indexing
	description: "[
		Node for use with EV_TREE.
	]"
	legal: "See notice at end of class."
	status: "See notice at end of class."
	keywords: "tree, item, leaf, node, branch"
	date: "$Date$"
	revision: "$Revision$"

deferred class interface
	EV_TREE_NODE


feature -- Access

	accept_cursor: EV_POINTER_STYLE
			-- `Result' is cursor displayed when the screen pointer is over a
			-- target that accepts pebble during pick and drop.
			-- (from EV_PICK_AND_DROPABLE)
		require -- from  EV_ABSTRACT_PICK_AND_DROPABLE
			True
		ensure -- from EV_ABSTRACT_PICK_AND_DROPABLE
			result_not_void: Result /= Void
		ensure then -- from EV_PICK_AND_DROPABLE
			bridge_ok: Result = implementation.accept_cursor

	configurable_target_menu_handler: PROCEDURE [ANY, TUPLE [menu: EV_MENU; target_list: ARRAYED_LIST [EV_PND_TARGET_DATA]; source: EV_PICK_AND_DROPABLE; source_pebble: ANY]]
			-- Agent used for customizing the Pick and Drop Target Menu of `Current'.
			-- (from EV_PICK_AND_DROPABLE)

	cursor: EV_DYNAMIC_LIST_CURSOR [EV_TREE_NODE]
			-- Current cursor position.
			-- (from EV_DYNAMIC_LIST)
		require -- from  CURSOR_STRUCTURE
			True
		ensure -- from CURSOR_STRUCTURE
			cursor_not_void: Result /= Void
		ensure then -- from EV_DYNAMIC_LIST
			bridge_ok: Result.is_equal (implementation.cursor)

	data: ANY
			-- Arbitrary user data may be stored here.
			-- (from EV_ANY)

	default_identifier_name: STRING_8
			-- Default identifier_name if no specific name is set.
		ensure -- from EV_IDENTIFIABLE
			result_not_void: Result /= Void
			result_not_empty: not Result.is_empty
			no_period_in_result: not Result.has ('.')

	deny_cursor: EV_POINTER_STYLE
			-- `Result' is cursor displayed when the screen pointer is over a
			-- target that does not accept pebble during pick and drop.
			-- (from EV_PICK_AND_DROPABLE)
		require -- from  EV_ABSTRACT_PICK_AND_DROPABLE
			True
		ensure -- from EV_ABSTRACT_PICK_AND_DROPABLE
			result_not_void: Result /= Void
		ensure then -- from EV_PICK_AND_DROPABLE
			bridge_ok: Result = implementation.deny_cursor

	first: like item
			-- Item at first position
			-- (from CHAIN)
		require -- from CHAIN
			not_empty: not is_empty

	full_identifier_path: STRING_8
			-- Full name of object by prepending path of parent
			-- Uses '.' as a separator.
			-- (from EV_IDENTIFIABLE)
		ensure -- from EV_IDENTIFIABLE
			result_not_void: Result /= Void
			result_correct: parent = Void implies Result.is_equal (identifier_name)
			result_correct: parent /= Void implies Result.is_equal (parent.full_identifier_path + "." + identifier_name)

	generating_type: STRING_8
			-- Name of current object's generating type
			-- (type of which it is a direct instance)
			-- (from ANY)
		ensure -- from ANY
			generating_type_not_void: Result /= Void
			generating_type_not_empty: not Result.is_empty

	generator: STRING_8
			-- Name of current object's generating class
			-- (base class of the type of which it is a direct instance)
			-- (from ANY)
		ensure -- from ANY
			generator_not_void: Result /= Void
			generator_not_empty: not Result.is_empty

	has (v: like item): BOOLEAN
			-- Does chain include `v'?
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from CHAIN)
		require -- from  CONTAINER
			True
		ensure -- from CONTAINER
			not_found_in_empty: Result implies not is_empty

	has_recursively (an_item: EV_TREE_NODE): BOOLEAN
			-- Is `an_item' contained in `Current' at any level?
			-- (from EV_TREE_NODE_LIST)
		require -- from EV_TREE_NODE_LIST
			item_not_void: an_item /= Void
		ensure -- from EV_TREE_NODE_LIST
			not_found_in_empty: Result implies not is_empty
			index_not_changed: old index = index

	i_th alias "[]" (i: INTEGER_32): like item
			-- Item at `i'-th position.
			-- (from EV_DYNAMIC_LIST)
		require -- from TABLE
			valid_key: valid_index (i)
		ensure then -- from EV_DYNAMIC_LIST
			bridge_ok: Result.is_equal (implementation.i_th (i))

	frozen id_object (an_id: INTEGER_32): ?IDENTIFIED
			-- Object associated with `an_id' (void if no such object)
			-- (from IDENTIFIED)
		ensure -- from IDENTIFIED
			consistent: Result = Void or else Result.object_id = an_id

	identifier_name: STRING_8
			-- Name of object
			-- If no specific name is set, default_identifier_name is used.
			-- (from EV_IDENTIFIABLE)
		ensure -- from EV_IDENTIFIABLE
			result_not_void: Result /= Void
			result_not_empty: not Result.is_empty
			no_period_in_result: not Result.has ('.')
			default_name_available: not has_identifier_name_set implies Result.is_equal (default_identifier_name)

	index: INTEGER_32
			-- Current position.
			-- (from EV_DYNAMIC_LIST)
		require -- from  LINEAR
			True
		ensure then -- from EV_DYNAMIC_LIST
			bridge_ok: Result = implementation.index

	index_of (v: like item; i: INTEGER_32): INTEGER_32
			-- Index of `i'th occurrence of `v'.
			-- (from EV_DYNAMIC_LIST)
		require -- from LINEAR
			positive_occurrences: i > 0
		ensure -- from LINEAR
			non_negative_result: Result >= 0
		ensure then -- from EV_DYNAMIC_LIST
			bridge_ok: Result = implementation.index_of (v, i)

	item: EV_TREE_NODE
			-- Item at current position.
			-- (from EV_DYNAMIC_LIST)
		require -- from TRAVERSABLE
			not_off: not off
		require -- from ACTIVE
			readable: readable
		ensure then -- from EV_DYNAMIC_LIST
			not_void: Result /= Void
			bridge_ok: Result.is_equal (implementation.item)

	item_for_iteration: EV_TREE_NODE
			-- Item at current position
			-- (from LINEAR)
		require -- from LINEAR
			not_off: not off

	last: like item
			-- Item at last position
			-- (from CHAIN)
		require -- from CHAIN
			not_empty: not is_empty

	frozen object_id: INTEGER_32
			-- Unique for current object in any given session
			-- (from IDENTIFIED)
		ensure -- from IDENTIFIED
			valid_id: Result > 0 implies id_object (Result) = Current

	sequential_occurrences (v: like item): INTEGER_32
			-- Number of times `v' appears.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from LINEAR)
		require -- from  BAG
			True
		ensure -- from BAG
			non_negative_occurrences: Result >= 0

	parent: EV_TREE_NODE_LIST
			-- Parent of `Current'.
		require -- from EV_IDENTIFIABLE
			not_destroyed: not is_destroyed
		ensure -- from EV_IDENTIFIABLE
			correct: has_parent implies Result /= Void
			correct: not has_parent implies Result = Void
		ensure then -- from EV_ITEM
			bridge_ok: Result = implementation.parent

	parent_tree: EV_TREE
			-- Contains `Current'.
		require
			not_destroyed: not is_destroyed
		ensure
			bridge_ok: Result = implementation.parent_tree

	pebble: ANY
			-- Data to be transported by pick and drop mechanism.
			-- (from EV_PICK_AND_DROPABLE)
		require -- from  EV_ABSTRACT_PICK_AND_DROPABLE
			True
		ensure then -- from EV_PICK_AND_DROPABLE
			bridge_ok: Result = implementation.pebble

	pebble_function: FUNCTION [ANY, TUPLE, ANY]
			-- Returns data to be transported by pick and drop mechanism.
			-- (from EV_PICK_AND_DROPABLE)
		require -- from  EV_ABSTRACT_PICK_AND_DROPABLE
			True
		ensure then -- from EV_PICK_AND_DROPABLE
			bridge_ok: Result = implementation.pebble_function

	pebble_positioning_enabled: BOOLEAN
			-- If `True' then pick and drop start coordinates are
			-- pebble_x_position, pebble_y_position.
			-- If `False' then pick and drop start coordinates are
			-- the pointer coordinates.
			-- (from EV_PICK_AND_DROPABLE)
		require -- from EV_PICK_AND_DROPABLE
			not_destroyed: not is_destroyed
		ensure then -- from EV_PICK_AND_DROPABLE
			bridge_ok: Result = implementation.pebble_positioning_enabled

	pebble_x_position: INTEGER_32
			-- Initial x position for pick and drop relative to `Current'.
			-- (from EV_PICK_AND_DROPABLE)
		require -- from EV_PICK_AND_DROPABLE
			not_destroyed: not is_destroyed
		ensure then -- from EV_PICK_AND_DROPABLE
			bridge_ok: Result = implementation.pebble_x_position

	pebble_y_position: INTEGER_32
			-- Initial y position for pick and drop relative to `Current'.
			-- (from EV_PICK_AND_DROPABLE)
		require -- from EV_PICK_AND_DROPABLE
			not_destroyed: not is_destroyed
		ensure then -- from EV_PICK_AND_DROPABLE
			bridge_ok: Result = implementation.pebble_y_position

	pixmap: EV_PIXMAP
			-- Copy of image displayed on `Current'.
			-- Void if none.
			-- (from EV_PIXMAPABLE)
		require -- from EV_PIXMAPABLE
			not_destroyed: not is_destroyed
		ensure -- from EV_PIXMAPABLE
			bridge_ok: (Result = Void and implementation.pixmap = Void) or Result.is_equal (implementation.pixmap)

	retrieve_item_by_data (some_data: ANY; should_compare_objects: BOOLEAN): EV_TREE_NODE
			-- `Result' is first item in `Current' with data
			-- matching `some_data'. Compare objects if
			-- `should_compare_objects' otherwise compare references.
			-- (from EV_DYNAMIC_LIST)
		ensure -- from EV_DYNAMIC_LIST
			not_found_in_empty: Result /= Void implies not is_empty
			index_not_changed: old index = index

	retrieve_item_recursively_by_data (some_data: ANY; should_compare_objects: BOOLEAN): EV_TREE_NODE
			-- If data contained in a tree item at any level then
			-- assign this item to `Result'. Compare objects if
			-- `should_compare_objects' otherwise compare references.
			-- (from EV_TREE_NODE_LIST)
		ensure -- from EV_TREE_NODE_LIST
			not_found_in_empty: Result /= Void implies not is_empty
			index_not_changed: old index = index

	retrieve_items_by_data (some_data: ANY; should_compare_objects: BOOLEAN): ARRAYED_LIST [EV_TREE_NODE]
			-- `Result' is all items in `Current' with data
			-- matching `some_data'. Compare objects if
			-- `should_compare_objects' otherwise compare references.
			-- (from EV_DYNAMIC_LIST)
		ensure -- from EV_DYNAMIC_LIST
			result_not_void: Result /= Void
			not_found_in_empty: not Result.is_empty implies not is_empty
			index_not_changed: old index = index

	retrieve_items_recursively_by_data (some_data: ANY; should_compare_objects: BOOLEAN): ARRAYED_LIST [EV_TREE_NODE]
			-- `Result' is all tree items contained in `Current' at any level
			-- with data matching `some_data'. Compare objects if
			-- `should_compare_objects' otherwise compare references.
			-- (from EV_TREE_NODE_LIST)
		ensure -- from EV_TREE_NODE_LIST
			result_not_void: Result /= Void
			not_found_in_empty: not Result.is_empty implies not is_empty
			index_not_changed: old index = index

	target_data_function: FUNCTION [ANY, TUPLE [ANY], EV_PND_TARGET_DATA]
			-- Function for computing target meta data based on source pebble.
			-- Primarily used for Pick and Drop target menu.
			-- (from EV_ABSTRACT_PICK_AND_DROPABLE)

	target_name: STRING_GENERAL
			-- Optional textual name describing `Current' pick and drop hole.
			-- (from EV_ABSTRACT_PICK_AND_DROPABLE)

	text: STRING_32
			-- Text displayed in textable.
			-- (from EV_TEXTABLE)
		require -- from EV_TEXTABLE
			not_destroyed: not is_destroyed
		ensure -- from EV_TEXTABLE
			bridge_ok: equal (Result, implementation.text)
			not_void: Result /= Void
			cloned: Result /= implementation.text
			no_carriage_returns: not Result.has ('%R')

	tooltip: STRING_32
			-- Tooltip displayed on `Current'.
			-- If `Result' is empty then no tooltip displayed.
			-- (from EV_TOOLTIPABLE)
		require -- from EV_TOOLTIPABLE
			not_destroyed: not is_destroyed
		ensure -- from EV_TOOLTIPABLE
			bridge_ok: is_bridge_ok (Result)
			not_void: Result /= Void
			cloned: is_cloned (Result)

	infix "@" (i: INTEGER_32): like item assign put_i_th
			-- Item at `i'-th position
			-- Was declared in CHAIN as synonym of i_th.
			-- (from CHAIN)
		require -- from TABLE
			valid_key: valid_index (i)
	
feature -- Measurement

	count: INTEGER_32
			-- Number of items.
			-- (from EV_DYNAMIC_LIST)
		require -- from  FINITE
			True
		require -- from  SET
			True
		ensure then -- from EV_DYNAMIC_LIST
			bridge_ok: Result = implementation.count

	height: INTEGER_32
			-- Vertical size in pixels.
			-- Same as minimum_height when not displayed.
			-- (from EV_POSITIONED)
		require -- from EV_POSITIONED
			not_destroyed: not is_destroyed
		ensure -- from EV_POSITIONED
			bridge_ok: Result = implementation.height

	index_set: INTEGER_INTERVAL
			-- Range of acceptable indexes
			-- (from CHAIN)
		require -- from  INDEXABLE
			True
		ensure -- from INDEXABLE
			not_void: Result /= Void
		ensure then -- from CHAIN
			count_definition: Result.count = count

	minimum_height: INTEGER_32
			-- Lower bound on height in pixels.
			-- (from EV_POSITIONED)
		require -- from EV_POSITIONED
			not_destroyed: not is_destroyed
		ensure -- from EV_POSITIONED
			bridge_ok: Result = implementation.minimum_height
			positive_or_zero: Result >= 0

	minimum_width: INTEGER_32
			-- Lower bound on width in pixels.
			-- (from EV_POSITIONED)
		require -- from EV_POSITIONED
			not_destroyed: not is_destroyed
		ensure -- from EV_POSITIONED
			bridge_ok: Result = implementation.minimum_width
			positive_or_zero: Result >= 0

	occurrences (v: like item): INTEGER_32
			-- Number of times `v' appears.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from CHAIN)
		require -- from  BAG
			True
		require -- from  LINEAR
			True
		ensure -- from BAG
			non_negative_occurrences: Result >= 0

	screen_x: INTEGER_32
			-- Horizontal offset relative to screen.
			-- (from EV_POSITIONED)
		require -- from EV_POSITIONED
			not_destroyed: not is_destroyed
		ensure -- from EV_POSITIONED
			bridge_ok: Result = implementation.screen_x

	screen_y: INTEGER_32
			-- Vertical offset relative to screen.
			-- (from EV_POSITIONED)
		require -- from EV_POSITIONED
			not_destroyed: not is_destroyed
		ensure -- from EV_POSITIONED
			bridge_ok: Result = implementation.screen_y

	width: INTEGER_32
			-- Horizontal size in pixels.
			-- Same as minimum_width when not displayed.
			-- (from EV_POSITIONED)
		require -- from EV_POSITIONED
			not_destroyed: not is_destroyed
		ensure -- from EV_POSITIONED
			bridge_ok: Result = implementation.width

	x_position: INTEGER_32
			-- Horizontal offset relative to parent x_position in pixels.
			-- (from EV_POSITIONED)
		require -- from EV_POSITIONED
			not_destroyed: not is_destroyed
		ensure -- from EV_POSITIONED
			bridge_ok: Result = implementation.x_position

	y_position: INTEGER_32
			-- Vertical offset relative to parent y_position in pixels.
			-- (from EV_POSITIONED)
		require -- from EV_POSITIONED
			not_destroyed: not is_destroyed
		ensure -- from EV_POSITIONED
			bridge_ok: Result = implementation.y_position
	
feature -- Comparison

	frozen deep_equal (some: ?ANY; other: like arg #1): BOOLEAN
			-- Are `some' and `other' either both void
			-- or attached to isomorphic object structures?
			-- (from ANY)
		ensure -- from ANY
			shallow_implies_deep: standard_equal (some, other) implies Result
			both_or_none_void: (some = Void) implies (Result = (other = Void))
			same_type: (Result and (some /= Void)) implies (other /= Void and then some.same_type (other))
			symmetric: Result implies deep_equal (other, some)

	frozen equal (some: ?ANY; other: like arg #1): BOOLEAN
			-- Are `some' and `other' either both void or attached
			-- to objects considered equal?
			-- (from ANY)
		ensure -- from ANY
			definition: Result = (some = Void and other = Void) or else ((some /= Void and other /= Void) and then some.is_equal (other))

	frozen is_deep_equal (other: EV_TREE_NODE): BOOLEAN
			-- Are `Current' and `other' attached to isomorphic object structures?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		ensure -- from ANY
			shallow_implies_deep: standard_is_equal (other) implies Result
			same_type: Result implies same_type (other)
			symmetric: Result implies other.is_deep_equal (Current)

	is_equal (other: EV_TREE_NODE): BOOLEAN
			-- Does `other' contain the same elements?
			-- (from LIST)
		require -- from ANY
			other_not_void: other /= Void
		ensure -- from ANY
			symmetric: Result implies other.is_equal (Current)
			consistent: standard_is_equal (other) implies Result
		ensure then -- from LIST
			indices_unchanged: index = old index and other.index = old other.index
			true_implies_same_size: Result implies count = other.count

	frozen standard_equal (some: ?ANY; other: like arg #1): BOOLEAN
			-- Are `some' and `other' either both void or attached to
			-- field-by-field identical objects of the same type?
			-- Always uses default object comparison criterion.
			-- (from ANY)
		ensure -- from ANY
			definition: Result = (some = Void and other = Void) or else ((some /= Void and other /= Void) and then some.standard_is_equal (other))

	frozen standard_is_equal (other: EV_TREE_NODE): BOOLEAN
			-- Is `other' attached to an object of the same type
			-- as current object, and field-by-field identical to it?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		ensure -- from ANY
			same_type: Result implies same_type (other)
			symmetric: Result implies other.standard_is_equal (Current)
	
feature -- Status report

	after: BOOLEAN
			-- Is there no valid cursor position to the right of cursor?
			-- (from LIST)
		require -- from  LINEAR
			True

	before: BOOLEAN
			-- Is there no valid cursor position to the left of cursor?
			-- (from LIST)
		require -- from  BILINEAR
			True

	conforms_to (other: ANY): BOOLEAN
			-- Does type of current object conform to type
			-- of `other' (as per Eiffel: The Language, chapter 13)?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void

	exhausted: BOOLEAN
			-- Has structure been completely explored?
			-- (from LINEAR)
		ensure -- from LINEAR
			exhausted_when_off: off implies Result

	extendible: BOOLEAN is True
			-- May new items be added? (Answer: yes.)
			-- (from DYNAMIC_CHAIN)

	full: BOOLEAN is False
			-- Is structured filled to capacity? (Answer: no.)
			-- (from EV_DYNAMIC_LIST)

	has_identifier_name_set: BOOLEAN
			-- Is a specific identifier name set?
			-- (from EV_IDENTIFIABLE)

	has_parent: BOOLEAN
			-- Does identifiable has a parent?
			-- (from EV_IDENTIFIABLE)

	is_empty: BOOLEAN
			-- Is structure empty?
			-- (from FINITE)
		require -- from  CONTAINER
			True

	is_expanded: BOOLEAN
			-- Are items in `Current' displayed?
		require
			not_destroyed: not is_destroyed

	is_inserted (v: EV_TREE_NODE): BOOLEAN
			-- Has `v' been inserted by the most recent insertion?
			-- (By default, the value returned is equivalent to calling 
			-- `has (v)'. However, descendants might be able to provide more
			-- efficient implementations.)
			-- (from COLLECTION)

	is_selectable: BOOLEAN
			-- May enable_select be called?
			-- (from EV_SELECTABLE)
		require -- from EV_SELECTABLE
			not_destroyed: not is_destroyed

	is_selected: BOOLEAN
			-- Is selected?
			-- (from EV_SELECTABLE)
		require -- from EV_SELECTABLE
			not_destroyed: not is_destroyed
		ensure -- from EV_SELECTABLE
			bridge_ok: is_selectable implies Result = implementation.is_selected

	isfirst: BOOLEAN
			-- Is cursor at first position?
			-- (from CHAIN)
		ensure -- from CHAIN
			valid_position: Result implies not is_empty

	islast: BOOLEAN
			-- Is cursor at last position?
			-- (from CHAIN)
		ensure -- from CHAIN
			valid_position: Result implies not is_empty

	mode_is_configurable_target_menu: BOOLEAN
			-- Is the user interface mode a configurable pop-up menu of targets?
			-- (from EV_PICK_AND_DROPABLE)
		require -- from EV_PICK_AND_DROPABLE
			not_destroyed: not is_destroyed
		ensure then -- from EV_PICK_AND_DROPABLE
			bridge_ok: Result = implementation.mode_is_configurable_target_menu

	mode_is_drag_and_drop: BOOLEAN
			-- Is the user interface mode drag and drop?
			-- (from EV_PICK_AND_DROPABLE)
		require -- from EV_PICK_AND_DROPABLE
			not_destroyed: not is_destroyed
		ensure then -- from EV_PICK_AND_DROPABLE
			bridge_ok: Result = implementation.mode_is_drag_and_drop

	mode_is_pick_and_drop: BOOLEAN
			-- Is the user interface mode pick and drop?
			-- (from EV_PICK_AND_DROPABLE)
		require -- from EV_PICK_AND_DROPABLE
			not_