[i945GM] stray horizontal black lines in multiple apps (firefox, emacs, ...)

[Nathaniel Smith]

Binary package hint: xserver-xorg-video-intel

I just upgraded from Intrepid to Jaunty. One consequence of the upgrade was that I'm now seeing some sort of cross-application rendering bug -- horizontal black lines show up in various apps.

To reproduce:
1) Open firefox to a long-ish page.
2) Hold down the "down-arrow" key to scroll downwards.
3) Occasional scattered black lines will appear overlaying the page content.

The lines survive incremental scrolling, but any kind of forced redraw (another window moving in front of them, scrolling the location where they appear off-screen and then back again, etc.) gets rid of them.

Observed in firefox (as mentioned above), GNU emacs, and then they showed up in the Gnome screenshot dialog when I was taking a screenshot for this bug report too... screenshots attached.

This is on a Thinkpad X60 with Intel 945GM integrated graphics, using EXA for acceleration. I do not use desktop effects of any sort (plain ol' metacity). My font hinting is set to use sub-pixel smoothing, "RGB" order (not VRGB).

I don't know for sure that it's an X server bug, but assigning to xserver-xorg-video-intel because the corruption seems to occur during within-server scrolling blits, at least sometimes.

[lspci]
00:00.0 Host bridge [0600]: Intel Corporation Mobile 945GM/PM/GMS, 943/940GML and 945GT Express Memory Controller Hub [8086:27a0] (rev 03)
 Subsystem: Lenovo Device [17aa:2017]
00:02.0 VGA compatible controller [0300]: Intel Corporation Mobile 945GM/GMS, 943/940GML Express Integrated Graphics Controller [8086:27a2] (rev 03)
 Subsystem: Lenovo Device [17aa:201a]

[Nathaniel Smith (njs)]

This appears to be a side-effect of #377172 -- after fixing my xorg.conf to remove the overlarge Virtual size I no longer see the rendering bugs.

[Bryce Harrington (bryce)]

Hi njs,

Thanks for including an image to demonstrate the issue. Could you also please attach the output of `lspci -vvnn`, and attach your /var/log/Xorg.0.log or Xorg.0.log.old file from after reproducing this issue. If you've made any customizations to your /etc/X11/xorg.conf please attach that as well.

[This is an automated message. Apologies if it has reached you inappropriately; please just reply to this message indicating so.]

[Nathaniel Smith (njs)]

As mentioned a few comments up, this appears to be a side-effect of using a Virtual setting that is >2048x2048. But here's the log so you can see all the excitement.

[Geir Ove Myhr (gomyhr)]

Would you mind testing the newer drivers at https://launchpad.net/~ubuntu-x-swat/+archive/x-updates/ ? And with the new driver, test if it is also present if you add these two lines to the "Device" section of your xorg.conf:
  AccelMethod "uxa"
  Option "ModeDebug" "true"
(the second line will only enable some debugging output in your logs, which may be useful later).

[Bryce Harrington (bryce)]

[This is an automatic notification.]

A new major version of the -intel driver is now available in Karmic.

This version includes a major reworking of the acceleration
architecture, which resolves a huge number of issues. We do not know
whether it resolves the issue you reported.

Would you mind testing Karmic Alpha-2 and seeing if it is still a
problem? CD ISO images are available here:

  http://cdimages.ubuntu.com/releases/karmic/

If the issue can still be reproduced on karmic, please report here with
your findings, and attach a fresh Xorg.0.log from your test, and we will
be able to forward the bug upstream.

Otherwise, if the bug no longer exists in Karmic, let us know that as
well.

In the off chance you encounter different bugs while attempting to test
Karmic, please report those as new bug reports.

[Bryce Harrington (bryce)]

We're closing this bug since it is has been some time with no response from the original reporter. However, if the issue still exists please feel free to reopen with the requested information. Also, if you could, please test against the latest development version of Ubuntu, since this confirms the bug is one we may be able to pass upstream for help.

It seems likely to me this bug is gone; the -intel driver has improved immensely in Karmic and a lot of bugs are being reported as no longer present. So hopefully that's the case here too.