[Wayland-bugs] [Bug 99268] With Clickfinger behavior, pointer movement briefly turns into a scroll when a thumb is dropped onto the pad

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=99268

--- Comment #8 from Peter Hutterer <peter.hutterer at who-t.net> ---
the current algorithm works: if we have a finger that exceeds the motion
threshold for more than 5 events in a row, a new touch will be marked as thumb
and ignored. In your recording, the new touch happens at the fourth event, i.e.
another 2 events (~25ms later) and the thumb detection would've kicked in.

fixing this is nontrivial because we just don't have enough data and there are
many conflicting use-cases (responsive scrolling vs palm detection vs pinch
gestures vs thumb detection). Right now, I don't have a good idea on how to fix
this beyond "don't drop your thumb on a touchpad if the touchpad isn't capable
of detection thumbs". Which is the case here because all we have is pressure
and the thumb has the same pressure levels as your moving finger.

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