text: // dear imgui: Renderer Backend for OpenGL2 (legacy OpenGL, fixed pipeline)
  // This needs to be used along with a Platform Backend (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'.
  
  // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this. 
  // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
  // If you are new to Dear ImGui, read documentation from the docs/ folder + read the top of imgui.cpp.
  // Read online: https://github.com/ocornut/imgui/tree/master/docs
  
  // **DO NOT USE THIS CODE IF YOUR CODE/ENGINE IS USING MODERN OPENGL (SHADERS, VBO, VAO, etc.)**
  // **Prefer using the code in imgui_impl_opengl3.cpp**
  // This code is mostly provided as a reference to learn how ImGui integration works, because it is shorter to read.
  // If your code is using GL3+ context or any semi modern OpenGL calls, using this is likely to make everything more
  // complicated, will require your code to reset every single OpenGL attributes to their initial state, and might
  // confuse your GPU driver.
  // The GL2 code is unable to reset attributes or even call e.g. "glUseProgram(0)" because they don't exist in that API.
  
  #pragma once
  #include "imgui.h"      // IMGUI_IMPL_API
  
  IMGUI_IMPL_API bool     ImGui_ImplOpenGL2_Init();
  IMGUI_IMPL_API void     ImGui_ImplOpenGL2_Shutdown();
  IMGUI_IMPL_API void     ImGui_ImplOpenGL2_NewFrame();
  IMGUI_IMPL_API void     ImGui_ImplOpenGL2_RenderDrawData(ImDrawData* draw_data);
  
  // Called by Init/NewFrame/Shutdown
  IMGUI_IMPL_API bool     ImGui_ImplOpenGL2_CreateFontsTexture();
  IMGUI_IMPL_API void     ImGui_ImplOpenGL2_DestroyFontsTexture();
  IMGUI_IMPL_API bool     ImGui_ImplOpenGL2_CreateDeviceObjects();
  IMGUI_IMPL_API void     ImGui_ImplOpenGL2_DestroyDeviceObjects();
  