title: How to get a transparent SDL_Surface?
body: <p>I'm trying to get a transparent SDL_Surface (to blit translucent rectangles on it), and here's what I've done:</p>
  
  <pre><code>surface := SDL_CreateRGBSurface(SDL_SWSURFACE, XMAX*TILE_SIZE,
  YMAX*TILE_SIZE, BPP, 0, 0, 0, SDL_ALPHA_TRANSPARENT);
  SDL_FillRect(surface, nil, SDL_MapRGBA(surface^.format, 0, 0, 0, 0));
  </code></pre>
  
  <p>This still doesn't work, the surface I get is black instead of being transparent. Any idea?</p>
  
  <p>BONUS: To avoid the blitting of multiple translucide rectangles on top of each other, is there any way I can remove these rectangles then blit the new one (without blitting again the background ...) ?</p>