Merge request for new button scrolling mode

[Paul Ausbeck]

I've put together a merge request for a new button scrolling mode that I've
developed. Having just recently and finally abandoned Windows on my personal desktop
machines, one thing I couldn't do without is a replacement for the Chiral Mouse
scrolling mode that I developed while working for Synaptics around 15 years ago. The
Chiral Mouse is still under patent but I've put together a simpler mode
that I find works similarly enough that feel I can wait another five years for
Chiral Mouse to come off patent.

I've spent a significant amount of time putting together a merge request for the
new scrolling mode. I am hopeful that the libinput maintainers will take a look
at the mode for their own personal use. The mode is cordoned off under a udev
flag in the hope that the patch can just be merged with little change to allow those
that are interested to easily experiment. I've also limited the code changes to a
single source file, evdev.c, to allow for easier review. Hopefully, there will be enough interest to justify effort to integrate more fully with X and wayland.

The commit:

https://gitlab.freedesktop.org/ausbeck/libinput/-/commit/989d1b8e49cb90d8251cbde3942c6d36124a1278

The merge request:

https://gitlab.freedesktop.org/ausbeck/libinput/-/merge_requests/1

I've spent quite some time on this trying to make it something that easily
digestible . But I haven't done anything like this before, so there may be some, maybe
even large, holes that I've missed in the process. If so, I would be grateful if
you would point me in the right direction. I am OK with spending yet more time on
this if I feel like it's getting any traction at all.

Regards,

Paul Ausbeck