[PATCH v3 libinput 0/6] Add touch-size based touch and palm handling for Apple touchpads

[Peter Hutterer]

For reference, v1 was
https://lists.freedesktop.org/archives/wayland-devel/2017-March/033593.html
v1 was more complicated than this set:
* it tried to use physical measurements for touch sizes
* it tried to use those measurements combined with the resolution to
  estimate touch size even when rotated
The physical measurements were effectively hardcoded and relied on the
touchpad to give use meaningful values - which they didn't.

This version is simpler: we have thresholds and if major/minor
go above these thresholds (or below) the touch is considered logically
down (or up). Same as the pressure handling. Palm handling has a second,
higher thresholds. If either major/minor go above, it's a palm.

This is only enabled for apple touchpads so far and while the thresholds
work on my magic trackpad here, expect them to need some adjusting for the
laptops. The apple restriction isn't hardcoded, adding a size range to the
udev hwdb will enable it for the respective devices.

A new tool is provided to measure these thresholds easily.

Cheers,
  Peter