| .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 |
