Callback used by sticky_events_foreach.
When this function returns
true, the next event will be returned. When
false is returned,
sticky_events_foreach will return.
event is set to
null, the item will be removed from the list of sticky events.
event can be
replaced by assigning a new reference to it. This function is responsible for unreffing the old event when removing or modifying.
a sticky Event.
the pointer to optional user data.