[Wayland-bugs] [Bug 103947] can't seem to get a usable acceleration profile on T450s trackpoint

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=103947

            Bug ID: 103947
           Summary: can't seem to get a usable acceleration profile on
                    T450s trackpoint
           Product: Wayland
           Version: unspecified
          Hardware: Other
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: libinput
          Assignee: wayland-bugs at lists.freedesktop.org
          Reporter: njs at pobox.com

I'm using Debian testing on a Thinkpad T450s, and a recent upgrade made some
change to trackpoint handling. Since then I've been unable to find a
configuration that makes my trackpoint usable, and I'd really appreciate some
help.

With Gnome's default configuration, the pointer's top speed is comfortable and
makes it easy to flick the pointer across the screen in the way I expect, but
it's very difficult to control at low speeds -- small movements are jerky and I
often jump the pointer back and forth several times across a button before
managing to land on it and press it. If I verrrry carrrrefully apply the
minimum force possible to the pointer stick, it starts to move at a reasonable
speed, but as I increase that it feels like it quickly "jumps" to some higher
speed. It feels like the acceleration steps are in the wrong place. (I'm not
sure how to check if that's true or not though -- I could be hallucinating. Is
there some way to debug this, e.g. by asking libinput --debug-events to say
when acceleration is kicking in or not?)

On the other hand, if I turn down the mouse speed slider in the Gnome settings
app, then fine control becomes reasonable but the top speed is frustratingly
slow. Hauling the pointer from one corner of the screen to another feels like a
chore.

I've read
https://wayland.freedesktop.org/libinput/doc/latest/pointer-acceleration.html,
and I've tried fiddling empirically with the /sensitivity and /speed entries in
/sys/devices/platform/i8042/serio1/serio2, but I still haven't figured out any
way to make this work. I feel like I want a way to shift the initial ramp up
period over to the right, while keeping the maximum speed in about the same
place? Does that make sense? But I can't figure out how to do that. I can't
even figure out what the difference is between "sensitivity" and "speed"...

Any help would be much appreciated.

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