Normally users switch xkb input sources and ibus input sources.
But currently the first input source only is running. It's also good
to preload all ibus engines in the logging session so that users switch
input sources quickly without the launching time of input sources.
The following is the ibus change:
https://github.com/ibus/ibus/commit/cff35929a9https://bugzilla.gnome.org/show_bug.cgi?id=695428
Instead of calling out to gnome-settings-daemon we'll just implement
the switching logic ourselves and use mutter APIs that allow this
functionality to work both in X sessions and when we're a Wayland
compositor.
Switching IBus engines is done transparently as well just like g-s-d
used to do.
https://bugzilla.gnome.org/show_bug.cgi?id=736435
gnome-settings-daemon doesn't this for us anymore. Note that
ibus-daemon isn't DBus activatable but just spawning it is fine
because it does its own single instance management. The library
notifies us when it shows up and goes away through the connected and
disconnected signals.
https://bugzilla.gnome.org/show_bug.cgi?id=736435
