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Bug 748594 - x11-drivers/nvidia-drivers-450.xx: breaking dev-qt/qt*-5.15.1, weird phenomena in KDE Plasma etc.
Summary: x11-drivers/nvidia-drivers-450.xx: breaking dev-qt/qt*-5.15.1, weird phenomen...
Alias: None
Product: Gentoo Linux
Classification: Unclassified
Component: Current packages (show other bugs)
Hardware: All Linux
: Normal normal (vote)
Assignee: Jeroen Roovers (RETIRED)
Depends on:
Reported: 2020-10-14 03:07 UTC by Michael Moon
Modified: 2020-10-16 15:35 UTC (History)
0 users

See Also:
Package list:
Runtime testing required: ---

emerge --info (emerge-info.txt,9.42 KB, text/plain)
2020-10-14 03:07 UTC, Michael Moon

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Description Michael Moon 2020-10-14 03:07:51 UTC
Created attachment 665197 [details]
emerge --info

Hi, just updated Qt to 5.15.1 and now my KDE desktop is flipping out - kwin complains that "Compositing is not possible", I get big black rectangles where the menus should be in systemsettings, my panels are gone, and my desktop background isn't being drawn at all (so windows leave trails when I move them).

glxinfo | grep direct says Yes, glxgears and vkcube work fine, my web browsers seem to have 3d rendering, mpv quite happily uses gpu rendering, and Steam (and several games) are fine too - it's only Qt things that seem to be affected.

I added the following to my package.mask as they were recently updated:


and will report back when it's done downgrading.

I'm using nvidia-drivers-450.57-r1 and I haven't updated it since August, while this issue appeared today after updating Qt yesterday.

It's a little tricky to search for relevant bugs with these symptoms, does anyone have a link to something upstream I can check?
Comment 1 Michael Moon 2020-10-14 06:55:41 UTC
After downgrading the listed packages back to their various qt-5.14.2 versions, everything has returned to normal on my desktop - compositing is working fine, and KDE panels and desktop backgrounds and things are being drawn correctly.
Comment 2 Andreas Sturmlechner gentoo-dev 2020-10-14 08:39:03 UTC
(In reply to Michael Moon from comment #0)
> I'm using nvidia-drivers-450.57-r1 and I haven't updated it since August

Please use a version that is actually in Gentoo repository, and try with latest 455.23.04-r1 in ~arch as well. This is a clear Nvidia bug suspect.
Comment 3 Andreas Sturmlechner gentoo-dev 2020-10-15 16:57:25 UTC
Nothing to do from KDE proj side. Re trouble with Nvidia 450.xx see bug 747472.
Comment 4 Michael Moon 2020-10-15 18:30:19 UTC
With nvidia-drivers-455.28 and QT-5.15.1 the problem appears to be resolved, so I guess it's confirmed as an nvidia-drivers problem.

WRT the linked bugs (thanks for the links btw), this is a desktop with only nVidia graphics, not a system with dual graphics.
Comment 5 Michael Moon 2020-10-15 18:31:39 UTC
Should Gentoo's QT packages add a blocker between QT-5.15 and nvidia-drivers-450 to reduce the chance of others having to search this bug?
Comment 6 Michael Moon 2020-10-16 04:37:31 UTC
After a reboot my plasmashell is crashing on an infinite loop in Qt5Quick, but I guess that's a separate issue which I'll make a separate bug report about
Comment 7 Andreas Sturmlechner gentoo-dev 2020-10-16 14:36:41 UTC
(In reply to Michael Moon from comment #5)
> Should Gentoo's QT packages add a blocker between QT-5.15 and
> nvidia-drivers-450
No, this strategy would produce an insane amount of blockers.