[Wayland-bugs] [Bug 98839] Trackpad cursor movement feels sluggish at very slow speeds and does not move at all when you pivot your finger around a spot

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=98839

--- Comment #7 from Peter Hutterer <peter.hutterer at who-t.net> ---
(In reply to Nate Graham from comment #5)
> Touchpad size as listed by the kernel: 117x56mm
> User-specified touchpad size: 118x58mm

close enough, I'd say

> After recompiling libinput and installing it to /, is there an easier way or
> reloading the driver than restarting?

I'm going to assume you didn't install to / given that you notice an effect but
there are a few things to watch out for: use --prefix=/usr and on fedora also
add --libdir=/usr/lib64. libinput master has a lower soname than 1.5.3, so you
may be installing it correctly but things are still picking up the other one.
Make sure to remove libinput.so.10.10.4, as master will currently install
10.10.3
Once installed, you need to restart X only (or the compositor if you're under
wayland), no need to actually reboot.

For local testing, use the ./tools/event-gui app. It's not exactly the same and
affected by lag but good enough to get an idea before having to restart the
session.

(In reply to Nate Graham from comment #6)
> Turning off the hysteresis entirely definitely has an effect, but it doesn't
> resolve the issue.
> 
> It doesn't feel like an event rate issue either; with my touchpad, I can
> make medium-sized circles as fast as I can move my finger. As I reduce the
> size of the circles though, at about 1 cm diameter, the cursor stops moving
> in a circle and sort of wobbles awkwardly around its current location.

I think what you're seeing is an effect of the firmware skipping data, most
likely to avoid pointer wobbles. The problem is simply that the interaction you
want to have is very similar to someone holding the finger still but still
getting changing sensor readings. This effect is particularly bad on the Lenovo
T450 [1] In that case, there isn't much we can do though.

[1]
https://who-t.blogspot.com.au/2016/09/libinput-and-lenovo-t450-and-t460.html

You could try the RMI4 patchset to see if it makes a difference:
http://lkml.iu.edu/hypermail/linux/kernel/1612.2/00646.html

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