If the user maps eg. Alt+F2 to a pad button, the MetaInputSettings will
send the full Alt press, F2 press, F2 release, Alt release sequence.
However the keycode corresponding to Alt is found in level 1, so the
Shift modifier gets unintendedly latched in addition to the Alt key
press/release pair.
We could probably improve keycode lookup heuristics so level=0 (and
no modifier latching) is preferred, but we can do without it altogether
for modifier keys.
Unfortunately XKeysymToKeycode() falls short in that it coalesces keysyms
into keycodes pertaining to the first level (i.e. lowercase). Add a
ClutterKeymapX11 method (much alike its GdkKeymap counterpart) to look up
all matches for the given keysym.
Two other helper methods have been added so the virtual device can fetch
the current keyboard group, and latch modifiers for key emission. Combining
all this, the virtual device is now able to handle keycodes in further
levels.
Closes: https://gitlab.gnome.org/GNOME/gnome-shell/issues/135
Virtual input devices aim to enable injecting input events as if they
came from hardware events. This is useful for things such as remote
controlling, for example via a remote desktop session.
The API so far only consists of stumps.
https://bugzilla.gnome.org/show_bug.cgi?id=765009
