Notes on in range

This wiki page is intended to be a place to record notes about the internal workings of the Wacom Kernel driver.

In range while exiting

Hopefully this clarifies "in range while exiting"... I'll be using the classic definition of "in range" (i.e., "in range" is further from the tablet than "in prox") and assuming the use of one of the classic non-HID tablets (Intuos5, Intuos Pro, Cintiq 24, Cintiq 27)

Imagine that you have a pen on the tablet surface (i.e., BTN_TOUCH = 1 and ABS_PRESSURE > 0) and that you pick it up and completely remove it from proximity. Normally the driver would first receive a few reports with decreasing pressure, then a few reports with increasing distance, a couple "in range" reports, and finally the "out-of-prox" report. Nothing special.

Now, however, imagine that you have a pen on the tablet surface and that you pick it up very quickly but not entirely out of proximity. If you're unlucky, the tablet can send a report indicating contact and then immediately afterwards send a report indicating "in range". Because in-range packets are handled by "wacom_intuos_inout" rather than "wacom_intuos_general", the function needs to explicitly send userspace data consistent with the "in-range" state (i.e., BTN_TOUCH = 0, ABS_PRESSURE = 0, ABS_DISTANCE = maximum). If this doesn't happen, userspace is left thinking that the pen is still touching the tablet until you either completely remove it from proximity (causing the "exit report" code to reset everything to zero) or bring it closer to the tablet so that it starts sending in-prox reports that are handled by "wacom_intuos_general".