text: // Dear ImGui: standalone example application for Emscripten, using SDL2 + OpenGL3
  // (Emscripten is a C++-to-javascript compiler, used to publish executables for the web. See https://emscripten.org/)
  // 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
  
  // This is mostly the same code as the SDL2 + OpenGL3 example, simply with the modifications needed to run on Emscripten.
  // It is possible to combine both code into a single source file that will compile properly on Desktop and using Emscripten.
  // See https://github.com/ocornut/imgui/pull/2492 as an example on how to do just that.
  
  #include "imgui.h"
  #include "imgui_impl_sdl.h"
  #include "imgui_impl_opengl3.h"
  #include <stdio.h>
  #include <emscripten.h>
  #include <SDL.h>
  #include <SDL_opengles2.h>
  
  // Emscripten requires to have full control over the main loop. We're going to store our SDL book-keeping variables globally.
  // Having a single function that acts as a loop prevents us to store state in the stack of said function. So we need some location for this.
  SDL_Window*     g_Window = NULL;
  SDL_GLContext   g_GLContext = NULL;
  
  // For clarity, our main loop code is declared at the end.
  static void main_loop(void*);
  
  int main(int, char**)
  {
      // Setup SDL
      if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER | SDL_INIT_GAMECONTROLLER) != 0)
      {
          printf("Error: %s\n", SDL_GetError());
          return -1;
      }
  
      // For the browser using Emscripten, we are going to use WebGL1 with GL ES2. See the Makefile. for requirement details.
      // It is very likely the generated file won't work in many browsers. Firefox is the only sure bet, but I have successfully
      // run this code on Chrome for Android for example.
      const char* glsl_version = "#version 100";
      //const char* glsl_version = "#version 300 es";
      SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, 0);
      SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_ES);
      SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
      SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
  
      // Create window with graphics context
      SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
      SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
      SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
      SDL_DisplayMode current;
      SDL_GetCurrentDisplayMode(0, &current);
      SDL_WindowFlags window_flags = (SDL_WindowFlags)(SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI);
      g_Window = SDL_CreateWindow("Dear ImGui Emscripten example", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 1280, 720, window_flags);
      g_GLContext = SDL_GL_CreateContext(g_Window);
      if (!g_GLContext)
      {
          fprintf(stderr, "Failed to initialize WebGL context!\n");
          return 1;
      }
      SDL_GL_SetSwapInterval(1); // Enable vsync
  
      // Setup Dear ImGui context
      IMGUI_CHECKVERSION();
      ImGui::CreateContext();
      ImGuiIO& io = ImGui::GetIO(); (void)io;
      //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
      //io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
  
      // For an Emscripten build we are disabling file-system access, so let's not attempt to do a fopen() of the imgui.ini file.
      // You may manually call LoadIniSettingsFromMemory() to load settings from your own storage.
      io.IniFilename = NULL;
  
      // Setup Dear ImGui style
      ImGui::StyleColorsDark();
      //ImGui::StyleColorsClassic();
  
      // Setup Platform/Renderer backends
      ImGui_ImplSDL2_InitForOpenGL(g_Window, g_GLContext);
      ImGui_ImplOpenGL3_Init(glsl_version);
  
      // Load Fonts
      // - If no fonts are loaded, dear imgui will use the default font. You can also load multiple fonts and use ImGui::PushFont()/PopFont() to select them.
      // - AddFontFromFileTTF() will return the ImFont* so you can store it if you need to select the font among multiple.
      // - If the file cannot be loaded, the function will return NULL. Please handle those errors in your application (e.g. use an assertion, or display an error and quit).
      // - The fonts will be rasterized at a given size (w/ oversampling) and stored into a texture when calling ImFontAtlas::Build()/GetTexDataAsXXXX(), which ImGui_ImplXXXX_NewFrame below will call.
      // - Read 'docs/FONTS.md' for more instructions and details.
      // - Remember that in C/C++ if you want to include a backslash \ in a string literal you need to write a double backslash \\ !
      // - Emscripten allows preloading a file or folder to be accessible at runtime. See Makefile for details.
      //io.Fonts->AddFontDefault();
  #ifndef IMGUI_DISABLE_FILE_FUNCTIONS
      io.Fonts->AddFontFromFileTTF("fonts/Roboto-Medium.ttf", 16.0f);
      //io.Fonts->AddFontFromFileTTF("fonts/Cousine-Regular.ttf", 15.0f);
      //io.Fonts->AddFontFromFileTTF("fonts/DroidSans.ttf", 16.0f);
      //io.Fonts->AddFontFromFileTTF("fonts/ProggyTiny.ttf", 10.0f);
      //ImFont* font = io.Fonts->AddFontFromFileTTF("fonts/ArialUni.ttf", 18.0f, NULL, io.Fonts->GetGlyphRangesJapanese());
      //IM_ASSERT(font != NULL);
  #endif
  
      // This function call won't return, and will engage in an infinite loop, processing events from the browser, and dispatching them.
      emscripten_set_main_loop_arg(main_loop, NULL, 0, true);
  }
  
  static void main_loop(void* arg)
  {
      ImGuiIO& io = ImGui::GetIO();
      IM_UNUSED(arg); // We can pass this argument as the second parameter of emscripten_set_main_loop_arg(), but we don't use that.
  
      // Our state (make them static = more or less global) as a convenience to keep the example terse.
      static bool show_demo_window = true;
      static bool show_another_window = false;
      static ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);
  
      // Poll and handle events (inputs, window resize, etc.)
      // You can read the io.WantCaptureMouse, io.WantCaptureKeyboard flags to tell if dear imgui wants to use your inputs.
      // - When io.WantCaptureMouse is true, do not dispatch mouse input data to your main application.
      // - When io.WantCaptureKeyboard is true, do not dispatch keyboard input data to your main application.
      // Generally you may always pass all inputs to dear imgui, and hide them from your application based on those two flags.
      SDL_Event event;
      while (SDL_PollEvent(&event))
      {
          ImGui_ImplSDL2_ProcessEvent(&event);
          // Capture events here, based on io.WantCaptureMouse and io.WantCaptureKeyboard
      }
  
      // Start the Dear ImGui frame
      ImGui_ImplOpenGL3_NewFrame();
      ImGui_ImplSDL2_NewFrame();
      ImGui::NewFrame();
  
      // 1. Show the big demo window (Most of the sample code is in ImGui::ShowDemoWindow()! You can browse its code to learn more about Dear ImGui!).
      if (show_demo_window)
          ImGui::ShowDemoWindow(&show_demo_window);
  
      // 2. Show a simple window that we create ourselves. We use a Begin/End pair to created a named window.
      {
          static float f = 0.0f;
          static int counter = 0;
  
          ImGui::Begin("Hello, world!");                                // Create a window called "Hello, world!" and append into it.
  
          ImGui::Text("This is some useful text.");                     // Display some text (you can use a format strings too)
          ImGui::Checkbox("Demo Window", &show_demo_window);            // Edit bools storing our window open/close state
          ImGui::Checkbox("Another Window", &show_another_window);
  
          ImGui::SliderFloat("float", &f, 0.0f, 1.0f);                  // Edit 1 float using a slider from 0.0f to 1.0f
          ImGui::ColorEdit3("clear color", (float*)&clear_color);       // Edit 3 floats representing a color
  
          if (ImGui::Button("Button"))                                  // Buttons return true when clicked (most widgets return true when edited/activated)
              counter++;
          ImGui::SameLine();
          ImGui::Text("counter = %d", counter);
  
          ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / ImGui::GetIO().Framerate, ImGui::GetIO().Framerate);
          ImGui::End();
      }
  
      // 3. Show another simple window.
      if (show_another_window)
      {
          ImGui::Begin("Another Window", &show_another_window);         // Pass a pointer to our bool variable (the window will have a closing button that will clear the bool when clicked)
          ImGui::Text("Hello from another window!");
          if (ImGui::Button("Close Me"))
              show_another_window = false;
          ImGui::End();
      }
  
      // Rendering
      ImGui::Render();
      SDL_GL_MakeCurrent(g_Window, g_GLContext);
      glViewport(0, 0, (int)io.DisplaySize.x, (int)io.DisplaySize.y);
      glClearColor(clear_color.x * clear_color.w, clear_color.y * clear_color.w, clear_color.z * clear_color.w, clear_color.w);
      glClear(GL_COLOR_BUFFER_BIT);
      ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
      SDL_GL_SwapWindow(g_Window);
  }
  