[cairo] Render EXTEND_REPEAT bug is back...

[Owen Taylor]

On Sun, 2008-01-27 at 11:00 -0800, Vladimir Vukicevic wrote:
> On Jan 26, 2008, at 11:03 AM, Owen Taylor wrote:
> 
> >
> > On Fri, 2008-01-25 at 13:12 -0800, Vladimir Vukicevic wrote:
> >> It looks like that the ati/radeon driver is hit by the old
> >> 'buggy_repeat' bug, even with a new X server.  I've got Xorg  
> >> 1.4.0.90,
> >> radeon driver 6.7.197 and a more recent one built from git yesterday;
> >> both show the bug.  (Tested with https://bugzilla.mozilla.org/show_bug.cgi?id=41358.)

That can't be the right bug number.

> > Are you sure it's really *the* old buggy repeat bug and not another  
> > bug
> > that the same work-around code works around?
> 
> I'm not -- the symptoms look identical, but I don't know if the  
> underlying cause is the same.  The mozilla bug report got updated; it  
> doesn't seem to be limited to the radeon driver, people using sis and  
> i810 at least are seeing it.  Do we have a testcase for this?  I can't  
> remember if it's in the testsuite since it's platform-specific, but it  
> would be good to be able to reproduce it without firefox.  If we  
> don't, I can put one together tomorrow.

The original bug report on the X server:

 https://bugs.freedesktop.org/show_bug.cgi?id=3566

The patch attachment is no longer available (all
bugzilla.freedesktop.org attachments got scrambled some years ago), but
as you can see from the description, that bug had to do with a very
specific logic error in the core RENDER framebuffer code. I haven't
looked at the current version of that file, but it seems improbable to
me that that particular logic error was reintroduced.

So, I think the first step here is to track down and figure out what the
current X server bug you are seeing is, and what exactly is the scope of
it. Before that, trying to figure out how to work around it seems like a
risky and uncertain proposition.

- Owen

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