When the "Automatic" mapping is chosen for a display-attached tablet device,
Mutter is in charge of applying the heuristics to map the tablet device to
its most likely attached display.
When that happens, the Wacom panel does not know better (or anything)
to show the calibration UI than picking a GdkMonitor and hoping for the
best.
To improve this situation, Mutter has been added a D-Bus interface so it
is possible to query it for the output that a tablet device is mapped to.
This commit adds the support for this interface, so that the Wacom panel
does know to pick the right GdkMonitor to fullscreen the calibration UI on.
Use GsdDeviceManager to monitor libwacom-supported tablets coming and
going. Hide the Wacom panel from the list when there's no supported
tablets plugged in.
This makes loading faster, with less I/O, avoids unnecessary
code duplication (around 1k lines shaved), and ensures that
all the panels link and work appropriately.
By the same token, it will stop external panels from being
created, and loaded.
https://bugzilla.gnome.org/show_bug.cgi?id=690036
