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