SDL_BlitSurface(3) SDL API Reference SDL_BlitSurface(3)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 sur-
face.
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. Col-
orkeying 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
SDL Tue 11 Sep 2001, 23:01 SDL_BlitSurface(3)
