Invoking the task switcher (I use <Alt-Tab>) prompts a (very distracting) message box:

Window/Tasks Switcher error message

If I release <Alt-Tab>, but then activate it shortly after, it will continue to grow, as such:

Window/Tasks Switcher multiple error messages

I'm running Debian 9.2, e.g. Stretch, on a HP Probook 6450b. None of the base switcher effects works, and neither does the downloadable ones I've tried. The switching itself works, there's just no effect, or preview of any windows, it just switches instantaneously.


  1. What could be causing this?
  2. How can I solve it?

Edit: I found a bug report. Reported Nov. 2015, maintainer* answered Aug. 2016, and then, silence. Doesn't bode well.

* I assume

  • KDE5 plasma is still not rock solid stable, so there are a lot of bugs now. If this bug is new then please report it: bugs.debian.org/cgi-bin/… Nov 7, 2017 at 21:16
  • @IporSircer It's fairly solid on Arch Linux. This looks like a packaging issue. Switching works for me. But yeah, if you don't get anything useful here, you'd probably just want to contact Debian about this.
    – Sparhawk
    Nov 7, 2017 at 21:36
  • I found a bug report, but it really doesn't bode well, especially considering how minor a bug it is. Nov 7, 2017 at 23:11

3 Answers 3


The window switcher installation is broken, resources are missing

It seems you downloaded some theme or custom task switcher that is not compatible with your current version.

I had same problem and fixed it selecting a working theme, then restarting (or relogging), using following command :

kwin_x11 --replace

Hope it helps.

  • 1
    This did the trick for me. I'm pretty sure my issue was caused by a package update without restarting the session.
    – jamespfinn
    Jun 18, 2019 at 14:24
  • can you be more specific about "theme"? which theme did you pick? i seem to get this no matter which "desktop theme" i pick.
    – Jayen
    Aug 17, 2019 at 10:54
  • @Jayen using a default one instead of custom themes : imgur.com/a/xTddYoO same for task switcher Aug 26, 2019 at 5:53
  • 1
    thanks. it turned out just having a broken theme installed broke all the themes. after uninstalling it, all the other themes worked fine.
    – Jayen
    Aug 26, 2019 at 9:18

In systemsettings5, go to workspace->window management->task switcher. Here, under "Visualisation", try choosing something different from the drop-down (for example, I had the problem you describe when "Cover switch" was selected). Click Apply in the lower right corner. Then, bring up the run dialog (alt+f2 unless you changed the hotkey) and enter kwin_x11 --replace, followed by ENTER. "Breeze Dark" instead of "Cover switch" worked for me, fwiw.


It may happen because of broken switch layout/theme (like "compact" one). Try to delete all downloaded theme, choose one from default list and restart kwin (or reboot system).

  • 2
    Welcome to U&L! Your answer might be good start, but needs some more detail to be helpful: How should someone "delete themes" -- should they delete files from a specific directory? How can they tell which themes are "downloaded" or "default"?
    – JigglyNaga
    Nov 8, 2018 at 13:46

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