[Wayland-bugs] [Bug 105696] Apple Magic Trackpad scrolling prevented by speed-based thumb detection (libinput 1.10)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=105696

Peter Hutterer <peter.hutterer at who-t.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Apple Magic Trackpad        |Apple Magic Trackpad
                   |scrolling sensitivity too   |scrolling prevented by
                   |low (libinput 1.10)         |speed-based thumb detection
                   |                            |(libinput 1.10)
             Status|NEEDINFO                    |ASSIGNED
                 CC|                            |benjamin.tissoires at gmail.co
                   |                            |m

--- Comment #7 from Peter Hutterer <peter.hutterer at who-t.net> ---
First I think there's something wrong with your kernel

E: 0.253846 0001 0145 0002      # EV_KEY / BTN_TOOL_FINGER      2

I haven't seen that before, a repeat event for BTN_TOOL_FINGER? Benjamin, any
ideas? Also, the slot association is strange, usually the slot numbers match
the fingers down and get re-used, this recording seems to use them in seemingly
arbitrary order. That's generally fine, just unusual.

Back to libinput: the issue is definitely the touch size threshold, there are
only few events below 60, followed immediately by events above the threshold.

The problem appears to be:
 event25 - touch 7 is speed-based thumb
 event25 - touch 2 is speed-based thumb
 event25 - touch 4 is speed-based thumb
 event25 - touch 10 is speed-based thumb

This appears before every POINTER_MOTION sequence when two fingers are down. In
short, the problem here is that the second finger is detected as thumb after
the first finger moved. Not 100% sure yet why this happens, e.g. 3.712742
starts touch 7 after a single event of touch 9. We require 4 events for
speed-based thumb detection though, so this simply shouldn't happen. I'll try
to dig into this.

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