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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_JoyBallEvent</TITLE
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><H1
><A
NAME="SDLJOYBALLEVENT"
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>SDL_JoyBallEvent</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN4396"
></A
><H2
>Name</H2
>SDL_JoyBallEvent&nbsp;--&nbsp;Joystick trackball motion event structure</DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN4399"
></A
><H2
>Structure Definition</H2
><PRE
CLASS="PROGRAMLISTING"
>typedef struct{
  Uint8 type;
  Uint8 which;
  Uint8 ball;
  Sint16 xrel, yrel;
} SDL_JoyBallEvent;</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN4402"
></A
><H2
>Structure Data</H2
><DIV
CLASS="INFORMALTABLE"
><A
NAME="AEN4404"
></A
><P
></P
><TABLE
BORDER="0"
CLASS="CALSTABLE"
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>type</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_JOYBALLMOTION</TT
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>which</I
></TT
></TD
><TD
ALIGN="LEFT"
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>Joystick device index</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>ball</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Joystick trackball index</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>xrel</I
></TT
>, <TT
CLASS="STRUCTFIELD"
><I
>yrel</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>The relative motion in the X/Y direction</TD
></TR
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><P
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><DIV
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><A
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></A
><H2
>Description</H2
><P
><SPAN
CLASS="STRUCTNAME"
>SDL_JoyBallEvent</SPAN
> is a member of the <A
HREF="sdlevent.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_Event</SPAN
></A
> union and is used when an event of type <TT
CLASS="LITERAL"
>SDL_JOYBALLMOTION</TT
> is reported.</P
><P
>A <TT
CLASS="LITERAL"
>SDL_JOYBALLMOTION</TT
> event occurs when a user moves a trackball on the joystick. The field <TT
CLASS="STRUCTFIELD"
><I
>which</I
></TT
> is the index of the joystick that reported the event and <TT
CLASS="STRUCTFIELD"
><I
>ball</I
></TT
> is the index of the trackball (for a more detailed explaination see the <A
HREF="joystick.html"
>Joystick section</A
>). Trackballs only return relative motion, this is the change in position on the ball since it was last polled (last cycle of the event loop) and it is stored in <TT
CLASS="STRUCTFIELD"
><I
>xrel</I
></TT
> and <TT
CLASS="STRUCTFIELD"
><I
>yrel</I
></TT
>.</P
></DIV
><DIV
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><A
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></A
><H2
>See Also</H2
><P
><A
HREF="sdlevent.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_Event</SPAN
></A
>,
<A
HREF="joystick.html"
>Joystick Functions</A
>,
<A
HREF="sdljoystickeventstate.html"
><TT
CLASS="FUNCTION"
>SDL_JoystickEventState</TT
></A
>,
<A
HREF="sdljoystickgetball.html"
><TT
CLASS="FUNCTION"
>SDL_JoystickGetBall</TT
></A
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