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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 |