[Wayland-bugs] [Bug 91369] Libinput 0.19 and 0.20 ignore POINTINGSTICK_CONST_ACCEL

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=91369

--- Comment #63 from Peter Hutterer <peter.hutterer at who-t.net> ---
And another commit on top of that branch, check that you have "filter: apply
the same factor to x and y" before testing please. Mostly happy with this but
I'm not 100% sure about the range yet, the slow one (-1.0) is still relatively
fast. Not sure how much this matters.

How to test this:
First, run this from a fresh checkout, a bunch of tools have renamed so without
a fresh checkout, you may be testing stale code. Preferably build with meson,
it's easier to clean up after that.

Measure the trackpoint range with the libinput-measure-trackpoint-range tool.
Note that this measures the hardware range as-is, don't press too hard, don't
press too soft. The tool is supposed to capture the highest reasonable deltas
that the device sends. If you press harder than you would use in normal usage,
it'll skew the results. If you don't press hard enough, it'll skew the results.
Look at the histogram printed, pick a good number. Usually that's the edge of
the bell curve or maybe a bit further out. Leaving this tool running in the
background while using the trackpoint for a bit is a good idea to capture the
full range.

Set the LIBINPUT_ATTR_TRACKPOINT_RANGE property. Note that this is not a
configuration option, it's a description of the hardware. Thus, if you change
the sysfs sensitivity, you need to measure again. There's a bit of room for
error on the range property, especially if you get different ranges from the
trackpoint on multiple measuring runs. Adjust as necessary to be as accurate as
possible. Better to use a slightly smaller range than a larger range, I think.

Make sure the udev property shows up on the device before testing.

When testing, please do test with different speed settings. The default speed
setting won't make everyone happy, that's why we have the slider. Test from -1
to +1 and see. In theory, no-one should need -1 or +1, the majority should be
close to the 0 mark. Test for a bit to let your muscle memory adjust.

Also, set your sysfs drift_time to 30 or above, it'll spare you some accidental
movements, see bug 93448.

If you have a trackpoint that does *NOT* have a sysfs sensitivity/drift_time
file you're using a different kernel driver. I don't know what impact that has
on this code, but make sure you mention it in any comments.

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