Nowadays, Clutter knows what an implicit grab is, which gives
us already the feel that we are after with buttons (e.g. press
and drag on the button will not enter other actors meanwhile).
ClutterGrab was only added to provide that feel meanwhile, and
it's also slightly more intense (e.g. altering keyboard focus,
or triggering leave events on all parents of the button) which
may trigger side effects.
An example is the IBus candidates popup, where the pagination
buttons may indirectly trigger dismissing of the entire popup
when interacted, by stealing the keyboard focus to the
client/actor doing IM.
Related: https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2497
Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/2244
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2924>
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