We provide a mechanism by which a 'platform' (eg: Gtk) can register some
hook functions to be called to collect platform-data at the point of
sending an outgoing action activation request and also to inform the
platform of this data on incoming requests (before and after dispatching
the actual request).

This can be used for forwarding timestamp and startup-notification
information (as is presently done in GApplication) but the before/after
hook could also be used for acquiring/releasing the Gdk lock or other
similar things.

https://bugzilla.gnome.org/show_bug.cgi?id=665737