libinput pointer precision at different sensitivity levels

[Josh Simmons]

Hello there,

I've found what seems to be some interesting behaviour in the events
returned from xinput2 while using the libinput driver with the "FLAT"
profile.

It seems that changing the sensitivity (via the gnome control panel)
only changes the scale of the events sent by libinput, and not the
frequency (in device coordinates) in which they are reported to the
application. (Either that or they're somehow losing device coordinate
sub-pixel precision at some point along the way).

The result of this is that with the standard 100% sensitivity the
driver will report to X only events that are multiples of 1 pixel.
With a sensitivity of 200% it will only report events that are
multiples of 2 pixels. With a sensitivity of 50% it will report with a
0.5 pixel resolution and so on making the default and higher
sensitivities feel very janky and not at all smooth.

My work around is just to slide the sensitivity as low as I can and
use my mouse's DPI adjustment to get to where I want to be, but it
seems like a bug that all the sub-pixel resolution is missing from the
default configuration at the very least.

Thanks, and apologies if I've missed this issue when searching the archive.
Josh.