(In reply to comment #84)
> Yes, that is characteristic of this bug. The internal vertex/texture
> coordinates that are being passed along the GPU pipeline become corrupt (it
> looks like we overflow a small ring buffer). The only effective approach

If it would be plain 'overflow' - than I'd be seeing this kind of corruption
always right after X starts.

But it seems like i.e. Firefox must be used for certain period of time,
to make these corruptions visible.

Surely I'm not not an expert on GPU programming - but maybe when the
physical memory gets fragmented enough after some usage there are some
'cached bo' objects - maybe their usage is not fully synchronized?

Also the effect could also disappear (I've not yet noticed any particular way 
for that) - so then Firefox scroll even the very same pages and there
is no problem (i.e. now I run still the same session - and I do not get any 
visible problem)

> I've found so far has been to keep the number of rectangles inside the GPU
> pipeline below a magic value - but that is quite tricky here, and the

Well why the number would sometimes work for ours without a single
visible problem, and suddenly start to show them again?

My impression here is, when this problem is visible,
it looks like operations is working with 'wrong' parameters
(i.e. sometimes I see the image stretched, inverted, zoomed)

Maybe parameters have only some bits mangled - not fully synchronized memory
from CPU for GPU??

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You received this bug notification because you are a member of Desktop
Packages, which is subscribed to xserver-xorg-video-intel in Ubuntu.
https://bugs.launchpad.net/bugs/1098334

Title:
  [gen4 sna] Font corruption in Chromium tab bar

Status in X.org xf86-video-intel:
  In Progress
Status in “xserver-xorg-video-intel” package in Ubuntu:
  Triaged

Bug description:
  After enabling the SNA acceleration method and rebooting, I noticed
  that graphical glitches appeared in the letters on Chromium's tab bar
  during the mouse hover animation. I've attached a screenshot
  illustrating this, particularly with the letter "g" in the screenshot.

  ProblemType: Bug
  DistroRelease: Ubuntu 13.04
  Package: xorg 1:7.7+1ubuntu4
  ProcVersionSignature: Ubuntu 3.7.0-7.15-generic 3.7.0
  Uname: Linux 3.7.0-7-generic x86_64
  ApportVersion: 2.8-0ubuntu1
  Architecture: amd64
  Date: Thu Jan 10 16:00:55 2013
  InstallationDate: Installed on 2012-09-24 (107 days ago)
  InstallationMedia: Kubuntu 12.04.1 LTS "Precise Pangolin" - Release amd64 
(20120822.2)
  MarkForUpload: True
  SourcePackage: xorg
  UpgradeStatus: Upgraded to raring on 2012-09-25 (107 days ago)

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