[Wayland-bugs] [Bug 105222] RFE: keyboard debouncing

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=105222

--- Comment #7 from Peter Hutterer <peter.hutterer at who-t.net> ---
Created attachment 137597
  --> https://bugs.freedesktop.org/attachment.cgi?id=137597&action=edit
keyboard state

I wrote a tool to visualise what your keyboard does, see here:
https://github.com/whot/input-data-analysis/blob/master/keyboard-state/keyboard-state.py

The generated output for your event recording is attached and it shows a number
of issues. First, there doesn't seem to be a consistent prediction of when the
keyboard bounces. Look at the * rows in the output, these mark events with less
than 3ms. Initially I ran this on 8ms and that's even more. I was hoping we'd
only get these when multiple keys are down but that doesn't seem to be the
case.

This makes debouncing a lot harder, because we'll inevitable end up having to
discard key events. The one you mentioned at 10.735 can only be debounced if
the initial space key press is discarded, the second press does not come in
until 32ms later. For reference, the button debounce timeouts are 12 and 25ms,
and some consider that too long.

Googling around for the issue indicates this is a common enough (hardware)
problem:
https://www.dell.com/community/General/Precision-5510-keyboard-douuble-characters/m-p/4758956
https://www.reddit.com/r/Dell/comments/5qydpb/keyboard_repeat_issues_wdell_xps_15_9560/
and it appears the hw may be the same as the XPS for which you can find even
more complaints. I really suggests taking this up with Dell to get a fix.

Honestly, this is something I'm very reluctant to fix in libinput. It'll cost a
lot of time and effort, is likely to break thinks for other users and appears
to be a hardware bug.

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