When creating a virtual device for the native backend, no "device-added"
is emitted.
Similarly, no "device-removed" signal is emitted either when the virtual
device is disposed.
However, the backend plugs into the "device-added" signal to set the
monitor device. Without the "device-added" signal being emitted, the
monitor associated with a virtual device remains NULL.
That later will cause a crash in `meta_idle_monitor_reset_idlettime()`
called from `handle_idletime_for_event()` when processing events from a
virtual device because the device monitor is NULL.
Make sure to emit the "device-added" signal when creating a virtual
device, and the "device-removed" when the virtual device is disposed.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/1037
The end goal is to have all clutter backend code in src/backends. Input
is the larger chunk of it, which is now part of our specific
MutterClutterBackendNative, this extends to device manager, input devices,
tools and keymap.
This was supposed to be nice and incremental, but there's no sane way
to cut this through. As a result of the refactor, a number of private
Clutter functions are now exported for external backends to be possible.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/672
