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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
><HEAD
><TITLE
>SDL_Overlay</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
"><LINK
REL="HOME"
TITLE="SDL Library Documentation"
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><HR
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><H1
><A
NAME="SDLOVERLAY"
></A
>SDL_Overlay</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN3464"
></A
><H2
>Name</H2
>SDL_Overlay&nbsp;--&nbsp;YUV video overlay</DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN3467"
></A
><H2
>Structure Definition</H2
><PRE
CLASS="PROGRAMLISTING"
>typedef struct{
  Uint32 format;
  int w, h;
  int planes;
  Uint16 *pitches;
  Uint8 **pixels;
  Uint32 hw_overlay:1;
} SDL_Overlay;</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN3470"
></A
><H2
>Structure Data</H2
><DIV
CLASS="INFORMALTABLE"
><A
NAME="AEN3472"
></A
><P
></P
><TABLE
BORDER="0"
CLASS="CALSTABLE"
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>format</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Overlay format (see below)</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>w, h</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Width and height of overlay</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>planes</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Number of planes in the overlay. Usually either 1 or 3</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>pitches</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>An array of pitches, one for each plane. Pitch is the length of a row in bytes.</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>pixels</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>An array of pointers to teh data of each plane. The overlay should be locked before these pointers are used.</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>hw_overlay</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>This will be set to 1 if the overlay is hardware accelerated.</TD
></TR
></TBODY
></TABLE
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN3499"
></A
><H2
>Description</H2
><P
>A <SPAN
CLASS="STRUCTNAME"
>SDL_Overlay</SPAN
> is similar to a <A
HREF="sdlsurface.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_Surface</SPAN
></A
> except it stores a YUV overlay. All the fields are read only, except for <TT
CLASS="STRUCTFIELD"
><I
>pixels</I
></TT
> which should be <A
HREF="sdllockyuvoverlay.html"
>locked</A
> before use. The <TT
CLASS="STRUCTFIELD"
><I
>format</I
></TT
> field stores the format of the overlay which is one of the following:
<PRE
CLASS="PROGRAMLISTING"
>#define SDL_YV12_OVERLAY  0x32315659  /* Planar mode: Y + V + U */
#define SDL_IYUV_OVERLAY  0x56555949  /* Planar mode: Y + U + V */
#define SDL_YUY2_OVERLAY  0x32595559  /* Packed mode: Y0+U0+Y1+V0 */
#define SDL_UYVY_OVERLAY  0x59565955  /* Packed mode: U0+Y0+V0+Y1 */
#define SDL_YVYU_OVERLAY  0x55595659  /* Packed mode: Y0+V0+Y1+U0 */</PRE
>
More information on YUV formats can be found at <A
HREF="http://www.webartz.com/fourcc/indexyuv.htm"
TARGET="_top"
>http://www.webartz.com/fourcc/indexyuv.htm</A
>.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN3510"
></A
><H2
>See Also</H2
><P
><A
HREF="sdlcreateyuvoverlay.html"
><TT
CLASS="FUNCTION"
>SDL_CreateYUVOverlay</TT
></A
>,
<A
HREF="sdllockyuvoverlay.html"
><TT
CLASS="FUNCTION"
>SDL_LockYUVOverlay</TT
></A
>,
<A
HREF="sdlunlockyuvoverlay.html"
><TT
CLASS="FUNCTION"
>SDL_UnlockYUVOverlay</TT
></A
>,
<A
HREF="sdlfreeyuvoverlay.html"
><TT
CLASS="FUNCTION"
>SDL_FreeYUVOverlay</TT
></A
></P
></DIV
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