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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 355632dca928
children
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<HTML
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>SDL_GetRGBA</TITLE
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>SDL_GetRGBA</H1
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><H2
>Name</H2
>SDL_GetRGBA&nbsp;--&nbsp;Get RGBA values from a pixel in the specified pixel format.</DIV
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>Synopsis</H2
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><P
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><PRE
CLASS="FUNCSYNOPSISINFO"
>#include "SDL.h"</PRE
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><CODE
><CODE
CLASS="FUNCDEF"
>void <B
CLASS="FSFUNC"
>SDL_GetRGBA</B
></CODE
>(Uint32 pixel, SDL_PixelFormat *fmt, Uint8 *r, Uint8 *g, Uint8 *b, Uint8 *a);</CODE
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><H2
>Description</H2
><P
>Get RGBA component values from a pixel stored in the specified pixel format.</P
><P
>This function uses the entire 8-bit [0..255] range when converting color
components from pixel formats with less than 8-bits per RGB component
(e.g., a completely white pixel in 16-bit RGB565 format would return
[0xff, 0xff, 0xff] not [0xf8, 0xfc, 0xf8]).</P
><P
>If the surface has no alpha component, the alpha will be returned as 0xff
(100% opaque).</P
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><A
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>SDL_GetRGB</A
>,
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>SDL_MapRGB</A
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>SDL_MapRGBA</A
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>SDL_PixelFormat</A
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