KDE Plasma Compositor Not Activating

Luna Murasaki

Luna Murasaki

Purple Demon
Bit poster
I set up two Linux VMs. Both are installed from the latest openSUSE Tumbleweed arm64 ISO, and are configured identically except that for one, I selected the GNOME desktop during install, and for the other, I selected KDE Plasma. The host is an M3 Max MacBook Pro 16" running Sonoma 14.4.1.

The GNOME one seems to work just fine. The KDE one works fine except that the compositor isn't working. There is no error message - it just doesn't seem that the compositor is on because all the special effects aren't working, there's weird squaring of the rounded window corners, and hotkeys to activate desktop effects, or to enable/disable the compositor do nothing. 3D games are still working fine - I tested by installing SuperTuxKart and it seems to run okay. Desktop composition functionality is also working great in the GNOME VM - this is only a problem in the KDE one.

I remember installing KDE a long time ago and I had the desktop compositor working.

Any ideas? Even if you guys don't have the actual solution, just providing me with some tips for diagnosis (log files for the compositor, ways to try and activate it from the terminal, other things to try, etc.), it would be greatly appreciated.
 
So I was finally able to fix the problem on my own. To anyone who comes across this page from a search engine who has my same problem, it seems desktop composition only works in Wayland, which is not the default. The SDDM login manager in the KDE VM was defaulting to using "Plasma (X11)". By changing it to "Plasma (Wayland)", desktop composition started working. I then had a new problem where my mouse pointer became invisible, making it almost impossible to click on anything, but I was able to fix this by creating the file "/etc/environment", putting "KWIN_FORCE_SW_CURSOR=1" in this new file, and then rebooting the VM.
 
It seems you're encountering an issue with the KDE Plasma compositor not activating in your virtual machine.
Open the KDE System Settings and navigate to Display and Monitor. Go to the Compositor section and ensure that it is enabled on startup.
You can try to manually enable the compositor using the terminal.

qdbus org.kde.KWin /Compositor resume

To suspend compositing

qdbus org.kde.KWin /Compositor suspend

DE logs can be accessed using the journalctl command. To filter for KDE-related logs, you can us

journalctl -f | grep --line-buffered kde

Additionally, check the ~/.xsession-errors file for any relevant output that might indicate what's going wrong with the compositor.
If you're running KDE Plasma 6.0 or later, it defaults to a Wayland session, which requires GPU acceleration for the compositor to function. Ensure that your VM is set to start a Wayland session if it's not already. You can usually select this from the SDDM login manager Kynect.
If you experience issues like an invisible mouse pointer, you can create a file named /etc/environment and add the following line to it

KWIN_FORCE_SW_CURSOR=1

Then, reboot the VM to apply the changes.
As a last resort, you might consider reinstalling KDE components that are related to the compositor, such as plasma-desktop, sddm, qt5-base, gtk2, and gtk3.
Remember to back up any important data before making significant changes to your system.
 
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