Mercurial > sdl-ios-xcode
view docs/man3/SDL_MapRGB.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 |
line wrap: on
line source
.TH "SDL_MapRGB" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" .SH "NAME" SDL_MapRGB\- Map a RGB color value to a pixel format\&. .SH "SYNOPSIS" .PP \fB#include "SDL\&.h" .sp \fBUint32 \fBSDL_MapRGB\fP\fR(\fBSDL_PixelFormat *fmt, Uint8 r, Uint8 g, Uint8 b\fR); .SH "DESCRIPTION" .PP Maps the RGB color value to the specified pixel format and returns the pixel value as a 32-bit int\&. .PP If the format has a palette (8-bit) the index of the closest matching color in the palette will be returned\&. .PP If the specified pixel format has an alpha component it will be returned as all 1 bits (fully opaque)\&. .SH "RETURN VALUE" .PP A pixel value best approximating the given RGB color value for a given pixel format\&. If the pixel format bpp (color depth) is less than 32-bpp then the unused upper bits of the return value can safely be ignored (e\&.g\&., with a 16-bpp format the return value can be assigned to a \fBUint16\fP, and similarly a \fBUint8\fP for an 8-bpp format)\&. .SH "SEE ALSO" .PP \fI\fBSDL_GetRGB\fP\fR, \fI\fBSDL_GetRGBA\fP\fR, \fI\fBSDL_MapRGBA\fP\fR, \fI\fBSDL_PixelFormat\fR\fR ...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01