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Wayland: fix scroll axis units - #22207
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MrJul merged 1 commit intoSep 10, 2026
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Only wheels send axis_value120, so continuous sources fell through to the raw axis value, whose logical-pixel distance was read as a detent count. Convert it at 10px per detent instead, the convention GTK3, Qt, SDL and Chromium all assume, which also matches Avalonia's own X11 backend. Touchpad scrolling on Wayland becomes 10x slower as a result.
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MrJul
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MrJul
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Only wheels send axis_value120, so continuous sources fell through to the raw axis value, whose logical-pixel distance was read as a detent count. Convert it at 10px per detent instead, the convention GTK3, Qt, SDL and Chromium all assume, which also matches Avalonia's own X11 backend. Touchpad scrolling on Wayland becomes 10x slower as a result.
MrJul
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backport-candidate-12.1.x
grokys
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Oct 7, 2026
Only wheels send axis_value120, so continuous sources fell through to the raw axis value, whose logical-pixel distance was read as a detent count. Convert it at 10px per detent instead, the convention GTK3, Qt, SDL and Chromium all assume, which also matches Avalonia's own X11 backend. Touchpad scrolling on Wayland becomes 10x slower as a result.
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What does the pull request do?
Correctly scales continuous (touchpad, trackpoint) scroll deltas on Wayland backend.
What is the current behavior?
WaylandInputDispatchertreats raw pixel deltas as full mouse wheel notches, causing the scroll to be uncontrollably fast.What is the updated/expected behavior with this PR?
Touchpad scrolling on Wayland has a normal speed, similar to X11.
How was the solution implemented (if it's not obvious)?
Only wheel sources send
axis_value120, so every continuous source falls through to the raw axis value.WaylandInputDispatchernow divides the raw axis value by 10 pixels per detent, matching other Wayland clients:gdkdevice-wayland.c:1924wl_fixed_to_double (value) / 10.0gtkeventcontrollerscroll.c:68#define SURFACE_UNIT_DISCRETE_MAPPING 10qwaylandinputdevice.cpp:1114delta * -12against a 120-per-detent scaleSDL_waylandevents.c:78#define WAYLAND_WHEEL_AXIS_UNIT 10wayland_pointer.cc:192constexpr double kAxisValueScale = 10.0Checklist
Breaking changes
none
Obsoletions / Deprecations
none
Fixed issues
Fixes #22034