Bug 509516

Summary:	Hi-res scroll events aren't passed through to nested kwin-wayland
Product:	[Plasma] kwin	Reporter:	André M <andre.vmatos>
Component:	platform-wayland-nested	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	CONFIRMED ---
Severity:	minor	CC:	kde, nate
Priority:	NOR
Version First Reported In:	6.4.5
Target Milestone:	---
Platform:	NixOS
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description André M 2025-09-15 12:19:43 UTC

SUMMARY
I'm running NixOS unstable plasma 6.4.5 on host, and another NixOS unstable systemd-nspawn container, to which I bind wayland socket, export WAYLAND_DISPLAY in the container, and startplasma-wayland a full nested plasma session; desktop shows up in a nested window, which I make fullscreen and disable global shortcuts in host (so it receives all inputs when focused); I can still go back to host by switching desktops with 3-finger gesture; it works surprisingly well, except for some smaller issues:

In this case, when looking at kwin's console Input Events, I can see both Delta=15, Delta(V120)=120 events when scrolling; but if check in the nested kwin, I see Delta=15, Delta(V120)=0
Most apps work fine with just the low-res events, but some (e.g. Zed Editor) look only at the V120, and scroll doesn't work.

STEPS TO REPRODUCE
1. Launch nested kwin session
2. Open kwin debug console
3. Check Delta(V120)=0 for scroll events

OBSERVED RESULT
Delta(V120) (hi-res scrolling events) are passed as 0

EXPECTED RESULT
Events are passed as is

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 6.4.5
KDE Plasma Version: 6.4.5
KDE Frameworks Version: 6.17.0
Qt Version: 6.9.2

ADDITIONAL INFORMATION
I'm using a Logitech MX Anywhere 3S mouse over bluetooth, which is supposed to have hi-res scroll, but I never managed to make it detect high resolution support (as per libinput debug-events)