examples/opengl2_example/imgui_impl_glfw_gl2.cpp - external/github.com/ocornut/imgui - Git at Google

 // ImGui GLFW binding with OpenGL (legacy, fixed pipeline)
 // (GLFW 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.

 // **DO NOT USE THIS CODE IF YOUR CODE/ENGINE IS USING MODERN OPENGL (SHADERS, VBO, VAO, etc.)**
 // **Prefer using the code in the 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)
 //  2018-03-20: Misc: Setup io.BackendFlags ImGuiBackendFlags_HasMouseCursors and ImGuiBackendFlags_HasSetMousePos flags + honor ImGuiConfigFlags_NoMouseCursorChange flag.
 //  2018-02-20: Inputs: Added support for mouse cursors (ImGui::GetMouseCursor() value, passed to glfwSetCursor()).
 //  2018-02-20: Inputs: Renamed GLFW callbacks exposed in .h to not include GL2 in their name.
 //  2018-02-16: Misc: Obsoleted the io.RenderDrawListsFn callback and exposed ImGui_ImplGlfwGL2_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.
 //  2018-02-06: Inputs: Honoring the io.WantSetMousePos flag by repositioning the mouse (ImGuiConfigFlags_NavEnableSetMousePos is set).
 //  2018-01-20: Inputs: Added Horizontal Mouse Wheel support.
 //  2018-01-18: Inputs: Added mapping for ImGuiKey_Insert.
 //  2018-01-09: Misc: Renamed imgui_impl_glfw.* to imgui_impl_glfw_gl2.*.
 //  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.
 //  2016-09-10: OpenGL: Uploading font texture as RGBA32 to increase compatibility with users shaders (not ideal).
 //  2016-09-05: OpenGL: Fixed save and restore of current scissor rectangle.

 #include "imgui.h"
 #include "imgui_impl_glfw_gl2.h"

 // GLFW
 #include <GLFW/glfw3.h>
 #ifdef _WIN32
 #undef APIENTRY
 #define GLFW_EXPOSE_NATIVE_WIN32
 #define GLFW_EXPOSE_NATIVE_WGL
 #include <GLFW/glfw3native.h>
 #endif

 // GLFW data
 static GLFWwindow*  g_Window = NULL;
 static double       g_Time = 0.0f;
 static bool         g_MouseJustPressed[3] = { false, false, false };
 static GLFWcursor*  g_MouseCursors[ImGuiMouseCursor_COUNT] = { 0 };

 // OpenGL data
 static GLuint       g_FontTexture = 0;

 // 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_ImplGlfwGL2_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_ImplGlfwGL2_GetClipboardText(void* user_data)
 {
     return glfwGetClipboardString((GLFWwindow*)user_data);
 }

 static void ImGui_ImplGlfwGL2_SetClipboardText(void* user_data, const char* text)
 {
     glfwSetClipboardString((GLFWwindow*)user_data, text);
 }

 void ImGui_ImplGlfw_MouseButtonCallback(GLFWwindow*, int button, int action, int /*mods*/)
 {
     if (action == GLFW_PRESS && button >= 0 && button < 3)
         g_MouseJustPressed[button] = true;
 }

 void ImGui_ImplGlfw_ScrollCallback(GLFWwindow*, double xoffset, double yoffset)
 {
     ImGuiIO& io = ImGui::GetIO();
     io.MouseWheelH += (float)xoffset;
     io.MouseWheel += (float)yoffset;
 }

 void ImGui_ImplGlfw_KeyCallback(GLFWwindow*, int key, int, int action, int mods)
 {
     ImGuiIO& io = ImGui::GetIO();
     if (action == GLFW_PRESS)
         io.KeysDown[key] = true;
     if (action == GLFW_RELEASE)
         io.KeysDown[key] = false;

     (void)mods; // Modifiers are not reliable across systems
     io.KeyCtrl = io.KeysDown[GLFW_KEY_LEFT_CONTROL] || io.KeysDown[GLFW_KEY_RIGHT_CONTROL];
     io.KeyShift = io.KeysDown[GLFW_KEY_LEFT_SHIFT] || io.KeysDown[GLFW_KEY_RIGHT_SHIFT];
     io.KeyAlt = io.KeysDown[GLFW_KEY_LEFT_ALT] || io.KeysDown[GLFW_KEY_RIGHT_ALT];
     io.KeySuper = io.KeysDown[GLFW_KEY_LEFT_SUPER] || io.KeysDown[GLFW_KEY_RIGHT_SUPER];
 }

 void ImGui_ImplGlfw_CharCallback(GLFWwindow*, unsigned int c)
 {
     ImGuiIO& io = ImGui::GetIO();
     if (c > 0 && c < 0x10000)
         io.AddInputCharacter((unsigned short)c);
 }

 bool ImGui_ImplGlfwGL2_CreateDeviceObjects()
 {
     // Build texture atlas
     ImGuiIO& io = ImGui::GetIO();
     unsigned char* pixels;
     int width, height;
     io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);   // Load as RGBA 32-bits (75% of the memory is wasted, but default font is so small) because it is more likely to be compatible with user's existing shaders. If your ImTextureId represent a higher-level concept than just a GL texture id, consider calling GetTexDataAsAlpha8() instead to save on GPU memory.

     // 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_RGBA, width, height, 0, GL_RGBA, 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_ImplGlfwGL2_InvalidateDeviceObjects()
 {
     if (g_FontTexture)
     {
         glDeleteTextures(1, &g_FontTexture);
         ImGui::GetIO().Fonts->TexID = 0;
         g_FontTexture = 0;
     }
 }

 static void ImGui_ImplGlfw_InstallCallbacks(GLFWwindow* window)
 {
     glfwSetMouseButtonCallback(window, ImGui_ImplGlfw_MouseButtonCallback);
     glfwSetScrollCallback(window, ImGui_ImplGlfw_ScrollCallback);
     glfwSetKeyCallback(window, ImGui_ImplGlfw_KeyCallback);
     glfwSetCharCallback(window, ImGui_ImplGlfw_CharCallback);
 }

 bool    ImGui_ImplGlfwGL2_Init(GLFWwindow* window, bool install_callbacks)
 {
     g_Window = window;

     // Setup back-end capabilities flags
     ImGuiIO& io = ImGui::GetIO();
     io.BackendFlags |= ImGuiBackendFlags_HasMouseCursors;   // We can honor GetMouseCursor() values (optional)
     io.BackendFlags |= ImGuiBackendFlags_HasSetMousePos;    // We can honor io.WantSetMousePos requests (optional, rarely used)

     // Keyboard mapping. ImGui will use those indices to peek into the io.KeysDown[] array.
     io.KeyMap[ImGuiKey_Tab] = GLFW_KEY_TAB;
     io.KeyMap[ImGuiKey_LeftArrow] = GLFW_KEY_LEFT;
     io.KeyMap[ImGuiKey_RightArrow] = GLFW_KEY_RIGHT;
     io.KeyMap[ImGuiKey_UpArrow] = GLFW_KEY_UP;
     io.KeyMap[ImGuiKey_DownArrow] = GLFW_KEY_DOWN;
     io.KeyMap[ImGuiKey_PageUp] = GLFW_KEY_PAGE_UP;
     io.KeyMap[ImGuiKey_PageDown] = GLFW_KEY_PAGE_DOWN;
     io.KeyMap[ImGuiKey_Home] = GLFW_KEY_HOME;
     io.KeyMap[ImGuiKey_End] = GLFW_KEY_END;
     io.KeyMap[ImGuiKey_Insert] = GLFW_KEY_INSERT;
     io.KeyMap[ImGuiKey_Delete] = GLFW_KEY_DELETE;
     io.KeyMap[ImGuiKey_Backspace] = GLFW_KEY_BACKSPACE;
     io.KeyMap[ImGuiKey_Space] = GLFW_KEY_SPACE;
     io.KeyMap[ImGuiKey_Enter] = GLFW_KEY_ENTER;
     io.KeyMap[ImGuiKey_Escape] = GLFW_KEY_ESCAPE;
     io.KeyMap[ImGuiKey_A] = GLFW_KEY_A;
     io.KeyMap[ImGuiKey_C] = GLFW_KEY_C;
     io.KeyMap[ImGuiKey_V] = GLFW_KEY_V;
     io.KeyMap[ImGuiKey_X] = GLFW_KEY_X;
     io.KeyMap[ImGuiKey_Y] = GLFW_KEY_Y;
     io.KeyMap[ImGuiKey_Z] = GLFW_KEY_Z;

     io.SetClipboardTextFn = ImGui_ImplGlfwGL2_SetClipboardText;
     io.GetClipboardTextFn = ImGui_ImplGlfwGL2_GetClipboardText;
     io.ClipboardUserData = g_Window;
 #ifdef _WIN32
     io.ImeWindowHandle = glfwGetWin32Window(g_Window);
 #endif

     // Load cursors
     // FIXME: GLFW doesn't expose suitable cursors for ResizeAll, ResizeNESW, ResizeNWSE. We revert to arrow cursor for those.
     g_MouseCursors[ImGuiMouseCursor_Arrow] = glfwCreateStandardCursor(GLFW_ARROW_CURSOR);
     g_MouseCursors[ImGuiMouseCursor_TextInput] = glfwCreateStandardCursor(GLFW_IBEAM_CURSOR);
     g_MouseCursors[ImGuiMouseCursor_ResizeAll] = glfwCreateStandardCursor(GLFW_ARROW_CURSOR);
     g_MouseCursors[ImGuiMouseCursor_ResizeNS] = glfwCreateStandardCursor(GLFW_VRESIZE_CURSOR);
     g_MouseCursors[ImGuiMouseCursor_ResizeEW] = glfwCreateStandardCursor(GLFW_HRESIZE_CURSOR);
     g_MouseCursors[ImGuiMouseCursor_ResizeNESW] = glfwCreateStandardCursor(GLFW_ARROW_CURSOR);
     g_MouseCursors[ImGuiMouseCursor_ResizeNWSE] = glfwCreateStandardCursor(GLFW_ARROW_CURSOR);

     if (install_callbacks)
         ImGui_ImplGlfw_InstallCallbacks(window);

     return true;
 }

 void ImGui_ImplGlfwGL2_Shutdown()
 {
     // Destroy GLFW mouse cursors
     for (ImGuiMouseCursor cursor_n = 0; cursor_n < ImGuiMouseCursor_COUNT; cursor_n++)
         glfwDestroyCursor(g_MouseCursors[cursor_n]);
     memset(g_MouseCursors, 0, sizeof(g_MouseCursors));

     // Destroy OpenGL objects
     ImGui_ImplGlfwGL2_InvalidateDeviceObjects();
 }

 void ImGui_ImplGlfwGL2_NewFrame()
 {
     if (!g_FontTexture)
         ImGui_ImplGlfwGL2_CreateDeviceObjects();

     ImGuiIO& io = ImGui::GetIO();

     // Setup display size (every frame to accommodate for window resizing)
     int w, h;
     int display_w, display_h;
     glfwGetWindowSize(g_Window, &w, &h);
     glfwGetFramebufferSize(g_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
     double current_time =  glfwGetTime();
     io.DeltaTime = g_Time > 0.0 ? (float)(current_time - g_Time) : (float)(1.0f/60.0f);
     g_Time = current_time;

     // Setup inputs
     // (we already got mouse wheel, keyboard keys & characters from glfw callbacks polled in glfwPollEvents())
     if (glfwGetWindowAttrib(g_Window, GLFW_FOCUSED))
     {
         // Set OS mouse position if requested (only used when ImGuiConfigFlags_NavEnableSetMousePos is enabled by user)
         if (io.WantSetMousePos)
         {
             glfwSetCursorPos(g_Window, (double)io.MousePos.x, (double)io.MousePos.y);
         }
         else
         {
             double mouse_x, mouse_y;
             glfwGetCursorPos(g_Window, &mouse_x, &mouse_y);
             io.MousePos = ImVec2((float)mouse_x, (float)mouse_y);
         }
     }
     else
     {
         io.MousePos = ImVec2(-FLT_MAX,-FLT_MAX);
     }

     for (int i = 0; i < 3; i++)
     {
         // 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[i] = g_MouseJustPressed[i] || glfwGetMouseButton(g_Window, i) != 0;
         g_MouseJustPressed[i] = false;
     }

     // Update OS/hardware mouse cursor if imgui isn't drawing a software cursor
     if ((io.ConfigFlags & ImGuiConfigFlags_NoMouseCursorChange) == 0 && glfwGetInputMode(g_Window, GLFW_CURSOR) != GLFW_CURSOR_DISABLED)
     {
         ImGuiMouseCursor cursor = ImGui::GetMouseCursor();
         if (io.MouseDrawCursor || cursor == ImGuiMouseCursor_None)
         {
             glfwSetInputMode(g_Window, GLFW_CURSOR, GLFW_CURSOR_HIDDEN);
         }
         else
         {
             glfwSetCursor(g_Window, g_MouseCursors[cursor] ? g_MouseCursors[cursor] : g_MouseCursors[ImGuiMouseCursor_Arrow]);
             glfwSetInputMode(g_Window, GLFW_CURSOR, GLFW_CURSOR_NORMAL);
         }
     }

     // 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 GLFW binding with OpenGL (legacy, fixed pipeline)
	// (GLFW 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.

	// DO NOT USE THIS CODE IF YOUR CODE/ENGINE IS USING MODERN OPENGL (SHADERS, VBO, VAO, etc.)
	// Prefer using the code in the 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)
	// 2018-03-20: Misc: Setup io.BackendFlags ImGuiBackendFlags_HasMouseCursors and ImGuiBackendFlags_HasSetMousePos flags + honor ImGuiConfigFlags_NoMouseCursorChange flag.
	// 2018-02-20: Inputs: Added support for mouse cursors (ImGui::GetMouseCursor() value, passed to glfwSetCursor()).
	// 2018-02-20: Inputs: Renamed GLFW callbacks exposed in .h to not include GL2 in their name.
	// 2018-02-16: Misc: Obsoleted the io.RenderDrawListsFn callback and exposed ImGui_ImplGlfwGL2_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.
	// 2018-02-06: Inputs: Honoring the io.WantSetMousePos flag by repositioning the mouse (ImGuiConfigFlags_NavEnableSetMousePos is set).
	// 2018-01-20: Inputs: Added Horizontal Mouse Wheel support.
	// 2018-01-18: Inputs: Added mapping for ImGuiKey_Insert.
	// 2018-01-09: Misc: Renamed imgui_impl_glfw.* to imgui_impl_glfw_gl2.*.
	// 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.
	// 2016-09-10: OpenGL: Uploading font texture as RGBA32 to increase compatibility with users shaders (not ideal).
	// 2016-09-05: OpenGL: Fixed save and restore of current scissor rectangle.

	#include "imgui.h"
	#include "imgui_impl_glfw_gl2.h"

	// GLFW
	#include <GLFW/glfw3.h>
	#ifdef _WIN32
	#undef APIENTRY
	#define GLFW_EXPOSE_NATIVE_WIN32
	#define GLFW_EXPOSE_NATIVE_WGL
	#include <GLFW/glfw3native.h>
	#endif

	// GLFW data
	static GLFWwindow* g_Window = NULL;
	static double g_Time = 0.0f;
	static bool g_MouseJustPressed[3] = { false, false, false };
	static GLFWcursor* g_MouseCursors[ImGuiMouseCursor_COUNT] = { 0 };

	// OpenGL data
	static GLuint g_FontTexture = 0;

	// 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_ImplGlfwGL2_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_ImplGlfwGL2_GetClipboardText(void* user_data)
	{
	return glfwGetClipboardString((GLFWwindow*)user_data);
	}

	static void ImGui_ImplGlfwGL2_SetClipboardText(void* user_data, const char* text)
	{
	glfwSetClipboardString((GLFWwindow*)user_data, text);
	}

	void ImGui_ImplGlfw_MouseButtonCallback(GLFWwindow, int button, int action, int /mods*/)
	{
	if (action == GLFW_PRESS && button >= 0 && button < 3)
	g_MouseJustPressed[button] = true;
	}

	void ImGui_ImplGlfw_ScrollCallback(GLFWwindow*, double xoffset, double yoffset)
	{
	ImGuiIO& io = ImGui::GetIO();
	io.MouseWheelH += (float)xoffset;
	io.MouseWheel += (float)yoffset;
	}

	void ImGui_ImplGlfw_KeyCallback(GLFWwindow*, int key, int, int action, int mods)
	{
	ImGuiIO& io = ImGui::GetIO();
	if (action == GLFW_PRESS)
	io.KeysDown[key] = true;
	if (action == GLFW_RELEASE)
	io.KeysDown[key] = false;

	(void)mods; // Modifiers are not reliable across systems
	io.KeyCtrl = io.KeysDown[GLFW_KEY_LEFT_CONTROL] \|\| io.KeysDown[GLFW_KEY_RIGHT_CONTROL];
	io.KeyShift = io.KeysDown[GLFW_KEY_LEFT_SHIFT] \|\| io.KeysDown[GLFW_KEY_RIGHT_SHIFT];
	io.KeyAlt = io.KeysDown[GLFW_KEY_LEFT_ALT] \|\| io.KeysDown[GLFW_KEY_RIGHT_ALT];
	io.KeySuper = io.KeysDown[GLFW_KEY_LEFT_SUPER] \|\| io.KeysDown[GLFW_KEY_RIGHT_SUPER];
	}

	void ImGui_ImplGlfw_CharCallback(GLFWwindow*, unsigned int c)
	{
	ImGuiIO& io = ImGui::GetIO();
	if (c > 0 && c < 0x10000)
	io.AddInputCharacter((unsigned short)c);
	}

	bool ImGui_ImplGlfwGL2_CreateDeviceObjects()
	{
	// Build texture atlas
	ImGuiIO& io = ImGui::GetIO();
	unsigned char* pixels;
	int width, height;
	io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height); // Load as RGBA 32-bits (75% of the memory is wasted, but default font is so small) because it is more likely to be compatible with user's existing shaders. If your ImTextureId represent a higher-level concept than just a GL texture id, consider calling GetTexDataAsAlpha8() instead to save on GPU memory.

	// 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_RGBA, width, height, 0, GL_RGBA, 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_ImplGlfwGL2_InvalidateDeviceObjects()
	{
	if (g_FontTexture)
	{
	glDeleteTextures(1, &g_FontTexture);
	ImGui::GetIO().Fonts->TexID = 0;
	g_FontTexture = 0;
	}
	}

	static void ImGui_ImplGlfw_InstallCallbacks(GLFWwindow* window)
	{
	glfwSetMouseButtonCallback(window, ImGui_ImplGlfw_MouseButtonCallback);
	glfwSetScrollCallback(window, ImGui_ImplGlfw_ScrollCallback);
	glfwSetKeyCallback(window, ImGui_ImplGlfw_KeyCallback);
	glfwSetCharCallback(window, ImGui_ImplGlfw_CharCallback);
	}

	bool ImGui_ImplGlfwGL2_Init(GLFWwindow* window, bool install_callbacks)
	{
	g_Window = window;

	// Setup back-end capabilities flags
	ImGuiIO& io = ImGui::GetIO();
	io.BackendFlags \|= ImGuiBackendFlags_HasMouseCursors; // We can honor GetMouseCursor() values (optional)
	io.BackendFlags \|= ImGuiBackendFlags_HasSetMousePos; // We can honor io.WantSetMousePos requests (optional, rarely used)

	// Keyboard mapping. ImGui will use those indices to peek into the io.KeysDown[] array.
	io.KeyMap[ImGuiKey_Tab] = GLFW_KEY_TAB;
	io.KeyMap[ImGuiKey_LeftArrow] = GLFW_KEY_LEFT;
	io.KeyMap[ImGuiKey_RightArrow] = GLFW_KEY_RIGHT;
	io.KeyMap[ImGuiKey_UpArrow] = GLFW_KEY_UP;
	io.KeyMap[ImGuiKey_DownArrow] = GLFW_KEY_DOWN;
	io.KeyMap[ImGuiKey_PageUp] = GLFW_KEY_PAGE_UP;
	io.KeyMap[ImGuiKey_PageDown] = GLFW_KEY_PAGE_DOWN;
	io.KeyMap[ImGuiKey_Home] = GLFW_KEY_HOME;
	io.KeyMap[ImGuiKey_End] = GLFW_KEY_END;
	io.KeyMap[ImGuiKey_Insert] = GLFW_KEY_INSERT;
	io.KeyMap[ImGuiKey_Delete] = GLFW_KEY_DELETE;
	io.KeyMap[ImGuiKey_Backspace] = GLFW_KEY_BACKSPACE;
	io.KeyMap[ImGuiKey_Space] = GLFW_KEY_SPACE;
	io.KeyMap[ImGuiKey_Enter] = GLFW_KEY_ENTER;
	io.KeyMap[ImGuiKey_Escape] = GLFW_KEY_ESCAPE;
	io.KeyMap[ImGuiKey_A] = GLFW_KEY_A;
	io.KeyMap[ImGuiKey_C] = GLFW_KEY_C;
	io.KeyMap[ImGuiKey_V] = GLFW_KEY_V;
	io.KeyMap[ImGuiKey_X] = GLFW_KEY_X;
	io.KeyMap[ImGuiKey_Y] = GLFW_KEY_Y;
	io.KeyMap[ImGuiKey_Z] = GLFW_KEY_Z;

	io.SetClipboardTextFn = ImGui_ImplGlfwGL2_SetClipboardText;
	io.GetClipboardTextFn = ImGui_ImplGlfwGL2_GetClipboardText;
	io.ClipboardUserData = g_Window;
	#ifdef _WIN32
	io.ImeWindowHandle = glfwGetWin32Window(g_Window);
	#endif

	// Load cursors
	// FIXME: GLFW doesn't expose suitable cursors for ResizeAll, ResizeNESW, ResizeNWSE. We revert to arrow cursor for those.
	g_MouseCursors[ImGuiMouseCursor_Arrow] = glfwCreateStandardCursor(GLFW_ARROW_CURSOR);
	g_MouseCursors[ImGuiMouseCursor_TextInput] = glfwCreateStandardCursor(GLFW_IBEAM_CURSOR);
	g_MouseCursors[ImGuiMouseCursor_ResizeAll] = glfwCreateStandardCursor(GLFW_ARROW_CURSOR);
	g_MouseCursors[ImGuiMouseCursor_ResizeNS] = glfwCreateStandardCursor(GLFW_VRESIZE_CURSOR);
	g_MouseCursors[ImGuiMouseCursor_ResizeEW] = glfwCreateStandardCursor(GLFW_HRESIZE_CURSOR);
	g_MouseCursors[ImGuiMouseCursor_ResizeNESW] = glfwCreateStandardCursor(GLFW_ARROW_CURSOR);
	g_MouseCursors[ImGuiMouseCursor_ResizeNWSE] = glfwCreateStandardCursor(GLFW_ARROW_CURSOR);

	if (install_callbacks)
	ImGui_ImplGlfw_InstallCallbacks(window);

	return true;
	}

	void ImGui_ImplGlfwGL2_Shutdown()
	{
	// Destroy GLFW mouse cursors
	for (ImGuiMouseCursor cursor_n = 0; cursor_n < ImGuiMouseCursor_COUNT; cursor_n++)
	glfwDestroyCursor(g_MouseCursors[cursor_n]);
	memset(g_MouseCursors, 0, sizeof(g_MouseCursors));

	// Destroy OpenGL objects
	ImGui_ImplGlfwGL2_InvalidateDeviceObjects();
	}

	void ImGui_ImplGlfwGL2_NewFrame()
	{
	if (!g_FontTexture)
	ImGui_ImplGlfwGL2_CreateDeviceObjects();

	ImGuiIO& io = ImGui::GetIO();

	// Setup display size (every frame to accommodate for window resizing)
	int w, h;
	int display_w, display_h;
	glfwGetWindowSize(g_Window, &w, &h);
	glfwGetFramebufferSize(g_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
	double current_time = glfwGetTime();
	io.DeltaTime = g_Time > 0.0 ? (float)(current_time - g_Time) : (float)(1.0f/60.0f);
	g_Time = current_time;

	// Setup inputs
	// (we already got mouse wheel, keyboard keys & characters from glfw callbacks polled in glfwPollEvents())
	if (glfwGetWindowAttrib(g_Window, GLFW_FOCUSED))
	{
	// Set OS mouse position if requested (only used when ImGuiConfigFlags_NavEnableSetMousePos is enabled by user)
	if (io.WantSetMousePos)
	{
	glfwSetCursorPos(g_Window, (double)io.MousePos.x, (double)io.MousePos.y);
	}
	else
	{
	double mouse_x, mouse_y;
	glfwGetCursorPos(g_Window, &mouse_x, &mouse_y);
	io.MousePos = ImVec2((float)mouse_x, (float)mouse_y);
	}
	}
	else
	{
	io.MousePos = ImVec2(-FLT_MAX,-FLT_MAX);
	}

	for (int i = 0; i < 3; i++)
	{
	// 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[i] = g_MouseJustPressed[i] \|\| glfwGetMouseButton(g_Window, i) != 0;
	g_MouseJustPressed[i] = false;
	}

	// Update OS/hardware mouse cursor if imgui isn't drawing a software cursor
	if ((io.ConfigFlags & ImGuiConfigFlags_NoMouseCursorChange) == 0 && glfwGetInputMode(g_Window, GLFW_CURSOR) != GLFW_CURSOR_DISABLED)
	{
	ImGuiMouseCursor cursor = ImGui::GetMouseCursor();
	if (io.MouseDrawCursor \|\| cursor == ImGuiMouseCursor_None)
	{
	glfwSetInputMode(g_Window, GLFW_CURSOR, GLFW_CURSOR_HIDDEN);
	}
	else
	{
	glfwSetCursor(g_Window, g_MouseCursors[cursor] ? g_MouseCursors[cursor] : g_MouseCursors[ImGuiMouseCursor_Arrow]);
	glfwSetInputMode(g_Window, GLFW_CURSOR, GLFW_CURSOR_NORMAL);
	}
	}

	// 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();
	}