examples/opengl_example/imgui_impl_glfw.cpp - external/github.com/ocornut/imgui - Git at Google

 // ImGui GLFW binding with OpenGL
 // https://github.com/ocornut/imgui

 #include <imgui.h>
 #include "imgui_impl_glfw.h"

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

 // Data
 static GLFWwindow*  g_Window = NULL;
 static double       g_Time = 0.0f;
 static bool         g_MousePressed[3] = { false, false, false };
 static float        g_MouseWheel = 0.0f;
 static GLuint       g_FontTexture = 0;

 // This is the main rendering function that you have to implement and provide to ImGui (via setting up 'RenderDrawListsFn' in the ImGuiIO structure)
 // If text or lines are blurry when integrating ImGui in your engine:
 // - in your Render function, try translating your projection matrix by (0.5f,0.5f) or (0.375f,0.375f)
 static void ImGui_ImplGlfw_RenderDrawLists(ImDrawList** const cmd_lists, int cmd_lists_count)
 {
     if (cmd_lists_count == 0)
         return;

     // We are using the OpenGL fixed pipeline to make the example code simpler to read!
     // A probable faster way to render would be to collate all vertices from all cmd_lists into a single vertex buffer.
     // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled, vertex/texcoord/color pointers.
     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);

     // Setup orthographic projection matrix
     const float width = ImGui::GetIO().DisplaySize.x;
     const float height = ImGui::GetIO().DisplaySize.y;
     glMatrixMode(GL_PROJECTION);
     glPushMatrix();
     glLoadIdentity();
     glOrtho(0.0f, width, height, 0.0f, -1.0f, +1.0f);
     glMatrixMode(GL_MODELVIEW);
     glPushMatrix();
     glLoadIdentity();

     // Render command lists
     #define OFFSETOF(TYPE, ELEMENT) ((size_t)&(((TYPE *)0)->ELEMENT))
     for (int n = 0; n < cmd_lists_count; n++)
     {
         const ImDrawList* cmd_list = cmd_lists[n];
         const unsigned char* vtx_buffer = (const unsigned char*)&cmd_list->vtx_buffer.front();
         glVertexPointer(2, GL_FLOAT, sizeof(ImDrawVert), (void*)(vtx_buffer + OFFSETOF(ImDrawVert, pos)));
         glTexCoordPointer(2, GL_FLOAT, sizeof(ImDrawVert), (void*)(vtx_buffer + OFFSETOF(ImDrawVert, uv)));
         glColorPointer(4, GL_UNSIGNED_BYTE, sizeof(ImDrawVert), (void*)(vtx_buffer + OFFSETOF(ImDrawVert, col)));

         int vtx_offset = 0;
         for (size_t cmd_i = 0; cmd_i < cmd_list->commands.size(); cmd_i++)
         {
             const ImDrawCmd* pcmd = &cmd_list->commands[cmd_i];
             if (pcmd->user_callback)
             {
                 pcmd->user_callback(cmd_list, pcmd);
             }
             else
             {
                 glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->texture_id);
                 glScissor((int)pcmd->clip_rect.x, (int)(height - pcmd->clip_rect.w), (int)(pcmd->clip_rect.z - pcmd->clip_rect.x), (int)(pcmd->clip_rect.w - pcmd->clip_rect.y));
                 glDrawArrays(GL_TRIANGLES, vtx_offset, pcmd->vtx_count);
             }
             vtx_offset += pcmd->vtx_count;
         }
     }
     #undef OFFSETOF

     // Restore modified state
     glDisableClientState(GL_COLOR_ARRAY);
     glDisableClientState(GL_TEXTURE_COORD_ARRAY);
     glDisableClientState(GL_VERTEX_ARRAY);
     glMatrixMode(GL_MODELVIEW);
     glPopMatrix();
     glMatrixMode(GL_PROJECTION);
     glPopMatrix();
     glPopAttrib();
 }

 static const char* ImGui_ImplGlfw_GetClipboardText()
 {
     return glfwGetClipboardString(g_Window);
 }

 static void ImGui_ImplGlfw_SetClipboardText(const char* text)
 {
     glfwSetClipboardString(g_Window, text);
 }

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

 void ImGui_ImplGlfw_ScrollCallback(GLFWwindow* window, double xoffset, double yoffset)
 {
     g_MouseWheel += (float)yoffset; // Use fractional mouse wheel, 1.0 unit 5 lines.
 }

 void ImGui_ImplGlFw_KeyCallback(GLFWwindow* window, int key, int scancode, int action, int mods)
 {
     ImGuiIO& io = ImGui::GetIO();
     if (action == GLFW_PRESS)
         io.KeysDown[key] = true;
     if (action == GLFW_RELEASE)
         io.KeysDown[key] = false;
     io.KeyCtrl = (mods & GLFW_MOD_CONTROL) != 0;
     io.KeyShift = (mods & GLFW_MOD_SHIFT) != 0;
 }

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

 bool ImGui_ImplGlfw_CreateDeviceObjects()
 {
     ImGuiIO& io = ImGui::GetIO();

     // Build texture
     unsigned char* pixels;
     int width, height;
     io.Fonts->GetTexDataAsAlpha8(&pixels, &width, &height);

     // Create 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);
     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;

     return true;
 }

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

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

     ImGuiIO& io = ImGui::GetIO();
     io.KeyMap[ImGuiKey_Tab] = GLFW_KEY_TAB;                 // Keyboard mapping. ImGui will use those indices to peek into the io.KeyDown[] array.
     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_Home] = GLFW_KEY_HOME;
     io.KeyMap[ImGuiKey_End] = GLFW_KEY_END;
     io.KeyMap[ImGuiKey_Delete] = GLFW_KEY_DELETE;
     io.KeyMap[ImGuiKey_Backspace] = GLFW_KEY_BACKSPACE;
     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.RenderDrawListsFn = ImGui_ImplGlfw_RenderDrawLists;
     io.SetClipboardTextFn = ImGui_ImplGlfw_SetClipboardText;
     io.GetClipboardTextFn = ImGui_ImplGlfw_GetClipboardText;
 #ifdef _MSC_VER
     io.ImeWindowHandle = glfwGetWin32Window(g_Window);
 #endif

     if (install_callbacks)
     {
         glfwSetMouseButtonCallback(window, ImGui_ImplGlfw_MouseButtonCallback);
         glfwSetScrollCallback(window, ImGui_ImplGlfw_ScrollCallback);
         glfwSetKeyCallback(window, ImGui_ImplGlFw_KeyCallback);
         glfwSetCharCallback(window, ImGui_ImplGlfw_CharCallback);
     }

     return true;
 }

 void ImGui_ImplGlfw_Shutdown()
 {
     ImGui_ImplGlfw_InvalidateDeviceObjects();
     ImGui::Shutdown();
 }

 void ImGui_ImplGlfw_NewFrame()
 {
     if (!g_FontTexture)
         ImGui_ImplGlfw_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)display_w, (float)display_h);

     // 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())
     double mouse_x, mouse_y;
     glfwGetCursorPos(g_Window, &mouse_x, &mouse_y);
     mouse_x *= (float)display_w / w;                                                    // Convert mouse coordinates to pixels
     mouse_y *= (float)display_h / h;
     io.MousePos = ImVec2((float)mouse_x, (float)mouse_y);                               // Mouse position, in pixels (set to -1,-1 if no mouse / on another screen, etc.)

     for (int i = 0; i < 3; i++)
     {
         io.MouseDown[i] = g_MousePressed[i] || glfwGetMouseButton(g_Window, i) != 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.
         g_MousePressed[i] = false;
     }

     io.MouseWheel = g_MouseWheel;
     g_MouseWheel = 0.0f;

     // Start the frame
     ImGui::NewFrame();
 }
	// ImGui GLFW binding with OpenGL
	// https://github.com/ocornut/imgui

	#include <imgui.h>
	#include "imgui_impl_glfw.h"

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

	// Data
	static GLFWwindow* g_Window = NULL;
	static double g_Time = 0.0f;
	static bool g_MousePressed[3] = { false, false, false };
	static float g_MouseWheel = 0.0f;
	static GLuint g_FontTexture = 0;

	// This is the main rendering function that you have to implement and provide to ImGui (via setting up 'RenderDrawListsFn' in the ImGuiIO structure)
	// If text or lines are blurry when integrating ImGui in your engine:
	// - in your Render function, try translating your projection matrix by (0.5f,0.5f) or (0.375f,0.375f)
	static void ImGui_ImplGlfw_RenderDrawLists(ImDrawList** const cmd_lists, int cmd_lists_count)
	{
	if (cmd_lists_count == 0)
	return;

	// We are using the OpenGL fixed pipeline to make the example code simpler to read!
	// A probable faster way to render would be to collate all vertices from all cmd_lists into a single vertex buffer.
	// Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled, vertex/texcoord/color pointers.
	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);

	// Setup orthographic projection matrix
	const float width = ImGui::GetIO().DisplaySize.x;
	const float height = ImGui::GetIO().DisplaySize.y;
	glMatrixMode(GL_PROJECTION);
	glPushMatrix();
	glLoadIdentity();
	glOrtho(0.0f, width, height, 0.0f, -1.0f, +1.0f);
	glMatrixMode(GL_MODELVIEW);
	glPushMatrix();
	glLoadIdentity();

	// Render command lists
	#define OFFSETOF(TYPE, ELEMENT) ((size_t)&(((TYPE *)0)->ELEMENT))
	for (int n = 0; n < cmd_lists_count; n++)
	{
	const ImDrawList* cmd_list = cmd_lists[n];
	const unsigned char* vtx_buffer = (const unsigned char*)&cmd_list->vtx_buffer.front();
	glVertexPointer(2, GL_FLOAT, sizeof(ImDrawVert), (void*)(vtx_buffer + OFFSETOF(ImDrawVert, pos)));
	glTexCoordPointer(2, GL_FLOAT, sizeof(ImDrawVert), (void*)(vtx_buffer + OFFSETOF(ImDrawVert, uv)));
	glColorPointer(4, GL_UNSIGNED_BYTE, sizeof(ImDrawVert), (void*)(vtx_buffer + OFFSETOF(ImDrawVert, col)));

	int vtx_offset = 0;
	for (size_t cmd_i = 0; cmd_i < cmd_list->commands.size(); cmd_i++)
	{
	const ImDrawCmd* pcmd = &cmd_list->commands[cmd_i];
	if (pcmd->user_callback)
	{
	pcmd->user_callback(cmd_list, pcmd);
	}
	else
	{
	glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->texture_id);
	glScissor((int)pcmd->clip_rect.x, (int)(height - pcmd->clip_rect.w), (int)(pcmd->clip_rect.z - pcmd->clip_rect.x), (int)(pcmd->clip_rect.w - pcmd->clip_rect.y));
	glDrawArrays(GL_TRIANGLES, vtx_offset, pcmd->vtx_count);
	}
	vtx_offset += pcmd->vtx_count;
	}
	}
	#undef OFFSETOF

	// Restore modified state
	glDisableClientState(GL_COLOR_ARRAY);
	glDisableClientState(GL_TEXTURE_COORD_ARRAY);
	glDisableClientState(GL_VERTEX_ARRAY);
	glMatrixMode(GL_MODELVIEW);
	glPopMatrix();
	glMatrixMode(GL_PROJECTION);
	glPopMatrix();
	glPopAttrib();
	}

	static const char* ImGui_ImplGlfw_GetClipboardText()
	{
	return glfwGetClipboardString(g_Window);
	}

	static void ImGui_ImplGlfw_SetClipboardText(const char* text)
	{
	glfwSetClipboardString(g_Window, text);
	}

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

	void ImGui_ImplGlfw_ScrollCallback(GLFWwindow* window, double xoffset, double yoffset)
	{
	g_MouseWheel += (float)yoffset; // Use fractional mouse wheel, 1.0 unit 5 lines.
	}

	void ImGui_ImplGlFw_KeyCallback(GLFWwindow* window, int key, int scancode, int action, int mods)
	{
	ImGuiIO& io = ImGui::GetIO();
	if (action == GLFW_PRESS)
	io.KeysDown[key] = true;
	if (action == GLFW_RELEASE)
	io.KeysDown[key] = false;
	io.KeyCtrl = (mods & GLFW_MOD_CONTROL) != 0;
	io.KeyShift = (mods & GLFW_MOD_SHIFT) != 0;
	}

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

	bool ImGui_ImplGlfw_CreateDeviceObjects()
	{
	ImGuiIO& io = ImGui::GetIO();

	// Build texture
	unsigned char* pixels;
	int width, height;
	io.Fonts->GetTexDataAsAlpha8(&pixels, &width, &height);

	// Create 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);
	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;

	return true;
	}

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

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

	ImGuiIO& io = ImGui::GetIO();
	io.KeyMap[ImGuiKey_Tab] = GLFW_KEY_TAB; // Keyboard mapping. ImGui will use those indices to peek into the io.KeyDown[] array.
	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_Home] = GLFW_KEY_HOME;
	io.KeyMap[ImGuiKey_End] = GLFW_KEY_END;
	io.KeyMap[ImGuiKey_Delete] = GLFW_KEY_DELETE;
	io.KeyMap[ImGuiKey_Backspace] = GLFW_KEY_BACKSPACE;
	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.RenderDrawListsFn = ImGui_ImplGlfw_RenderDrawLists;
	io.SetClipboardTextFn = ImGui_ImplGlfw_SetClipboardText;
	io.GetClipboardTextFn = ImGui_ImplGlfw_GetClipboardText;
	#ifdef _MSC_VER
	io.ImeWindowHandle = glfwGetWin32Window(g_Window);
	#endif

	if (install_callbacks)
	{
	glfwSetMouseButtonCallback(window, ImGui_ImplGlfw_MouseButtonCallback);
	glfwSetScrollCallback(window, ImGui_ImplGlfw_ScrollCallback);
	glfwSetKeyCallback(window, ImGui_ImplGlFw_KeyCallback);
	glfwSetCharCallback(window, ImGui_ImplGlfw_CharCallback);
	}

	return true;
	}

	void ImGui_ImplGlfw_Shutdown()
	{
	ImGui_ImplGlfw_InvalidateDeviceObjects();
	ImGui::Shutdown();
	}

	void ImGui_ImplGlfw_NewFrame()
	{
	if (!g_FontTexture)
	ImGui_ImplGlfw_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)display_w, (float)display_h);

	// 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())
	double mouse_x, mouse_y;
	glfwGetCursorPos(g_Window, &mouse_x, &mouse_y);
	mouse_x *= (float)display_w / w; // Convert mouse coordinates to pixels
	mouse_y *= (float)display_h / h;
	io.MousePos = ImVec2((float)mouse_x, (float)mouse_y); // Mouse position, in pixels (set to -1,-1 if no mouse / on another screen, etc.)

	for (int i = 0; i < 3; i++)
	{
	io.MouseDown[i] = g_MousePressed[i] \|\| glfwGetMouseButton(g_Window, i) != 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.
	g_MousePressed[i] = false;
	}

	io.MouseWheel = g_MouseWheel;
	g_MouseWheel = 0.0f;

	// Start the frame
	ImGui::NewFrame();
	}