[cairo] xlib bug, with testcase

[Vladimir Vukicevic]

Hmm, I don't see this fix in the pixman repo -- did it get pushed up?

    - 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
>>>
>>>
>> _______________________________________________
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>> 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>