Pen tilt values come into Blender through ghost platforms and device
drivers with inconsistent and ambiguous directions. This PR codifies
that we consider tilt-x positive values to be rightward, negative
values as leftward. Similarly tilt-y positive is away from the user,
negative is toward the user. Comments are updated to make this clear.
This fixes Windows Ink (currently always returning left and away). This
also reverses the Wayland tily-y values to match. We might still have
to consider a user preference to swap directions if we find differences
within a platform.
Pull Request: https://projects.blender.org/blender/blender/pulls/137501
e1e250aa84