    indexing
    	description: "Figure groups that are the root of a world of figures.%NMay be interpreted by any kind of projection.%NExamples: may be output to a printer, saved to an XML file,%Ndrawn on a drawing area, etc."
    	legal: "See notice at end of class."
    	status: "See notice at end of class."
    	date: "$Date: 2006-01-22 18:25:44 -0800 (Sun, 22 Jan 2006) $"
    	revision: "$Revision: 56675 $"

    class interface
    	EV_MODEL_WORLD

    create
    	default_create
    			-- Create with a white background.
    		require -- from  ANY
    			True
    		ensure then -- from EV_MODEL_GROUP
    			is_grouped: is_grouped
    			not_is_in_group: not is_in_group

    create {EV_MODEL_WORLD}
    	make_filled (n: INTEGER_32)
    			-- Allocate list with `n' items.
    			-- (`n' may be zero for empty list.)
    			-- This list will be full.
    			-- (from ARRAYED_LIST)
    		require -- from ARRAYED_LIST
    			valid_number_of_items: n >= 0
    		ensure -- from ARRAYED_LIST
    			correct_position: before
    			filled: full

    feature -- Initialization

    	list_make (n: INTEGER_32)
    			-- Allocate list with `n' items.
    			-- (`n' may be zero for empty list.)
    			-- (from ARRAYED_LIST)
    		require -- from ARRAYED_LIST
    			valid_number_of_items: n >= 0
    		ensure -- from ARRAYED_LIST
    			correct_position: before
    			is_empty: is_empty

    	make_filled (n: INTEGER_32)
    			-- Allocate list with `n' items.
    			-- (`n' may be zero for empty list.)
    			-- This list will be full.
    			-- (from ARRAYED_LIST)
    		require -- from ARRAYED_LIST
    			valid_number_of_items: n >= 0
    		ensure -- from ARRAYED_LIST
    			correct_position: before
    			filled: full

    feature -- Access

    	angle: REAL_64
    			-- `Current' has to be rotated around (x,y) for -angle
    			-- to be in upright position.
    			-- (from EV_MODEL_GROUP)
    		require -- from  EV_MODEL
    			True
    		ensure then -- from EV_MODEL_GROUP
    			result_equal_current_angle: Result = current_angle

    	background_color: EV_COLOR
    			-- Color used to clear drawing device.
    			-- Default: White.

    	capture_figure: EV_MODEL
    			-- Figure that has mouse capture.

    	cursor: ARRAYED_LIST_CURSOR
    			-- Current cursor position
    			-- (from ARRAYED_LIST)
    		ensure -- from CURSOR_STRUCTURE
    			cursor_not_void: Result /= Void

    	deep_elements: LIST [EV_MODEL]
    			-- All elements in `Current' and in its subgroups.
    			-- (from EV_MODEL_GROUP)
    		ensure -- from EV_MODEL_GROUP
    			result_not_void: Result /= Void

    	default_grid_x: INTEGER_32 is 20
    			-- Default horizontal step of grid.

    	default_grid_y: INTEGER_32 is 20
    			-- Default vertical step of grid.

    	first: like item
    			-- Item at first position
    			-- (from ARRAYED_LIST)
    		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)

    	grid_enabled: BOOLEAN
    			-- Should all move handles in world snap to grid?
    			-- Default: False.

    	grid_visible: BOOLEAN
    			-- Display visual representation of  grid?
    			-- Default: True.

    	grid_x: INTEGER_32
    			-- Horizontal step of grid.
    			-- Default: Default_grid_x.

    	grid_y: INTEGER_32
    			-- Vertical step of grid.
    			-- Default: Default_grid_x.

    	group: EV_MODEL_GROUP
    			-- The group `Current' is part of. Void if `Current' is
    			-- not part of a group.
    			-- (from EV_MODEL)

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

    	id: INTEGER_32
    			-- Unique id.
    			-- (from EV_MODEL)
    		ensure -- from HASHABLE
    			good_hash_value: Result >= 0

    	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
    			-- Index of item, if valid.
    			-- (from ARRAYED_LIST)

    	index_of (v: like item; i: INTEGER_32): INTEGER_32
    			-- Index of `i'-th occurrence of item identical to `v'.
    			-- (Reference or object equality,
    			-- based on object_comparison.)
    			-- 0 if none.
    			-- (from CHAIN)
    		require -- from LINEAR
    			positive_occurrences: i > 0
    		ensure -- from LINEAR
    			non_negative_result: Result >= 0

    	item: EV_MODEL
    			-- Current item
    			-- (from ARRAYED_LIST)
    		require -- from TRAVERSABLE
    			not_off: not off
    		require -- from ACTIVE
    			readable: readable
    		require else -- from ARRAYED_LIST
    			index_is_valid: valid_index (index)

    	last: like first
    			-- Item at last position
    			-- (from ARRAYED_LIST)
    		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

    	pebble: ANY
    			-- Data to be transported by pick and drop mechanism.
    			-- (from EV_MODEL)

    	pebble_function: FUNCTION [ANY, TUPLE, ANY]
    			-- Returns data to be transported by pick and drop mechanism.
    			-- When not `Void', pebble is ignored.
    			-- (from EV_MODEL)

    	point: EV_COORDINATE
    			-- First point of `Current'.
    			-- (from EV_MODEL_SINGLE_POINTED)
    		ensure -- from EV_MODEL_SINGLE_POINTED
    			result_exists: Result /= Void
    			result_x_equal_point_x: Result.x = point_x
    			result_y_eqyal_point_y: Result.y = point_y

    	point_count: INTEGER_32
    			-- `Current' has one point.
    			-- (from EV_MODEL_SINGLE_POINTED)
    		require -- from  EV_MODEL
    			True
    		ensure -- from EV_MODEL
    			correct: Result = point_array.count

    	point_relative: EV_COORDINATE
    			-- point relative to group.point.
    			-- (from EV_MODEL_SINGLE_POINTED)
    		ensure -- from EV_MODEL_SINGLE_POINTED
    			result_exists: Result /= Void
    			result_x_equal_point_x_relative: Result.x = point_x_relative
    			result_y_eqyal_point_y_relative: Result.y = point_y_relative

    	point_x: INTEGER_32
    			-- x position of point.
    			-- (from EV_MODEL_GROUP)

    	point_x_relative: INTEGER_32
    			-- horizontal distance between point_x and group.point_x.
    			-- (from EV_MODEL_SINGLE_POINTED)

    	point_y: INTEGER_32
    			-- y position of point.
    			-- (from EV_MODEL_GROUP)

    	point_y_relative: INTEGER_32
    			-- vertical distance between point_y and group.point_y.
    			-- (from EV_MODEL_SINGLE_POINTED)

    	pointer_style: EV_POINTER_STYLE
    			-- Cursor displayed when pointer is over this figure.
    			-- (from EV_MODEL)

    	points_visible: BOOLEAN
    			-- Are all points in world visible?
    			-- Used for debugging purposes.
    			-- Default: False.

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

    	world: EV_MODEL_WORLD
    			-- `Current' object.

    	x: INTEGER_32
    			-- x position of the center on the screen.
    			-- (from EV_MODEL)

    	x_to_grid (a_x: INTEGER_32): INTEGER_32
    			-- Nearest point on grid to `a_x'.

    	y: INTEGER_32
    			-- y position of the center on the screen .
    			-- (from EV_MODEL)

    	y_to_grid (a_y: INTEGER_32): INTEGER_32
    			-- Nearest point on grid to absolute `a_y'.

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

    feature -- Measurement

    	count: INTEGER_32
    			-- Number of items.
    			-- (from ARRAYED_LIST)

    	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 {ANY} -- Measurement

    	capacity: INTEGER_32
    			-- Number of available indices
    			-- Was declared in ARRAY as synonym of count.
    			-- (from ARRAY)
    		require -- from  BOUNDED
    			True
    		ensure then -- from ARRAY
    			consistent_with_bounds: Result = upper - lower + 1

    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
    			-- Is `other' attached to an object considered
    			-- equal to current object?
    			-- (from ANY)
    		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

    	changeable_comparison_criterion: BOOLEAN
    			-- May object_comparison be changed?
    			-- (Answer: yes by default.)
    			-- (from CONTAINER)

    	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 structure filled to capacity?
    			-- (from ARRAYED_LIST)
    		require -- from  BOX
    			True

    	has (v: like item): BOOLEAN
    			-- Does current include `v'?
    			-- (based on v.id)
    			-- (from EV_MODEL_GROUP)
    		require -- from  CONTAINER
    			True
    		ensure -- from CONTAINER
    			not_found_in_empty: Result implies not is_empty

    	has_deep (figure: EV_MODEL): BOOLEAN
    			-- Does any item contains `figure'?
    			-- (from EV_MODEL_GROUP)

    	invalid_rectangle: EV_RECTANGLE
    			-- Rectangle that needs erasing.
    			-- `Void' if no change is made.
    			-- (from EV_MODEL_GROUP)

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

    	is_grouped: BOOLEAN
    			-- Is grouped?
    			-- (from EV_MODEL_GROUP)

    	is_hashable: BOOLEAN
    			-- May current object be hashed?
    			-- (True if it is not its type's default.)
    			-- (from HASHABLE)
    		ensure -- from HASHABLE
    			ok_if_not_default: Result implies (Current /= default)

    	is_inserted (v: EV_MODEL): BOOLEAN
    			-- Has `v' been inserted at the end by the most recent put or
    			-- extend?
    			-- (from ARRAYED_LIST)

    	is_redraw_needed: BOOLEAN
    			-- Does entire area need to be redrawn?
    			-- This is the case when a figure is added or removed.

    	is_rotatable: BOOLEAN
    			-- Is this figure group rotatable?
    			-- (from EV_MODEL_GROUP)

    	is_scalable: BOOLEAN
    			-- Is this figure group scalable?
    			-- (from EV_MODEL_GROUP)

    	is_transformable: BOOLEAN
    			-- Is this figure group transformable?
    			-- (from EV_MODEL_GROUP)

    	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

    	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 ARRAYED_LIST)
    		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))

    	update_rectangle: EV_RECTANGLE
    			-- Rectangle that needs redrawing.
    			-- `Void' if no change is made.
    			-- (from EV_MODEL_GROUP)

    	valid_cursor (p: CURSOR): BOOLEAN
    			-- Can the cursor be moved to position `p'?
    			-- (from ARRAYED_LIST)

    	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' a valid index?
    			-- (from ARRAYED_LIST)
    		require -- from  TABLE
    			True
    		require -- from  TO_SPECIAL
    			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

    	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_grid
    			-- Set grid_enabled `False'.
    		ensure
    			grid_disabled: not grid_enabled

    	enable_grid
    			-- Set grid_enabled `True'.
    		ensure
    			grid_enabled: grid_enabled

    	full_redraw
    			-- On next projection, mark entire area as invalid.

    	hide_grid
    			-- Set grid_visible to `False'.
    		ensure
    			not_grid_visible: not grid_visible

    	hide_points
    			-- Set points_visible to `False'.
    		ensure
    			not_points_visible: not points_visible

    	set_point_position_relative (ax, ay: INTEGER_32)
    			-- Set position of point_relative to (`ax', `ay').
    			-- (from EV_MODEL_SINGLE_POINTED)

    	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)

    	show_grid
    			-- Set grid_visible to `True'.
    		ensure
    			grid_visible: grid_visible

    	show_points
    			-- Set points_visible to `True'.
    		ensure
    			points_visible: points_visible

    feature -- Cursor movement

    	back
    			-- Move cursor one position backward.
    			-- (from ARRAYED_LIST)
    		require -- from BILINEAR
    			not_before: not before

    	finish
    			-- Move cursor to last position if any.
    			-- (from ARRAYED_LIST)
    		require -- from  LINEAR
    			True
    		ensure then -- from CHAIN
    			at_last: not is_empty implies islast
    		ensure then -- from ARRAYED_LIST
    			before_when_empty: is_empty implies before

    	forth
    			-- Move cursor one position forward.
    			-- (from ARRAYED_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 ARRAYED_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 ARRAYED_LIST)
    		require -- from CURSOR_STRUCTURE
    			cursor_position_valid: valid_cursor (p)

    	move (i: INTEGER_32)
    			-- Move cursor `i' positions.
    			-- (from ARRAYED_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 ARRAYED_LIST)
    		require -- from  LINEAR
    			True
    		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 if any.
    			-- (from ARRAYED_LIST)
    		require -- from  TRAVERSABLE
    			True
    		ensure then -- from CHAIN
    			at_first: not is_empty implies isfirst
    		ensure then -- from ARRAYED_LIST
    			after_when_empty: is_empty implies after

    feature -- Element change

    	bring_forward (a_figure: EV_MODEL)
    			-- Bring `a_figure' one layer forwards.
    			-- (from EV_MODEL_GROUP)
    		require -- from EV_MODEL_GROUP
    			a_figure_in_figures: has (a_figure)
    		ensure -- from EV_MODEL_GROUP
    			a_figure_in_group: a_figure.group = Current
    			a_figure_in_current: has (a_figure)

    	bring_to_front (a_figure: EV_MODEL)
    			-- Bring `a_figure' to the top most layer
    			-- (from EV_MODEL_GROUP)
    		require -- from EV_MODEL_GROUP
    			a_figure_in_figures: has (a_figure)
    		ensure -- from EV_MODEL_GROUP
    			is_last: last = a_figure
    			a_figure_in_group: a_figure.group = Current
    			a_figure_in_current: has (a_figure)

    	extend (v: like item)
    			-- Add `v' to end.
    			-- Do not move cursor.
    			-- Was declared in ARRAYED_LIST as synonym of force.
    			-- (from ARRAYED_LIST)
    		require -- from COLLECTION
    			extendible: extendible
    		ensure -- from COLLECTION
    			item_inserted: is_inserted (v)
    		ensure then -- from BAG
    			one_more_occurrence: occurrences (v) = old (occurrences (v)) + 1

    	fill (other: CONTAINER [EV_MODEL])
    			-- 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 ARRAYED_LIST as synonym of extend.
    			-- (from ARRAYED_LIST)
    		require -- from SEQUENCE
    			extendible: extendible
    		ensure then -- from SEQUENCE
    			new_count: count = old count + 1
    			item_inserted: has (v)

    	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 CHAIN
    			same_count: count = old count

    	put_front (v: like item)
    			-- Add `v' to the beginning.
    			-- Do not move cursor.
    			-- (from ARRAYED_LIST)
    		ensure -- from DYNAMIC_CHAIN
    			new_count: count = old count + 1
    			item_inserted: first = v

    	put_left (v: like item)
    			-- Add `v' to the left of current position.
    			-- Do not move cursor.
    			-- (from ARRAYED_LIST)
    		require -- from DYNAMIC_CHAIN
    			extendible: extendible
    			not_before: not before
    		ensure -- from DYNAMIC_CHAIN
    			new_count: count = old count + 1
    			new_index: index = old index + 1

    	put_right (v: like item)
    			-- Add `v' to the right of current position.
    			-- Do not move cursor.
    			-- (from ARRAYED_LIST)
    		require -- from DYNAMIC_CHAIN
    			extendible: extendible
    			not_after: not after
    		ensure -- from DYNAMIC_CHAIN
    			new_count: count = old count + 1
    			same_index: index = old index

    	regroup
    			-- Group the `figures' in the group.
    			-- (from EV_MODEL_GROUP)
    		require -- from EV_MODEL_GROUP
    			not_is_grouped: not is_grouped
    			not_is_in_group: not is_in_group
    		ensure -- from EV_MODEL_GROUP
    			is_grouped: is_grouped
    			all_grouped: for_all (agent {EV_MODEL}.is_in_group)
    			center_is_invalid: not is_center_valid

    	remove_capture_figure
    			-- Set capture_figure to `Void'.
    		require
    			capture_figure_not_void: capture_figure /= Void
    		ensure
    			removed: capture_figure = Void

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

    	rotate (an_angle: REAL_64)
    			-- Rotate around the center for `an_angle'.
    			-- (from EV_MODEL_GROUP)
    		require -- from EV_MODEL
    			is_rotatable: is_rotatable
    		ensure -- from EV_MODEL
    			center_valid: is_center_valid
    		ensure then -- from EV_MODEL_GROUP
    			angle_equal_an_angle: angle = old angle + an_angle

    	rotate_around (an_angle: REAL_64; ax, ay: INTEGER_32)
    			-- Rotate around (`ax', `ay') for `an_angle'.
    			-- (from EV_MODEL)
    		require -- from EV_MODEL
    			is_rotatable: is_rotatable
    		ensure -- from EV_MODEL
    			center_valid: is_center_valid

    	scale (a_scale: REAL_64)
    			-- Scale to x and y direction for `a_scale'.
    			-- (from EV_MODEL)
    		require -- from EV_MODEL
    			is_scalable: is_scalable
    			a_scale_bigger_zero: a_scale > 0.0

    	scale_abs (a_scale: REAL_64)
    			-- Scale to x and y direction for `a_scale'.
    			-- Do not rotate around angle first.
    			-- (from EV_MODEL)
    		require -- from EV_MODEL
    			is_scalable: is_scalable
    			a_scale_bigger_zero: a_scale > 0.0

    	scale_x (a_scale_x: REAL_64)
    			-- Scale to x direction for `a_scale_x'.
    			-- (from EV_MODEL)
    		require -- from EV_MODEL
    			is_scalable: is_scalable
    			a_scale_x_bigger_zero: a_scale_x > 0.0

    	scale_x_abs (a_scale_x: REAL_64)
    			-- Scale absolute to x direction for `a_scale_x'.
    			-- Do not rotate around angle first.
    			-- (from EV_MODEL)
    		require -- from EV_MODEL
    			is_scalable: is_scalable
    			a_scale_x_bigger_zero: a_scale_x > 0.0

    	scale_y (a_scale_y: REAL_64)
    			-- Scale to y direction for `a_scale_y'.
    			-- (from EV_MODEL)
    		require -- from EV_MODEL
    			is_scalable: is_scalable
    			a_scale_y_bigger_zero: a_scale_y > 0.0

    	scale_y_abs (a_scale_y: REAL_64)
    			-- Scale to y direction for `a_scale_y'.
    			-- Do not rotate around angle first.
    			-- (from EV_MODEL)
    		require -- from EV_MODEL
    			is_scalable: is_scalable
    			a_scale_y_bigger_zero: a_scale_y > 0.0

    	send_backward (a_figure: EV_MODEL)
    			-- Send `a_figure' one layer backwards.
    			-- (from EV_MODEL_GROUP)
    		require -- from EV_MODEL_GROUP
    			a_figure_in_figures: has (a_figure)
    		ensure -- from EV_MODEL_GROUP
    			a_figure_in_group: a_figure.group = Current
    			a_figure_in_current: has (a_figure)

    	send_to_back (a_figure: EV_MODEL)
    			-- Send `a_figure' to the bottom most layer.
    			-- (from EV_MODEL_GROUP)
    		require -- from EV_MODEL_GROUP
    			a_figure_in_figures: has (a_figure)
    		ensure -- from EV_MODEL_GROUP
    			is_at_front: first = a_figure
    			a_figure_in_group: a_figure.group = Current
    			a_figure_in_current: has (a_figure)

    	set_accept_cursor (a_cursor: EV_POINTER_STYLE)
    			-- Set `a_cursor' to be displayed when the screen pointer is over a
    			-- target that accepts pebble during pick and drop.
    			-- (from EV_MODEL)
    		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_background_color (a_color: EV_COLOR)
    			-- Assign `a_color' to background_color.
    		require
    			a_color_not_void: a_color /= Void
    		ensure
    			assigned: background_color = a_color

    	set_capture_figure (a_figure: EV_MODEL)
    			-- Set capture_figure to `a_figure'.
    		require
    			a_figure_not_void: a_figure /= Void
    		ensure
    			assigned: capture_figure = a_figure

    	set_deny_cursor (a_cursor: EV_POINTER_STYLE)
    			-- Set `a_cursor' to be displayed when the screen pointer is not
    			-- over a valid target.
    			-- (from EV_MODEL)
    		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_grid_x (new_grid_x: INTEGER_32)
    			-- Assign `new_grid_x' to grid_x.
    		require
    			new_grid_x_positive: new_grid_x > 0
    		ensure
    			assigned: grid_x = new_grid_x

    	set_grid_y (new_grid_y: INTEGER_32)
    			-- Assign `new_grid_y' to grid_y.
    		require
    			new_grid_y_positive: new_grid_y > 0
    		ensure
    			assigned: grid_y = new_grid_y

    	set_pebble (a_pebble: like pebble)
    			-- Assign `a_pebble' to pebble.
    			-- (from EV_MODEL)
    		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.
    			-- (from EV_MODEL)
    		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_point_position (a_x, a_y: INTEGER_32)
    			-- Set position of point to (`a_x', `a_y').
    			-- (from EV_MODEL_GROUP)

    	set_pointer_style (a_cursor: like pointer_style)
    			-- Assign `a_cursor' to pointer_style.
    			-- (from EV_MODEL)
    		require -- from EV_MODEL
    			a_cursor_not_void: a_cursor /= Void
    		ensure -- from EV_MODEL
    			pointer_style_assigned: pointer_style = a_cursor

    	set_x (a_x: INTEGER_32)
    			-- Set x to `an_x'.
    			-- (from EV_MODEL_GROUP)
    		ensure -- from EV_MODEL
    			x_set: a_x = x
    			center_valid: is_center_valid

    	set_x_y (a_x, a_y: INTEGER_32)
    			-- Set x to `an_x'.
    			-- (from EV_MODEL_GROUP)
    		ensure -- from EV_MODEL
    			set: a_x = x and a_y = y
    			center_valid: is_center_valid

    	set_y (a_y: INTEGER_32)
    			-- Set y to `an_y'.
    			-- (from EV_MODEL_GROUP)
    		ensure -- from EV_MODEL
    			y_set: a_y = y
    			center_valid: is_center_valid

    	transform (a_transformation: EV_MODEL_TRANSFORMATION)
    			-- Transform all points in point_array using `a_transformation'.
    			-- You can do any transformation you want. You can
    			-- for example rotate `Current' around an other point
    			-- than the center.
    			-- (from EV_MODEL)
    		require -- from EV_MODEL
    			a_transformation_not_void: a_transformation /= Void
    			is_transformable: is_transformable

    	ungroup
    			-- Ungroup all `figures'.
    			-- (from EV_MODEL_GROUP)
    		require -- from EV_MODEL_GROUP
    			is_grouped: is_grouped
    			not_is_in_group: not is_in_group
    		ensure -- from EV_MODEL_GROUP
    			is_ungrouped: not is_grouped
    			none_is_in_a_group: not there_exists (agent {EV_MODEL}.is_in_group)
    			center_is_invalid: not is_center_valid

    feature -- Removal

    	prune (v: like item)
    			-- Remove first occurrence of `v', if any,
    			-- after cursor position.
    			-- Move cursor to right neighbor.
    			-- (or after if no right neighbor or `v' does not occur)
    			-- (from ARRAYED_LIST)
    		require -- from COLLECTION
    			prunable: prunable

    	remove_left
    			-- Remove item to the left of cursor position.
    			-- Do not move cursor.
    			-- (from ARRAYED_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

    	remove_right
    			-- Remove item to the right of cursor position
    			-- Do not move cursor
    			-- (from ARRAYED_LIST)
    		require -- from DYNAMIC_CHAIN
    			right_exists: index < count
    		ensure -- from DYNAMIC_CHAIN
    			new_count: count = old count - 1
    			same_index: index = old index

    feature -- Resizing

    	resize (new_capacity: INTEGER_32)
    			-- Resize list so that it can contain
    			-- at least `n' items. Do not lose any item.
    			-- (from ARRAYED_LIST)
    		require -- from ARRAYED_LIST
    			new_capacity_large_enough: new_capacity >= capacity
    		ensure -- from ARRAYED_LIST
    			capacity_set: capacity >= new_capacity

    feature -- Conversion

    	linear_representation: LINEAR [EV_MODEL]
    			-- 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 ANY)
    		require -- from ANY
    			other_not_void: other /= Void
    			type_identity: same_type (other)
    		ensure -- from ANY
    			is_equal: is_equal (other)
    		ensure then -- from ARRAY
    			equal_areas: area.is_equal (other.area)

    	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)

    	duplicate (n: INTEGER_32): like Current
    			-- Copy of sub-list beginning at current position
    			-- and having min (`n', count - index + 1) items.
    			-- (from ARRAYED_LIST)
    		require -- from CHAIN
    			not_off_unless_after: off implies after
    			valid_subchain: n >= 0

    	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 -- Action sequences

    	conforming_pick_actions: EV_NOTIFY_ACTION_SEQUENCE
    			-- Actions to be performed when a pebble that fits this hole is
    			-- picked up from another source.
    			-- (when drop_actions.accepts_pebble (pebble))
    			-- (from EV_MODEL)

    	drop_actions: EV_PND_ACTION_SEQUENCE
    			-- Actions to take when pick and drop transport drops on `Current'.
    			-- (from EV_MODEL)

    	pick_actions: EV_PND_START_ACTION_SEQUENCE
    			-- Actions to be performed when pebble is picked up.
    			-- (from EV_MODEL)

    	pointer_button_press_actions: EV_POINTER_BUTTON_ACTION_SEQUENCE
    			-- Actions to be performed when screen pointer button is pressed.
    			-- (from EV_MODEL)

    	pointer_button_release_actions: EV_POINTER_BUTTON_ACTION_SEQUENCE
    			-- Actions to be performed when screen pointer button is released.
    			-- (from EV_MODEL)

    	pointer_double_press_actions: EV_POINTER_BUTTON_ACTION_SEQUENCE
    			-- Actions to be performed when screen pointer is double clicked.
    			-- (from EV_MODEL)

    	pointer_enter_actions: EV_NOTIFY_ACTION_SEQUENCE
    			-- Actions to be performed when screen pointer enters widget.
    			-- (from EV_MODEL)

    	pointer_leave_actions: EV_NOTIFY_ACTION_SEQUENCE
    			-- Actions to be performed when screen pointer leaves widget.
    			-- (from EV_MODEL)

    	pointer_motion_actions: EV_POINTER_MOTION_ACTION_SEQUENCE
    			-- Actions to be performed when screen pointer moves.
    			-- (from EV_MODEL)

    feature -- Events

    	bounding_box: EV_RECTANGLE
    			-- Smallest orthogonal rectangular area `Current' fits in.
    			-- (from EV_MODEL_GROUP)
    		ensure -- from EV_MODEL
    			result_not_void: Result /= Void
    			internal_is_twin: internal_bounding_box /= Result

    	position_on_figure (a_x, a_y: INTEGER_32): BOOLEAN
    			-- Is the point on (`a_x', `a_y') on this figure?
    			-- Always returns `False', but descendants can override
    			-- it to improve efficiency.
    			-- (from EV_MODEL_GROUP)

    feature -- Iteration

    	do_all (action: PROCEDURE [ANY, TUPLE [EV_MODEL]])
    			-- 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
    		require -- from ARRAY
    			action_not_void: action /= Void

    	do_if (action: PROCEDURE [ANY, TUPLE [EV_MODEL]]; test: FUNCTION [ANY, TUPLE [EV_MODEL], 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
    		require -- from ARRAY
    			action_not_void: action /= Void
    			test_not_void: test /= Void

    	for_all (test: FUNCTION [ANY, TUPLE [EV_MODEL], 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
    		require -- from ARRAY
    			test_not_void: test /= Void
    		ensure then -- from LINEAR
    			empty: is_empty implies Result

    	there_exists (test: FUNCTION [ANY, TUPLE [EV_MODEL], 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
    		require -- from ARRAY
    			test_not_void: test /= Void

    feature -- List change

    	append (s: SEQUENCE [EV_MODEL])
    			-- Append a copy of `s'.
    			-- (from EV_MODEL_GROUP)
    		require -- from SEQUENCE
    			argument_not_void: s /= Void
    		ensure -- from SEQUENCE
    			new_count: count >= old count

    	force_i_th (fig: like item; i: INTEGER_32)
    			-- Add `fig' to the group.
    			-- (from EV_MODEL_GROUP)
    		require -- from  ARRAY
    			True
    		ensure -- from ARRAY
    			inserted: i_th (i) = fig
    			higher_count: count >= old count
    		ensure then -- from EV_MODEL_GROUP
    			fig_in_lookup_table: fig /= Void implies lookup_table.has (fig.id)
    			fig_in_group: fig /= Void implies fig.group = Current

    	insert (fig: like item; i: INTEGER_32)
    			-- Add `fig' to the group.
    			-- (from EV_MODEL_GROUP)
    		require -- from ARRAYED_LIST
    			index_small_enough: i <= count
    			index_large_enough: i >= 1
    		ensure -- from ARRAYED_LIST
    			new_count: count = old count + 1
    			index_unchanged: index = old index
    			insertion_done: i_th (i) = fig
    		ensure then -- from EV_MODEL_GROUP
    			fig_in_lookup_table: fig /= Void implies lookup_table.has (fig.id)
    			fig_in_group: fig /= Void implies fig.group = Current

    	make_from_array (a: ARRAY [EV_MODEL])
    			-- Create list from array `a'.
    			-- (from EV_MODEL_GROUP)
    		require -- from ARRAY
    			array_exists: a /= Void
    		ensure then -- from ARRAYED_LIST
    			correct_position: before
    			filled: count = a.count

    	merge_left (other: like Current)
    			-- Merge `other' into group before cursor.
    			-- `other' will be empty afterwards.
    			-- (from EV_MODEL_GROUP)
    		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 group after cursor.
    			-- `other' will be empty afterwards.
    			-- (from EV_MODEL_GROUP)
    		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

    	prune_all (fig: like item)
    			-- Remove `fig' from the group.
    			-- (from EV_MODEL_GROUP)
    		require -- from COLLECTION
    			prunable: prunable
    		ensure -- from COLLECTION
    			no_more_occurrences: not has (fig)
    		ensure then -- from DYNAMIC_CHAIN
    			is_exhausted: exhausted
    		ensure then -- from ARRAYED_LIST
    			is_after: after
    		ensure then -- from EV_MODEL_GROUP
    			item_not_in_lookup_table: fig /= Void implies not lookup_table.has (fig.id)

    	remove
    			-- Remove item from figure.
    			-- (from EV_MODEL_GROUP)
    		require -- from ACTIVE
    			prunable: prunable
    			writable: writable
    		ensure then -- from DYNAMIC_LIST
    			after_when_empty: is_empty implies after
    		ensure then -- from ARRAYED_LIST
    			index: index = old index
    		ensure then -- from EV_MODEL_GROUP
    			item_not_in_lookup_table: not lookup_table.has (old item.id)
    			item_not_in_group: not (old item).is_in_group

    	replace (fig: like item)
    			-- Replace current item by `fig'.
    			-- (from EV_MODEL_GROUP)
    		require -- from ACTIVE
    			writable: writable
    		ensure -- from ACTIVE
    			item_replaced: item = fig
    		ensure then -- from EV_MODEL_GROUP
    			fig_in_lookup_table: fig /= Void implies lookup_table.has (fig.id)
    			item_not_in_lookup_table: not lookup_table.has (old item.id)
    			fig_in_group: fig /= Void implies fig.group = Current
    			item_not_in_group: not (old item).is_in_group

    	swap (i: INTEGER_32)
    			-- Exchange item at `i'-th position with item
    			-- at cursor position.
    			-- (from EV_MODEL_GROUP)
    		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
    		ensure then -- from EV_MODEL_GROUP
    			item_in_lookup_table: lookup_table.has (old item.id)
    			i_in_lookup_table: lookup_table.has (i_th (i).id)
    			item_in_group: (old item).group = Current
    			i_th_in_group: i_th (i).group = Current

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

    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

    	accept_cursor: EV_POINTER_STYLE
    			-- Accept cursor set by user.
    			-- To be displayed when the screen pointer is over a target that accepts
    			-- pebble during pick and drop.
    			-- (from EV_MODEL)

    	are_events_sended_to_group: BOOLEAN
    			-- Are events for pointer_motion_actions, pointer_button_press_actions,
    			-- pointer_double_press_actions,  pointer_button_release_actions
    			-- pointer_enter_actions and pointer_leave_actions send to `Current's
    			-- group (if any) even if `Current' catch the event. (Default True).
    			-- (from EV_MODEL)

    	deny_cursor: EV_POINTER_STYLE
    			-- Deny cursor set by user.
    			-- To be displayed when the screen pointer is not over a valid target.
    			-- (from EV_MODEL)

    	has_capture: BOOLEAN
    			-- Are all events sent to `Current'?
    			-- (from EV_MODEL)

    	is_center_valid: BOOLEAN
    			-- Is the position of the center valid?
    			-- (from EV_MODEL)

    	is_in_group: BOOLEAN
    			-- Is `Current' part of a group?
    			-- (from EV_MODEL)
    		ensure -- from EV_MODEL
    			group_defines_is_in_group: Result = (group /= Void)

    	is_in_world: BOOLEAN
    			-- Is `Current' part of a world?
    			-- (from EV_MODEL)
    		ensure -- from EV_MODEL
    			world_defines_is_in_world: Result = (world /= Void)

    	is_sensitive: BOOLEAN
    			-- Is object sensitive to user input?
    			-- (from EV_MODEL)

    	is_show_requested: BOOLEAN
    			-- Will `Current' be displayed when its parent is?
    			-- (from EV_MODEL)

    feature -- Status settings

    	disable_capture
    			-- Disable grab of all events on world.
    			-- (from EV_MODEL)
    		require -- from EV_MODEL
    			in_world: world /= Void
    			has_capture: has_capture
    		ensure -- from EV_MODEL
    			capture_released: not has_capture

    	disable_events_sended_to_group
    			-- Set are_events_sended_to_group to False.
    			-- (from EV_MODEL)
    		ensure -- from EV_MODEL
    			events_blocked: not are_events_sended_to_group

    	disable_sensitive
    			-- Make object non-sensitive to user input.
    			-- (from EV_MODEL)
    		ensure -- from EV_MODEL
    			insensitive_requested: not internal_is_sensitive

    	enable_capture
    			-- Grab all mouse events for world.
    			-- (from EV_MODEL)
    		require -- from EV_MODEL
    			in_world: world /= Void
    		ensure -- from EV_MODEL
    			capture_set: has_capture

    	enable_events_sended_to_group
    			-- Set are_events_sended_to_group to True.
    			-- (from EV_MODEL)
    		ensure -- from EV_MODEL
    			events_sended_to_group: are_events_sended_to_group

    	enable_sensitive
    			-- Make object sensitive to user input.
    			-- (from EV_MODEL)
    		ensure -- from EV_MODEL
    			sensitive_requested: internal_is_sensitive

    	hide
    			-- Request that `Current' not be displayed even when its group is.
    			-- (from EV_MODEL)
    		ensure -- from EV_MODEL
    			not_is_show_requested: not is_show_requested

    	invalidate
    			-- Some property of `Current' has changed.
    			-- (from EV_MODEL_GROUP)

    	show
    			-- Request that `Current' be displayed when its group is.
    			-- `True' by default.
    			-- (from EV_MODEL)
    		ensure -- from EV_MODEL
    			is_show_requested: is_show_requested

    	validate
    			-- Validate `Current'.
    			-- (from EV_MODEL_GROUP)

    feature --EV_FIGURE -- Status settings

    	center_invalidate
    			-- The position of the center may have changed.
    			-- (from EV_MODEL)

    invariant
    	background_color_exists: background_color /= Void

    		-- from EV_MODEL_GROUP
    	is_grouped_implies_all_grouped: is_grouped implies for_all (agent {EV_MODEL}.is_in_group)
    	angle_equal_current_angle: angle = current_angle
    	not_is_grouped_implies_angel_equals_zero: not is_grouped implies (angle = 0)

    		-- from EV_MODEL
    	point_array_exists: point_array /= Void
    	center_exists: center /= Void
    	x_is_center_x: x = center.x
    	y_is_center_y: y = center.y
    	all_points_exist: all_points_exist (point_array)
    	projection_matrix_not_void: projection_matrix /= Void
    	is_transfomable_implies_rotatable_and_scalable: is_transformable implies (is_rotatable and is_scalable)

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

    		-- from ARRAYED_LIST
    	prunable: prunable
    	starts_from_one: lower = 1
    	empty_means_storage_empty: is_empty implies all_default

    		-- from ARRAY
    	area_exists: area /= Void
    	consistent_size: capacity = upper - lower + 1
    	non_negative_count: count >= 0
    	index_set_has_same_count: valid_index_set

    		-- from RESIZABLE
    	increase_by_at_least_one: minimal_increase >= 1

    		-- from BOUNDED
    	valid_count: count <= capacity
    	full_definition: full = (count = capacity)

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

    		-- from INDEXABLE
    	index_set_not_void: index_set /= Void

    		-- 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 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 DYNAMIC_CHAIN
    	extendible: extendible

    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_MODEL_WORLD