| e14743d1 |
1 | .TH "SDL_BlitSurface" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" |
| 2 | .SH "NAME" |
| 3 | SDL_BlitSurface \- This performs a fast blit from the source surface to the destination surface\&. |
| 4 | .SH "SYNOPSIS" |
| 5 | .PP |
| 6 | \fB#include "SDL\&.h" |
| 7 | .sp |
| 8 | \fBint \fBSDL_BlitSurface\fP\fR(\fBSDL_Surface *src, SDL_Rect *srcrect, SDL_Surface *dst, SDL_Rect *dstrect\fR); |
| 9 | .SH "DESCRIPTION" |
| 10 | .PP |
| 11 | This performs a fast blit from the source surface to the destination surface\&. |
| 12 | .PP |
| 13 | Only the position is used in the \fBdstrect\fR (the width and height are ignored)\&. |
| 14 | .PP |
| 15 | If either \fBsrcrect\fR or \fBdstrect\fR are \fBNULL\fP, the entire surface (\fBsrc\fR or \fBdst\fR) is copied\&. |
| 16 | .PP |
| 17 | The final blit rectangle is saved in \fBdstrect\fR after all clipping is performed (\fBsrcrect\fR is not modified)\&. |
| 18 | .PP |
| 19 | The blit function should not be called on a locked surface\&. |
| 20 | .PP |
| 21 | 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\&. |
| 22 | .PP |
| 23 | .nf |
| 24 | \f(CWif (source surface has SDL_SRCALPHA set) { |
| 25 | if (source surface has alpha channel (that is, format->Amask != 0)) |
| 26 | blit using per-pixel alpha, ignoring any colour key |
| 27 | else { |
| 28 | if (source surface has SDL_SRCCOLORKEY set) |
| 29 | blit using the colour key AND the per-surface alpha value |
| 30 | else |
| 31 | blit using the per-surface alpha value |
| 32 | } |
| 33 | } else { |
| 34 | if (source surface has SDL_SRCCOLORKEY set) |
| 35 | blit using the colour key |
| 36 | else |
| 37 | ordinary opaque rectangular blit |
| 38 | }\fR |
| 39 | .fi |
| 40 | .PP |
| 41 | .SH "RETURN VALUE" |
| 42 | .PP |
| 43 | If the blit is successful, it returns \fB0\fR, otherwise it returns \fB-1\fR\&. |
| 44 | .PP |
| 45 | 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: |
| 46 | .PP |
| 47 | .nf |
| 48 | \f(CW while ( SDL_BlitSurface(image, imgrect, screen, dstrect) == -2 ) { |
| 49 | while ( SDL_LockSurface(image)) < 0 ) |
| 50 | Sleep(10); |
| 51 | -- Write image pixels to image->pixels -- |
| 52 | SDL_UnlockSurface(image); |
| 53 | }\fR |
| 54 | .fi |
| 55 | .PP |
| 56 | 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\&. |
| 57 | .SH "SEE ALSO" |
| 58 | .PP |
| 59 | \fI\fBSDL_LockSurface\fP\fR, \fI\fBSDL_FillRect\fP\fR, \fI\fBSDL_Surface\fR\fR, \fI\fBSDL_Rect\fR\fR |
| 60 | .\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01 |
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