public delegate bool CollectPadsEventFunction (CollectPads pads, CollectData pad, Event event)
A function that will be called while processing an event.
It takes ownership of the event and is responsible for chaining up (to event_default) or dropping events (such typical cases being handled by the default handler).
the CollectPads that triggered the callback
the Pad that received an event
the Event received
user data passed to set_event_function