[Wayland-bugs] [Bug 98839] Somehow conditionalize hysteresis (hardware black/whitelist, device property introspection, user-exposed setting, etc)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=98839

--- Comment #36 from Peter Hutterer <peter.hutterer at who-t.net> ---
we tried to remove the hysteresis a while ago and got so many complaints about
the fingers still wobbling that we had to re-instate it. It was largely
whack-a-mole with the various touchpads. Search for
LIBINPUT_MODEL_WOBBLY_TOUCHPAD in the log, f6c2d4b and 27078b2 mark the range
that is interesting.
Things *may* be better now with SMBus/RMI4 being more common, but I don't know.

The reason we have it is that a large portion of all touchpads wobble when you
hold the finger still on the touchpad. That wobbling is hard to/impossible to
determine from real finger movement, the hysteresis is the only solution here.

tp_init_hysteresis() is the function here, the margins are set to res/2, so
0.5mm each direction (i.e. the whole hysteresis area is 1mm wide). The way it's
implemented means that the hysteresis doesn't take effect after the first 0.5mm
of movement though because continuously moving in one direction will keep
moving the edge. See the comment at evdev_hysteresis().

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