# Register an event that finishes before the begin of current one.
	#
	# `delay` indicates the time between the end of the new event and the begin of the current one.
	# Use 0.0 if both event should be contiguous and not overlap.
	#
	# Returns the new event information that can be used in fluent programming.
	fun add_before(event: E, delay: Float, duration: nullable Float): EventInfo[E]
	do
		duration = duration or else 0.0
		return queue.add_at(event, start - delay - duration, duration)
	end