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view docs/man3/SDL_SetColorKey.3 @ 3899:081aecdb0911 SDL-1.2
From: Gabriel Gambetta
To: SDL Mailing List <sdl@libsdl.org>
Date: Fri, 17 Nov 2006 00:39:29 -0200
Subject: [SDL] Alpha blending bug - fixed?
It turns out mm5 never got the correct value. This failed :
[...]
"movd %1, %%mm5\n\t"
: : "m" (amask), "m" (sf->Ashift) );
mm5 got 0xFF000018 instead of 0x00000018. However I did this :
Uint32 ashift = sf->Ashift;
[...]
"movd %1, %%mm5\n\t"
: : "m" (amask), "m" (ashift) );
and everything worked fine.
The only thing I could find out was that ashift is 32-bit aligned but
sf->Ashift isn't:
printf("ashift %8X [%d]\n", &ashift, (int)(&ashift) % 4);
printf("sf->Ashift %8X [%d]\n", &sf->Ashift, (int)(&sf->Ashift) % 4);
ashift at BFF0E0C4 [0]
sf->Ashift at 08AFB9CD [1]
Could this be the problem? If it is, the fix is extremely trivial.
Should I submit a patch?
--Gabriel
author | Ryan C. Gordon <icculus@icculus.org> |
---|---|
date | Tue, 21 Nov 2006 23:17:00 +0000 |
parents | e5bc29de3f0a |
children | 546f7c1eb755 |
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.TH "SDL_SetColorKey" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" .SH "NAME" SDL_SetColorKey\- Sets the color key (transparent pixel) in a blittable surface and RLE acceleration\&. .SH "SYNOPSIS" .PP \fB#include "SDL\&.h" .sp \fBint \fBSDL_SetColorKey\fP\fR(\fBSDL_Surface *surface, Uint32 flag, Uint32 key\fR); .SH "DESCRIPTION" .PP Sets the color key (transparent pixel) in a blittable surface and enables or disables RLE blit acceleration\&. .PP RLE acceleration can substantially speed up blitting of images with large horizontal runs of transparent pixels (i\&.e\&., pixels that match the \fBkey\fR value)\&. The \fBkey\fR must be of the same pixel format as the \fBsurface\fR, \fI\fBSDL_MapRGB\fP\fR is often useful for obtaining an acceptable value\&. .PP If \fBflag\fR is \fBSDL_SRCCOLORKEY\fP then \fBkey\fR is the transparent pixel value in the source image of a blit\&. .PP If \fBflag\fR is OR\&'d with \fBSDL_RLEACCEL\fP then the surface will be draw using RLE acceleration when drawn with \fISDL_BlitSurface\fR\&. The surface will actually be encoded for RLE acceleration the first time \fISDL_BlitSurface\fR or \fISDL_DisplayFormat\fR is called on the surface\&. .PP If \fBflag\fR is 0, this function clears any current color key\&. .SH "RETURN VALUE" .PP This function returns \fB0\fR, or \fB-1\fR if there was an error\&. .SH "SEE ALSO" .PP \fI\fBSDL_BlitSurface\fP\fR, \fI\fBSDL_DisplayFormat\fP\fR, \fI\fBSDL_MapRGB\fP\fR, \fI\fBSDL_SetAlpha\fP\fR ...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01