[Wayland-bugs] [Bug 94910] The cursor "jump" sometimes

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=94910

--- Comment #17 from Dudley Du <dudlx at hotmail.com> ---
Hi Jeremy,

Thanks for your try and response.
It seems that the noise immunity improvement has no help on this issue, so this
issue should not be caused by the noise.

After analysized the captured report data in jump.evemu file, I got following
inforamtion:
1) it seems that the first finger doing tapping on the trackpad device. Because
in most case, the finger touch data located in a very small area.
2) when the first finger appearred on the trackpad device, the second finger
may appear later and disappeared before the first figner left;
   Such as the fingers data of TRACKING_ID of 92, 93.
3) When the first figner appeared on the trackpad device, the second finger may
appear later and disappeared after the first finger left;
   Such as the fingers data of TRACKING_ID of 68, 72,94, 96,99, 101.
4) When the first finger appeared on the trackpad device, the second finger may
appear immediaterly after the first finger left.
   At this situation, the first finger left event won't be seen, because it was
immediately replaced by the second finger when it left, so the second finger
would be recognized as the first finger.
   Such as the finger data of TRACKING_ID of 104.
5) Beside the first appeared finger, the second finger would appeare within a
almoust fixed area. This fixed area exists in the area as the rectangle from
<61, 833> to <169, 877>.
6) The second finger would appeare and disappear, would not exist all the time.
When there was an finger on the trackpad, the ghost finger then may appear.

Based on the above apalysis, I think there may be a ghost finger issue onthe
the trackpd device. The second appeared finger was just the ghost finger.
So when the symptom of item 4) happpend, it's sure that the cursor jump will be
seen on the screen.

To doulbe confirm on these symptoms, could you help double check that if it was
possible that there was a ghost finger reported even there was no finger touch
on the trackpad device?
Or could you try to press the trackpad with a non-conductor object on the
trackpad device, which may help to reproduce the ghost finger issue.
Because the ghost may appear and disapper by itself, so it seems that the ghost
finger was on the edge to be triggered or not on the trackpad device.

If the ghost finger happened on the trackpad device, it may indicate the
hardware has been broken. For example, in the manufacture, there is a foreign
matter or air was brought in between the malar and the PCB. Or some other
factors, that has affect the sensors on the fixed area.
So could you also try anohter trackpad on anthoer HP Falco Chromebook?

Thanks,
Dudley

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