I don't want to clutter up the other thread, so I made a new one just for this topic. Can I please get an explanation of making a 'global' double buffer? I'm having trouble visualising the implementation.

From what I've been able to gather and as it's been pointed out, my code is creating / destroying the bitmap used as the buffer each time the DrawMain() function gets called. I've come up with the following; modified from my previous attempt. Going by my understanding, I put hdcBuffer = CreateCompatibleDC( hdc ); and destroy the buffer on exit.

If I still haven't gotten it right, I want to know! ?

HDC hdc;
HDC hdcMem;
HDC hdcBuffer;
HBITMAP hbmBuffer;
HBITMAP hbmOldBuffer;
PAINTSTRUCT ps;
RECT rcClient;

Globals at the top of the program.

void DrawMain( HDC hdc, RECT* rcClient )
{
  hbmBuffer    = CreateCompatibleBitmap( hdc, rcClient->right, rcClient->bottom );
  hbmOldBuffer = (HBITMAP)SelectObject( hdcBuffer, hbmBuffer );

  FillRect(hdcBuffer, rcClient, (HBRUSH)GetStockObject(WHITE_BRUSH));

  // title
  SelectObject( hdcMem, g_hbmTitle ); //not sure if HBITMAP hbmOld = (HBITMAP) is necessary as the program works without it
  TransparentBlt( hdcBuffer, 50, 24, 297, 39, hdcMem, 0, 0, 297, 39, RGB( 255, 0, 255 ) );
   // background
  SelectObject( hdcMem, g_hbmBackground );
  TransparentBlt( hdcBuffer, 112, 90, 186, 91, hdcMem, 0, 0, 186, 91, RGB( 255, 0, 255 ) );

  // sprite
  HBITMAP hbmOld3 = (HBITMAP)SelectObject( hdcMem, g_hbmSprite );
  TransparentBlt( hdcBuffer, Sprite_Slow.x+(Sprite_Slow.amplitude*sin(Sprite_Slow.angle)+0.5), Sprite_Slow.y,15, 15 , hdcMem, 15*(frames%28), 0, 15, 15, RGB( 255, 0, 255 )) ;

  // blit double buffer to window
  BitBlt( hdc, 0, 0, rcClient->right, rcClient->bottom, hdcBuffer, 0, 0, SRCCOPY );

  SelectObject( hdcMem, hbmOld3 );
  DeleteDC( hdcMem );
}

The updated DrawMain() function.

 case WM_PAINT:
      {
        hdc = BeginPaint( hwnd, &ps );

        GetClientRect( hwnd, &rcClient );
        hdcBuffer    = CreateCompatibleDC( hdc );
        hdcMem       = CreateCompatibleDC( hdc );

        dw_timestart = timeGetTime();

        DrawMain( hdc, &rcClient );
        AnimateFrames ();
        UpdateSpritePosition();

        dw_timestop = timeGetTime();
        EndPaint( hwnd, &ps );

        f_cycle_t = dw_timestop - dw_timestart;
      }
      return 0;

The updated WM_PAINT message.

case WM_DESTROY:

      SelectObject( hdcBuffer, hbmOldBuffer );
      DeleteDC( hdcBuffer );
      DeleteObject( hbmBuffer );
      DeleteObject( g_hbmSprite );
      DeleteObject( g_hbmTitle );
      DeleteObject( g_hbmBackground );

      PostQuitMessage( 0 );
      return 0;

How I'm destroying the bitmap. The program freezes after a few moments.

@Shaarigan

Hello Shaarigan.

Thank you for your reply. I am using C and GDI for this project. I'm afraid I know barely anything about .NET and have never used C# so much of this goes over my head! I'm guessing that the method for achieving the same things in GDI+ is similar, within reason.

I do have a question about performance. My program uses between 27 and 34% CPU, but nothing extremely demanding is going on. Is this normal? The GDI Objects column also shows the number of objects changing intermittently between 14 and 18. I'm wondering if something is leaking/not being released correctly.

I have made some progress on the initial problem, however one thing puzzling me is why the code deleting the DC and Object has to be within the DrawMain() function. If I put it in WM_DESTROY, I get a blank window.

void DrawMain()
{
  SelectObject( hdcMem, g_hbmTitle ); //not sure if HBITMAP hbmOld = (HBITMAP) is necessary
  TransparentBlt( hdcBuffer, 50, 24, 297, 39, hdcMem, 0, 0, 297, 39, RGB( 255, 0, 255 ) );

  SelectObject( hdcMem, g_hbmBackground );
  TransparentBlt( hdcBuffer, 112, 90, 186, 91, hdcMem, 0, 0, 186, 91, RGB( 255, 0, 255 ) );

  SelectObject( hdcMem, g_hbmSprite );
  TransparentBlt( hdcBuffer, Sprite_Slow.x+(Sprite_Slow.amplitude*sin(Sprite_Slow.angle)+0.5),
  Sprite_Slow.y,15, 15 , hdcMem, 15*(frames%28), 0, 15, 15, RGB( 255, 0, 255 )) ;

  // blit double buffer to window
  BitBlt( hdc, 0, 0, WINDOW_WIDTH, WINDOW_HEIGHT, hdcBuffer, 0, 0, SRCCOPY );

  // This code gives produces a blank window when placed in WM_DESTROY
  DeleteDC( hdcMem );
  SelectObject( hdcBuffer, hbmOldBuffer );
  DeleteDC( hdcBuffer );
  DeleteObject( hbmBuffer );
}

    case WM_PAINT:
      {
        hdc = BeginPaint( hwnd, &ps );

        GetClientRect( hwnd, &rcClient );
        hdcBuffer    = CreateCompatibleDC( hdc );
        hdcMem       = CreateCompatibleDC( hdc );

        dw_timestart = timeGetTime();

        hbmBuffer    = CreateCompatibleBitmap( hdc, WINDOW_WIDTH, WINDOW_HEIGHT );
        hbmOldBuffer = (HBITMAP)SelectObject( hdcBuffer, hbmBuffer );
        FillRect(hdcBuffer, &rcClient, (HBRUSH)GetStockObject(WHITE_BRUSH));

        DrawMain();
        DrawBackroundBrush(); //placeholder for drawing effect
        AnimateFrames ();
        UpdateSpritePosition();

        dw_timestop = timeGetTime();
        EndPaint( hwnd, &ps );

        f_cycle_t = dw_timestop - dw_timestart;
      }
      return 0;

I've moved all the DC creation to WM_PAINT and the functions don't need any parameters, unlike before.

case WM_DESTROY:

      DeleteObject( g_hbmSprite );
      DeleteObject( g_hbmTitle );
      DeleteObject( g_hbmBackground );

      PostQuitMessage( 0 );
      return 0;

@Shaarigan

I have taken a look at the links but it will take a while before I can make much sense of it as a whole. Currently I'm just modifying the program step by step to see how it affects the performance. Visibly nothing is different. Thanks for your input, I will read up on WM_PAINT and hopefully find out what's going on.

I am deleting the objects on program exit, but maybe not giving the memory back to the system.. I will take your advice and examine the calls to WM_PAINT.