https://bugs.kde.org/show_bug.cgi?id=524788
Bug ID: 524788
Summary: Duplicated/excessive scroll events on Wayland with
high-resolution wheel mice (Razer Basilisk V2)
Classification: Plasma
Product: kwin
Version First 6.7.4
Reported In:
Platform: Arch Linux
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: input
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Target Milestone: ---
Created attachment 195492
--> https://bugs.kde.org/attachment.cgi?id=195492&action=edit
libinput record output for Razer Basilisk V2
SUMMARY
When using a mouse with high-resolution scrolling (such as the Razer Basilisk
V2) on KWin Wayland, scrolling the wheel results in duplicated or excessively
accelerated scroll events.
A single notch of the scroll wheel causes extreme jumps in applications
(browsers, text editors), whereas the same mouse works completely normally on
GNOME/Mutter.
STEPS TO REPRODUCE
1. Connect a Razer Basilisk V2 (or similar mouse sending both REL_WHEEL and
REL_WHEEL_HI_RES).
2. Start a KDE Plasma Wayland session.
3. Scroll one notch on any scrollable window.
OBSERVED RESULT
Scroll events are doubled / excessively accelerated.
EXPECTED RESULT
Smooth, single-step scrolling per notch.
ADDITIONAL INFORMATION
I initially suspected a kernel or libinput issue and reported it to upstream
libinput:
[https://gitlab.freedesktop.org/libinput/libinput/-/work_items/1329]
According to libinput maintainers:
- The kernel sends both REL_WHEEL and REL_WHEEL_HI_RES for backwards
compatibility.
- libinput channels them into separate events (`LIBINPUT_EVENT_POINTER_AXIS`
and `LIBINPUT_EVENT_POINTER_SCROLL_WHEEL`).
- A Wayland compositor should handle either one, but never process both
simultaneously as separate scroll events.
- It appears KWin Wayland is accumulating/processing both events, causing
duplicate scroll steps.
System details:
- OS: Arch Linux
- Graphics Platform: Wayland
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