[wayland] KWin crashes when I Alt+Tab

I’ve recently been working to move my desktop PC from X11 to Wayland. It was going quite smoothly until I hit this particular issue. I’ve had the skills to debug and fix everything that’s come up prior, but when we reach GDB, I’m out of my depth.

With a 100% rate of occurrence, when I Alt+Tab, KWin crashes, dumps its core, and restarts. When it restarts, most of my applications are no longer running. Sometimes Konsole will still be running, strangely, but certainly everything else I’ve tried is lost upon this crash.

I am not allowed to upload the GDB file that the debugging documentation specifically intructed me to record, though, so I’ll need direction there.

I can’t upload text files either, so I can’t share share information about my system through qdbus!

Community? Does this belong here? What’s the standard for uploading files?

That sounds serious and you should probably create a bug report at bugs.kde.org

But you can also send the info here by copy pasting (unless it is insane amounts) you can press this button: (press the cogwheel to get the drop down)

And then paste the log. (in text)

:face_with_symbols_over_mouth: Thank you!

The guide suggests that if you don’t know it to be a bug, to start with the forums. Bit confusing, all of it.

Thank you for the direction. I’ll head off to the bug tracker and link back here for posterity.

I mean, yes, that is correct, but I assumed you knew it to be a KDE related crash and not something else on the system.

Post the log like I showed earlier and people could take a look! :heart:

If it crashes it is a bug :D. Regular people probably can’t read backtraces so its probably better to report crashes to the bug tracker.

Are you using polonium by any chance?

@Cannon_Palms I now have this exact same issue, along with all the icons in my launcher bar bunching up over the “start” button… did you end up creating a bug for it or finding a solution to it?

At least as far as the alt-tab problem, if I uncheck(disable) Task Switcher Visualizations I no longer have the problem with Kwin crashing, but I still have this for my launcher


This stuff all used to work a few system updates ago (I don’t restart with each update), so not sure how it broke exactly.

Seems all visual effects crash kwin, i.e. dragging a window to the top of the screen to maximise also crashes kwin :confused:

The problem is this setting in ~/.config/kdeglobals:


I have no idea how that how it was set, but once I remove it, save and force a crash, I can once again alt+tab and snap windows with visualisation animations without crashing kwin.

EDIT: looks to be the same as this - caused by a crash and automatic fallback, how annoying… :angry:

As mentioned the fallback is automatic - outside your control.

I noticed because I have a login startup job that checks the X11 compositor, which can also fallback to software. The job raises a notification. I’m not sure checking the compositor will always catch SceneGraphBackend=software, but I’ve now added a check for that too. Here’s the script I’m currently using:

#set -x
# Wait for desktop to settle down
sleep 30

compositor_enabled=$(qdbus-qt5 org.kde.KWin /Compositor org.kde.kwin.Compositing.active)

if [ "$compositor_enabled" != "true" ]
     notify-send -a "Check Compositor" -t 0 -i dialog-error.png 'Hardware -> Display and Monitor -> Compositor is disabled!'

if grep -q 'SceneGraphBackend=software' ~/.config/kdeglobals
     notify-send -a "Check kdeglobals"  -t 0 -i dialog-error.png 'Warning ~/.config/kdeglobals SceneGraphBackend=software'

Thanks, I’ve opened a bug 486078 – Automatically enabling software rendering causes KWin to crash on all visual effects (alt+tab, maximise, snap window)

I don’t think Plasma should do what it’s doing silently and then just leave users to figure it out on their own…

I’ll use your script in the meantime, though with a change to #!/usr/bin/env bash for the magic line to get it to run on NixOS.

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