    indexing
    	description: "[
    		Item for use with EV_TREE.
    		A tree item is also a tree-item container because if
    		we create a tree-item with a tree-item as parent, the
    		parent will become a subtree.
    	]"
    	legal: "See notice at end of class."
    	status: "See notice at end of class."
    	keywords: "tree, item, leaf, node, branch"
    	date: "$Date: 2006-01-22 18:25:44 -0800 (Sun, 22 Jan 2006) $"
    	revision: "$Revision: 56675 $"

    class interface
    	EV_TREE_ITEM

    create
    	default_create
    			-- Standard creation procedure.
    			-- (from EV_ANY)
    		require -- from  ANY
    			True
    		ensure then -- from EV_ANY
    			is_coupled: implementation /= Void
    			is_initialized: is_initialized
    			default_create_called_set: default_create_called
    			is_in_default_state: is_in_default_state

    	make_with_text (a_text: STRING_GENERAL)
    			-- Create `Current' and assign `a_text' to text
    			-- (from EV_TEXTABLE)
    		require -- from EV_TEXTABLE
    			a_text_not_void: a_text /= Void
    		ensure -- from EV_TEXTABLE
    			text_assigned: text.is_equal (a_text) and text /= a_text

    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

    	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)

    	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

    	generating_type: STRING_8
    			-- Name of current object's generating type
    			-- (type of which it is a direct instance)
    			-- (from ANY)

    	generator: STRING_8
    			-- Name of current object's generating class
    			-- (base class of the type of which it is a direct instance)
    			-- (from ANY)

    	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

    	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)

    	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: 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'.
    			-- (from EV_TREE_NODE)
    		require -- from EV_CONTAINABLE
    			not_destroyed: not is_destroyed
    		ensure then -- from EV_ITEM
    			bridge_ok: Result = implementation.parent

    	parent_tree: EV_TREE
    			-- Contains `Current'.
    			-- (from EV_TREE_NODE)
    		require -- from EV_TREE_NODE
    			not_destroyed: not is_destroyed
    		ensure -- from EV_TREE_NODE
    			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_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: equal (Result, implementation.tooltip)
    			not_void: Result /= Void
    			cloned: Result /= implementation.tooltip

    	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

    	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

    	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

    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 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))

    	is_equal (other: like Current): 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: like Current): 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)

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

    	is_expanded: BOOLEAN
    			-- Are items in `Current' displayed?
    			-- (from EV_TREE_NODE)
    		require -- from EV_TREE_NODE
    			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_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_destroyed: not is_destroyed
    		ensure then -- from EV_PICK_AND_DROPABLE
    			bridge_ok: Result = implementation.mode_is_pick_and_drop

    	mode_is_target_menu: BOOLEAN
    			-- Is the user interface mode a 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_target_menu

    	object_comparison: BOOLEAN
    			-- Must search operations use equal rather than `='
    			-- for comparing references? (Default: no, use `='.)
    			-- (from CONTAINER)

    	off: BOOLEAN
    			-- Is there no current item?
    			-- (from CHAIN)
    		require -- from  TRAVERSABLE
    			True

    	prunable: BOOLEAN
    			-- May items be removed? (Answer: yes.)
    			-- (from DYNAMIC_CHAIN)
    		require -- from  COLLECTION
    			True

    	readable: BOOLEAN
    			-- Is there a current item that may be read?
    			-- (from SEQUENCE)
    		require -- from  ACTIVE
    			True

    	same_type (other: ANY): BOOLEAN
    			-- Is type of current object identical to type of `other'?
    			-- (from ANY)
    		require -- from ANY
    			other_not_void: other /= Void
    		ensure -- from ANY
    			definition: Result = (conforms_to (other) and other.conforms_to (Current))

    	valid_cursor (p: CURSOR): BOOLEAN
    			-- Can the cursor be moved to position `p'?
    			-- This is True if `p' conforms to EV_DYNAMIC_LIST_CURSOR and
    			-- if it points to an item, `Current' must have it.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from  CURSOR_STRUCTURE
    			True
    		ensure then -- from EV_DYNAMIC_LIST
    			bridge_ok: Result = implementation.valid_cursor (p)

    	valid_cursor_index (i: INTEGER_32): BOOLEAN
    			-- Is `i' correctly bounded for cursor movement?
    			-- (from CHAIN)
    		ensure -- from CHAIN
    			valid_cursor_index_definition: Result = ((i >= 0) and (i <= count + 1))

    	valid_index (i: INTEGER_32): BOOLEAN
    			-- Is `i' within allowable bounds?
    			-- (from CHAIN)
    		require -- from  TABLE
    			True
    		ensure then -- from INDEXABLE
    			only_if_in_index_set: Result implies ((i >= index_set.lower) and (i <= index_set.upper))
    		ensure then -- from CHAIN
    			valid_index_definition: Result = ((i >= 1) and (i <= count))

    	writable: BOOLEAN
    			-- Is there a current item that may be modified?
    			-- (from SEQUENCE)
    		require -- from  ACTIVE
    			True

    feature -- Status setting

    	collapse
    			-- Set is_expanded `False'.
    			-- (from EV_TREE_NODE)
    		require -- from EV_TREE_NODE
    			not_destroyed: not is_destroyed
    			is_collapsable: is_expandable
    		ensure -- from EV_TREE_NODE
    			not_is_expanded: not is_expanded

    	compare_objects
    			-- Ensure that future search operations will use equal
    			-- rather than `=' for comparing references.
    			-- (from CONTAINER)
    		require -- from CONTAINER
    			changeable_comparison_criterion: changeable_comparison_criterion
    		ensure -- from CONTAINER
    			object_comparison

    	compare_references
    			-- Ensure that future search operations will use `='
    			-- rather than equal for comparing references.
    			-- (from CONTAINER)
    		require -- from CONTAINER
    			changeable_comparison_criterion: changeable_comparison_criterion
    		ensure -- from CONTAINER
    			reference_comparison: not object_comparison

    	disable_pebble_positioning
    			-- Assign `False' to pebble_positioning_enabled.
    			-- The pick and drop will start at the pointer position.
    			-- (from EV_PICK_AND_DROPABLE)
    		require -- from EV_PICK_AND_DROPABLE
    			not_destroyed: not is_destroyed
    		ensure -- from EV_PICK_AND_DROPABLE
    			pebble_positioning_updated: not pebble_positioning_enabled

    	disable_select
    			-- Deselect the object.
    			-- (from EV_DESELECTABLE)
    		require -- from EV_DESELECTABLE
    			not_destroyed: not is_destroyed
    		ensure -- from EV_DESELECTABLE
    			unselected: not is_selected

    	enable_pebble_positioning
    			-- Assign `True' to pebble_positioning_enabled.
    			-- Use pebble_x_position and pebble_y_position as the initial coordinates
    			-- for the pick and drop in pixels relative to `Current'.
    			-- (from EV_PICK_AND_DROPABLE)
    		require -- from EV_PICK_AND_DROPABLE
    			not_destroyed: not is_destroyed
    		ensure -- from EV_PICK_AND_DROPABLE
    			pebble_positioning_updated: pebble_positioning_enabled

    	enable_select
    			-- Make is_selected True.
    			-- (from EV_SELECTABLE)
    		require -- from EV_SELECTABLE
    			not_destroyed: not is_destroyed
    			is_selectable: is_selectable
    		ensure -- from EV_SELECTABLE
    			is_selected: is_selected

    	expand
    			-- Set is_expanded `True'.
    			-- (from EV_TREE_NODE)
    		require -- from EV_TREE_NODE
    			not_destroyed: not is_destroyed
    			is_expandable: is_expandable
    		ensure -- from EV_TREE_NODE
    			is_expanded: is_expanded

    	remove_pebble
    			-- Make pebble `Void' and pebble_function `Void,
    			-- Removing transport.
    			-- (from EV_PICK_AND_DROPABLE)
    		ensure -- from EV_ABSTRACT_PICK_AND_DROPABLE
    			pebble_removed: pebble = Void and pebble_function = Void

    	set_accept_cursor (a_cursor: like accept_cursor)
    			-- Set `a_cursor' to be 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
    			a_cursor_not_void: a_cursor /= Void
    		ensure -- from EV_ABSTRACT_PICK_AND_DROPABLE
    			accept_cursor_assigned: accept_cursor.is_equal (a_cursor)

    	set_deny_cursor (a_cursor: like deny_cursor)
    			-- Set `a_cursor' to be displayed when the screen pointer is not
    			-- over a valid target.
    			-- (from EV_PICK_AND_DROPABLE)
    		require -- from EV_ABSTRACT_PICK_AND_DROPABLE
    			a_cursor_not_void: a_cursor /= Void
    		ensure -- from EV_ABSTRACT_PICK_AND_DROPABLE
    			deny_cursor_assigned: deny_cursor.is_equal (a_cursor)

    	set_drag_and_drop_mode
    			-- Set user interface mode to drag and drop.
    			-- (from EV_PICK_AND_DROPABLE)
    		require -- from EV_PICK_AND_DROPABLE
    			not_destroyed: not is_destroyed
    		ensure -- from EV_PICK_AND_DROPABLE
    			drag_and_drop_set: mode_is_drag_and_drop

    	set_pebble (a_pebble: like pebble)
    			-- Assign `a_pebble' to pebble.
    			-- Overrides set_pebble_function.
    			-- (from EV_PICK_AND_DROPABLE)
    		require -- from EV_ABSTRACT_PICK_AND_DROPABLE
    			a_pebble_not_void: a_pebble /= Void
    		ensure -- from EV_ABSTRACT_PICK_AND_DROPABLE
    			pebble_assigned: pebble = a_pebble

    	set_pebble_function (a_function: FUNCTION [ANY, TUPLE, ANY])
    			-- Set `a_function' to compute pebble.
    			-- It will be called once each time a pick occurs, the result
    			-- will be assigned to pebble for the duration of transport.
    			-- When a pick occurs, the pick position in widget coordinates,
    			-- <<x, y>> in pixels, is passed.
    			-- To handle this data use `a_function' of type
    			-- FUNCTION [ANY, TUPLE [INTEGER, INTEGER], ANY] and return the
    			-- pebble as a function of x and y.
    			-- Overrides set_pebble.
    			-- (from EV_PICK_AND_DROPABLE)
    		require -- from EV_ABSTRACT_PICK_AND_DROPABLE
    			a_function_not_void: a_function /= Void
    			a_function_takes_two_integer_open_operands: a_function.valid_operands ([1, 1])
    		ensure -- from EV_ABSTRACT_PICK_AND_DROPABLE
    			pebble_function_assigned: pebble_function = a_function

    	set_pebble_position (a_x, a_y: INTEGER_32)
    			-- Set the initial position for pick and drop
    			-- Coordinates are in pixels and are relative to position of `Current'.
    			-- Pebble_positioning_enabled must be `True' for the position to be used,
    			-- use enable_pebble_positioning.
    			-- (from EV_PICK_AND_DROPABLE)
    		require -- from EV_PICK_AND_DROPABLE
    			not_destroyed: not is_destroyed
    		ensure -- from EV_PICK_AND_DROPABLE
    			pebble_position_assigned: pebble_x_position = a_x and pebble_y_position = a_y

    	set_pick_and_drop_mode
    			-- Set user interface mode to pick and drop.
    			-- (from EV_PICK_AND_DROPABLE)
    		require -- from EV_PICK_AND_DROPABLE
    			not_destroyed: not is_destroyed
    		ensure -- from EV_PICK_AND_DROPABLE
    			pick_and_drop_set: mode_is_pick_and_drop

    	set_target_menu_mode
    			-- Set user interface mode to pop-up menu of targets.
    			-- (from EV_PICK_AND_DROPABLE)
    		require -- from EV_PICK_AND_DROPABLE
    			not_destroyed: not is_destroyed
    		ensure -- from EV_PICK_AND_DROPABLE
    			target_menu_mode_set: mode_is_target_menu

    	set_target_name (a_name: STRING_GENERAL)
    			-- Assign `a_name' to target_name.
    			-- (from EV_ABSTRACT_PICK_AND_DROPABLE)
    		require -- from EV_ABSTRACT_PICK_AND_DROPABLE
    			a_name_not_void: a_name /= Void
    		ensure -- from EV_ABSTRACT_PICK_AND_DROPABLE
    			target_name_assigned: a_name /= target_name and a_name.is_equal (target_name)

    	toggle
    			-- Change is_selected.
    			-- (from EV_DESELECTABLE)
    		require -- from EV_DESELECTABLE
    			not_is_destroyed: not is_destroyed
    			can_be_selected: not is_selected implies is_selectable
    		ensure -- from EV_DESELECTABLE
    			is_selected_changed: is_selected /= old is_selected

    feature -- Cursor movement

    	back
    			-- Move to previous position.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from BILINEAR
    			not_before: not before

    	finish
    			-- Move cursor to last position.
    			-- (No effect if empty)
    			-- (from CHAIN)
    		require -- from  LINEAR
    			True
    		ensure then -- from CHAIN
    			at_last: not is_empty implies islast

    	forth
    			-- Move cursor to next position.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from LINEAR
    			not_after: not after
    		ensure then -- from LIST
    			moved_forth: index = old index + 1

    	go_i_th (i: INTEGER_32)
    			-- Move cursor to `i'-th position.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from CHAIN
    			valid_cursor_index: valid_cursor_index (i)
    		ensure -- from CHAIN
    			position_expected: index = i

    	go_to (p: CURSOR)
    			-- Move cursor to position `p'.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from CURSOR_STRUCTURE
    			cursor_position_valid: valid_cursor (p)

    	move (i: INTEGER_32)
    			-- Move cursor `i' positions.
    			-- (from EV_DYNAMIC_LIST)
    		ensure -- from CHAIN
    			too_far_right: (old index + i > count) implies exhausted
    			too_far_left: (old index + i < 1) implies exhausted
    			expected_index: (not exhausted) implies (index = old index + i)

    	search (v: like item)
    			-- Move to first position (at or after current
    			-- position) where item and `v' are equal.
    			-- If structure does not include `v' ensure that
    			-- exhausted will be true.
    			-- (Reference or object equality,
    			-- based on object_comparison.)
    			-- (from BILINEAR)
    		ensure -- from LINEAR
    			object_found: (not exhausted and object_comparison) implies equal (v, item)
    			item_found: (not exhausted and not object_comparison) implies v = item

    	start
    			-- Move cursor to first position.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from  TRAVERSABLE
    			True
    		ensure then -- from CHAIN
    			at_first: not is_empty implies isfirst
    		ensure then -- from EV_DYNAMIC_LIST
    			empty_implies_after: is_empty implies after

    feature -- Element change

    	append (s: SEQUENCE [like item])
    			-- Append a copy of `s'. Do not move cursor.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from EV_DYNAMIC_LIST
    			not_destroyed: not is_destroyed
    			extendible: extendible
    			sequence_not_void: s /= Void
    			sequence_not_current: s /= Current
    			not_parented: not s.there_exists (agent (v: like item): BOOLEAN
    			)
    		ensure -- from EV_DYNAMIC_LIST
    			count_increased: old count + s.count = count
    			cursor_not_moved: (index = old index) or (after and old after)

    	extend (v: like item)
    			-- Add `v' to end. Do not move cursor.
    			-- Was declared in EV_DYNAMIC_LIST as synonym of force.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from EV_DYNAMIC_LIST
    			not_destroyed: not is_destroyed
    			extendible: extendible
    			v_not_void: v /= Void
    			v_parent_void: v.parent = Void
    			v_not_current: not same (v)
    			v_not_parent_of_current: not is_parent_recursive (v)
    		ensure -- from EV_DYNAMIC_LIST
    			parent_is_current: v.parent = Current
    			v_is_last: v = last
    			count_increased: count = old count + 1
    			cursor_not_moved: (index = old index) or (after and old after)

    	fill (other: CONTAINER [EV_TREE_NODE])
    			-- Fill with as many items of `other' as possible.
    			-- The representations of `other' and current structure
    			-- need not be the same.
    			-- (from CHAIN)
    		require -- from COLLECTION
    			other_not_void: other /= Void
    			extendible: extendible

    	force (v: like item)
    			-- Add `v' to end. Do not move cursor.
    			-- Was declared in EV_DYNAMIC_LIST as synonym of extend.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from EV_DYNAMIC_LIST
    			not_destroyed: not is_destroyed
    			extendible: extendible
    			v_not_void: v /= Void
    			v_parent_void: v.parent = Void
    			v_not_current: not same (v)
    			v_not_parent_of_current: not is_parent_recursive (v)
    		ensure -- from EV_DYNAMIC_LIST
    			parent_is_current: v.parent = Current
    			v_is_last: v = last
    			count_increased: count = old count + 1
    			cursor_not_moved: (index = old index) or (after and old after)

    	dl_force (v: like item)
    			-- Add `v' to end.
    			-- (from SEQUENCE)
    		require -- from SEQUENCE
    			extendible: extendible
    		ensure then -- from SEQUENCE
    			new_count: count = old count + 1
    			item_inserted: has (v)

    	merge_left (other: like Current)
    			-- Merge `other' into current structure before cursor
    			-- position. Do not move cursor. Empty `other'.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from DYNAMIC_CHAIN
    			extendible: extendible
    			not_before: not before
    			other_exists: other /= Void
    			not_current: other /= Current
    		ensure -- from DYNAMIC_CHAIN
    			new_count: count = old count + old other.count
    			new_index: index = old index + old other.count
    			other_is_empty: other.is_empty

    	merge_right (other: like Current)
    			-- Merge `other' into current structure after cursor
    			-- position. Do not move cursor. Empty `other'.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from DYNAMIC_CHAIN
    			extendible: extendible
    			not_after: not after
    			other_exists: other /= Void
    			not_current: other /= Current
    		ensure -- from DYNAMIC_CHAIN
    			new_count: count = old count + old other.count
    			same_index: index = old index
    			other_is_empty: other.is_empty

    	put (v: like item)
    			-- Replace current item by `v'.
    			-- (Synonym for replace)
    			-- (from CHAIN)
    		require -- from COLLECTION
    			extendible: extendible
    		ensure -- from COLLECTION
    			item_inserted: is_inserted (v)
    		ensure then -- from SET
    			in_set_already: old has (v) implies (count = old count)
    			added_to_set: not old has (v) implies (count = old count + 1)
    		ensure then -- from CHAIN
    			same_count: count = old count

    	put_front (v: like item)
    			-- Add `v' at beginning. Do not move cursor.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from EV_DYNAMIC_LIST
    			not_destroyed: not is_destroyed
    			extendible: extendible
    			v_not_void: v /= Void
    			v_parent_void: v.parent = Void
    			v_not_current: not same (v)
    			v_not_parent_of_current: not is_parent_recursive (v)
    		ensure -- from EV_DYNAMIC_LIST
    			parent_is_current: v.parent = Current
    			v_is_first: v = first
    			count_increased: count = old count + 1
    			cursor_not_moved: (index = old index + 1) or (before and old before)

    	put_i_th (v: like item; i: INTEGER_32)
    			-- Replace item at `i'-th position by `v'.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from EV_DYNAMIC_LIST
    			not_destroyed: not is_destroyed
    			valid_index: i > 0 and i <= count
    			v_not_void: v /= Void
    			v_parent_void: v.parent = Void
    			v_not_current: not same (v)
    			v_not_parent_of_current: not is_parent_recursive (v)
    		ensure -- from EV_DYNAMIC_LIST
    			parent_is_current: v.parent = Current
    			item_replaced: v = i_th (i)
    			not_has_old_item: not has (old i_th (i))
    			old_item_parent_void: (old i_th (i)).parent = Void
    			count_same: count = old count
    			cursor_not_moved: index = old index

    	put_left (v: like item)
    			-- Add `v' to the left of cursor position. Do not move cursor.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from EV_DYNAMIC_LIST
    			not_destroyed: not is_destroyed
    			extendible: extendible
    			not_before: not before
    			v_not_void: v /= Void
    			v_parent_void: v.parent = Void
    			v_not_current: not same (v)
    			v_not_parent_of_current: not is_parent_recursive (v)
    		ensure -- from EV_DYNAMIC_LIST
    			parent_is_current: v.parent = Current
    			v_at_index_plus_one: v = i_th (index - 1)
    			count_increased: count = old count + 1
    			cursor_not_moved: index = old index + 1

    	put_right (v: like item)
    			-- Add `v' to right of cursor position. Do not move cursor.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from EV_DYNAMIC_LIST
    			not_destroyed: not is_destroyed
    			extendible: extendible
    			not_after: not after
    			v_not_void: v /= Void
    			v_parent_void: v.parent = Void
    			v_not_current: not same (v)
    			v_not_parent_of_current: not is_parent_recursive (v)
    		ensure -- from EV_DYNAMIC_LIST
    			parent_is_current: v.parent = Current
    			v_at_index_plus_one: v = i_th (index + 1)
    			count_increased: count = old count + 1
    			cursor_not_moved: index = old index

    	remove_pixmap
    			-- Remove image displayed on `Current'.
    			-- (from EV_PIXMAPABLE)
    		require -- from EV_PIXMAPABLE
    			not_destroyed: not is_destroyed
    		ensure -- from EV_PIXMAPABLE
    			pixmap_removed: pixmap = Void

    	remove_text
    			-- Make text is_empty.
    			-- (from EV_TEXTABLE)
    		require -- from EV_TEXTABLE
    			not_destroyed: not is_destroyed
    		ensure -- from EV_TEXTABLE
    			text_empty: text.is_empty

    	remove_tooltip
    			-- Make tooltip empty.
    			-- (from EV_TOOLTIPABLE)
    		require -- from EV_TOOLTIPABLE
    			not_destroyed: not is_destroyed
    		ensure -- from EV_TOOLTIPABLE
    			tooltip_removed: tooltip.is_empty

    	replace (v: like item)
    			-- Replace current item by `v'.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from EV_DYNAMIC_LIST
    			not_destroyed: not is_destroyed
    			writable: writable
    			v_not_void: v /= Void
    			v_parent_void: v.parent = Void
    			v_not_current: not same (v)
    			v_not_parent_of_current: not is_parent_recursive (v)
    		ensure -- from EV_DYNAMIC_LIST
    			parent_is_current: v.parent = Current
    			item_replaced: v = item
    			not_has_old_item: not has (old item)
    			old_item_parent_void: (old item).parent = Void
    			count_same: count = old count
    			cursor_not_moved: index = old index

    	set_data (some_data: like data)
    			-- Assign `some_data' to data.
    			-- (from EV_ANY)
    		require -- from EV_ANY
    			not_destroyed: not is_destroyed
    		ensure -- from EV_ANY
    			data_assigned: data = some_data

    	set_pixmap (a_pixmap: EV_PIXMAP)
    			-- Display image of `a_pixmap' on `Current'.
    			-- Image of pixmap will be a copy of `a_pixmap'.
    			-- Image may be scaled in some descendents, i.e EV_TREE_ITEM
    			-- See EV_TREE.set_pixmaps_size.
    			-- (from EV_PIXMAPABLE)
    		require -- from EV_PIXMAPABLE
    			not_destroyed: not is_destroyed
    			pixmap_not_void: a_pixmap /= Void

    	set_text (a_text: STRING_GENERAL)
    			-- Assign `a_text' to text.
    			-- (from EV_TEXTABLE)
    		require -- from EV_TEXTABLE
    			not_destroyed: not is_destroyed
    			a_text_not_void: a_text /= Void
    			no_carriage_returns: not a_text.has_code (('%R').natural_32_code)
    		ensure -- from EV_TEXTABLE
    			text_cloned: text.is_equal (a_text) and then text /= a_text

    	set_tooltip (a_tooltip: STRING_GENERAL)
    			-- Assign `a_tooltip' to tooltip.
    			-- (from EV_TOOLTIPABLE)
    		require -- from EV_TOOLTIPABLE
    			not_destroyed: not is_destroyed
    			tooltip: a_tooltip /= Void
    		ensure -- from EV_TOOLTIPABLE
    			tooltip_assigned: tooltip.is_equal (a_tooltip)
    			cloned: tooltip /= a_tooltip

    	swap (i: INTEGER_32)
    			-- Exchange_item at `i'-th position with item
    			-- at cursor position.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from CHAIN
    			not_off: not off
    			valid_index: valid_index (i)
    		ensure -- from CHAIN
    			swapped_to_item: item = old i_th (i)
    			swapped_from_item: i_th (i) = old item

    feature -- Removal

    	prune (v: like item)
    			-- Remove `v' if present. Do not move cursor, except if
    			-- cursor was on `v', move to right neighbor.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from COLLECTION
    			prunable: prunable
    		ensure then -- from SET
    			removed_count_change: old has (v) implies (count = old count - 1)
    			not_removed_no_count_change: not old has (v) implies (count = old count)
    			item_deleted: not has (v)
    		ensure then -- from EV_DYNAMIC_LIST
    			not_has_v: not has (v)
    			had_item_implies_parent_void: old has (v) implies v.parent = Void
    			had_item_implies_count_decreased: old has (v) implies count = old count - 1
    			had_item_and_was_after_implies_index_decreased: (old after and old has (v)) implies index = old index - 1

    	prune_all (v: like item)
    			-- Remove all occurrences of `v'.
    			-- (Reference or object equality,
    			-- based on object_comparison.)
    			-- Leave structure exhausted.
    			-- (from DYNAMIC_CHAIN)
    		require -- from COLLECTION
    			prunable: prunable
    		ensure -- from COLLECTION
    			no_more_occurrences: not has (v)
    		ensure then -- from DYNAMIC_CHAIN
    			is_exhausted: exhausted

    	remove
    			-- Remove current item. Move cursor to right neighbor.
    			-- (or after if no right neighbor).
    			-- (from EV_DYNAMIC_LIST)
    		require -- from ACTIVE
    			prunable: prunable
    			writable: writable
    		ensure then -- from DYNAMIC_LIST
    			after_when_empty: is_empty implies after
    		ensure then -- from EV_DYNAMIC_LIST
    			v_removed: not has (old item)
    			parent_void: (old item).parent = Void
    			count_decreased: count = old count - 1
    			index_same: index = old index

    	remove_left
    			-- Remove item to left of cursor position.
    			-- Do not move cursor.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from DYNAMIC_CHAIN
    			left_exists: index > 1
    		ensure -- from DYNAMIC_CHAIN
    			new_count: count = old count - 1
    			new_index: index = old index - 1
    		ensure then -- from EV_DYNAMIC_LIST
    			left_neighbor_removed: not has (old i_th (index - 1))
    			parent_void: (old i_th (index - 1)).parent = Void
    			index_decreased: index = old index - 1

    	remove_right
    			-- Remove item to right of cursor position.
    			-- Do not move cursor.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from DYNAMIC_CHAIN
    			right_exists: index < count
    		ensure -- from DYNAMIC_CHAIN
    			new_count: count = old count - 1
    			same_index: index = old index
    		ensure then -- from EV_DYNAMIC_LIST
    			right_neighbor_removed: not has (old i_th (index + 1))
    			parent_void: (old i_th (index + 1)).parent = Void
    			index_same: index = old index

    	wipe_out
    			-- Remove all items.
    			-- (from EV_DYNAMIC_LIST)
    		require -- from COLLECTION
    			prunable: prunable
    		ensure -- from COLLECTION
    			wiped_out: is_empty
    		ensure then -- from DYNAMIC_LIST
    			is_before: before

    feature -- Conversion

    	linear_representation: LINEAR [EV_TREE_NODE]
    			-- Representation as a linear structure
    			-- (from LINEAR)
    		require -- from  CONTAINER
    			True

    feature -- Duplication

    	copy (other: like Current)
    			-- Update current object using fields of object attached
    			-- to `other', so as to yield equal objects.
    			-- (from EV_ANY)
    		require -- from ANY
    			other_not_void: other /= Void
    			type_identity: same_type (other)
    		ensure -- from ANY
    			is_equal: is_equal (other)

    	frozen deep_copy (other: like Current)
    			-- Effect equivalent to that of:
    			--		copy (`other' . deep_twin)
    			-- (from ANY)
    		require -- from ANY
    			other_not_void: other /= Void
    		ensure -- from ANY
    			deep_equal: deep_equal (Current, other)

    	frozen deep_twin: like Current
    			-- New object structure recursively duplicated from Current.
    			-- (from ANY)
    		ensure -- from ANY
    			deep_equal: deep_equal (Current, Result)

    	frozen standard_copy (other: like Current)
    			-- Copy every field of `other' onto corresponding field
    			-- of current object.
    			-- (from ANY)
    		require -- from ANY
    			other_not_void: other /= Void
    			type_identity: same_type (other)
    		ensure -- from ANY
    			is_standard_equal: standard_is_equal (other)

    	frozen standard_twin: like Current
    			-- New object field-by-field identical to `other'.
    			-- Always uses default copying semantics.
    			-- (from ANY)
    		ensure -- from ANY
    			standard_twin_not_void: Result /= Void
    			equal: standard_equal (Result, Current)

    	frozen twin: like Current
    			-- New object equal to `Current'
    			-- twin calls copy; to change copying/twining semantics, redefine copy.
    			-- (from ANY)
    		ensure -- from ANY
    			twin_not_void: Result /= Void
    			is_equal: Result.is_equal (Current)

    feature -- Basic operations

    	frozen default: like Current
    			-- Default value of object's type
    			-- (from ANY)

    	frozen default_pointer: POINTER
    			-- Default value of type `POINTER'
    			-- (Avoid the need to write `p'.default for
    			-- some `p' of type `POINTER'.)
    			-- (from ANY)

    	default_rescue
    			-- Process exception for routines with no Rescue clause.
    			-- (Default: do nothing.)
    			-- (from ANY)

    	frozen do_nothing
    			-- Execute a null action.
    			-- (from ANY)

    feature -- Implementation

    	changeable_comparison_criterion: BOOLEAN is False
    			-- May object_comparison be changed?
    			-- (Answer: no by default.
    			-- (from EV_ITEM_LIST)

    feature -- Basic operation

    	recursive_do_all (action: PROCEDURE [ANY, TUPLE [EV_TREE_NODE]])
    			-- Apply `action' to every item.
    			-- Semantics not guaranteed if `action' changes the structure;
    			-- (from EV_TREE_NODE_LIST)
    		require -- from EV_TREE_NODE_LIST
    			action_not_void: action /= Void

    feature -- Command

    	destroy
    			-- Destroy underlying native toolkit object.
    			-- Render `Current' unusable.
    			-- (from EV_ANY)
    		ensure -- from EV_ANY
    			is_destroyed: is_destroyed

    feature -- Contract support

    	is_expandable: BOOLEAN
    			-- Is `Current' able to expand or collapse.
    		require -- from EV_TREE_NODE
    			not_destroyed: not is_destroyed

    	is_parent_recursive (a_list: EV_TREE_NODE): BOOLEAN
    			-- Is `a_list' parent or recursively parent of parent?
    			-- (from EV_TREE_NODE)
    		require -- from EV_DYNAMIC_LIST
    			a_list_not_void: a_list /= Void
    			not_destroyed: not is_destroyed

    	same (other: EV_ANY): BOOLEAN
    			-- Is `other' `Current'?
    			-- (from EV_DYNAMIC_LIST)

    feature -- Event handling

    	collapse_actions: EV_NOTIFY_ACTION_SEQUENCE
    			-- Actions to be performed when collapsed.
    			-- (from EV_TREE_NODE_ACTION_SEQUENCES)
    		ensure -- from EV_TREE_NODE_ACTION_SEQUENCES
    			not_void: Result /= Void

    	conforming_pick_actions: EV_NOTIFY_ACTION_SEQUENCE
    			-- Actions to be performed when a pebble that fits here is picked.
    			-- (from EV_PICK_AND_DROPABLE_ACTION_SEQUENCES)
    		require -- from  EV_ABSTRACT_PICK_AND_DROPABLE
    			True
    		ensure -- from EV_PICK_AND_DROPABLE_ACTION_SEQUENCES
    			not_void: Result /= Void

    	deselect_actions: EV_NOTIFY_ACTION_SEQUENCE
    			-- Actions to be performed when deselected.
    			-- (from EV_TREE_NODE_ACTION_SEQUENCES)
    		ensure -- from EV_TREE_NODE_ACTION_SEQUENCES
    			not_void: Result /= Void

    	drop_actions: EV_PND_ACTION_SEQUENCE
    			-- Actions to be performed when a pebble is dropped here.
    			-- (from EV_PICK_AND_DROPABLE_ACTION_SEQUENCES)
    		require -- from  EV_ABSTRACT_PICK_AND_DROPABLE
    			True
    		ensure -- from EV_PICK_AND_DROPABLE_ACTION_SEQUENCES
    			not_void: Result /= Void

    	expand_actions: EV_NOTIFY_ACTION_SEQUENCE
    			-- Actions to be performed when expanded.
    			-- (from EV_TREE_NODE_ACTION_SEQUENCES)
    		ensure -- from EV_TREE_NODE_ACTION_SEQUENCES
    			not_void: Result /= Void

    	pick_actions: EV_PND_START_ACTION_SEQUENCE
    			-- Actions to be performed when pebble is picked up.
    			-- (from EV_PICK_AND_DROPABLE_ACTION_SEQUENCES)
    		require -- from  EV_ABSTRACT_PICK_AND_DROPABLE
    			True
    		ensure -- from EV_PICK_AND_DROPABLE_ACTION_SEQUENCES
    			not_void: Result /= Void

    	pick_ended_actions: EV_PND_FINISHED_ACTION_SEQUENCE
    			-- Actions to be performed when a transport from `Current' ends.
    			-- If transport completed successfully, then event data
    			-- is target. If cancelled, then event data is Void.
    			-- (from EV_PICK_AND_DROPABLE_ACTION_SEQUENCES)
    		ensure -- from EV_PICK_AND_DROPABLE_ACTION_SEQUENCES
    			not_void: Result /= Void

    	pointer_button_press_actions: EV_POINTER_BUTTON_ACTION_SEQUENCE
    			-- Actions to be performed when screen pointer button is pressed.
    			-- (from EV_ITEM_ACTION_SEQUENCES)
    		ensure -- from EV_ITEM_ACTION_SEQUENCES
    			not_void: Result /= Void

    	pointer_double_press_actions: EV_POINTER_BUTTON_ACTION_SEQUENCE
    			-- Actions to be performed when screen pointer is double clicked.
    			-- (from EV_ITEM_ACTION_SEQUENCES)
    		ensure -- from EV_ITEM_ACTION_SEQUENCES
    			not_void: Result /= Void

    	pointer_motion_actions: EV_POINTER_MOTION_ACTION_SEQUENCE
    			-- Actions to be performed when screen pointer moves.
    			-- (from EV_ITEM_ACTION_SEQUENCES)
    		require -- from  EV_ABSTRACT_PICK_AND_DROPABLE
    			True
    		ensure -- from EV_ITEM_ACTION_SEQUENCES
    			not_void: Result /= Void

    	select_actions: EV_NOTIFY_ACTION_SEQUENCE
    			-- Actions to be performed when selected.
    			-- (from EV_TREE_NODE_ACTION_SEQUENCES)
    		ensure -- from EV_TREE_NODE_ACTION_SEQUENCES
    			not_void: Result /= Void

    feature -- Iteration

    	do_all (action: PROCEDURE [ANY, TUPLE [EV_TREE_NODE]])
    			-- Apply `action' to every item.
    			-- Semantics not guaranteed if `action' changes the structure;
    			-- in such a case, apply iterator to clone of structure instead.
    			-- (from LINEAR)
    		require -- from TRAVERSABLE
    			action_exists: action /= Void

    	do_if (action: PROCEDURE [ANY, TUPLE [EV_TREE_NODE]]; test: FUNCTION [ANY, TUPLE [EV_TREE_NODE], BOOLEAN])
    			-- Apply `action' to every item that satisfies `test'.
    			-- Semantics not guaranteed if `action' or `test' changes the structure;
    			-- in such a case, apply iterator to clone of structure instead.
    			-- (from LINEAR)
    		require -- from TRAVERSABLE
    			action_exists: action /= Void
    			test_exits: test /= Void

    	for_all (test: FUNCTION [ANY, TUPLE [EV_TREE_NODE], BOOLEAN]): BOOLEAN
    			-- Is `test' true for all items?
    			-- Semantics not guaranteed if `test' changes the structure;
    			-- in such a case, apply iterator to clone of structure instead.
    			-- (from LINEAR)
    		require -- from TRAVERSABLE
    			test_exits: test /= Void
    		ensure then -- from LINEAR
    			empty: is_empty implies Result

    	there_exists (test: FUNCTION [ANY, TUPLE [EV_TREE_NODE], BOOLEAN]): BOOLEAN
    			-- Is `test' true for at least one item?
    			-- Semantics not guaranteed if `test' changes the structure;
    			-- in such a case, apply iterator to clone of structure instead.
    			-- (from LINEAR)
    		require -- from TRAVERSABLE
    			test_exits: test /= Void

    feature -- Output

    	io: STD_FILES
    			-- Handle to standard file setup
    			-- (from ANY)

    	out: STRING_8
    			-- New string containing terse printable representation
    			-- of current object
    			-- Was declared in ANY as synonym of tagged_out.
    			-- (from ANY)

    	print (some: ANY)
    			-- Write terse external representation of `some'
    			-- on standard output.
    			-- (from ANY)

    	frozen tagged_out: STRING_8
    			-- New string containing terse printable representation
    			-- of current object
    			-- Was declared in ANY as synonym of out.
    			-- (from ANY)

    feature -- Platform

    	operating_environment: OPERATING_ENVIRONMENT
    			-- Objects available from the operating system
    			-- (from ANY)

    feature -- Status Report

    	is_destroyed: BOOLEAN
    			-- Is `Current' no longer usable?
    			-- (from EV_ANY)
    		ensure -- from EV_ANY
    			bridge_ok: Result = implementation.is_destroyed

    invariant
    		-- from EV_PICK_AND_DROPABLE
    	user_interface_modes_mutually_exclusive: mode_is_pick_and_drop.to_integer + mode_is_drag_and_drop.to_integer + mode_is_target_menu.to_integer = 1

    		-- from EV_ANY
    	is_initialized: is_initialized
    	is_coupled: implementation /= Void and then implementation.interface = Current
    	default_create_called: default_create_called

    		-- from ANY
    	reflexive_equality: standard_is_equal (Current)
    	reflexive_conformance: conforms_to (Current)

    		-- from EV_ITEM_LIST
    	parent_of_items_is_current: is_usable and then not is_empty implies parent_of_items_is_current
    	items_unique: is_usable and not is_empty implies items_unique

    		-- from LIST
    	before_definition: before = (index = 0)
    	after_definition: after = (index = count + 1)

    		-- from CHAIN
    	non_negative_index: index >= 0
    	index_small_enough: index <= count + 1
    	off_definition: off = ((index = 0) or (index = count + 1))
    	isfirst_definition: isfirst = ((not is_empty) and (index = 1))
    	islast_definition: islast = ((not is_empty) and (index = count))
    	item_corresponds_to_index: (not off) implies (item = i_th (index))
    	index_set_has_same_count: index_set.count = count

    		-- from ACTIVE
    	writable_constraint: writable implies readable
    	empty_constraint: is_empty implies (not readable) and (not writable)

    		-- from INDEXABLE
    	index_set_not_void: index_set /= Void

    		-- from BILINEAR
    	not_both: not (after and before)
    	before_constraint: before implies off

    		-- from LINEAR
    	after_constraint: after implies off

    		-- from TRAVERSABLE
    	empty_constraint: is_empty implies off

    		-- from FINITE
    	empty_definition: is_empty = (count = 0)
    	non_negative_count: count >= 0

    		-- from DYNAMIC_CHAIN
    	extendible: extendible

    		-- from EV_TEXTABLE
    	text_not_void: is_usable implies text /= Void

    		-- from EV_DESELECTABLE
    	not_selectable_therefore_not_selected: not is_selectable implies not is_selected

    indexing
    	copyright: "Copyright (c) 1984-2006, Eiffel Software and others"
    	license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)"
    	source: "[
    		Eiffel Software
    		356 Storke Road, Goleta, CA 93117 USA
    		Telephone 805-685-1006, Fax 805-685-6869
    		Website http://www.eiffel.com
    		Customer support http://support.eiffel.com
    	]"

    end -- class EV_TREE_ITEM