("Rebuild all")) { dc->WantFullRebuild = true; }
+        for (int n = 0; n < dc->Nodes.Data.Size; n++)
+            if (ImGuiDockNode* node = (ImGuiDockNode*)dc->Nodes.Data[n].val_p)
+                if (!root_nodes_only || node->IsRootNode())
+                    DebugNodeDockNode(node, "Node");
         TreePop();
     }
 #endif // #ifdef IMGUI_HAS_DOCK
@@ -14794,6 +20491,29 @@
         }
 
 #ifdef IMGUI_HAS_DOCK
+        if (TreeNode("SettingsDocking", "Settings packed data: Docking"))
+        {
+            ImGuiDockContext* dc = &g.DockContext;
+            Text("In SettingsWindows:");
+            for (ImGuiWindowSettings* settings = g.SettingsWindows.begin(); settings != NULL; settings = g.SettingsWindows.next_chunk(settings))
+                if (settings->DockId != 0)
+                    BulletText("Window '%s' -> DockId %08X DockOrder=%d", settings->GetName(), settings->DockId, settings->DockOrder);
+            Text("In SettingsNodes:");
+            for (int n = 0; n < dc->NodesSettings.Size; n++)
+            {
+                ImGuiDockNodeSettings* settings = &dc->NodesSettings[n];
+                const char* selected_tab_name = NULL;
+                if (settings->SelectedTabId)
+                {
+                    if (ImGuiWindow* window = FindWindowByID(settings->SelectedTabId))
+                        selected_tab_name = window->Name;
+                    else if (ImGuiWindowSettings* window_settings = FindWindowSettingsByID(settings->SelectedTabId))
+                        selected_tab_name = window_settings->GetName();
+                }
+                BulletText("Node %08X, Parent %08X, SelectedTab %08X ('%s')", settings->ID, settings->ParentNodeId, settings->SelectedTabId, selected_tab_name ? selected_tab_name : settings->SelectedTabId ? "N/A" : "");
+            }
+            TreePop();
+        }
 #endif // #ifdef IMGUI_HAS_DOCK
 
         if (TreeNode("SettingsIniData", "Settings unpacked data (.ini): %d bytes", g.SettingsIniData.size()))
@@ -14922,9 +20642,11 @@
         Text("WINDOWING");
         Indent();
         Text("HoveredWindow: '%s'", g.HoveredWindow ? g.HoveredWindow->Name : "NULL");
-        Text("HoveredWindow->Root: '%s'", g.HoveredWindow ? g.HoveredWindow->RootWindow->Name : "NULL");
+        Text("HoveredWindow->Root: '%s'", g.HoveredWindow ? g.HoveredWindow->RootWindowDockTree->Name : "NULL");
         Text("HoveredWindowUnderMovingWindow: '%s'", g.HoveredWindowUnderMovingWindow ? g.HoveredWindowUnderMovingWindow->Name : "NULL");
+        Text("HoveredDockNode: 0x%08X", g.DebugHoveredDockNode ? g.DebugHoveredDockNode->ID : 0);
         Text("MovingWindow: '%s'", g.MovingWindow ? g.MovingWindow->Name : "NULL");
+        Text("MouseViewport: 0x%08X (UserHovered 0x%08X, LastHovered 0x%08X)", g.MouseViewport->ID, g.IO.MouseHoveredViewport, g.MouseLastHoveredViewport ? g.MouseLastHoveredViewport->ID : 0);
         Unindent();
 
         Text("ITEMS");
@@ -15018,8 +20740,21 @@
 
 #ifdef IMGUI_HAS_DOCK
     // Overlay: Display Docking info
-    if (show_docking_nodes && g.IO.KeyCtrl)
+    if (cfg->ShowDockingNodes && g.IO.KeyCtrl && g.DebugHoveredDockNode)
     {
+        char buf[64] = "";
+        char* p = buf;
+        ImGuiDockNode* node = g.DebugHoveredDockNode;
+        ImDrawList* overlay_draw_list = node->HostWindow ? GetForegroundDrawList(node->HostWindow) : GetForegroundDrawList(GetMainViewport());
+        p += ImFormatString(p, buf + IM_ARRAYSIZE(buf) - p, "DockId: %X%s\n", node->ID, node->IsCentralNode() ? " *CentralNode*" : "");
+        p += ImFormatString(p, buf + IM_ARRAYSIZE(buf) - p, "WindowClass: %08X\n", node->WindowClass.ClassId);
+        p += ImFormatString(p, buf + IM_ARRAYSIZE(buf) - p, "Size: (%.0f, %.0f)\n", node->Size.x, node->Size.y);
+        p += ImFormatString(p, buf + IM_ARRAYSIZE(buf) - p, "SizeRef: (%.0f, %.0f)\n", node->SizeRef.x, node->SizeRef.y);
+        int depth = DockNodeGetDepth(node);
+        overlay_draw_list->AddRect(node->Pos + ImVec2(3, 3) * (float)depth, node->Pos + node->Size - ImVec2(3, 3) * (float)depth, IM_COL32(200, 100, 100, 255));
+        ImVec2 pos = node->Pos + ImVec2(3, 3) * (float)depth;
+        overlay_draw_list->AddRectFilled(pos - ImVec2(1, 1), pos + CalcTextSize(buf) + ImVec2(1, 1), IM_COL32(200, 100, 100, 255));
+        overlay_draw_list->AddText(NULL, 0.0f, pos, IM_COL32(255, 255, 255, 255), buf);
     }
 #endif // #ifdef IMGUI_HAS_DOCK
 
@@ -15095,6 +20830,93 @@
     TreePop();
 }
 
+static void DebugNodeDockNodeFlags(ImGuiDockNodeFlags* p_flags, const char* label, bool enabled)
+{
+    using namespace ImGui;
+    PushID(label);
+    PushStyleVar(ImGuiStyleVar_FramePadding, ImVec2(0.0f, 0.0f));
+    Text("%s:", label);
+    if (!enabled)
+        BeginDisabled();
+    CheckboxFlags("NoResize", p_flags, ImGuiDockNodeFlags_NoResize);
+    CheckboxFlags("NoResizeX", p_flags, ImGuiDockNodeFlags_NoResizeX);
+    CheckboxFlags("NoResizeY",p_flags, ImGuiDockNodeFlags_NoResizeY);
+    CheckboxFlags("NoTabBar", p_flags, ImGuiDockNodeFlags_NoTabBar);
+    CheckboxFlags("HiddenTabBar", p_flags, ImGuiDockNodeFlags_HiddenTabBar);
+    CheckboxFlags("NoWindowMenuButton", p_flags, ImGuiDockNodeFlags_NoWindowMenuButton);
+    CheckboxFlags("NoCloseButton", p_flags, ImGuiDockNodeFlags_NoCloseButton);
+    CheckboxFlags("DockedWindowsInFocusRoute", p_flags, ImGuiDockNodeFlags_DockedWindowsInFocusRoute);
+    CheckboxFlags("NoDocking", p_flags, ImGuiDockNodeFlags_NoDocking); // Multiple flags
+    CheckboxFlags("NoDockingSplit", p_flags, ImGuiDockNodeFlags_NoDockingSplit);
+    CheckboxFlags("NoDockingSplitOther", p_flags, ImGuiDockNodeFlags_NoDockingSplitOther);
+    CheckboxFlags("NoDockingOver", p_flags, ImGuiDockNodeFlags_NoDockingOverMe);
+    CheckboxFlags("NoDockingOverOther", p_flags, ImGuiDockNodeFlags_NoDockingOverOther);
+    CheckboxFlags("NoDockingOverEmpty", p_flags, ImGuiDockNodeFlags_NoDockingOverEmpty);
+    CheckboxFlags("NoUndocking", p_flags, ImGuiDockNodeFlags_NoUndocking);
+    if (!enabled)
+        EndDisabled();
+    PopStyleVar();
+    PopID();
+}
+
+// [DEBUG] Display contents of ImDockNode
+void ImGui::DebugNodeDockNode(ImGuiDockNode* node, const char* label)
+{
+    ImGuiContext& g = *GImGui;
+    const bool is_alive = (g.FrameCount - node->LastFrameAlive < 2);    // Submitted with ImGuiDockNodeFlags_KeepAliveOnly
+    const bool is_active = (g.FrameCount - node->LastFrameActive < 2);  // Submitted
+    if (!is_alive) { PushStyleColor(ImGuiCol_Text, GetStyleColorVec4(ImGuiCol_TextDisabled)); }
+    bool open;
+    ImGuiTreeNodeFlags tree_node_flags = node->IsFocused ? ImGuiTreeNodeFlags_Selected : ImGuiTreeNodeFlags_None;
+    if (node->Windows.Size > 0)
+        open = TreeNodeEx((void*)(intptr_t)node->ID, tree_node_flags, "%s 0x%04X%s: %d windows (vis: '%s')", label, node->ID, node->IsVisible ? "" : " (hidden)", node->Windows.Size, node->VisibleWindow ? node->VisibleWindow->Name : "NULL");
+    else
+        open = TreeNodeEx((void*)(intptr_t)node->ID, tree_node_flags, "%s 0x%04X%s: %s (vis: '%s')", label, node->ID, node->IsVisible ? "" : " (hidden)", (node->SplitAxis == ImGuiAxis_X) ? "horizontal split" : (node->SplitAxis == ImGuiAxis_Y) ? "vertical split" : "empty", node->VisibleWindow ? node->VisibleWindow->Name : "NULL");
+    if (!is_alive) { PopStyleColor(); }
+    if (is_active && IsItemHovered())
+        if (ImGuiWindow* window = node->HostWindow ? node->HostWindow : node->VisibleWindow)
+            GetForegroundDrawList(window)->AddRect(node->Pos, node->Pos + node->Size, IM_COL32(255, 255, 0, 255));
+    if (open)
+    {
+        IM_ASSERT(node->ChildNodes[0] == NULL || node->ChildNodes[0]->ParentNode == node);
+        IM_ASSERT(node->ChildNodes[1] == NULL || node->ChildNodes[1]->ParentNode == node);
+        BulletText("Pos (%.0f,%.0f), Size (%.0f, %.0f) Ref (%.0f, %.0f)",
+            node->Pos.x, node->Pos.y, node->Size.x, node->Size.y, node->SizeRef.x, node->SizeRef.y);
+        DebugNodeWindow(node->HostWindow, "HostWindow");
+        DebugNodeWindow(node->VisibleWindow, "VisibleWindow");
+        BulletText("SelectedTabID: 0x%08X, LastFocusedNodeID: 0x%08X", node->SelectedTabId, node->LastFocusedNodeId);
+        BulletText("Misc:%s%s%s%s%s%s%s",
+            node->IsDockSpace() ? " IsDockSpace" : "",
+            node->IsCentralNode() ? " IsCentralNode" : "",
+            is_alive ? " IsAlive" : "", is_active ? " IsActive" : "", node->IsFocused ? " IsFocused" : "",
+            node->WantLockSizeOnce ? " WantLockSizeOnce" : "",
+            node->HasCentralNodeChild ? " HasCentralNodeChild" : "");
+        if (TreeNode("flags", "Flags Merged: 0x%04X, Local: 0x%04X, InWindows: 0x%04X, Shared: 0x%04X", node->MergedFlags, node->LocalFlags, node->LocalFlagsInWindows, node->SharedFlags))
+        {
+            if (BeginTable("flags", 4))
+            {
+                TableNextColumn(); DebugNodeDockNodeFlags(&node->MergedFlags, "MergedFlags", false);
+                TableNextColumn(); DebugNodeDockNodeFlags(&node->LocalFlags, "LocalFlags", true);
+                TableNextColumn(); DebugNodeDockNodeFlags(&node->LocalFlagsInWindows, "LocalFlagsInWindows", false);
+                TableNextColumn(); DebugNodeDockNodeFlags(&node->SharedFlags, "SharedFlags", true);
+                EndTable();
+            }
+            TreePop();
+        }
+        if (node->ParentNode)
+            DebugNodeDockNode(node->ParentNode, "ParentNode");
+        if (node->ChildNodes[0])
+            DebugNodeDockNode(node->ChildNodes[0], "Child[0]");
+        if (node->ChildNodes[1])
+            DebugNodeDockNode(node->ChildNodes[1], "Child[1]");
+        if (node->TabBar)
+            DebugNodeTabBar(node->TabBar, "TabBar");
+        DebugNodeWindowsList(&node->Windows, "Windows");
+
+        TreePop();
+    }
+}
+
 static void FormatTextureIDForDebugDisplay(char* buf, int buf_size, ImTextureID tex_id)
 {
     union { void* ptr; int integer; } tex_id_opaque;
@@ -15106,10 +20928,10 @@
 }
 
 // [DEBUG] Display contents of ImDrawList
+// Note that both 'window' and 'viewport' may be NULL here. Viewport is generally null of destroyed popups which previously owned a viewport.
 void ImGui::DebugNodeDrawList(ImGuiWindow* window, ImGuiViewportP* viewport, const ImDrawList* draw_list, const char* label)
 {
     ImGuiContext& g = *GImGui;
-    IM_UNUSED(viewport); // Used in docking branch
     ImGuiMetricsConfig* cfg = &g.DebugMetricsConfig;
     int cmd_count = draw_list->CmdBuffer.Size;
     if (cmd_count > 0 && draw_list->CmdBuffer.back().ElemCount == 0 && draw_list->CmdBuffer.back().UserCallback == NULL)
@@ -15124,7 +20946,7 @@
         return;
     }
 
-    ImDrawList* fg_draw_list = GetForegroundDrawList(window); // Render additional visuals into the top-most draw list
+    ImDrawList* fg_draw_list = viewport ? GetForegroundDrawList(viewport) : NULL; // Render additional visuals into the top-most draw list
     if (window && IsItemHovered() && fg_draw_list)
         fg_draw_list->AddRect(window->Pos, window->Pos + window->Size, IM_COL32(255, 255, 0, 255));
     if (!node_open)
@@ -15387,19 +21209,32 @@
 {
     ImGuiContext& g = *GImGui;
     SetNextItemOpen(true, ImGuiCond_Once);
-    bool open = TreeNode("viewport0", "Viewport #%d", 0);
+    bool open = TreeNode((void*)(intptr_t)viewport->ID, "Viewport #%d, ID: 0x%08X, Parent: 0x%08X, Window: \"%s\"", viewport->Idx, viewport->ID, viewport->ParentViewportId, viewport->Window ? viewport->Window->Name : "N/A");
     if (IsItemHovered())
         g.DebugMetricsConfig.HighlightViewportID = viewport->ID;
     if (open)
     {
         ImGuiWindowFlags flags = viewport->Flags;
-        BulletText("Main Pos: (%.0f,%.0f), Size: (%.0f,%.0f)\nWorkArea Offset Left: %.0f Top: %.0f, Right: %.0f, Bottom: %.0f",
+        BulletText("Main Pos: (%.0f,%.0f), Size: (%.0f,%.0f)\nWorkArea Offset Left: %.0f Top: %.0f, Right: %.0f, Bottom: %.0f\nMonitor: %d, DpiScale: %.0f%%",
             viewport->Pos.x, viewport->Pos.y, viewport->Size.x, viewport->Size.y,
-            viewport->WorkOffsetMin.x, viewport->WorkOffsetMin.y, viewport->WorkOffsetMax.x, viewport->WorkOffsetMax.y);
-        BulletText("Flags: 0x%04X =%s%s%s", viewport->Flags,
-            (flags & ImGuiViewportFlags_IsPlatformWindow)  ? " IsPlatformWindow"  : "",
+            viewport->WorkOffsetMin.x, viewport->WorkOffsetMin.y, viewport->WorkOffsetMax.x, viewport->WorkOffsetMax.y,
+            viewport->PlatformMonitor, viewport->DpiScale * 100.0f);
+        if (viewport->Idx > 0) { SameLine(); if (SmallButton("Reset Pos")) { viewport->Pos = ImVec2(200, 200); viewport->UpdateWorkRect(); if (viewport->Window) viewport->Window->Pos = viewport->Pos; } }
+        BulletText("Flags: 0x%04X =%s%s%s%s%s%s%s%s%s%s%s%s%s", viewport->Flags,
+            //(flags & ImGuiViewportFlags_IsPlatformWindow) ? " IsPlatformWindow" : "", // Omitting because it is the standard
             (flags & ImGuiViewportFlags_IsPlatformMonitor) ? " IsPlatformMonitor" : "",
-            (flags & ImGuiViewportFlags_OwnedByApp)        ? " OwnedByApp"        : "");
+            (flags & ImGuiViewportFlags_IsMinimized) ? " IsMinimized" : "",
+            (flags & ImGuiViewportFlags_IsFocused) ? " IsFocused" : "",
+            (flags & ImGuiViewportFlags_OwnedByApp) ? " OwnedByApp" : "",
+            (flags & ImGuiViewportFlags_NoDecoration) ? " NoDecoration" : "",
+            (flags & ImGuiViewportFlags_NoTaskBarIcon) ? " NoTaskBarIcon" : "",
+            (flags & ImGuiViewportFlags_NoFocusOnAppearing) ? " NoFocusOnAppearing" : "",
+            (flags & ImGuiViewportFlags_NoFocusOnClick) ? " NoFocusOnClick" : "",
+            (flags & ImGuiViewportFlags_NoInputs) ? " NoInputs" : "",
+            (flags & ImGuiViewportFlags_NoRendererClear) ? " NoRendererClear" : "",
+            (flags & ImGuiViewportFlags_NoAutoMerge) ? " NoAutoMerge" : "",
+            (flags & ImGuiViewportFlags_TopMost) ? " TopMost" : "",
+            (flags & ImGuiViewportFlags_CanHostOtherWindows) ? " CanHostOtherWindows" : "");
         for (ImDrawList* draw_list : viewport->DrawDataP.CmdLists)
             DebugNodeDrawList(NULL, viewport, draw_list, "DrawList");
         TreePop();
@@ -15438,6 +21273,7 @@
         (flags & ImGuiWindowFlags_ChildWindow)  ? "Child " : "",      (flags & ImGuiWindowFlags_Tooltip)     ? "Tooltip "   : "",  (flags & ImGuiWindowFlags_Popup) ? "Popup " : "",
         (flags & ImGuiWindowFlags_Modal)        ? "Modal " : "",      (flags & ImGuiWindowFlags_ChildMenu)   ? "ChildMenu " : "",  (flags & ImGuiWindowFlags_NoSavedSettings) ? "NoSavedSettings " : "",
         (flags & ImGuiWindowFlags_NoMouseInputs)? "NoMouseInputs":"", (flags & ImGuiWindowFlags_NoNavInputs) ? "NoNavInputs" : "", (flags & ImGuiWindowFlags_AlwaysAutoResize) ? "AlwaysAutoResize" : "");
+    BulletText("WindowClassId: 0x%08X", window->WindowClass.ClassId);
     BulletText("Scroll: (%.2f/%.2f,%.2f/%.2f) Scrollbar:%s%s", window->Scroll.x, window->ScrollMax.x, window->Scroll.y, window->ScrollMax.y, window->ScrollbarX ? "X" : "", window->ScrollbarY ? "Y" : "");
     BulletText("Active: %d/%d, WriteAccessed: %d, BeginOrderWithinContext: %d", window->Active, window->WasActive, window->WriteAccessed, (window->Active || window->WasActive) ? window->BeginOrderWithinContext : -1);
     BulletText("Appearing: %d, Hidden: %d (CanSkip %d Cannot %d), SkipItems: %d", window->Appearing, window->Hidden, window->HiddenFramesCanSkipItems, window->HiddenFramesCannotSkipItems, window->SkipItems);
@@ -15454,7 +21290,15 @@
     for (int layer = 0; layer < ImGuiNavLayer_COUNT; layer++)
         BulletText("NavPreferredScoringPosRel[%d] = {%.1f,%.1f)", layer, (pr[layer].x == FLT_MAX ? -99999.0f : pr[layer].x), (pr[layer].y == FLT_MAX ? -99999.0f : pr[layer].y)); // Display as 99999.0f so it looks neater.
     BulletText("NavLayersActiveMask: %X, NavLastChildNavWindow: %s", window->DC.NavLayersActiveMask, window->NavLastChildNavWindow ? window->NavLastChildNavWindow->Name : "NULL");
+
+    BulletText("Viewport: %d%s, ViewportId: 0x%08X, ViewportPos: (%.1f,%.1f)", window->Viewport ? window->Viewport->Idx : -1, window->ViewportOwned ? " (Owned)" : "", window->ViewportId, window->ViewportPos.x, window->ViewportPos.y);
+    BulletText("ViewportMonitor: %d", window->Viewport ? window->Viewport->PlatformMonitor : -1);
+    BulletText("DockId: 0x%04X, DockOrder: %d, Act: %d, Vis: %d", window->DockId, window->DockOrder, window->DockIsActive, window->DockTabIsVisible);
+    if (window->DockNode || window->DockNodeAsHost)
+        DebugNodeDockNode(window->DockNodeAsHost ? window->DockNodeAsHost : window->DockNode, window->DockNodeAsHost ? "DockNodeAsHost" : "DockNode");
+
     if (window->RootWindow != window)               { DebugNodeWindow(window->RootWindow, "RootWindow"); }
+    if (window->RootWindowDockTree != window->RootWindow) { DebugNodeWindow(window->RootWindowDockTree, "RootWindowDockTree"); }
     if (window->ParentWindow != NULL)               { DebugNodeWindow(window->ParentWindow, "ParentWindow"); }
     if (window->ParentWindowForFocusRoute != NULL)  { DebugNodeWindow(window->ParentWindowForFocusRoute, "ParentWindowForFocusRoute"); }
     if (window->DC.ChildWindows.Size > 0)           { DebugNodeWindowsList(&window->DC.ChildWindows, "ChildWindows"); }
@@ -15576,11 +21420,13 @@
 
     ShowDebugLogFlag("ActiveId", ImGuiDebugLogFlags_EventActiveId);
     ShowDebugLogFlag("Clipper", ImGuiDebugLogFlags_EventClipper);
+    ShowDebugLogFlag("Docking", ImGuiDebugLogFlags_EventDocking);
     ShowDebugLogFlag("Focus", ImGuiDebugLogFlags_EventFocus);
     ShowDebugLogFlag("IO", ImGuiDebugLogFlags_EventIO);
     ShowDebugLogFlag("Nav", ImGuiDebugLogFlags_EventNav);
     ShowDebugLogFlag("Popup", ImGuiDebugLogFlags_EventPopup);
     //ShowDebugLogFlag("Selection", ImGuiDebugLogFlags_EventSelection);
+    ShowDebugLogFlag("Viewport", ImGuiDebugLogFlags_EventViewport);
     ShowDebugLogFlag("InputRouting", ImGuiDebugLogFlags_EventInputRouting);
 
     if (SmallButton("Clear"))
diff --git a/imgui.h b/imgui.h
index bc1ec84..106d000 100644
--- a/imgui.h
+++ b/imgui.h
@@ -30,6 +30,8 @@
 #define IMGUI_VERSION       "1.90.7 WIP"
 #define IMGUI_VERSION_NUM   19066
 #define IMGUI_HAS_TABLE
+#define IMGUI_HAS_VIEWPORT          // Viewport WIP branch
+#define IMGUI_HAS_DOCK              // Docking WIP branch
 
 /*
 
@@ -42,12 +44,12 @@
 // [SECTION] Helpers: Memory allocations macros, ImVector<>
 // [SECTION] ImGuiStyle
 // [SECTION] ImGuiIO
-// [SECTION] Misc data structures (ImGuiInputTextCallbackData, ImGuiSizeCallbackData, ImGuiPayload)
+// [SECTION] Misc data structures (ImGuiInputTextCallbackData, ImGuiSizeCallbackData, ImGuiWindowClass, ImGuiPayload)
 // [SECTION] Helpers (ImGuiOnceUponAFrame, ImGuiTextFilter, ImGuiTextBuffer, ImGuiStorage, ImGuiListClipper, Math Operators, ImColor)
 // [SECTION] Drawing API (ImDrawCallback, ImDrawCmd, ImDrawIdx, ImDrawVert, ImDrawChannel, ImDrawListSplitter, ImDrawFlags, ImDrawListFlags, ImDrawList, ImDrawData)
 // [SECTION] Font API (ImFontConfig, ImFontGlyph, ImFontGlyphRangesBuilder, ImFontAtlasFlags, ImFontAtlas, ImFont)
 // [SECTION] Viewports (ImGuiViewportFlags, ImGuiViewport)
-// [SECTION] Platform Dependent Interfaces (ImGuiPlatformImeData)
+// [SECTION] Platform Dependent Interfaces (ImGuiPlatformIO, ImGuiPlatformMonitor, ImGuiPlatformImeData)
 // [SECTION] Obsolete functions and types
 
 */
@@ -165,6 +167,8 @@
 struct ImGuiListClipper;            // Helper to manually clip large list of items
 struct ImGuiOnceUponAFrame;         // Helper for running a block of code not more than once a frame
 struct ImGuiPayload;                // User data payload for drag and drop operations
+struct ImGuiPlatformIO;             // Multi-viewport support: interface for Platform/Renderer backends + viewports to render
+struct ImGuiPlatformMonitor;        // Multi-viewport support: user-provided bounds for each connected monitor/display. Used when positioning popups and tooltips to avoid them straddling monitors
 struct ImGuiPlatformImeData;        // Platform IME data for io.SetPlatformImeDataFn() function.
 struct ImGuiSizeCallbackData;       // Callback data when using SetNextWindowSizeConstraints() (rare/advanced use)
 struct ImGuiStorage;                // Helper for key->value storage
@@ -173,7 +177,8 @@
 struct ImGuiTableColumnSortSpecs;   // Sorting specification for one column of a table
 struct ImGuiTextBuffer;             // Helper to hold and append into a text buffer (~string builder)
 struct ImGuiTextFilter;             // Helper to parse and apply text filters (e.g. "aaaaa[,bbbbb][,ccccc]")
-struct ImGuiViewport;               // A Platform Window (always only one in 'master' branch), in the future may represent Platform Monitor
+struct ImGuiViewport;               // A Platform Window (always 1 unless multi-viewport are enabled. One per platform window to output to). In the future may represent Platform Monitor
+struct ImGuiWindowClass;            // Window class (rare/advanced uses: provide hints to the platform backend via altered viewport flags and parent/child info)
 
 // Enumerations
 // - We don't use strongly typed enums much because they add constraints (can't extend in private code, can't store typed in bit fields, extra casting on iteration)
@@ -207,6 +212,7 @@
 typedef int ImGuiColorEditFlags;    // -> enum ImGuiColorEditFlags_  // Flags: for ColorEdit4(), ColorPicker4() etc.
 typedef int ImGuiConfigFlags;       // -> enum ImGuiConfigFlags_     // Flags: for io.ConfigFlags
 typedef int ImGuiComboFlags;        // -> enum ImGuiComboFlags_      // Flags: for BeginCombo()
+typedef int ImGuiDockNodeFlags;     // -> enum ImGuiDockNodeFlags_   // Flags: for DockSpace()
 typedef int ImGuiDragDropFlags;     // -> enum ImGuiDragDropFlags_   // Flags: for BeginDragDropSource(), AcceptDragDropPayload()
 typedef int ImGuiFocusedFlags;      // -> enum ImGuiFocusedFlags_    // Flags: for IsWindowFocused()
 typedef int ImGuiHoveredFlags;      // -> enum ImGuiHoveredFlags_    // Flags: for IsItemHovered(), IsWindowHovered() etc.
@@ -379,10 +385,12 @@
     IMGUI_API bool          IsWindowFocused(ImGuiFocusedFlags flags=0); // is current window focused? or its root/child, depending on flags. see flags for options.
     IMGUI_API bool          IsWindowHovered(ImGuiHoveredFlags flags=0); // is current window hovered and hoverable (e.g. not blocked by a popup/modal)? See ImGuiHoveredFlags_ for options. IMPORTANT: If you are trying to check whether your mouse should be dispatched to Dear ImGui or to your underlying app, you should not use this function! Use the 'io.WantCaptureMouse' boolean for that! Refer to FAQ entry "How can I tell whether to dispatch mouse/keyboard to Dear ImGui or my application?" for details.
     IMGUI_API ImDrawList*   GetWindowDrawList();                        // get draw list associated to the current window, to append your own drawing primitives
+    IMGUI_API float         GetWindowDpiScale();                        // get DPI scale currently associated to the current window's viewport.
     IMGUI_API ImVec2        GetWindowPos();                             // get current window position in screen space (note: it is unlikely you need to use this. Consider using current layout pos instead, GetCursorScreenPos())
     IMGUI_API ImVec2        GetWindowSize();                            // get current window size (note: it is unlikely you need to use this. Consider using GetCursorScreenPos() and e.g. GetContentRegionAvail() instead)
     IMGUI_API float         GetWindowWidth();                           // get current window width (shortcut for GetWindowSize().x)
     IMGUI_API float         GetWindowHeight();                          // get current window height (shortcut for GetWindowSize().y)
+    IMGUI_API ImGuiViewport*GetWindowViewport();                        // get viewport currently associated to the current window.
 
     // Window manipulation
     // - Prefer using SetNextXXX functions (before Begin) rather that SetXXX functions (after Begin).
@@ -394,6 +402,7 @@
     IMGUI_API void          SetNextWindowFocus();                                                       // set next window to be focused / top-most. call before Begin()
     IMGUI_API void          SetNextWindowScroll(const ImVec2& scroll);                                  // set next window scrolling value (use < 0.0f to not affect a given axis).
     IMGUI_API void          SetNextWindowBgAlpha(float alpha);                                          // set next window background color alpha. helper to easily override the Alpha component of ImGuiCol_WindowBg/ChildBg/PopupBg. you may also use ImGuiWindowFlags_NoBackground.
+    IMGUI_API void          SetNextWindowViewport(ImGuiID viewport_id);                                 // set next window viewport
     IMGUI_API void          SetWindowPos(const ImVec2& pos, ImGuiCond cond = 0);                        // (not recommended) set current window position - call within Begin()/End(). prefer using SetNextWindowPos(), as this may incur tearing and side-effects.
     IMGUI_API void          SetWindowSize(const ImVec2& size, ImGuiCond cond = 0);                      // (not recommended) set current window size - call within Begin()/End(). set to ImVec2(0, 0) to force an auto-fit. prefer using SetNextWindowSize(), as this may incur tearing and minor side-effects.
     IMGUI_API void          SetWindowCollapsed(bool collapsed, ImGuiCond cond = 0);                     // (not recommended) set current window collapsed state. prefer using SetNextWindowCollapsed().
@@ -833,6 +842,26 @@
     IMGUI_API bool          TabItemButton(const char* label, ImGuiTabItemFlags flags = 0);      // create a Tab behaving like a button. return true when clicked. cannot be selected in the tab bar.
     IMGUI_API void          SetTabItemClosed(const char* tab_or_docked_window_label);           // notify TabBar or Docking system of a closed tab/window ahead (useful to reduce visual flicker on reorderable tab bars). For tab-bar: call after BeginTabBar() and before Tab submissions. Otherwise call with a window name.
 
+    // Docking
+    // [BETA API] Enable with io.ConfigFlags |= ImGuiConfigFlags_DockingEnable.
+    // Note: You can use most Docking facilities without calling any API. You DO NOT need to call DockSpace() to use Docking!
+    // - Drag from window title bar or their tab to dock/undock. Hold SHIFT to disable docking.
+    // - Drag from window menu button (upper-left button) to undock an entire node (all windows).
+    // - When io.ConfigDockingWithShift == true, you instead need to hold SHIFT to enable docking.
+    // About dockspaces:
+    // - Use DockSpaceOverViewport() to create a window covering the screen or a specific viewport + a dockspace inside it.
+    //   This is often used with ImGuiDockNodeFlags_PassthruCentralNode to make it transparent.
+    // - Use DockSpace() to create an explicit dock node _within_ an existing window. See Docking demo for details.
+    // - Important: Dockspaces need to be submitted _before_ any window they can host. Submit it early in your frame!
+    // - Important: Dockspaces need to be kept alive if hidden, otherwise windows docked into it will be undocked.
+    //   e.g. if you have multiple tabs with a dockspace inside each tab: submit the non-visible dockspaces with ImGuiDockNodeFlags_KeepAliveOnly.
+    IMGUI_API ImGuiID       DockSpace(ImGuiID dockspace_id, const ImVec2& size = ImVec2(0, 0), ImGuiDockNodeFlags flags = 0, const ImGuiWindowClass* window_class = NULL);
+    IMGUI_API ImGuiID       DockSpaceOverViewport(ImGuiID dockspace_id = 0, const ImGuiViewport* viewport = NULL, ImGuiDockNodeFlags flags = 0, const ImGuiWindowClass* window_class = NULL);
+    IMGUI_API void          SetNextWindowDockID(ImGuiID dock_id, ImGuiCond cond = 0);           // set next window dock id
+    IMGUI_API void          SetNextWindowClass(const ImGuiWindowClass* window_class);           // set next window class (control docking compatibility + provide hints to platform backend via custom viewport flags and platform parent/child relationship)
+    IMGUI_API ImGuiID       GetWindowDockID();
+    IMGUI_API bool          IsWindowDocked();                                                   // is current window docked into another window?
+
     // Logging/Capture
     // - All text output from the interface can be captured into tty/file/clipboard. By default, tree nodes are automatically opened during logging.
     IMGUI_API void          LogToTTY(int auto_open_depth = -1);                                 // start logging to tty (stdout)
@@ -904,8 +933,10 @@
     IMGUI_API ImGuiViewport* GetMainViewport();                                                 // return primary/default viewport. This can never be NULL.
 
     // Background/Foreground Draw Lists
-    IMGUI_API ImDrawList*   GetBackgroundDrawList();                                            // this draw list will be the first rendered one. Useful to quickly draw shapes/text behind dear imgui contents.
-    IMGUI_API ImDrawList*   GetForegroundDrawList();                                            // this draw list will be the last rendered one. Useful to quickly draw shapes/text over dear imgui contents.
+    IMGUI_API ImDrawList*   GetBackgroundDrawList();                                            // get background draw list for the viewport associated to the current window. this draw list will be the first rendering one. Useful to quickly draw shapes/text behind dear imgui contents.
+    IMGUI_API ImDrawList*   GetForegroundDrawList();                                            // get foreground draw list for the viewport associated to the current window. this draw list will be the last rendered one. Useful to quickly draw shapes/text over dear imgui contents.
+    IMGUI_API ImDrawList*   GetBackgroundDrawList(ImGuiViewport* viewport);                     // get background draw list for the given viewport. this draw list will be the first rendering one. Useful to quickly draw shapes/text behind dear imgui contents.
+    IMGUI_API ImDrawList*   GetForegroundDrawList(ImGuiViewport* viewport);                     // get foreground draw list for the given viewport. this draw list will be the last rendered one. Useful to quickly draw shapes/text over dear imgui contents.
 
     // Miscellaneous Utilities
     IMGUI_API bool          IsRectVisible(const ImVec2& size);                                  // test if rectangle (of given size, starting from cursor position) is visible / not clipped.
@@ -1008,6 +1039,16 @@
     IMGUI_API void*         MemAlloc(size_t size);
     IMGUI_API void          MemFree(void* ptr);
 
+    // (Optional) Platform/OS interface for multi-viewport support
+    // Read comments around the ImGuiPlatformIO structure for more details.
+    // Note: You may use GetWindowViewport() to get the current viewport of the current window.
+    IMGUI_API ImGuiPlatformIO&  GetPlatformIO();                                                // platform/renderer functions, for backend to setup + viewports list.
+    IMGUI_API void              UpdatePlatformWindows();                                        // call in main loop. will call CreateWindow/ResizeWindow/etc. platform functions for each secondary viewport, and DestroyWindow for each inactive viewport.
+    IMGUI_API void              RenderPlatformWindowsDefault(void* platform_render_arg = NULL, void* renderer_render_arg = NULL); // call in main loop. will call RenderWindow/SwapBuffers platform functions for each secondary viewport which doesn't have the ImGuiViewportFlags_Minimized flag set. May be reimplemented by user for custom rendering needs.
+    IMGUI_API void              DestroyPlatformWindows();                                       // call DestroyWindow platform functions for all viewports. call from backend Shutdown() if you need to close platform windows before imgui shutdown. otherwise will be called by DestroyContext().
+    IMGUI_API ImGuiViewport*    FindViewportByID(ImGuiID id);                                   // this is a helper for backends.
+    IMGUI_API ImGuiViewport*    FindViewportByPlatformHandle(void* platform_handle);            // this is a helper for backends. the type platform_handle is decided by the backend (e.g. HWND, MyWindow*, GLFWwindow* etc.)
+
 } // namespace ImGui
 
 //-----------------------------------------------------------------------------
@@ -1038,6 +1079,7 @@
     ImGuiWindowFlags_NoNavInputs            = 1 << 16,  // No gamepad/keyboard navigation within the window
     ImGuiWindowFlags_NoNavFocus             = 1 << 17,  // No focusing toward this window with gamepad/keyboard navigation (e.g. skipped by CTRL+TAB)
     ImGuiWindowFlags_UnsavedDocument        = 1 << 18,  // Display a dot next to the title. When used in a tab/docking context, tab is selected when clicking the X + closure is not assumed (will wait for user to stop submitting the tab). Otherwise closure is assumed when pressing the X, so if you keep submitting the tab may reappear at end of tab bar.
+    ImGuiWindowFlags_NoDocking              = 1 << 19,  // Disable docking of this window
     ImGuiWindowFlags_NoNav                  = ImGuiWindowFlags_NoNavInputs | ImGuiWindowFlags_NoNavFocus,
     ImGuiWindowFlags_NoDecoration           = ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoCollapse,
     ImGuiWindowFlags_NoInputs               = ImGuiWindowFlags_NoMouseInputs | ImGuiWindowFlags_NoNavInputs | ImGuiWindowFlags_NoNavFocus,
@@ -1049,6 +1091,7 @@
     ImGuiWindowFlags_Popup                  = 1 << 26,  // Don't use! For internal use by BeginPopup()
     ImGuiWindowFlags_Modal                  = 1 << 27,  // Don't use! For internal use by BeginPopupModal()
     ImGuiWindowFlags_ChildMenu              = 1 << 28,  // Don't use! For internal use by BeginMenu()
+    ImGuiWindowFlags_DockNodeHost           = 1 << 29,  // Don't use! For internal use by Begin()/NewFrame()
 
     // Obsolete names
 #ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
@@ -1231,7 +1274,7 @@
     ImGuiFocusedFlags_RootWindow                    = 1 << 1,   // Test from root window (top most parent of the current hierarchy)
     ImGuiFocusedFlags_AnyWindow                     = 1 << 2,   // Return true if any window is focused. Important: If you are trying to tell how to dispatch your low-level inputs, do NOT use this. Use 'io.WantCaptureMouse' instead! Please read the FAQ!
     ImGuiFocusedFlags_NoPopupHierarchy              = 1 << 3,   // Do not consider popup hierarchy (do not treat popup emitter as parent of popup) (when used with _ChildWindows or _RootWindow)
-    //ImGuiFocusedFlags_DockHierarchy               = 1 << 4,   // Consider docking hierarchy (treat dockspace host as parent of docked window) (when used with _ChildWindows or _RootWindow)
+    ImGuiFocusedFlags_DockHierarchy                 = 1 << 4,   // Consider docking hierarchy (treat dockspace host as parent of docked window) (when used with _ChildWindows or _RootWindow)
     ImGuiFocusedFlags_RootAndChildWindows           = ImGuiFocusedFlags_RootWindow | ImGuiFocusedFlags_ChildWindows,
 };
 
@@ -1245,7 +1288,7 @@
     ImGuiHoveredFlags_RootWindow                    = 1 << 1,   // IsWindowHovered() only: Test from root window (top most parent of the current hierarchy)
     ImGuiHoveredFlags_AnyWindow                     = 1 << 2,   // IsWindowHovered() only: Return true if any window is hovered
     ImGuiHoveredFlags_NoPopupHierarchy              = 1 << 3,   // IsWindowHovered() only: Do not consider popup hierarchy (do not treat popup emitter as parent of popup) (when used with _ChildWindows or _RootWindow)
-    //ImGuiHoveredFlags_DockHierarchy               = 1 << 4,   // IsWindowHovered() only: Consider docking hierarchy (treat dockspace host as parent of docked window) (when used with _ChildWindows or _RootWindow)
+    ImGuiHoveredFlags_DockHierarchy                 = 1 << 4,   // IsWindowHovered() only: Consider docking hierarchy (treat dockspace host as parent of docked window) (when used with _ChildWindows or _RootWindow)
     ImGuiHoveredFlags_AllowWhenBlockedByPopup       = 1 << 5,   // Return true even if a popup window is normally blocking access to this item/window
     //ImGuiHoveredFlags_AllowWhenBlockedByModal     = 1 << 6,   // Return true even if a modal popup window is normally blocking access to this item/window. FIXME-TODO: Unavailable yet.
     ImGuiHoveredFlags_AllowWhenBlockedByActiveItem  = 1 << 7,   // Return true even if an active item is blocking access to this item/window. Useful for Drag and Drop patterns.
@@ -1275,6 +1318,27 @@
     ImGuiHoveredFlags_NoSharedDelay                 = 1 << 17,  // IsItemHovered() only: Disable shared delay system where moving from one item to the next keeps the previous timer for a short time (standard for tooltips with long delays)
 };
 
+// Flags for ImGui::DockSpace(), shared/inherited by child nodes.
+// (Some flags can be applied to individual nodes directly)
+// FIXME-DOCK: Also see ImGuiDockNodeFlagsPrivate_ which may involve using the WIP and internal DockBuilder api.
+enum ImGuiDockNodeFlags_
+{
+    ImGuiDockNodeFlags_None                         = 0,
+    ImGuiDockNodeFlags_KeepAliveOnly                = 1 << 0,   //       // Don't display the dockspace node but keep it alive. Windows docked into this dockspace node won't be undocked.
+    //ImGuiDockNodeFlags_NoCentralNode              = 1 << 1,   //       // Disable Central Node (the node which can stay empty)
+    ImGuiDockNodeFlags_NoDockingOverCentralNode     = 1 << 2,   //       // Disable docking over the Central Node, which will be always kept empty.
+    ImGuiDockNodeFlags_PassthruCentralNode          = 1 << 3,   //       // Enable passthru dockspace: 1) DockSpace() will render a ImGuiCol_WindowBg background covering everything excepted the Central Node when empty. Meaning the host window should probably use SetNextWindowBgAlpha(0.0f) prior to Begin() when using this. 2) When Central Node is empty: let inputs pass-through + won't display a DockingEmptyBg background. See demo for details.
+    ImGuiDockNodeFlags_NoDockingSplit               = 1 << 4,   //       // Disable other windows/nodes from splitting this node.
+    ImGuiDockNodeFlags_NoResize                     = 1 << 5,   // Saved // Disable resizing node using the splitter/separators. Useful with programmatically setup dockspaces.
+    ImGuiDockNodeFlags_AutoHideTabBar               = 1 << 6,   //       // Tab bar will automatically hide when there is a single window in the dock node.
+    ImGuiDockNodeFlags_NoUndocking                  = 1 << 7,   //       // Disable undocking this node.
+
+#ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
+    ImGuiDockNodeFlags_NoSplit                      = ImGuiDockNodeFlags_NoDockingSplit, // Renamed in 1.90
+    ImGuiDockNodeFlags_NoDockingInCentralNode       = ImGuiDockNodeFlags_NoDockingOverCentralNode, // Renamed in 1.90
+#endif
+};
+
 // Flags for ImGui::BeginDragDropSource(), ImGui::AcceptDragDropPayload()
 enum ImGuiDragDropFlags_
 {
@@ -1519,6 +1583,15 @@
     ImGuiConfigFlags_NoMouse                = 1 << 4,   // Instruct imgui to clear mouse position/buttons in NewFrame(). This allows ignoring the mouse information set by the backend.
     ImGuiConfigFlags_NoMouseCursorChange    = 1 << 5,   // Instruct backend to not alter mouse cursor shape and visibility. Use if the backend cursor changes are interfering with yours and you don't want to use SetMouseCursor() to change mouse cursor. You may want to honor requests from imgui by reading GetMouseCursor() yourself instead.
 
+    // [BETA] Docking
+    ImGuiConfigFlags_DockingEnable          = 1 << 6,   // Docking enable flags.
+
+    // [BETA] Viewports
+    // When using viewports it is recommended that your default value for ImGuiCol_WindowBg is opaque (Alpha=1.0) so transition to a viewport won't be noticeable.
+    ImGuiConfigFlags_ViewportsEnable        = 1 << 10,  // Viewport enable flags (require both ImGuiBackendFlags_PlatformHasViewports + ImGuiBackendFlags_RendererHasViewports set by the respective backends)
+    ImGuiConfigFlags_DpiEnableScaleViewports= 1 << 14,  // [BETA: Don't use] FIXME-DPI: Reposition and resize imgui windows when the DpiScale of a viewport changed (mostly useful for the main viewport hosting other window). Note that resizing the main window itself is up to your application.
+    ImGuiConfigFlags_DpiEnableScaleFonts    = 1 << 15,  // [BETA: Don't use] FIXME-DPI: Request bitmap-scaled fonts to match DpiScale. This is a very low-quality workaround. The correct way to handle DPI is _currently_ to replace the atlas and/or fonts in the Platform_OnChangedViewport callback, but this is all early work in progress.
+
     // User storage (to allow your backend/engine to communicate to code that may be shared between multiple projects. Those flags are NOT used by core Dear ImGui)
     ImGuiConfigFlags_IsSRGB                 = 1 << 20,  // Application is SRGB-aware.
     ImGuiConfigFlags_IsTouchScreen          = 1 << 21,  // Application is using a touch screen instead of a mouse.
@@ -1532,6 +1605,11 @@
     ImGuiBackendFlags_HasMouseCursors       = 1 << 1,   // Backend Platform supports honoring GetMouseCursor() value to change the OS cursor shape.
     ImGuiBackendFlags_HasSetMousePos        = 1 << 2,   // Backend Platform supports io.WantSetMousePos requests to reposition the OS mouse position (only used if ImGuiConfigFlags_NavEnableSetMousePos is set).
     ImGuiBackendFlags_RendererHasVtxOffset  = 1 << 3,   // Backend Renderer supports ImDrawCmd::VtxOffset. This enables output of large meshes (64K+ vertices) while still using 16-bit indices.
+
+    // [BETA] Viewports
+    ImGuiBackendFlags_PlatformHasViewports  = 1 << 10,  // Backend Platform supports multiple viewports.
+    ImGuiBackendFlags_HasMouseHoveredViewport=1 << 11,  // Backend Platform supports calling io.AddMouseViewportEvent() with the viewport under the mouse. IF POSSIBLE, ignore viewports with the ImGuiViewportFlags_NoInputs flag (Win32 backend, GLFW 3.30+ backend can do this, SDL backend cannot). If this cannot be done, Dear ImGui needs to use a flawed heuristic to find the viewport under.
+    ImGuiBackendFlags_RendererHasViewports  = 1 << 12,  // Backend Renderer supports multiple viewports.
 };
 
 // Enumeration for PushStyleColor() / PopStyleColor()
@@ -1575,6 +1653,8 @@
     ImGuiCol_TabActive,
     ImGuiCol_TabUnfocused,
     ImGuiCol_TabUnfocusedActive,
+    ImGuiCol_DockingPreview,        // Preview overlay color when about to docking something
+    ImGuiCol_DockingEmptyBg,        // Background color for empty node (e.g. CentralNode with no window docked into it)
     ImGuiCol_PlotLines,
     ImGuiCol_PlotLinesHovered,
     ImGuiCol_PlotHistogram,
@@ -1629,13 +1709,14 @@
     ImGuiStyleVar_TabRounding,              // float     TabRounding
     ImGuiStyleVar_TabBorderSize,            // float     TabBorderSize
     ImGuiStyleVar_TabBarBorderSize,         // float     TabBarBorderSize
-    ImGuiStyleVar_TableAngledHeadersAngle,  // float  TableAngledHeadersAngle
-    ImGuiStyleVar_TableAngledHeadersTextAlign,// ImVec2 TableAngledHeadersTextAlign
+    ImGuiStyleVar_TableAngledHeadersAngle,  // float     TableAngledHeadersAngle
+    ImGuiStyleVar_TableAngledHeadersTextAlign,// ImVec2  TableAngledHeadersTextAlign
     ImGuiStyleVar_ButtonTextAlign,          // ImVec2    ButtonTextAlign
     ImGuiStyleVar_SelectableTextAlign,      // ImVec2    SelectableTextAlign
-    ImGuiStyleVar_SeparatorTextBorderSize,  // float  SeparatorTextBorderSize
+    ImGuiStyleVar_SeparatorTextBorderSize,  // float     SeparatorTextBorderSize
     ImGuiStyleVar_SeparatorTextAlign,       // ImVec2    SeparatorTextAlign
     ImGuiStyleVar_SeparatorTextPadding,     // ImVec2    SeparatorTextPadding
+    ImGuiStyleVar_DockingSeparatorSize,     // float     DockingSeparatorSize
     ImGuiStyleVar_COUNT
 };
 
@@ -2073,7 +2154,8 @@
     ImVec2      SeparatorTextPadding;       // Horizontal offset of text from each edge of the separator + spacing on other axis. Generally small values. .y is recommended to be == FramePadding.y.
     ImVec2      DisplayWindowPadding;       // Window position are clamped to be visible within the display area or monitors by at least this amount. Only applies to regular windows.
     ImVec2      DisplaySafeAreaPadding;     // If you cannot see the edges of your screen (e.g. on a TV) increase the safe area padding. Apply to popups/tooltips as well regular windows. NB: Prefer configuring your TV sets correctly!
-    float       MouseCursorScale;           // Scale software rendered mouse cursor (when io.MouseDrawCursor is enabled). May be removed later.
+    float       DockingSeparatorSize;       // Thickness of resizing border between docked windows
+    float       MouseCursorScale;           // Scale software rendered mouse cursor (when io.MouseDrawCursor is enabled). We apply per-monitor DPI scaling over this scale. May be removed later.
     bool        AntiAliasedLines;           // Enable anti-aliased lines/borders. Disable if you are really tight on CPU/GPU. Latched at the beginning of the frame (copied to ImDrawList).
     bool        AntiAliasedLinesUseTex;     // Enable anti-aliased lines/borders using textures where possible. Require backend to render with bilinear filtering (NOT point/nearest filtering). Latched at the beginning of the frame (copied to ImDrawList).
     bool        AntiAliasedFill;            // Enable anti-aliased edges around filled shapes (rounded rectangles, circles, etc.). Disable if you are really tight on CPU/GPU. Latched at the beginning of the frame (copied to ImDrawList).
@@ -2134,6 +2216,18 @@
     ImFont*     FontDefault;                    // = NULL           // Font to use on NewFrame(). Use NULL to uses Fonts->Fonts[0].
     ImVec2      DisplayFramebufferScale;        // = (1, 1)         // For retina display or other situations where window coordinates are different from framebuffer coordinates. This generally ends up in ImDrawData::FramebufferScale.
 
+    // Docking options (when ImGuiConfigFlags_DockingEnable is set)
+    bool        ConfigDockingNoSplit;           // = false          // Simplified docking mode: disable window splitting, so docking is limited to merging multiple windows together into tab-bars.
+    bool        ConfigDockingWithShift;         // = false          // Enable docking with holding Shift key (reduce visual noise, allows dropping in wider space)
+    bool        ConfigDockingAlwaysTabBar;      // = false          // [BETA] [FIXME: This currently creates regression with auto-sizing and general overhead] Make every single floating window display within a docking node.
+    bool        ConfigDockingTransparentPayload;// = false          // [BETA] Make window or viewport transparent when docking and only display docking boxes on the target viewport. Useful if rendering of multiple viewport cannot be synced. Best used with ConfigViewportsNoAutoMerge.
+
+    // Viewport options (when ImGuiConfigFlags_ViewportsEnable is set)
+    bool        ConfigViewportsNoAutoMerge;     // = false;         // Set to make all floating imgui windows always create their own viewport. Otherwise, they are merged into the main host viewports when overlapping it. May also set ImGuiViewportFlags_NoAutoMerge on individual viewport.
+    bool        ConfigViewportsNoTaskBarIcon;   // = false          // Disable default OS task bar icon flag for secondary viewports. When a viewport doesn't want a task bar icon, ImGuiViewportFlags_NoTaskBarIcon will be set on it.
+    bool        ConfigViewportsNoDecoration;    // = true           // Disable default OS window decoration flag for secondary viewports. When a viewport doesn't want window decorations, ImGuiViewportFlags_NoDecoration will be set on it. Enabling decoration can create subsequent issues at OS levels (e.g. minimum window size).
+    bool        ConfigViewportsNoDefaultParent; // = false          // Disable default OS parenting to main viewport for secondary viewports. By default, viewports are marked with ParentViewportId = <main_viewport>, expecting the platform backend to setup a parent/child relationship between the OS windows (some backend may ignore this). Set to true if you want the default to be 0, then all viewports will be top-level OS windows.
+
     // Miscellaneous options
     bool        MouseDrawCursor;                // = false          // Request ImGui to draw a mouse cursor for you (if you are on a platform without a mouse cursor). Cannot be easily renamed to 'io.ConfigXXX' because this is frequently used by backend implementations.
     bool        ConfigMacOSXBehaviors;          // = defined(__APPLE__) // Swap Cmd<>Ctrl keys + OS X style text editing cursor movement using Alt instead of Ctrl, Shortcuts using Cmd/Super instead of Ctrl, Line/Text Start and End using Cmd+Arrows instead of Home/End, Double click selects by word instead of selecting whole text, Multi-selection in lists uses Cmd/Super instead of Ctrl.
@@ -2175,7 +2269,7 @@
     // - Backends may have other side-effects on focus loss, so this will reduce side-effects but not necessary remove all of them.
     bool        ConfigDebugIgnoreFocusLoss;     // = false          // Ignore io.AddFocusEvent(false), consequently not calling io.ClearInputKeys() in input processing.
 
-    // Options to audit .ini data
+    // Option to audit .ini data
     bool        ConfigDebugIniSettings;         // = false          // Save .ini data with extra comments (particularly helpful for Docking, but makes saving slower)
 
     //------------------------------------------------------------------
@@ -2214,6 +2308,7 @@
     IMGUI_API void  AddMouseButtonEvent(int button, bool down);             // Queue a mouse button change
     IMGUI_API void  AddMouseWheelEvent(float wheel_x, float wheel_y);       // Queue a mouse wheel update. wheel_y<0: scroll down, wheel_y>0: scroll up, wheel_x<0: scroll right, wheel_x>0: scroll left.
     IMGUI_API void  AddMouseSourceEvent(ImGuiMouseSource source);           // Queue a mouse source change (Mouse/TouchScreen/Pen)
+    IMGUI_API void  AddMouseViewportEvent(ImGuiID id);                      // Queue a mouse hovered viewport. Requires backend to set ImGuiBackendFlags_HasMouseHoveredViewport to call this (for multi-viewport support).
     IMGUI_API void  AddFocusEvent(bool focused);                            // Queue a gain/loss of focus for the application (generally based on OS/platform focus of your window)
     IMGUI_API void  AddInputCharacter(unsigned int c);                      // Queue a new character input
     IMGUI_API void  AddInputCharacterUTF16(ImWchar16 c);                    // Queue a new character input from a UTF-16 character, it can be a surrogate
@@ -2261,6 +2356,7 @@
     float       MouseWheel;                         // Mouse wheel Vertical: 1 unit scrolls about 5 lines text. >0 scrolls Up, <0 scrolls Down. Hold SHIFT to turn vertical scroll into horizontal scroll.
     float       MouseWheelH;                        // Mouse wheel Horizontal. >0 scrolls Left, <0 scrolls Right. Most users don't have a mouse with a horizontal wheel, may not be filled by all backends.
     ImGuiMouseSource MouseSource;                   // Mouse actual input peripheral (Mouse/TouchScreen/Pen).
+    ImGuiID     MouseHoveredViewport;               // (Optional) Modify using io.AddMouseViewportEvent(). With multi-viewports: viewport the OS mouse is hovering. If possible _IGNORING_ viewports with the ImGuiViewportFlags_NoInputs flag is much better (few backends can handle that). Set io.BackendFlags |= ImGuiBackendFlags_HasMouseHoveredViewport if you can provide this info. If you don't imgui will infer the value using the rectangles and last focused time of the viewports it knows about (ignoring other OS windows).
     bool        KeyCtrl;                            // Keyboard modifier down: Control
     bool        KeyShift;                           // Keyboard modifier down: Shift
     bool        KeyAlt;                             // Keyboard modifier down: Alt
@@ -2284,6 +2380,7 @@
     bool        MouseCtrlLeftAsRightClick;          // (OSX) Set to true when the current click was a ctrl-click that spawned a simulated right click
     float       MouseDownDuration[5];               // Duration the mouse button has been down (0.0f == just clicked)
     float       MouseDownDurationPrev[5];           // Previous time the mouse button has been down
+    ImVec2      MouseDragMaxDistanceAbs[5];         // Maximum distance, absolute, on each axis, of how much mouse has traveled from the clicking point
     float       MouseDragMaxDistanceSqr[5];         // Squared maximum distance of how much mouse has traveled from the clicking point (used for moving thresholds)
     float       PenPressure;                        // Touch/Pen pressure (0.0f to 1.0f, should be >0.0f only when MouseDown[0] == true). Helper storage currently unused by Dear ImGui.
     bool        AppFocusLost;                       // Only modify via AddFocusEvent()
@@ -2361,6 +2458,28 @@
     ImVec2  DesiredSize;    // Read-write.  Desired size, based on user's mouse position. Write to this field to restrain resizing.
 };
 
+// [ALPHA] Rarely used / very advanced uses only. Use with SetNextWindowClass() and DockSpace() functions.
+// Important: the content of this class is still highly WIP and likely to change and be refactored
+// before we stabilize Docking features. Please be mindful if using this.
+// Provide hints:
+// - To the platform backend via altered viewport flags (enable/disable OS decoration, OS task bar icons, etc.)
+// - To the platform backend for OS level parent/child relationships of viewport.
+// - To the docking system for various options and filtering.
+struct ImGuiWindowClass
+{
+    ImGuiID             ClassId;                    // User data. 0 = Default class (unclassed). Windows of different classes cannot be docked with each others.
+    ImGuiID             ParentViewportId;           // Hint for the platform backend. -1: use default. 0: request platform backend to not parent the platform. != 0: request platform backend to create a parent<>child relationship between the platform windows. Not conforming backends are free to e.g. parent every viewport to the main viewport or not.
+    ImGuiID             FocusRouteParentWindowId;   // ID of parent window for shortcut focus route evaluation, e.g. Shortcut() call from Parent Window will succeed when this window is focused.
+    ImGuiViewportFlags  ViewportFlagsOverrideSet;   // Viewport flags to set when a window of this class owns a viewport. This allows you to enforce OS decoration or task bar icon, override the defaults on a per-window basis.
+    ImGuiViewportFlags  ViewportFlagsOverrideClear; // Viewport flags to clear when a window of this class owns a viewport. This allows you to enforce OS decoration or task bar icon, override the defaults on a per-window basis.
+    ImGuiTabItemFlags   TabItemFlagsOverrideSet;    // [EXPERIMENTAL] TabItem flags to set when a window of this class gets submitted into a dock node tab bar. May use with ImGuiTabItemFlags_Leading or ImGuiTabItemFlags_Trailing.
+    ImGuiDockNodeFlags  DockNodeFlagsOverrideSet;   // [EXPERIMENTAL] Dock node flags to set when a window of this class is hosted by a dock node (it doesn't have to be selected!)
+    bool                DockingAlwaysTabBar;        // Set to true to enforce single floating windows of this class always having their own docking node (equivalent of setting the global io.ConfigDockingAlwaysTabBar)
+    bool                DockingAllowUnclassed;      // Set to true to allow windows of this class to be docked/merged with an unclassed window. // FIXME-DOCK: Move to DockNodeFlags override?
+
+    ImGuiWindowClass() { memset(this, 0, sizeof(*this)); ParentViewportId = (ImGuiID)-1; DockingAllowUnclassed = true; }
+};
+
 // Data payload for Drag and Drop operations: AcceptDragDropPayload(), GetDragDropPayload()
 struct ImGuiPayload
 {
@@ -2904,7 +3023,7 @@
 struct ImDrawData
 {
     bool                Valid;              // Only valid after Render() is called and before the next NewFrame() is called.
-    int                 CmdListsCount;      // Number of ImDrawList* to render (should always be == CmdLists.size)
+    int                 CmdListsCount;      // Number of ImDrawList* to render
     int                 TotalIdxCount;      // For convenience, sum of all ImDrawList's IdxBuffer.Size
     int                 TotalVtxCount;      // For convenience, sum of all ImDrawList's VtxBuffer.Size
     ImVector<ImDrawList*> CmdLists;         // Array of ImDrawList* to render. The ImDrawLists are owned by ImGuiContext and only pointed to from here.
@@ -3187,11 +3306,24 @@
     ImGuiViewportFlags_None                     = 0,
     ImGuiViewportFlags_IsPlatformWindow         = 1 << 0,   // Represent a Platform Window
     ImGuiViewportFlags_IsPlatformMonitor        = 1 << 1,   // Represent a Platform Monitor (unused yet)
-    ImGuiViewportFlags_OwnedByApp               = 1 << 2,   // Platform Window: is created/managed by the application (rather than a dear imgui backend)
+    ImGuiViewportFlags_OwnedByApp               = 1 << 2,   // Platform Window: Was created/managed by the user application? (rather than our backend)
+    ImGuiViewportFlags_NoDecoration             = 1 << 3,   // Platform Window: Disable platform decorations: title bar, borders, etc. (generally set all windows, but if ImGuiConfigFlags_ViewportsDecoration is set we only set this on popups/tooltips)
+    ImGuiViewportFlags_NoTaskBarIcon            = 1 << 4,   // Platform Window: Disable platform task bar icon (generally set on popups/tooltips, or all windows if ImGuiConfigFlags_ViewportsNoTaskBarIcon is set)
+    ImGuiViewportFlags_NoFocusOnAppearing       = 1 << 5,   // Platform Window: Don't take focus when created.
+    ImGuiViewportFlags_NoFocusOnClick           = 1 << 6,   // Platform Window: Don't take focus when clicked on.
+    ImGuiViewportFlags_NoInputs                 = 1 << 7,   // Platform Window: Make mouse pass through so we can drag this window while peaking behind it.
+    ImGuiViewportFlags_NoRendererClear          = 1 << 8,   // Platform Window: Renderer doesn't need to clear the framebuffer ahead (because we will fill it entirely).
+    ImGuiViewportFlags_NoAutoMerge              = 1 << 9,   // Platform Window: Avoid merging this window into another host window. This can only be set via ImGuiWindowClass viewport flags override (because we need to now ahead if we are going to create a viewport in the first place!).
+    ImGuiViewportFlags_TopMost                  = 1 << 10,  // Platform Window: Display on top (for tooltips only).
+    ImGuiViewportFlags_CanHostOtherWindows      = 1 << 11,  // Viewport can host multiple imgui windows (secondary viewports are associated to a single window). // FIXME: In practice there's still probably code making the assumption that this is always and only on the MainViewport. Will fix once we add support for "no main viewport".
+
+    // Output status flags (from Platform)
+    ImGuiViewportFlags_IsMinimized              = 1 << 12,  // Platform Window: Window is minimized, can skip render. When minimized we tend to avoid using the viewport pos/size for clipping window or testing if they are contained in the viewport.
+    ImGuiViewportFlags_IsFocused                = 1 << 13,  // Platform Window: Window is focused (last call to Platform_GetWindowFocus() returned true)
 };
 
 // - Currently represents the Platform Window created by the application which is hosting our Dear ImGui windows.
-// - In 'docking' branch with multi-viewport enabled, we extend this concept to have multiple active viewports.
+// - With multi-viewport enabled, we extend this concept to have multiple active viewports.
 // - In the future we will extend this concept further to also represent Platform Monitor and support a "no main platform window" operation mode.
 // - About Main Area vs Work Area:
 //   - Main Area = entire viewport.
@@ -3205,11 +3337,26 @@
     ImVec2              Size;                   // Main Area: Size of the viewport.
     ImVec2              WorkPos;                // Work Area: Position of the viewport minus task bars, menus bars, status bars (>= Pos)
     ImVec2              WorkSize;               // Work Area: Size of the viewport minus task bars, menu bars, status bars (<= Size)
+    float               DpiScale;               // 1.0f = 96 DPI = No extra scale.
+    ImGuiID             ParentViewportId;       // (Advanced) 0: no parent. Instruct the platform backend to setup a parent/child relationship between platform windows.
+    ImDrawData*         DrawData;               // The ImDrawData corresponding to this viewport. Valid after Render() and until the next call to NewFrame().
 
     // Platform/Backend Dependent Data
-    void*               PlatformHandleRaw;      // void* to hold lower-level, platform-native window handle (under Win32 this is expected to be a HWND, unused for other platforms)
+    // Our design separate the Renderer and Platform backends to facilitate combining default backends with each others.
+    // When our create your own backend for a custom engine, it is possible that both Renderer and Platform will be handled
+    // by the same system and you may not need to use all the UserData/Handle fields.
+    // The library never uses those fields, they are merely storage to facilitate backend implementation.
+    void*               RendererUserData;       // void* to hold custom data structure for the renderer (e.g. swap chain, framebuffers etc.). generally set by your Renderer_CreateWindow function.
+    void*               PlatformUserData;       // void* to hold custom data structure for the OS / platform (e.g. windowing info, render context). generally set by your Platform_CreateWindow function.
+    void*               PlatformHandle;         // void* for FindViewportByPlatformHandle(). (e.g. suggested to use natural platform handle such as HWND, GLFWWindow*, SDL_Window*)
+    void*               PlatformHandleRaw;      // void* to hold lower-level, platform-native window handle (under Win32 this is expected to be a HWND, unused for other platforms), when using an abstraction layer like GLFW or SDL (where PlatformHandle would be a SDL_Window*)
+    bool                PlatformWindowCreated;  // Platform window has been created (Platform_CreateWindow() has been called). This is false during the first frame where a viewport is being created.
+    bool                PlatformRequestMove;    // Platform window requested move (e.g. window was moved by the OS / host window manager, authoritative position will be OS window position)
+    bool                PlatformRequestResize;  // Platform window requested resize (e.g. window was resized by the OS / host window manager, authoritative size will be OS window size)
+    bool                PlatformRequestClose;   // Platform window requested closure (e.g. window was moved by the OS / host window manager, e.g. pressing ALT-F4)
 
     ImGuiViewport()     { memset(this, 0, sizeof(*this)); }
+    ~ImGuiViewport()    { IM_ASSERT(PlatformUserData == NULL && RendererUserData == NULL); }
 
     // Helpers
     ImVec2              GetCenter() const       { return ImVec2(Pos.x + Size.x * 0.5f, Pos.y + Size.y * 0.5f); }
@@ -3217,8 +3364,126 @@
 };
 
 //-----------------------------------------------------------------------------
-// [SECTION] Platform Dependent Interfaces
+// [SECTION] Platform Dependent Interfaces (for e.g. multi-viewport support)
 //-----------------------------------------------------------------------------
+// [BETA] (Optional) This is completely optional, for advanced users!
+// If you are new to Dear ImGui and trying to integrate it into your engine, you can probably ignore this for now.
+//
+// This feature allows you to seamlessly drag Dear ImGui windows outside of your application viewport.
+// This is achieved by creating new Platform/OS windows on the fly, and rendering into them.
+// Dear ImGui manages the viewport structures, and the backend create and maintain one Platform/OS window for each of those viewports.
+//
+// See Glossary https://github.com/ocornut/imgui/wiki/Glossary for details about some of the terminology.
+// See Thread https://github.com/ocornut/imgui/issues/1542 for gifs, news and questions about this evolving feature.
+//
+// About the coordinates system:
+// - When multi-viewports are enabled, all Dear ImGui coordinates become absolute coordinates (same as OS coordinates!)
+// - So e.g. ImGui::SetNextWindowPos(ImVec2(0,0)) will position a window relative to your primary monitor!
+// - If you want to position windows relative to your main application viewport, use ImGui::GetMainViewport()->Pos as a base position.
+//
+// Steps to use multi-viewports in your application, when using a default backend from the examples/ folder:
+// - Application:  Enable feature with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
+// - Backend:      The backend initialization will setup all necessary ImGuiPlatformIO's functions and update monitors info every frame.
+// - Application:  In your main loop, call ImGui::UpdatePlatformWindows(), ImGui::RenderPlatformWindowsDefault() after EndFrame() or Render().
+// - Application:  Fix absolute coordinates used in ImGui::SetWindowPos() or ImGui::SetNextWindowPos() calls.
+//
+// Steps to use multi-viewports in your application, when using a custom backend:
+// - Important:    THIS IS NOT EASY TO DO and comes with many subtleties not described here!
+//                 It's also an experimental feature, so some of the requirements may evolve.
+//                 Consider using default backends if you can. Either way, carefully follow and refer to examples/ backends for details.
+// - Application:  Enable feature with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
+// - Backend:      Hook ImGuiPlatformIO's Platform_* and Renderer_* callbacks (see below).
+//                 Set 'io.BackendFlags |= ImGuiBackendFlags_PlatformHasViewports' and 'io.BackendFlags |= ImGuiBackendFlags_PlatformHasViewports'.
+//                 Update ImGuiPlatformIO's Monitors list every frame.
+//                 Update MousePos every frame, in absolute coordinates.
+// - Application:  In your main loop, call ImGui::UpdatePlatformWindows(), ImGui::RenderPlatformWindowsDefault() after EndFrame() or Render().
+//                 You may skip calling RenderPlatformWindowsDefault() if its API is not convenient for your needs. Read comments below.
+// - Application:  Fix absolute coordinates used in ImGui::SetWindowPos() or ImGui::SetNextWindowPos() calls.
+//
+// About ImGui::RenderPlatformWindowsDefault():
+// - This function is a mostly a _helper_ for the common-most cases, and to facilitate using default backends.
+// - You can check its simple source code to understand what it does.
+//   It basically iterates secondary viewports and call 4 functions that are setup in ImGuiPlatformIO, if available:
+//     Platform_RenderWindow(), Renderer_RenderWindow(), Platform_SwapBuffers(), Renderer_SwapBuffers()
+//   Those functions pointers exists only for the benefit of RenderPlatformWindowsDefault().
+// - If you have very specific rendering needs (e.g. flipping multiple swap-chain simultaneously, unusual sync/threading issues, etc.),
+//   you may be tempted to ignore RenderPlatformWindowsDefault() and write customized code to perform your renderingg.
+//   You may decide to setup the platform_io's *RenderWindow and *SwapBuffers pointers and call your functions through those pointers,
+//   or you may decide to never setup those pointers and call your code directly. They are a convenience, not an obligatory interface.
+//-----------------------------------------------------------------------------
+
+// (Optional) Access via ImGui::GetPlatformIO()
+struct ImGuiPlatformIO
+{
+    //------------------------------------------------------------------
+    // Input - Backend interface/functions + Monitor List
+    //------------------------------------------------------------------
+
+    // (Optional) Platform functions (e.g. Win32, GLFW, SDL2)
+    // For reference, the second column shows which function are generally calling the Platform Functions:
+    //   N = ImGui::NewFrame()                        ~ beginning of the dear imgui frame: read info from platform/OS windows (latest size/position)
+    //   F = ImGui::Begin(), ImGui::EndFrame()        ~ during the dear imgui frame
+    //   U = ImGui::UpdatePlatformWindows()           ~ after the dear imgui frame: create and update all platform/OS windows
+    //   R = ImGui::RenderPlatformWindowsDefault()    ~ render
+    //   D = ImGui::DestroyPlatformWindows()          ~ shutdown
+    // The general idea is that NewFrame() we will read the current Platform/OS state, and UpdatePlatformWindows() will write to it.
+    //
+    // The functions are designed so we can mix and match 2 imgui_impl_xxxx files, one for the Platform (~window/input handling), one for Renderer.
+    // Custom engine backends will often provide both Platform and Renderer interfaces and so may not need to use all functions.
+    // Platform functions are typically called before their Renderer counterpart, apart from Destroy which are called the other way.
+
+    // Platform function --------------------------------------------------- Called by -----
+    void    (*Platform_CreateWindow)(ImGuiViewport* vp);                    // . . U . .  // Create a new platform window for the given viewport
+    void    (*Platform_DestroyWindow)(ImGuiViewport* vp);                   // N . U . D  //
+    void    (*Platform_ShowWindow)(ImGuiViewport* vp);                      // . . U . .  // Newly created windows are initially hidden so SetWindowPos/Size/Title can be called on them before showing the window
+    void    (*Platform_SetWindowPos)(ImGuiViewport* vp, ImVec2 pos);        // . . U . .  // Set platform window position (given the upper-left corner of client area)
+    ImVec2  (*Platform_GetWindowPos)(ImGuiViewport* vp);                    // N . . . .  //
+    void    (*Platform_SetWindowSize)(ImGuiViewport* vp, ImVec2 size);      // . . U . .  // Set platform window client area size (ignoring OS decorations such as OS title bar etc.)
+    ImVec2  (*Platform_GetWindowSize)(ImGuiViewport* vp);                   // N . . . .  // Get platform window client area size
+    void    (*Platform_SetWindowFocus)(ImGuiViewport* vp);                  // N . . . .  // Move window to front and set input focus
+    bool    (*Platform_GetWindowFocus)(ImGuiViewport* vp);                  // . . U . .  //
+    bool    (*Platform_GetWindowMinimized)(ImGuiViewport* vp);              // N . . . .  // Get platform window minimized state. When minimized, we generally won't attempt to get/set size and contents will be culled more easily
+    void    (*Platform_SetWindowTitle)(ImGuiViewport* vp, const char* str); // . . U . .  // Set platform window title (given an UTF-8 string)
+    void    (*Platform_SetWindowAlpha)(ImGuiViewport* vp, float alpha);     // . . U . .  // (Optional) Setup global transparency (not per-pixel transparency)
+    void    (*Platform_UpdateWindow)(ImGuiViewport* vp);                    // . . U . .  // (Optional) Called by UpdatePlatformWindows(). Optional hook to allow the platform backend from doing general book-keeping every frame.
+    void    (*Platform_RenderWindow)(ImGuiViewport* vp, void* render_arg);  // . . . R .  // (Optional) Main rendering (platform side! This is often unused, or just setting a "current" context for OpenGL bindings). 'render_arg' is the value passed to RenderPlatformWindowsDefault().
+    void    (*Platform_SwapBuffers)(ImGuiViewport* vp, void* render_arg);   // . . . R .  // (Optional) Call Present/SwapBuffers (platform side! This is often unused!). 'render_arg' is the value passed to RenderPlatformWindowsDefault().
+    float   (*Platform_GetWindowDpiScale)(ImGuiViewport* vp);               // N . . . .  // (Optional) [BETA] FIXME-DPI: DPI handling: Return DPI scale for this viewport. 1.0f = 96 DPI.
+    void    (*Platform_OnChangedViewport)(ImGuiViewport* vp);               // . F . . .  // (Optional) [BETA] FIXME-DPI: DPI handling: Called during Begin() every time the viewport we are outputting into changes, so backend has a chance to swap fonts to adjust style.
+    int     (*Platform_CreateVkSurface)(ImGuiViewport* vp, ImU64 vk_inst, const void* vk_allocators, ImU64* out_vk_surface); // (Optional) For a Vulkan Renderer to call into Platform code (since the surface creation needs to tie them both).
+
+    // (Optional) Renderer functions (e.g. DirectX, OpenGL, Vulkan)
+    void    (*Renderer_CreateWindow)(ImGuiViewport* vp);                    // . . U . .  // Create swap chain, frame buffers etc. (called after Platform_CreateWindow)
+    void    (*Renderer_DestroyWindow)(ImGuiViewport* vp);                   // N . U . D  // Destroy swap chain, frame buffers etc. (called before Platform_DestroyWindow)
+    void    (*Renderer_SetWindowSize)(ImGuiViewport* vp, ImVec2 size);      // . . U . .  // Resize swap chain, frame buffers etc. (called after Platform_SetWindowSize)
+    void    (*Renderer_RenderWindow)(ImGuiViewport* vp, void* render_arg);  // . . . R .  // (Optional) Clear framebuffer, setup render target, then render the viewport->DrawData. 'render_arg' is the value passed to RenderPlatformWindowsDefault().
+    void    (*Renderer_SwapBuffers)(ImGuiViewport* vp, void* render_arg);   // . . . R .  // (Optional) Call Present/SwapBuffers. 'render_arg' is the value passed to RenderPlatformWindowsDefault().
+
+    // (Optional) Monitor list
+    // - Updated by: app/backend. Update every frame to dynamically support changing monitor or DPI configuration.
+    // - Used by: dear imgui to query DPI info, clamp popups/tooltips within same monitor and not have them straddle monitors.
+    ImVector<ImGuiPlatformMonitor>  Monitors;
+
+    //------------------------------------------------------------------
+    // Output - List of viewports to render into platform windows
+    //------------------------------------------------------------------
+
+    // Viewports list (the list is updated by calling ImGui::EndFrame or ImGui::Render)
+    // (in the future we will attempt to organize this feature to remove the need for a "main viewport")
+    ImVector<ImGuiViewport*>        Viewports;                              // Main viewports, followed by all secondary viewports.
+    ImGuiPlatformIO()               { memset(this, 0, sizeof(*this)); }     // Zero clear
+};
+
+// (Optional) This is required when enabling multi-viewport. Represent the bounds of each connected monitor/display and their DPI.
+// We use this information for multiple DPI support + clamping the position of popups and tooltips so they don't straddle multiple monitors.
+struct ImGuiPlatformMonitor
+{
+    ImVec2  MainPos, MainSize;      // Coordinates of the area displayed on this monitor (Min = upper left, Max = bottom right)
+    ImVec2  WorkPos, WorkSize;      // Coordinates without task bars / side bars / menu bars. Used to avoid positioning popups/tooltips inside this region. If you don't have this info, please copy the value for MainPos/MainSize.
+    float   DpiScale;               // 1.0f = 96 DPI
+    void*   PlatformHandle;         // Backend dependant data (e.g. HMONITOR, GLFWmonitor*, SDL Display Index, NSScreen*)
+    ImGuiPlatformMonitor()          { MainPos = MainSize = WorkPos = WorkSize = ImVec2(0, 0); DpiScale = 1.0f; PlatformHandle = NULL; }
+};
 
 // (Optional) Support for IME (Input Method Editor) via the io.SetPlatformImeDataFn() function.
 struct ImGuiPlatformImeData
diff --git a/imgui_demo.cpp b/imgui_demo.cpp
index cc81921..f3d3778 100644
--- a/imgui_demo.cpp
+++ b/imgui_demo.cpp
@@ -91,6 +91,7 @@
 // [SECTION] Example App: Fullscreen window / ShowExampleAppFullscreen()
 // [SECTION] Example App: Manipulating window titles / ShowExampleAppWindowTitles()
 // [SECTION] Example App: Custom Rendering using ImDrawList API / ShowExampleAppCustomRendering()
+// [SECTION] Example App: Docking, DockSpace / ShowExampleAppDockSpace()
 // [SECTION] Example App: Documents Handling / ShowExampleAppDocuments()
 
 */
@@ -198,6 +199,7 @@
 static void ShowExampleAppMainMenuBar();
 static void ShowExampleAppConsole(bool* p_open);
 static void ShowExampleAppCustomRendering(bool* p_open);
+static void ShowExampleAppDockSpace(bool* p_open);
 static void ShowExampleAppDocuments(bool* p_open);
 static void ShowExampleAppLog(bool* p_open);
 static void ShowExampleAppLayout(bool* p_open);
@@ -237,6 +239,16 @@
     }
 }
 
+static void ShowDockingDisabledMessage()
+{
+    ImGuiIO& io = ImGui::GetIO();
+    ImGui::Text("ERROR: Docking is not enabled! See Demo > Configuration.");
+    ImGui::Text("Set io.ConfigFlags |= ImGuiConfigFlags_DockingEnable in your code, or ");
+    ImGui::SameLine(0.0f, 0.0f);
+    if (ImGui::SmallButton("click here"))
+        io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;
+}
+
 // Helper to wire demo markers located in code to an interactive browser
 typedef void (*ImGuiDemoMarkerCallback)(const char* file, int line, const char* section, void* user_data);
 extern ImGuiDemoMarkerCallback      GImGuiDemoMarkerCallback;
@@ -273,6 +285,7 @@
     static bool show_app_main_menu_bar = false;
     static bool show_app_console = false;
     static bool show_app_custom_rendering = false;
+    static bool show_app_dockspace = false;
     static bool show_app_documents = false;
     static bool show_app_log = false;
     static bool show_app_layout = false;
@@ -285,7 +298,8 @@
     static bool show_app_window_titles = false;
 
     if (show_app_main_menu_bar)       ShowExampleAppMainMenuBar();
-    if (show_app_documents)           ShowExampleAppDocuments(&show_app_documents);
+    if (show_app_dockspace)           ShowExampleAppDockSpace(&show_app_dockspace);     // Process the Docking app first, as explicit DockSpace() nodes needs to be submitted early (read comments near the DockSpace function)
+    if (show_app_documents)           ShowExampleAppDocuments(&show_app_documents);     // Process the Document app next, as it may also use a DockSpace()
     if (show_app_console)             ShowExampleAppConsole(&show_app_console);
     if (show_app_custom_rendering)    ShowExampleAppCustomRendering(&show_app_custom_rendering);
     if (show_app_log)                 ShowExampleAppLog(&show_app_log);
@@ -331,6 +345,7 @@
     static bool no_nav = false;
     static bool no_background = false;
     static bool no_bring_to_front = false;
+    static bool no_docking = false;
     static bool unsaved_document = false;
 
     ImGuiWindowFlags window_flags = 0;
@@ -343,6 +358,7 @@
     if (no_nav)             window_flags |= ImGuiWindowFlags_NoNav;
     if (no_background)      window_flags |= ImGuiWindowFlags_NoBackground;
     if (no_bring_to_front)  window_flags |= ImGuiWindowFlags_NoBringToFrontOnFocus;
+    if (no_docking)         window_flags |= ImGuiWindowFlags_NoDocking;
     if (unsaved_document)   window_flags |= ImGuiWindowFlags_UnsavedDocument;
     if (no_close)           p_open = NULL; // Don't pass our bool* to Begin
 
@@ -383,6 +399,7 @@
             ImGui::SeparatorText("Mini apps");
             ImGui::MenuItem("Console", NULL, &show_app_console);
             ImGui::MenuItem("Custom rendering", NULL, &show_app_custom_rendering);
+            ImGui::MenuItem("Dockspace", NULL, &show_app_dockspace);
             ImGui::MenuItem("Documents", NULL, &show_app_documents);
             ImGui::MenuItem("Log", NULL, &show_app_log);
             ImGui::MenuItem("Property editor", NULL, &show_app_property_editor);
@@ -475,11 +492,50 @@
             }
             ImGui::CheckboxFlags("io.ConfigFlags: NoMouseCursorChange", &io.ConfigFlags, ImGuiConfigFlags_NoMouseCursorChange);
             ImGui::SameLine(); HelpMarker("Instruct backend to not alter mouse cursor shape and visibility.");
+
             ImGui::Checkbox("io.ConfigInputTrickleEventQueue", &io.ConfigInputTrickleEventQueue);
             ImGui::SameLine(); HelpMarker("Enable input queue trickling: some types of events submitted during the same frame (e.g. button down + up) will be spread over multiple frames, improving interactions with low framerates.");
             ImGui::Checkbox("io.MouseDrawCursor", &io.MouseDrawCursor);
             ImGui::SameLine(); HelpMarker("Instruct Dear ImGui to render a mouse cursor itself. Note that a mouse cursor rendered via your application GPU rendering path will feel more laggy than hardware cursor, but will be more in sync with your other visuals.\n\nSome desktop applications may use both kinds of cursors (e.g. enable software cursor only when resizing/dragging something).");
 
+            ImGui::SeparatorText("Docking");
+            ImGui::CheckboxFlags("io.ConfigFlags: DockingEnable", &io.ConfigFlags, ImGuiConfigFlags_DockingEnable);
+            ImGui::SameLine();
+            if (io.ConfigDockingWithShift)
+                HelpMarker("Drag from window title bar or their tab to dock/undock. Hold SHIFT to enable docking.\n\nDrag from window menu button (upper-left button) to undock an entire node (all windows).");
+            else
+                HelpMarker("Drag from window title bar or their tab to dock/undock. Hold SHIFT to disable docking.\n\nDrag from window menu button (upper-left button) to undock an entire node (all windows).");
+            if (io.ConfigFlags & ImGuiConfigFlags_DockingEnable)
+            {
+                ImGui::Indent();
+                ImGui::Checkbox("io.ConfigDockingNoSplit", &io.ConfigDockingNoSplit);
+                ImGui::SameLine(); HelpMarker("Simplified docking mode: disable window splitting, so docking is limited to merging multiple windows together into tab-bars.");
+                ImGui::Checkbox("io.ConfigDockingWithShift", &io.ConfigDockingWithShift);
+                ImGui::SameLine(); HelpMarker("Enable docking when holding Shift only (allow to drop in wider space, reduce visual noise)");
+                ImGui::Checkbox("io.ConfigDockingAlwaysTabBar", &io.ConfigDockingAlwaysTabBar);
+                ImGui::SameLine(); HelpMarker("Create a docking node and tab-bar on single floating windows.");
+                ImGui::Checkbox("io.ConfigDockingTransparentPayload", &io.ConfigDockingTransparentPayload);
+                ImGui::SameLine(); HelpMarker("Make window or viewport transparent when docking and only display docking boxes on the target viewport. Useful if rendering of multiple viewport cannot be synced. Best used with ConfigViewportsNoAutoMerge.");
+                ImGui::Unindent();
+            }
+
+            ImGui::SeparatorText("Multi-viewports");
+            ImGui::CheckboxFlags("io.ConfigFlags: ViewportsEnable", &io.ConfigFlags, ImGuiConfigFlags_ViewportsEnable);
+            ImGui::SameLine(); HelpMarker("[beta] Enable beta multi-viewports support. See ImGuiPlatformIO for details.");
+            if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+            {
+                ImGui::Indent();
+                ImGui::Checkbox("io.ConfigViewportsNoAutoMerge", &io.ConfigViewportsNoAutoMerge);
+                ImGui::SameLine(); HelpMarker("Set to make all floating imgui windows always create their own viewport. Otherwise, they are merged into the main host viewports when overlapping it.");
+                ImGui::Checkbox("io.ConfigViewportsNoTaskBarIcon", &io.ConfigViewportsNoTaskBarIcon);
+                ImGui::SameLine(); HelpMarker("Toggling this at runtime is normally unsupported (most platform backends won't refresh the task bar icon state right away).");
+                ImGui::Checkbox("io.ConfigViewportsNoDecoration", &io.ConfigViewportsNoDecoration);
+                ImGui::SameLine(); HelpMarker("Toggling this at runtime is normally unsupported (most platform backends won't refresh the decoration right away).");
+                ImGui::Checkbox("io.ConfigViewportsNoDefaultParent", &io.ConfigViewportsNoDefaultParent);
+                ImGui::SameLine(); HelpMarker("Toggling this at runtime is normally unsupported (most platform backends won't refresh the parenting right away).");
+                ImGui::Unindent();
+            }
+
             ImGui::SeparatorText("Widgets");
             ImGui::Checkbox("io.ConfigInputTextCursorBlink", &io.ConfigInputTextCursorBlink);
             ImGui::SameLine(); HelpMarker("Enable blinking cursor (optional as some users consider it to be distracting).");
@@ -519,12 +575,16 @@
                 "Those flags are set by the backends (imgui_impl_xxx files) to specify their capabilities.\n"
                 "Here we expose them as read-only fields to avoid breaking interactions with your backend.");
 
+            // Make a local copy to avoid modifying actual backend flags.
             // FIXME: Maybe we need a BeginReadonly() equivalent to keep label bright?
             ImGui::BeginDisabled();
-            ImGui::CheckboxFlags("io.BackendFlags: HasGamepad",           &io.BackendFlags, ImGuiBackendFlags_HasGamepad);
-            ImGui::CheckboxFlags("io.BackendFlags: HasMouseCursors",      &io.BackendFlags, ImGuiBackendFlags_HasMouseCursors);
-            ImGui::CheckboxFlags("io.BackendFlags: HasSetMousePos",       &io.BackendFlags, ImGuiBackendFlags_HasSetMousePos);
-            ImGui::CheckboxFlags("io.BackendFlags: RendererHasVtxOffset", &io.BackendFlags, ImGuiBackendFlags_RendererHasVtxOffset);
+            ImGui::CheckboxFlags("io.BackendFlags: HasGamepad",             &io.BackendFlags, ImGuiBackendFlags_HasGamepad);
+            ImGui::CheckboxFlags("io.BackendFlags: HasMouseCursors",        &io.BackendFlags, ImGuiBackendFlags_HasMouseCursors);
+            ImGui::CheckboxFlags("io.BackendFlags: HasSetMousePos",         &io.BackendFlags, ImGuiBackendFlags_HasSetMousePos);
+            ImGui::CheckboxFlags("io.BackendFlags: PlatformHasViewports",   &io.BackendFlags, ImGuiBackendFlags_PlatformHasViewports);
+            ImGui::CheckboxFlags("io.BackendFlags: HasMouseHoveredViewport",&io.BackendFlags, ImGuiBackendFlags_HasMouseHoveredViewport);
+            ImGui::CheckboxFlags("io.BackendFlags: RendererHasVtxOffset",   &io.BackendFlags, ImGuiBackendFlags_RendererHasVtxOffset);
+            ImGui::CheckboxFlags("io.BackendFlags: RendererHasViewports",   &io.BackendFlags, ImGuiBackendFlags_RendererHasViewports);
             ImGui::EndDisabled();
             ImGui::TreePop();
             ImGui::Spacing();
@@ -574,6 +634,7 @@
             ImGui::TableNextColumn(); ImGui::Checkbox("No nav", &no_nav);
             ImGui::TableNextColumn(); ImGui::Checkbox("No background", &no_background);
             ImGui::TableNextColumn(); ImGui::Checkbox("No bring to front", &no_bring_to_front);
+            ImGui::TableNextColumn(); ImGui::Checkbox("No docking", &no_docking);
             ImGui::TableNextColumn(); ImGui::Checkbox("Unsaved document", &unsaved_document);
             ImGui::EndTable();
         }
@@ -2658,18 +2719,24 @@
             "IsWindowFocused() = %d\n"
             "IsWindowFocused(_ChildWindows) = %d\n"
             "IsWindowFocused(_ChildWindows|_NoPopupHierarchy) = %d\n"
+            "IsWindowFocused(_ChildWindows|_DockHierarchy) = %d\n"
             "IsWindowFocused(_ChildWindows|_RootWindow) = %d\n"
             "IsWindowFocused(_ChildWindows|_RootWindow|_NoPopupHierarchy) = %d\n"
+            "IsWindowFocused(_ChildWindows|_RootWindow|_DockHierarchy) = %d\n"
             "IsWindowFocused(_RootWindow) = %d\n"
             "IsWindowFocused(_RootWindow|_NoPopupHierarchy) = %d\n"
+            "IsWindowFocused(_RootWindow|_DockHierarchy) = %d\n"
             "IsWindowFocused(_AnyWindow) = %d\n",
             ImGui::IsWindowFocused(),
             ImGui::IsWindowFocused(ImGuiFocusedFlags_ChildWindows),
             ImGui::IsWindowFocused(ImGuiFocusedFlags_ChildWindows | ImGuiFocusedFlags_NoPopupHierarchy),
+            ImGui::IsWindowFocused(ImGuiFocusedFlags_ChildWindows | ImGuiFocusedFlags_DockHierarchy),
             ImGui::IsWindowFocused(ImGuiFocusedFlags_ChildWindows | ImGuiFocusedFlags_RootWindow),
             ImGui::IsWindowFocused(ImGuiFocusedFlags_ChildWindows | ImGuiFocusedFlags_RootWindow | ImGuiFocusedFlags_NoPopupHierarchy),
+            ImGui::IsWindowFocused(ImGuiFocusedFlags_ChildWindows | ImGuiFocusedFlags_RootWindow | ImGuiFocusedFlags_DockHierarchy),
             ImGui::IsWindowFocused(ImGuiFocusedFlags_RootWindow),
             ImGui::IsWindowFocused(ImGuiFocusedFlags_RootWindow | ImGuiFocusedFlags_NoPopupHierarchy),
+            ImGui::IsWindowFocused(ImGuiFocusedFlags_RootWindow | ImGuiFocusedFlags_DockHierarchy),
             ImGui::IsWindowFocused(ImGuiFocusedFlags_AnyWindow));
 
         // Testing IsWindowHovered() function with its various flags.
@@ -2679,10 +2746,13 @@
             "IsWindowHovered(_AllowWhenBlockedByActiveItem) = %d\n"
             "IsWindowHovered(_ChildWindows) = %d\n"
             "IsWindowHovered(_ChildWindows|_NoPopupHierarchy) = %d\n"
+            "IsWindowHovered(_ChildWindows|_DockHierarchy) = %d\n"
             "IsWindowHovered(_ChildWindows|_RootWindow) = %d\n"
             "IsWindowHovered(_ChildWindows|_RootWindow|_NoPopupHierarchy) = %d\n"
+            "IsWindowHovered(_ChildWindows|_RootWindow|_DockHierarchy) = %d\n"
             "IsWindowHovered(_RootWindow) = %d\n"
             "IsWindowHovered(_RootWindow|_NoPopupHierarchy) = %d\n"
+            "IsWindowHovered(_RootWindow|_DockHierarchy) = %d\n"
             "IsWindowHovered(_ChildWindows|_AllowWhenBlockedByPopup) = %d\n"
             "IsWindowHovered(_AnyWindow) = %d\n"
             "IsWindowHovered(_Stationary) = %d\n",
@@ -2691,10 +2761,13 @@
             ImGui::IsWindowHovered(ImGuiHoveredFlags_AllowWhenBlockedByActiveItem),
             ImGui::IsWindowHovered(ImGuiHoveredFlags_ChildWindows),
             ImGui::IsWindowHovered(ImGuiHoveredFlags_ChildWindows | ImGuiHoveredFlags_NoPopupHierarchy),
+            ImGui::IsWindowHovered(ImGuiHoveredFlags_ChildWindows | ImGuiHoveredFlags_DockHierarchy),
             ImGui::IsWindowHovered(ImGuiHoveredFlags_ChildWindows | ImGuiHoveredFlags_RootWindow),
             ImGui::IsWindowHovered(ImGuiHoveredFlags_ChildWindows | ImGuiHoveredFlags_RootWindow | ImGuiHoveredFlags_NoPopupHierarchy),
+            ImGui::IsWindowHovered(ImGuiHoveredFlags_ChildWindows | ImGuiHoveredFlags_RootWindow | ImGuiHoveredFlags_DockHierarchy),
             ImGui::IsWindowHovered(ImGuiHoveredFlags_RootWindow),
             ImGui::IsWindowHovered(ImGuiHoveredFlags_RootWindow | ImGuiHoveredFlags_NoPopupHierarchy),
+            ImGui::IsWindowHovered(ImGuiHoveredFlags_RootWindow | ImGuiHoveredFlags_DockHierarchy),
             ImGui::IsWindowHovered(ImGuiHoveredFlags_ChildWindows | ImGuiHoveredFlags_AllowWhenBlockedByPopup),
             ImGui::IsWindowHovered(ImGuiHoveredFlags_AnyWindow),
             ImGui::IsWindowHovered(ImGuiHoveredFlags_Stationary));
@@ -2707,10 +2780,13 @@
 
         // Calling IsItemHovered() after begin returns the hovered status of the title bar.
         // This is useful in particular if you want to create a context menu associated to the title bar of a window.
+        // This will also work when docked into a Tab (the Tab replace the Title Bar and guarantee the same properties).
         static bool test_window = false;
         ImGui::Checkbox("Hovered/Active tests after Begin() for title bar testing", &test_window);
         if (test_window)
         {
+            // FIXME-DOCK: This window cannot be docked within the ImGui Demo window, this will cause a feedback loop and get them stuck.
+            // Could we fix this through an ImGuiWindowClass feature? Or an API call to tag our parent as "don't skip items"?
             ImGui::Begin("Title bar Hovered/Active tests", &test_window);
             if (ImGui::BeginPopupContextItem()) // <-- This is using IsItemHovered()
             {
@@ -6565,6 +6641,12 @@
 #ifdef __EMSCRIPTEN__
         ImGui::Text("define: __EMSCRIPTEN__");
 #endif
+#ifdef IMGUI_HAS_VIEWPORT
+        ImGui::Text("define: IMGUI_HAS_VIEWPORT");
+#endif
+#ifdef IMGUI_HAS_DOCK
+        ImGui::Text("define: IMGUI_HAS_DOCK");
+#endif
         ImGui::Separator();
         ImGui::Text("io.BackendPlatformName: %s", io.BackendPlatformName ? io.BackendPlatformName : "NULL");
         ImGui::Text("io.BackendRendererName: %s", io.BackendRendererName ? io.BackendRendererName : "NULL");
@@ -6575,7 +6657,19 @@
         if (io.ConfigFlags & ImGuiConfigFlags_NavNoCaptureKeyboard)     ImGui::Text(" NavNoCaptureKeyboard");
         if (io.ConfigFlags & ImGuiConfigFlags_NoMouse)                  ImGui::Text(" NoMouse");
         if (io.ConfigFlags & ImGuiConfigFlags_NoMouseCursorChange)      ImGui::Text(" NoMouseCursorChange");
+        if (io.ConfigFlags & ImGuiConfigFlags_DockingEnable)            ImGui::Text(" DockingEnable");
+        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)          ImGui::Text(" ViewportsEnable");
+        if (io.ConfigFlags & ImGuiConfigFlags_DpiEnableScaleViewports)  ImGui::Text(" DpiEnableScaleViewports");
+        if (io.ConfigFlags & ImGuiConfigFlags_DpiEnableScaleFonts)      ImGui::Text(" DpiEnableScaleFonts");
         if (io.MouseDrawCursor)                                         ImGui::Text("io.MouseDrawCursor");
+        if (io.ConfigViewportsNoAutoMerge)                              ImGui::Text("io.ConfigViewportsNoAutoMerge");
+        if (io.ConfigViewportsNoTaskBarIcon)                            ImGui::Text("io.ConfigViewportsNoTaskBarIcon");
+        if (io.ConfigViewportsNoDecoration)                             ImGui::Text("io.ConfigViewportsNoDecoration");
+        if (io.ConfigViewportsNoDefaultParent)                          ImGui::Text("io.ConfigViewportsNoDefaultParent");
+        if (io.ConfigDockingNoSplit)                                    ImGui::Text("io.ConfigDockingNoSplit");
+        if (io.ConfigDockingWithShift)                                  ImGui::Text("io.ConfigDockingWithShift");
+        if (io.ConfigDockingAlwaysTabBar)                               ImGui::Text("io.ConfigDockingAlwaysTabBar");
+        if (io.ConfigDockingTransparentPayload)                         ImGui::Text("io.ConfigDockingTransparentPayload");
         if (io.ConfigMacOSXBehaviors)                                   ImGui::Text("io.ConfigMacOSXBehaviors");
         if (io.ConfigInputTextCursorBlink)                              ImGui::Text("io.ConfigInputTextCursorBlink");
         if (io.ConfigWindowsResizeFromEdges)                            ImGui::Text("io.ConfigWindowsResizeFromEdges");
@@ -6585,7 +6679,10 @@
         if (io.BackendFlags & ImGuiBackendFlags_HasGamepad)             ImGui::Text(" HasGamepad");
         if (io.BackendFlags & ImGuiBackendFlags_HasMouseCursors)        ImGui::Text(" HasMouseCursors");
         if (io.BackendFlags & ImGuiBackendFlags_HasSetMousePos)         ImGui::Text(" HasSetMousePos");
+        if (io.BackendFlags & ImGuiBackendFlags_PlatformHasViewports)   ImGui::Text(" PlatformHasViewports");
+        if (io.BackendFlags & ImGuiBackendFlags_HasMouseHoveredViewport)ImGui::Text(" HasMouseHoveredViewport");
         if (io.BackendFlags & ImGuiBackendFlags_RendererHasVtxOffset)   ImGui::Text(" RendererHasVtxOffset");
+        if (io.BackendFlags & ImGuiBackendFlags_RendererHasViewports)   ImGui::Text(" RendererHasViewports");
         ImGui::Separator();
         ImGui::Text("io.Fonts: %d fonts, Flags: 0x%08X, TexSize: %d,%d", io.Fonts->Fonts.Size, io.Fonts->Flags, io.Fonts->TexWidth, io.Fonts->TexHeight);
         ImGui::Text("io.DisplaySize: %.2f,%.2f", io.DisplaySize.x, io.DisplaySize.y);
@@ -6759,6 +6856,9 @@
             ImGui::SliderFloat2("SeparatorTextPadding", (float*)&style.SeparatorTextPadding, 0.0f, 40.0f, "%.0f");
             ImGui::SliderFloat("LogSliderDeadzone", &style.LogSliderDeadzone, 0.0f, 12.0f, "%.0f");
 
+            ImGui::SeparatorText("Docking");
+            ImGui::SliderFloat("DockingSplitterSize", &style.DockingSeparatorSize, 0.0f, 12.0f, "%.0f");
+
             ImGui::SeparatorText("Tooltips");
             for (int n = 0; n < 2; n++)
                 if (ImGui::TreeNodeEx(n == 0 ? "HoverFlagsForTooltipMouse" : "HoverFlagsForTooltipNav"))
@@ -7944,6 +8044,8 @@
         else
         {
             ImGui::Text("(Hold SHIFT to display a dummy viewport)");
+            if (ImGui::IsWindowDocked())
+                ImGui::Text("Warning: Sizing Constraints won't work if the window is docked!");
             if (ImGui::Button("Set 200x200")) { ImGui::SetWindowSize(ImVec2(200, 200)); } ImGui::SameLine();
             if (ImGui::Button("Set 500x500")) { ImGui::SetWindowSize(ImVec2(500, 500)); } ImGui::SameLine();
             if (ImGui::Button("Set 800x200")) { ImGui::SetWindowSize(ImVec2(800, 200)); }
@@ -7970,7 +8072,7 @@
 {
     static int location = 0;
     ImGuiIO& io = ImGui::GetIO();
-    ImGuiWindowFlags window_flags = ImGuiWindowFlags_NoDecoration | ImGuiWindowFlags_AlwaysAutoResize | ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_NoFocusOnAppearing | ImGuiWindowFlags_NoNav;
+    ImGuiWindowFlags window_flags = ImGuiWindowFlags_NoDecoration | ImGuiWindowFlags_NoDocking | ImGuiWindowFlags_AlwaysAutoResize | ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_NoFocusOnAppearing | ImGuiWindowFlags_NoNav;
     if (location >= 0)
     {
         const float PAD = 10.0f;
@@ -7983,6 +8085,7 @@
         window_pos_pivot.x = (location & 1) ? 1.0f : 0.0f;
         window_pos_pivot.y = (location & 2) ? 1.0f : 0.0f;
         ImGui::SetNextWindowPos(window_pos, ImGuiCond_Always, window_pos_pivot);
+        ImGui::SetNextWindowViewport(viewport->ID);
         window_flags |= ImGuiWindowFlags_NoMove;
     }
     else if (location == -2)
@@ -8403,6 +8506,134 @@
 }
 
 //-----------------------------------------------------------------------------
+// [SECTION] Example App: Docking, DockSpace / ShowExampleAppDockSpace()
+//-----------------------------------------------------------------------------
+
+// Demonstrate using DockSpace() to create an explicit docking node within an existing window.
+// Note: You can use most Docking facilities without calling any API. You DO NOT need to call DockSpace() to use Docking!
+// - Drag from window title bar or their tab to dock/undock. Hold SHIFT to disable docking.
+// - Drag from window menu button (upper-left button) to undock an entire node (all windows).
+// - When io.ConfigDockingWithShift == true, you instead need to hold SHIFT to enable docking.
+// About dockspaces:
+// - Use DockSpace() to create an explicit dock node _within_ an existing window.
+// - Use DockSpaceOverViewport() to create an explicit dock node covering the screen or a specific viewport.
+//   This is often used with ImGuiDockNodeFlags_PassthruCentralNode.
+// - Important: Dockspaces need to be submitted _before_ any window they can host. Submit it early in your frame! (*)
+// - Important: Dockspaces need to be kept alive if hidden, otherwise windows docked into it will be undocked.
+//   e.g. if you have multiple tabs with a dockspace inside each tab: submit the non-visible dockspaces with ImGuiDockNodeFlags_KeepAliveOnly.
+// (*) because of this constraint, the implicit \"Debug\" window can not be docked into an explicit DockSpace() node,
+// because that window is submitted as part of the part of the NewFrame() call. An easy workaround is that you can create
+// your own implicit "Debug##2" window after calling DockSpace() and leave it in the window stack for anyone to use.
+void ShowExampleAppDockSpace(bool* p_open)
+{
+    // READ THIS !!!
+    // TL;DR; this demo is more complicated than what most users you would normally use.
+    // If we remove all options we are showcasing, this demo would become:
+    //     void ShowExampleAppDockSpace()
+    //     {
+    //         ImGui::DockSpaceOverViewport(0, ImGui::GetMainViewport());
+    //     }
+    // In most cases you should be able to just call DockSpaceOverViewport() and ignore all the code below!
+    // In this specific demo, we are not using DockSpaceOverViewport() because:
+    // - (1) we allow the host window to be floating/moveable instead of filling the viewport (when opt_fullscreen == false)
+    // - (2) we allow the host window to have padding (when opt_padding == true)
+    // - (3) we expose many flags and need a way to have them visible.
+    // - (4) we have a local menu bar in the host window (vs. you could use BeginMainMenuBar() + DockSpaceOverViewport()
+    //      in your code, but we don't here because we allow the window to be floating)
+
+    static bool opt_fullscreen = true;
+    static bool opt_padding = false;
+    static ImGuiDockNodeFlags dockspace_flags = ImGuiDockNodeFlags_None;
+
+    // We are using the ImGuiWindowFlags_NoDocking flag to make the parent window not dockable into,
+    // because it would be confusing to have two docking targets within each others.
+    ImGuiWindowFlags window_flags = ImGuiWindowFlags_MenuBar | ImGuiWindowFlags_NoDocking;
+    if (opt_fullscreen)
+    {
+        const ImGuiViewport* viewport = ImGui::GetMainViewport();
+        ImGui::SetNextWindowPos(viewport->WorkPos);
+        ImGui::SetNextWindowSize(viewport->WorkSize);
+        ImGui::SetNextWindowViewport(viewport->ID);
+        ImGui::PushStyleVar(ImGuiStyleVar_WindowRounding, 0.0f);
+        ImGui::PushStyleVar(ImGuiStyleVar_WindowBorderSize, 0.0f);
+        window_flags |= ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoCollapse | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove;
+        window_flags |= ImGuiWindowFlags_NoBringToFrontOnFocus | ImGuiWindowFlags_NoNavFocus;
+    }
+    else
+    {
+        dockspace_flags &= ~ImGuiDockNodeFlags_PassthruCentralNode;
+    }
+
+    // When using ImGuiDockNodeFlags_PassthruCentralNode, DockSpace() will render our background
+    // and handle the pass-thru hole, so we ask Begin() to not render a background.
+    if (dockspace_flags & ImGuiDockNodeFlags_PassthruCentralNode)
+        window_flags |= ImGuiWindowFlags_NoBackground;
+
+    // Important: note that we proceed even if Begin() returns false (aka window is collapsed).
+    // This is because we want to keep our DockSpace() active. If a DockSpace() is inactive,
+    // all active windows docked into it will lose their parent and become undocked.
+    // We cannot preserve the docking relationship between an active window and an inactive docking, otherwise
+    // any change of dockspace/settings would lead to windows being stuck in limbo and never being visible.
+    if (!opt_padding)
+        ImGui::PushStyleVar(ImGuiStyleVar_WindowPadding, ImVec2(0.0f, 0.0f));
+    ImGui::Begin("DockSpace Demo", p_open, window_flags);
+    if (!opt_padding)
+        ImGui::PopStyleVar();
+
+    if (opt_fullscreen)
+        ImGui::PopStyleVar(2);
+
+    // Submit the DockSpace
+    ImGuiIO& io = ImGui::GetIO();
+    if (io.ConfigFlags & ImGuiConfigFlags_DockingEnable)
+    {
+        ImGuiID dockspace_id = ImGui::GetID("MyDockSpace");
+        ImGui::DockSpace(dockspace_id, ImVec2(0.0f, 0.0f), dockspace_flags);
+    }
+    else
+    {
+        ShowDockingDisabledMessage();
+    }
+
+    if (ImGui::BeginMenuBar())
+    {
+        if (ImGui::BeginMenu("Options"))
+        {
+            // Disabling fullscreen would allow the window to be moved to the front of other windows,
+            // which we can't undo at the moment without finer window depth/z control.
+            ImGui::MenuItem("Fullscreen", NULL, &opt_fullscreen);
+            ImGui::MenuItem("Padding", NULL, &opt_padding);
+            ImGui::Separator();
+
+            if (ImGui::MenuItem("Flag: NoDockingOverCentralNode", "", (dockspace_flags & ImGuiDockNodeFlags_NoDockingOverCentralNode) != 0)) { dockspace_flags ^= ImGuiDockNodeFlags_NoDockingOverCentralNode; }
+            if (ImGui::MenuItem("Flag: NoDockingSplit",         "", (dockspace_flags & ImGuiDockNodeFlags_NoDockingSplit) != 0))             { dockspace_flags ^= ImGuiDockNodeFlags_NoDockingSplit; }
+            if (ImGui::MenuItem("Flag: NoUndocking",            "", (dockspace_flags & ImGuiDockNodeFlags_NoUndocking) != 0))                { dockspace_flags ^= ImGuiDockNodeFlags_NoUndocking; }
+            if (ImGui::MenuItem("Flag: NoResize",               "", (dockspace_flags & ImGuiDockNodeFlags_NoResize) != 0))                   { dockspace_flags ^= ImGuiDockNodeFlags_NoResize; }
+            if (ImGui::MenuItem("Flag: AutoHideTabBar",         "", (dockspace_flags & ImGuiDockNodeFlags_AutoHideTabBar) != 0))             { dockspace_flags ^= ImGuiDockNodeFlags_AutoHideTabBar; }
+            if (ImGui::MenuItem("Flag: PassthruCentralNode",    "", (dockspace_flags & ImGuiDockNodeFlags_PassthruCentralNode) != 0, opt_fullscreen)) { dockspace_flags ^= ImGuiDockNodeFlags_PassthruCentralNode; }
+            ImGui::Separator();
+
+            if (ImGui::MenuItem("Close", NULL, false, p_open != NULL))
+                *p_open = false;
+            ImGui::EndMenu();
+        }
+        HelpMarker(
+            "When docking is enabled, you can ALWAYS dock MOST window into another! Try it now!" "\n"
+            "- Drag from window title bar or their tab to dock/undock." "\n"
+            "- Drag from window menu button (upper-left button) to undock an entire node (all windows)." "\n"
+            "- Hold SHIFT to disable docking (if io.ConfigDockingWithShift == false, default)" "\n"
+            "- Hold SHIFT to enable docking (if io.ConfigDockingWithShift == true)" "\n"
+            "This demo app has nothing to do with enabling docking!" "\n\n"
+            "This demo app only demonstrate the use of ImGui::DockSpace() which allows you to manually create a docking node _within_ another window." "\n\n"
+            "Read comments in ShowExampleAppDockSpace() for more details.");
+
+        ImGui::EndMenuBar();
+    }
+
+    ImGui::End();
+}
+
+//-----------------------------------------------------------------------------
 // [SECTION] Example App: Documents Handling / ShowExampleAppDocuments()
 //-----------------------------------------------------------------------------
 
@@ -8506,11 +8737,25 @@
     static ExampleAppDocuments app;
 
     // Options
+    enum Target
+    {
+        Target_None,
+        Target_Tab,                 // Create documents as local tab into a local tab bar
+        Target_DockSpaceAndWindow   // Create documents as regular windows, and create an embedded dockspace
+    };
+    static Target opt_target = Target_Tab;
     static bool opt_reorderable = true;
     static ImGuiTabBarFlags opt_fitting_flags = ImGuiTabBarFlags_FittingPolicyDefault_;
 
+    // When (opt_target == Target_DockSpaceAndWindow) there is the possibily that one of our child Document window (e.g. "Eggplant")
+    // that we emit gets docked into the same spot as the parent window ("Example: Documents").
+    // This would create a problematic feedback loop because selecting the "Eggplant" tab would make the "Example: Documents" tab
+    // not visible, which in turn would stop submitting the "Eggplant" window.
+    // We avoid this problem by submitting our documents window even if our parent window is not currently visible.
+    // Another solution may be to make the "Example: Documents" window use the ImGuiWindowFlags_NoDocking.
+
     bool window_contents_visible = ImGui::Begin("Example: Documents", p_open, ImGuiWindowFlags_MenuBar);
-    if (!window_contents_visible)
+    if (!window_contents_visible && opt_target != Target_DockSpaceAndWindow)
     {
         ImGui::End();
         return;
@@ -8554,6 +8799,12 @@
                 doc.DoForceClose();
         ImGui::PopID();
     }
+    ImGui::PushItemWidth(ImGui::GetFontSize() * 12);
+    ImGui::Combo("Output", (int*)&opt_target, "None\0TabBar+Tabs\0DockSpace+Window\0");
+    ImGui::PopItemWidth();
+    bool redock_all = false;
+    if (opt_target == Target_Tab)                { ImGui::SameLine(); ImGui::Checkbox("Reorderable Tabs", &opt_reorderable); }
+    if (opt_target == Target_DockSpaceAndWindow) { ImGui::SameLine(); redock_all = ImGui::Button("Redock all"); }
 
     ImGui::Separator();
 
@@ -8567,7 +8818,8 @@
     //   hole for one-frame, both in the tab-bar and in tab-contents when closing a tab/window.
     //   The rarely used SetTabItemClosed() function is a way to notify of programmatic closure to avoid the one-frame hole.
 
-    // Submit Tab Bar and Tabs
+    // Tabs
+    if (opt_target == Target_Tab)
     {
         ImGuiTabBarFlags tab_bar_flags = (opt_fitting_flags) | (opt_reorderable ? ImGuiTabBarFlags_Reorderable : 0);
         if (ImGui::BeginTabBar("##tabs", tab_bar_flags))
@@ -8606,6 +8858,53 @@
             ImGui::EndTabBar();
         }
     }
+    else if (opt_target == Target_DockSpaceAndWindow)
+    {
+        if (ImGui::GetIO().ConfigFlags & ImGuiConfigFlags_DockingEnable)
+        {
+            NotifyOfDocumentsClosedElsewhere(app);
+
+            // Create a DockSpace node where any window can be docked
+            ImGuiID dockspace_id = ImGui::GetID("MyDockSpace");
+            ImGui::DockSpace(dockspace_id);
+
+            // Create Windows
+            for (int doc_n = 0; doc_n < app.Documents.Size; doc_n++)
+            {
+                MyDocument* doc = &app.Documents[doc_n];
+                if (!doc->Open)
+                    continue;
+
+                ImGui::SetNextWindowDockID(dockspace_id, redock_all ? ImGuiCond_Always : ImGuiCond_FirstUseEver);
+                ImGuiWindowFlags window_flags = (doc->Dirty ? ImGuiWindowFlags_UnsavedDocument : 0);
+                bool visible = ImGui::Begin(doc->Name, &doc->Open, window_flags);
+
+                // Cancel attempt to close when unsaved add to save queue so we can display a popup.
+                if (!doc->Open && doc->Dirty)
+                {
+                    doc->Open = true;
+                    doc->DoQueueClose();
+                }
+
+                MyDocument::DisplayContextMenu(doc);
+                if (visible)
+                    MyDocument::DisplayContents(doc);
+
+                ImGui::End();
+            }
+        }
+        else
+        {
+            ShowDockingDisabledMessage();
+        }
+    }
+
+    // Early out other contents
+    if (!window_contents_visible)
+    {
+        ImGui::End();
+        return;
+    }
 
     // Update closing queue
     static ImVector<MyDocument*> close_queue;
diff --git a/imgui_draw.cpp b/imgui_draw.cpp
index 00b8948..393f417 100644
--- a/imgui_draw.cpp
+++ b/imgui_draw.cpp
@@ -216,6 +216,8 @@
     colors[ImGuiCol_TabActive]              = ImLerp(colors[ImGuiCol_HeaderActive], colors[ImGuiCol_TitleBgActive], 0.60f);
     colors[ImGuiCol_TabUnfocused]           = ImLerp(colors[ImGuiCol_Tab],          colors[ImGuiCol_TitleBg], 0.80f);
     colors[ImGuiCol_TabUnfocusedActive]     = ImLerp(colors[ImGuiCol_TabActive],    colors[ImGuiCol_TitleBg], 0.40f);
+    colors[ImGuiCol_DockingPreview]         = colors[ImGuiCol_HeaderActive] * ImVec4(1.0f, 1.0f, 1.0f, 0.7f);
+    colors[ImGuiCol_DockingEmptyBg]         = ImVec4(0.20f, 0.20f, 0.20f, 1.00f);
     colors[ImGuiCol_PlotLines]              = ImVec4(0.61f, 0.61f, 0.61f, 1.00f);
     colors[ImGuiCol_PlotLinesHovered]       = ImVec4(1.00f, 0.43f, 0.35f, 1.00f);
     colors[ImGuiCol_PlotHistogram]          = ImVec4(0.90f, 0.70f, 0.00f, 1.00f);
@@ -276,6 +278,8 @@
     colors[ImGuiCol_TabActive]              = ImLerp(colors[ImGuiCol_HeaderActive], colors[ImGuiCol_TitleBgActive], 0.60f);
     colors[ImGuiCol_TabUnfocused]           = ImLerp(colors[ImGuiCol_Tab],          colors[ImGuiCol_TitleBg], 0.80f);
     colors[ImGuiCol_TabUnfocusedActive]     = ImLerp(colors[ImGuiCol_TabActive],    colors[ImGuiCol_TitleBg], 0.40f);
+    colors[ImGuiCol_DockingPreview]         = colors[ImGuiCol_Header] * ImVec4(1.0f, 1.0f, 1.0f, 0.7f);
+    colors[ImGuiCol_DockingEmptyBg]         = ImVec4(0.20f, 0.20f, 0.20f, 1.00f);
     colors[ImGuiCol_PlotLines]              = ImVec4(1.00f, 1.00f, 1.00f, 1.00f);
     colors[ImGuiCol_PlotLinesHovered]       = ImVec4(0.90f, 0.70f, 0.00f, 1.00f);
     colors[ImGuiCol_PlotHistogram]          = ImVec4(0.90f, 0.70f, 0.00f, 1.00f);
@@ -337,6 +341,8 @@
     colors[ImGuiCol_TabActive]              = ImLerp(colors[ImGuiCol_HeaderActive], colors[ImGuiCol_TitleBgActive], 0.60f);
     colors[ImGuiCol_TabUnfocused]           = ImLerp(colors[ImGuiCol_Tab],          colors[ImGuiCol_TitleBg], 0.80f);
     colors[ImGuiCol_TabUnfocusedActive]     = ImLerp(colors[ImGuiCol_TabActive],    colors[ImGuiCol_TitleBg], 0.40f);
+    colors[ImGuiCol_DockingPreview]         = colors[ImGuiCol_Header] * ImVec4(1.0f, 1.0f, 1.0f, 0.7f);
+    colors[ImGuiCol_DockingEmptyBg]         = ImVec4(0.20f, 0.20f, 0.20f, 1.00f);
     colors[ImGuiCol_PlotLines]              = ImVec4(0.39f, 0.39f, 0.39f, 1.00f);
     colors[ImGuiCol_PlotLinesHovered]       = ImVec4(1.00f, 0.43f, 0.35f, 1.00f);
     colors[ImGuiCol_PlotHistogram]          = ImVec4(0.90f, 0.70f, 0.00f, 1.00f);
@@ -4196,6 +4202,7 @@
 // - RenderArrow()
 // - RenderBullet()
 // - RenderCheckMark()
+// - RenderArrowDockMenu()
 // - RenderArrowPointingAt()
 // - RenderRectFilledRangeH()
 // - RenderRectFilledWithHole()
@@ -4270,6 +4277,14 @@
     }
 }
 
+// This is less wide than RenderArrow() and we use in dock nodes instead of the regular RenderArrow() to denote a change of functionality,
+// and because the saved space means that the left-most tab label can stay at exactly the same position as the label of a loose window.
+void ImGui::RenderArrowDockMenu(ImDrawList* draw_list, ImVec2 p_min, float sz, ImU32 col)
+{
+    draw_list->AddRectFilled(p_min + ImVec2(sz * 0.20f, sz * 0.15f), p_min + ImVec2(sz * 0.80f, sz * 0.30f), col);
+    RenderArrowPointingAt(draw_list, p_min + ImVec2(sz * 0.50f, sz * 0.85f), ImVec2(sz * 0.30f, sz * 0.40f), ImGuiDir_Down, col);
+}
+
 static inline float ImAcos01(float x)
 {
     if (x <= 0.0f) return IM_PI * 0.5f;
@@ -4355,6 +4370,17 @@
     if (fill_R && fill_D) draw_list->AddRectFilled(ImVec2(inner.Max.x, inner.Max.y), ImVec2(outer.Max.x, outer.Max.y), col, rounding, ImDrawFlags_RoundCornersBottomRight);
 }
 
+ImDrawFlags ImGui::CalcRoundingFlagsForRectInRect(const ImRect& r_in, const ImRect& r_outer, float threshold)
+{
+    bool round_l = r_in.Min.x <= r_outer.Min.x + threshold;
+    bool round_r = r_in.Max.x >= r_outer.Max.x - threshold;
+    bool round_t = r_in.Min.y <= r_outer.Min.y + threshold;
+    bool round_b = r_in.Max.y >= r_outer.Max.y - threshold;
+    return ImDrawFlags_RoundCornersNone
+        | ((round_t && round_l) ? ImDrawFlags_RoundCornersTopLeft : 0) | ((round_t && round_r) ? ImDrawFlags_RoundCornersTopRight : 0)
+        | ((round_b && round_l) ? ImDrawFlags_RoundCornersBottomLeft : 0) | ((round_b && round_r) ? ImDrawFlags_RoundCornersBottomRight : 0);
+}
+
 // Helper for ColorPicker4()
 // NB: This is rather brittle and will show artifact when rounding this enabled if rounded corners overlap multiple cells. Caller currently responsible for avoiding that.
 // Spent a non reasonable amount of time trying to getting this right for ColorButton with rounding+anti-aliasing+ImGuiColorEditFlags_HalfAlphaPreview flag + various grid sizes and offsets, and eventually gave up... probably more reasonable to disable rounding altogether.
diff --git a/imgui_internal.h b/imgui_internal.h
index 37bbd78..7fb13d1 100644
--- a/imgui_internal.h
+++ b/imgui_internal.h
@@ -91,8 +91,9 @@
 #pragma clang diagnostic ignored "-Wunsafe-buffer-usage"            // warning: 'xxx' is an unsafe pointer used for buffer access
 #elif defined(__GNUC__)
 #pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wpragmas"              // warning: unknown option after '#pragma GCC diagnostic' kind
-#pragma GCC diagnostic ignored "-Wclass-memaccess"      // [__GNUC__ >= 8] warning: 'memset/memcpy' clearing/writing an object of type 'xxxx' with no trivial copy-assignment; use assignment or value-initialization instead
+#pragma GCC diagnostic ignored "-Wpragmas"                          // warning: unknown option after '#pragma GCC diagnostic' kind
+#pragma GCC diagnostic ignored "-Wclass-memaccess"                  // [__GNUC__ >= 8] warning: 'memset/memcpy' clearing/writing an object of type 'xxxx' with no trivial copy-assignment; use assignment or value-initialization instead
+#pragma GCC diagnostic ignored "-Wdeprecated-enum-enum-conversion"  // warning: bitwise operation between different enumeration types ('XXXFlags_' and 'XXXFlagsPrivate_') is deprecated
 #endif
 
 // In 1.89.4, we moved the implementation of "courtesy maths operators" from imgui_internal.h in imgui.h
@@ -128,6 +129,10 @@
 struct ImGuiContextHook;            // Hook for extensions like ImGuiTestEngine
 struct ImGuiDataVarInfo;            // Variable information (e.g. to access style variables from an enum)
 struct ImGuiDataTypeInfo;           // Type information associated to a ImGuiDataType enum
+struct ImGuiDockContext;            // Docking system context
+struct ImGuiDockRequest;            // Docking system dock/undock queued request
+struct ImGuiDockNode;               // Docking system node (hold a list of Windows OR two child dock nodes)
+struct ImGuiDockNodeSettings;       // Storage for a dock node in .ini file (we preserve those even if the associated dock node isn't active during the session)
 struct ImGuiGroupData;              // Stacked storage data for BeginGroup()/EndGroup()
 struct ImGuiInputTextState;         // Internal state of the currently focused/edited text input box
 struct ImGuiInputTextDeactivateData;// Short term storage to backup text of a deactivating InputText() while another is stealing active id
@@ -157,12 +162,14 @@
 struct ImGuiTypingSelectState;      // Storage for GetTypingSelectRequest()
 struct ImGuiTypingSelectRequest;    // Storage for GetTypingSelectRequest() (aimed to be public)
 struct ImGuiWindow;                 // Storage for one window
+struct ImGuiWindowDockStyle;        // Storage for window-style data which needs to be stored for docking purpose
 struct ImGuiWindowTempData;         // Temporary storage for one window (that's the data which in theory we could ditch at the end of the frame, in practice we currently keep it for each window)
 struct ImGuiWindowSettings;         // Storage for a window .ini settings (we keep one of those even if the actual window wasn't instanced during this session)
 
 // Enumerations
 // Use your programming IDE "Go to definition" facility on the names of the center columns to find the actual flags/enum lists.
 enum ImGuiLocKey : int;                 // -> enum ImGuiLocKey              // Enum: a localization entry for translation.
+typedef int ImGuiDataAuthority;         // -> enum ImGuiDataAuthority_      // Enum: for storing the source authority (dock node vs window) of a field
 typedef int ImGuiLayoutType;            // -> enum ImGuiLayoutType_         // Enum: Horizontal or vertical
 
 // Flags
@@ -216,6 +223,9 @@
 // [SECTION] Macros
 //-----------------------------------------------------------------------------
 
+// Internal Drag and Drop payload types. String starting with '_' are reserved for Dear ImGui.
+#define IMGUI_PAYLOAD_TYPE_WINDOW       "_IMWINDOW"     // Payload == ImGuiWindow*
+
 // Debug Printing Into TTY
 // (since IMGUI_VERSION_NUM >= 18729: IMGUI_DEBUG_LOG was reworked into IMGUI_DEBUG_PRINTF (and removed framecount from it). If you were using a #define IMGUI_DEBUG_LOG please rename)
 #ifndef IMGUI_DEBUG_PRINTF
@@ -240,6 +250,8 @@
 #define IMGUI_DEBUG_LOG_CLIPPER(...)    do { if (g.DebugLogFlags & ImGuiDebugLogFlags_EventClipper)     IMGUI_DEBUG_LOG(__VA_ARGS__); } while (0)
 #define IMGUI_DEBUG_LOG_IO(...)         do { if (g.DebugLogFlags & ImGuiDebugLogFlags_EventIO)          IMGUI_DEBUG_LOG(__VA_ARGS__); } while (0)
 #define IMGUI_DEBUG_LOG_INPUTROUTING(...) do{if (g.DebugLogFlags & ImGuiDebugLogFlags_EventInputRouting)IMGUI_DEBUG_LOG(__VA_ARGS__); } while (0)
+#define IMGUI_DEBUG_LOG_DOCKING(...)    do { if (g.DebugLogFlags & ImGuiDebugLogFlags_EventDocking)     IMGUI_DEBUG_LOG(__VA_ARGS__); } while (0)
+#define IMGUI_DEBUG_LOG_VIEWPORT(...)   do { if (g.DebugLogFlags & ImGuiDebugLogFlags_EventViewport)    IMGUI_DEBUG_LOG(__VA_ARGS__); } while (0)
 
 // Static Asserts
 #define IM_STATIC_ASSERT(_COND)         static_assert(_COND, "")
@@ -858,7 +870,7 @@
 enum ImGuiHoveredFlagsPrivate_
 {
     ImGuiHoveredFlags_DelayMask_                    = ImGuiHoveredFlags_DelayNone | ImGuiHoveredFlags_DelayShort | ImGuiHoveredFlags_DelayNormal | ImGuiHoveredFlags_NoSharedDelay,
-    ImGuiHoveredFlags_AllowedMaskForIsWindowHovered = ImGuiHoveredFlags_ChildWindows | ImGuiHoveredFlags_RootWindow | ImGuiHoveredFlags_AnyWindow | ImGuiHoveredFlags_NoPopupHierarchy | ImGuiHoveredFlags_AllowWhenBlockedByPopup | ImGuiHoveredFlags_AllowWhenBlockedByActiveItem | ImGuiHoveredFlags_ForTooltip | ImGuiHoveredFlags_Stationary,
+    ImGuiHoveredFlags_AllowedMaskForIsWindowHovered = ImGuiHoveredFlags_ChildWindows | ImGuiHoveredFlags_RootWindow | ImGuiHoveredFlags_AnyWindow | ImGuiHoveredFlags_NoPopupHierarchy | ImGuiHoveredFlags_DockHierarchy | ImGuiHoveredFlags_AllowWhenBlockedByPopup | ImGuiHoveredFlags_AllowWhenBlockedByActiveItem | ImGuiHoveredFlags_ForTooltip | ImGuiHoveredFlags_Stationary,
     ImGuiHoveredFlags_AllowedMaskForIsItemHovered   = ImGuiHoveredFlags_AllowWhenBlockedByPopup | ImGuiHoveredFlags_AllowWhenBlockedByActiveItem | ImGuiHoveredFlags_AllowWhenOverlapped | ImGuiHoveredFlags_AllowWhenDisabled | ImGuiHoveredFlags_NoNavOverride | ImGuiHoveredFlags_ForTooltip | ImGuiHoveredFlags_Stationary | ImGuiHoveredFlags_DelayMask_,
 };
 
@@ -1140,6 +1152,9 @@
     ImGuiNextWindowDataFlags_HasScroll          = 1 << 7,
     ImGuiNextWindowDataFlags_HasChildFlags      = 1 << 8,
     ImGuiNextWindowDataFlags_HasRefreshPolicy   = 1 << 9,
+    ImGuiNextWindowDataFlags_HasViewport        = 1 << 10,
+    ImGuiNextWindowDataFlags_HasDock            = 1 << 11,
+    ImGuiNextWindowDataFlags_HasWindowClass     = 1 << 12,
 };
 
 // Storage for SetNexWindow** functions
@@ -1149,17 +1164,22 @@
     ImGuiCond                   PosCond;
     ImGuiCond                   SizeCond;
     ImGuiCond                   CollapsedCond;
+    ImGuiCond                   DockCond;
     ImVec2                      PosVal;
     ImVec2                      PosPivotVal;
     ImVec2                      SizeVal;
     ImVec2                      ContentSizeVal;
     ImVec2                      ScrollVal;
     ImGuiChildFlags             ChildFlags;
+    bool                        PosUndock;
     bool                        CollapsedVal;
     ImRect                      SizeConstraintRect;
     ImGuiSizeCallback           SizeCallback;
     void*                       SizeCallbackUserData;
     float                       BgAlphaVal;             // Override background alpha
+    ImGuiID                     ViewportId;
+    ImGuiID                     DockId;
+    ImGuiWindowClass            WindowClass;
     ImVec2                      MenuBarOffsetMinVal;    // (Always on) This is not exposed publicly, so we don't clear it and it doesn't have a corresponding flag (could we? for consistency?)
     ImGuiWindowRefreshFlags     RefreshFlagsVal;
 
@@ -1357,6 +1377,7 @@
     ImGuiInputEventType_MousePos,
     ImGuiInputEventType_MouseWheel,
     ImGuiInputEventType_MouseButton,
+    ImGuiInputEventType_MouseViewport,
     ImGuiInputEventType_Key,
     ImGuiInputEventType_Text,
     ImGuiInputEventType_Focus,
@@ -1377,6 +1398,7 @@
 struct ImGuiInputEventMousePos      { float PosX, PosY; ImGuiMouseSource MouseSource; };
 struct ImGuiInputEventMouseWheel    { float WheelX, WheelY; ImGuiMouseSource MouseSource; };
 struct ImGuiInputEventMouseButton   { int Button; bool Down; ImGuiMouseSource MouseSource; };
+struct ImGuiInputEventMouseViewport { ImGuiID HoveredViewportID; };
 struct ImGuiInputEventKey           { ImGuiKey Key; bool Down; float AnalogValue; };
 struct ImGuiInputEventText          { unsigned int Char; };
 struct ImGuiInputEventAppFocused    { bool Focused; };
@@ -1391,6 +1413,7 @@
         ImGuiInputEventMousePos     MousePos;       // if Type == ImGuiInputEventType_MousePos
         ImGuiInputEventMouseWheel   MouseWheel;     // if Type == ImGuiInputEventType_MouseWheel
         ImGuiInputEventMouseButton  MouseButton;    // if Type == ImGuiInputEventType_MouseButton
+        ImGuiInputEventMouseViewport MouseViewport; // if Type == ImGuiInputEventType_MouseViewport
         ImGuiInputEventKey          Key;            // if Type == ImGuiInputEventType_Key
         ImGuiInputEventText         Text;           // if Type == ImGuiInputEventType_Text
         ImGuiInputEventAppFocused   AppFocused;     // if Type == ImGuiInputEventType_Focus
@@ -1713,8 +1736,150 @@
 // [SECTION] Docking support
 //-----------------------------------------------------------------------------
 
+#define DOCKING_HOST_DRAW_CHANNEL_BG 0  // Dock host: background fill
+#define DOCKING_HOST_DRAW_CHANNEL_FG 1  // Dock host: decorations and contents
+
 #ifdef IMGUI_HAS_DOCK
-// <this is filled in 'docking' branch>
+
+// Extend ImGuiDockNodeFlags_
+enum ImGuiDockNodeFlagsPrivate_
+{
+    // [Internal]
+    ImGuiDockNodeFlags_DockSpace                = 1 << 10,  // Saved // A dockspace is a node that occupy space within an existing user window. Otherwise the node is floating and create its own window.
+    ImGuiDockNodeFlags_CentralNode              = 1 << 11,  // Saved // The central node has 2 main properties: stay visible when empty, only use "remaining" spaces from its neighbor.
+    ImGuiDockNodeFlags_NoTabBar                 = 1 << 12,  // Saved // Tab bar is completely unavailable. No triangle in the corner to enable it back.
+    ImGuiDockNodeFlags_HiddenTabBar             = 1 << 13,  // Saved // Tab bar is hidden, with a triangle in the corner to show it again (NB: actual tab-bar instance may be destroyed as this is only used for single-window tab bar)
+    ImGuiDockNodeFlags_NoWindowMenuButton       = 1 << 14,  // Saved // Disable window/docking menu (that one that appears instead of the collapse button)
+    ImGuiDockNodeFlags_NoCloseButton            = 1 << 15,  // Saved // Disable close button
+    ImGuiDockNodeFlags_NoResizeX                = 1 << 16,  //       //
+    ImGuiDockNodeFlags_NoResizeY                = 1 << 17,  //       //
+    ImGuiDockNodeFlags_DockedWindowsInFocusRoute= 1 << 18,  //       // Any docked window will be automatically be focus-route chained (window->ParentWindowForFocusRoute set to this) so Shortcut() in this window can run when any docked window is focused.
+    // Disable docking/undocking actions in this dockspace or individual node (existing docked nodes will be preserved)
+    // Those are not exposed in public because the desirable sharing/inheriting/copy-flag-on-split behaviors are quite difficult to design and understand.
+    // The two public flags ImGuiDockNodeFlags_NoDockingOverCentralNode/ImGuiDockNodeFlags_NoDockingSplit don't have those issues.
+    ImGuiDockNodeFlags_NoDockingSplitOther      = 1 << 19,  //       // Disable this node from splitting other windows/nodes.
+    ImGuiDockNodeFlags_NoDockingOverMe          = 1 << 20,  //       // Disable other windows/nodes from being docked over this node.
+    ImGuiDockNodeFlags_NoDockingOverOther       = 1 << 21,  //       // Disable this node from being docked over another window or non-empty node.
+    ImGuiDockNodeFlags_NoDockingOverEmpty       = 1 << 22,  //       // Disable this node from being docked over an empty node (e.g. DockSpace with no other windows)
+    ImGuiDockNodeFlags_NoDocking                = ImGuiDockNodeFlags_NoDockingOverMe | ImGuiDockNodeFlags_NoDockingOverOther | ImGuiDockNodeFlags_NoDockingOverEmpty | ImGuiDockNodeFlags_NoDockingSplit | ImGuiDockNodeFlags_NoDockingSplitOther,
+    // Masks
+    ImGuiDockNodeFlags_SharedFlagsInheritMask_  = ~0,
+    ImGuiDockNodeFlags_NoResizeFlagsMask_       = ImGuiDockNodeFlags_NoResize | ImGuiDockNodeFlags_NoResizeX | ImGuiDockNodeFlags_NoResizeY,
+    // When splitting, those local flags are moved to the inheriting child, never duplicated
+    ImGuiDockNodeFlags_LocalFlagsTransferMask_  = ImGuiDockNodeFlags_NoDockingSplit | ImGuiDockNodeFlags_NoResizeFlagsMask_ | ImGuiDockNodeFlags_AutoHideTabBar | ImGuiDockNodeFlags_CentralNode | ImGuiDockNodeFlags_NoTabBar | ImGuiDockNodeFlags_HiddenTabBar | ImGuiDockNodeFlags_NoWindowMenuButton | ImGuiDockNodeFlags_NoCloseButton,
+    ImGuiDockNodeFlags_SavedFlagsMask_          = ImGuiDockNodeFlags_NoResizeFlagsMask_ | ImGuiDockNodeFlags_DockSpace | ImGuiDockNodeFlags_CentralNode | ImGuiDockNodeFlags_NoTabBar | ImGuiDockNodeFlags_HiddenTabBar | ImGuiDockNodeFlags_NoWindowMenuButton | ImGuiDockNodeFlags_NoCloseButton,
+};
+
+// Store the source authority (dock node vs window) of a field
+enum ImGuiDataAuthority_
+{
+    ImGuiDataAuthority_Auto,
+    ImGuiDataAuthority_DockNode,
+    ImGuiDataAuthority_Window,
+};
+
+enum ImGuiDockNodeState
+{
+    ImGuiDockNodeState_Unknown,
+    ImGuiDockNodeState_HostWindowHiddenBecauseSingleWindow,
+    ImGuiDockNodeState_HostWindowHiddenBecauseWindowsAreResizing,
+    ImGuiDockNodeState_HostWindowVisible,
+};
+
+// sizeof() 156~192
+struct IMGUI_API ImGuiDockNode
+{
+    ImGuiID                 ID;
+    ImGuiDockNodeFlags      SharedFlags;                // (Write) Flags shared by all nodes of a same dockspace hierarchy (inherited from the root node)
+    ImGuiDockNodeFlags      LocalFlags;                 // (Write) Flags specific to this node
+    ImGuiDockNodeFlags      LocalFlagsInWindows;        // (Write) Flags specific to this node, applied from windows
+    ImGuiDockNodeFlags      MergedFlags;                // (Read)  Effective flags (== SharedFlags | LocalFlagsInNode | LocalFlagsInWindows)
+    ImGuiDockNodeState      State;
+    ImGuiDockNode*          ParentNode;
+    ImGuiDockNode*          ChildNodes[2];              // [Split node only] Child nodes (left/right or top/bottom). Consider switching to an array.
+    ImVector<ImGuiWindow*>  Windows;                    // Note: unordered list! Iterate TabBar->Tabs for user-order.
+    ImGuiTabBar*            TabBar;
+    ImVec2                  Pos;                        // Current position
+    ImVec2                  Size;                       // Current size
+    ImVec2                  SizeRef;                    // [Split node only] Last explicitly written-to size (overridden when using a splitter affecting the node), used to calculate Size.
+    ImGuiAxis               SplitAxis;                  // [Split node only] Split axis (X or Y)
+    ImGuiWindowClass        WindowClass;                // [Root node only]
+    ImU32                   LastBgColor;
+
+    ImGuiWindow*            HostWindow;
+    ImGuiWindow*            VisibleWindow;              // Generally point to window which is ID is == SelectedTabID, but when CTRL+Tabbing this can be a different window.
+    ImGuiDockNode*          CentralNode;                // [Root node only] Pointer to central node.
+    ImGuiDockNode*          OnlyNodeWithWindows;        // [Root node only] Set when there is a single visible node within the hierarchy.
+    int                     CountNodeWithWindows;       // [Root node only]
+    int                     LastFrameAlive;             // Last frame number the node was updated or kept alive explicitly with DockSpace() + ImGuiDockNodeFlags_KeepAliveOnly
+    int                     LastFrameActive;            // Last frame number the node was updated.
+    int                     LastFrameFocused;           // Last frame number the node was focused.
+    ImGuiID                 LastFocusedNodeId;          // [Root node only] Which of our child docking node (any ancestor in the hierarchy) was last focused.
+    ImGuiID                 SelectedTabId;              // [Leaf node only] Which of our tab/window is selected.
+    ImGuiID                 WantCloseTabId;             // [Leaf node only] Set when closing a specific tab/window.
+    ImGuiID                 RefViewportId;              // Reference viewport ID from visible window when HostWindow == NULL.
+    ImGuiDataAuthority      AuthorityForPos         :3;
+    ImGuiDataAuthority      AuthorityForSize        :3;
+    ImGuiDataAuthority      AuthorityForViewport    :3;
+    bool                    IsVisible               :1; // Set to false when the node is hidden (usually disabled as it has no active window)
+    bool                    IsFocused               :1;
+    bool                    IsBgDrawnThisFrame      :1;
+    bool                    HasCloseButton          :1; // Provide space for a close button (if any of the docked window has one). Note that button may be hidden on window without one.
+    bool                    HasWindowMenuButton     :1;
+    bool                    HasCentralNodeChild     :1;
+    bool                    WantCloseAll            :1; // Set when closing all tabs at once.
+    bool                    WantLockSizeOnce        :1;
+    bool                    WantMouseMove           :1; // After a node extraction we need to transition toward moving the newly created host window
+    bool                    WantHiddenTabBarUpdate  :1;
+    bool                    WantHiddenTabBarToggle  :1;
+
+    ImGuiDockNode(ImGuiID id);
+    ~ImGuiDockNode();
+    bool                    IsRootNode() const      { return ParentNode == NULL; }
+    bool                    IsDockSpace() const     { return (MergedFlags & ImGuiDockNodeFlags_DockSpace) != 0; }
+    bool                    IsFloatingNode() const  { return ParentNode == NULL && (MergedFlags & ImGuiDockNodeFlags_DockSpace) == 0; }
+    bool                    IsCentralNode() const   { return (MergedFlags & ImGuiDockNodeFlags_CentralNode) != 0; }
+    bool                    IsHiddenTabBar() const  { return (MergedFlags & ImGuiDockNodeFlags_HiddenTabBar) != 0; } // Hidden tab bar can be shown back by clicking the small triangle
+    bool                    IsNoTabBar() const      { return (MergedFlags & ImGuiDockNodeFlags_NoTabBar) != 0; }     // Never show a tab bar
+    bool                    IsSplitNode() const     { return ChildNodes[0] != NULL; }
+    bool                    IsLeafNode() const      { return ChildNodes[0] == NULL; }
+    bool                    IsEmpty() const         { return ChildNodes[0] == NULL && Windows.Size == 0; }
+    ImRect                  Rect() const            { return ImRect(Pos.x, Pos.y, Pos.x + Size.x, Pos.y + Size.y); }
+
+    void                    SetLocalFlags(ImGuiDockNodeFlags flags) { LocalFlags = flags; UpdateMergedFlags(); }
+    void                    UpdateMergedFlags()     { MergedFlags = SharedFlags | LocalFlags | LocalFlagsInWindows; }
+};
+
+// List of colors that are stored at the time of Begin() into Docked Windows.
+// We currently store the packed colors in a simple array window->DockStyle.Colors[].
+// A better solution may involve appending into a log of colors in ImGuiContext + store offsets into those arrays in ImGuiWindow,
+// but it would be more complex as we'd need to double-buffer both as e.g. drop target may refer to window from last frame.
+enum ImGuiWindowDockStyleCol
+{
+    ImGuiWindowDockStyleCol_Text,
+    ImGuiWindowDockStyleCol_Tab,
+    ImGuiWindowDockStyleCol_TabHovered,
+    ImGuiWindowDockStyleCol_TabActive,
+    ImGuiWindowDockStyleCol_TabUnfocused,
+    ImGuiWindowDockStyleCol_TabUnfocusedActive,
+    ImGuiWindowDockStyleCol_COUNT
+};
+
+// We don't store style.Alpha: dock_node->LastBgColor embeds it and otherwise it would only affect the docking tab, which intuitively I would say we don't want to.
+struct ImGuiWindowDockStyle
+{
+    ImU32 Colors[ImGuiWindowDockStyleCol_COUNT];
+};
+
+struct ImGuiDockContext
+{
+    ImGuiStorage                    Nodes;          // Map ID -> ImGuiDockNode*: Active nodes
+    ImVector<ImGuiDockRequest>      Requests;
+    ImVector<ImGuiDockNodeSettings> NodesSettings;
+    bool                            WantFullRebuild;
+    ImGuiDockContext()              { memset(this, 0, sizeof(*this)); }
+};
+
 #endif // #ifdef IMGUI_HAS_DOCK
 
 //-----------------------------------------------------------------------------
@@ -1725,17 +1890,31 @@
 // Every instance of ImGuiViewport is in fact a ImGuiViewportP.
 struct ImGuiViewportP : public ImGuiViewport
 {
+    ImGuiWindow*        Window;                 // Set when the viewport is owned by a window (and ImGuiViewportFlags_CanHostOtherWindows is NOT set)
+    int                 Idx;
+    int                 LastFrameActive;        // Last frame number this viewport was activated by a window
+    int                 LastFocusedStampCount;  // Last stamp number from when a window hosted by this viewport was focused (by comparing this value between two viewport we have an implicit viewport z-order we use as fallback)
+    ImGuiID             LastNameHash;
+    ImVec2              LastPos;
+    float               Alpha;                  // Window opacity (when dragging dockable windows/viewports we make them transparent)
+    float               LastAlpha;
+    bool                LastFocusedHadNavWindow;// Instead of maintaining a LastFocusedWindow (which may harder to correctly maintain), we merely store weither NavWindow != NULL last time the viewport was focused.
+    short               PlatformMonitor;
     int                 BgFgDrawListsLastFrame[2]; // Last frame number the background (0) and foreground (1) draw lists were used
     ImDrawList*         BgFgDrawLists[2];       // Convenience background (0) and foreground (1) draw lists. We use them to draw software mouser cursor when io.MouseDrawCursor is set and to draw most debug overlays.
     ImDrawData          DrawDataP;
     ImDrawDataBuilder   DrawDataBuilder;        // Temporary data while building final ImDrawData
+    ImVec2              LastPlatformPos;
+    ImVec2              LastPlatformSize;
+    ImVec2              LastRendererSize;
     ImVec2              WorkOffsetMin;          // Work Area: Offset from Pos to top-left corner of Work Area. Generally (0,0) or (0,+main_menu_bar_height). Work Area is Full Area but without menu-bars/status-bars (so WorkArea always fit inside Pos/Size!)
     ImVec2              WorkOffsetMax;          // Work Area: Offset from Pos+Size to bottom-right corner of Work Area. Generally (0,0) or (0,-status_bar_height).
     ImVec2              BuildWorkOffsetMin;     // Work Area: Offset being built during current frame. Generally >= 0.0f.
     ImVec2              BuildWorkOffsetMax;     // Work Area: Offset being built during current frame. Generally <= 0.0f.
 
-    ImGuiViewportP()    { BgFgDrawListsLastFrame[0] = BgFgDrawListsLastFrame[1] = -1; BgFgDrawLists[0] = BgFgDrawLists[1] = NULL; }
-    ~ImGuiViewportP()   { if (BgFgDrawLists[0]) IM_DELETE(BgFgDrawLists[0]); if (BgFgDrawLists[1]) IM_DELETE(BgFgDrawLists[1]); }
+    ImGuiViewportP()                    { Window = NULL; Idx = -1; LastFrameActive = BgFgDrawListsLastFrame[0] = BgFgDrawListsLastFrame[1] = LastFocusedStampCount = -1; LastNameHash = 0; Alpha = LastAlpha = 1.0f; LastFocusedHadNavWindow = false; PlatformMonitor = -1; BgFgDrawLists[0] = BgFgDrawLists[1] = NULL; LastPlatformPos = LastPlatformSize = LastRendererSize = ImVec2(FLT_MAX, FLT_MAX); }
+    ~ImGuiViewportP()                   { if (BgFgDrawLists[0]) IM_DELETE(BgFgDrawLists[0]); if (BgFgDrawLists[1]) IM_DELETE(BgFgDrawLists[1]); }
+    void    ClearRequestFlags()         { PlatformRequestClose = PlatformRequestMove = PlatformRequestResize = false; }
 
     // Calculate work rect pos/size given a set of offset (we have 1 pair of offset for rect locked from last frame data, and 1 pair for currently building rect)
     ImVec2  CalcWorkRectPos(const ImVec2& off_min) const                            { return ImVec2(Pos.x + off_min.x, Pos.y + off_min.y); }
@@ -1758,14 +1937,19 @@
 struct ImGuiWindowSettings
 {
     ImGuiID     ID;
-    ImVec2ih    Pos;
+    ImVec2ih    Pos;            // NB: Settings position are stored RELATIVE to the viewport! Whereas runtime ones are absolute positions.
     ImVec2ih    Size;
+    ImVec2ih    ViewportPos;
+    ImGuiID     ViewportId;
+    ImGuiID     DockId;         // ID of last known DockNode (even if the DockNode is invisible because it has only 1 active window), or 0 if none.
+    ImGuiID     ClassId;        // ID of window class if specified
+    short       DockOrder;      // Order of the last time the window was visible within its DockNode. This is used to reorder windows that are reappearing on the same frame. Same value between windows that were active and windows that were none are possible.
     bool        Collapsed;
     bool        IsChild;
     bool        WantApply;      // Set when loaded from .ini data (to enable merging/loading .ini data into an already running context)
     bool        WantDelete;     // Set to invalidate/delete the settings entry
 
-    ImGuiWindowSettings()       { memset(this, 0, sizeof(*this)); }
+    ImGuiWindowSettings()       { memset(this, 0, sizeof(*this)); DockOrder = -1; }
     char* GetName()             { return (char*)(this + 1); }
 };
 
@@ -1799,6 +1983,9 @@
     ImGuiLocKey_WindowingMainMenuBar,
     ImGuiLocKey_WindowingPopup,
     ImGuiLocKey_WindowingUntitled,
+    ImGuiLocKey_DockingHideTabBar,
+    ImGuiLocKey_DockingHoldShiftToDock,
+    ImGuiLocKey_DockingDragToUndockOrMoveNode,
     ImGuiLocKey_COUNT
 };
 
@@ -1825,8 +2012,10 @@
     ImGuiDebugLogFlags_EventSelection       = 1 << 5,
     ImGuiDebugLogFlags_EventIO              = 1 << 6,
     ImGuiDebugLogFlags_EventInputRouting    = 1 << 7,
+    ImGuiDebugLogFlags_EventDocking         = 1 << 8,
+    ImGuiDebugLogFlags_EventViewport        = 1 << 9,
 
-    ImGuiDebugLogFlags_EventMask_           = ImGuiDebugLogFlags_EventActiveId  | ImGuiDebugLogFlags_EventFocus | ImGuiDebugLogFlags_EventPopup | ImGuiDebugLogFlags_EventNav | ImGuiDebugLogFlags_EventClipper | ImGuiDebugLogFlags_EventSelection | ImGuiDebugLogFlags_EventIO | ImGuiDebugLogFlags_EventInputRouting,
+    ImGuiDebugLogFlags_EventMask_           = ImGuiDebugLogFlags_EventActiveId  | ImGuiDebugLogFlags_EventFocus | ImGuiDebugLogFlags_EventPopup | ImGuiDebugLogFlags_EventNav | ImGuiDebugLogFlags_EventClipper | ImGuiDebugLogFlags_EventSelection | ImGuiDebugLogFlags_EventIO | ImGuiDebugLogFlags_EventInputRouting | ImGuiDebugLogFlags_EventDocking | ImGuiDebugLogFlags_EventViewport,
     ImGuiDebugLogFlags_OutputToTTY          = 1 << 20,  // Also send output to TTY
     ImGuiDebugLogFlags_OutputToTestEngine   = 1 << 21,  // Also send output to Test Engine
 };
@@ -1859,6 +2048,7 @@
     bool        ShowDrawCmdBoundingBoxes = true;
     bool        ShowTextEncodingViewer = false;
     bool        ShowAtlasTintedWithTextColor = false;
+    bool        ShowDockingNodes = false;
     int         ShowWindowsRectsType = -1;
     int         ShowTablesRectsType = -1;
     int         HighlightMonitorIdx = -1;
@@ -1916,15 +2106,19 @@
     bool                    Initialized;
     bool                    FontAtlasOwnedByContext;            // IO.Fonts-> is owned by the ImGuiContext and will be destructed along with it.
     ImGuiIO                 IO;
+    ImGuiPlatformIO         PlatformIO;
     ImGuiStyle              Style;
+    ImGuiConfigFlags        ConfigFlagsCurrFrame;               // = g.IO.ConfigFlags at the time of NewFrame()
+    ImGuiConfigFlags        ConfigFlagsLastFrame;
     ImFont*                 Font;                               // (Shortcut) == FontStack.empty() ? IO.Font : FontStack.back()
     float                   FontSize;                           // (Shortcut) == FontBaseSize * g.CurrentWindow->FontWindowScale == window->FontSize(). Text height for current window.
     float                   FontBaseSize;                       // (Shortcut) == IO.FontGlobalScale * Font->Scale * Font->FontSize. Base text height.
-    float                   CurrentDpiScale;                    // Current window/viewport DpiScale
+    float                   CurrentDpiScale;                    // Current window/viewport DpiScale == CurrentViewport->DpiScale
     ImDrawListSharedData    DrawListSharedData;
     double                  Time;
     int                     FrameCount;
     int                     FrameCountEnded;
+    int                     FrameCountPlatformEnded;
     int                     FrameCountRendered;
     bool                    WithinFrameScope;                   // Set by NewFrame(), cleared by EndFrame()
     bool                    WithinFrameScopeWithImplicitWindow; // Set by NewFrame(), cleared by EndFrame() when the implicit debug window has been pushed
@@ -1951,7 +2145,7 @@
     ImGuiWindow*            CurrentWindow;                      // Window being drawn into
     ImGuiWindow*            HoveredWindow;                      // Window the mouse is hovering. Will typically catch mouse inputs.
     ImGuiWindow*            HoveredWindowUnderMovingWindow;     // Hovered window ignoring MovingWindow. Only set if MovingWindow is set.
-    ImGuiWindow*            MovingWindow;                       // Track the window we clicked on (in order to preserve focus). The actual window that is moved is generally MovingWindow->RootWindow.
+    ImGuiWindow*            MovingWindow;                       // Track the window we clicked on (in order to preserve focus). The actual window that is moved is generally MovingWindow->RootWindowDockTree.
     ImGuiWindow*            WheelingWindow;                     // Track the window we started mouse-wheeling on. Until a timer elapse or mouse has moved, generally keep scrolling the same window even if during the course of scrolling the mouse ends up hovering a child window.
     ImVec2                  WheelingWindowRefMousePos;
     int                     WheelingWindowStartFrame;           // This may be set one frame before WheelingWindow is != NULL
@@ -2028,7 +2222,16 @@
     ImVector<ImGuiNavTreeNodeData>  NavTreeNodeStack;           // Stack for TreeNode() when a NavLeft requested is emitted.
 
     // Viewports
-    ImVector<ImGuiViewportP*> Viewports;                        // Active viewports (Size==1 in 'master' branch). Each viewports hold their copy of ImDrawData.
+    ImVector<ImGuiViewportP*> Viewports;                        // Active viewports (always 1+, and generally 1 unless multi-viewports are enabled). Each viewports hold their copy of ImDrawData.
+    ImGuiViewportP*         CurrentViewport;                    // We track changes of viewport (happening in Begin) so we can call Platform_OnChangedViewport()
+    ImGuiViewportP*         MouseViewport;
+    ImGuiViewportP*         MouseLastHoveredViewport;           // Last known viewport that was hovered by mouse (even if we are not hovering any viewport any more) + honoring the _NoInputs flag.
+    ImGuiID                 PlatformLastFocusedViewportId;
+    ImGuiPlatformMonitor    FallbackMonitor;                    // Virtual monitor used as fallback if backend doesn't provide monitor information.
+    ImRect                  PlatformMonitorsFullWorkRect;       // Bounding box of all platform monitors
+    int                     ViewportCreatedCount;               // Unique sequential creation counter (mostly for testing/debugging)
+    int                     PlatformWindowsCreatedCount;        // Unique sequential creation counter (mostly for testing/debugging)
+    int                     ViewportFocusedStampCount;          // Every time the front-most window changes, we stamp its viewport with an incrementing counter
 
     // Gamepad/keyboard Navigation
     ImGuiWindow*            NavWindow;                          // Focused window for navigation. Could be called 'FocusedWindow'
@@ -2181,6 +2384,12 @@
     // Platform support
     ImGuiPlatformImeData    PlatformImeData;                    // Data updated by current frame
     ImGuiPlatformImeData    PlatformImeDataPrev;                // Previous frame data (when changing we will call io.SetPlatformImeDataFn
+    ImGuiID                 PlatformImeViewport;
+
+    // Extensions
+    // FIXME: We could provide an API to register one slot in an array held in ImGuiContext?
+    ImGuiDockContext        DockContext;
+    void                    (*DockNodeWindowMenuHandler)(ImGuiContext* ctx, ImGuiDockNode* node, ImGuiTabBar* tab_bar);
 
     // Settings
     bool                    SettingsLoaded;
@@ -2227,6 +2436,7 @@
     ImGuiMetricsConfig      DebugMetricsConfig;
     ImGuiIDStackTool        DebugIDStackTool;
     ImGuiDebugAllocInfo     DebugAllocInfo;
+    ImGuiDockNode*          DebugHoveredDockNode;               // Hovered dock node.
 
     // Misc
     float                   FramerateSecPerFrame[60];           // Calculate estimate of framerate for user over the last 60 frames..
@@ -2245,13 +2455,14 @@
         InputTextState.Ctx = this;
 
         Initialized = false;
+        ConfigFlagsCurrFrame = ConfigFlagsLastFrame = ImGuiConfigFlags_None;
         FontAtlasOwnedByContext = shared_font_atlas ? false : true;
         Font = NULL;
         FontSize = FontBaseSize = CurrentDpiScale = 0.0f;
         IO.Fonts = shared_font_atlas ? shared_font_atlas : IM_NEW(ImFontAtlas)();
         Time = 0.0f;
         FrameCount = 0;
-        FrameCountEnded = FrameCountRendered = -1;
+        FrameCountEnded = FrameCountPlatformEnded = FrameCountRendered = -1;
         WithinFrameScope = WithinFrameScopeWithImplicitWindow = WithinEndChild = false;
         GcCompactAll = false;
         TestEngineHookItems = false;
@@ -2307,6 +2518,12 @@
         CurrentItemFlags = ImGuiItemFlags_None;
         DebugShowGroupRects = false;
 
+        CurrentViewport = NULL;
+        MouseViewport = MouseLastHoveredViewport = NULL;
+        PlatformLastFocusedViewportId = 0;
+        ViewportCreatedCount = PlatformWindowsCreatedCount = 0;
+        ViewportFocusedStampCount = 0;
+
         NavWindow = NULL;
         NavId = NavFocusScopeId = NavActivateId = NavActivateDownId = NavActivatePressedId = 0;
         NavJustMovedToId = NavJustMovedToFocusScopeId = NavNextActivateId = 0;
@@ -2391,6 +2608,9 @@
 
         PlatformImeData.InputPos = ImVec2(0.0f, 0.0f);
         PlatformImeDataPrev.InputPos = ImVec2(-1.0f, -1.0f); // Different to ensure initial submission
+        PlatformImeViewport = 0;
+
+        DockNodeWindowMenuHandler = NULL;
 
         SettingsLoaded = false;
         SettingsDirtyTimer = 0.0f;
@@ -2418,6 +2638,7 @@
         DebugItemPickerBreakId = 0;
         DebugFlashStyleColorTime = 0.0f;
         DebugFlashStyleColorIdx = ImGuiCol_COUNT;
+        DebugHoveredDockNode = NULL;
 
         // Same as DebugBreakClearData(). Those fields are scattered in their respective subsystem to stay in hot-data locations
         DebugBreakInWindow = 0;
@@ -2496,9 +2717,13 @@
     ImGuiContext*           Ctx;                                // Parent UI context (needs to be set explicitly by parent).
     char*                   Name;                               // Window name, owned by the window.
     ImGuiID                 ID;                                 // == ImHashStr(Name)
-    ImGuiWindowFlags        Flags;                              // See enum ImGuiWindowFlags_
+    ImGuiWindowFlags        Flags, FlagsPreviousFrame;          // See enum ImGuiWindowFlags_
     ImGuiChildFlags         ChildFlags;                         // Set when window is a child window. See enum ImGuiChildFlags_
+    ImGuiWindowClass        WindowClass;                        // Advanced users only. Set with SetNextWindowClass()
     ImGuiViewportP*         Viewport;                           // Always set in Begin(). Inactive windows may have a NULL value here if their viewport was discarded.
+    ImGuiID                 ViewportId;                         // We backup the viewport id (since the viewport may disappear or never be created if the window is inactive)
+    ImVec2                  ViewportPos;                        // We backup the viewport position (since the viewport may disappear or never be created if the window is inactive)
+    int                     ViewportAllowPlatformMonitorExtend; // Reset to -1 every frame (index is guaranteed to be valid between NewFrame..EndFrame), only used in the Appearing frame of a tooltip/popup to enforce clamping to a given monitor
     ImVec2                  Pos;                                // Position (always rounded-up to nearest pixel)
     ImVec2                  Size;                               // Current size (==SizeFull or collapsed title bar size)
     ImVec2                  SizeFull;                           // Size when non collapsed
@@ -2513,6 +2738,7 @@
     float                   DecoInnerSizeX1, DecoInnerSizeY1;   // Applied AFTER/OVER InnerRect. Specialized for Tables as they use specialized form of clipping and frozen rows/columns are inside InnerRect (and not part of regular decoration sizes).
     int                     NameBufLen;                         // Size of buffer storing Name. May be larger than strlen(Name)!
     ImGuiID                 MoveId;                             // == window->GetID("#MOVE")
+    ImGuiID                 TabId;                              // == window->GetID("#TAB")
     ImGuiID                 ChildId;                            // ID of corresponding item in parent window (for navigation to return from child window to parent window)
     ImVec2                  Scroll;
     ImVec2                  ScrollMax;
@@ -2521,6 +2747,7 @@
     ImVec2                  ScrollTargetEdgeSnapDist;           // 0.0f = no snapping, >0.0f snapping threshold
     ImVec2                  ScrollbarSizes;                     // Size taken by each scrollbars on their smaller axis. Pay attention! ScrollbarSizes.x == width of the vertical scrollbar, ScrollbarSizes.y = height of the horizontal scrollbar.
     bool                    ScrollbarX, ScrollbarY;             // Are scrollbars visible?
+    bool                    ViewportOwned;
     bool                    Active;                             // Set to true on Begin(), unless Collapsed
     bool                    WasActive;
     bool                    WriteAccessed;                      // Set to true when any widget access the current window
@@ -2551,6 +2778,7 @@
     ImGuiCond               SetWindowPosAllowFlags : 8;         // store acceptable condition flags for SetNextWindowPos() use.
     ImGuiCond               SetWindowSizeAllowFlags : 8;        // store acceptable condition flags for SetNextWindowSize() use.
     ImGuiCond               SetWindowCollapsedAllowFlags : 8;   // store acceptable condition flags for SetNextWindowCollapsed() use.
+    ImGuiCond               SetWindowDockAllowFlags : 8;        // store acceptable condition flags for SetNextWindowDock() use.
     ImVec2                  SetWindowPosVal;                    // store window position when using a non-zero Pivot (position set needs to be processed when we know the window size)
     ImVec2                  SetWindowPosPivot;                  // store window pivot for positioning. ImVec2(0, 0) when positioning from top-left corner; ImVec2(0.5f, 0.5f) for centering; ImVec2(1, 1) for bottom right.
 
@@ -2570,11 +2798,13 @@
     ImVec2ih                HitTestHoleOffset;
 
     int                     LastFrameActive;                    // Last frame number the window was Active.
+    int                     LastFrameJustFocused;               // Last frame number the window was made Focused.
     float                   LastTimeActive;                     // Last timestamp the window was Active (using float as we don't need high precision there)
     float                   ItemWidthDefault;
     ImGuiStorage            StateStorage;
     ImVector<ImGuiOldColumns> ColumnsStorage;
     float                   FontWindowScale;                    // User scale multiplier per-window, via SetWindowFontScale()
+    float                   FontDpiScale;
     int                     SettingsOffset;                     // Offset into SettingsWindows[] (offsets are always valid as we only grow the array from the back)
 
     ImDrawList*             DrawList;                           // == &DrawListInst (for backward compatibility reason with code using imgui_internal.h we keep this a pointer)
@@ -2583,6 +2813,7 @@
     ImGuiWindow*            ParentWindowInBeginStack;
     ImGuiWindow*            RootWindow;                         // Point to ourself or first ancestor that is not a child window. Doesn't cross through popups/dock nodes.
     ImGuiWindow*            RootWindowPopupTree;                // Point to ourself or first ancestor that is not a child window. Cross through popups parent<>child.
+    ImGuiWindow*            RootWindowDockTree;                 // Point to ourself or first ancestor that is not a child window. Cross through dock nodes.
     ImGuiWindow*            RootWindowForTitleBarHighlight;     // Point to ourself or first ancestor which will display TitleBgActive color when this window is active.
     ImGuiWindow*            RootWindowForNav;                   // Point to ourself or first ancestor which doesn't have the NavFlattened flag.
     ImGuiWindow*            ParentWindowForFocusRoute;          // Set to manual link a window to its logical parent so that Shortcut() chain are honoerd (e.g. Tool linked to Document)
@@ -2597,6 +2828,19 @@
     int                     MemoryDrawListVtxCapacity;
     bool                    MemoryCompacted;                    // Set when window extraneous data have been garbage collected
 
+    // Docking
+    bool                    DockIsActive        :1;             // When docking artifacts are actually visible. When this is set, DockNode is guaranteed to be != NULL. ~~ (DockNode != NULL) && (DockNode->Windows.Size > 1).
+    bool                    DockNodeIsVisible   :1;
+    bool                    DockTabIsVisible    :1;             // Is our window visible this frame? ~~ is the corresponding tab selected?
+    bool                    DockTabWantClose    :1;
+    short                   DockOrder;                          // Order of the last time the window was visible within its DockNode. This is used to reorder windows that are reappearing on the same frame. Same value between windows that were active and windows that were none are possible.
+    ImGuiWindowDockStyle    DockStyle;
+    ImGuiDockNode*          DockNode;                           // Which node are we docked into. Important: Prefer testing DockIsActive in many cases as this will still be set when the dock node is hidden.
+    ImGuiDockNode*          DockNodeAsHost;                     // Which node are we owning (for parent windows)
+    ImGuiID                 DockId;                             // Backup of last valid DockNode->ID, so single window remember their dock node id even when they are not bound any more
+    ImGuiItemStatusFlags    DockTabItemStatusFlags;
+    ImRect                  DockTabItemRect;
+
 public:
     ImGuiWindow(ImGuiContext* context, const char* name);
     ~ImGuiWindow();
@@ -2608,7 +2852,7 @@
 
     // We don't use g.FontSize because the window may be != g.CurrentWindow.
     ImRect      Rect() const            { return ImRect(Pos.x, Pos.y, Pos.x + Size.x, Pos.y + Size.y); }
-    float       CalcFontSize() const    { ImGuiContext& g = *Ctx; float scale = g.FontBaseSize * FontWindowScale; if (ParentWindow) scale *= ParentWindow->FontWindowScale; return scale; }
+    float       CalcFontSize() const    { ImGuiContext& g = *Ctx; float scale = g.FontBaseSize * FontWindowScale * FontDpiScale; if (ParentWindow) scale *= ParentWindow->FontWindowScale; return scale; }
     float       TitleBarHeight() const  { ImGuiContext& g = *Ctx; return (Flags & ImGuiWindowFlags_NoTitleBar) ? 0.0f : CalcFontSize() + g.Style.FramePadding.y * 2.0f; }
     ImRect      TitleBarRect() const    { return ImRect(Pos, ImVec2(Pos.x + SizeFull.x, Pos.y + TitleBarHeight())); }
     float       MenuBarHeight() const   { ImGuiContext& g = *Ctx; return (Flags & ImGuiWindowFlags_MenuBar) ? DC.MenuBarOffset.y + CalcFontSize() + g.Style.FramePadding.y * 2.0f : 0.0f; }
@@ -2633,13 +2877,15 @@
     ImGuiTabItemFlags_SectionMask_              = ImGuiTabItemFlags_Leading | ImGuiTabItemFlags_Trailing,
     ImGuiTabItemFlags_NoCloseButton             = 1 << 20,  // Track whether p_open was set or not (we'll need this info on the next frame to recompute ContentWidth during layout)
     ImGuiTabItemFlags_Button                    = 1 << 21,  // Used by TabItemButton, change the tab item behavior to mimic a button
+    ImGuiTabItemFlags_Unsorted                  = 1 << 22,  // [Docking] Trailing tabs with the _Unsorted flag will be sorted based on the DockOrder of their Window.
 };
 
-// Storage for one active tab item (sizeof() 40 bytes)
+// Storage for one active tab item (sizeof() 48 bytes)
 struct ImGuiTabItem
 {
     ImGuiID             ID;
     ImGuiTabItemFlags   Flags;
+    ImGuiWindow*        Window;                 // When TabItem is part of a DockNode's TabBar, we hold on to a window.
     int                 LastFrameVisible;
     int                 LastFrameSelected;      // This allows us to infer an ordered list of the last activated tabs with little maintenance
     float               Offset;                 // Position relative to beginning of tab
@@ -3003,7 +3249,7 @@
     IMGUI_API void          UpdateWindowParentAndRootLinks(ImGuiWindow* window, ImGuiWindowFlags flags, ImGuiWindow* parent_window);
     IMGUI_API void          UpdateWindowSkipRefresh(ImGuiWindow* window);
     IMGUI_API ImVec2        CalcWindowNextAutoFitSize(ImGuiWindow* window);
-    IMGUI_API bool          IsWindowChildOf(ImGuiWindow* window, ImGuiWindow* potential_parent, bool popup_hierarchy);
+    IMGUI_API bool          IsWindowChildOf(ImGuiWindow* window, ImGuiWindow* potential_parent, bool popup_hierarchy, bool dock_hierarchy);
     IMGUI_API bool          IsWindowWithinBeginStackOf(ImGuiWindow* window, ImGuiWindow* potential_parent);
     IMGUI_API bool          IsWindowAbove(ImGuiWindow* potential_above, ImGuiWindow* potential_below);
     IMGUI_API bool          IsWindowNavFocusable(ImGuiWindow* window);
@@ -3012,7 +3258,7 @@
     IMGUI_API void          SetWindowCollapsed(ImGuiWindow* window, bool collapsed, ImGuiCond cond = 0);
     IMGUI_API void          SetWindowHitTestHole(ImGuiWindow* window, const ImVec2& pos, const ImVec2& size);
     IMGUI_API void          SetWindowHiddenAndSkipItemsForCurrentFrame(ImGuiWindow* window);
-    inline void             SetWindowParentWindowForFocusRoute(ImGuiWindow* window, ImGuiWindow* parent_window) { window->ParentWindowForFocusRoute = parent_window; }
+    inline void             SetWindowParentWindowForFocusRoute(ImGuiWindow* window, ImGuiWindow* parent_window) { window->ParentWindowForFocusRoute = parent_window; } // You may also use SetNextWindowClass()'s FocusRouteParentWindowId field.
     inline ImRect           WindowRectAbsToRel(ImGuiWindow* window, const ImRect& r) { ImVec2 off = window->DC.CursorStartPos; return ImRect(r.Min.x - off.x, r.Min.y - off.y, r.Max.x - off.x, r.Max.y - off.y); }
     inline ImRect           WindowRectRelToAbs(ImGuiWindow* window, const ImRect& r) { ImVec2 off = window->DC.CursorStartPos; return ImRect(r.Min.x + off.x, r.Min.y + off.y, r.Max.x + off.x, r.Max.y + off.y); }
     inline ImVec2           WindowPosRelToAbs(ImGuiWindow* window, const ImVec2& p)  { ImVec2 off = window->DC.CursorStartPos; return ImVec2(p.x + off.x, p.y + off.y); }
@@ -3033,9 +3279,7 @@
     // Fonts, drawing
     IMGUI_API void          SetCurrentFont(ImFont* font);
     inline ImFont*          GetDefaultFont() { ImGuiContext& g = *GImGui; return g.IO.FontDefault ? g.IO.FontDefault : g.IO.Fonts->Fonts[0]; }
-    inline ImDrawList*      GetForegroundDrawList(ImGuiWindow* window) { IM_UNUSED(window); return GetForegroundDrawList(); } // This seemingly unnecessary wrapper simplifies compatibility between the 'master' and 'docking' branches.
-    IMGUI_API ImDrawList*   GetBackgroundDrawList(ImGuiViewport* viewport);                     // get background draw list for the given viewport. this draw list will be the first rendering one. Useful to quickly draw shapes/text behind dear imgui contents.
-    IMGUI_API ImDrawList*   GetForegroundDrawList(ImGuiViewport* viewport);                     // get foreground draw list for the given viewport. this draw list will be the last rendered one. Useful to quickly draw shapes/text over dear imgui contents.
+    inline ImDrawList*      GetForegroundDrawList(ImGuiWindow* window) { return GetForegroundDrawList(window->Viewport); }
     IMGUI_API void          AddDrawListToDrawDataEx(ImDrawData* draw_data, ImVector<ImDrawList*>* out_list, ImDrawList* draw_list);
 
     // Init
@@ -3047,6 +3291,7 @@
     IMGUI_API void          UpdateHoveredWindowAndCaptureFlags();
     IMGUI_API void          FindHoveredWindowEx(const ImVec2& pos, bool find_first_and_in_any_viewport, ImGuiWindow** out_hovered_window, ImGuiWindow** out_hovered_window_under_moving_window);
     IMGUI_API void          StartMouseMovingWindow(ImGuiWindow* window);
+    IMGUI_API void          StartMouseMovingWindowOrNode(ImGuiWindow* window, ImGuiDockNode* node, bool undock);
     IMGUI_API void          UpdateMouseMovingWindowNewFrame();
     IMGUI_API void          UpdateMouseMovingWindowEndFrame();
 
@@ -3056,7 +3301,13 @@
     IMGUI_API void          CallContextHooks(ImGuiContext* context, ImGuiContextHookType type);
 
     // Viewports
+    IMGUI_API void          TranslateWindowsInViewport(ImGuiViewportP* viewport, const ImVec2& old_pos, const ImVec2& new_pos);
+    IMGUI_API void          ScaleWindowsInViewport(ImGuiViewportP* viewport, float scale);
+    IMGUI_API void          DestroyPlatformWindow(ImGuiViewportP* viewport);
     IMGUI_API void          SetWindowViewport(ImGuiWindow* window, ImGuiViewportP* viewport);
+    IMGUI_API void          SetCurrentViewport(ImGuiWindow* window, ImGuiViewportP* viewport);
+    IMGUI_API const ImGuiPlatformMonitor*   GetViewportPlatformMonitor(ImGuiViewport* viewport);
+    IMGUI_API ImGuiViewportP*               FindHoveredViewportFromPlatformWindowStack(const ImVec2& mouse_platform_pos);
 
     // Settings
     IMGUI_API void                  MarkIniSettingsDirty();
@@ -3269,6 +3520,61 @@
     IMGUI_API bool          TestShortcutRouting(ImGuiKeyChord key_chord, ImGuiID owner_id);
     IMGUI_API ImGuiKeyRoutingData* GetShortcutRoutingData(ImGuiKeyChord key_chord);
 
+    // Docking
+    // (some functions are only declared in imgui.cpp, see Docking section)
+    IMGUI_API void          DockContextInitialize(ImGuiContext* ctx);
+    IMGUI_API void          DockContextShutdown(ImGuiContext* ctx);
+    IMGUI_API void          DockContextClearNodes(ImGuiContext* ctx, ImGuiID root_id, bool clear_settings_refs); // Use root_id==0 to clear all
+    IMGUI_API void          DockContextRebuildNodes(ImGuiContext* ctx);
+    IMGUI_API void          DockContextNewFrameUpdateUndocking(ImGuiContext* ctx);
+    IMGUI_API void          DockContextNewFrameUpdateDocking(ImGuiContext* ctx);
+    IMGUI_API void          DockContextEndFrame(ImGuiContext* ctx);
+    IMGUI_API ImGuiID       DockContextGenNodeID(ImGuiContext* ctx);
+    IMGUI_API void          DockContextQueueDock(ImGuiContext* ctx, ImGuiWindow* target, ImGuiDockNode* target_node, ImGuiWindow* payload, ImGuiDir split_dir, float split_ratio, bool split_outer);
+    IMGUI_API void          DockContextQueueUndockWindow(ImGuiContext* ctx, ImGuiWindow* window);
+    IMGUI_API void          DockContextQueueUndockNode(ImGuiContext* ctx, ImGuiDockNode* node);
+    IMGUI_API void          DockContextProcessUndockWindow(ImGuiContext* ctx, ImGuiWindow* window, bool clear_persistent_docking_ref = true);
+    IMGUI_API void          DockContextProcessUndockNode(ImGuiContext* ctx, ImGuiDockNode* node);
+    IMGUI_API bool          DockContextCalcDropPosForDocking(ImGuiWindow* target, ImGuiDockNode* target_node, ImGuiWindow* payload_window, ImGuiDockNode* payload_node, ImGuiDir split_dir, bool split_outer, ImVec2* out_pos);
+    IMGUI_API ImGuiDockNode*DockContextFindNodeByID(ImGuiContext* ctx, ImGuiID id);
+    IMGUI_API void          DockNodeWindowMenuHandler_Default(ImGuiContext* ctx, ImGuiDockNode* node, ImGuiTabBar* tab_bar);
+    IMGUI_API bool          DockNodeBeginAmendTabBar(ImGuiDockNode* node);
+    IMGUI_API void          DockNodeEndAmendTabBar();
+    inline ImGuiDockNode*   DockNodeGetRootNode(ImGuiDockNode* node)                 { while (node->ParentNode) node = node->ParentNode; return node; }
+    inline bool             DockNodeIsInHierarchyOf(ImGuiDockNode* node, ImGuiDockNode* parent) { while (node) { if (node == parent) return true; node = node->ParentNode; } return false; }
+    inline int              DockNodeGetDepth(const ImGuiDockNode* node)              { int depth = 0; while (node->ParentNode) { node = node->ParentNode; depth++; } return depth; }
+    inline ImGuiID          DockNodeGetWindowMenuButtonId(const ImGuiDockNode* node) { return ImHashStr("#COLLAPSE", 0, node->ID); }
+    inline ImGuiDockNode*   GetWindowDockNode()                                      { ImGuiContext& g = *GImGui; return g.CurrentWindow->DockNode; }
+    IMGUI_API bool          GetWindowAlwaysWantOwnTabBar(ImGuiWindow* window);
+    IMGUI_API void          BeginDocked(ImGuiWindow* window, bool* p_open);
+    IMGUI_API void          BeginDockableDragDropSource(ImGuiWindow* window);
+    IMGUI_API void          BeginDockableDragDropTarget(ImGuiWindow* window);
+    IMGUI_API void          SetWindowDock(ImGuiWindow* window, ImGuiID dock_id, ImGuiCond cond);
+
+    // Docking - Builder function needs to be generally called before the node is used/submitted.
+    // - The DockBuilderXXX functions are designed to _eventually_ become a public API, but it is too early to expose it and guarantee stability.
+    // - Do not hold on ImGuiDockNode* pointers! They may be invalidated by any split/merge/remove operation and every frame.
+    // - To create a DockSpace() node, make sure to set the ImGuiDockNodeFlags_DockSpace flag when calling DockBuilderAddNode().
+    //   You can create dockspace nodes (attached to a window) _or_ floating nodes (carry its own window) with this API.
+    // - DockBuilderSplitNode() create 2 child nodes within 1 node. The initial node becomes a parent node.
+    // - If you intend to split the node immediately after creation using DockBuilderSplitNode(), make sure
+    //   to call DockBuilderSetNodeSize() beforehand. If you don't, the resulting split sizes may not be reliable.
+    // - Call DockBuilderFinish() after you are done.
+    IMGUI_API void          DockBuilderDockWindow(const char* window_name, ImGuiID node_id);
+    IMGUI_API ImGuiDockNode*DockBuilderGetNode(ImGuiID node_id);
+    inline ImGuiDockNode*   DockBuilderGetCentralNode(ImGuiID node_id)              { ImGuiDockNode* node = DockBuilderGetNode(node_id); if (!node) return NULL; return DockNodeGetRootNode(node)->CentralNode; }
+    IMGUI_API ImGuiID       DockBuilderAddNode(ImGuiID node_id = 0, ImGuiDockNodeFlags flags = 0);
+    IMGUI_API void          DockBuilderRemoveNode(ImGuiID node_id);                 // Remove node and all its child, undock all windows
+    IMGUI_API void          DockBuilderRemoveNodeDockedWindows(ImGuiID node_id, bool clear_settings_refs = true);
+    IMGUI_API void          DockBuilderRemoveNodeChildNodes(ImGuiID node_id);       // Remove all split/hierarchy. All remaining docked windows will be re-docked to the remaining root node (node_id).
+    IMGUI_API void          DockBuilderSetNodePos(ImGuiID node_id, ImVec2 pos);
+    IMGUI_API void          DockBuilderSetNodeSize(ImGuiID node_id, ImVec2 size);
+    IMGUI_API ImGuiID       DockBuilderSplitNode(ImGuiID node_id, ImGuiDir split_dir, float size_ratio_for_node_at_dir, ImGuiID* out_id_at_dir, ImGuiID* out_id_at_opposite_dir); // Create 2 child nodes in this parent node.
+    IMGUI_API void          DockBuilderCopyDockSpace(ImGuiID src_dockspace_id, ImGuiID dst_dockspace_id, ImVector<const char*>* in_window_remap_pairs);
+    IMGUI_API void          DockBuilderCopyNode(ImGuiID src_node_id, ImGuiID dst_node_id, ImVector<ImGuiID>* out_node_remap_pairs);
+    IMGUI_API void          DockBuilderCopyWindowSettings(const char* src_name, const char* dst_name);
+    IMGUI_API void          DockBuilderFinish(ImGuiID node_id);
+
     // [EXPERIMENTAL] Focus Scope
     // This is generally used to identify a unique input location (for e.g. a selection set)
     // There is one per window (automatically set in Begin), but:
@@ -3368,9 +3674,11 @@
     IMGUI_API bool          BeginTabBarEx(ImGuiTabBar* tab_bar, const ImRect& bb, ImGuiTabBarFlags flags);
     IMGUI_API ImGuiTabItem* TabBarFindTabByID(ImGuiTabBar* tab_bar, ImGuiID tab_id);
     IMGUI_API ImGuiTabItem* TabBarFindTabByOrder(ImGuiTabBar* tab_bar, int order);
+    IMGUI_API ImGuiTabItem* TabBarFindMostRecentlySelectedTabForActiveWindow(ImGuiTabBar* tab_bar);
     IMGUI_API ImGuiTabItem* TabBarGetCurrentTab(ImGuiTabBar* tab_bar);
     inline int              TabBarGetTabOrder(ImGuiTabBar* tab_bar, ImGuiTabItem* tab) { return tab_bar->Tabs.index_from_ptr(tab); }
     IMGUI_API const char*   TabBarGetTabName(ImGuiTabBar* tab_bar, ImGuiTabItem* tab);
+    IMGUI_API void          TabBarAddTab(ImGuiTabBar* tab_bar, ImGuiTabItemFlags tab_flags, ImGuiWindow* window);
     IMGUI_API void          TabBarRemoveTab(ImGuiTabBar* tab_bar, ImGuiID tab_id);
     IMGUI_API void          TabBarCloseTab(ImGuiTabBar* tab_bar, ImGuiTabItem* tab);
     IMGUI_API void          TabBarQueueFocus(ImGuiTabBar* tab_bar, ImGuiTabItem* tab);
@@ -3403,8 +3711,10 @@
     IMGUI_API void          RenderBullet(ImDrawList* draw_list, ImVec2 pos, ImU32 col);
     IMGUI_API void          RenderCheckMark(ImDrawList* draw_list, ImVec2 pos, ImU32 col, float sz);
     IMGUI_API void          RenderArrowPointingAt(ImDrawList* draw_list, ImVec2 pos, ImVec2 half_sz, ImGuiDir direction, ImU32 col);
+    IMGUI_API void          RenderArrowDockMenu(ImDrawList* draw_list, ImVec2 p_min, float sz, ImU32 col);
     IMGUI_API void          RenderRectFilledRangeH(ImDrawList* draw_list, const ImRect& rect, ImU32 col, float x_start_norm, float x_end_norm, float rounding);
     IMGUI_API void          RenderRectFilledWithHole(ImDrawList* draw_list, const ImRect& outer, const ImRect& inner, ImU32 col, float rounding);
+    IMGUI_API ImDrawFlags   CalcRoundingFlagsForRectInRect(const ImRect& r_in, const ImRect& r_outer, float threshold);
 
     // Widgets
     IMGUI_API void          TextEx(const char* text, const char* text_end = NULL, ImGuiTextFlags flags = 0);
@@ -3418,7 +3728,7 @@
 
     // Widgets: Window Decorations
     IMGUI_API bool          CloseButton(ImGuiID id, const ImVec2& pos);
-    IMGUI_API bool          CollapseButton(ImGuiID id, const ImVec2& pos);
+    IMGUI_API bool          CollapseButton(ImGuiID id, const ImVec2& pos, ImGuiDockNode* dock_node);
     IMGUI_API void          Scrollbar(ImGuiAxis axis);
     IMGUI_API bool          ScrollbarEx(const ImRect& bb, ImGuiID id, ImGuiAxis axis, ImS64* p_scroll_v, ImS64 avail_v, ImS64 contents_v, ImDrawFlags flags);
     IMGUI_API ImRect        GetWindowScrollbarRect(ImGuiWindow* window, ImGuiAxis axis);
@@ -3502,6 +3812,7 @@
     IMGUI_API void          ShowFontAtlas(ImFontAtlas* atlas);
     IMGUI_API void          DebugHookIdInfo(ImGuiID id, ImGuiDataType data_type, const void* data_id, const void* data_id_end);
     IMGUI_API void          DebugNodeColumns(ImGuiOldColumns* columns);
+    IMGUI_API void          DebugNodeDockNode(ImGuiDockNode* node, const char* label);
     IMGUI_API void          DebugNodeDrawList(ImGuiWindow* window, ImGuiViewportP* viewport, const ImDrawList* draw_list, const char* label);
     IMGUI_API void          DebugNodeDrawCmdShowMeshAndBoundingBox(ImDrawList* out_draw_list, const ImDrawList* draw_list, const ImDrawCmd* draw_cmd, bool show_mesh, bool show_aabb);
     IMGUI_API void          DebugNodeFont(ImFont* font);
diff --git a/imgui_widgets.cpp b/imgui_widgets.cpp
index 2e78012..45604e0 100644
--- a/imgui_widgets.cpp
+++ b/imgui_widgets.cpp
@@ -503,7 +503,7 @@
         item_flags |= ImGuiItemFlags_ButtonRepeat;
 
     ImGuiWindow* backup_hovered_window = g.HoveredWindow;
-    const bool flatten_hovered_children = (flags & ImGuiButtonFlags_FlattenChildren) && g.HoveredWindow && g.HoveredWindow->RootWindow == window;
+    const bool flatten_hovered_children = (flags & ImGuiButtonFlags_FlattenChildren) && g.HoveredWindow && g.HoveredWindow->RootWindowDockTree == window->RootWindowDockTree;
     if (flatten_hovered_children)
         g.HoveredWindow = window;
 
@@ -849,7 +849,8 @@
     return pressed;
 }
 
-bool ImGui::CollapseButton(ImGuiID id, const ImVec2& pos)
+// The Collapse button also functions as a Dock Menu button.
+bool ImGui::CollapseButton(ImGuiID id, const ImVec2& pos, ImGuiDockNode* dock_node)
 {
     ImGuiContext& g = *GImGui;
     ImGuiWindow* window = g.CurrentWindow;
@@ -862,15 +863,20 @@
         return pressed;
 
     // Render
+    //bool is_dock_menu = (window->DockNodeAsHost && !window->Collapsed);
     ImU32 bg_col = GetColorU32((held && hovered) ? ImGuiCol_ButtonActive : hovered ? ImGuiCol_ButtonHovered : ImGuiCol_Button);
     ImU32 text_col = GetColorU32(ImGuiCol_Text);
     if (hovered || held)
         window->DrawList->AddCircleFilled(bb.GetCenter() + ImVec2(0.0f, -0.5f), g.FontSize * 0.5f + 1.0f, bg_col);
-    RenderArrow(window->DrawList, bb.Min, text_col, window->Collapsed ? ImGuiDir_Right : ImGuiDir_Down, 1.0f);
+
+    if (dock_node)
+        RenderArrowDockMenu(window->DrawList, bb.Min, g.FontSize, text_col);
+    else
+        RenderArrow(window->DrawList, bb.Min, text_col, window->Collapsed ? ImGuiDir_Right : ImGuiDir_Down, 1.0f);
 
     // Switch to moving the window after mouse is moved beyond the initial drag threshold
     if (IsItemActive() && IsMouseDragging(0))
-        StartMouseMovingWindow(window);
+        StartMouseMovingWindowOrNode(window, dock_node, true); // Undock from window/collapse menu button
 
     return pressed;
 }
@@ -1515,7 +1521,7 @@
     const float separator_thickness = style.SeparatorTextBorderSize;
     const ImVec2 min_size(label_size.x + extra_w + padding.x * 2.0f, ImMax(label_size.y + padding.y * 2.0f, separator_thickness));
     const ImRect bb(pos, ImVec2(window->WorkRect.Max.x, pos.y + min_size.y));
-    const float text_baseline_y = ImTrunc((bb.GetHeight() - label_size.y) * style.SeparatorTextAlign.y + 0.99999f); //ImMax(padding.y, ImFloor((style.SeparatorTextSize - label_size.y) * 0.5f));
+    const float text_baseline_y = ImTrunc((bb.GetHeight() - label_size.y) * style.SeparatorTextAlign.y + 0.99999f); //ImMax(padding.y, ImTrunc((style.SeparatorTextSize - label_size.y) * 0.5f));
     ItemSize(min_size, text_baseline_y);
     if (!ItemAdd(bb, id))
         return;
@@ -5018,6 +5024,7 @@
                 g.PlatformImeData.WantVisible = true;
                 g.PlatformImeData.InputPos = ImVec2(cursor_screen_pos.x - 1.0f, cursor_screen_pos.y - g.FontSize);
                 g.PlatformImeData.InputLineHeight = g.FontSize;
+                g.PlatformImeViewport = window->Viewport->ID;
             }
         }
     }
@@ -7304,7 +7311,7 @@
     // We don't clip with current window clipping rectangle as it is already set to the area below. However we clip with window full rect.
     // We remove 1 worth of rounding to Max.x to that text in long menus and small windows don't tend to display over the lower-right rounded area, which looks particularly glitchy.
     ImRect bar_rect = window->MenuBarRect();
-    ImRect clip_rect(IM_ROUND(bar_rect.Min.x + window->WindowBorderSize), IM_ROUND(bar_rect.Min.y + window->WindowBorderSize), IM_ROUND(ImMax(bar_rect.Min.x, bar_rect.Max.x - ImMax(window->WindowRounding, window->WindowBorderSize))), IM_ROUND(bar_rect.Max.y));
+    ImRect clip_rect(ImFloor(bar_rect.Min.x + window->WindowBorderSize), ImFloor(bar_rect.Min.y + window->WindowBorderSize), ImFloor(ImMax(bar_rect.Min.x, bar_rect.Max.x - ImMax(window->WindowRounding, window->WindowBorderSize))), ImFloor(bar_rect.Max.y));
     clip_rect.ClipWith(window->OuterRectClipped);
     PushClipRect(clip_rect.Min, clip_rect.Max, false);
 
@@ -7374,10 +7381,10 @@
     IM_ASSERT(dir != ImGuiDir_None);
 
     ImGuiWindow* bar_window = FindWindowByName(name);
+    ImGuiViewportP* viewport = (ImGuiViewportP*)(void*)(viewport_p ? viewport_p : GetMainViewport());
     if (bar_window == NULL || bar_window->BeginCount == 0)
     {
         // Calculate and set window size/position
-        ImGuiViewportP* viewport = (ImGuiViewportP*)(void*)(viewport_p ? viewport_p : GetMainViewport());
         ImRect avail_rect = viewport->GetBuildWorkRect();
         ImGuiAxis axis = (dir == ImGuiDir_Up || dir == ImGuiDir_Down) ? ImGuiAxis_Y : ImGuiAxis_X;
         ImVec2 pos = avail_rect.Min;
@@ -7395,7 +7402,8 @@
             viewport->BuildWorkOffsetMax[axis] -= axis_size;
     }
 
-    window_flags |= ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove;
+    window_flags |= ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoDocking;
+    SetNextWindowViewport(viewport->ID); // Enforce viewport so we don't create our own viewport when ImGuiConfigFlags_ViewportsNoMerge is set.
     PushStyleVar(ImGuiStyleVar_WindowRounding, 0.0f);
     PushStyleVar(ImGuiStyleVar_WindowMinSize, ImVec2(0, 0)); // Lift normal size constraint
     bool is_open = Begin(name, NULL, window_flags);
@@ -7409,6 +7417,9 @@
     ImGuiContext& g = *GImGui;
     ImGuiViewportP* viewport = (ImGuiViewportP*)(void*)GetMainViewport();
 
+    // Notify of viewport change so GetFrameHeight() can be accurate in case of DPI change
+    SetCurrentViewport(NULL, viewport);
+
     // For the main menu bar, which cannot be moved, we honor g.Style.DisplaySafeAreaPadding to ensure text can be visible on a TV set.
     // FIXME: This could be generalized as an opt-in way to clamp window->DC.CursorStartPos to avoid SafeArea?
     // FIXME: Consider removing support for safe area down the line... it's messy. Nowadays consoles have support for TV calibration in OS settings.
@@ -7459,7 +7470,7 @@
     const ImGuiPopupData* upper_popup = &g.OpenPopupStack[g.BeginPopupStack.Size];
     if (window->DC.NavLayerCurrent != upper_popup->ParentNavLayer)
         return false;
-    return upper_popup->Window && (upper_popup->Window->Flags & ImGuiWindowFlags_ChildMenu) && ImGui::IsWindowChildOf(upper_popup->Window, window, true);
+    return upper_popup->Window && (upper_popup->Window->Flags & ImGuiWindowFlags_ChildMenu) && ImGui::IsWindowChildOf(upper_popup->Window, window, true, false);
 }
 
 bool ImGui::BeginMenuEx(const char* label, const char* icon, bool enabled)
@@ -7798,8 +7809,10 @@
 // - TabBarCalcMaxTabWidth() [Internal]
 // - TabBarFindTabById() [Internal]
 // - TabBarFindTabByOrder() [Internal]
+// - TabBarFindMostRecentlySelectedTabForActiveWindow() [Internal]
 // - TabBarGetCurrentTab() [Internal]
 // - TabBarGetTabName() [Internal]
+// - TabBarAddTab() [Internal]
 // - TabBarRemoveTab() [Internal]
 // - TabBarCloseTab() [Internal]
 // - TabBarScrollClamp() [Internal]
@@ -7918,7 +7931,8 @@
 
     // Ensure correct ordering when toggling ImGuiTabBarFlags_Reorderable flag, or when a new tab was added while being not reorderable
     if ((flags & ImGuiTabBarFlags_Reorderable) != (tab_bar->Flags & ImGuiTabBarFlags_Reorderable) || (tab_bar->TabsAddedNew && !(flags & ImGuiTabBarFlags_Reorderable)))
-        ImQsort(tab_bar->Tabs.Data, tab_bar->Tabs.Size, sizeof(ImGuiTabItem), TabItemComparerByBeginOrder);
+        if ((flags & ImGuiTabBarFlags_DockNode) == 0) // FIXME: TabBar with DockNode can now be hybrid
+            ImQsort(tab_bar->Tabs.Data, tab_bar->Tabs.Size, sizeof(ImGuiTabItem), TabItemComparerByBeginOrder);
     tab_bar->TabsAddedNew = false;
 
     // Flags
@@ -8200,6 +8214,10 @@
     tab_bar->VisibleTabId = tab_bar->SelectedTabId;
     tab_bar->VisibleTabWasSubmitted = false;
 
+    // CTRL+TAB can override visible tab temporarily
+    if (g.NavWindowingTarget != NULL && g.NavWindowingTarget->DockNode && g.NavWindowingTarget->DockNode->TabBar == tab_bar)
+        tab_bar->VisibleTabId = scroll_to_tab_id = g.NavWindowingTarget->TabId;
+
     // Apply request requests
     if (scroll_to_tab_id != 0)
         TabBarScrollToTab(tab_bar, scroll_to_tab_id, sections);
@@ -8245,11 +8263,11 @@
 // Dockable windows uses Name/ID in the global namespace. Non-dockable items use the ID stack.
 static ImU32   ImGui::TabBarCalcTabID(ImGuiTabBar* tab_bar, const char* label, ImGuiWindow* docked_window)
 {
-    IM_ASSERT(docked_window == NULL); // master branch only
-    IM_UNUSED(docked_window);
-    if (tab_bar->Flags & ImGuiTabBarFlags_DockNode)
+    if (docked_window != NULL)
     {
-        ImGuiID id = ImHashStr(label);
+        IM_UNUSED(tab_bar);
+        IM_ASSERT(tab_bar->Flags & ImGuiTabBarFlags_DockNode);
+        ImGuiID id = docked_window->TabId;
         KeepAliveID(id);
         return id;
     }
@@ -8283,6 +8301,20 @@
     return &tab_bar->Tabs[order];
 }
 
+// FIXME: See references to #2304 in TODO.txt
+ImGuiTabItem* ImGui::TabBarFindMostRecentlySelectedTabForActiveWindow(ImGuiTabBar* tab_bar)
+{
+    ImGuiTabItem* most_recently_selected_tab = NULL;
+    for (int tab_n = 0; tab_n < tab_bar->Tabs.Size; tab_n++)
+    {
+        ImGuiTabItem* tab = &tab_bar->Tabs[tab_n];
+        if (most_recently_selected_tab == NULL || most_recently_selected_tab->LastFrameSelected < tab->LastFrameSelected)
+            if (tab->Window && tab->Window->WasActive)
+                most_recently_selected_tab = tab;
+    }
+    return most_recently_selected_tab;
+}
+
 ImGuiTabItem* ImGui::TabBarGetCurrentTab(ImGuiTabBar* tab_bar)
 {
     if (tab_bar->LastTabItemIdx <= 0 || tab_bar->LastTabItemIdx >= tab_bar->Tabs.Size)
@@ -8292,12 +8324,35 @@
 
 const char* ImGui::TabBarGetTabName(ImGuiTabBar* tab_bar, ImGuiTabItem* tab)
 {
+    if (tab->Window)
+        return tab->Window->Name;
     if (tab->NameOffset == -1)
         return "N/A";
     IM_ASSERT(tab->NameOffset < tab_bar->TabsNames.Buf.Size);
     return tab_bar->TabsNames.Buf.Data + tab->NameOffset;
 }
 
+// The purpose of this call is to register tab in advance so we can control their order at the time they appear.
+// Otherwise calling this is unnecessary as tabs are appending as needed by the BeginTabItem() function.
+void ImGui::TabBarAddTab(ImGuiTabBar* tab_bar, ImGuiTabItemFlags tab_flags, ImGuiWindow* window)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(TabBarFindTabByID(tab_bar, window->TabId) == NULL);
+    IM_ASSERT(g.CurrentTabBar != tab_bar);  // Can't work while the tab bar is active as our tab doesn't have an X offset yet, in theory we could/should test something like (tab_bar->CurrFrameVisible < g.FrameCount) but we'd need to solve why triggers the commented early-out assert in BeginTabBarEx() (probably dock node going from implicit to explicit in same frame)
+
+    if (!window->HasCloseButton)
+        tab_flags |= ImGuiTabItemFlags_NoCloseButton;       // Set _NoCloseButton immediately because it will be used for first-frame width calculation.
+
+    ImGuiTabItem new_tab;
+    new_tab.ID = window->TabId;
+    new_tab.Flags = tab_flags;
+    new_tab.LastFrameVisible = tab_bar->CurrFrameVisible;   // Required so BeginTabBar() doesn't ditch the tab
+    if (new_tab.LastFrameVisible == -1)
+        new_tab.LastFrameVisible = g.FrameCount - 1;
+    new_tab.Window = window;                                // Required so tab bar layout can compute the tab width before tab submission
+    tab_bar->Tabs.push_back(new_tab);
+}
+
 // The *TabId fields are already set by the docking system _before_ the actual TabItem was created, so we clear them regardless.
 void ImGui::TabBarRemoveTab(ImGuiTabBar* tab_bar, ImGuiID tab_id)
 {
@@ -8578,7 +8633,7 @@
         IM_ASSERT_USER_ERROR(tab_bar, "Needs to be called between BeginTabBar() and EndTabBar()!");
         return false;
     }
-    IM_ASSERT(!(flags & ImGuiTabItemFlags_Button)); // BeginTabItem() Can't be used with button flags, use TabItemButton() instead!
+    IM_ASSERT((flags & ImGuiTabItemFlags_Button) == 0);             // BeginTabItem() Can't be used with button flags, use TabItemButton() instead!
 
     bool ret = TabItemEx(tab_bar, label, p_open, flags, NULL);
     if (ret && !(flags & ImGuiTabItemFlags_NoPushId))
@@ -8688,11 +8743,14 @@
     const bool is_tab_button = (flags & ImGuiTabItemFlags_Button) != 0;
     tab->LastFrameVisible = g.FrameCount;
     tab->Flags = flags;
+    tab->Window = docked_window;
 
     // Append name _WITH_ the zero-terminator
+    // (regular tabs are permitted in a DockNode tab bar, but window tabs not permitted in a non-DockNode tab bar)
     if (docked_window != NULL)
     {
-        IM_ASSERT(docked_window == NULL); // master branch only
+        IM_ASSERT(tab_bar->Flags & ImGuiTabBarFlags_DockNode);
+        tab->NameOffset = -1;
     }
     else
     {
@@ -8717,7 +8775,7 @@
         tab_bar->VisibleTabWasSubmitted = true;
 
     // On the very first frame of a tab bar we let first tab contents be visible to minimize appearing glitches
-    if (!tab_contents_visible && tab_bar->SelectedTabId == 0 && tab_bar_appearing)
+    if (!tab_contents_visible && tab_bar->SelectedTabId == 0 && tab_bar_appearing && docked_window == NULL)
         if (tab_bar->Tabs.Size == 1 && !(tab_bar->Flags & ImGuiTabBarFlags_AutoSelectNewTabs))
             tab_contents_visible = true;
 
@@ -8765,30 +8823,82 @@
     }
 
     // Click to Select a tab
-    // Allow the close button to overlap
     ImGuiButtonFlags button_flags = ((is_tab_button ? ImGuiButtonFlags_PressedOnClickRelease : ImGuiButtonFlags_PressedOnClick) | ImGuiButtonFlags_AllowOverlap);
-    if (g.DragDropActive)
+    if (g.DragDropActive && !g.DragDropPayload.IsDataType(IMGUI_PAYLOAD_TYPE_WINDOW)) // FIXME: May be an opt-in property of the payload to disable this
         button_flags |= ImGuiButtonFlags_PressedOnDragDropHold;
     bool hovered, held;
     bool pressed = ButtonBehavior(bb, id, &hovered, &held, button_flags);
     if (pressed && !is_tab_button)
         TabBarQueueFocus(tab_bar, tab);
 
-    // Drag and drop: re-order tabs
-    if (held && !tab_appearing && IsMouseDragging(0))
+    // Transfer active id window so the active id is not owned by the dock host (as StartMouseMovingWindow()
+    // will only do it on the drag). This allows FocusWindow() to be more conservative in how it clears active id.
+    if (held && docked_window && g.ActiveId == id && g.ActiveIdIsJustActivated)
+        g.ActiveIdWindow = docked_window;
+
+    // Drag and drop a single floating window node moves it
+    ImGuiDockNode* node = docked_window ? docked_window->DockNode : NULL;
+    const bool single_floating_window_node = node && node->IsFloatingNode() && (node->Windows.Size == 1);
+    if (held && single_floating_window_node && IsMouseDragging(0, 0.0f))
     {
-        if (!g.DragDropActive && (tab_bar->Flags & ImGuiTabBarFlags_Reorderable))
+        // Move
+        StartMouseMovingWindow(docked_window);
+    }
+    else if (held && !tab_appearing && IsMouseDragging(0))
+    {
+        // Drag and drop: re-order tabs
+        int drag_dir = 0;
+        float drag_distance_from_edge_x = 0.0f;
+        if (!g.DragDropActive && ((tab_bar->Flags & ImGuiTabBarFlags_Reorderable) || (docked_window != NULL)))
         {
             // While moving a tab it will jump on the other side of the mouse, so we also test for MouseDelta.x
             if (g.IO.MouseDelta.x < 0.0f && g.IO.MousePos.x < bb.Min.x)
             {
+                drag_dir = -1;
+                drag_distance_from_edge_x = bb.Min.x - g.IO.MousePos.x;
                 TabBarQueueReorderFromMousePos(tab_bar, tab, g.IO.MousePos);
             }
             else if (g.IO.MouseDelta.x > 0.0f && g.IO.MousePos.x > bb.Max.x)
             {
+                drag_dir = +1;
+                drag_distance_from_edge_x = g.IO.MousePos.x - bb.Max.x;
                 TabBarQueueReorderFromMousePos(tab_bar, tab, g.IO.MousePos);
             }
         }
+
+        // Extract a Dockable window out of it's tab bar
+        const bool can_undock = docked_window != NULL && !(docked_window->Flags & ImGuiWindowFlags_NoMove) && !(node->MergedFlags & ImGuiDockNodeFlags_NoUndocking);
+        if (can_undock)
+        {
+            // We use a variable threshold to distinguish dragging tabs within a tab bar and extracting them out of the tab bar
+            bool undocking_tab = (g.DragDropActive && g.DragDropPayload.SourceId == id);
+            if (!undocking_tab) //&& (!g.IO.ConfigDockingWithShift || g.IO.KeyShift)
+            {
+                float threshold_base = g.FontSize;
+                float threshold_x = (threshold_base * 2.2f);
+                float threshold_y = (threshold_base * 1.5f) + ImClamp((ImFabs(g.IO.MouseDragMaxDistanceAbs[0].x) - threshold_base * 2.0f) * 0.20f, 0.0f, threshold_base * 4.0f);
+                //GetForegroundDrawList()->AddRect(ImVec2(bb.Min.x - threshold_x, bb.Min.y - threshold_y), ImVec2(bb.Max.x + threshold_x, bb.Max.y + threshold_y), IM_COL32_WHITE); // [DEBUG]
+
+                float distance_from_edge_y = ImMax(bb.Min.y - g.IO.MousePos.y, g.IO.MousePos.y - bb.Max.y);
+                if (distance_from_edge_y >= threshold_y)
+                    undocking_tab = true;
+                if (drag_distance_from_edge_x > threshold_x)
+                    if ((drag_dir < 0 && TabBarGetTabOrder(tab_bar, tab) == 0) || (drag_dir > 0 && TabBarGetTabOrder(tab_bar, tab) == tab_bar->Tabs.Size - 1))
+                        undocking_tab = true;
+            }
+
+            if (undocking_tab)
+            {
+                // Undock
+                // FIXME: refactor to share more code with e.g. StartMouseMovingWindow
+                DockContextQueueUndockWindow(&g, docked_window);
+                g.MovingWindow = docked_window;
+                SetActiveID(g.MovingWindow->MoveId, g.MovingWindow);
+                g.ActiveIdClickOffset -= g.MovingWindow->Pos - bb.Min;
+                g.ActiveIdNoClearOnFocusLoss = true;
+                SetActiveIdUsingAllKeyboardKeys();
+            }
+        }
     }
 
 #if 0
@@ -8816,7 +8926,7 @@
         flags |= ImGuiTabItemFlags_NoCloseWithMiddleMouseButton;
 
     // Render tab label, process close button
-    const ImGuiID close_button_id = p_open ? GetIDWithSeed("#CLOSE", NULL, id) : 0;
+    const ImGuiID close_button_id = p_open ? GetIDWithSeed("#CLOSE", NULL, docked_window ? docked_window->ID : id) : 0;
     bool just_closed;
     bool text_clipped;
     TabItemLabelAndCloseButton(display_draw_list, bb, tab_just_unsaved ? (flags & ~ImGuiTabItemFlags_UnsavedDocument) : flags, tab_bar->FramePadding, label, id, close_button_id, tab_contents_visible, &just_closed, &text_clipped);
@@ -8826,6 +8936,11 @@
         TabBarCloseTab(tab_bar, tab);
     }
 
+    // Forward Hovered state so IsItemHovered() after Begin() can work (even though we are technically hovering our parent)
+    // That state is copied to window->DockTabItemStatusFlags by our caller.
+    if (docked_window && (hovered || g.HoveredId == close_button_id))
+        g.LastItemData.StatusFlags |= ImGuiItemStatusFlags_HoveredWindow;
+
     // Restore main window position so user can draw there
     if (want_clip_rect)
         PopClipRect();
@@ -8860,6 +8975,16 @@
         if (ImGuiTabItem* tab = TabBarFindTabByID(tab_bar, tab_id))
             tab->WantClose = true; // Will be processed by next call to TabBarLayout()
     }
+    else if (ImGuiWindow* window = FindWindowByName(label))
+    {
+        if (window->DockIsActive)
+            if (ImGuiDockNode* node = window->DockNode)
+            {
+                ImGuiID tab_id = TabBarCalcTabID(node->TabBar, label, window);
+                TabBarRemoveTab(node->TabBar, tab_id);
+                window->DockTabWantClose = true;
+            }
+    }
 }
 
 ImVec2 ImGui::TabItemCalcSize(const char* label, bool has_close_button_or_unsaved_marker)
@@ -8874,10 +8999,9 @@
     return ImVec2(ImMin(size.x, TabBarCalcMaxTabWidth()), size.y);
 }
 
-ImVec2 ImGui::TabItemCalcSize(ImGuiWindow*)
+ImVec2 ImGui::TabItemCalcSize(ImGuiWindow* window)
 {
-    IM_ASSERT(0); // This function exists to facilitate merge with 'docking' branch.
-    return ImVec2(0.0f, 0.0f);
+    return TabItemCalcSize(window->Name, window->HasCloseButton || (window->Flags & ImGuiWindowFlags_UnsavedDocument));
 }
 
 void ImGui::TabItemBackground(ImDrawList* draw_list, const ImRect& bb, ImGuiTabItemFlags flags, ImU32 col)
diff --git a/misc/debuggers/imgui.natvis b/misc/debuggers/imgui.natvis
index 13b6360..94d17a8 100644
--- a/misc/debuggers/imgui.natvis
+++ b/misc/debuggers/imgui.natvis
@@ -55,4 +55,8 @@
   <DisplayString>{{Name {Name,s} Active {(Active||WasActive)?1:0,d} Child {(Flags &amp; 0x01000000)?1:0,d} Popup {(Flags &amp; 0x04000000)?1:0,d} Hidden {(Hidden)?1:0,d}}</DisplayString>
 </Type>
 
+<Type Name="ImGuiDockNode">
+  <DisplayString>{{ID {ID,x} Pos=({Pos.x,g} {Pos.y,g}) Size=({Size.x,g} {Size.y,g}) Parent {(ParentNode==0)?0:ParentNode->ID,x} Childs {(ChildNodes[0] != 0)+(ChildNodes[1] != 0)} Windows {Windows.Size}  }</DisplayString>
+</Type>
+
 </AutoVisualizer>