SYNOPSIS
#include "SDL.h"
int SDL_Flip(SDL_Surface *screen);
DESCRIPTION
On hardware that supports double-buffering, this function sets up a flip and returns. The hardware will wait for vertical retrace, and then swap video buffers before the next video surface blit or lock will return. On hardware that doesn't support double-buffering, this is equivalent to calling SDL_UpdateRect(screen, 0, 0, 0, 0)
The SDL_DOUBLEBUF flag must have been passed to SDL_SetVideoMode, when setting the video mode for this function to perform hardware flipping.
RETURN VALUE
This function returns 0 if successful, or -1 if there was an error.