-
Some tablets such as those in the XP-PEN PRO series use "dials" which are actually scrollwheels and emit EV_REL events. These should not be emulated as rings (which are absolute) so we must expose them as a new tablet event. Adds LIBINPUT_EVENT_TABLET_PAD_DIAL that work largely identical as our high-resolution wheel events (i.e. the values are in multiples or fractions of of 120). Currently supports two dials. This is a lot of copy/paste from the ring axes because the interface is virtually identical. The main difference is that dials give us a v120 value in the same manner as our scroll axes. Notes: - REL_DIAL is mutually exclusive with REL_WHEEL, we assume the kernel doesn't (at this point) give us devices with both. If this changes for devices with three dials (wheel + hwheel + dial) we need to add code for that. - REL_DIAL does not have a high-resolution axis and we assume that any device with REL_WHEEL_HI_RES will also have REL_HWHEEL_HI_RES (if the second wheel exists). - With dials being REL_DIAL or REL_WHEEL there is no possibility of detecting a finger release (the kernel does not route EV_RELs with a value of zero). Unless this is implemented via a side-channel - and it doesn't look like any hardware that supports dials does that - we cannot forward any information here. So unlike absolute rings we cannot provide a source information here. Closes #600 Co-authored-by:
Peter Hutterer <peter.hutterer@who-t.net> Part-of: <!967>
