Mercurial > sdl-ios-xcode
view docs/man3/SDL_BlitSurface.3 @ 2866:e532417a6977
Fixed SDL 1.2 compatibility problem.
The API specifies that SDL_OpenAudio() will fill out the 'desired' audio spec
with the correct samples and size set by the driver. This value is important
since it may be used by applications that size audio buffers, etc.
However, we want to allow advanced applications to call SDL_OpenAudioDevice()
which gets passed a const 'desired' parameter, and have the correct data filled
into the 'obtained' parameter, possibly allowing or not allowing format changes.
So... 'obtained' becomes the audio format the user callback is expected to use,
and we add flags to allow the application to specify which format changes are
allowed.
Note: We really need to add a way to query the 'obtained' audio spec.
author | Sam Lantinga <slouken@libsdl.org> |
---|---|
date | Sat, 13 Dec 2008 06:36:47 +0000 |
parents | 546f7c1eb755 |
children | 1238da4a7112 |
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.TH "SDL_BlitSurface" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" .SH "NAME" SDL_BlitSurface \- This performs a fast blit from the source surface to the destination surface\&. .SH "SYNOPSIS" .PP \fB#include "SDL\&.h" .sp \fBint \fBSDL_BlitSurface\fP\fR(\fBSDL_Surface *src, SDL_Rect *srcrect, SDL_Surface *dst, SDL_Rect *dstrect\fR); .SH "DESCRIPTION" .PP This performs a fast blit from the source surface to the destination surface\&. .PP Only the position is used in the \fBdstrect\fR (the width and height are ignored)\&. .PP If either \fBsrcrect\fR or \fBdstrect\fR are \fBNULL\fP, the entire surface (\fBsrc\fR or \fBdst\fR) is copied\&. .PP The final blit rectangle is saved in \fBdstrect\fR after all clipping is performed (\fBsrcrect\fR is not modified)\&. .PP The blit function should not be called on a locked surface\&. .PP 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\&. .PP .nf \f(CWif (source surface has SDL_SRCALPHA set) { if (source surface has alpha channel (that is, format->Amask != 0)) blit using per-pixel alpha, ignoring any colour key else { if (source surface has SDL_SRCCOLORKEY set) blit using the colour key AND the per-surface alpha value else blit using the per-surface alpha value } } else { if (source surface has SDL_SRCCOLORKEY set) blit using the colour key else ordinary opaque rectangular blit }\fR .fi .PP .SH "RETURN VALUE" .PP If the blit is successful, it returns \fB0\fR, otherwise it returns \fB-1\fR\&. .PP 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: .PP .nf \f(CW while ( SDL_BlitSurface(image, imgrect, screen, dstrect) == -2 ) { while ( SDL_LockSurface(image)) < 0 ) Sleep(10); -- Write image pixels to image->pixels -- SDL_UnlockSurface(image); }\fR .fi .PP 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\&. .SH "SEE ALSO" .PP \fI\fBSDL_LockSurface\fP\fR, \fI\fBSDL_FillRect\fP\fR, \fI\fBSDL_Surface\fR\fR, \fI\fBSDL_Rect\fR\fR ...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01