[Wayland-bugs] [Bug 95290] synaptics touchpad jitter

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=95290

--- Comment #8 from liam at fightingcrane.com ---
Created attachment 123862
  --> https://bugs.freedesktop.org/attachment.cgi?id=123862&action=edit
screencast of evemu-play with "another evemu scrolling jitter recording"

(In reply to Peter Hutterer from comment #7)
> ok, I still don't know what exactly I'm supposed to be looking at here.
> Let's make sure we don't clash in terminology terms: jitter means that the
> pointer keeps moving even when the finger(s) is/are held still. jumps mean
> that the pointer suddenly moves by a large amount.
> 
> I didn't see any jitter in the recording of the still finger, usually we'll
> see some pointer movement when a touchpad is jittery.
> 
> In this recording I can see scroll events and I can see some small ca 1
> pixel up down movement after the button click event, but it's hard to tell
> what the movement is supposed to be given the other movements in the event.
> Also remember, I can only see the touchpad events, not your finger so it's
> sometimes hard to tell what is intended and what isn't.
> 
> So, I'm sorry but I'll need you to explain in detail what the bug is you're
> seeing and when. And ideally produce an evemu-recording that isolates this
> behaviour and has no or hardly any other events in it.

I said this in the initial report:

The trackpad passes along movement even when my fingers aren't moving.
Depending on context,this manifests as either a jittery pointer (randomly hops
about a, roughly, five square pixel area) or, when I've two fingers on the
trackpad, it will randomly scroll by about the same amount as the pointer
jitters.

The issue with (two-finger) scrolling is analogous to the pointer jitter: when
holding two fingers still on the trackpad, the page will move up and down a bit
(again, it looks to be ABOUT -+5 pixels...on both the x and y axis if those
freedoms are available).
Now, I'd call that amount of movement jitter rather than jumps.
If that doesn't explain the problem sufficiently, can you please tell me how
you'd like it phrased? I spent quite a while reading about this before posting
the bug so that: 1. it hadn't yet been reported (similar bugs have been
reported, but not for this model trackpad), 2. you had all the information you
needed (from
https://wayland.freedesktop.org/libinput/doc/latest/reporting_bugs.html).
I'm attaching a screencast which plays back the recording called "another evemu
scrolling jitter recording". I use two finger scroll twice. It's after the
second scroll ends that you see a pretty substantial jitter (around the 6s mark
and lasts for around 2s).
I hope this helps.

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