Red Hat Bugzilla – Bug 473768
F10: Window switching in compiz causes flickering
Last modified: 2009-12-04 12:57:05 EST
Description of problem:
Window switching in compiz (using alt-tab or the scale effect) causes a lot of flickering if there are too many windows open (usually five or more).
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. Open five windows (Epiphany, Evolution, Rhythmbox, Gossip and Gnome-Terminal always reproduce the bug here);
2. Alt-tab to switch between them.
If Gnome-Terminal is open, the flickering seems to get worse. Maybe because of transparency?
Video: Intel i915
One more bit of information: It seems that you need at least three maximized windows to hit the bug.
Aside from adding a "me too" (intel i915 video as well), I wanted to note some additional behaviours:
* When switching with alt-tab, sometimes all windows show noise/static during the switch.
* After switching, sometimes all windows except the active window keep the noise/static.
* The behaviour seems to only occur with alt-tab switching; clicking on a different window does not cause the effect.
* Even when the flickering or noise/static do not occur, the redraw on switching windows with alt-tab is very noticeable, esp. compared to just clicking on a different window to refocus.
I've turned compiz off for the time being, but am very happy to do further testing on the problem or test packages with fixes.
I'm seeing this on an Acer Aspire One (945GME). Textures seem to be swapped randomly causing the flickering. This only appeared once I worked around an unrelated bug preventing the X server setting up a write-combining MTRR. It may be worth testing disabling this MTRR with:
echo "disable=7" > /proc/mtrr
Replace 7 with the index of the write-combining range that shows up in "cat /proc/mtrr". It's not a workaround because of the reduced performance, but if we can establish that write-combining is the trigger, it might help pinpoint the cause. I've tested with write-back caching and get no corruption.
While you can't see the flickering in a screenshot, I've got a couple which show the resulting texture corruption with the ring switcher. I've also seen flickering with the scale plugin, glide animation and even just scrolling large web pages in Firefox.
Created attachment 328121 [details]
Screenshot of texture corruption with the ring switcher.
This screenshot shows the texture for part of one window being applied to another when using the ring switcher.
Created attachment 328122 [details]
Screenshot of texture corruption with the ring switcher.
This screenshot shows the background texture replaced with textures from two windows when using the ring switcher.
Created attachment 328144 [details]
Video of flickering on Intel graphic card
I have the same. Everything is visible on a video. Having an Opera window open increases this effect. My hardware (lspci output):
00:02.0 VGA compatible controller: Intel Corporation 82G33/G31 Express Integrated Graphics Controller (rev 10)
Since this bugzilla report was filed, there have been several major updates in various components of the Xorg system, including Intel driver, which may have resolved this issue.
To be more precise, Intel has undergone a major rewrite during Fedora 10, 11 and 12 cycles, and whole driver is working a lot better now. Users who have experienced this problem are encouraged to retry with at least Fedora 12 Beta and see if the issue is still relevant.
Please, if you experience this problem on Fedora 12 Beta or up-to-date system running Rawhide, let us now in the comment for this bug, or whether the upgraded system works for you.
If you won't be able to reply in one month, I will have to close this bug as INSUFFICIENT_DATA. Thank you.
We hope to see how many older bugs in Intel driver are still relevant today, in hope that most of them were fixed in rewrite process.
[This is a bulk message for all open Fedora 10 i810-related bugs (39 of them are still open). I'm adding myself to the CC list for each bug, so I'll see any comments you make after this and do my best to make sure every issue gets proper attention.]
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We are sorry, but the Fedora Project is will soon stop longer releasing bug fixes or any other updates for this version of Fedora. There were so many changes between Fedora 10 and Fedora 12 in Intel driver and X.Org that it's very likely that this bug is fixed. This bug will be set to CLOSED:WONTFIX to reflect this, but please reopen it if the problem persists after upgrading to the latest version of Fedora (version 12), which is available from: