[GM45,Intrepid] Screen corruption when enabling/disabling external monitor with compiz

This is a picture of the corrupted display. Notice how the top part of each monitor has a black strip across it. The corruption can manifest itself in other ways as well. Sometimes the entire picture on the external monitor is garbled.

Update: I tried to do some debugging by attaching gdb to the /usr/bin/Xorg but I didn't get anything useful with the backtrace. Since X doesn't actually crash, I would need to find a reasonable breakpoint, but I was unable to do so. Does anyone have any ideas?

More interestingly, I can enable the external monitor using the command:
xrandr --output VGA --auto --right-of LVDS
with no problems. This suggests the bug occurs because of the difference in the way xrandr is called from the command line and how it is called in gnome-display-properties. Any ideas?

This sort of sounds like another GM45 lockup error that was recently fixed:
https://bugs.freedesktop.org/show_bug.cgi?id=17292

Please test with latest updates to Jaunty and see if the bug still exists.

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.

Sorry about the long silence. My laptop is my production machine and I didn't want to install a development version of Ubuntu on it. I realized this week that I should be able to get it working with the Live CD. So I just tested with Jaunty Flight 5. The bug still exists in this version with the same symptoms as before. Suggestions?

As a side note, I had a few other problems that didn't exist in Intrepid. I'm not sure if they were because I was working with a Live CD, or they are regressions from Ubuntu. When I used the xrandr utility it seemed like it only wanted to support a screen size of 2048x2048. I also experienced a hard lockup when the Screen Resolutions Utility wanted to changed the screen size from 1440x1440 (with only my laptop screen) to 2880xsomething for dualhead. I'll file bugs if I can replicate this issues.

Well, next I'd like to forward this issue upstream, but first it must be retested on latest development version of Karmic to make sure the issue still happens there with the latest code. ISO images are available at http://cdimages.ubuntu.com/releases/karmic/. If you can reproduce it in the LiveCD environment, you shouldn't need to modify your installed system. Also please attach a fresh Xorg.0.log and dmesg from this testing.

This issue appears to be resolved in Karmic Alpha 2.

There is another bug that needs to be resolved. Desktop doesn't extend across both of my 1440x900 monitors. So half of one monitor is unusable. I'm guessing the desktop size is limited to 2048. I'll file a bug when / if I have time.

Paul

Thanks for letting us know the issue is resolved. Yes, there is a 2048 limit, however it was recently increased for this chip, so going forward you may have better results in karmic.