[Wayland-bugs] [Bug 106044] Unreliable tap-to-click on a DELL XPS 9370

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=106044

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

           What    |Removed                     |Added
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                 CC|                            |peter.hutterer at who-t.net

--- Comment #1 from Peter Hutterer <peter.hutterer at who-t.net> ---
The log parts that matter here, for the evemu record from comment 0:

event19 - tap: touch 0 state TAP_STATE_IDLE → TAP_EVENT_TOUCH → TAP_STATE_TOUCH
event19 - tap: touch 1 state TAP_STATE_TOUCH → TAP_EVENT_TOUCH →
TAP_STATE_TOUCH_2
event19 - palm: touch 1: palm-tap detected
event19 - tap: touch 1 state TAP_STATE_TOUCH_2 → TAP_EVENT_MOTION →
TAP_STATE_TOUCH_2_HOLD
event19 - tap: touch 1 state TAP_STATE_TOUCH_2_HOLD → TAP_EVENT_RELEASE →
TAP_STATE_HOLD
event19 - tap: touch 0 state TAP_STATE_HOLD → TAP_EVENT_RELEASE →
TAP_STATE_IDLE

So basically what this means:
- touch down
- second touch down
- second touch is detected as palm touch because it's at the far edge of the
touchpad
- this puts the first touch into the "touch-and-hold" state

IOW, if a palm is detected during tapping, we don't continue with the tap
because there's too much chance of interference. That's the reason that you
don't get a one-finger tap with two fingers (one of which is a palm). And the
reason you don't get a two-finger tap is because one touchpoint is in the palm
detection area on the far side of the touchpad. This is an intentional
behaviour, see:
http://wayland.freedesktop.org/libinput/doc/latest/palm_detection.html

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