xcb: fix regression with missing XI_PropertyEvent

Wacom stylus proximity detection had stopped working: it was not
detecting which type of tool is in use, so all stylus types
acted as a generic drawing stylus.

Selecting XI_PropertyEvent on a root window fixes the problem.
There is nothing in the XI2 specification that says that this
property would not be supported on non-root windows. Possibly
it is bug in the X server. Anyways, selecting XI_PropertyEvent
on a root window in this case actually is better. Property event
contains a global state information, there is nothing window
specific in it, so there is no need to select it for every native
sub-window.

It is worth noting that XI_HierarchyChanged also seems to work
only when selected on the root window (according to my testing
results). And on XI2 author's blog post about XI_HierarchyChanged
it says [1]:

"These events are sent to all windows, so it doesn't really
matter where you register. The traditional approach is to
register on the root window."

This kind of further confirms that it might be bug in X Server's
implementation.

[1] http://who-t.blogspot.no/2009/06/xi2-recipies-part-2.html

Task-number: QTBUG-64911
Change-Id: I8582675bf835239932e23f4596966dc167495e30
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

0 files changed, 0 insertions, 0 deletions