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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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><TITLE
>SDL_SetColorKey</TITLE
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><H1
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>SDL_SetColorKey</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN2045"
></A
><H2
>Name</H2
>SDL_SetColorKey&nbsp;--&nbsp;Sets the color key (transparent pixel) in a blittable surface and
RLE acceleration.</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN2048"
></A
><H2
>Synopsis</H2
><DIV
CLASS="FUNCSYNOPSIS"
><A
NAME="AEN2049"
></A
><P
></P
><PRE
CLASS="FUNCSYNOPSISINFO"
>#include "SDL.h"</PRE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>int <B
CLASS="FSFUNC"
>SDL_SetColorKey</B
></CODE
>(SDL_Surface *surface, Uint32 flag, Uint32 key);</CODE
></P
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN2055"
></A
><H2
>Description</H2
><P
> Sets the color key (transparent pixel) in a blittable surface and enables or
 disables RLE blit acceleration.</P
><P
>RLE acceleration can substantially speed up blitting of images with large
horizontal runs of transparent pixels (i.e., pixels that match the
<TT
CLASS="PARAMETER"
><I
>key</I
></TT
> value). The <TT
CLASS="PARAMETER"
><I
>key</I
></TT
> must be of the same pixel format as the <TT
CLASS="PARAMETER"
><I
>surface</I
></TT
>, <A
HREF="sdlmaprgb.html"
><TT
CLASS="FUNCTION"
>SDL_MapRGB</TT
></A
> is often useful for obtaining an acceptable value.</P
><P
>If <TT
CLASS="PARAMETER"
><I
>flag</I
></TT
> is <TT
CLASS="LITERAL"
>SDL_SRCCOLORKEY</TT
> then
<TT
CLASS="PARAMETER"
><I
>key</I
></TT
> is the transparent pixel value in the source image of a
blit.</P
><P
>If <TT
CLASS="PARAMETER"
><I
>flag</I
></TT
> is OR'd with
<TT
CLASS="LITERAL"
>SDL_RLEACCEL</TT
> then the surface will be draw using RLE
acceleration when drawn with
<A
HREF="sdlblitsurface.html"
>SDL_BlitSurface</A
>.  The surface will
actually be encoded for RLE acceleration the first time
<A
HREF="sdlblitsurface.html"
>SDL_BlitSurface</A
> or
<A
HREF="sdldisplayformat.html"
>SDL_DisplayFormat</A
> is called on the
surface.</P
><P
>If <TT
CLASS="PARAMETER"
><I
>flag</I
></TT
> is 0, this function clears
any current color key.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN2076"
></A
><H2
>Return Value</H2
><P
>This function returns <SPAN
CLASS="RETURNVALUE"
>0</SPAN
>, or
<SPAN
CLASS="RETURNVALUE"
>-1</SPAN
> if there was an error.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN2081"
></A
><H2
>See Also</H2
><P
><A
HREF="sdlblitsurface.html"
><TT
CLASS="FUNCTION"
>SDL_BlitSurface</TT
></A
>,
<A
HREF="sdldisplayformat.html"
><TT
CLASS="FUNCTION"
>SDL_DisplayFormat</TT
></A
>,
<A
HREF="sdlmaprgb.html"
><TT
CLASS="FUNCTION"
>SDL_MapRGB</TT
></A
>,
<A
HREF="sdlsetalpha.html"
><TT
CLASS="FUNCTION"
>SDL_SetAlpha</TT
></A
></P
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