[cairo] xlib bug, with testcase

[Behdad Esfahbod]

On Mon, 2008-07-14 at 16:43 -0700, Vladimir Vukicevic wrote:
> Hmm, I don't see this fix in the pixman repo -- did it get pushed up?

Doesn't seem so.

>     - Vlad
> 
> On May 28, 2008, at 11:56 AM, Behdad Esfahbod wrote:
> 
> > On Wed, 2008-05-28 at 14:25 -0400, Antoine Azar wrote:
> >> Hey Vlad,
> >>
> >> There are rendering problems on Win32 too. I traced it, and the bug  
> >> seems to
> >> be coming from the fbCompositeSrc_x888xnx8888mmx function.
> >>
> >> If you comment out this loop, it all works fine:
> >>
> >> 	while (w >= 16)
> >> 	{
> >> 	    __m64 vd0 = *(__m64 *)(dst + 0);
> >> 	    __m64 vd1 = *(__m64 *)(dst + 2);
> >>
> >> ......
> >>
> >> 	    *(__m64 *)(dst + 14) = vd7;
> >>
> >> 	    w -= 16;
> >> 	    dst += 16;
> >> 	    src += 16;
> >> 	}
> >>
> >> That's a temporary fix, I have no idea what the problem inside this  
> >> loop
> >> might be, maybe Fred can shed some light.
> >
> > That function is not ignoring source alpha as it should be.  Attaching
> > fix.  Going to do a quick review of other places that may have the  
> > same
> > bug.
> >
> >> I'm attaching my resulting images, with and without MMX, and opaque  
> >> and
> >> non-opaque. The non-opaque ones are fine because we're calling a much
> >> simpler code path, although the MMX version still gives a different  
> >> result
> >> from the non-MMX one.
> >>
> >> Best,
> >>
> >> Antoine
> >>
> >>> -----Original Message-----
> >>> From: cairo-bounces at cairographics.org
> >>> [mailto:cairo-bounces at cairographics.org] On Behalf Of
> >>> Vladimir Vukicevic
> >>> Sent: Tuesday, May 27, 2008 7:51 PM
> >>> To: cairo at cairographics.org
> >>> Subject: [cairo] xlib bug, with testcase
> >>>
> >>>
> >>> Howdy,
> >>>
> >>> This showed up as https://bugzilla.mozilla.org/show_bug.cgi? 
> >>> id=433917
> >>> -- it seems to happen on linux and win32, though I haven't 
> >>> tried reproducing it on win32.  The attached testcase shows
> >>> the problem; I've also attached the ref rendering from the
> >>> image backend.  If the first paint_with_alpha has an alpha
> >>> value less than 1.0, then..
> >>> strange things happen, I'm not even sure exactly what.  I'll
> >>> try to figure out a regression range in the next few days,
> >>> though if someone wants to beat me to it, please feel free :)
> >>>
> >>>     - Vlad
> >>>
> >>>
> >> _______________________________________________
> >> cairo mailing list
> >> cairo at cairographics.org
> >> http://lists.cairographics.org/mailman/listinfo/cairo
> > -- 
> > behdad
> > http://behdad.org/
> >
> > "Those who would give up Essential Liberty to purchase a little
> > Temporary Safety, deserve neither Liberty nor Safety."
> >        -- Benjamin Franklin, 1759
> > <pixman-fbCompositeSrc_x888xnx8888mmx-alpha.patch>
> 
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-- 
behdad
http://behdad.org/

"Those who would give up Essential Liberty to purchase a little
 Temporary Safety, deserve neither Liberty nor Safety."
        -- Benjamin Franklin, 1759