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61 lines
2.6 KiB
Groff
61 lines
2.6 KiB
Groff
.TH "SDL_BlitSurface" "3" "Sun 10 Jun 2001, 19:41" "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, Sun 10 Jun 2001, 19:41
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