Mercurial > sdl-ios-xcode
annotate 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> |
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date | Wed, 15 Mar 2006 15:47:49 +0000 |
parents | e5bc29de3f0a |
children | 546f7c1eb755 |
rev | line source |
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181
e5bc29de3f0a
Updated from the SDL Documentation Project
Sam Lantinga <slouken@libsdl.org>
parents:
55
diff
changeset
|
1 .TH "SDL_MapRGB" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" |
0 | 2 .SH "NAME" |
3 SDL_MapRGB\- Map a RGB color value to a pixel format\&. | |
4 .SH "SYNOPSIS" | |
5 .PP | |
6 \fB#include "SDL\&.h" | |
7 .sp | |
8 \fBUint32 \fBSDL_MapRGB\fP\fR(\fBSDL_PixelFormat *fmt, Uint8 r, Uint8 g, Uint8 b\fR); | |
9 .SH "DESCRIPTION" | |
10 .PP | |
11 Maps the RGB color value to the specified pixel format and returns the pixel value as a 32-bit int\&. | |
12 .PP | |
13 If the format has a palette (8-bit) the index of the closest matching color in the palette will be returned\&. | |
14 .PP | |
15 If the specified pixel format has an alpha component it will be returned as all 1 bits (fully opaque)\&. | |
16 .SH "RETURN VALUE" | |
17 .PP | |
18 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)\&. | |
19 .SH "SEE ALSO" | |
20 .PP | |
21 \fI\fBSDL_GetRGB\fP\fR, \fI\fBSDL_GetRGBA\fP\fR, \fI\fBSDL_MapRGBA\fP\fR, \fI\fBSDL_PixelFormat\fR\fR | |
181
e5bc29de3f0a
Updated from the SDL Documentation Project
Sam Lantinga <slouken@libsdl.org>
parents:
55
diff
changeset
|
22 ...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01 |