[Wayland-bugs] [Bug 105535] SynPS/2 Synaptics TouchPad detects fingers not touching the touchpad while using two-finger scrolling

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=105535

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Depends on|                            |105258
             Status|NEEDINFO                    |ASSIGNED

--- Comment #8 from Peter Hutterer <peter.hutterer at who-t.net> ---
oops, the range mismatch is fixed in master now (4ff5f02d9c). But the big thing
here is:

> As for single-finger pointer motion - it's normal. Bug does not not appear there.

Basically this means that the touchpad pressure changes when two fingers are
down. That's not good... Anyway, I bisected this and came up with: commit
3979b9e16a5ed141506d95f80ddfd7b94651dcfa. Basically the problem is that we now
assume that when we have more fingers down than the touchpad can individually
detect (>1 for semi-mt devices) then we assume all fingers have an
above-threshold pressure value.

This matches the data in the evemu recording, the pressure is well below the
thresholds yet we treat it as down. Should be fixable.


Referenced Bugs:

https://bugs.freedesktop.org/show_bug.cgi?id=105258
[Bug 105258] libinput crashes Xorg with SIGABRT in tp_tap_handle_state()
[evdev-mt-touchpad-tap.c:1030|1028]
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