// SDL_03 [SDL-OpenGL NeHe's Lesson 02].nova



// Using namespace declarations.
using Library.OpenGL;
using Library.SDL;



// The application class.
class SdlNeHeLesson02App
{
   // Application class's "main" function.
   public static void main( String[] args )
   {
      // Output the keyboard contols.
      Stream.write( "Keyboard controls:\n"
                  + "   esc = exit\n" );


      // The size of the OpenGL window.
      int WINDOW_WIDTH = 640, WINDOW_HEIGHT = 480;


      // Initialize SDL.
      if ( SDL.SDL_Init( SDL.SDL_INIT_VIDEO ) < 0 )
      {
         // Report an error if it fails.
         Stream.writeLine( "Failed initializing SDL Video: " + SDL.SDL_GetError( ) );

         // Return instead of SDL_Quit because SDL isn't yet initialized.
         return;
      }

      // Create an OpenGL screen.
      if ( SDL.SDL_SetVideoMode( WINDOW_WIDTH, WINDOW_HEIGHT, 0, SDL.SDL_OPENGL ) == null )
      {
         Stream.writeLine( "Unable to create OpenGL screen: " + SDL.SDL_GetError( ) );

         SDL.SDL_Quit( );

         return;
      }

      // Set the title bar in environments that support it.
      String caption = "SDL_03 [SDL-OpenGL NeHe's Lesson 02]";
      SDL.SDL_WM_SetCaption( caption, caption );

      // Loop, drawing and checking events.
      initGL( WINDOW_WIDTH, WINDOW_HEIGHT );

      bool done = false;
      SDL_Event event = new SDL_Event( );

      while ( !done )
      {
         drawGLScene( );

         // Inner loop to process multiple SDL events per frame.
         while ( SDL.SDL_PollEvent( event ) == 1 )
         {
            if ( event.typeID == SDL.SDL_QUIT )
            {
               done = true;
            }

            if ( event.typeID == SDL.SDL_KEYDOWN )
            {
               if ( event.key.keysym.sym == SDL.SDLK_ESCAPE )
               {
                  done = true;
               }
            }
         }
      }

      // Shutdown SDL.
      SDL.SDL_Quit( );
   }



   // A general OpenGL initialization function.
   // We call this right after our OpenGL window is created.
   private static void initGL( int width, int height )
   {
      OpenGL.glViewport( 0, 0, width, height );
      OpenGL.glClearDepth( 1.0 );                     // Enables clearing of the depth buffer.
      OpenGL.glDepthFunc( OpenGL.GL_LESS );           // The type of depth test to do.
      OpenGL.glEnable( OpenGL.GL_DEPTH_TEST );        // Enables depth testing.

      OpenGL.glMatrixMode( OpenGL.GL_PROJECTION );
      OpenGL.glLoadIdentity( );                       // Reset the projection matrix.

      // Calculate the aspect ratio of the window.
      OpenGL.gluPerspective( 45.0,
                             (double)width / (double)height,
                             0.1,
                             100.0 );

      OpenGL.glMatrixMode( OpenGL.GL_MODELVIEW );
   }



   // The main drawing function.
   private static void drawGLScene( )
   {
      // Clear the screen and the depth buffer.
      OpenGL.glClear( OpenGL.GL_COLOR_BUFFER_BIT | OpenGL.GL_DEPTH_BUFFER_BIT );

      OpenGL.glLoadIdentity( );                   // Reset the view.

      OpenGL.glTranslatef( -1.5f, 0.0f, -6.0f );  // Move left 1.5 units and into the screen 6.0 units.

      // Draw a triangle.
      OpenGL.glBegin( OpenGL.GL_POLYGON );        // Start drawing a polygon.
      OpenGL.glVertex3f(  0.0f,  1.0f, 0.0f );    // Top.
      OpenGL.glVertex3f(  1.0f, -1.0f, 0.0f );    // Bottom right.
      OpenGL.glVertex3f( -1.0f, -1.0f, 0.0f );    // Bottom left.
      OpenGL.glEnd( );                            // We're done with the polygon.

      OpenGL.glTranslatef( 3.0f, 0.0f, 0.0f );    // Move right 3 units.

      // Draw a square (quadrilateral).
      OpenGL.glBegin( OpenGL.GL_QUADS );          // Start drawing a polygon (4 sided).
      OpenGL.glVertex3f( -1.0f,  1.0f, 0.0f );    // Top left.
      OpenGL.glVertex3f(  1.0f,  1.0f, 0.0f );    // Top right.
      OpenGL.glVertex3f(  1.0f, -1.0f, 0.0f );    // Bottom right.
      OpenGL.glVertex3f( -1.0f, -1.0f, 0.0f );    // Bottom left.
      OpenGL.glEnd( );                            // Done with the polygon.

      // Swap buffers to display, since we're double buffered.
      SDL.SDL_GL_SwapBuffers( );
   }
}