source: opengl-game/imgui_impl_glfw_gl3.cpp@ 4e0b82b

// ImGui GLFW binding with OpenGL3 + shaders
// (GLFW is a cross-platform general purpose library for handling windows, inputs, OpenGL/Vulkan graphics context creation, etc.)
// (GL3W is a helper library to access OpenGL functions since there is no standard header to access modern OpenGL functions easily. Alternatives are GLEW, Glad, etc.)

// Implemented features:
//  [X] User texture binding. Cast 'GLuint' OpenGL texture identifier as void*/ImTextureID. Read the FAQ about ImTextureID in imgui.cpp.
//  [X] Gamepad navigation mapping. Enable with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.

// 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.
//  2018-03-06: OpenGL: Added const char* glsl_version parameter to ImGui_ImplGlfwGL3_Init() so user can override the GLSL version e.g. "#version 150".
//  2018-02-23: OpenGL: Create the VAO in the render function so the setup can more easily be used with multiple shared GL context.
//  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 GL3 in their name.
//  2018-02-16: Misc: Obsoleted the io.RenderDrawListsFn callback and exposed ImGui_ImplGlfwGL3_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.
//  2018-01-25: Inputs: Added gamepad support if ImGuiConfigFlags_NavEnableGamepad is set.
//  2018-01-25: 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.
//  2018-01-07: OpenGL: Changed GLSL shader version from 330 to 150. (Also changed GL context from 3.3 to 3.2 in example's main.cpp)
//  2017-09-01: OpenGL: Save and restore current bound sampler. 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).
//  2017-05-01: OpenGL: Fixed save and restore of current blend function state.
//  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.
//  2016-04-30: OpenGL: Fixed save and restore of current GL_ACTIVE_TEXTURE.

#if defined(_MSC_VER) && !defined(_CRT_SECURE_NO_WARNINGS)
#define _CRT_SECURE_NO_WARNINGS
#endif

#include "imgui.h"
#include "imgui_impl_glfw_gl3.h"

// GL3W/GLFW
#include "gl3w.h"    // This example is using gl3w to access OpenGL functions (because it is small). You may use glew/glad/glLoadGen/etc. whatever already works for you.
#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 };

// OpenGL3 data
static char         g_GlslVersion[32] = "#version 150";
static GLuint       g_FontTexture = 0;
static int          g_ShaderHandle = 0, g_VertHandle = 0, g_FragHandle = 0;
static int          g_AttribLocationTex = 0, g_AttribLocationProjMtx = 0;
static int          g_AttribLocationPosition = 0, g_AttribLocationUV = 0, g_AttribLocationColor = 0;
static unsigned int g_VboHandle = 0, g_ElementsHandle = 0;

// OpenGL3 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_ImplGlfwGL3_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);

   // Backup GL state
   GLenum last_active_texture; glGetIntegerv(GL_ACTIVE_TEXTURE, (GLint*)&last_active_texture);
   glActiveTexture(GL_TEXTURE0);
   GLint last_program; glGetIntegerv(GL_CURRENT_PROGRAM, &last_program);
   GLint last_texture; glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
   GLint last_sampler; glGetIntegerv(GL_SAMPLER_BINDING, &last_sampler);
   GLint last_array_buffer; glGetIntegerv(GL_ARRAY_BUFFER_BINDING, &last_array_buffer);
   GLint last_element_array_buffer; glGetIntegerv(GL_ELEMENT_ARRAY_BUFFER_BINDING, &last_element_array_buffer);
   GLint last_vertex_array; glGetIntegerv(GL_VERTEX_ARRAY_BINDING, &last_vertex_array);
   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);
   GLenum last_blend_src_rgb; glGetIntegerv(GL_BLEND_SRC_RGB, (GLint*)&last_blend_src_rgb);
   GLenum last_blend_dst_rgb; glGetIntegerv(GL_BLEND_DST_RGB, (GLint*)&last_blend_dst_rgb);
   GLenum last_blend_src_alpha; glGetIntegerv(GL_BLEND_SRC_ALPHA, (GLint*)&last_blend_src_alpha);
   GLenum last_blend_dst_alpha; glGetIntegerv(GL_BLEND_DST_ALPHA, (GLint*)&last_blend_dst_alpha);
   GLenum last_blend_equation_rgb; glGetIntegerv(GL_BLEND_EQUATION_RGB, (GLint*)&last_blend_equation_rgb);
   GLenum last_blend_equation_alpha; glGetIntegerv(GL_BLEND_EQUATION_ALPHA, (GLint*)&last_blend_equation_alpha);
   GLboolean last_enable_blend = glIsEnabled(GL_BLEND);
   GLboolean last_enable_cull_face = glIsEnabled(GL_CULL_FACE);
   GLboolean last_enable_depth_test = glIsEnabled(GL_DEPTH_TEST);
   GLboolean last_enable_scissor_test = glIsEnabled(GL_SCISSOR_TEST);

   // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled, polygon fill
   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);
   glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);

   // Setup viewport, orthographic projection matrix
   glViewport(0, 0, (GLsizei)fb_width, (GLsizei)fb_height);
   const float ortho_projection[4][4] =
   {
      { 2.0f / io.DisplaySize.x, 0.0f,                   0.0f, 0.0f },
   { 0.0f,                  2.0f / -io.DisplaySize.y, 0.0f, 0.0f },
   { 0.0f,                  0.0f,                  -1.0f, 0.0f },
   { -1.0f,                  1.0f,                   0.0f, 1.0f },
   };
   glUseProgram(g_ShaderHandle);
   glUniform1i(g_AttribLocationTex, 0);
   glUniformMatrix4fv(g_AttribLocationProjMtx, 1, GL_FALSE, &ortho_projection[0][0]);
   glBindSampler(0, 0); // Rely on combined texture/sampler state.

                        // Recreate the VAO every time 
                        // (This is to easily allow multiple GL contexts. VAO are not shared among GL contexts, and we don't track creation/deletion of windows so we don't have an obvious key to use to cache them.)
   GLuint vao_handle = 0;
   glGenVertexArrays(1, &vao_handle);
   glBindVertexArray(vao_handle);
   glBindBuffer(GL_ARRAY_BUFFER, g_VboHandle);
   glEnableVertexAttribArray(g_AttribLocationPosition);
   glEnableVertexAttribArray(g_AttribLocationUV);
   glEnableVertexAttribArray(g_AttribLocationColor);
   glVertexAttribPointer(g_AttribLocationPosition, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, pos));
   glVertexAttribPointer(g_AttribLocationUV, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, uv));
   glVertexAttribPointer(g_AttribLocationColor, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, col));

   // Draw
   for (int n = 0; n < draw_data->CmdListsCount; n++)
   {
      const ImDrawList* cmd_list = draw_data->CmdLists[n];
      const ImDrawIdx* idx_buffer_offset = 0;

      glBindBuffer(GL_ARRAY_BUFFER, g_VboHandle);
      glBufferData(GL_ARRAY_BUFFER, (GLsizeiptr)cmd_list->VtxBuffer.Size * sizeof(ImDrawVert), (const GLvoid*)cmd_list->VtxBuffer.Data, GL_STREAM_DRAW);

      glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, g_ElementsHandle);
      glBufferData(GL_ELEMENT_ARRAY_BUFFER, (GLsizeiptr)cmd_list->IdxBuffer.Size * sizeof(ImDrawIdx), (const GLvoid*)cmd_list->IdxBuffer.Data, GL_STREAM_DRAW);

      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_offset);
         }
         idx_buffer_offset += pcmd->ElemCount;
      }
   }
   glDeleteVertexArrays(1, &vao_handle);

   // Restore modified GL state
   glUseProgram(last_program);
   glBindTexture(GL_TEXTURE_2D, last_texture);
   glBindSampler(0, last_sampler);
   glActiveTexture(last_active_texture);
   glBindVertexArray(last_vertex_array);
   glBindBuffer(GL_ARRAY_BUFFER, last_array_buffer);
   glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, last_element_array_buffer);
   glBlendEquationSeparate(last_blend_equation_rgb, last_blend_equation_alpha);
   glBlendFuncSeparate(last_blend_src_rgb, last_blend_dst_rgb, last_blend_src_alpha, last_blend_dst_alpha);
   if (last_enable_blend) glEnable(GL_BLEND); else glDisable(GL_BLEND);
   if (last_enable_cull_face) glEnable(GL_CULL_FACE); else glDisable(GL_CULL_FACE);
   if (last_enable_depth_test) glEnable(GL_DEPTH_TEST); else glDisable(GL_DEPTH_TEST);
   if (last_enable_scissor_test) glEnable(GL_SCISSOR_TEST); else glDisable(GL_SCISSOR_TEST);
   glPolygonMode(GL_FRONT_AND_BACK, (GLenum)last_polygon_mode[0]);
   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_ImplGlfwGL3_GetClipboardText(void* user_data)
{
   return glfwGetClipboardString((GLFWwindow*)user_data);
}

static void ImGui_ImplGlfwGL3_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_ImplGlfwGL3_CreateFontsTexture()
{
   // 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;
}

bool ImGui_ImplGlfwGL3_CreateDeviceObjects()
{
   // Backup GL state
   GLint last_texture, last_array_buffer, last_vertex_array;
   glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
   glGetIntegerv(GL_ARRAY_BUFFER_BINDING, &last_array_buffer);
   glGetIntegerv(GL_VERTEX_ARRAY_BINDING, &last_vertex_array);

   const GLchar* vertex_shader =
      "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 =
      "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";

   const GLchar* vertex_shader_with_version[2] = { g_GlslVersion, vertex_shader };
   const GLchar* fragment_shader_with_version[2] = { g_GlslVersion, fragment_shader };

   g_ShaderHandle = glCreateProgram();
   g_VertHandle = glCreateShader(GL_VERTEX_SHADER);
   g_FragHandle = glCreateShader(GL_FRAGMENT_SHADER);
   glShaderSource(g_VertHandle, 2, vertex_shader_with_version, NULL);
   glShaderSource(g_FragHandle, 2, fragment_shader_with_version, NULL);
   glCompileShader(g_VertHandle);
   glCompileShader(g_FragHandle);
   glAttachShader(g_ShaderHandle, g_VertHandle);
   glAttachShader(g_ShaderHandle, g_FragHandle);
   glLinkProgram(g_ShaderHandle);

   g_AttribLocationTex = glGetUniformLocation(g_ShaderHandle, "Texture");
   g_AttribLocationProjMtx = glGetUniformLocation(g_ShaderHandle, "ProjMtx");
   g_AttribLocationPosition = glGetAttribLocation(g_ShaderHandle, "Position");
   g_AttribLocationUV = glGetAttribLocation(g_ShaderHandle, "UV");
   g_AttribLocationColor = glGetAttribLocation(g_ShaderHandle, "Color");

   glGenBuffers(1, &g_VboHandle);
   glGenBuffers(1, &g_ElementsHandle);

   ImGui_ImplGlfwGL3_CreateFontsTexture();

   // Restore modified GL state
   glBindTexture(GL_TEXTURE_2D, last_texture);
   glBindBuffer(GL_ARRAY_BUFFER, last_array_buffer);
   glBindVertexArray(last_vertex_array);

   return true;
}

void    ImGui_ImplGlfwGL3_InvalidateDeviceObjects()
{
   if (g_VboHandle) glDeleteBuffers(1, &g_VboHandle);
   if (g_ElementsHandle) glDeleteBuffers(1, &g_ElementsHandle);
   g_VboHandle = g_ElementsHandle = 0;

   if (g_ShaderHandle && g_VertHandle) glDetachShader(g_ShaderHandle, g_VertHandle);
   if (g_VertHandle) glDeleteShader(g_VertHandle);
   g_VertHandle = 0;

   if (g_ShaderHandle && g_FragHandle) glDetachShader(g_ShaderHandle, g_FragHandle);
   if (g_FragHandle) glDeleteShader(g_FragHandle);
   g_FragHandle = 0;

   if (g_ShaderHandle) glDeleteProgram(g_ShaderHandle);
   g_ShaderHandle = 0;

   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_ImplGlfwGL3_Init(GLFWwindow* window, bool install_callbacks, const char* glsl_version)
{
   g_Window = window;

   // Store GL version string so we can refer to it later in case we recreate shaders.
   if (glsl_version == NULL)
      glsl_version = "#version 150";
   IM_ASSERT((int)strlen(glsl_version) + 2 < IM_ARRAYSIZE(g_GlslVersion));
   strcpy(g_GlslVersion, glsl_version);
   strcat(g_GlslVersion, "\n");

   // 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_ImplGlfwGL3_SetClipboardText;
   io.GetClipboardTextFn = ImGui_ImplGlfwGL3_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_ImplGlfwGL3_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_ImplGlfwGL3_InvalidateDeviceObjects();
}

void ImGui_ImplGlfwGL3_NewFrame()
{
   if (!g_FontTexture)
      ImGui_ImplGlfwGL3_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);
      }
   }

   // Gamepad navigation mapping [BETA]
   memset(io.NavInputs, 0, sizeof(io.NavInputs));
   if (io.ConfigFlags & ImGuiConfigFlags_NavEnableGamepad)
   {
      // Update gamepad inputs
#define MAP_BUTTON(NAV_NO, BUTTON_NO)       { if (buttons_count > BUTTON_NO && buttons[BUTTON_NO] == GLFW_PRESS) io.NavInputs[NAV_NO] = 1.0f; }
#define MAP_ANALOG(NAV_NO, AXIS_NO, V0, V1) { float v = (axes_count > AXIS_NO) ? axes[AXIS_NO] : V0; v = (v - V0) / (V1 - V0); if (v > 1.0f) v = 1.0f; if (io.NavInputs[NAV_NO] < v) io.NavInputs[NAV_NO] = v; }
      int axes_count = 0, buttons_count = 0;
      const float* axes = glfwGetJoystickAxes(GLFW_JOYSTICK_1, &axes_count);
      const unsigned char* buttons = glfwGetJoystickButtons(GLFW_JOYSTICK_1, &buttons_count);
      MAP_BUTTON(ImGuiNavInput_Activate, 0);     // Cross / A
      MAP_BUTTON(ImGuiNavInput_Cancel, 1);     // Circle / B
      MAP_BUTTON(ImGuiNavInput_Menu, 2);     // Square / X
      MAP_BUTTON(ImGuiNavInput_Input, 3);     // Triangle / Y
      MAP_BUTTON(ImGuiNavInput_DpadLeft, 13);    // D-Pad Left
      MAP_BUTTON(ImGuiNavInput_DpadRight, 11);    // D-Pad Right
      MAP_BUTTON(ImGuiNavInput_DpadUp, 10);    // D-Pad Up
      MAP_BUTTON(ImGuiNavInput_DpadDown, 12);    // D-Pad Down
      MAP_BUTTON(ImGuiNavInput_FocusPrev, 4);     // L1 / LB
      MAP_BUTTON(ImGuiNavInput_FocusNext, 5);     // R1 / RB
      MAP_BUTTON(ImGuiNavInput_TweakSlow, 4);     // L1 / LB
      MAP_BUTTON(ImGuiNavInput_TweakFast, 5);     // R1 / RB
      MAP_ANALOG(ImGuiNavInput_LStickLeft, 0, -0.3f, -0.9f);
      MAP_ANALOG(ImGuiNavInput_LStickRight, 0, +0.3f, +0.9f);
      MAP_ANALOG(ImGuiNavInput_LStickUp, 1, +0.3f, +0.9f);
      MAP_ANALOG(ImGuiNavInput_LStickDown, 1, -0.3f, -0.9f);
#undef MAP_BUTTON
#undef MAP_ANALOG
      if (axes_count > 0 && buttons_count > 0)
         io.BackendFlags |= ImGuiBackendFlags_HasGamepad;
      else
         io.BackendFlags &= ~ImGuiBackendFlags_HasGamepad;
   }

   // 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();
}