Backends: Win32: Added ImGui_ImplWin32_EnableAlphaCompositing() helper. (#2766, #3447)
Pragma linking with dwmapi.lib (Vista-era, ~9 kb). MinGW users will need to link with -ldwmapi.
diff --git a/backends/imgui_impl_win32.cpp b/backends/imgui_impl_win32.cpp
index 64454dd..df5f502 100644
--- a/backends/imgui_impl_win32.cpp
+++ b/backends/imgui_impl_win32.cpp
@@ -18,6 +18,10 @@
#endif
#include <windows.h>
#include <tchar.h>
+#include <dwmapi.h>
+
+// Configuration flags to add in your imconfig.h file:
+//#define IMGUI_IMPL_WIN32_DISABLE_GAMEPAD // Disable gamepad support (this used to be meaningful before <1.81) but we know load XInput dynamically so the option is less relevant now.
// Using XInput for gamepad (will load DLL dynamically)
#ifndef IMGUI_IMPL_WIN32_DISABLE_GAMEPAD
@@ -28,6 +32,7 @@
// CHANGELOG
// (minor and older changes stripped away, please see git history for details)
+// 2021-02-18: Added ImGui_ImplWin32_EnableAlphaCompositing(). Non Visual Studio users will need to link with dwmapi.lib (MinGW/gcc: use -ldwmapi).
// 2021-02-17: Fixed ImGui_ImplWin32_EnableDpiAwareness() attempting to get SetProcessDpiAwareness from shcore.dll on Windows 8 whereas it is only supported on Windows 8.1.
// 2021-01-25: Inputs: Dynamically loading XInput DLL.
// 2020-12-04: Misc: Fixed setting of io.DisplaySize to invalid/uninitialized data when after hwnd has been closed.
@@ -457,7 +462,7 @@
}
#if defined(_MSC_VER) && !defined(NOGDI)
-#pragma comment(lib, "gdi32") // Link with gdi32.lib for GetDeviceCaps()
+#pragma comment(lib, "gdi32") // Link with gdi32.lib for GetDeviceCaps(). MinGW will require linking with '-lgdi32'
#endif
float ImGui_ImplWin32_GetDpiScaleForMonitor(void* monitor)
@@ -490,3 +495,43 @@
}
//---------------------------------------------------------------------------------------------------------
+// Transparency related helpers (optional)
+//--------------------------------------------------------------------------------------------------------
+
+#if defined(_MSC_VER)
+#pragma comment(lib, "dwmapi") // Link with dwmapi.lib. MinGW will require linking with '-ldwmapi'
+#endif
+
+// [experimental]
+// Borrowed from GLFW's function updateFramebufferTransparency() in src/win32_window.c
+// (the Dwm* functions are Vista era functions but we are borrowing logic from GLFW)
+void ImGui_ImplWin32_EnableAlphaCompositing(void* hwnd)
+{
+ if (!IsWindowsVistaOrGreater())
+ return;
+
+ BOOL composition;
+ if (FAILED(::DwmIsCompositionEnabled(&composition)) || !composition)
+ return;
+
+ BOOL opaque;
+ DWORD color;
+ if (IsWindows8OrGreater() || (SUCCEEDED(::DwmGetColorizationColor(&color, &opaque)) && !opaque))
+ {
+ HRGN region = ::CreateRectRgn(0, 0, -1, -1);
+ DWM_BLURBEHIND bb = {};
+ bb.dwFlags = DWM_BB_ENABLE | DWM_BB_BLURREGION;
+ bb.hRgnBlur = region;
+ bb.fEnable = TRUE;
+ ::DwmEnableBlurBehindWindow((HWND)hwnd, &bb);
+ ::DeleteObject(region);
+ }
+ else
+ {
+ DWM_BLURBEHIND bb = {};
+ bb.dwFlags = DWM_BB_ENABLE;
+ ::DwmEnableBlurBehindWindow((HWND)hwnd, &bb);
+ }
+}
+
+//---------------------------------------------------------------------------------------------------------
diff --git a/backends/imgui_impl_win32.h b/backends/imgui_impl_win32.h
index 0721d3e..5197b7f 100644
--- a/backends/imgui_impl_win32.h
+++ b/backends/imgui_impl_win32.h
@@ -18,10 +18,6 @@
IMGUI_IMPL_API void ImGui_ImplWin32_Shutdown();
IMGUI_IMPL_API void ImGui_ImplWin32_NewFrame();
-// Configuration
-// - Disable gamepad support
-//#define IMGUI_IMPL_WIN32_DISABLE_GAMEPAD
-
// Win32 message handler your application need to call.
// - Intentionally commented out in a '#if 0' block to avoid dragging dependencies on <windows.h> from this helper.
// - You should COPY the line below into your .cpp code to forward declare the function and then you can call it.
@@ -38,3 +34,8 @@
IMGUI_IMPL_API void ImGui_ImplWin32_EnableDpiAwareness();
IMGUI_IMPL_API float ImGui_ImplWin32_GetDpiScaleForHwnd(void* hwnd); // HWND hwnd
IMGUI_IMPL_API float ImGui_ImplWin32_GetDpiScaleForMonitor(void* monitor); // HMONITOR monitor
+
+// Transparency related helpers (optional) [experimental]
+// - Use to enable alpha compositing transparency with the desktop.
+// - Use together with e.g. clearing your framebuffer with zero-alpha.
+IMGUI_IMPL_API void ImGui_ImplWin32_EnableAlphaCompositing(void* hwnd); // HWND hwnd
diff --git a/docs/CHANGELOG.txt b/docs/CHANGELOG.txt
index 25b3848..74a4a25 100644
--- a/docs/CHANGELOG.txt
+++ b/docs/CHANGELOG.txt
@@ -39,12 +39,15 @@
- Style: renamed rarely used style.CircleSegmentMaxError (old default = 1.60f)
to style.CircleTessellationMaxError (new default = 0.30f) as its meaning changed. (#3808) [@thedmd]
+- Backends: Win32: Pragma linking with dwmapi.lib (Vista-era, ~9 kb). MinGW users will need to link with -ldwmapi.
Other Changes:
- ImDrawList: AddCircle, AddCircleFilled(): Tweaked default segment count calculation to honor MaxError
with more accuracy. Made default segment count always even for better looking result. (#3808) [@thedmd]
- ImDrawList: AddCircle, AddCircleFilled(): New default for style.
+- Backends: Win32: Added ImGui_ImplWin32_EnableAlphaCompositing() to facilitate experimenting with
+ alpha compositing and transparent windows. (#2766, #3447 etc.).
- Backends: OpenGL, Vulkan, DX9, DX10, DX11, DX12, Metal, WebGPU, Allegro: Rework blending equation to
preserve alpha in output buffer (using SrcBlendAlpha = ONE, DstBlendAlpha = ONE_MINUS_SRC_ALPHA consistently
accross all backends), facilitating compositing of the output buffer with another buffer.
