annotate docs/man3/SDL_BlitSurface.3 @ 1856:21f13c787b46

Date: Mon, 22 May 2006 01:16:47 -0400 From: Mike Frysinger Subject: [SDL] [patch] fix sed expression in sdl-config just noticed that sdl-config uses '[a-z]' with sed in sdl-config without forcing the locale to C ... this could cause problems with locales where the letter 'z' is not the last letter in the alphabet
author Sam Lantinga <slouken@libsdl.org>
date Tue, 23 May 2006 15:07:56 +0000
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rev   line source
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1 .TH "SDL_BlitSurface" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference"
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2 .SH "NAME"
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3 SDL_BlitSurface\- This performs a fast blit from the source surface to the destination surface\&.
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4 .SH "SYNOPSIS"
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5 .PP
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6 \fB#include "SDL\&.h"
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7 .sp
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8 \fBint \fBSDL_BlitSurface\fP\fR(\fBSDL_Surface *src, SDL_Rect *srcrect, SDL_Surface *dst, SDL_Rect *dstrect\fR);
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9 .SH "DESCRIPTION"
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10 .PP
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11 This performs a fast blit from the source surface to the destination surface\&.
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12 .PP
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13 Only the position is used in the \fBdstrect\fR (the width and height are ignored)\&.
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14 .PP
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15 If either \fBsrcrect\fR or \fBdstrect\fR are \fBNULL\fP, the entire surface (\fBsrc\fR or \fBdst\fR) is copied\&.
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16 .PP
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17 The final blit rectangle is saved in \fBdstrect\fR after all clipping is performed (\fBsrcrect\fR is not modified)\&.
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18 .PP
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19 The blit function should not be called on a locked surface\&.
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20 .PP
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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\&.
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22 .PP
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23 .nf
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24 \f(CWif (source surface has SDL_SRCALPHA set) {
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25 if (source surface has alpha channel (that is, format->Amask != 0))
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26 blit using per-pixel alpha, ignoring any colour key
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27 else {
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28 if (source surface has SDL_SRCCOLORKEY set)
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29 blit using the colour key AND the per-surface alpha value
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30 else
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31 blit using the per-surface alpha value
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32 }
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33 } else {
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34 if (source surface has SDL_SRCCOLORKEY set)
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35 blit using the colour key
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36 else
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37 ordinary opaque rectangular blit
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38 }\fR
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39 .fi
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40 .PP
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41 .SH "RETURN VALUE"
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42 .PP
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43 If the blit is successful, it returns \fB0\fR, otherwise it returns \fB-1\fR\&.
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44 .PP
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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:
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46 .PP
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47 .nf
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48 \f(CW while ( SDL_BlitSurface(image, imgrect, screen, dstrect) == -2 ) {
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49 while ( SDL_LockSurface(image)) < 0 )
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50 Sleep(10);
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51 -- Write image pixels to image->pixels --
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52 SDL_UnlockSurface(image);
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53 }\fR
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54 .fi
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55 .PP
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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\&.
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57 .SH "SEE ALSO"
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58 .PP
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59 \fI\fBSDL_LockSurface\fP\fR, \fI\fBSDL_FillRect\fP\fR, \fI\fBSDL_Surface\fR\fR, \fI\fBSDL_Rect\fR\fR
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60 ...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01