.TH "SDL_BlitSurface" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" 
.SH "NAME"
SDL_BlitSurface \- This performs a fast blit from the source surface to the destination surface\&.
.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
.\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01