NAME

       SDL_BlitSurface  -  This  performs  a fast blit from the source surface to the destination
       surface.

SYNOPSIS

       #include "SDL.h"

       int  SDL_BlitSurface(SDL_Surface  *src,  SDL_Rect  *srcrect,  SDL_Surface  *dst,  SDL_Rect
       *dstrect);

DESCRIPTION

       This performs a fast blit from the source surface to the destination surface.

       Only the position is used in the dstrect (the width and height are ignored).

       If either srcrect or dstrect are NULL, the entire surface (src or dst) is copied.

       The  final  blit rectangle is saved in dstrect after all clipping is performed (srcrect is
       not modified).

       The blit function should not be called on a locked surface.

       The results of blitting operations vary greatly depending on whether SDL_SRCAPLHA  is  set
       or not. See SDL_SetAlpha for an explaination of how this affects your results. Colorkeying
       and alpha attributes also interact with surface blitting,  as  the  following  pseudo-code
       should hopefully explain.

       if (source surface has SDL_SRCALPHA set) {
           if (source surface has alpha channel (that is, format->Amask != 0))
               blit using per-pixel alpha, ignoring any colour key
           else {
               if (source surface has SDL_SRCCOLORKEY set)
                   blit using the colour key AND the per-surface alpha value
               else
                   blit using the per-surface alpha value
           }
       } else {
           if (source surface has SDL_SRCCOLORKEY set)
               blit using the colour key
           else
               ordinary opaque rectangular blit
       }

RETURN VALUE

       If the blit is successful, it returns 0, otherwise it returns -1.

       If  either of the surfaces were in video memory, and the blit returns -2, the video memory
       was lost, so it should be reloaded with artwork and re-blitted:

               while ( SDL_BlitSurface(image, imgrect, screen, dstrect) == -2 ) {
                       while ( SDL_LockSurface(image)) < 0 )
                               Sleep(10);
                       -- Write image pixels to image->pixels --
                       SDL_UnlockSurface(image);
               }

        This happens under DirectX 5.0  when  the  system  switches  away  from  your  fullscreen
       application.  Locking the surface will also fail until you have access to the video memory
       again.

SEE ALSO

       SDL_LockSurface, SDL_FillRect, SDL_Surface, SDL_Rect