.TH "SDL_BlitSurface" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" +
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.SH "NAME"+
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SDL_BlitSurface\- This performs a fast blit from the source surface to the destination surface\&.+
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.SH "SYNOPSIS"+
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.PP+
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\fB#include "SDL\&.h"+
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.sp+
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\fBint \fBSDL_BlitSurface\fP\fR(\fBSDL_Surface *src, SDL_Rect *srcrect, SDL_Surface *dst, SDL_Rect *dstrect\fR);+
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.SH "DESCRIPTION"+
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.PP+
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This performs a fast blit from the source surface to the destination surface\&.+
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.PP+
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Only the position is used in the \fBdstrect\fR (the width and height are ignored)\&.+
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.PP+
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If either \fBsrcrect\fR or \fBdstrect\fR are \fBNULL\fP, the entire surface (\fBsrc\fR or \fBdst\fR) is copied\&.+
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.PP+
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The final blit rectangle is saved in \fBdstrect\fR after all clipping is performed (\fBsrcrect\fR is not modified)\&.+
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.PP+
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The blit function should not be called on a locked surface\&.+
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.PP+
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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\&. +
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.PP+
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.nf+
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\f(CWif (source surface has SDL_SRCALPHA set) {+
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    if (source surface has alpha channel (that is, format->Amask != 0))+
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        blit using per-pixel alpha, ignoring any colour key+
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    else {+
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        if (source surface has SDL_SRCCOLORKEY set)+
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            blit using the colour key AND the per-surface alpha value+
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        else+
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            blit using the per-surface alpha value+
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    }+
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} else {+
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    if (source surface has SDL_SRCCOLORKEY set)+
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        blit using the colour key+
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    else+
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        ordinary opaque rectangular blit+
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}\fR+
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.fi+
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.PP+
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.SH "RETURN VALUE"+
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.PP+
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If the blit is successful, it returns \fB0\fR, otherwise it returns \fB-1\fR\&.+
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.PP+
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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: +
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.PP+
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.nf+
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\f(CW        while ( SDL_BlitSurface(image, imgrect, screen, dstrect) == -2 ) {+
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                while ( SDL_LockSurface(image)) < 0 )+
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                        Sleep(10);+
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                -- Write image pixels to image->pixels --+
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                SDL_UnlockSurface(image);+
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        }\fR+
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.fi+
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.PP+
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 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\&.+
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.SH "SEE ALSO"+
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.PP+
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\fI\fBSDL_LockSurface\fP\fR, \fI\fBSDL_FillRect\fP\fR, \fI\fBSDL_Surface\fR\fR, \fI\fBSDL_Rect\fR\fR+
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...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01+
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