text: // dear imgui: Renderer for modern OpenGL with shaders / programmatic pipeline
  // - Desktop GL: 2.x 3.x 4.x
  // - Embedded GL: ES 2.0 (WebGL 1.0), ES 3.0 (WebGL 2.0)
  // This needs to be used along with a Platform Binding (e.g. GLFW, SDL, Win32, custom..)
  
  // Implemented features:
  //  [X] Renderer: User texture binding. Use 'GLuint' OpenGL texture identifier as void*/ImTextureID. Read the FAQ about ImTextureID!
  //  [X] Renderer: Multi-viewport support. Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
  //  [x] Renderer: Desktop GL only: Support for large meshes (64k+ vertices) with 16-bit indices.
  
  // You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
  // If you are new to dear imgui, read examples/README.txt and read the documentation at the top of imgui.cpp.
  // https://github.com/ocornut/imgui
  
  // About Desktop OpenGL function loaders:
  //  Modern desktop OpenGL doesn't have a standard portable header file to load OpenGL function pointers.
  //  Helper libraries are often used for this purpose! Here we are supporting a few common ones (gl3w, glew, glad).
  //  You may use another loader/header of your choice (glext, glLoadGen, etc.), or chose to manually implement your own.
  
  // About GLSL version:
  //  The 'glsl_version' initialization parameter should be NULL (default) or a "#version XXX" string.
  //  On computer platform the GLSL version default to "#version 130". On OpenGL ES 3 platform it defaults to "#version 300 es"
  //  Only override if your GL version doesn't handle this GLSL version. See GLSL version table at the top of imgui_impl_opengl3.cpp.
  
  #pragma once
  
  // Backend API
  IMGUI_IMPL_API bool     ImGui_ImplOpenGL3_Init(const char* glsl_version = NULL);
  IMGUI_IMPL_API void     ImGui_ImplOpenGL3_Shutdown();
  IMGUI_IMPL_API void     ImGui_ImplOpenGL3_NewFrame();
  IMGUI_IMPL_API void     ImGui_ImplOpenGL3_RenderDrawData(ImDrawData* draw_data);
  
  // (Optional) Called by Init/NewFrame/Shutdown
  IMGUI_IMPL_API bool     ImGui_ImplOpenGL3_CreateFontsTexture();
  IMGUI_IMPL_API void     ImGui_ImplOpenGL3_DestroyFontsTexture();
  IMGUI_IMPL_API bool     ImGui_ImplOpenGL3_CreateDeviceObjects();
  IMGUI_IMPL_API void     ImGui_ImplOpenGL3_DestroyDeviceObjects();
  
  // Specific OpenGL versions
  //#define IMGUI_IMPL_OPENGL_ES2     // Auto-detected on Emscripten
  //#define IMGUI_IMPL_OPENGL_ES3     // Auto-detected on iOS/Android
  
  // Desktop OpenGL: attempt to detect default GL loader based on available header files.
  // If auto-detection fails or doesn't select the same GL loader file as used by your application,
  // you are likely to get a crash in ImGui_ImplOpenGL3_Init().
  // You can explicitly select a loader by using '#define IMGUI_IMPL_OPENGL_LOADER_XXX' in imconfig.h or compiler command-line.
  #if !defined(IMGUI_IMPL_OPENGL_LOADER_GL3W) \
   && !defined(IMGUI_IMPL_OPENGL_LOADER_GLEW) \
   && !defined(IMGUI_IMPL_OPENGL_LOADER_GLAD) \
   && !defined(IMGUI_IMPL_OPENGL_LOADER_CUSTOM)
      #if defined(__has_include)
          #if __has_include(<GL/glew.h>)
              #define IMGUI_IMPL_OPENGL_LOADER_GLEW
          #elif __has_include(<glad/glad.h>)
              #define IMGUI_IMPL_OPENGL_LOADER_GLAD
          #elif __has_include(<GL/gl3w.h>)
              #define IMGUI_IMPL_OPENGL_LOADER_GL3W
          #else
              #error "Cannot detect OpenGL loader!"
          #endif
      #else
          #define IMGUI_IMPL_OPENGL_LOADER_GL3W       // Default to GL3W
      #endif
  #endif
  
  