examples/opengl3_example/main.cpp - external/github.com/ocornut/imgui - Git at Google

 // ImGui - standalone example application for OpenGL 3, using programmable pipeline

 #ifdef _MSC_VER
 #pragma warning (disable: 4996)                        // 'This function or variable may be unsafe': strcpy, strdup, sprintf, vsnprintf, sscanf, fopen
 #endif
 #ifdef __clang__
 #pragma clang diagnostic ignored "-Wunused-function"   // warning: unused function
 #endif

 #include "../../imgui.h"
 #include <stdio.h>

 // Glfw/Glew
 #define GLEW_STATIC
 #include <GL/glew.h>
 #include <GLFW/glfw3.h>
 #define OFFSETOF(TYPE, ELEMENT) ((size_t)&(((TYPE *)0)->ELEMENT))

 static GLFWwindow* window;
 static bool mousePressed[2] = { false, false };

 // Shader variables
 static int shader_handle, vert_handle, frag_handle;
 static int texture_location, proj_mtx_location;
 static int position_location, uv_location, colour_location;
 static size_t vbo_max_size = 20000;
 static unsigned int vbo_handle, vao_handle;

 // 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 ImImpl_RenderDrawLists(ImDrawList** const cmd_lists, int cmd_lists_count)
 {
     if (cmd_lists_count == 0)
         return;

     // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled
     glEnable(GL_BLEND);
     glBlendEquation(GL_FUNC_ADD);
     glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
     glDisable(GL_CULL_FACE);
     glDisable(GL_DEPTH_TEST);
     glEnable(GL_SCISSOR_TEST);
     glActiveTexture(GL_TEXTURE0);

     // Setup orthographic projection matrix
     const float width = ImGui::GetIO().DisplaySize.x;
     const float height = ImGui::GetIO().DisplaySize.y;
     const float ortho_projection[4][4] =
     {
         { 2.0f/width,	0.0f,			0.0f,		0.0f },
         { 0.0f,			2.0f/-height,	0.0f,		0.0f },
         { 0.0f,			0.0f,			-1.0f,		0.0f },
         { -1.0f,		1.0f,			0.0f,		1.0f },
     };
     glUseProgram(shader_handle);
     glUniform1i(texture_location, 0);
     glUniformMatrix4fv(proj_mtx_location, 1, GL_FALSE, &ortho_projection[0][0]);

     // Grow our buffer according to what we need
     size_t total_vtx_count = 0;
     for (int n = 0; n < cmd_lists_count; n++)
         total_vtx_count += cmd_lists[n]->vtx_buffer.size();
     glBindBuffer(GL_ARRAY_BUFFER, vbo_handle);
     size_t neededBufferSize = total_vtx_count * sizeof(ImDrawVert);
     if (neededBufferSize > vbo_max_size)
     {
         vbo_max_size = neededBufferSize + 5000;  // Grow buffer
         glBufferData(GL_ARRAY_BUFFER, vbo_max_size, NULL, GL_STREAM_DRAW);
     }

     // Copy and convert all vertices into a single contiguous buffer
     unsigned char* buffer_data = (unsigned char*)glMapBuffer(GL_ARRAY_BUFFER, GL_WRITE_ONLY);
     if (!buffer_data)
         return;
     for (int n = 0; n < cmd_lists_count; n++)
     {
         const ImDrawList* cmd_list = cmd_lists[n];
         memcpy(buffer_data, &cmd_list->vtx_buffer[0], cmd_list->vtx_buffer.size() * sizeof(ImDrawVert));
         buffer_data += cmd_list->vtx_buffer.size() * sizeof(ImDrawVert);
     }
     glUnmapBuffer(GL_ARRAY_BUFFER);
     glBindBuffer(GL_ARRAY_BUFFER, 0);
     glBindVertexArray(vao_handle);

     int cmd_offset = 0;
     for (int n = 0; n < cmd_lists_count; n++)
     {
         const ImDrawList* cmd_list = cmd_lists[n];
         int vtx_offset = cmd_offset;
         const ImDrawCmd* pcmd_end = cmd_list->commands.end();
         for (const ImDrawCmd* pcmd = cmd_list->commands.begin(); pcmd != pcmd_end; pcmd++)
         {
             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;
         }
         cmd_offset = vtx_offset;
     }

     // Restore modified state
     glBindVertexArray(0);
     glUseProgram(0);
     glDisable(GL_SCISSOR_TEST);
     glBindTexture(GL_TEXTURE_2D, 0);
 }

 static const char* ImImpl_GetClipboardTextFn()
 {
     return glfwGetClipboardString(window);
 }

 static void ImImpl_SetClipboardTextFn(const char* text)
 {
     glfwSetClipboardString(window, text);
 }

 // GLFW callbacks to get events
 static void glfw_error_callback(int error, const char* description)
 {
     fputs(description, stderr);
 }

 static void glfw_mouse_button_callback(GLFWwindow* window, int button, int action, int mods)
 {
     if (action == GLFW_PRESS && button >= 0 && button < 2)
         mousePressed[button] = true;
 }

 static void glfw_scroll_callback(GLFWwindow* window, double xoffset, double yoffset)
 {
     ImGuiIO& io = ImGui::GetIO();
     io.MouseWheel += (float)yoffset; // Use fractional mouse wheel, 1.0 unit 5 lines.
 }

 static void glfw_key_callback(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;
 }

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

 void InitGL()
 {
     glfwSetErrorCallback(glfw_error_callback);
     if (!glfwInit())
         exit(1);

     glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
     glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
     glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

     window = glfwCreateWindow(1280, 720, "ImGui OpenGL3 example", NULL, NULL);
     glfwMakeContextCurrent(window);
     glfwSetKeyCallback(window, glfw_key_callback);
     glfwSetMouseButtonCallback(window, glfw_mouse_button_callback);
     glfwSetScrollCallback(window, glfw_scroll_callback);
     glfwSetCharCallback(window, glfw_char_callback);

     glewExperimental = GL_TRUE;

     GLenum err = glewInit();
     if (GLEW_OK != err)
         fprintf(stderr, "Error: %s\n", glewGetErrorString(err));

     const GLchar *vertex_shader =
         "#version 330\n"
         "uniform mat4 ProjMtx;\n"
         "in vec2 Position;\n"
         "in vec2 UV;\n"
         "in vec4 Color;\n"
         "out vec2 Frag_UV;\n"
         "out vec4 Frag_Color;\n"
         "void main()\n"
         "{\n"
         "	Frag_UV = UV;\n"
         "	Frag_Color = Color;\n"
         "	gl_Position = ProjMtx * vec4(Position.xy,0,1);\n"
         "}\n";

     const GLchar* fragment_shader =
         "#version 330\n"
         "uniform sampler2D Texture;\n"
         "in vec2 Frag_UV;\n"
         "in vec4 Frag_Color;\n"
         "out vec4 Out_Color;\n"
         "void main()\n"
         "{\n"
         "	Out_Color = Frag_Color * texture( Texture, Frag_UV.st);\n"
         "}\n";

     shader_handle = glCreateProgram();
     vert_handle = glCreateShader(GL_VERTEX_SHADER);
     frag_handle = glCreateShader(GL_FRAGMENT_SHADER);
     glShaderSource(vert_handle, 1, &vertex_shader, 0);
     glShaderSource(frag_handle, 1, &fragment_shader, 0);
     glCompileShader(vert_handle);
     glCompileShader(frag_handle);
     glAttachShader(shader_handle, vert_handle);
     glAttachShader(shader_handle, frag_handle);
     glLinkProgram(shader_handle);

     texture_location = glGetUniformLocation(shader_handle, "Texture");
     proj_mtx_location = glGetUniformLocation(shader_handle, "ProjMtx");
     position_location = glGetAttribLocation(shader_handle, "Position");
     uv_location = glGetAttribLocation(shader_handle, "UV");
     colour_location = glGetAttribLocation(shader_handle, "Color");

     glGenBuffers(1, &vbo_handle);
     glBindBuffer(GL_ARRAY_BUFFER, vbo_handle);
     glBufferData(GL_ARRAY_BUFFER, vbo_max_size, NULL, GL_DYNAMIC_DRAW);

     glGenVertexArrays(1, &vao_handle);
     glBindVertexArray(vao_handle);
     glBindBuffer(GL_ARRAY_BUFFER, vbo_handle);
     glEnableVertexAttribArray(position_location);
     glEnableVertexAttribArray(uv_location);
     glEnableVertexAttribArray(colour_location);

     glVertexAttribPointer(position_location, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, pos));
     glVertexAttribPointer(uv_location, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, uv));
     glVertexAttribPointer(colour_location, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, col));
     glBindVertexArray(0);
     glBindBuffer(GL_ARRAY_BUFFER, 0);
 }

 void LoadFontsTexture()
 {
     ImGuiIO& io = ImGui::GetIO();
     //ImFont* my_font1 = io.Fonts->AddFontDefault();
     //ImFont* my_font2 = io.Fonts->AddFontFromFileTTF("extra_fonts/Karla-Regular.ttf", 15.0f);
     //ImFont* my_font3 = io.Fonts->AddFontFromFileTTF("extra_fonts/ProggyClean.ttf", 13.0f); my_font3->DisplayOffset.y += 1;
     //ImFont* my_font4 = io.Fonts->AddFontFromFileTTF("extra_fonts/ProggyTiny.ttf", 10.0f); my_font4->DisplayOffset.y += 1;
     //ImFont* my_font5 = io.Fonts->AddFontFromFileTTF("c:\\Windows\\Fonts\\ArialUni.ttf", 20.0f, io.Fonts->GetGlyphRangesJapanese());

     unsigned char* pixels;
     int width, height;
     io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);   // Load as RGBA 32-bits for OpenGL3 demo because it is more likely to be compatible with user's existing shader.

     GLuint tex_id;
     glGenTextures(1, &tex_id);
     glBindTexture(GL_TEXTURE_2D, tex_id);
     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_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels);

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

 void InitImGui()
 {
     ImGuiIO& io = ImGui::GetIO();
     io.DeltaTime = 1.0f / 60.0f;                                  // Time elapsed since last frame, in seconds (in this sample app we'll override this every frame because our timestep is variable)
     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 = ImImpl_RenderDrawLists;
     io.SetClipboardTextFn = ImImpl_SetClipboardTextFn;
     io.GetClipboardTextFn = ImImpl_GetClipboardTextFn;

     LoadFontsTexture();
 }

 void UpdateImGui()
 {
     ImGuiIO& io = ImGui::GetIO();

     // Setup resolution (every frame to accommodate for window resizing)
     int w, h;
     int display_w, display_h;
     glfwGetWindowSize(window, &w, &h);
     glfwGetFramebufferSize(window, &display_w, &display_h);
     io.DisplaySize = ImVec2((float)display_w, (float)display_h);                                   // Display size, in pixels. For clamping windows positions.

     // Setup time step
     static double time = 0.0f;
     const double current_time =  glfwGetTime();
     io.DeltaTime = (float)(current_time - time);
     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(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.)
     io.MouseDown[0] = mousePressed[0] || glfwGetMouseButton(window, GLFW_MOUSE_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] = mousePressed[1] || glfwGetMouseButton(window, GLFW_MOUSE_BUTTON_RIGHT) != 0;

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

 // Application code
 int main(int argc, char** argv)
 {
     InitGL();
     InitImGui();

     bool show_test_window = true;
     bool show_another_window = false;
     ImVec4 clear_col = ImColor(114, 144, 154);

     while (!glfwWindowShouldClose(window))
     {
         ImGuiIO& io = ImGui::GetIO();
         io.MouseWheel = 0;
         mousePressed[0] = mousePressed[1] = false;
         glfwPollEvents();
         UpdateImGui();

         // 1. Show a simple window
         // Tip: if we don't call ImGui::Begin()/ImGui::End() the widgets appears in a window automatically called "Debug"
         {
             static float f;
             ImGui::Text("Hello, world!");
             ImGui::SliderFloat("float", &f, 0.0f, 1.0f);
             ImGui::ColorEdit3("clear color", (float*)&clear_col);
             if (ImGui::Button("Test Window")) show_test_window ^= 1;
             if (ImGui::Button("Another Window")) show_another_window ^= 1;
             ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / ImGui::GetIO().Framerate, ImGui::GetIO().Framerate);
         }

         // 2. Show another simple window, this time using an explicit Begin/End pair
         if (show_another_window)
         {
             ImGui::Begin("Another Window", &show_another_window, ImVec2(200,100));
             ImGui::Text("Hello");
             ImGui::End();
         }

         // 3. Show the ImGui test window. Most of the sample code is in ImGui::ShowTestWindow()
         if (show_test_window)
         {
             ImGui::SetNextWindowPos(ImVec2(650, 20), ImGuiSetCondition_FirstUseEver);
             ImGui::ShowTestWindow(&show_test_window);
         }

         // Rendering
         glViewport(0, 0, (int)io.DisplaySize.x, (int)io.DisplaySize.y);
         glClearColor(clear_col.x, clear_col.y, clear_col.z, clear_col.w);
         glClear(GL_COLOR_BUFFER_BIT);
         ImGui::Render();
         glfwSwapBuffers(window);
     }

     // Cleanup
     if (vao_handle) glDeleteVertexArrays(1, &vao_handle);
     if (vbo_handle) glDeleteBuffers(1, &vbo_handle);
     glDetachShader(shader_handle, vert_handle);
     glDetachShader(shader_handle, frag_handle);
     glDeleteShader(vert_handle);
     glDeleteShader(frag_handle);
     glDeleteProgram(shader_handle);

     ImGui::Shutdown();
     glfwTerminate();

     return 0;
 }
	// ImGui - standalone example application for OpenGL 3, using programmable pipeline

	#ifdef _MSC_VER
	#pragma warning (disable: 4996) // 'This function or variable may be unsafe': strcpy, strdup, sprintf, vsnprintf, sscanf, fopen
	#endif
	#ifdef __clang__
	#pragma clang diagnostic ignored "-Wunused-function" // warning: unused function
	#endif

	#include "../../imgui.h"
	#include <stdio.h>

	// Glfw/Glew
	#define GLEW_STATIC
	#include <GL/glew.h>
	#include <GLFW/glfw3.h>
	#define OFFSETOF(TYPE, ELEMENT) ((size_t)&(((TYPE *)0)->ELEMENT))

	static GLFWwindow* window;
	static bool mousePressed[2] = { false, false };

	// Shader variables
	static int shader_handle, vert_handle, frag_handle;
	static int texture_location, proj_mtx_location;
	static int position_location, uv_location, colour_location;
	static size_t vbo_max_size = 20000;
	static unsigned int vbo_handle, vao_handle;

	// 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 ImImpl_RenderDrawLists(ImDrawList** const cmd_lists, int cmd_lists_count)
	{
	if (cmd_lists_count == 0)
	return;

	// Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled
	glEnable(GL_BLEND);
	glBlendEquation(GL_FUNC_ADD);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
	glDisable(GL_CULL_FACE);
	glDisable(GL_DEPTH_TEST);
	glEnable(GL_SCISSOR_TEST);
	glActiveTexture(GL_TEXTURE0);

	// Setup orthographic projection matrix
	const float width = ImGui::GetIO().DisplaySize.x;
	const float height = ImGui::GetIO().DisplaySize.y;
	const float ortho_projection[4][4] =
	{
	{ 2.0f/width, 0.0f, 0.0f, 0.0f },
	{ 0.0f, 2.0f/-height, 0.0f, 0.0f },
	{ 0.0f, 0.0f, -1.0f, 0.0f },
	{ -1.0f, 1.0f, 0.0f, 1.0f },
	};
	glUseProgram(shader_handle);
	glUniform1i(texture_location, 0);
	glUniformMatrix4fv(proj_mtx_location, 1, GL_FALSE, &ortho_projection[0][0]);

	// Grow our buffer according to what we need
	size_t total_vtx_count = 0;
	for (int n = 0; n < cmd_lists_count; n++)
	total_vtx_count += cmd_lists[n]->vtx_buffer.size();
	glBindBuffer(GL_ARRAY_BUFFER, vbo_handle);
	size_t neededBufferSize = total_vtx_count * sizeof(ImDrawVert);
	if (neededBufferSize > vbo_max_size)
	{
	vbo_max_size = neededBufferSize + 5000; // Grow buffer
	glBufferData(GL_ARRAY_BUFFER, vbo_max_size, NULL, GL_STREAM_DRAW);
	}

	// Copy and convert all vertices into a single contiguous buffer
	unsigned char* buffer_data = (unsigned char*)glMapBuffer(GL_ARRAY_BUFFER, GL_WRITE_ONLY);
	if (!buffer_data)
	return;
	for (int n = 0; n < cmd_lists_count; n++)
	{
	const ImDrawList* cmd_list = cmd_lists[n];
	memcpy(buffer_data, &cmd_list->vtx_buffer[0], cmd_list->vtx_buffer.size() * sizeof(ImDrawVert));
	buffer_data += cmd_list->vtx_buffer.size() * sizeof(ImDrawVert);
	}
	glUnmapBuffer(GL_ARRAY_BUFFER);
	glBindBuffer(GL_ARRAY_BUFFER, 0);
	glBindVertexArray(vao_handle);

	int cmd_offset = 0;
	for (int n = 0; n < cmd_lists_count; n++)
	{
	const ImDrawList* cmd_list = cmd_lists[n];
	int vtx_offset = cmd_offset;
	const ImDrawCmd* pcmd_end = cmd_list->commands.end();
	for (const ImDrawCmd* pcmd = cmd_list->commands.begin(); pcmd != pcmd_end; pcmd++)
	{
	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;
	}
	cmd_offset = vtx_offset;
	}

	// Restore modified state
	glBindVertexArray(0);
	glUseProgram(0);
	glDisable(GL_SCISSOR_TEST);
	glBindTexture(GL_TEXTURE_2D, 0);
	}

	static const char* ImImpl_GetClipboardTextFn()
	{
	return glfwGetClipboardString(window);
	}

	static void ImImpl_SetClipboardTextFn(const char* text)
	{
	glfwSetClipboardString(window, text);
	}

	// GLFW callbacks to get events
	static void glfw_error_callback(int error, const char* description)
	{
	fputs(description, stderr);
	}

	static void glfw_mouse_button_callback(GLFWwindow* window, int button, int action, int mods)
	{
	if (action == GLFW_PRESS && button >= 0 && button < 2)
	mousePressed[button] = true;
	}

	static void glfw_scroll_callback(GLFWwindow* window, double xoffset, double yoffset)
	{
	ImGuiIO& io = ImGui::GetIO();
	io.MouseWheel += (float)yoffset; // Use fractional mouse wheel, 1.0 unit 5 lines.
	}

	static void glfw_key_callback(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;
	}

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

	void InitGL()
	{
	glfwSetErrorCallback(glfw_error_callback);
	if (!glfwInit())
	exit(1);

	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

	window = glfwCreateWindow(1280, 720, "ImGui OpenGL3 example", NULL, NULL);
	glfwMakeContextCurrent(window);
	glfwSetKeyCallback(window, glfw_key_callback);
	glfwSetMouseButtonCallback(window, glfw_mouse_button_callback);
	glfwSetScrollCallback(window, glfw_scroll_callback);
	glfwSetCharCallback(window, glfw_char_callback);

	glewExperimental = GL_TRUE;

	GLenum err = glewInit();
	if (GLEW_OK != err)
	fprintf(stderr, "Error: %s\n", glewGetErrorString(err));

	const GLchar *vertex_shader =
	"#version 330\n"
	"uniform mat4 ProjMtx;\n"
	"in vec2 Position;\n"
	"in vec2 UV;\n"
	"in vec4 Color;\n"
	"out vec2 Frag_UV;\n"
	"out vec4 Frag_Color;\n"
	"void main()\n"
	"{\n"
	" Frag_UV = UV;\n"
	" Frag_Color = Color;\n"
	" gl_Position = ProjMtx * vec4(Position.xy,0,1);\n"
	"}\n";

	const GLchar* fragment_shader =
	"#version 330\n"
	"uniform sampler2D Texture;\n"
	"in vec2 Frag_UV;\n"
	"in vec4 Frag_Color;\n"
	"out vec4 Out_Color;\n"
	"void main()\n"
	"{\n"
	" Out_Color = Frag_Color * texture( Texture, Frag_UV.st);\n"
	"}\n";

	shader_handle = glCreateProgram();
	vert_handle = glCreateShader(GL_VERTEX_SHADER);
	frag_handle = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(vert_handle, 1, &vertex_shader, 0);
	glShaderSource(frag_handle, 1, &fragment_shader, 0);
	glCompileShader(vert_handle);
	glCompileShader(frag_handle);
	glAttachShader(shader_handle, vert_handle);
	glAttachShader(shader_handle, frag_handle);
	glLinkProgram(shader_handle);

	texture_location = glGetUniformLocation(shader_handle, "Texture");
	proj_mtx_location = glGetUniformLocation(shader_handle, "ProjMtx");
	position_location = glGetAttribLocation(shader_handle, "Position");
	uv_location = glGetAttribLocation(shader_handle, "UV");
	colour_location = glGetAttribLocation(shader_handle, "Color");

	glGenBuffers(1, &vbo_handle);
	glBindBuffer(GL_ARRAY_BUFFER, vbo_handle);
	glBufferData(GL_ARRAY_BUFFER, vbo_max_size, NULL, GL_DYNAMIC_DRAW);

	glGenVertexArrays(1, &vao_handle);
	glBindVertexArray(vao_handle);
	glBindBuffer(GL_ARRAY_BUFFER, vbo_handle);
	glEnableVertexAttribArray(position_location);
	glEnableVertexAttribArray(uv_location);
	glEnableVertexAttribArray(colour_location);

	glVertexAttribPointer(position_location, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, pos));
	glVertexAttribPointer(uv_location, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, uv));
	glVertexAttribPointer(colour_location, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, col));
	glBindVertexArray(0);
	glBindBuffer(GL_ARRAY_BUFFER, 0);
	}

	void LoadFontsTexture()
	{
	ImGuiIO& io = ImGui::GetIO();
	//ImFont* my_font1 = io.Fonts->AddFontDefault();
	//ImFont* my_font2 = io.Fonts->AddFontFromFileTTF("extra_fonts/Karla-Regular.ttf", 15.0f);
	//ImFont* my_font3 = io.Fonts->AddFontFromFileTTF("extra_fonts/ProggyClean.ttf", 13.0f); my_font3->DisplayOffset.y += 1;
	//ImFont* my_font4 = io.Fonts->AddFontFromFileTTF("extra_fonts/ProggyTiny.ttf", 10.0f); my_font4->DisplayOffset.y += 1;
	//ImFont* my_font5 = io.Fonts->AddFontFromFileTTF("c:\\Windows\\Fonts\\ArialUni.ttf", 20.0f, io.Fonts->GetGlyphRangesJapanese());

	unsigned char* pixels;
	int width, height;
	io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height); // Load as RGBA 32-bits for OpenGL3 demo because it is more likely to be compatible with user's existing shader.

	GLuint tex_id;
	glGenTextures(1, &tex_id);
	glBindTexture(GL_TEXTURE_2D, tex_id);
	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_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels);

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

	void InitImGui()
	{
	ImGuiIO& io = ImGui::GetIO();
	io.DeltaTime = 1.0f / 60.0f; // Time elapsed since last frame, in seconds (in this sample app we'll override this every frame because our timestep is variable)
	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 = ImImpl_RenderDrawLists;
	io.SetClipboardTextFn = ImImpl_SetClipboardTextFn;
	io.GetClipboardTextFn = ImImpl_GetClipboardTextFn;

	LoadFontsTexture();
	}

	void UpdateImGui()
	{
	ImGuiIO& io = ImGui::GetIO();

	// Setup resolution (every frame to accommodate for window resizing)
	int w, h;
	int display_w, display_h;
	glfwGetWindowSize(window, &w, &h);
	glfwGetFramebufferSize(window, &display_w, &display_h);
	io.DisplaySize = ImVec2((float)display_w, (float)display_h); // Display size, in pixels. For clamping windows positions.

	// Setup time step
	static double time = 0.0f;
	const double current_time = glfwGetTime();
	io.DeltaTime = (float)(current_time - time);
	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(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.)
	io.MouseDown[0] = mousePressed[0] \|\| glfwGetMouseButton(window, GLFW_MOUSE_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] = mousePressed[1] \|\| glfwGetMouseButton(window, GLFW_MOUSE_BUTTON_RIGHT) != 0;

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

	// Application code
	int main(int argc, char** argv)
	{
	InitGL();
	InitImGui();

	bool show_test_window = true;
	bool show_another_window = false;
	ImVec4 clear_col = ImColor(114, 144, 154);

	while (!glfwWindowShouldClose(window))
	{
	ImGuiIO& io = ImGui::GetIO();
	io.MouseWheel = 0;
	mousePressed[0] = mousePressed[1] = false;
	glfwPollEvents();
	UpdateImGui();

	// 1. Show a simple window
	// Tip: if we don't call ImGui::Begin()/ImGui::End() the widgets appears in a window automatically called "Debug"
	{
	static float f;
	ImGui::Text("Hello, world!");
	ImGui::SliderFloat("float", &f, 0.0f, 1.0f);
	ImGui::ColorEdit3("clear color", (float*)&clear_col);
	if (ImGui::Button("Test Window")) show_test_window ^= 1;
	if (ImGui::Button("Another Window")) show_another_window ^= 1;
	ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / ImGui::GetIO().Framerate, ImGui::GetIO().Framerate);
	}

	// 2. Show another simple window, this time using an explicit Begin/End pair
	if (show_another_window)
	{
	ImGui::Begin("Another Window", &show_another_window, ImVec2(200,100));
	ImGui::Text("Hello");
	ImGui::End();
	}

	// 3. Show the ImGui test window. Most of the sample code is in ImGui::ShowTestWindow()
	if (show_test_window)
	{
	ImGui::SetNextWindowPos(ImVec2(650, 20), ImGuiSetCondition_FirstUseEver);
	ImGui::ShowTestWindow(&show_test_window);
	}

	// Rendering
	glViewport(0, 0, (int)io.DisplaySize.x, (int)io.DisplaySize.y);
	glClearColor(clear_col.x, clear_col.y, clear_col.z, clear_col.w);
	glClear(GL_COLOR_BUFFER_BIT);
	ImGui::Render();
	glfwSwapBuffers(window);
	}

	// Cleanup
	if (vao_handle) glDeleteVertexArrays(1, &vao_handle);
	if (vbo_handle) glDeleteBuffers(1, &vbo_handle);
	glDetachShader(shader_handle, vert_handle);
	glDetachShader(shader_handle, frag_handle);
	glDeleteShader(vert_handle);
	glDeleteShader(frag_handle);
	glDeleteProgram(shader_handle);

	ImGui::Shutdown();
	glfwTerminate();

	return 0;
	}