To allow for more natural pointer movements from relative pointer
devices (e.g. mouse, touchpad, tablet tool in relative mode, etc), scale
the relative motion from libinput with the scale of the monitor. In
effect, this means that the pointer movement is twice as fast (physical
movement vs numbers of pixels passed) as before, but it also means that
the same physical movement crosses the distance in a GUI no matter if
it is on a HiDPI monitor or not.
https://bugzilla.gnome.org/show_bug.cgi?id=778119
e60dfd5b23