examples/sdl_opengl2_example/imgui_impl_sdl_gl2.cpp - external/github.com/ocornut/imgui - Git at Google

 // ImGui SDL2 binding with OpenGL (legacy, fixed pipeline)
 // (SDL is a cross-platform general purpose library for handling windows, inputs, OpenGL/Vulkan graphics context creation, etc.)

 // Implemented features:
 //  [X] User texture binding. Cast 'GLuint' OpenGL texture identifier as void*/ImTextureID. Read the FAQ about ImTextureID in imgui.cpp.
 // Missing features:
 //  [ ] SDL2 handling of IME under Windows appears to be broken and it explicitly disable the regular Windows IME. You can restore Windows IME by compiling SDL with SDL_DISABLE_WINDOWS_IME.

 // **DO NOT USE THIS CODE IF YOUR CODE/ENGINE IS USING MODERN OPENGL (SHADERS, VBO, VAO, etc.)**
 // **Prefer using the code in the sdl_opengl3_example/ folder**
 // This code is mostly provided as a reference to learn how ImGui integration works, because it is shorter to read.
 // If your code is using GL3+ context or any semi modern OpenGL calls, using this is likely to make everything more
 // complicated, will require your code to reset every single OpenGL attributes to their initial state, and might
 // confuse your GPU driver.
 // The GL2 code is unable to reset attributes or even call e.g. "glUseProgram(0)" because they don't exist in that API.

 // You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
 // If you use this binding you'll need to call 4 functions: ImGui_ImplXXXX_Init(), ImGui_ImplXXXX_NewFrame(), ImGui::Render() and ImGui_ImplXXXX_Shutdown().
 // If you are new to ImGui, see examples/README.txt and documentation at the top of imgui.cpp.
 // https://github.com/ocornut/imgui

 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
 //  2018-05-09: Misc: Fixed clipboard paste memory leak (we didn't call SDL_FreeMemory on the data returned by SDL_GetClipboardText).
 //  2018-03-20: Misc: Setup io.BackendFlags ImGuiBackendFlags_HasMouseCursors flag + honor ImGuiConfigFlags_NoMouseCursorChange flag.
 //  2018-02-16: Inputs: Added support for mouse cursors, honoring ImGui::GetMouseCursor() value.
 //  2018-02-16: Misc: Obsoleted the io.RenderDrawListsFn callback and exposed ImGui_ImplSdlGL2_RenderDrawData() in the .h file so you can call it yourself.
 //  2018-02-06: Misc: Removed call to ImGui::Shutdown() which is not available from 1.60 WIP, user needs to call CreateContext/DestroyContext themselves.
 //  2018-02-06: Inputs: Added mapping for ImGuiKey_Space.
 //  2018-02-05: Misc: Using SDL_GetPerformanceCounter() instead of SDL_GetTicks() to be able to handle very high framerate (1000+ FPS).
 //  2018-02-05: Inputs: Keyboard mapping is using scancodes everywhere instead of a confusing mixture of keycodes and scancodes.
 //  2018-01-20: Inputs: Added Horizontal Mouse Wheel support.
 //  2018-01-19: Inputs: When available (SDL 2.0.4+) using SDL_CaptureMouse() to retrieve coordinates outside of client area when dragging. Otherwise (SDL 2.0.3 and before) testing for SDL_WINDOW_INPUT_FOCUS instead of SDL_WINDOW_MOUSE_FOCUS.
 //  2018-01-18: Inputs: Added mapping for ImGuiKey_Insert.
 //  2017-09-01: OpenGL: Save and restore current polygon mode.
 //  2017-08-25: Inputs: MousePos set to -FLT_MAX,-FLT_MAX when mouse is unavailable/missing (instead of -1,-1).
 //  2016-10-15: Misc: Added a void* user_data parameter to Clipboard function handlers.
 //  2016-09-05: OpenGL: Fixed save and restore of current scissor rectangle.
 //  2016-07-29: OpenGL: Explicitly setting GL_UNPACK_ROW_LENGTH to reduce issues because SDL changes it. (#752)

 #include <SDL.h>
 #include <SDL_syswm.h>
 #include <SDL_opengl.h>
 #include "imgui.h"
 #include "imgui_impl_sdl_gl2.h"

 // Data
 static Uint64       g_Time = 0;
 static bool         g_MousePressed[3] = { false, false, false };
 static GLuint       g_FontTexture = 0;
 static SDL_Cursor*  g_MouseCursors[ImGuiMouseCursor_COUNT] = { 0 };
 static char*        g_ClipboardTextData = NULL;

 // OpenGL2 Render function.
 // (this used to be set in io.RenderDrawListsFn and called by ImGui::Render(), but you can now call this directly from your main loop)
 // Note that this implementation is little overcomplicated because we are saving/setting up/restoring every OpenGL state explicitly, in order to be able to run within any OpenGL engine that doesn't do so.
 void ImGui_ImplSdlGL2_RenderDrawData(ImDrawData* draw_data)
 {
     // Avoid rendering when minimized, scale coordinates for retina displays (screen coordinates != framebuffer coordinates)
     ImGuiIO& io = ImGui::GetIO();
     int fb_width = (int)(io.DisplaySize.x * io.DisplayFramebufferScale.x);
     int fb_height = (int)(io.DisplaySize.y * io.DisplayFramebufferScale.y);
     if (fb_width == 0 || fb_height == 0)
         return;
     draw_data->ScaleClipRects(io.DisplayFramebufferScale);

     // We are using the OpenGL fixed pipeline to make the example code simpler to read!
     // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled, vertex/texcoord/color pointers, polygon fill.
     GLint last_texture; glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
     GLint last_polygon_mode[2]; glGetIntegerv(GL_POLYGON_MODE, last_polygon_mode);
     GLint last_viewport[4]; glGetIntegerv(GL_VIEWPORT, last_viewport);
     GLint last_scissor_box[4]; glGetIntegerv(GL_SCISSOR_BOX, last_scissor_box);
     glPushAttrib(GL_ENABLE_BIT | GL_COLOR_BUFFER_BIT | GL_TRANSFORM_BIT);
     glEnable(GL_BLEND);
     glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
     glDisable(GL_CULL_FACE);
     glDisable(GL_DEPTH_TEST);
     glEnable(GL_SCISSOR_TEST);
     glEnableClientState(GL_VERTEX_ARRAY);
     glEnableClientState(GL_TEXTURE_COORD_ARRAY);
     glEnableClientState(GL_COLOR_ARRAY);
     glEnable(GL_TEXTURE_2D);
     glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
     //glUseProgram(0); // You may want this if using this code in an OpenGL 3+ context where shaders may be bound

     // Setup viewport, orthographic projection matrix
     glViewport(0, 0, (GLsizei)fb_width, (GLsizei)fb_height);
     glMatrixMode(GL_PROJECTION);
     glPushMatrix();
     glLoadIdentity();
     glOrtho(0.0f, io.DisplaySize.x, io.DisplaySize.y, 0.0f, -1.0f, +1.0f);
     glMatrixMode(GL_MODELVIEW);
     glPushMatrix();
     glLoadIdentity();

     // Render command lists
     for (int n = 0; n < draw_data->CmdListsCount; n++)
     {
         const ImDrawList* cmd_list = draw_data->CmdLists[n];
         const ImDrawVert* vtx_buffer = cmd_list->VtxBuffer.Data;
         const ImDrawIdx* idx_buffer = cmd_list->IdxBuffer.Data;
         glVertexPointer(2, GL_FLOAT, sizeof(ImDrawVert), (const GLvoid*)((const char*)vtx_buffer + IM_OFFSETOF(ImDrawVert, pos)));
         glTexCoordPointer(2, GL_FLOAT, sizeof(ImDrawVert), (const GLvoid*)((const char*)vtx_buffer + IM_OFFSETOF(ImDrawVert, uv)));
         glColorPointer(4, GL_UNSIGNED_BYTE, sizeof(ImDrawVert), (const GLvoid*)((const char*)vtx_buffer + IM_OFFSETOF(ImDrawVert, col)));

         for (int cmd_i = 0; cmd_i < cmd_list->CmdBuffer.Size; cmd_i++)
         {
             const ImDrawCmd* pcmd = &cmd_list->CmdBuffer[cmd_i];
             if (pcmd->UserCallback)
             {
                 pcmd->UserCallback(cmd_list, pcmd);
             }
             else
             {
                 glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->TextureId);
                 glScissor((int)pcmd->ClipRect.x, (int)(fb_height - pcmd->ClipRect.w), (int)(pcmd->ClipRect.z - pcmd->ClipRect.x), (int)(pcmd->ClipRect.w - pcmd->ClipRect.y));
                 glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, idx_buffer);
             }
             idx_buffer += pcmd->ElemCount;
         }
     }

     // Restore modified state
     glDisableClientState(GL_COLOR_ARRAY);
     glDisableClientState(GL_TEXTURE_COORD_ARRAY);
     glDisableClientState(GL_VERTEX_ARRAY);
     glBindTexture(GL_TEXTURE_2D, (GLuint)last_texture);
     glMatrixMode(GL_MODELVIEW);
     glPopMatrix();
     glMatrixMode(GL_PROJECTION);
     glPopMatrix();
     glPopAttrib();
     glPolygonMode(GL_FRONT, (GLenum)last_polygon_mode[0]); glPolygonMode(GL_BACK, (GLenum)last_polygon_mode[1]);
     glViewport(last_viewport[0], last_viewport[1], (GLsizei)last_viewport[2], (GLsizei)last_viewport[3]);
     glScissor(last_scissor_box[0], last_scissor_box[1], (GLsizei)last_scissor_box[2], (GLsizei)last_scissor_box[3]);
 }

 static const char* ImGui_ImplSdlGL2_GetClipboardText(void*)
 {
     if (g_ClipboardTextData)
         SDL_free(g_ClipboardTextData);
     g_ClipboardTextData = SDL_GetClipboardText();
     return g_ClipboardTextData;
 }

 static void ImGui_ImplSdlGL2_SetClipboardText(void*, const char* text)
 {
     SDL_SetClipboardText(text);
 }

 // You can read the io.WantCaptureMouse, io.WantCaptureKeyboard flags to tell if dear imgui wants to use your inputs.
 // - When io.WantCaptureMouse is true, do not dispatch mouse input data to your main application.
 // - When io.WantCaptureKeyboard is true, do not dispatch keyboard input data to your main application.
 // Generally you may always pass all inputs to dear imgui, and hide them from your application based on those two flags.
 bool ImGui_ImplSdlGL2_ProcessEvent(SDL_Event* event)
 {
     ImGuiIO& io = ImGui::GetIO();
     switch (event->type)
     {
     case SDL_MOUSEWHEEL:
         {
             if (event->wheel.x > 0) io.MouseWheelH += 1;
             if (event->wheel.x < 0) io.MouseWheelH -= 1;
             if (event->wheel.y > 0) io.MouseWheel += 1;
             if (event->wheel.y < 0) io.MouseWheel -= 1;
             return true;
         }
     case SDL_MOUSEBUTTONDOWN:
         {
             if (event->button.button == SDL_BUTTON_LEFT) g_MousePressed[0] = true;
             if (event->button.button == SDL_BUTTON_RIGHT) g_MousePressed[1] = true;
             if (event->button.button == SDL_BUTTON_MIDDLE) g_MousePressed[2] = true;
             return true;
         }
     case SDL_TEXTINPUT:
         {
             io.AddInputCharactersUTF8(event->text.text);
             return true;
         }
     case SDL_KEYDOWN:
     case SDL_KEYUP:
         {
             int key = event->key.keysym.scancode;
             IM_ASSERT(key >= 0 && key < IM_ARRAYSIZE(io.KeysDown));
             io.KeysDown[key] = (event->type == SDL_KEYDOWN);
             io.KeyShift = ((SDL_GetModState() & KMOD_SHIFT) != 0);
             io.KeyCtrl = ((SDL_GetModState() & KMOD_CTRL) != 0);
             io.KeyAlt = ((SDL_GetModState() & KMOD_ALT) != 0);
             io.KeySuper = ((SDL_GetModState() & KMOD_GUI) != 0);
             return true;
         }
     }
     return false;
 }

 bool ImGui_ImplSdlGL2_CreateDeviceObjects()
 {
     // Build texture atlas
     ImGuiIO& io = ImGui::GetIO();
     unsigned char* pixels;
     int width, height;
     io.Fonts->GetTexDataAsAlpha8(&pixels, &width, &height);

     // Upload texture to graphics system
     GLint last_texture;
     glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
     glGenTextures(1, &g_FontTexture);
     glBindTexture(GL_TEXTURE_2D, g_FontTexture);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
     glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
     glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, width, height, 0, GL_ALPHA, GL_UNSIGNED_BYTE, pixels);

     // Store our identifier
     io.Fonts->TexID = (void *)(intptr_t)g_FontTexture;

     // Restore state
     glBindTexture(GL_TEXTURE_2D, last_texture);

     return true;
 }

 void    ImGui_ImplSdlGL2_InvalidateDeviceObjects()
 {
     if (g_FontTexture)
     {
         glDeleteTextures(1, &g_FontTexture);
         ImGui::GetIO().Fonts->TexID = 0;
         g_FontTexture = 0;
     }
 }

 bool    ImGui_ImplSdlGL2_Init(SDL_Window* window)
 {
     // Setup back-end capabilities flags
     ImGuiIO& io = ImGui::GetIO();
     io.BackendFlags |= ImGuiBackendFlags_HasMouseCursors;   // We can honor GetMouseCursor() values (optional)

     // Keyboard mapping. ImGui will use those indices to peek into the io.KeysDown[] array.
     io.KeyMap[ImGuiKey_Tab] = SDL_SCANCODE_TAB;
     io.KeyMap[ImGuiKey_LeftArrow] = SDL_SCANCODE_LEFT;
     io.KeyMap[ImGuiKey_RightArrow] = SDL_SCANCODE_RIGHT;
     io.KeyMap[ImGuiKey_UpArrow] = SDL_SCANCODE_UP;
     io.KeyMap[ImGuiKey_DownArrow] = SDL_SCANCODE_DOWN;
     io.KeyMap[ImGuiKey_PageUp] = SDL_SCANCODE_PAGEUP;
     io.KeyMap[ImGuiKey_PageDown] = SDL_SCANCODE_PAGEDOWN;
     io.KeyMap[ImGuiKey_Home] = SDL_SCANCODE_HOME;
     io.KeyMap[ImGuiKey_End] = SDL_SCANCODE_END;
     io.KeyMap[ImGuiKey_Insert] = SDL_SCANCODE_INSERT;
     io.KeyMap[ImGuiKey_Delete] = SDL_SCANCODE_DELETE;
     io.KeyMap[ImGuiKey_Backspace] = SDL_SCANCODE_BACKSPACE;
     io.KeyMap[ImGuiKey_Space] = SDL_SCANCODE_SPACE;
     io.KeyMap[ImGuiKey_Enter] = SDL_SCANCODE_RETURN;
     io.KeyMap[ImGuiKey_Escape] = SDL_SCANCODE_ESCAPE;
     io.KeyMap[ImGuiKey_A] = SDL_SCANCODE_A;
     io.KeyMap[ImGuiKey_C] = SDL_SCANCODE_C;
     io.KeyMap[ImGuiKey_V] = SDL_SCANCODE_V;
     io.KeyMap[ImGuiKey_X] = SDL_SCANCODE_X;
     io.KeyMap[ImGuiKey_Y] = SDL_SCANCODE_Y;
     io.KeyMap[ImGuiKey_Z] = SDL_SCANCODE_Z;

     io.SetClipboardTextFn = ImGui_ImplSdlGL2_SetClipboardText;
     io.GetClipboardTextFn = ImGui_ImplSdlGL2_GetClipboardText;
     io.ClipboardUserData = NULL;

     g_MouseCursors[ImGuiMouseCursor_Arrow] = SDL_CreateSystemCursor(SDL_SYSTEM_CURSOR_ARROW);
     g_MouseCursors[ImGuiMouseCursor_TextInput] = SDL_CreateSystemCursor(SDL_SYSTEM_CURSOR_IBEAM);
     g_MouseCursors[ImGuiMouseCursor_ResizeAll] = SDL_CreateSystemCursor(SDL_SYSTEM_CURSOR_SIZEALL);
     g_MouseCursors[ImGuiMouseCursor_ResizeNS] = SDL_CreateSystemCursor(SDL_SYSTEM_CURSOR_SIZENS);
     g_MouseCursors[ImGuiMouseCursor_ResizeEW] = SDL_CreateSystemCursor(SDL_SYSTEM_CURSOR_SIZEWE);
     g_MouseCursors[ImGuiMouseCursor_ResizeNESW] = SDL_CreateSystemCursor(SDL_SYSTEM_CURSOR_SIZENESW);
     g_MouseCursors[ImGuiMouseCursor_ResizeNWSE] = SDL_CreateSystemCursor(SDL_SYSTEM_CURSOR_SIZENWSE);

 #ifdef _WIN32
     SDL_SysWMinfo wmInfo;
     SDL_VERSION(&wmInfo.version);
     SDL_GetWindowWMInfo(window, &wmInfo);
     io.ImeWindowHandle = wmInfo.info.win.window;
 #else
     (void)window;
 #endif

     return true;
 }

 void ImGui_ImplSdlGL2_Shutdown()
 {
     // Destroy SDL mouse cursors
     for (ImGuiMouseCursor cursor_n = 0; cursor_n < ImGuiMouseCursor_COUNT; cursor_n++)
         SDL_FreeCursor(g_MouseCursors[cursor_n]);
     memset(g_MouseCursors, 0, sizeof(g_MouseCursors));

     // Destroy last known clipboard data
     if (g_ClipboardTextData)
         SDL_free(g_ClipboardTextData);

     // Destroy OpenGL objects
     ImGui_ImplSdlGL2_InvalidateDeviceObjects();
 }

 void ImGui_ImplSdlGL2_NewFrame(SDL_Window *window)
 {
     if (!g_FontTexture)
         ImGui_ImplSdlGL2_CreateDeviceObjects();

     ImGuiIO& io = ImGui::GetIO();

     // Setup display size (every frame to accommodate for window resizing)
     int w, h;
     int display_w, display_h;
     SDL_GetWindowSize(window, &w, &h);
     SDL_GL_GetDrawableSize(window, &display_w, &display_h);
     io.DisplaySize = ImVec2((float)w, (float)h);
     io.DisplayFramebufferScale = ImVec2(w > 0 ? ((float)display_w / w) : 0, h > 0 ? ((float)display_h / h) : 0);

     // Setup time step (we don't use SDL_GetTicks() because it is using millisecond resolution)
     static Uint64 frequency = SDL_GetPerformanceFrequency();
     Uint64 current_time = SDL_GetPerformanceCounter();
     io.DeltaTime = g_Time > 0 ? (float)((double)(current_time - g_Time) / frequency) : (float)(1.0f / 60.0f);
     g_Time = current_time;

     // Setup mouse inputs (we already got mouse wheel, keyboard keys & characters from our event handler)
     int mx, my;
     Uint32 mouse_buttons = SDL_GetMouseState(&mx, &my);
     io.MousePos = ImVec2(-FLT_MAX, -FLT_MAX);
     io.MouseDown[0] = g_MousePressed[0] || (mouse_buttons & SDL_BUTTON(SDL_BUTTON_LEFT)) != 0;  // If a mouse press event came, always pass it as "mouse held this frame", so we don't miss click-release events that are shorter than 1 frame.
     io.MouseDown[1] = g_MousePressed[1] || (mouse_buttons & SDL_BUTTON(SDL_BUTTON_RIGHT)) != 0;
     io.MouseDown[2] = g_MousePressed[2] || (mouse_buttons & SDL_BUTTON(SDL_BUTTON_MIDDLE)) != 0;
     g_MousePressed[0] = g_MousePressed[1] = g_MousePressed[2] = false;

     // We need to use SDL_CaptureMouse() to easily retrieve mouse coordinates outside of the client area. This is only supported from SDL 2.0.4 (released Jan 2016)
 #if (SDL_MAJOR_VERSION >= 2) && (SDL_MINOR_VERSION >= 0) && (SDL_PATCHLEVEL >= 4)
     if ((SDL_GetWindowFlags(window) & (SDL_WINDOW_MOUSE_FOCUS | SDL_WINDOW_MOUSE_CAPTURE)) != 0)
         io.MousePos = ImVec2((float)mx, (float)my);
     bool any_mouse_button_down = false;
     for (int n = 0; n < IM_ARRAYSIZE(io.MouseDown); n++)
         any_mouse_button_down |= io.MouseDown[n];
     if (any_mouse_button_down && (SDL_GetWindowFlags(window) & SDL_WINDOW_MOUSE_CAPTURE) == 0)
         SDL_CaptureMouse(SDL_TRUE);
     if (!any_mouse_button_down && (SDL_GetWindowFlags(window) & SDL_WINDOW_MOUSE_CAPTURE) != 0)
         SDL_CaptureMouse(SDL_FALSE);
 #else
     if ((SDL_GetWindowFlags(window) & SDL_WINDOW_INPUT_FOCUS) != 0)
         io.MousePos = ImVec2((float)mx, (float)my);
 #endif

     // Update OS/hardware mouse cursor if imgui isn't drawing a software cursor
     if ((io.ConfigFlags & ImGuiConfigFlags_NoMouseCursorChange) == 0)
     {
         ImGuiMouseCursor cursor = ImGui::GetMouseCursor();
         if (io.MouseDrawCursor || cursor == ImGuiMouseCursor_None)
         {
             SDL_ShowCursor(0);
         }
         else
         {
             SDL_SetCursor(g_MouseCursors[cursor] ? g_MouseCursors[cursor] : g_MouseCursors[ImGuiMouseCursor_Arrow]);
             SDL_ShowCursor(1);
         }
     }

     // Start the frame. This call will update the io.WantCaptureMouse, io.WantCaptureKeyboard flag that you can use to dispatch inputs (or not) to your application.
     ImGui::NewFrame();
 }
	// ImGui SDL2 binding with OpenGL (legacy, fixed pipeline)
	// (SDL is a cross-platform general purpose library for handling windows, inputs, OpenGL/Vulkan graphics context creation, etc.)

	// Implemented features:
	// [X] User texture binding. Cast 'GLuint' OpenGL texture identifier as void*/ImTextureID. Read the FAQ about ImTextureID in imgui.cpp.
	// Missing features:
	// [ ] SDL2 handling of IME under Windows appears to be broken and it explicitly disable the regular Windows IME. You can restore Windows IME by compiling SDL with SDL_DISABLE_WINDOWS_IME.

	// DO NOT USE THIS CODE IF YOUR CODE/ENGINE IS USING MODERN OPENGL (SHADERS, VBO, VAO, etc.)
	// Prefer using the code in the sdl_opengl3_example/ folder
	// This code is mostly provided as a reference to learn how ImGui integration works, because it is shorter to read.
	// If your code is using GL3+ context or any semi modern OpenGL calls, using this is likely to make everything more
	// complicated, will require your code to reset every single OpenGL attributes to their initial state, and might
	// confuse your GPU driver.
	// The GL2 code is unable to reset attributes or even call e.g. "glUseProgram(0)" because they don't exist in that API.

	// You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
	// If you use this binding you'll need to call 4 functions: ImGui_ImplXXXX_Init(), ImGui_ImplXXXX_NewFrame(), ImGui::Render() and ImGui_ImplXXXX_Shutdown().
	// If you are new to ImGui, see examples/README.txt and documentation at the top of imgui.cpp.
	// https://github.com/ocornut/imgui

	// CHANGELOG
	// (minor and older changes stripped away, please see git history for details)
	// 2018-05-09: Misc: Fixed clipboard paste memory leak (we didn't call SDL_FreeMemory on the data returned by SDL_GetClipboardText).
	// 2018-03-20: Misc: Setup io.BackendFlags ImGuiBackendFlags_HasMouseCursors flag + honor ImGuiConfigFlags_NoMouseCursorChange flag.
	// 2018-02-16: Inputs: Added support for mouse cursors, honoring ImGui::GetMouseCursor() value.
	// 2018-02-16: Misc: Obsoleted the io.RenderDrawListsFn callback and exposed ImGui_ImplSdlGL2_RenderDrawData() in the .h file so you can call it yourself.
	// 2018-02-06: Misc: Removed call to ImGui::Shutdown() which is not available from 1.60 WIP, user needs to call CreateContext/DestroyContext themselves.
	// 2018-02-06: Inputs: Added mapping for ImGuiKey_Space.
	// 2018-02-05: Misc: Using SDL_GetPerformanceCounter() instead of SDL_GetTicks() to be able to handle very high framerate (1000+ FPS).
	// 2018-02-05: Inputs: Keyboard mapping is using scancodes everywhere instead of a confusing mixture of keycodes and scancodes.
	// 2018-01-20: Inputs: Added Horizontal Mouse Wheel support.
	// 2018-01-19: Inputs: When available (SDL 2.0.4+) using SDL_CaptureMouse() to retrieve coordinates outside of client area when dragging. Otherwise (SDL 2.0.3 and before) testing for SDL_WINDOW_INPUT_FOCUS instead of SDL_WINDOW_MOUSE_FOCUS.
	// 2018-01-18: Inputs: Added mapping for ImGuiKey_Insert.
	// 2017-09-01: OpenGL: Save and restore current polygon mode.
	// 2017-08-25: Inputs: MousePos set to -FLT_MAX,-FLT_MAX when mouse is unavailable/missing (instead of -1,-1).
	// 2016-10-15: Misc: Added a void* user_data parameter to Clipboard function handlers.
	// 2016-09-05: OpenGL: Fixed save and restore of current scissor rectangle.
	// 2016-07-29: OpenGL: Explicitly setting GL_UNPACK_ROW_LENGTH to reduce issues because SDL changes it. (#752)

	#include <SDL.h>
	#include <SDL_syswm.h>
	#include <SDL_opengl.h>
	#include "imgui.h"
	#include "imgui_impl_sdl_gl2.h"

	// Data
	static Uint64 g_Time = 0;
	static bool g_MousePressed[3] = { false, false, false };
	static GLuint g_FontTexture = 0;
	static SDL_Cursor* g_MouseCursors[ImGuiMouseCursor_COUNT] = { 0 };
	static char* g_ClipboardTextData = NULL;

	// OpenGL2 Render function.
	// (this used to be set in io.RenderDrawListsFn and called by ImGui::Render(), but you can now call this directly from your main loop)
	// Note that this implementation is little overcomplicated because we are saving/setting up/restoring every OpenGL state explicitly, in order to be able to run within any OpenGL engine that doesn't do so.
	void ImGui_ImplSdlGL2_RenderDrawData(ImDrawData* draw_data)
	{
	// Avoid rendering when minimized, scale coordinates for retina displays (screen coordinates != framebuffer coordinates)
	ImGuiIO& io = ImGui::GetIO();
	int fb_width = (int)(io.DisplaySize.x * io.DisplayFramebufferScale.x);
	int fb_height = (int)(io.DisplaySize.y * io.DisplayFramebufferScale.y);
	if (fb_width == 0 \|\| fb_height == 0)
	return;
	draw_data->ScaleClipRects(io.DisplayFramebufferScale);

	// We are using the OpenGL fixed pipeline to make the example code simpler to read!
	// Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled, vertex/texcoord/color pointers, polygon fill.
	GLint last_texture; glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
	GLint last_polygon_mode[2]; glGetIntegerv(GL_POLYGON_MODE, last_polygon_mode);
	GLint last_viewport[4]; glGetIntegerv(GL_VIEWPORT, last_viewport);
	GLint last_scissor_box[4]; glGetIntegerv(GL_SCISSOR_BOX, last_scissor_box);
	glPushAttrib(GL_ENABLE_BIT \| GL_COLOR_BUFFER_BIT \| GL_TRANSFORM_BIT);
	glEnable(GL_BLEND);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
	glDisable(GL_CULL_FACE);
	glDisable(GL_DEPTH_TEST);
	glEnable(GL_SCISSOR_TEST);
	glEnableClientState(GL_VERTEX_ARRAY);
	glEnableClientState(GL_TEXTURE_COORD_ARRAY);
	glEnableClientState(GL_COLOR_ARRAY);
	glEnable(GL_TEXTURE_2D);
	glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
	//glUseProgram(0); // You may want this if using this code in an OpenGL 3+ context where shaders may be bound

	// Setup viewport, orthographic projection matrix
	glViewport(0, 0, (GLsizei)fb_width, (GLsizei)fb_height);
	glMatrixMode(GL_PROJECTION);
	glPushMatrix();
	glLoadIdentity();
	glOrtho(0.0f, io.DisplaySize.x, io.DisplaySize.y, 0.0f, -1.0f, +1.0f);
	glMatrixMode(GL_MODELVIEW);
	glPushMatrix();
	glLoadIdentity();

	// Render command lists
	for (int n = 0; n < draw_data->CmdListsCount; n++)
	{
	const ImDrawList* cmd_list = draw_data->CmdLists[n];
	const ImDrawVert* vtx_buffer = cmd_list->VtxBuffer.Data;
	const ImDrawIdx* idx_buffer = cmd_list->IdxBuffer.Data;
	glVertexPointer(2, GL_FLOAT, sizeof(ImDrawVert), (const GLvoid)((const char)vtx_buffer + IM_OFFSETOF(ImDrawVert, pos)));
	glTexCoordPointer(2, GL_FLOAT, sizeof(ImDrawVert), (const GLvoid)((const char)vtx_buffer + IM_OFFSETOF(ImDrawVert, uv)));
	glColorPointer(4, GL_UNSIGNED_BYTE, sizeof(ImDrawVert), (const GLvoid)((const char)vtx_buffer + IM_OFFSETOF(ImDrawVert, col)));

	for (int cmd_i = 0; cmd_i < cmd_list->CmdBuffer.Size; cmd_i++)
	{
	const ImDrawCmd* pcmd = &cmd_list->CmdBuffer[cmd_i];
	if (pcmd->UserCallback)
	{
	pcmd->UserCallback(cmd_list, pcmd);
	}
	else
	{
	glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->TextureId);
	glScissor((int)pcmd->ClipRect.x, (int)(fb_height - pcmd->ClipRect.w), (int)(pcmd->ClipRect.z - pcmd->ClipRect.x), (int)(pcmd->ClipRect.w - pcmd->ClipRect.y));
	glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, idx_buffer);
	}
	idx_buffer += pcmd->ElemCount;
	}
	}

	// Restore modified state
	glDisableClientState(GL_COLOR_ARRAY);
	glDisableClientState(GL_TEXTURE_COORD_ARRAY);
	glDisableClientState(GL_VERTEX_ARRAY);
	glBindTexture(GL_TEXTURE_2D, (GLuint)last_texture);
	glMatrixMode(GL_MODELVIEW);
	glPopMatrix();
	glMatrixMode(GL_PROJECTION);
	glPopMatrix();
	glPopAttrib();
	glPolygonMode(GL_FRONT, (GLenum)last_polygon_mode[0]); glPolygonMode(GL_BACK, (GLenum)last_polygon_mode[1]);
	glViewport(last_viewport[0], last_viewport[1], (GLsizei)last_viewport[2], (GLsizei)last_viewport[3]);
	glScissor(last_scissor_box[0], last_scissor_box[1], (GLsizei)last_scissor_box[2], (GLsizei)last_scissor_box[3]);
	}

	static const char* ImGui_ImplSdlGL2_GetClipboardText(void*)
	{
	if (g_ClipboardTextData)
	SDL_free(g_ClipboardTextData);
	g_ClipboardTextData = SDL_GetClipboardText();
	return g_ClipboardTextData;
	}

	static void ImGui_ImplSdlGL2_SetClipboardText(void, const char text)
	{
	SDL_SetClipboardText(text);
	}

	// You can read the io.WantCaptureMouse, io.WantCaptureKeyboard flags to tell if dear imgui wants to use your inputs.
	// - When io.WantCaptureMouse is true, do not dispatch mouse input data to your main application.
	// - When io.WantCaptureKeyboard is true, do not dispatch keyboard input data to your main application.
	// Generally you may always pass all inputs to dear imgui, and hide them from your application based on those two flags.
	bool ImGui_ImplSdlGL2_ProcessEvent(SDL_Event* event)
	{
	ImGuiIO& io = ImGui::GetIO();
	switch (event->type)
	{
	case SDL_MOUSEWHEEL:
	{
	if (event->wheel.x > 0) io.MouseWheelH += 1;
	if (event->wheel.x < 0) io.MouseWheelH -= 1;
	if (event->wheel.y > 0) io.MouseWheel += 1;
	if (event->wheel.y < 0) io.MouseWheel -= 1;
	return true;
	}
	case SDL_MOUSEBUTTONDOWN:
	{
	if (event->button.button == SDL_BUTTON_LEFT) g_MousePressed[0] = true;
	if (event->button.button == SDL_BUTTON_RIGHT) g_MousePressed[1] = true;
	if (event->button.button == SDL_BUTTON_MIDDLE) g_MousePressed[2] = true;
	return true;
	}
	case SDL_TEXTINPUT:
	{
	io.AddInputCharactersUTF8(event->text.text);
	return true;
	}
	case SDL_KEYDOWN:
	case SDL_KEYUP:
	{
	int key = event->key.keysym.scancode;
	IM_ASSERT(key >= 0 && key < IM_ARRAYSIZE(io.KeysDown));
	io.KeysDown[key] = (event->type == SDL_KEYDOWN);
	io.KeyShift = ((SDL_GetModState() & KMOD_SHIFT) != 0);
	io.KeyCtrl = ((SDL_GetModState() & KMOD_CTRL) != 0);
	io.KeyAlt = ((SDL_GetModState() & KMOD_ALT) != 0);
	io.KeySuper = ((SDL_GetModState() & KMOD_GUI) != 0);
	return true;
	}
	}
	return false;
	}

	bool ImGui_ImplSdlGL2_CreateDeviceObjects()
	{
	// Build texture atlas
	ImGuiIO& io = ImGui::GetIO();
	unsigned char* pixels;
	int width, height;
	io.Fonts->GetTexDataAsAlpha8(&pixels, &width, &height);

	// Upload texture to graphics system
	GLint last_texture;
	glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
	glGenTextures(1, &g_FontTexture);
	glBindTexture(GL_TEXTURE_2D, g_FontTexture);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
	glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, width, height, 0, GL_ALPHA, GL_UNSIGNED_BYTE, pixels);

	// Store our identifier
	io.Fonts->TexID = (void *)(intptr_t)g_FontTexture;

	// Restore state
	glBindTexture(GL_TEXTURE_2D, last_texture);

	return true;
	}

	void ImGui_ImplSdlGL2_InvalidateDeviceObjects()
	{
	if (g_FontTexture)
	{
	glDeleteTextures(1, &g_FontTexture);
	ImGui::GetIO().Fonts->TexID = 0;
	g_FontTexture = 0;
	}
	}

	bool ImGui_ImplSdlGL2_Init(SDL_Window* window)
	{
	// Setup back-end capabilities flags
	ImGuiIO& io = ImGui::GetIO();
	io.BackendFlags \|= ImGuiBackendFlags_HasMouseCursors; // We can honor GetMouseCursor() values (optional)

	// Keyboard mapping. ImGui will use those indices to peek into the io.KeysDown[] array.
	io.KeyMap[ImGuiKey_Tab] = SDL_SCANCODE_TAB;
	io.KeyMap[ImGuiKey_LeftArrow] = SDL_SCANCODE_LEFT;
	io.KeyMap[ImGuiKey_RightArrow] = SDL_SCANCODE_RIGHT;
	io.KeyMap[ImGuiKey_UpArrow] = SDL_SCANCODE_UP;
	io.KeyMap[ImGuiKey_DownArrow] = SDL_SCANCODE_DOWN;
	io.KeyMap[ImGuiKey_PageUp] = SDL_SCANCODE_PAGEUP;
	io.KeyMap[ImGuiKey_PageDown] = SDL_SCANCODE_PAGEDOWN;
	io.KeyMap[ImGuiKey_Home] = SDL_SCANCODE_HOME;
	io.KeyMap[ImGuiKey_End] = SDL_SCANCODE_END;
	io.KeyMap[ImGuiKey_Insert] = SDL_SCANCODE_INSERT;
	io.KeyMap[ImGuiKey_Delete] = SDL_SCANCODE_DELETE;
	io.KeyMap[ImGuiKey_Backspace] = SDL_SCANCODE_BACKSPACE;
	io.KeyMap[ImGuiKey_Space] = SDL_SCANCODE_SPACE;
	io.KeyMap[ImGuiKey_Enter] = SDL_SCANCODE_RETURN;
	io.KeyMap[ImGuiKey_Escape] = SDL_SCANCODE_ESCAPE;
	io.KeyMap[ImGuiKey_A] = SDL_SCANCODE_A;
	io.KeyMap[ImGuiKey_C] = SDL_SCANCODE_C;
	io.KeyMap[ImGuiKey_V] = SDL_SCANCODE_V;
	io.KeyMap[ImGuiKey_X] = SDL_SCANCODE_X;
	io.KeyMap[ImGuiKey_Y] = SDL_SCANCODE_Y;
	io.KeyMap[ImGuiKey_Z] = SDL_SCANCODE_Z;

	io.SetClipboardTextFn = ImGui_ImplSdlGL2_SetClipboardText;
	io.GetClipboardTextFn = ImGui_ImplSdlGL2_GetClipboardText;
	io.ClipboardUserData = NULL;

	g_MouseCursors[ImGuiMouseCursor_Arrow] = SDL_CreateSystemCursor(SDL_SYSTEM_CURSOR_ARROW);
	g_MouseCursors[ImGuiMouseCursor_TextInput] = SDL_CreateSystemCursor(SDL_SYSTEM_CURSOR_IBEAM);
	g_MouseCursors[ImGuiMouseCursor_ResizeAll] = SDL_CreateSystemCursor(SDL_SYSTEM_CURSOR_SIZEALL);
	g_MouseCursors[ImGuiMouseCursor_ResizeNS] = SDL_CreateSystemCursor(SDL_SYSTEM_CURSOR_SIZENS);
	g_MouseCursors[ImGuiMouseCursor_ResizeEW] = SDL_CreateSystemCursor(SDL_SYSTEM_CURSOR_SIZEWE);
	g_MouseCursors[ImGuiMouseCursor_ResizeNESW] = SDL_CreateSystemCursor(SDL_SYSTEM_CURSOR_SIZENESW);
	g_MouseCursors[ImGuiMouseCursor_ResizeNWSE] = SDL_CreateSystemCursor(SDL_SYSTEM_CURSOR_SIZENWSE);

	#ifdef _WIN32
	SDL_SysWMinfo wmInfo;
	SDL_VERSION(&wmInfo.version);
	SDL_GetWindowWMInfo(window, &wmInfo);
	io.ImeWindowHandle = wmInfo.info.win.window;
	#else
	(void)window;
	#endif

	return true;
	}

	void ImGui_ImplSdlGL2_Shutdown()
	{
	// Destroy SDL mouse cursors
	for (ImGuiMouseCursor cursor_n = 0; cursor_n < ImGuiMouseCursor_COUNT; cursor_n++)
	SDL_FreeCursor(g_MouseCursors[cursor_n]);
	memset(g_MouseCursors, 0, sizeof(g_MouseCursors));

	// Destroy last known clipboard data
	if (g_ClipboardTextData)
	SDL_free(g_ClipboardTextData);

	// Destroy OpenGL objects
	ImGui_ImplSdlGL2_InvalidateDeviceObjects();
	}

	void ImGui_ImplSdlGL2_NewFrame(SDL_Window *window)
	{
	if (!g_FontTexture)
	ImGui_ImplSdlGL2_CreateDeviceObjects();

	ImGuiIO& io = ImGui::GetIO();

	// Setup display size (every frame to accommodate for window resizing)
	int w, h;
	int display_w, display_h;
	SDL_GetWindowSize(window, &w, &h);
	SDL_GL_GetDrawableSize(window, &display_w, &display_h);
	io.DisplaySize = ImVec2((float)w, (float)h);
	io.DisplayFramebufferScale = ImVec2(w > 0 ? ((float)display_w / w) : 0, h > 0 ? ((float)display_h / h) : 0);

	// Setup time step (we don't use SDL_GetTicks() because it is using millisecond resolution)
	static Uint64 frequency = SDL_GetPerformanceFrequency();
	Uint64 current_time = SDL_GetPerformanceCounter();
	io.DeltaTime = g_Time > 0 ? (float)((double)(current_time - g_Time) / frequency) : (float)(1.0f / 60.0f);
	g_Time = current_time;

	// Setup mouse inputs (we already got mouse wheel, keyboard keys & characters from our event handler)
	int mx, my;
	Uint32 mouse_buttons = SDL_GetMouseState(&mx, &my);
	io.MousePos = ImVec2(-FLT_MAX, -FLT_MAX);
	io.MouseDown[0] = g_MousePressed[0] \|\| (mouse_buttons & SDL_BUTTON(SDL_BUTTON_LEFT)) != 0; // If a mouse press event came, always pass it as "mouse held this frame", so we don't miss click-release events that are shorter than 1 frame.
	io.MouseDown[1] = g_MousePressed[1] \|\| (mouse_buttons & SDL_BUTTON(SDL_BUTTON_RIGHT)) != 0;
	io.MouseDown[2] = g_MousePressed[2] \|\| (mouse_buttons & SDL_BUTTON(SDL_BUTTON_MIDDLE)) != 0;
	g_MousePressed[0] = g_MousePressed[1] = g_MousePressed[2] = false;

	// We need to use SDL_CaptureMouse() to easily retrieve mouse coordinates outside of the client area. This is only supported from SDL 2.0.4 (released Jan 2016)
	#if (SDL_MAJOR_VERSION >= 2) && (SDL_MINOR_VERSION >= 0) && (SDL_PATCHLEVEL >= 4)
	if ((SDL_GetWindowFlags(window) & (SDL_WINDOW_MOUSE_FOCUS \| SDL_WINDOW_MOUSE_CAPTURE)) != 0)
	io.MousePos = ImVec2((float)mx, (float)my);
	bool any_mouse_button_down = false;
	for (int n = 0; n < IM_ARRAYSIZE(io.MouseDown); n++)
	any_mouse_button_down \|= io.MouseDown[n];
	if (any_mouse_button_down && (SDL_GetWindowFlags(window) & SDL_WINDOW_MOUSE_CAPTURE) == 0)
	SDL_CaptureMouse(SDL_TRUE);
	if (!any_mouse_button_down && (SDL_GetWindowFlags(window) & SDL_WINDOW_MOUSE_CAPTURE) != 0)
	SDL_CaptureMouse(SDL_FALSE);
	#else
	if ((SDL_GetWindowFlags(window) & SDL_WINDOW_INPUT_FOCUS) != 0)
	io.MousePos = ImVec2((float)mx, (float)my);
	#endif

	// Update OS/hardware mouse cursor if imgui isn't drawing a software cursor
	if ((io.ConfigFlags & ImGuiConfigFlags_NoMouseCursorChange) == 0)
	{
	ImGuiMouseCursor cursor = ImGui::GetMouseCursor();
	if (io.MouseDrawCursor \|\| cursor == ImGuiMouseCursor_None)
	{
	SDL_ShowCursor(0);
	}
	else
	{
	SDL_SetCursor(g_MouseCursors[cursor] ? g_MouseCursors[cursor] : g_MouseCursors[ImGuiMouseCursor_Arrow]);
	SDL_ShowCursor(1);
	}
	}

	// Start the frame. This call will update the io.WantCaptureMouse, io.WantCaptureKeyboard flag that you can use to dispatch inputs (or not) to your application.
	ImGui::NewFrame();
	}