text: /*******************************************************************************************
  *
  *   raylib [core] example - window scale letterbox (and virtual mouse)
  *
  *   This example has been created using raylib 2.5 (www.raylib.com)
  *   raylib is licensed under an unmodified zlib/libpng license (View raylib.h for details)
  *
  *   Example contributed by Anata (@anatagawa) and reviewed by Ramon Santamaria (@raysan5)
  *
  *   Copyright (c) 2019 Anata (@anatagawa) and Ramon Santamaria (@raysan5)
  *
  ********************************************************************************************/
  
  #include "raylib.h"
  
  #define max(a, b) ((a)>(b)? (a) : (b))
  #define min(a, b) ((a)<(b)? (a) : (b))
  
  // Clamp Vector2 value with min and max and return a new vector2
  // NOTE: Required for virtual mouse, to clamp inside virtual game size
  Vector2 ClampValue(Vector2 value, Vector2 min, Vector2 max)
  {
      Vector2 result = value;
      result.x = (result.x > max.x)? max.x : result.x;
      result.x = (result.x < min.x)? min.x : result.x;
      result.y = (result.y > max.y)? max.y : result.y;
      result.y = (result.y < min.y)? min.y : result.y;
      return result;
  }
  
  int main(void)
  {
      const int windowWidth = 800;
      const int windowHeight = 450;
  
      // Enable config flags for resizable window and vertical synchro
      SetConfigFlags(FLAG_WINDOW_RESIZABLE | FLAG_VSYNC_HINT);
      InitWindow(windowWidth, windowHeight, "raylib [core] example - window scale letterbox");
      SetWindowMinSize(320, 240);
  
      int gameScreenWidth = 640;
      int gameScreenHeight = 480;
  
      // Render texture initialization, used to hold the rendering result so we can easily resize it
      RenderTexture2D target = LoadRenderTexture(gameScreenWidth, gameScreenHeight);
      SetTextureFilter(target.texture, TEXTURE_FILTER_BILINEAR);  // Texture scale filter to use
  
      Color colors[10] = { 0 };
      for (int i = 0; i < 10; i++) colors[i] = (Color){ GetRandomValue(100, 250), GetRandomValue(50, 150), GetRandomValue(10, 100), 255 };
  
      SetTargetFPS(60);                   // Set our game to run at 60 frames-per-second
      //--------------------------------------------------------------------------------------
  
      // Main game loop
      while (!WindowShouldClose())        // Detect window close button or ESC key
      {
          // Update
          //----------------------------------------------------------------------------------
          // Compute required framebuffer scaling
          float scale = min((float)GetScreenWidth()/gameScreenWidth, (float)GetScreenHeight()/gameScreenHeight);
  
          if (IsKeyPressed(KEY_SPACE))
          {
              // Recalculate random colors for the bars
              for (int i = 0; i < 10; i++) colors[i] = (Color){ GetRandomValue(100, 250), GetRandomValue(50, 150), GetRandomValue(10, 100), 255 };
          }
  
          // Update virtual mouse (clamped mouse value behind game screen)
          Vector2 mouse = GetMousePosition();
          Vector2 virtualMouse = { 0 };
          virtualMouse.x = (mouse.x - (GetScreenWidth() - (gameScreenWidth*scale))*0.5f)/scale;
          virtualMouse.y = (mouse.y - (GetScreenHeight() - (gameScreenHeight*scale))*0.5f)/scale;
          virtualMouse = ClampValue(virtualMouse, (Vector2){ 0, 0 }, (Vector2){ (float)gameScreenWidth, (float)gameScreenHeight });
  
          // Apply the same transformation as the virtual mouse to the real mouse (i.e. to work with raygui)
          //SetMouseOffset(-(GetScreenWidth() - (gameScreenWidth*scale))*0.5f, -(GetScreenHeight() - (gameScreenHeight*scale))*0.5f);
          //SetMouseScale(1/scale, 1/scale);
          //----------------------------------------------------------------------------------
  
          // Draw
          //----------------------------------------------------------------------------------
          // Draw everything in the render texture, note this will not be rendered on screen, yet
          BeginTextureMode(target);
              ClearBackground(RAYWHITE);  // Clear render texture background color
  
              for (int i = 0; i < 10; i++) DrawRectangle(0, (gameScreenHeight/10)*i, gameScreenWidth, gameScreenHeight/10, colors[i]);
  
              DrawText("If executed inside a window,\nyou can resize the window,\nand see the screen scaling!", 10, 25, 20, WHITE);
              DrawText(TextFormat("Default Mouse: [%i , %i]", (int)mouse.x, (int)mouse.y), 350, 25, 20, GREEN);
              DrawText(TextFormat("Virtual Mouse: [%i , %i]", (int)virtualMouse.x, (int)virtualMouse.y), 350, 55, 20, YELLOW);
          EndTextureMode();
          
          BeginDrawing();
              ClearBackground(BLACK);     // Clear screen background
  
              // Draw render texture to screen, properly scaled
              DrawTexturePro(target.texture, (Rectangle){ 0.0f, 0.0f, (float)target.texture.width, (float)-target.texture.height },
                             (Rectangle){ (GetScreenWidth() - ((float)gameScreenWidth*scale))*0.5f, (GetScreenHeight() - ((float)gameScreenHeight*scale))*0.5f,
                             (float)gameScreenWidth*scale, (float)gameScreenHeight*scale }, (Vector2){ 0, 0 }, 0.0f, WHITE);
          EndDrawing();
          //--------------------------------------------------------------------------------------
      }
  
      // De-Initialization
      //--------------------------------------------------------------------------------------
      UnloadRenderTexture(target);        // Unload render texture
  
      RLCloseWindow();                      // Close window and OpenGL context
      //--------------------------------------------------------------------------------------
  
      return 0;
  }
  