[SOLVED] "Not able to select appropriate backend" for mouse under kde

ATnpG · 2025-07-01 14:05:22

Ever since yesterday, I am getting these errors in journalctl -xe, and I am unable to turn off the giant mouse under kde (wayland) because I get "Not able to select appropriate backend" in the mouse settings

kwin_wayland[1394]: kf.windowsystem: static bool KX11Extras::mapViewport() may only be used on X11
systemsettings[11985]: kcm_mouse: Not able to select appropriate backend.
systemsettings[11985]: kcm_mouse: Not able to select appropriate backend.
systemsettings[11985]: qrc:/kcm/kcm_mouse/main.qml:40: TypeError: Cannot read property 'isAnonymousInputDevice' of null
systemsettings[11985]: qrc:/kcm/kcm_mouse/main.qml:68: TypeError: Cannot read property 'inputDevices' of null
systemsettings[11985]: qrc:/kcm/kcm_mouse/main.qml:65: TypeError: Cannot read property 'isAnonymousInputDevice' of null
systemsettings[11985]: qrc:/kcm/kcm_mouse/main.qml:89: TypeError: Cannot read property 'isAnonymousInputDevice' of null
systemsettings[11985]: qrc:/kcm/kcm_mouse/main.qml:249: TypeError: Cannot read property 'isAnonymousInputDevice' of null
systemsettings[11985]: qrc:/kcm/kcm_mouse/main.qml:29: TypeError: Cannot read property 'inputDevices' of null
systemsettings[11985]: kcm_touchpad: Using X11 backend
systemsettings[11985]: qrc:/kcm/kcm_touchpad/main.qml:501:13: Unable to assign [undefined] to bool
systemsettings[11985]: qrc:/kcm/kcm_touchpad/main.qml:502:13: Unable to assign [undefined] to bool
systemsettings[11985]: kcm_mouse: Not able to select appropriate backend.
systemsettings[11985]: kcm_mouse: Not able to select appropriate backend.
systemsettings[11985]: qrc:/kcm/kcm_mouse/main.qml:40: TypeError: Cannot read property 'isAnonymousInputDevice' of null
systemsettings[11985]: qrc:/kcm/kcm_mouse/main.qml:68: TypeError: Cannot read property 'inputDevices' of null
systemsettings[11985]: qrc:/kcm/kcm_mouse/main.qml:65: TypeError: Cannot read property 'isAnonymousInputDevice' of null
systemsettings[11985]: qrc:/kcm/kcm_mouse/main.qml:89: TypeError: Cannot read property 'isAnonymousInputDevice' of null
systemsettings[11985]: qrc:/kcm/kcm_mouse/main.qml:249: TypeError: Cannot read property 'isAnonymousInputDevice' of null
systemsettings[11985]: qrc:/kcm/kcm_mouse/main.qml:29: TypeError: Cannot read property 'inputDevices' of null
kwin_wayland[1394]: kwin_xwl: Could not create a source from 0x56392fe200d0 0
kwin_wayland[1394]: kwin_xwl: Could not create a source from 0x5639310a2d20 0

The most recent relevant topic is from a year ago: https://bbs.archlinux.org/viewtopic.php?id=295613
This was supposed to be fixed, so I don't know what I'm supposed to do here... libinput is already installed.

Last edited by ATnpG (2025-07-01 15:02:31)

seth · 2025-07-01 14:24:23

https://archlinux.org/news/plasma-640-w … re-on-x11/ ?

ATnpG · 2025-07-01 14:39:32

I'm not using X11, but wayland. plasma-x11-session is not installed and I can login just fine.

seth · 2025-07-01 14:57:31

I meant because of https://bugs.kde.org/show_bug.cgi?id=482048#c23 which kinda makes it sound as if this was a wayland/lack of X11 related problem.
Leaving aside the "error", what was fixed was systemsettings crashing because of this.
Do you have any functional problems or just the noise in the journal?

ATnpG · 2025-07-01 15:01:57

I solved it! The issue was that the mouse was not configurable, so I could not turn off the giant mouse shake effect.

I had to add the following to /etc/environment:

QT_QPA_PLATFORM=wayland;xcb

I had to relogin after, but then it was fixed.

Last edited by ATnpG (2025-07-01 15:03:17)

seth · 2025-07-01 15:04:16

Meaning you likely exported "QT_QPA_PLATFORM=xcb" somewhere else before?
And yes: you were then running all KDE stuff on xwayland

Arch Linux

#1 2025-07-01 14:05:22

[SOLVED] "Not able to select appropriate backend" for mouse under kde

#2 2025-07-01 14:24:23

Re: [SOLVED] "Not able to select appropriate backend" for mouse under kde

#3 2025-07-01 14:39:32

Re: [SOLVED] "Not able to select appropriate backend" for mouse under kde

#4 2025-07-01 14:57:31

Re: [SOLVED] "Not able to select appropriate backend" for mouse under kde

#5 2025-07-01 15:01:57

Re: [SOLVED] "Not able to select appropriate backend" for mouse under kde

#6 2025-07-01 15:04:16

Re: [SOLVED] "Not able to select appropriate backend" for mouse under kde

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