text: // ImGui SDL2 binding with OpenGL
  // In this binding, ImTextureID is used to store an OpenGL 'GLuint' texture identifier. Read the FAQ about ImTextureID in imgui.cpp.
  
  // 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
  
  #pragma warning( push, 0 )
  #include <SDL.h>
  #include <SDL_syswm.h>
  #include <SDL_opengl.h>
  #pragma warning ( pop )
  #include <imgui.h>
  #include "imgui_impl_sdl.h"
  
  // Data
  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)
  void ImGui_ImplSdl_RenderDrawLists(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.
      GLint last_texture; glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
      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);
      //glUseProgram(0); // You may want this if using this code in an OpenGL 3+ context
  
      // 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
      #define OFFSETOF(TYPE, ELEMENT) ((size_t)&(((TYPE *)0)->ELEMENT))
      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 + OFFSETOF(ImDrawVert, pos)));
          glTexCoordPointer(2, GL_FLOAT, sizeof(ImDrawVert), (const GLvoid*)((const char*)vtx_buffer + OFFSETOF(ImDrawVert, uv)));
          glColorPointer(4, GL_UNSIGNED_BYTE, sizeof(ImDrawVert), (const GLvoid*)((const char*)vtx_buffer + 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;
          }
      }
      #undef OFFSETOF
  
      // 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();
      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_ImplSdl_GetClipboardText(void*)
  {
      return SDL_GetClipboardText();
  }
  
  static void ImGui_ImplSdl_SetClipboardText(void*, const char* text)
  {
      SDL_SetClipboardText(text);
  }
  
  bool ImGui_ImplSdl_ProcessEvent(SDL_Event* event)
  {
      ImGuiIO& io = ImGui::GetIO();
      switch (event->type)
      {
      case SDL_MOUSEWHEEL:
          {
              if (event->wheel.y > 0)
                  g_MouseWheel = 1;
              if (event->wheel.y < 0)
                  g_MouseWheel = -1;
              return true;
          }
      case SDL_MOUSEBUTTONDOWN:
          {
              if (event->button.button == SDL_BUTTON_LEFT) g_MousePressed[0] = true;
              if (event->button.button == SDL_BUTTON_RIGHT) g_MousePressed[1] = true;
              if (event->button.button == SDL_BUTTON_MIDDLE) g_MousePressed[2] = true;
              return true;
          }
      case SDL_TEXTINPUT:
          {
              io.AddInputCharactersUTF8(event->text.text);
              return true;
          }
      case SDL_KEYDOWN:
      case SDL_KEYUP:
          {
              int key = event->key.keysym.sym & ~SDLK_SCANCODE_MASK;
              io.KeysDown[key] = (event->type == SDL_KEYDOWN);
              io.KeyShift = ((SDL_GetModState() & KMOD_SHIFT) != 0);
              io.KeyCtrl = ((SDL_GetModState() & KMOD_CTRL) != 0);
              io.KeyAlt = ((SDL_GetModState() & KMOD_ALT) != 0);
              io.KeySuper = ((SDL_GetModState() & KMOD_GUI) != 0);
              return true;
          }
      }
      return false;
  }
  
  bool ImGui_ImplSdl_CreateDeviceObjects()
  {
      // Build texture atlas
      ImGuiIO& io = ImGui::GetIO();
      unsigned char* pixels;
      int width, height;
      io.Fonts->GetTexDataAsAlpha8(&pixels, &width, &height);
  
      // Upload texture to graphics system
      GLint last_texture;
      glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
      glGenTextures(1, &g_FontTexture);
      glBindTexture(GL_TEXTURE_2D, g_FontTexture);
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
      glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
      glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, width, height, 0, GL_ALPHA, GL_UNSIGNED_BYTE, pixels);
  
      // Store our identifier
      io.Fonts->TexID = (void *)(intptr_t)g_FontTexture;
  
      // Restore state
      glBindTexture(GL_TEXTURE_2D, last_texture);
  
      return true;
  }
  
  void    ImGui_ImplSdl_InvalidateDeviceObjects()
  {
      if (g_FontTexture)
      {
          glDeleteTextures(1, &g_FontTexture);
          ImGui::GetIO().Fonts->TexID = 0;
          g_FontTexture = 0;
      }
  }
  
  bool    ImGui_ImplSdl_Init(SDL_Window* window)
  {
      ImGuiIO& io = ImGui::GetIO();
      io.KeyMap[ImGuiKey_Tab] = SDLK_TAB;                     // Keyboard mapping. ImGui will use those indices to peek into the io.KeyDown[] array.
      io.KeyMap[ImGuiKey_LeftArrow] = SDL_SCANCODE_LEFT;
      io.KeyMap[ImGuiKey_RightArrow] = SDL_SCANCODE_RIGHT;
      io.KeyMap[ImGuiKey_UpArrow] = SDL_SCANCODE_UP;
      io.KeyMap[ImGuiKey_DownArrow] = SDL_SCANCODE_DOWN;
      io.KeyMap[ImGuiKey_PageUp] = SDL_SCANCODE_PAGEUP;
      io.KeyMap[ImGuiKey_PageDown] = SDL_SCANCODE_PAGEDOWN;
      io.KeyMap[ImGuiKey_Home] = SDL_SCANCODE_HOME;
      io.KeyMap[ImGuiKey_End] = SDL_SCANCODE_END;
      io.KeyMap[ImGuiKey_Delete] = SDLK_DELETE;
      io.KeyMap[ImGuiKey_Backspace] = SDLK_BACKSPACE;
      io.KeyMap[ImGuiKey_Enter] = SDLK_RETURN;
      io.KeyMap[ImGuiKey_Escape] = SDLK_ESCAPE;
      io.KeyMap[ImGuiKey_A] = SDLK_a;
      io.KeyMap[ImGuiKey_C] = SDLK_c;
      io.KeyMap[ImGuiKey_V] = SDLK_v;
      io.KeyMap[ImGuiKey_X] = SDLK_x;
      io.KeyMap[ImGuiKey_Y] = SDLK_y;
      io.KeyMap[ImGuiKey_Z] = SDLK_z;
  
      io.RenderDrawListsFn = ImGui_ImplSdl_RenderDrawLists;   // Alternatively you can set this to NULL and call ImGui::GetDrawData() after ImGui::Render() to get the same ImDrawData pointer.
      io.SetClipboardTextFn = ImGui_ImplSdl_SetClipboardText;
      io.GetClipboardTextFn = ImGui_ImplSdl_GetClipboardText;
      io.ClipboardUserData = NULL;
  
  #ifdef _WIN32
      SDL_SysWMinfo wmInfo;
      SDL_VERSION(&wmInfo.version);
      SDL_GetWindowWMInfo(window, &wmInfo);
      io.ImeWindowHandle = wmInfo.info.win.window;
  #else
      (void)window;
  #endif
  
      return true;
  }
  
  void ImGui_ImplSdl_Shutdown()
  {
      ImGui_ImplSdl_InvalidateDeviceObjects();
      ImGui::Shutdown();
  }
  
  void ImGui_ImplSdl_NewFrame(SDL_Window *window)
  {
      if (!g_FontTexture)
          ImGui_ImplSdl_CreateDeviceObjects();
  
      ImGuiIO& io = ImGui::GetIO();
  
      // Setup display size (every frame to accommodate for window resizing)
      int w, h;
      int display_w, display_h;
      SDL_GetWindowSize(window, &w, &h);
      SDL_GL_GetDrawableSize(window, &display_w, &display_h);
      io.DisplaySize = ImVec2((float)w, (float)h);
      io.DisplayFramebufferScale = ImVec2(w > 0 ? ((float)display_w / w) : 0, h > 0 ? ((float)display_h / h) : 0);
  
      // Setup time step
      Uint32	time = SDL_GetTicks();
      double current_time = time / 1000.0;
      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 SDL_PollEvent())
      int mx, my;
      Uint32 mouseMask = SDL_GetMouseState(&mx, &my);
      if (SDL_GetWindowFlags(window) & SDL_WINDOW_MOUSE_FOCUS)
          io.MousePos = ImVec2((float)mx, (float)my);   // Mouse position, in pixels (set to -1,-1 if no mouse / on another screen, etc.)
      else
          io.MousePos = ImVec2(-1,-1);
  
      io.MouseDown[0] = g_MousePressed[0] || (mouseMask & SDL_BUTTON(SDL_BUTTON_LEFT)) != 0;		// If a mouse press event came, always pass it as "mouse held this frame", so we don't miss click-release events that are shorter than 1 frame.
      io.MouseDown[1] = g_MousePressed[1] || (mouseMask & SDL_BUTTON(SDL_BUTTON_RIGHT)) != 0;
      io.MouseDown[2] = g_MousePressed[2] || (mouseMask & SDL_BUTTON(SDL_BUTTON_MIDDLE)) != 0;
      g_MousePressed[0] = g_MousePressed[1] = g_MousePressed[2] = false;
  
      io.MouseWheel = g_MouseWheel;
      g_MouseWheel = 0.0f;
  
      // Hide OS mouse cursor if ImGui is drawing it
      SDL_ShowCursor(io.MouseDrawCursor ? 0 : 1);
  
      // Start the frame
      ImGui::NewFrame();
  }
  