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view docs/man3/SDL_FillRect.3 @ 1544:ab1e4c41ab71
Fixed bug #33
Mike Frysinger wrote:
> with libsdl-1.2.9, some games (like bomberclone) started
> segfaulting in Gentoo
[...snip...]
> the last change in the last hunk:
[...snip...]
> if i change the statement to read:
> (table[which].blit_features & GetBlitFeatures()) == GetBlitFeatures()
> bomberclone no longer segfaults on my box
Alex Volkov wrote:
> The test "(table[which].blit_features & GetBlitFeatures()) ==
> table[which].blit_features)" is correct, and the previous
> "(table[which].cpu_mmx == SDL_HasMMX())" was actually broken.
I think there is potentially a slightly different cause of the above problem.
During the introduction of the Altivec code, the blit_table struct field
'alpha' got changed from a straightforward enum to a bitmask, which makes
perfect sense by itself. However, now the table driven blitter selection code
in SDL_CalculateBlitN() can choose the wrong blitters when searching for a
NO_ALPHA blitter because of the following code:
int a_need = 0;
...
(a_need & table[which].alpha) == a_need &&
When searching through the normal_blit_2[] table, a SET_ALPHA blitter (like
Blit_RGB565_ARGB8888) can now be selected instead of a NO_ALPHA one, causing
alpha channel bits to appear in a non-alpha destination surface. I suppose this
could theoretically be an indirect cause of the segfault mentioned above.
I *think* this can be fixed by changing to
int a_need = NO_ALPHA;
author | Sam Lantinga <slouken@libsdl.org> |
---|---|
date | Wed, 15 Mar 2006 15:47:49 +0000 |
parents | e5bc29de3f0a |
children | 546f7c1eb755 |
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.TH "SDL_FillRect" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" .SH "NAME" SDL_FillRect\- This function performs a fast fill of the given rectangle with some color .SH "SYNOPSIS" .PP \fB#include "SDL\&.h" .sp \fBint \fBSDL_FillRect\fP\fR(\fBSDL_Surface *dst, SDL_Rect *dstrect, Uint32 color\fR); .SH "DESCRIPTION" .PP This function performs a fast fill of the given rectangle with \fBcolor\fR\&. If \fBdstrect\fR is \fBNULL\fP, the whole surface will be filled with \fBcolor\fR\&. .PP The color should be a pixel of the format used by the surface, and can be generated by the \fISDL_MapRGB\fR or \fISDL_MapRGBA\fR functions\&. If the color value contains an alpha value then the destination is simply "filled" with that alpha information, no blending takes place\&. .PP If there is a clip rectangle set on the destination (set via \fISDL_SetClipRect\fR) then this function will clip based on the intersection of the clip rectangle and the \fBdstrect\fR rectangle and the dstrect rectangle will be modified to represent the area actually filled\&. .SH "RETURN VALUE" .PP This function returns \fB0\fR on success, or \fB-1\fR on error\&. .SH "SEE ALSO" .PP \fI\fBSDL_MapRGB\fP\fR, \fI\fBSDL_MapRGBA\fP\fR, \fI\fBSDL_BlitSurface\fP\fR, \fI\fBSDL_Rect\fR\fR ...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01