hi is "SDL_BlitSurface(img, &start, screen, &dest);" slower than "SDL_BlitSurface(img, NULL, screen, &dest);"? also is it faster to use switch-break than many ifs? currently i create one 4000x4000 surface and blit that to screen. RAM usage seems to be over 60mb. and fps is 100-200 (which is pretty slow, IMO). one thing i can't understand is that the program gets gradually faster when i move the 4000x4000 image outside the screen. it doesn't blit to screen if coordinates are outside resolution?

It only draws whats in the screen region, everything else is clipped. So obviously the less drawing done, the faster it runs.