deferred class
	EV_DOCKABLE_TARGET

General
	cluster: interface
	description: 
		"Objects that allow dockable sources to be inserted as part of the
		dockable mechanism. Use `enable_docking' to permit sources to be dropped,
		and `veto_dock_function' to restrict which sources will be accepted. If a source
		is rejected by the veto function, then the parent structure will be explored until
		there are no more parents, or the source being transported is accepted.
		
		`docked_actions' is fired after the source of transport has been parented in `Current'."

Ancestors
	EV_ANY*
	EV_DOCKABLE_TARGET_ACTION_SEQUENCES*
	IDENTIFIED

Action sequences
	docked_actions: EV_DOCKABLE_SOURCE_ACTION_SEQUENCE

Queries
	data: ANY
	id_freed: BOOLEAN
	id_object (an_id: INTEGER_32): IDENTIFIED
	is_destroyed: BOOLEAN
	is_docking_enabled: BOOLEAN
	object_id: INTEGER_32
	veto_dock_function: FUNCTION [ANY, TUPLE [EV_DOCKABLE_SOURCE], BOOLEAN]

Commands
	copy (other: [like Current] EV_DOCKABLE_TARGET)
	destroy
	disable_docking
	enable_docking
	free_id
	set_data (some_data: [like data] ANY)
	set_veto_dock_function (a_function: FUNCTION [ANY, TUPLE [EV_DOCKABLE_SOURCE], BOOLEAN])