.SH "SYNOPSIS"

.PP

\fB#include "SDL\&.h"

.sp

\fBint \fBSDL_BlitSurface\fP\fR(\fBSDL_Surface *src, SDL_Rect *srcrect, SDL_Surface *dst, SDL_Rect *dstrect\fR);

.SH "DESCRIPTION"

.PP

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

.PP

Only the position is used in the \fBdstrect\fR (the width and height are ignored)\&.

.PP

If either \fBsrcrect\fR or \fBdstrect\fR are \fBNULL\fP, the entire surface (\fBsrc\fR or \fBdst\fR) is copied\&.

.PP

The final blit rectangle is saved in \fBdstrect\fR after all clipping is performed (\fBsrcrect\fR is not modified)\&.

.PP

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

.PP

The results of blitting operations vary greatly depending on whether \fBSDL_SRCAPLHA\fP is set or not\&. See \fISDL_SetAlpha\fR 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\&.

.PP

.nf

\f(CWif (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

}\fR

.fi

.PP

.SH "RETURN VALUE"

.PP

If the blit is successful, it returns \fB0\fR, otherwise it returns \fB-1\fR\&.

.PP

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

.PP

.nf

\f(CW while ( SDL_BlitSurface(image, imgrect, screen, dstrect) == -2 ) {

while ( SDL_LockSurface(image)) < 0 )

Sleep(10);

-- Write image pixels to image->pixels --

SDL_UnlockSurface(image);

}\fR

.fi

.PP

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\&.

.SH "SEE ALSO"

.PP

\fI\fBSDL_LockSurface\fP\fR, \fI\fBSDL_FillRect\fP\fR, \fI\fBSDL_Surface\fR\fR, \fI\fBSDL_Rect\fR\fR