# Listens to the progression of a possibly long-running operation.
interface ProgressionListener
	# The number that represents a completed operation.
	fun progression_max: Int do return 100

	# The operation started.
	fun started do end

	# The operation progressed.
	#
	# Parameter:
	#
	# * `progression`: Indicator of the progession, between `0` and
	# `progression_max`.
	fun progressed(progression: Int) do end

	# The operation is done.
	fun done do end
end