    indexing
    	description: "[
    		Widget which is a combination of an EV_TREE and an EV_MULTI_COLUMN_LIST.
    		Implementation Interface.
    	]"
    	legal: "See notice at end of class."
    	status: "See notice at end of class."
    	date: "$Date: 2006-10-05 11:59:42 -0700 (Thu, 05 Oct 2006) $"
    	revision: "$Revision: 64186 $"

    deferred class interface
    	EV_GRID_I

    feature -- Access

    	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_PICK_AND_DROPABLE_I)

    	actual_drop_target_agent: FUNCTION [ANY, TUPLE [INTEGER_32, INTEGER_32], EV_ABSTRACT_PICK_AND_DROPABLE]
    			-- Overrides default drop target on a certain position.
    			-- If `Void', will use the default drop target.
    			-- Always void if `Current' is not a widget.
    			-- (from EV_WIDGET_I)

    	are_tree_node_connectors_shown: BOOLEAN
    			-- Are connectors between tree nodes shown in `Current'?

    	background_color: EV_COLOR
    			-- Color displayed behind foregournd features.
    			-- (from EV_COLORIZABLE_I)

    	client_height: INTEGER_32
    			-- Height of the client area of container.
    			-- (from EV_CONTAINER_I)
    		ensure -- from EV_CONTAINER_I
    			positive: Result >= 0

    	client_width: INTEGER_32
    			-- Width of the client area of container.
    			-- (from EV_CONTAINER_I)
    		ensure -- from EV_CONTAINER_I
    			positive: Result >= 0

    	column (a_column: INTEGER_32): EV_GRID_COLUMN
    			-- Column at index `a_column'.
    		require
    			a_column_positive: a_column > 0
    			a_column_not_greater_than_column_count: a_column <= column_count
    		ensure
    			column_not_void: Result /= Void

    	column_at_virtual_position (a_virtual_x: INTEGER_32): EV_GRID_COLUMN
    			-- Column at virtual x position `a_virtual_x'.
    		require
    			virtual_x_valid: a_virtual_x >= 0 and a_virtual_x <= virtual_width

    	conforming_pick_actions: EV_NOTIFY_ACTION_SEQUENCE
    			-- Actions to be performed when a pebble that fits here is picked.
    		ensure -- from EV_PICK_AND_DROPABLE_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	default_key_processing_handler: PREDICATE [ANY, TUPLE [EV_KEY]]
    			-- Agent used to determine whether the default key processing should occur for `Current'.
    			-- If agent returns `True' then default key processing continues as normal, False prevents
    			-- default key processing from occuring.
    			-- (from EV_WIDGET_I)

    	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_PICK_AND_DROPABLE_I)

    	displayed_column (i: INTEGER_32): EV_GRID_COLUMN
    			-- `i'-th displayed column. May not correspond
    			-- to column if one or more columns have been
    			--- hidden via hide.
    		require
    			i_positive: i > 0
    			i_column_not_greater_than_displayed_column_count: i <= displayed_column_count
    		ensure
    			column_not_void: Result /= Void

    	drop_actions: EV_PND_ACTION_SEQUENCE
    			-- Actions to be performed when a pebble is dropped here.
    		ensure -- from EV_PICK_AND_DROPABLE_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	dynamic_content_function: FUNCTION [ANY, TUPLE [INTEGER_32, INTEGER_32], EV_GRID_ITEM]
    			-- Function which computes the item that resides in a particular position of the
    			-- grid while is_content_partially_dynamic or `is_content_completely_dynamic.

    	foreground_color: EV_COLOR
    			-- Color of foreground features like text.
    			-- (from EV_COLORIZABLE_I)

    	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_capture: BOOLEAN
    			-- Does `Current' have capture?

    	has_focus: BOOLEAN
    			-- Does `Current' have focus?

    	help_context: FUNCTION [ANY, TUPLE, EV_HELP_CONTEXT]
    			-- Agent that evaluates to help context sent to help engine when help is requested
    			-- (from EV_HELP_CONTEXTABLE_I)
    		ensure -- from EV_HELP_CONTEXTABLE_I
    			current_if_exists: internal_help_context /= Void implies Result = internal_help_context

    	internal_pointer_style: EV_POINTER_STYLE
    			-- Cursor displayed when screen pointer is over current widget,
    			-- as seen from interface.
    			-- (from EV_WIDGET_I)

    	is_column_resize_immediate: BOOLEAN
    			-- Is the user resizing of a reflected immediately in `Current'?
    			-- If `False', the column width is only updated upon completion of the resize.

    	is_content_partially_dynamic: BOOLEAN
    			-- Is the content of `Current' partially dynamic? If `True' then
    			-- whenever an item must be re-drawn and it is not already set within `Current',
    			-- then it is queried via `content_requested_actions'. The returned item is added
    			-- to `Current' so the query only occurs once.

    	is_dock_executing: BOOLEAN
    			-- Is `Current' in the process of a dockable transport?
    			-- (from EV_DOCKABLE_SOURCE_I)

    	is_dockable: BOOLEAN
    			-- Is `Current' dockable?
    			-- (from EV_DOCKABLE_SOURCE_I)

    	is_external_docking_enabled: BOOLEAN
    			-- Is `Current' able to be docked into an EV_DOCKABLE_DIALOG
    			-- When there is no valid EV_DRAGABLE_TARGET upon completion
    			-- of the transport?
    			-- (from EV_DOCKABLE_SOURCE_I)

    	is_external_docking_relative: BOOLEAN
    			-- Will dockable dialog displayed when `Current' is docked externally
    			-- be displayed relative to parent window of `Current'?
    			-- Otherwise displayed as a standard window.
    			-- (from EV_DOCKABLE_SOURCE_I)

    	is_header_displayed: BOOLEAN
    			-- Is the header displayed in `Current'.

    	is_horizontal_overscroll_enabled: BOOLEAN
    			-- Does the virtual width of `Current' include the
    			-- position of the final column plus the viewable_width.
    			-- If `True', this enables horizontal scrolling until the last column
    			-- is at the very left of the viewable area. If `False', scrolling
    			-- may be performed until the last column is at the left of the viewable
    			-- area.

    	is_horizontal_scrolling_per_item: BOOLEAN
    			-- Is horizontal scrolling performed on a per-item basis?
    			-- If `True', each change of the horizontal scroll bar increments the horizontal
    			-- offset by the current column width.
    			-- If `False', the scrolling is smooth on a per-pixel basis.

    	is_resizing_divider_enabled: BOOLEAN
    			-- Is a vertical divider displayed during column resizing?

    	is_resizing_divider_solid: BOOLEAN
    			-- Is resizing divider displayed during column resizing drawn as a solid line?
    			-- If `False', a dashed line style is used.

    	is_row_height_fixed: BOOLEAN
    			-- Must all rows in `Current' have the same height?

    	is_vertical_overscroll_enabled: BOOLEAN
    			-- Does the virtual height of `Current' include the
    			-- position of the final row plus the viewable_height.
    			-- If `True', this enables vertical scrolling until the last row
    			-- is at the very top of the viewable area. If `False', scrolling
    			-- may be performed until the last row is at the bottom of the viewable
    			-- area.

    	is_vertical_scrolling_per_item: BOOLEAN
    			-- Is vertical scrolling performed on a per-item basis?
    			-- If `True', each change of the vertical scroll bar increments the vertical
    			-- offset by the current row height.
    			-- If `False', the scrolling is smooth on a per-pixel basis.

    	item (a_column: INTEGER_32; a_row: INTEGER_32): EV_GRID_ITEM
    			-- Cell at `a_column' and `a_row' position, Void if none.
    		require
    			a_column_positive: a_column > 0
    			a_column_less_than_column_count: a_column <= column_count
    			a_row_positive: a_row > 0
    			a_row_less_than_row_count: a_row <= row_count

    	cell_item: EV_WIDGET
    			-- Current item.
    			-- (from EV_CONTAINER_I)

    	item_at_virtual_position (a_virtual_x, a_virtual_y: INTEGER_32): EV_GRID_ITEM
    			-- Cell at virtual position `a_virtual_x', `a_virtual_y' or
    			-- `Void' if none.
    		require
    			virtual_x_valid: a_virtual_x >= 0 and a_virtual_x <= virtual_width
    			virtual_y_valid: a_virtual_y >= 0 and a_virtual_y <= virtual_height

    	locked_indexes: ARRAYED_LIST [EV_GRID_LOCKED_I]
    			-- Sorted array of all columns and rows currently locked.

    	maximum_virtual_x_position: INTEGER_32
    			-- Maximum permitted virtual x position based on current dimensions and properties.
    			-- Properties that affect this value are is_vertical_scrolling_per_item and
    			-- is_vertical_overscroll_enabled.
    		ensure
    			result_non_negative: Result >= 0

    	maximum_virtual_y_position: INTEGER_32
    			-- Maximum permitted virtual y position based on current properties.
    			-- Properties that affect this value are is_horizontal_scrolling_per_item and
    			-- is_horizontal_overscroll_enabled.
    		ensure
    			result_non_negative: Result >= 0

    	merged_radio_button_groups: ARRAYED_LIST [EV_CONTAINER]
    			-- `Result' is all other radio button groups
    			-- merged with `Current'.
    			-- (from EV_CONTAINER_I)
    		ensure -- from EV_CONTAINER_I
    			current_not_included: Result /= Void implies not Result.has (interface)

    	not_external_docking_enabled: BOOLEAN
    			-- Attribute used for `is_externally_dockable'. We must implement
    			-- `is_externally_dockable' this way as we have no easy solution to
    			-- assign `True' to `is_externally_dockable'.
    			-- (from EV_DOCKABLE_SOURCE_I)

    	not_is_external_docking_relative: BOOLEAN
    			-- Will dockable dialog displayed when `Current' is docked externally
    			-- be displayed relative to parent window of `Current'?
    			-- Otherwise displayed as a standard window.
    			-- Internal reversed value of is_external_docking_relative as we cannot
    			-- easily initialize a BOOLE to True in this case.
    			-- (from EV_DOCKABLE_SOURCE_I)

    	original_parent_position: INTEGER_32
    			-- Original position in parent. Required
    			-- to restore widget later.
    			-- (from EV_DOCKABLE_SOURCE_I)

    	parent: EV_CONTAINER
    			-- Container widget that contains `Current'.
    			-- (Void if `Current' is not in a container)
    			-- (from EV_WIDGET_I)

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

    	pebble_function: FUNCTION [ANY, TUPLE, ANY]
    			-- Returns data to be transported by pick and drop mechanism.
    			-- (from EV_PICK_AND_DROPABLE_I)

    	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_I)

    	pebble_x_position: INTEGER_32
    			-- Initial x position for pick and drop relative to `Current'.
    			-- (from EV_PICK_AND_DROPABLE_I)

    	pebble_y_position: INTEGER_32
    			-- Initial y position for pick and drop relative to `Current'.
    			-- (from EV_PICK_AND_DROPABLE_I)

    	pick_actions: EV_PND_START_ACTION_SEQUENCE
    			-- Actions to be performed when pebble is picked up.
    		ensure -- from EV_PICK_AND_DROPABLE_ACTION_SEQUENCES_I
    			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.
    		ensure -- from EV_PICK_AND_DROPABLE_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	pixels_displayed_after_final_column: INTEGER_32
    			-- Width in pixels displayed after the final column of `Current'.
    			-- If `is_horizontal_overdraw_enabled' this is viewable_width less the final column width.
    			-- If not `is_horizontal_overdraw_enabled' and is_horizontal_scrolling_per_item this is
    			-- the number of pixels required to ensure the first visible column is flush to the left of the
    			-- viewable area of `Current'.

    	pixels_displayed_after_final_row: INTEGER_32
    			-- Height in pixels displayed after the final row of `Current'.
    			-- If `is_vertical_overdraw_enabled' this is viewable_height less the final row height.
    			-- If not `is_vertical_overdraw_enabled' and is_vertical_scrolling_per_item this is
    			-- the number of pixels required to ensure the first visible row is flush to the top of the
    			-- viewable area of `Current'.
    		ensure
    			result_non_negative: Result >= 0
    			result_no_more_than_viewable_height: Result <= viewable_height
    			no_rows_contained_implies_result_is_viewable_height: row_count = 0 implies Result = viewable_height
    			valid_result_with_rows_with_overdraw_with_fixed_row_height: row_count > 0 and is_row_height_fixed and is_vertical_overscroll_enabled implies Result = viewable_height - row_height
    			valid_result_with_rows_when_per_pixel_scrolling_with_no_overdraw: row_count > 0 and is_vertical_scrolling_per_item = False and is_vertical_overscroll_enabled = False implies Result = 0
    			valid_result_with_fixed_height_rows_when_per_item_scrolling_and_no_overdraw: row_count > 0 and is_row_height_fixed and is_vertical_scrolling_per_item and is_vertical_scrolling_per_item and row (row_count).virtual_y_position + row_height > viewable_height and not is_vertical_overscroll_enabled implies Result <= row_height

    	background_pixmap: EV_PIXMAP
    			-- Image displayed on `Current'.
    			-- (from EV_PIXMAPABLE_I)

    	pointer_position: EV_COORDINATE
    			-- Position of the screen pointer relative to `Current'.
    			-- (from EV_WIDGET_I)
    		ensure -- from EV_WIDGET_I
    			result_not_void: Result /= Void

    	pointer_style: EV_POINTER_STYLE
    			-- Cursor displayed when screen pointer is over current widget.
    			-- Void if none has been set using `set_pointer_position'.
    			-- (from EV_WIDGET_I)

    	real_source: EV_DOCKABLE_SOURCE
    			-- `Result' is EV_DOCKABLE_SOURCE which should be
    			-- dragged when docking begins on `Current'.
    			-- (from EV_DOCKABLE_SOURCE_I)

    	real_target: EV_DOCKABLE_TARGET
    			-- `Result' is target used during a dockable transport if
    			-- mouse pointer is above `Current'.
    			-- (from EV_WIDGET_I)

    	remove_selection
    			-- Ensure that selected_rows and selected_items are empty.
    		ensure
    			selected_items_empty: selected_items.is_empty
    			selected_rows_empty: selected_rows.is_empty
    			selected_columns_empty: selected_columns.is_empty

    	row (a_row: INTEGER_32): EV_GRID_ROW
    			-- Row at index `a_row'.
    		require
    			a_row_positive: a_row > 0
    			a_row_not_greater_than_row_count: a_row <= row_count
    		ensure
    			row_not_void: Result /= Void

    	row_at_virtual_position (a_virtual_y: INTEGER_32; ignore_locked_rows: BOOLEAN): EV_GRID_ROW
    			-- Row at virtual y position `a_virtual_y'.
    		require
    			virtual_y_valid: a_virtual_y >= 0 and a_virtual_y <= virtual_height

    	row_height: INTEGER_32
    			-- Height of all rows within `Current'. Only has an effect on `Current'
    			-- while is_row_height_fixed, otherwise the individual height of each
    			-- row is used directly.

    	selected_columns: ARRAYED_LIST [EV_GRID_COLUMN]
    			-- All columns selected in `Current'.
    		ensure
    			result_not_void: Result /= Void

    	selected_items: ARRAYED_LIST [EV_GRID_ITEM]
    			-- All items selected in `Current'.
    		ensure
    			result_not_void: Result /= Void

    	selected_rows: ARRAYED_LIST [EV_GRID_ROW]
    			-- All rows selected in `Current'.
    		ensure
    			result_not_void: Result /= Void

    	set_default_key_processing_handler (a_handler: like default_key_processing_handler)
    			-- Assign default_key_processing_handler to `a_handler'.

    	subrow_indent: INTEGER_32
    			-- Number of pixels horizontally by which each subrow is indented
    			-- from its `parent_row'.

    	tooltip: STRING_32
    			-- Tooltip displayed on `Current'.

    	unlock_column (a_column: EV_GRID_COLUMN_I)
    			-- Ensure column `a_column' is unlocked.
    		ensure
    			column_not_locked: not a_column.is_locked

    	unlock_row (a_row: EV_GRID_ROW_I)
    			-- Ensure row `a_row' is unlocked.
    		ensure
    			a_row_not_locked: not a_row.is_locked

    	viewable_height: INTEGER_32
    			-- Height of `Current' available to view displayed items. Does
    			-- not include width of any displayed scroll bars and/or header if shown.
    			-- Is equivalent to `viewport.height' and by storing this, multiple queries are far quicker
    			-- as the grid is only resized periodically and we no longer have to call EiffelVision for the value.

    	viewable_width: INTEGER_32
    			-- Width of `Current' available to view displayed items. Does
    			-- not include width of any displayed scroll bars. Is equivalent to `viewport.width' and
    			-- by storing this, multiple queries are far quicker as the grid is only resized periodically
    			-- and we no longer have to call EiffelVision for the value.

    	viewable_x_offset: INTEGER_32
    			-- Horizontal distance in pixels from the left edge of `Current' to
    			-- the left edge of the viewable area (defined by viewable_width, viewable_height)
    			-- in which all content is displayed.
    		ensure
    			viewable_x_offset_valid: Result >= 0 and Result <= width

    	viewable_y_offset: INTEGER_32
    			-- Vertical distance in pixels from the top edge of `Current' to
    			-- the top edge of the viewable area (defined by viewable_width, viewable_height)
    			-- in which all content is displayed.
    		ensure
    			viewable_y_offset_valid: Result >= 0 and Result <= height

    	virtual_height: INTEGER_32
    			-- Height of virtual area in pixels.
    		ensure
    			result_non_negative: Result >= 0

    	virtual_width: INTEGER_32
    			-- Width of virtual area in pixels.
    		ensure
    			result_non_negative: Result >= 0

    	virtual_x_position: INTEGER_32
    			-- Horizontal offset of viewable area in relation to the left edge of
    			-- the virtual area in pixels.
    		ensure
    			valid_result: Result >= 0 and Result <= maximum_virtual_x_position

    	virtual_y_position: INTEGER_32
    			-- Vertical offset of viewable area in relation to the top edge of
    			-- the virtual area in pixels.
    		ensure
    			valid_result: Result >= 0 and Result <= maximum_virtual_y_position

    feature -- Measurement

    	height: INTEGER_32
    			-- Vertical size in pixels.
    			-- (from EV_POSITIONED_I)

    	minimum_height: INTEGER_32
    			-- Minimum vertical size in pixels.
    			-- (from EV_POSITIONED_I)

    	minimum_width: INTEGER_32
    			-- Minimum horizontal size in pixels.
    			-- (from EV_POSITIONED_I)

    	screen_x: INTEGER_32
    			-- Horizontal offset relative to screen.
    			-- (from EV_WIDGET_I)

    	screen_y: INTEGER_32
    			-- Vertical offset relative to screen.
    			-- (from EV_WIDGET_I)

    	width: INTEGER_32
    			-- Horizontal size in pixels.
    			-- (from EV_POSITIONED_I)

    	x_position: INTEGER_32
    			-- Horizontal offset relative to parent x_position in pixels.
    			-- (from EV_POSITIONED_I)

    	y_position: INTEGER_32
    			-- Vertical offset relative to parent y_position in pixels.
    			-- (from EV_POSITIONED_I)

    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

    	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

    	are_columns_drawn_above_rows: BOOLEAN
    			-- For drawing purposes, are columns drawn above rows?
    			-- If `True', for all cells within `Current' whose column and row have non-Void
    			-- foreground or background colors, the column colors are given priority.
    			-- If `False', the colors of the row are given priority.

    	closest_dockable_target: EV_DOCKABLE_TARGET
    			-- `Result' is first dockable target that is_dockable found by recursively
    			-- searching up through the parenting structure from the widget
    			-- currently underneath the pointer position.
    			-- `Result' will be `Void' if a dockable target is not found.
    			-- (from EV_DOCKABLE_SOURCE_I)
    		ensure -- from EV_DOCKABLE_SOURCE_I
    			result_is_dockable: Result /= Void implies Result.is_docking_enabled

    	column_displayed (a_column: INTEGER_32): BOOLEAN
    			-- May column `a_column' be displayed when `Current' is?
    			-- Will return False if hide has been called on column `a_column'.
    			-- A value of True does not signify that column `a_column' is visible on screen at that particular time.
    		require
    			a_column_within_bounds: a_column > 0 and a_column <= column_count

    	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

    	disable_capture
    			-- Release the user input.

    	displayed_background_color (a_column, a_row: INTEGER_32): EV_COLOR
    			-- `Result' is background color to be displayed for item at position `a_column', `a_row'
    			-- on parts of the cell space in which the item is not displayed. i.e. for the background
    			-- area of a tree structure.
    		require
    			valid_column: a_column >= 1 and a_column <= column_count
    			valid_row: a_row >= 1 and a_row <= row_count
    		ensure
    			result_not_void: Result /= Void

    	drawables_have_focus: BOOLEAN
    			-- Does drawable or any of the drawables representing locked rows currently
    			-- have the focus? If `False' then selection should be grayed.

    	enable_capture
    			-- Grab the user input.

    	first_visible_column: EV_GRID_COLUMN
    			-- First column visible in `Current' or Void if column_count = 0
    			-- If is_horizontal_scrolling_per_item, the first visible column may be only partially visible.
    		require
    			is_displayed: is_displayed
    		ensure
    			has_columns_implies_result_not_void: column_count > 0 implies Result /= Void
    			no_columns_implies_result_void: column_count = 0 implies Result = Void

    	first_visible_row: EV_GRID_ROW
    			-- First row visible in `Current' or Void if row_count = 0
    			-- If is_vertical_scrolling_per_item, the first visible row may be only partially visible.
    		require
    			is_displayed: is_displayed
    		ensure
    			has_rows_implies_result_not_void: row_count > 0 implies Result /= Void
    			no_rows_implies_result_void: row_count = 0 implies Result = Void

    	focused_selection_color: EV_COLOR
    			-- Color used to show selection within items while focused.

    	focused_selection_text_color: EV_COLOR
    			-- Color used to show selection within items while focused.

    	get_next_target (a_widget: EV_WIDGET): EV_DOCKABLE_TARGET
    			-- `Result' is next dockable target that is is_dockable found by
    			-- recursively seraching up the parenting structure from `current_target'.
    			-- `Result' will be `Void' if none.
    			-- (from EV_DOCKABLE_SOURCE_I)
    		require -- from EV_DOCKABLE_SOURCE_I
    			a_widget_not_void: a_widget /= Void
    		ensure -- from EV_DOCKABLE_SOURCE_I
    			result_is_dockable: Result /= Void implies Result.is_docking_enabled

    	internal_non_sensitive: BOOLEAN
    			-- Is `Current' not sensitive to input as seen
    			-- from interface?
    			-- (from EV_SENSITIVE_I)

    	is_docking_enabled: BOOLEAN
    			-- May `Current' be docked to?
    			-- (from EV_DOCKABLE_TARGET_I)

    	is_multiple_item_selection_enabled: BOOLEAN
    			-- Does clicking or keyboard navigating via arrow keys select an item, with multiple
    			-- item selection permitted via the use of Ctrl and Shift keys?

    	is_multiple_row_selection_enabled: BOOLEAN
    			-- Does clicking or keyboard navigating via arrow keys select a row, with multiple
    			-- row selection permitted via the use of Ctrl and Shift keys?

    	is_multiple_selection_enabled: BOOLEAN
    			-- Is `Current' in either multiple item or row selection mode?

    	is_row_selection_enabled: BOOLEAN
    			-- Is `Current' in either single or multiple row selection mode?

    	is_selection_keyboard_handling_enabled: BOOLEAN
    			-- May an item be selected via the keyboard?

    	is_selection_on_click_enabled: BOOLEAN
    			-- Will an item be selected if clicked upon by the user?

    	is_selection_on_single_button_click_enabled: BOOLEAN
    			-- Will an item be selected if clicked upon via mouse button `1' only.
    			-- Mouse buttons `1' and `2' will leave selection unchanged.

    	is_single_item_selection_enabled: BOOLEAN
    			-- Does clicking or keyboard navigating via arrow keys select an item, unselecting
    			-- any previously selected items?

    	is_single_row_selection_enabled: BOOLEAN
    			-- Does clicking or keyboard navigating via arrow keys select a row, unselecting
    			-- any previously selected row?

    	is_transport_enabled: BOOLEAN
    			-- Is the transport mechanism enabled?
    			-- (from EV_PICK_AND_DROPABLE_I)

    	is_tree_enabled: BOOLEAN
    			-- Is tree functionality enabled?

    	last_visible_column: EV_GRID_COLUMN
    			-- Last column visible in `Current' or Void if column_count = 0
    			-- The last visible column may be only partially visible.
    		require
    			is_displayed: is_displayed
    		ensure
    			has_columns_implies_result_not_void: column_count > 0 implies Result /= Void
    			no_columns_implies_result_void: column_count = 0 implies Result = Void

    	last_visible_row: EV_GRID_ROW
    			-- Last row visible in `Current' or Void if row_count = 0
    			-- The last visible row may be only partially visible.
    		require
    			is_displayed: is_displayed
    		ensure
    			has_rows_implies_result_not_void: row_count > 0 implies Result /= Void
    			no_rows_implies_result_void: row_count = 0 implies Result = Void

    	mode_is_drag_and_drop: BOOLEAN
    			-- Is the transport mechanism drag and drop?
    			-- (from EV_PICK_AND_DROPABLE_I)

    	mode_is_pick_and_drop: BOOLEAN
    			-- Is the transport mechanism pick and drop?
    			-- (from EV_PICK_AND_DROPABLE_I)

    	mode_is_target_menu: BOOLEAN
    			-- Is the transport mechanism target menu?
    			-- (from EV_PICK_AND_DROPABLE_I)

    	non_focused_selection_color: EV_COLOR
    			-- Color used to show selection within items while not focused.

    	non_focused_selection_text_color: EV_COLOR
    			-- Color used for text of selected items while not focused.

    	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))

    	tree_node_connector_color: EV_COLOR
    			-- Color of connectors drawn between tree nodes within `Current'.

    	user_is_sensitive: BOOLEAN
    			-- Is the object sensitive to user input.
    			-- (from EV_SENSITIVE_I)

    	veto_dock_function: FUNCTION [ANY, TUPLE [EV_DOCKABLE_SOURCE], BOOLEAN]
    			-- Function used to veto transport.
    			-- (from EV_DOCKABLE_TARGET_I)

    	viewable_row_indexes: ARRAYED_LIST [INTEGER_32]
    			-- Row indexes that are currently viewable in the grid in its present state.
    			-- For example, if the first node is a non expanded tree that has 10 subrows, the contents
    			-- would be 1, 11, 12, 13, 14, ...
    		ensure
    			result_not_void: Result /= Void

    	visible_column_indexes: ARRAYED_LIST [INTEGER_32]
    			-- All columns that are currently visible in `Current'.
    		require
    			is_displayed: is_displayed
    		ensure
    			result_not_void: Result /= Void

    	visible_row_indexes: ARRAYED_LIST [INTEGER_32]
    			-- All rows that are currently visible in `Current'.
    		require
    			is_displayed: is_displayed
    		ensure
    			result_not_void: Result /= Void

    feature -- Status setting

    	activate_item (a_item: EV_GRID_ITEM)
    			-- Setup `a_item' for user interactive editing.
    		require
    			a_item_not_void: a_item /= Void

    	activate_window: EV_POPUP_WINDOW
    			-- Window used to edit grid item contents on `activate'.

    	currently_active_item: EV_GRID_ITEM
    			-- Item that is currently active.

    	deactivate_item (a_item: EV_GRID_ITEM)
    			-- Cleanup from previous call to `activate'.
    		require
    			a_item_not_void: a_item /= Void

    	disable_always_selected
    			-- Allow the user to completely remove the selection from the grid by clicking on an item,
    			-- clicking on a Void area or by Ctrl clicking the selected item itself.

    	disable_column_resize_immediate
    			-- Ensure is_column_resize_immediate is `False'.
    		ensure
    			not_is_column_resize_immediate: not is_column_resize_immediate

    	disable_column_separators
    			-- Ensure are_column_separators_enabled is `False'.
    		ensure
    			column_separators_disabled: not are_column_separators_enabled

    	disable_columns_drawn_above_rows
    			-- Ensure are_columns_drawn_above_rows is `False'.
    		ensure
    			columns_drawn_below_rows: not are_columns_drawn_above_rows

    	disable_dockable
    			-- Ensure `Current' is not dockable
    			-- (from EV_DOCKABLE_SOURCE_I)
    		ensure -- from EV_DOCKABLE_SOURCE_I
    			not_is_dockable: not is_dockable

    	disable_docking
    			-- Ensure is_docking_enabled is False.
    			-- `Current' will not accept docking.
    			-- (from EV_DOCKABLE_TARGET_I)
    		ensure -- from EV_DOCKABLE_TARGET_I
    			not_dockable: not is_docking_enabled
    			id_not_stored_in_application: not (create {EV_ENVIRONMENT}).application.implementation.dockable_targets.has (interface.object_id)

    	disable_dynamic_content
    			-- Ensure contents of `Current' are not dynamic and are no longer retrieved as such.
    		ensure
    			content_not_dynamic: not is_content_partially_dynamic

    	disable_external_docking
    			-- Forbid `Current' to be docked into an EV_DOCKABLE_DIALOG
    			-- When there is no valid EV_DRAGABLE_TARGET upon completion
    			-- of the transport?
    			-- (from EV_DOCKABLE_SOURCE_I)
    		require -- from EV_DOCKABLE_SOURCE_I
    			is_dockable: is_dockable
    		ensure -- from EV_DOCKABLE_SOURCE_I
    			not_externally_dockable: not is_external_docking_enabled

    	disable_external_docking_relative
    			-- Assign `False' to is_external_docking_relative, ensuring that
    			-- a dockable dialog displayed when `Current' is docked externally
    			-- is displayed as a standard window.
    			-- (from EV_DOCKABLE_SOURCE_I)
    		require -- from EV_DOCKABLE_SOURCE_I
    			external_docking_enabled: is_external_docking_enabled
    		ensure -- from EV_DOCKABLE_SOURCE_I
    			external_docking_not_relative: not is_external_docking_relative

    	disable_full_redraw_on_virtual_position_change
    			-- Ensure is_full_redraw_on_virtual_position_change_enabled is `False'.
    		ensure
    			not_is_full_redraw_on_virtual_position_change_enabled: not is_full_redraw_on_virtual_position_change_enabled

    	disable_horizontal_overscroll
    			-- Ensure is_horizontal_overscroll_enabled is `False'.
    		ensure
    			not_is_horizontal_overscroll_enabled: not is_horizontal_overscroll_enabled

    	disable_horizontal_scrolling_per_item
    			-- Ensure horizontal scrolling is performed on a per-pixel basis.
    		ensure
    			horizontal_scrolling_performed_per_pixel: not is_horizontal_scrolling_per_item

    	disable_pebble_positioning
    			-- Assign `False' to pebble_positioning_enabled.
    			-- (from EV_PICK_AND_DROPABLE_I)

    	disable_resizing_divider
    			-- Ensure no vertical divider is displayed during column resizing.
    		ensure
    			resizing_divider_disabled: not is_resizing_divider_enabled

    	disable_row_height_fixed
    			-- Permit rows to have varying heights.
    		require
    			not_dynamic_content_enabled_with_height_not_bounded: not (is_content_partially_dynamic and is_vertical_overscroll_enabled = False)

    	disable_row_separators
    			-- Ensure are_row_separators_enabled is `False'.
    		ensure
    			row_separators_disabled: not are_row_separators_enabled

    	disable_selection_keyboard_handling
    			-- Disable selection handling of items via the keyboard.
    		ensure
    			selection_keyboard_handling_disabled: not is_selection_keyboard_handling_enabled

    	disable_selection_on_click
    			-- Disable selection handling when items are clicked upon.
    		ensure
    			selection_on_click_disabled: not is_selection_on_click_enabled

    	disable_solid_resizing_divider
    			-- Ensure resizing divider displayed during column resizing
    			-- is displayed as a dashed line.
    		ensure
    			dashed_resizing_divider: not is_resizing_divider_solid

    	disable_transport
    			-- Deactivate pick/drag and drop mechanism.
    			-- (from EV_PICK_AND_DROPABLE_I)
    		ensure -- from EV_PICK_AND_DROPABLE_I
    			is_transport_disabled: not is_transport_enabled

    	disable_tree
    			-- Disable tree functionality for `Current'.
    			-- All subrows of rows contained are unparented,
    			-- which flattens the tree structure.
    		ensure
    			tree_disabled: not is_tree_enabled

    	disable_vertical_overscroll
    			-- Ensure is_vertical_overscroll_enabled is `False'.
    		require
    			dynamic_content_not_enabled_with_variable_row_heights: not (is_content_partially_dynamic and not is_row_height_fixed)
    		ensure
    			not_is_vertical_overscroll_enabled: not is_vertical_overscroll_enabled

    	disable_vertical_scrolling_per_item
    			-- Ensure vertical scrolling is performed on a per-pixel basis.
    		ensure
    			vertical_scrolling_performed_per_pixel: not is_vertical_scrolling_per_item

    	enable_always_selected
    			-- Ensure that the user may not completely remove the selection from `Current'.

    	enable_column_resize_immediate
    			-- Ensure is_column_resize_immediate is `True'.
    		ensure
    			is_column_resize_immediate: is_column_resize_immediate

    	enable_column_separators
    			-- Ensure are_column_separators_enabled is `True'.
    		ensure
    			column_separators_enabled: are_column_separators_enabled

    	enable_columns_drawn_above_rows
    			-- Ensure are_columns_drawn_above_rows is `True'.
    		ensure
    			columns_drawn_above_rows: are_columns_drawn_above_rows

    	enable_dockable
    			-- Allow `Current' to be dockable
    			-- (from EV_DOCKABLE_SOURCE_I)
    		ensure -- from EV_DOCKABLE_SOURCE_I
    			is_dockable: is_dockable

    	enable_docking
    			-- Ensure is_docking_enabled is True.
    			-- `Current' will accept docking from a
    			-- compatible EV_DOCKABLE_SOURCE.
    			-- (from EV_DOCKABLE_TARGET_I)
    		ensure -- from EV_DOCKABLE_TARGET_I
    			is_dockable: is_docking_enabled
    			id_stored_in_application: (create {EV_ENVIRONMENT}).application.implementation.dockable_targets.has (interface.object_id)

    	enable_external_docking
    			-- Allow `Current' to be docked into an EV_DOCKABLE_DIALOG
    			-- When there is no valid EV_DRAGABLE_TARGET upon completion
    			-- of the transport?
    			-- (from EV_DOCKABLE_SOURCE_I)
    		require -- from EV_DOCKABLE_SOURCE_I
    			is_dockable: is_dockable
    		ensure -- from EV_DOCKABLE_SOURCE_I
    			is_externally_dockable: is_external_docking_enabled

    	enable_external_docking_relative
    			-- Assign `True' to is_external_docking_relative, ensuring that
    			-- a dockable dialog displayed when `Current' is docked externally
    			-- is displayed relative to the top level window.
    			-- (from EV_DOCKABLE_SOURCE_I)
    		require -- from EV_DOCKABLE_SOURCE_I
    			external_docking_enabled: is_external_docking_enabled
    		ensure -- from EV_DOCKABLE_SOURCE_I
    			external_docking_not_relative: is_external_docking_relative

    	enable_full_redraw_on_virtual_position_change
    			-- Ensure is_full_redraw_on_virtual_position_change_enabled is `True'.
    		ensure
    			is_full_redraw_on_virtual_position_change_enabled: is_full_redraw_on_virtual_position_change_enabled

    	enable_horizontal_overscroll
    			-- Ensure is_horizontal_overscroll_enabled is `True'.
    		ensure
    			is_horizontal_overscroll_enabled: is_horizontal_overscroll_enabled

    	enable_horizontal_scrolling_per_item
    			-- Ensure horizontal scrolling is performed on a per-item basis.
    		ensure
    			horizontal_scrolling_performed_per_item: is_horizontal_scrolling_per_item

    	enable_multiple_item_selection
    			-- Allow the user to select more than one item via clicking or navigating using the keyboard arrow keys.
    			-- Multiple items may be selected via Ctrl and Shift keys.
    		ensure
    			multiple_item_selection_enabled: is_multiple_item_selection_enabled

    	enable_multiple_row_selection
    			-- Allow the user to select more than one row via clicking or navigating using the keyboard arrow keys.
    			-- Multiple rows may be selected via Ctrl and Shift keys.
    		ensure
    			multiple_row_selection_enabled: is_multiple_row_selection_enabled

    	enable_partial_dynamic_content
    			-- Ensure contents of `Current' must be retrieved when required via
    			-- `content_requested_actions' only if the item is not already set
    			-- in `Current'.
    		require
    			not_row_height_variable_and_vertical_overscroll_enabled: not (not is_row_height_fixed and is_vertical_overscroll_enabled)
    			not_row_height_variable_and_vertical_scrolling_per_pixel: not (not is_row_height_fixed and not is_vertical_scrolling_per_item)
    		ensure
    			content_partially_dynamic: is_content_partially_dynamic

    	enable_pebble_positioning
    			-- Assign `True' to pebble_positioning_enabled.
    			-- (from EV_PICK_AND_DROPABLE_I)

    	enable_resizing_divider
    			-- Ensure a vertical divider is displayed during column resizing.
    		ensure
    			resizing_divider_enabled: is_resizing_divider_enabled

    	enable_row_height_fixed
    			-- Ensure all rows have the same height.

    	enable_row_separators
    			-- Ensure are_row_separators_enabled is `True'.
    		ensure
    			row_separators_enabled: are_row_separators_enabled

    	enable_selection_keyboard_handling
    			-- Enable selection handling of items via the keyboard.
    		ensure
    			selection_keyboard_handling_enabled: is_selection_keyboard_handling_enabled

    	enable_selection_on_click
    			-- Enable selection handling of items when clicked upon.
    		ensure
    			selection_on_click_enabled: is_selection_on_click_enabled

    	enable_selection_on_single_button_click
    			-- Enable selection handling of items when clicked upon via mouse button `1'.
    			-- This is useful for implementing Contextual Menus where the selection may need
    			-- to remain unchanged when using mouse button `3' for instance.
    		ensure
    			selection_on_single_click_enabled: is_selection_on_single_button_click_enabled and then is_selection_on_click_enabled

    	enable_single_item_selection
    			-- Allow the user to select a single item via clicking or navigating using the keyboard arrow keys.
    		ensure
    			single_item_selection_enabled: is_single_item_selection_enabled

    	enable_single_row_selection
    			-- Allow the user to select a single row via clicking or navigating using the keyboard arrow keys.
    		ensure
    			single_row_selection_enabled: is_single_row_selection_enabled

    	enable_solid_resizing_divider
    			-- Ensure resizing divider displayed during column resizing
    			-- is displayed as a solid line.
    		ensure
    			solid_resizing_divider: is_resizing_divider_solid

    	enable_transport
    			-- Activate pick/drag and drop mechanism.
    			-- (from EV_PICK_AND_DROPABLE_I)
    		require -- from EV_PICK_AND_DROPABLE_I
    			pebble_not_void: pebble /= Void or pebble_function /= Void
    		ensure -- from EV_PICK_AND_DROPABLE_I
    			is_transport_enabled: interface.implementation.is_transport_enabled

    	enable_tree
    			-- Enable tree functionality for `Current'.
    			-- Must be `True' to perform any tree structure functions on `Current'.
    			-- Use enable_tree and disable_tree to set this state.
    		ensure
    			tree_enabled: is_tree_enabled

    	enable_vertical_overscroll
    			-- Ensure is_vertical_overscroll_enabled is `True'.
    		ensure
    			is_vertical_overscroll_enabled: is_vertical_overscroll_enabled

    	enable_vertical_scrolling_per_item
    			-- Ensure vertical scrolling is performed on a per-item basis.
    		ensure
    			vertical_scrolling_performed_per_item: is_vertical_scrolling_per_item

    	has_horizontal_scrolling_per_item_just_changed: BOOLEAN
    			-- Has the horizontal scrolling method just been changed between
    			-- per item and per pixel? This is used to adjust the scroll bar's position
    			-- to approximate it's original position during the recomputation of it's
    			-- settings in recompute_horizontal_scroll_bar.

    	has_vertical_scrolling_per_item_just_changed: BOOLEAN
    			-- Has the vertical scrolling method just been changed between
    			-- per item and per pixel? This is used to adjust the scroll bar's position
    			-- to approximate it's original position during the recomputation of it's
    			-- settings in recompute_vertical_scroll_bar.

    	hide
    			-- Request that `Current' not be displayed when its parent is.
    			-- (from EV_WIDGET_I)

    	hide_column (a_column: INTEGER_32)
    			-- Ensure column `a_column' is not visible in `Current'.
    		require
    			a_column_within_bounds: a_column > 0 and a_column <= column_count
    		ensure
    			column_not_displayed: not column_displayed (a_column)

    	hide_header
    			-- Ensure header is hidden.
    		ensure
    			header_not_displayed: not is_header_displayed

    	hide_horizontal_scroll_bar
    			-- Ensure no horizontal scroll bar is displayed in `Current'
    			-- at any time.
    		ensure
    			not_is_horizontal_scroll_bar_show_requested: not is_horizontal_scroll_bar_show_requested

    	hide_tree_node_connectors
    			-- Ensure no connectors are displayed between nodes of tree structure in `Current'.
    		ensure
    			tree_node_connectors_hidden: not are_tree_node_connectors_shown

    	hide_vertical_scroll_bar
    			-- Ensure no vertical scroll bar is displayed in `Current'
    			-- at any time.
    		ensure
    			not_is_vertical_scroll_bar_show_requested: not is_vertical_scroll_bar_show_requested

    	internal_disable_dockable
    			-- Platform specific implementation of disable_dockable.
    			-- (from EV_DOCKABLE_SOURCE_I)

    	internal_enable_dockable
    			-- Platform specific implementation of enable_dockable.
    			-- (from EV_DOCKABLE_SOURCE_I)

    	is_always_selected: BOOLEAN
    			-- Ensure that the user may not completely remove the selection from `Current'.

    	is_horizontal_scroll_bar_show_requested: BOOLEAN
    			-- Will a horizontal scroll bar be displayed in `Current' when
    			-- virtual_width exceeds viewable_width?

    	is_item_height_changing: BOOLEAN
    			-- Is height of items in `Current' changing?

    	is_vertical_scroll_bar_show_requested: BOOLEAN
    			-- Will a vertical scroll bar be displayed in `Current' when
    			-- virtual_height exceeds viewable_height?

    	item_pebble_function: FUNCTION [ANY, TUPLE [EV_GRID_ITEM], ANY]
    			-- User pebble function

    	lock_update
    			-- Ensure is_locked is `True', thereby preventing graphical
    			-- updates until unlock_update is called.
    		ensure
    			is_locked: is_locked

    	merge_radio_button_groups (other: EV_CONTAINER)
    			-- Merge `Current' radio button group with that of `other'.
    			-- (from EV_CONTAINER_I)

    	redraw
    			-- Force `Current' to be re-drawn when next idle.

    	remove_default_key_processing_handler
    			-- Ensure default_key_processing_handler is Void.
    			-- (from EV_WIDGET_I)
    		ensure -- from EV_WIDGET_I
    			default_key_processing_handler_removed: default_key_processing_handler = Void

    	remove_pebble
    			-- Remove pebble.
    			-- (from EV_PICK_AND_DROPABLE_I)
    		ensure -- from EV_PICK_AND_DROPABLE_I
    			pebble_removed: pebble = Void and pebble_function = Void
    			is_transport_disabled: not is_transport_enabled

    	remove_real_source
    			-- Ensure real_source is `Void'.
    			-- (from EV_DOCKABLE_SOURCE_I)
    		require -- from EV_DOCKABLE_SOURCE_I
    			is_dockable: is_dockable
    		ensure -- from EV_DOCKABLE_SOURCE_I
    			real_source_void: real_source = Void

    	remove_real_target
    			-- Ensure real_target is `Void'.
    			-- (from EV_WIDGET_I)
    		ensure -- from EV_WIDGET_I
    			real_target_void: real_target = Void

    	select_column (a_column: INTEGER_32)
    			-- Ensure all items in `a_column' are selected.
    		require
    			a_column_within_bounds: a_column > 0 and a_column <= column_count
    			column_displayed: column_displayed (a_column)
    		ensure
    			column_selected: column (a_column).is_selected

    	select_row (a_row: INTEGER_32)
    			-- Ensure all items in `a_row' are selected.
    		require
    			a_row_within_bounds: a_row > 0 and a_row <= row_count
    		ensure
    			row_selected: row (a_row).is_selected

    	set_actual_drop_target_agent (an_agent: like actual_drop_target_agent)
    			-- Assign `an_agent' to actual_drop_target_agent.
    			-- (from EV_WIDGET_I)
    		require -- from EV_WIDGET_I
    			an_agent_not_void: an_agent /= Void
    		ensure -- from EV_WIDGET_I
    			assigned: actual_drop_target_agent = an_agent

    	set_column_count_to (a_column_count: INTEGER_32)
    			-- Resize `Current' to have `a_column_count' columns.
    		require
    			a_column_count_not_negative: a_column_count >= 0
    		ensure
    			column_count_set: column_count = a_column_count

    	set_default_colors
    			-- Set foreground and background color to their default values.

    	set_drag_and_drop_mode
    			-- Set transport mechanism to drag and drop,
    			-- (from EV_PICK_AND_DROPABLE_I)
    		ensure -- from EV_PICK_AND_DROPABLE_I
    			mode_is_drag_and_drop: mode_is_drag_and_drop

    	set_dynamic_content_function (a_function: FUNCTION [ANY, TUPLE [INTEGER_32, INTEGER_32], EV_GRID_ITEM])
    			-- Function which computes the item that resides in a particular position of the
    			-- grid while is_content_partially_dynamic or `is_content_completely_dynamic.
    		require
    			a_function_not_void: a_function /= Void
    		ensure
    			dynamic_content_function_set: dynamic_content_function = a_function

    	set_first_visible_row (a_row: INTEGER_32)
    			-- Set `a_row' as the first row visible in `Current' as long
    			-- as there are enough rows after `a_row' to fill the remainder of `Current'.
    		require
    			valid_row_index: a_row >= 1 and a_row <= row_count

    	set_focus
    			-- Grab keyboard focus.

    	set_focused_selection_color (a_color: EV_COLOR)
    			-- Assign `a_color' to focused_selection_color.
    		require
    			a_color_not_void: a_color /= Void
    		ensure
    			focused_selection_color_set: focused_selection_color = a_color

    	set_focused_selection_text_color (a_color: EV_COLOR)
    			-- Assign `a_color' to focused_selection_text_color.
    		require
    			a_color_not_void: a_color /= Void
    		ensure
    			focused_selection_text_color_set: focused_selection_text_color = a_color

    	set_node_pixmaps (an_expand_node_pixmap, a_collapse_node_pixmap: EV_PIXMAP)
    			-- Assign `an_expand_node_pixmap' to expand_node_pixmap and `a_collapse_node_pixmap'
    			-- to collapse_node_pixmap. These pixmaps are used in rows containing subrows for
    			-- expanding/collapsing the row.
    		require
    			pixmaps_not_void: an_expand_node_pixmap /= Void and a_collapse_node_pixmap /= Void
    			pixmaps_dimensions_identical: an_expand_node_pixmap.width = a_collapse_node_pixmap.width and an_expand_node_pixmap.height = a_collapse_node_pixmap.height
    		ensure
    			pixmaps_set: expand_node_pixmap = an_expand_node_pixmap and collapse_node_pixmap = a_collapse_node_pixmap

    	set_non_focused_selection_color (a_color: EV_COLOR)
    			-- Assign `a_color' to non_focused_selection_color.
    		require
    			a_color_not_void: a_color /= Void
    		ensure
    			non_focused_selection_color_set: non_focused_selection_color = a_color

    	set_non_focused_selection_text_color (a_color: EV_COLOR)
    			-- Assign `a_color' to non_focused_selection_text_color.
    		require
    			a_color_not_void: a_color /= Void
    		ensure
    			non_focused_selection_text_color_set: non_focused_selection_text_color = a_color

    	set_pebble (a_pebble: like pebble)
    			-- Assign `a_pebble' to pebble.
    		require -- from EV_PICK_AND_DROPABLE_I
    			a_pebble_not_void: a_pebble /= Void
    		ensure -- from EV_PICK_AND_DROPABLE_I
    			pebble_assigned: interface.implementation.pebble = a_pebble
    			is_transport_enabled: interface.implementation.is_transport_enabled

    	set_pebble_function (a_function: FUNCTION [ANY, TUPLE, ANY])
    			-- Assign `a_function' to pebble_function.
    		require -- from EV_PICK_AND_DROPABLE_I
    			a_function_not_void: a_function /= Void
    		ensure -- from EV_PICK_AND_DROPABLE_I
    			pebble_function_assigned: interface.implementation.pebble_function = a_function
    			is_transport_enabled: interface.implementation.is_transport_enabled

    	set_pebble_position (a_x, a_y: INTEGER_32)
    			-- Set the initial position for pick and drop relative to `Current'.
    			-- (from EV_PICK_AND_DROPABLE_I)
    		ensure -- from EV_PICK_AND_DROPABLE_I
    			pick_x_assigned: pick_x = a_x
    			pick_y_assigned: pick_y = a_y

    	set_pick_and_drop_mode
    			-- Set transport mechanism to pick and drop,
    			-- (from EV_PICK_AND_DROPABLE_I)
    		ensure -- from EV_PICK_AND_DROPABLE_I
    			mode_is_pick_and_drop: mode_is_pick_and_drop

    	set_real_source (dockable_source: EV_DOCKABLE_SOURCE)
    			-- Set `dockable_source' to be the widget moved when a
    			-- drag begins on `Current'.
    			-- (from EV_DOCKABLE_SOURCE_I)
    		require -- from EV_DOCKABLE_SOURCE_I
    			is_dockable: is_dockable
    			dockable_source_not_void: dockable_source /= Void
    		ensure -- from EV_DOCKABLE_SOURCE_I
    			real_source_assigned: real_source = dockable_source

    	set_real_target (a_target: EV_DOCKABLE_TARGET)
    			-- Assign `a_target' to real_target.
    			-- (from EV_WIDGET_I)
    		require -- from EV_WIDGET_I
    			target_not_void: a_target /= Void
    		ensure -- from EV_WIDGET_I
    			assigned: real_target = a_target

    	set_row_count_to (a_row_count: INTEGER_32)
    			-- Resize `Current' to have `a_row_count' columns.
    		require
    			a_row_count_non_negative: a_row_count >= 0
    		ensure
    			row_count_set: row_count = a_row_count

    	set_row_height (a_row_height: INTEGER_32)
    			-- Set height of all rows within `Current' to `a_row_height
    			-- If not is_row_height_fixed then use the height individually per row instead.
    		require
    			is_row_height_fixed: is_row_height_fixed
    			a_row_height_positive: a_row_height >= 1
    		ensure
    			row_height_set: row_height = a_row_height

    	set_separator_color (a_color: EV_COLOR)
    			-- Set `a_color' as separator_color.
    		require
    			a_color_not_void: a_color /= Void
    		ensure
    			separator_color_set: separator_color = a_color

    	set_subrow_indent (a_subrow_indent: INTEGER_32)
    			-- Set subrow_indent to `a_subrow_indent'.
    		require
    			a_subrow_indent_non_negtive: a_subrow_indent >= 0
    		ensure
    			subrow_indent_set: subrow_indent = a_subrow_indent

    	set_target_menu_mode
    			-- Set transport mechanism to target_menu.
    			-- (from EV_PICK_AND_DROPABLE_I)
    		ensure -- from EV_PICK_AND_DROPABLE_I
    			mode_is_target_menu: mode_is_target_menu

    	set_tree_node_connector_color (a_color: EV_COLOR)
    			-- Set `a_color' as tree_node_connector_color.
    		require
    			a_color_not_void: a_color /= Void
    		ensure
    			tree_node_connector_color_set: tree_node_connector_color = a_color

    	set_veto_dock_function (a_function: FUNCTION [ANY, TUPLE [EV_DOCKABLE_SOURCE], BOOLEAN])
    			-- Assign `a_function' to veto_dock_function.
    			-- (from EV_DOCKABLE_TARGET_I)
    		require -- from EV_DOCKABLE_TARGET_I
    			a_function_not_void: a_function /= Void
    		ensure -- from EV_DOCKABLE_TARGET_I
    			veto_function_set: veto_dock_function = a_function

    	set_virtual_position (virtual_x, virtual_y: INTEGER_32)
    			-- Move `Current' to virtual position `virtual_x', `virtual_y'.
    		require
    			virtual_x_valid: virtual_x >= 0 and virtual_x <= maximum_virtual_x_position
    			virtual_y_valid: virtual_y >= 0 and virtual_y <= maximum_virtual_y_position
    		ensure
    			virtual_position_set: virtual_x_position = virtual_x and virtual_y_position = virtual_y

    	show
    			-- Request that `Current' be displayed when its parent is.
    			-- (from EV_WIDGET_I)

    	show_column (a_column: INTEGER_32)
    			-- Ensure column `a_column' is visible in `Current'.
    		require
    			a_column_within_bounds: a_column > 0 and a_column <= column_count
    		ensure
    			column_displayed: column_displayed (a_column)

    	show_header
    			-- Ensure header displayed.
    		ensure
    			header_displayed: is_header_displayed

    	show_horizontal_scroll_bar
    			-- Ensure a horizontal scroll bar is displayed in `Current'
    			-- when required. Note that this does not force the horizontal
    			-- scroll bar to be visible, simply ensures that when virtual_width
    			-- is greater than viewable_width, the scroll bar is displayed.
    		ensure
    			is_horizontal_scroll_bar_show_requested: is_horizontal_scroll_bar_show_requested

    	show_tree_node_connectors
    			-- Ensure connectors are displayed between nodes of tree structure in `Current'.
    		ensure
    			tree_node_connectors_shown: are_tree_node_connectors_shown

    	show_vertical_scroll_bar
    			-- Ensure a vertical scroll bar is displayed in `Current'
    			-- when required. Note that this does not force the vertical
    			-- scroll bar to be visible, simply ensures that when virtual_height
    			-- is greater than viewable_height, the scroll bar is displayed.
    		ensure
    			is_vertical_scroll_bar_show_requested: is_vertical_scroll_bar_show_requested

    	unlock_update
    			-- Ensure is_locked is `False', thereby ensuring graphical
    			-- updates occur as normal. The complete client area
    			-- is refreshed to synchronize the display with the contents.
    		ensure
    			not_is_locked: not is_locked

    	unmerge_radio_button_groups (other: EV_CONTAINER)
    			-- Remove `other' from radio button group of `Current'.
    			-- (from EV_CONTAINER_I)

    	user_disable_sensitive
    			-- Make object desensitive to user input.
    			-- (from EV_SENSITIVE_I)
    		ensure -- from EV_SENSITIVE_I
    			is_desensitive: not user_is_sensitive

    	user_enable_sensitive
    			-- Make object sensitive to user input.
    			-- (from EV_SENSITIVE_I)
    		ensure -- from EV_SENSITIVE_I
    			is_sensitive_if_parent_sensitive: (has_parent and then parent_is_sensitive) implies interface.implementation.is_sensitive
    			is_sensitive_if_orphaned: not has_parent implies interface.implementation.is_sensitive

    feature -- Element change

    	disable_drawables_have_focus
    			-- Ensure drawables_have_focus is set to `False'.
    		ensure
    			drawables_have_focus: drawables_have_focus = False

    	enable_drawables_have_focus
    			-- Ensure drawables_have_focus is set to `True'.
    		ensure
    			drawables_have_focus: drawables_have_focus = True

    	extend (an_item: like cell_item)
    			-- Ensure that structure includes `an_item'.
    			-- (from EV_CELL_I)
    		require -- from EV_CONTAINER_I
    			v_not_void: an_item /= Void

    	insert_new_column (a_index: INTEGER_32)
    			-- Insert a new column at index `a_index'.
    		require
    			a_index_within_range: a_index > 0 and a_index <= column_count + 1
    		ensure
    			column_count_set: column_count = old column_count + 1

    	insert_new_rows (rows_to_insert, i: INTEGER_32)
    			-- Insert `rows_to_insert' rows at index `i'.
    		require
    			i_within_range: i > 0 and i <= row_count + 1
    			rows_to_insert_positive: rows_to_insert >= 1
    			not_inserting_within_existing_subrow_structure: i <= row_count implies row (i).parent_row = Void
    		ensure
    			row_count_set: row_count = old row_count + rows_to_insert

    	insert_new_rows_parented (rows_to_insert, i: INTEGER_32; a_parent_row: EV_GRID_ROW)
    			-- Insert `rows_to_insert' new rows at index `i' and make those rows subnodes of `a_parent_row'.
    		require
    			i_positive: i > 0
    			tree_enabled: is_tree_enabled
    			rows_to_insert_positive: row_count >= 1
    			i_less_than_row_count: i <= row_count + 1
    			a_parent_row_not_void: a_parent_row /= Void
    			i_valid_for_parent: i > a_parent_row.index and i <= a_parent_row.index + a_parent_row.subrow_count_recursive + 1
    			not_inserting_within_existing_subrow_structure: i < a_parent_row.index + a_parent_row.subrow_count_recursive implies row (i).parent_row = a_parent_row
    		ensure
    			row_count_set: row_count = old row_count + rows_to_insert
    			subrow_count_set: a_parent_row.subrow_count = old a_parent_row.subrow_count + rows_to_insert

    	move_columns (i, j, n: INTEGER_32)
    			-- Move `n' columns at index `i' to index `j'.
    		require
    			i_valid: i > 0 and then i <= column_count
    			j_valid: j > 0 and then j <= column_count + 1
    			n_valid: n > 0 and then i + n <= column_count + 1
    			move_not_overlapping: n > 1 implies (j <= i or else j >= i + n)
    		ensure
    			columns_moved: (j < i implies column (j) = old column (i) and then column (j + n - 1) = old column (i + n - 1)) and (j > i + n implies column (j - n) = old column (i) and then column (j - 1) = old column (i + n - 1))
    			column_count_unchanged: column_count = old column_count

    	move_rows_to_parent (i, j, n: INTEGER_32; a_parent_row: EV_GRID_ROW)
    			-- All purpose row moving routine.
    			-- Move `n' rows starting at index `i' immediately before row at index `j'.
    			-- If `j' = `row_count + 1' the rows are moved to the very bottom of the grid.
    			-- If is_tree_enabled, all rows moved that share the same tree structure depth
    			-- as row `i' are reparented as a subrow of `a_parent_row'.
    			-- If `a_parent_row' is Void then they are set as root nodes of the grid tree.
    			-- All parent rows within the rows moved that have a tree structure depth
    			-- greater than that of row `i' are left parented.
    		require
    			i_valid: i > 0 and then i <= row_count
    			j_valid: j > 0 and then j <= row_count + 1
    			n_valid: n > 0 and then i + n <= row_count + 1
    			move_not_overlapping: n > 1 implies (j <= i or else j >= i + n)
    			not_breaking_existing_subrow_structure: j = row_count + 1 or else ((a_parent_row = Void and j <= row_count and (i + n <= row_count) and ((j = i or j = i + 1) implies row (i + n).parent_row = Void))) or else ((a_parent_row = Void and j <= row_count) implies row (j).parent_row = Void)
    			j_valid_for_move_to_a_parent_row: a_parent_row /= Void implies ((j = i + n and then (i > a_parent_row.index and i <= a_parent_row.index + a_parent_row.subrow_count_recursive + 1)) or (j > a_parent_row.index and j <= a_parent_row.index + a_parent_row.subrow_count_recursive + 1))
    			not_inserting_within_existing_subrow_structure: (a_parent_row /= Void and j <= a_parent_row.index + a_parent_row.subrow_count_recursive) implies row (j).parent_row = a_parent_row
    		ensure
    			rows_moved: (j <= i implies row (j) = old row (i) and then row (j + n - 1) = old row (i + n - 1)) and (j > i + n implies row (j - n) = old row (i) and then row (j - 1) = old row (i + n - 1))
    			row_count_unchanged: row_count = old row_count

    	pixmap_equal_to (a_pixmap: EV_PIXMAP): BOOLEAN
    			-- Is `a_pixmap' equal to `pixmap'?
    			-- (from EV_PIXMAPABLE_I)

    	remove_help_context
    			-- Remove key press action associated with `EV_APPLICATION.help_key'.
    			-- (from EV_HELP_CONTEXTABLE_I)
    		require -- from EV_HELP_CONTEXTABLE_I
    			help_context_not_void: help_context /= Void
    		ensure -- from EV_HELP_CONTEXTABLE_I
    			no_help_context: internal_help_context = Void

    	remove_background_pixmap
    			-- Make `pixmap' `Void'.
    			-- (from EV_PIXMAPABLE_I)
    		ensure -- from EV_PIXMAPABLE_I
    			pixmap_removed: background_pixmap = Void

    	replace (v: like cell_item)
    			-- Replace item with `v'.
    			-- (from EV_CONTAINER_I)

    	set_background_color (a_color: like background_color)
    			-- Assign `a_color' to foreground_color.
    			-- (from EV_COLORIZABLE_I)
    		require -- from EV_COLORIZABLE_I
    			a_color_not_void: a_color /= Void
    		ensure -- from EV_COLORIZABLE_I
    			background_color_assigned: is_initialized implies interface.implementation.background_color.is_equal (a_color)

    	set_foreground_color (a_color: like foreground_color)
    			-- Assign `a_color' to foreground_color.
    			-- (from EV_COLORIZABLE_I)
    		require -- from EV_COLORIZABLE_I
    			a_color_not_void: a_color /= Void
    		ensure -- from EV_COLORIZABLE_I
    			foreground_color_assigned: is_initialized implies interface.implementation.foreground_color.is_equal (a_color)

    	set_help_context (an_help_context: like help_context)
    			-- Assign `a_help_context' to help_context.
    			-- Assign `an_help_context' to help_context.
    			-- (from EV_HELP_CONTEXTABLE_I)
    		require -- from EV_HELP_CONTEXTABLE_I
    			an_help_context_not_void: an_help_context /= Void
    		ensure -- from EV_HELP_CONTEXTABLE_I
    			help_context_assigned: help_context.is_equal (an_help_context)

    	set_item (a_column, a_row: INTEGER_32; a_item: EV_GRID_ITEM)
    			-- Set grid item at position (`a_column', `a_row') to `a_item'.
    			-- If `a_item' is `Void', the current item (if any) is removed.
    		require
    			a_column_positive: a_column > 0
    			a_row_positive: a_row > 0
    			a_item_not_parented: a_item /= Void implies a_item.parent = Void
    			valid_tree_structure_on_item_insertion: a_item /= Void and is_tree_enabled and then a_row <= row_count and row (a_row).parent_row /= Void implies a_column >= row (a_row).parent_row.index_of_first_item
    			item_may_be_added_if_row_is_a_subrow: a_item /= Void and then a_row <= row_count and then row (a_row).is_part_of_tree_structure implies row (a_row).is_index_valid_for_item_setting_if_tree_node (a_column)
    			item_may_be_removed_if_row_is_a_subrow: a_item = Void and then a_row <= row_count and then row (a_row).is_part_of_tree_structure implies row (a_row).is_index_valid_for_item_removal_if_tree_node (a_column)
    		ensure
    			item_set: item (a_column, a_row) = a_item

    	set_minimum_height (a_minimum_height: INTEGER_32)
    			-- Set the minimum vertical size to `a_minimum_height' in pixels.
    			-- (from EV_WIDGET_I)
    		require -- from EV_WIDGET_I
    			a_minimum_height_positive: a_minimum_height >= 0
    		ensure -- from EV_WIDGET_I
    			minimum_height_assigned: is_usable implies interface.minimum_height = a_minimum_height

    	set_minimum_size (a_minimum_width, a_minimum_height: INTEGER_32)
    			-- Set the minimum horizontal size to `a_minimum_width' in pixels.
    			-- Set the minimum vertical size to `a_minimum_height' in pixels.
    			-- (from EV_WIDGET_I)
    		require -- from EV_WIDGET_I
    			a_minimum_width_positive: a_minimum_width >= 0
    			a_minimum_height_positive: a_minimum_height >= 0
    		ensure -- from EV_WIDGET_I
    			minimum_width_assigned: is_usable implies interface.minimum_width = a_minimum_width
    			minimum_height_assigned: is_usable implies interface.minimum_height = a_minimum_height

    	set_minimum_width (a_minimum_width: INTEGER_32)
    			-- Set the minimum horizontal size to `a_minimum_width' in pixels.
    			-- (from EV_WIDGET_I)
    		require -- from EV_WIDGET_I
    			a_minimum_width_positive: a_minimum_width >= 0
    		ensure -- from EV_WIDGET_I
    			minimum_width_assigned: is_usable implies interface.minimum_width = a_minimum_width

    	set_background_pixmap (a_pixmap: EV_PIXMAP)
    			-- Assign `a_pixmap' to `pixmap'.
    			-- (from EV_PIXMAPABLE_I)
    		require -- from EV_PIXMAPABLE_I
    			pixmap_not_void: a_pixmap /= Void

    	set_tooltip (a_tooltip: STRING_GENERAL)
    			-- Assign `a_tooltip' to `Current'.
    		require -- from EV_TOOLTIPABLE_I
    			a_tooltip_not_void: a_tooltip /= Void

    feature -- Removal

    	clear
    			-- Remove all items from `Current'.
    		ensure
    			to_implement_assertion ("EV_GRID_I.clear - All items positions return `Void'.")

    	remove_column (a_column: INTEGER_32)
    			-- Remove column `a_column'.
    		require
    			a_column_positive: a_column > 0
    			a_column_less_than_column_count: a_column <= column_count
    		ensure
    			column_count_updated: column_count = old column_count - 1
    			old_column_removed: (old column (a_column)).parent = Void

    	remove_row (a_row: INTEGER_32)
    			-- Remove row `a_row' and all subrows recursively.
    			-- If `row (a_row).subrow_count_recursive' is greater than 0 then
    			-- all subrows of the row are also removed from `Current'.
    		require
    			a_row_positive: a_row > 0
    			a_row_less_than_row_count: a_row <= row_count
    		ensure
    			row_count_updated: row_count = old row_count - (old row (a_row).subrow_count_recursive + 1)
    			old_row_removed: (old row (a_row)).parent = Void
    			node_counts_correct_in_parent: old (row_internal (a_row).parent_row_i) /= Void implies (old row_internal (a_row).parent_row_i).node_counts_correct
    			to_implement_assertion ("EV_GRID.remove_row%T%TAll old recursive subrows removed.")

    	remove_rows (lower_index, upper_index: INTEGER_32)
    			-- Remove all rows from `lower_index' to `upper_index' inclusive.
    		require
    			valid_lower_index: lower_index >= 1 and lower_index <= row_count
    			valid_upper_index: upper_index >= lower_index and upper_index <= row_count
    		ensure
    			row_count_consistent: row_count = (old row_count) - (upper_index - lower_index + 1)
    			lower_row_removed: (old row (lower_index)).parent = Void
    			upper_row_removed: (old row (upper_index)).parent = Void
    			to_implement_assertion (once "middle_rows_removed from lower to upper all old rows parent = Void")

    	wipe_out
    			-- Remove all columns and rows from `Current'.
    		ensure
    			columns_removed: column_count = 0
    			rows_removed: row_count = 0

    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)

    	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

    	close_dockable_dialog (dockable_dialog: EV_DOCKABLE_DIALOG)
    			-- Close request received by `dockable_dialog' so
    			-- restore widget contained back to its original position
    			-- in its old parent if possible.
    			-- We must fire `dock_ended' actions.
    			-- (from EV_DOCKABLE_SOURCE_I)
    		ensure -- from EV_DOCKABLE_SOURCE_I
    			dockable_dialog_destroyed: dockable_dialog.is_destroyed

    	complete_dock
    			-- Complete a dock from source_being_docked.
    			-- (from EV_DOCKABLE_SOURCE_I)
    		require -- from EV_DOCKABLE_SOURCE_I
    			source_being_docked: source_being_docked /= Void
    		ensure -- from EV_DOCKABLE_SOURCE_I
    			not_dock_executing: not is_dock_executing
    			insert_separator_not_parented: insert_sep.parent = Void
    			insert_label_not_parented: insert_label.parent = Void

    	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)

    	propagate_background_color
    			-- Propagate the current background color of the
    			-- container to the children.
    			-- (from EV_CONTAINER_I)
    		ensure -- from EV_CONTAINER_I
    			background_color_propagated: interface.cell_background_color_propagated

    	propagate_foreground_color
    			-- Propagate the current foreground color of the
    			-- container to the children.
    			-- (from EV_CONTAINER_I)
    		ensure -- from EV_CONTAINER_I
    			foreground_color_propagated: interface.cell_foreground_color_propagated

    	refresh_now
    			-- Force an immediate redraw of `Current'.
    			-- (from EV_WIDGET_I)

    feature -- Inapplicable

    	drag_cursor: EV_POINTER_STYLE
    			-- Cursor used when `Current' is being transported.
    			-- (from EV_DOCKABLE_SOURCE_I)

    feature {ANY}

    	disable_horizontal_offset_set_to_zero_when_items_smaller_than_viewable_width
    			-- Ensure is_horizontal_offset_set_to_zero_when_items_smaller_than_viewable_width is `False'
    		ensure
    			set: is_horizontal_offset_set_to_zero_when_items_smaller_than_viewable_width = False

    	is_horizontal_offset_set_to_zero_when_items_smaller_than_viewable_width: BOOLEAN
    			-- This is required for cases where you have two grids, one acting as a header for another.
    			-- If the vertical scroll bar of one is displayed, and the simulated header does not have
    			-- scroll bars displayed, then the virtual positions permitted are not in synch and we wish
    			-- to turn off the automatic scrolling of the header grid as it should always change in synch
    			-- with the main grid. This should probably be moved into the interface of EV_GRID at some point.

    	recompute_horizontal_scroll_bar
    			-- Recompute horizontal scroll bar positioning.

    feature -- Access EV_DRAGABLE_SOURCE.

    	dockable_dialog_target: EV_DOCKABLE_DIALOG
    			-- A dockable dialog that will be created as
    			-- necessary. This is not a local, to avoid it
    			-- being garbage collected.
    			-- (from EV_SHARED_TRANSPORT_I)

    	global_drag_targets: ARRAYED_LIST [INTEGER_32]
    			-- Shortcut to EV_APPLICATION.pnd_targets.
    			-- (from EV_SHARED_TRANSPORT_I)

    	insert_label: EV_CELL
    			-- Label used to indicate where `Current' will be placed in target.
    			-- (from EV_SHARED_TRANSPORT_I)
    		ensure -- from EV_SHARED_TRANSPORT_I
    			result_not_void: Result /= Void

    	insert_label_imp: EV_CELL_I
    			-- Once access to implementation of Insert_label.
    			-- (from EV_SHARED_TRANSPORT_I)
    		ensure -- from EV_SHARED_TRANSPORT_I
    			Result /= Void

    	insert_sep: EV_TOOL_BAR_SEPARATOR
    			-- Once access to a separator used to indicate the insertion position
    			-- when moving tool bar items.
    			-- (from EV_SHARED_TRANSPORT_I)

    	insert_sep_imp: EV_TOOL_BAR_SEPARATOR_I
    			-- Once access to implementation of Insert_sep.
    			-- (from EV_SHARED_TRANSPORT_I)
    		ensure -- from EV_SHARED_TRANSPORT_I
    			Result /= Void

    	internal_screen: EV_SCREEN
    			-- Once access to an EV_SCREEN.
    			-- (from EV_SHARED_TRANSPORT_I)

    	original_x_offset: INTEGER_16
    			-- Original x_offset and original_y_offset of transport
    			-- realtive to widget. Only used for dragable transports.
    			-- (from EV_SHARED_TRANSPORT_I)

    	original_y_offset: INTEGER_16
    			-- Original x_offset and original_y_offset of transport
    			-- realtive to widget. Only used for dragable transports.
    			-- (from EV_SHARED_TRANSPORT_I)

    	originating_source: EV_DOCKABLE_SOURCE_I
    			-- Dragable source that originated the transport of `source_being_dragged'.
    			-- (from EV_SHARED_TRANSPORT_I)

    	remove_insert_label
    			-- Remove Insert_label from its current parent.
    			-- We must handle a special case for cells. If the parent is a cell,
    			-- then we remove the cell from its parent, and then restore it.
    			-- Otherwise, when the label, removed, the cell keeps it size, and cells
    			-- are normally used with real_target when the cell must
    			-- not be visible.
    			-- (from EV_SHARED_TRANSPORT_I)
    		ensure -- from EV_SHARED_TRANSPORT_I
    			not_parented: insert_label.parent = Void

    	remove_insert_sep
    			-- Ensure `inset_sep' is not parented.
    			-- (from EV_SHARED_TRANSPORT_I)
    		ensure -- from EV_SHARED_TRANSPORT_I
    			not_parented: insert_sep.parent = Void

    	source_being_docked: EV_DOCKABLE_SOURCE_I
    			-- Dragable source currently being transported. May be a
    			-- WIDGET_IMP or an EV_TOOL_BAR_BUTTON_IMP.
    			-- (from EV_SHARED_TRANSPORT_I)

    feature -- Access EV_PICK_AND_DROPABLE.

    	default_accept_cursor: EV_POINTER_STYLE
    			-- Used in lieu of a user defined accept_cursor.
    			-- (from EV_SHARED_TRANSPORT_I)

    	default_deny_cursor: EV_POINTER_STYLE
    			-- Used in lieu of a user defined deny_cursor.
    			-- (from EV_SHARED_TRANSPORT_I)

    	default_pixmaps: EV_STOCK_PIXMAPS
    			-- Default pixmaps
    			-- (from EV_SHARED_TRANSPORT_I)

    	global_pnd_targets: HASH_TABLE [INTEGER_32, INTEGER_32]
    			-- Shortcut to EV_APPLICATION.pnd_targets.
    			-- (from EV_SHARED_TRANSPORT_I)

    	rubber_band_is_drawn: BOOLEAN
    			-- Is a rubber band line currently on the screen?
    			-- (from EV_SHARED_TRANSPORT_I)

    feature -- Access common.

    	pointer_x: INTEGER_16
    			-- (from EV_SHARED_TRANSPORT_I)

    	pointer_y: INTEGER_16
    			-- (from EV_SHARED_TRANSPORT_I)

    feature -- Event handling

    	column_deselect_actions: ACTION_SEQUENCE [TUPLE [EV_GRID_COLUMN]]
    			-- Actions to be performed when a column is deselected.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)
    		ensure -- from EV_GRID_ACTION_SEQUENCES_I
    			result_not_void: Result /= Void

    	column_select_actions: ACTION_SEQUENCE [TUPLE [EV_GRID_COLUMN]]
    			-- Actions to be performed when a column is selected.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)
    		ensure -- from EV_GRID_ACTION_SEQUENCES_I
    			result_not_void: Result /= Void

    	dock_ended_actions: EV_NOTIFY_ACTION_SEQUENCE
    			-- Actions to be performed after a dock completes from `Current'.
    			-- Either to a dockable target or a dockable dialog.
    			-- (from EV_DOCKABLE_SOURCE_ACTION_SEQUENCES_I)
    		ensure -- from EV_DOCKABLE_SOURCE_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	dock_started_actions: EV_NOTIFY_ACTION_SEQUENCE
    			-- Actions to be performed when pebble is picked up.
    			-- (from EV_DOCKABLE_SOURCE_ACTION_SEQUENCES_I)
    		ensure -- from EV_DOCKABLE_SOURCE_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	docked_actions: EV_DOCKABLE_SOURCE_ACTION_SEQUENCE
    			-- Actions to be performed
    			-- (from EV_DOCKABLE_TARGET_ACTION_SEQUENCES_I)
    		ensure -- from EV_DOCKABLE_TARGET_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	file_drop_actions: ACTION_SEQUENCE [TUPLE [LIST [STRING_32]]]
    			-- Actions to be performed when an OS file drop occurs on `Current'.
    			-- (from EV_WIDGET_ACTION_SEQUENCES_I)
    		ensure -- from EV_WIDGET_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	fill_background_actions: ACTION_SEQUENCE [TUPLE [EV_DRAWABLE, INTEGER_32, INTEGER_32, INTEGER_32, INTEGER_32]]
    			-- Actions to be performed when part of the background area of the grid that is outside of the
    			-- area filled by row_count and column_count needs to be redrawn.
    			-- By default, the grid fills the area in its background_color. If one or more agents are
    			-- contained in this action sequence, the grid is no longer responsible for drawing its background
    			-- and the agents must redraw this area, otherwise graphical glitches may appear.
    			-- The five pieces of event data passed are:
    			-- drawable: EV_DRAWABLE The drawable into which you must draw the background.
    			-- virtual_x: INTEGER The virtual x position of the area to be redrawn.
    			-- virtual_y: INTEGER The virtual y position of the area to be redrawn.
    			-- width: INTEGER The width of the area that must be redrawn.
    			-- height: INTEGER The height of the area that must be redrawn.
    			-- The upper left corner of the drawing must start at 0x0 in drawable with an area given by width
    			-- and height. The virtual coordinates specify the position of the area in relation to the grid's
    			-- virtual positiion which is essential if you wish to draw something such as a texture which must be
    			-- matched based on its position.
    			-- Note that fill_background_actions may be fired multiple times to fill the complete area of the
    			-- background that is invalid.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)
    		ensure -- from EV_GRID_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	focus_in_actions: EV_NOTIFY_ACTION_SEQUENCE
    			-- Actions to be performed when keyboard focus is gained.
    			-- (from EV_WIDGET_ACTION_SEQUENCES_I)
    		ensure -- from EV_WIDGET_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	focus_out_actions: EV_NOTIFY_ACTION_SEQUENCE
    			-- Actions to be performed when keyboard focus is lost.
    			-- (from EV_WIDGET_ACTION_SEQUENCES_I)
    		ensure -- from EV_WIDGET_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	item_activate_actions: ACTION_SEQUENCE [TUPLE [EV_GRID_ITEM, EV_POPUP_WINDOW]]
    			-- Actions to be performed to setup an item that is currently activated.
    			-- Overrides default setup of activatable items.
    			-- Arguments of TUPLE (with names for clarity):
    			--
    			-- activate_item: EV_GRID_ITEM -- The item that is currently activated.
    			-- popup_window: EV_WINDOW -- The popup window used to interactively edit activate_item, window has already been sized and positioned.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)

    	item_deactivate_actions: EV_GRID_ITEM_ACTION_SEQUENCE
    			-- Actions to be performed when an item is deactivated.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)
    		ensure -- from EV_GRID_ACTION_SEQUENCES_I
    			result_not_void: Result /= Void

    	item_deselect_actions: EV_GRID_ITEM_ACTION_SEQUENCE
    			-- Actions to be performed when an item is deselected.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)
    		ensure -- from EV_GRID_ACTION_SEQUENCES_I
    			result_not_void: Result /= Void

    	item_drop_actions: ACTION_SEQUENCE [TUPLE [EV_GRID_ITEM, ANY]]
    			-- Actions to be performed when a pebble is dropped here.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)
    		ensure -- from EV_GRID_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	item_select_actions: EV_GRID_ITEM_ACTION_SEQUENCE
    			-- Actions to be performed when an item is selected.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)
    		ensure -- from EV_GRID_ACTION_SEQUENCES_I
    			result_not_void: Result /= Void

    	key_press_actions: EV_KEY_ACTION_SEQUENCE
    			-- Actions to be performed when a keyboard key is pressed.
    			-- (from EV_WIDGET_ACTION_SEQUENCES_I)
    		ensure -- from EV_WIDGET_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	key_press_string_actions: EV_KEY_STRING_ACTION_SEQUENCE
    			-- Actions to be performed when a keyboard press generates a displayable character.
    			-- (from EV_WIDGET_ACTION_SEQUENCES_I)
    		ensure -- from EV_WIDGET_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	key_release_actions: EV_KEY_ACTION_SEQUENCE
    			-- Actions to be performed when a keyboard key is released.
    			-- (from EV_WIDGET_ACTION_SEQUENCES_I)
    		ensure -- from EV_WIDGET_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	mouse_wheel_actions: EV_INTEGER_ACTION_SEQUENCE
    			-- Actions to be performed when mouse wheel is rotated.
    			-- (from EV_WIDGET_ACTION_SEQUENCES_I)
    		ensure -- from EV_WIDGET_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	new_item_actions: EV_NEW_ITEM_ACTION_SEQUENCE
    			-- Actions to be performed when a new item is added.
    			-- (from EV_CONTAINER_ACTION_SEQUENCES_I)
    		ensure -- from EV_CONTAINER_ACTION_SEQUENCES_I
    			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_WIDGET_ACTION_SEQUENCES_I)
    		ensure -- from EV_WIDGET_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	pointer_button_press_item_actions: ACTION_SEQUENCE [TUPLE [INTEGER_32, INTEGER_32, INTEGER_32, EV_GRID_ITEM]]
    			-- Actions to be performed when a pointer press event is received by a grid.
    			-- Arguments (with names for clarity):
    			--
    			-- x_pos: INTEGER -- The x position of the press in grid virtual coordinates.
    			-- y_pos: INTEGER -- The y position of the press in grid virtual coordinates.
    			-- a_button: INTEGER -- The index of the pressed button.
    			-- item: EV_GRID_ITEM -- If the press occurred above an item, this is the pointed item, otherwise argument is set to `Void'.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)
    		ensure -- from EV_GRID_ACTION_SEQUENCES_I
    			result_not_void: Result /= Void

    	pointer_button_release_actions: EV_POINTER_BUTTON_ACTION_SEQUENCE
    			-- Actions to be performed when screen pointer button is released.
    			-- (from EV_WIDGET_ACTION_SEQUENCES_I)
    		ensure -- from EV_WIDGET_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	pointer_button_release_item_actions: ACTION_SEQUENCE [TUPLE [INTEGER_32, INTEGER_32, INTEGER_32, EV_GRID_ITEM]]
    			-- Actions to be performed when a pointer release event is received by a grid.
    			-- Arguments (with names for clarity):
    			--
    			-- x_pos: INTEGER -- The x position of the release in grid virtual coordinates.
    			-- y_pos: INTEGER -- The y position of the release in grid virtual coordinates.
    			-- a_button: INTEGER -- The index of the released button.
    			-- item: EV_GRID_ITEM -- If the release occurred above an item, this is the pointed item, otherwise argument is set to `Void'.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)
    		ensure -- from EV_GRID_ACTION_SEQUENCES_I
    			result_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_WIDGET_ACTION_SEQUENCES_I)
    		ensure -- from EV_WIDGET_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	pointer_double_press_item_actions: ACTION_SEQUENCE [TUPLE [INTEGER_32, INTEGER_32, INTEGER_32, EV_GRID_ITEM]]
    			-- Actions to be performed when a pointer double press event is received by a grid.
    			-- Arguments (with names for clarity):
    			--
    			-- x_pos: INTEGER -- The x position of the double press in grid virtual coordinates.
    			-- y_pos: INTEGER -- The y position of the double press in grid virtual coordinates.
    			-- a_button: INTEGER -- The index of the pressed button.
    			-- item: EV_GRID_ITEM -- If the double press occurred above an item, this is the pointed item, otherwise argument is set to `Void'.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)
    		ensure -- from EV_GRID_ACTION_SEQUENCES_I
    			result_not_void: Result /= Void

    	pointer_enter_actions: EV_NOTIFY_ACTION_SEQUENCE
    			-- Actions to be performed when screen pointer enters widget.
    			-- (from EV_WIDGET_ACTION_SEQUENCES_I)
    		ensure -- from EV_WIDGET_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	pointer_enter_item_actions: ACTION_SEQUENCE [TUPLE [BOOLEAN, EV_GRID_ITEM]]
    			-- Actions to be performed when a pointer enter event is received by a grid or grid item
    			-- Arguments (with names for clarity):
    			--
    			-- on_grid: BOOLEAN -- Did the enter event occur for the grid?
    			-- item: EV_GRID_ITEM -- If the enter event occurred for an item, this is the item.
    			--
    			-- Note that `on_grid' may be set to `True' and item may be non-Void
    			-- in the case where the pointer enters a grid at a location where there
    			-- is an item contained.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)
    		ensure -- from EV_GRID_ACTION_SEQUENCES_I
    			result_not_void: Result /= Void

    	pointer_leave_actions: EV_NOTIFY_ACTION_SEQUENCE
    			-- Actions to be performed when screen pointer leaves widget.
    			-- (from EV_WIDGET_ACTION_SEQUENCES_I)
    		ensure -- from EV_WIDGET_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	pointer_leave_item_actions: ACTION_SEQUENCE [TUPLE [BOOLEAN, EV_GRID_ITEM]]
    			-- Actions to be performed when a pointer leave event is received by a grid or grid item
    			-- Arguments (with names for clarity):
    			--
    			-- on_grid: BOOLEAN -- Did the leave event occur for the grid?
    			-- item: EV_GRID_ITEM -- If the leave event occurred for an item, this is the item.
    			--
    			-- Note that `on_grid' may be set to `True' and item may be non-Void
    			-- in the case where the pointer leaves a grid from a location where there.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)
    		ensure -- from EV_GRID_ACTION_SEQUENCES_I
    			result_not_void: Result /= Void

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

    	pointer_motion_item_actions: ACTION_SEQUENCE [TUPLE [INTEGER_32, INTEGER_32, EV_GRID_ITEM]]
    			-- Actions to be performed when a screen pointer moves over a grid.
    			-- Arguments (with names for clarity):
    			--
    			-- x_pos: INTEGER -- The x position of the motion in grid virtual coordinates.
    			-- y_pos: INTEGER -- The y position of the motion in grid virtual coordinates.
    			-- item: EV_GRID_ITEM -- If the motion occurred above an item, this is the pointed item, otherwise argument is set to `Void'.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)
    		ensure -- from EV_GRID_ACTION_SEQUENCES_I
    			result_not_void: Result /= Void

    	post_draw_overlay_actions: ACTION_SEQUENCE [TUPLE [EV_DRAWABLE, EV_GRID_ITEM, INTEGER_32, INTEGER_32]]
    			-- Actions to be performed after an item cell in `Current'  has been drawn. The four pieces of event data are:
    			-- drawable: EV_DRAWABLE The drawable into which you may draw to overlay onto the already drawn item.
    			-- grid_item: EV_GRID_ITEM The item which has just been drawn, may be Void in the case that an
    			-- item cell is being drawn which does not contain an item.
    			-- a_column_index: INTEGER The column index of the grid cell that has just been drawn.
    			-- a_row_index: INTEGER The row index of the grid cell that has just been drawn.
    			-- This is useful for drawing additional border styles or other such effects. The upper left corner
    			-- of the item cell starts at coordinates 0x0 in the passed drawable. All drawing Performed
    			-- in the drawable is clipped to width of the column at `a_column_index' and height of row at `a_row_index'.
    			-- Note that the upper left corner of drawable corresponds to the upper left corner of the item
    			-- cell and not the actual items horizontal position within the cell which may be greater than 0 if
    			-- the item is within a tree structure. Use `horizontal_indent' of the item to determine this.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)
    		ensure -- from EV_GRID_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	pre_draw_overlay_actions: ACTION_SEQUENCE [TUPLE [EV_DRAWABLE, EV_GRID_ITEM, INTEGER_32, INTEGER_32]]
    			-- Actions to be performed before the features of an item cell in `Current' have been drawn but after the background of
    			-- the cell has been drawn. The four pieces of event data are:
    			-- drawable: EV_DRAWABLE The drawable into which you may draw to overlay onto the already drawn background.
    			-- grid_item: EV_GRID_ITEM The item which has just been drawn, may be Void in the case that an
    			-- item cell is being drawn which does not contain an item.
    			-- a_column_index: INTEGER The column index of the grid cell that has just been drawn.
    			-- a_row_index: INTEGER The row index of the grid cell that has just been drawn.
    			-- This is useful for drawing additional border styles or other such effects. The upper left corner
    			-- of the item cell starts at coordinates 0x0 in the passed drawable. All drawing Performed
    			-- in the drawable is clipped to width of the column at `a_column_index' and height of row at `a_row_index'.
    			-- Note that the upper left corner of drawable corresponds to the upper left corner of the item
    			-- cell and not the actual items horizontal position within the cell which may be greater than 0 if
    			-- the item is within a tree structure. Use `horizontal_indent' of the item to determine this.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)
    		ensure -- from EV_GRID_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	resize_actions: EV_GEOMETRY_ACTION_SEQUENCE
    			-- Actions to be performed when size changes.
    			-- (from EV_WIDGET_ACTION_SEQUENCES_I)
    		ensure -- from EV_WIDGET_ACTION_SEQUENCES_I
    			not_void: Result /= Void

    	row_collapse_actions: EV_GRID_ROW_ACTION_SEQUENCE
    			-- Actions to be performed when a row is collapsed.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)
    		ensure -- from EV_GRID_ACTION_SEQUENCES_I
    			result_not_void: Result /= Void

    	row_deselect_actions: EV_GRID_ROW_ACTION_SEQUENCE
    			-- Actions to be performed when a row is deselected.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)
    		ensure -- from EV_GRID_ACTION_SEQUENCES_I
    			result_not_void: Result /= Void

    	row_expand_actions: EV_GRID_ROW_ACTION_SEQUENCE
    			-- Actions to be performed when a row is expanded.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)
    		ensure -- from EV_GRID_ACTION_SEQUENCES_I
    			result_not_void: Result /= Void

    	row_select_actions: EV_GRID_ROW_ACTION_SEQUENCE
    			-- Actions to be performed when a row is selected.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)
    		ensure -- from EV_GRID_ACTION_SEQUENCES_I
    			result_not_void: Result /= Void

    	virtual_position_changed_actions: ACTION_SEQUENCE [TUPLE [INTEGER_32, INTEGER_32]]
    			-- Actions to be performed upon next idle after virtual_x_position or virtual_y_position changed in grid.
    			-- Arguments (with names for clarity)
    			--
    			-- a_virtual_x_position: INTEGER -- New virtual_x_position of grid.
    			-- a_virtual_y_position: INTEGER -- New virtual_y_position of grid.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)

    	virtual_size_changed_actions: ACTION_SEQUENCE [TUPLE [INTEGER_32, INTEGER_32]]
    			-- Actions to be performed upon next idle after virtual_width or virtual_height changed in grid.
    			-- Arguments (with names for clarity)
    			--
    			-- a_virtual_width: INTEGER -- New virtual_width of grid.
    			-- a_virtual_height: INTEGER -- New virtual_height of grid.
    			-- (from EV_GRID_ACTION_SEQUENCES_I)

    feature -- Markers

    	fixme (comment: STRING_8)
    			-- Mark code that has to be "fixed" with `comment'.
    			-- (from REFACTORING_HELPER)
    		require -- from REFACTORING_HELPER
    			comment_not_void: comment /= Void

    	to_implement (comment: STRING_8)
    			-- Mark code that has to be "implemented" with `comment'.
    			-- (from REFACTORING_HELPER)
    		require -- from REFACTORING_HELPER
    			comment_not_void: comment /= Void

    	to_implement_assertion (comment: STRING_8): BOOLEAN
    			-- Mark assertion that has to be "implemented" with `comment'.
    			-- (from REFACTORING_HELPER)
    		require -- from REFACTORING_HELPER
    			comment_not_void: comment /= Void

    feature -- Measurements

    	column_count: INTEGER_32
    			-- Number of columns in Current.

    	displayed_column_count: INTEGER_32
    			-- Number of non-hidden columns displayed in Current.
    			-- Equal to column_count if no columns have been
    			-- hidden via hide.

    	row_count: INTEGER_32
    			-- Number of rows in Current.

    	visible_row_count: INTEGER_32
    			-- Number of visible rows in `Current'. When is_tree_enabled,
    			-- a number of rows may be within a collapsed parent row, so these
    			-- are ignored

    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 -- Pick and Drop

    	are_column_separators_enabled: BOOLEAN
    			-- Is a vertical separator displayed in color separator_color after each column?

    	are_row_separators_enabled: BOOLEAN
    			-- Is a horizontal separator displayed in color separator_color after each row?

    	drop_action_intermediary (a_pebble: ANY)
    			-- A PND drop has occured on a grid item.

    	item_accept_cursor_function: FUNCTION [ANY, TUPLE [EV_GRID_ITEM], EV_POINTER_STYLE]
    			-- Function used to retrieve the PND accept cursor for a particular item.

    	item_accepts_pebble (a_item: EV_GRID_ITEM; a_pebble: ANY): BOOLEAN
    			-- Do any actions accept `a_pebble' for `a_item'.
    		require
    			a_pebble_not_void: a_pebble /= Void

    	item_deny_cursor_function: FUNCTION [ANY, TUPLE [EV_GRID_ITEM], EV_POINTER_STYLE]
    			-- Function used to retrieve the PND deny cursor for a particular item.

    	item_target: EV_GRID_ITEM
    			-- Item currently at pointer position.

    	item_veto_pebble_function: FUNCTION [ANY, TUPLE [EV_GRID_ITEM, ANY], BOOLEAN]
    			-- User item veto function.

    	separator_color: EV_COLOR
    			-- Color used to display column and row separators.

    	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.

    	set_deny_cursor (a_cursor: like deny_cursor)
    			-- Set `a_cursor' to be displayed when the screen pointer is over a
    			-- target that doesn't accept pebble during pick and drop.

    	set_item_accept_cursor_function (a_function: FUNCTION [ANY, TUPLE [EV_GRID_ITEM], EV_POINTER_STYLE])
    			-- Assign `a_function' to item_accept_cursor_function.
    		ensure
    			item_accept_cursor_function_set: item_accept_cursor_function = a_function

    	set_item_deny_cursor_function (a_function: FUNCTION [ANY, TUPLE [EV_GRID_ITEM], EV_POINTER_STYLE])
    			-- Assign `a_function' to item_deny_cursor_function.
    		ensure
    			item_deny_cursor_function_set: item_deny_cursor_function = a_function

    	set_item_pebble_function (a_function: FUNCTION [ANY, TUPLE [EV_GRID_ITEM], ANY])
    			-- Set `a_function' to compute pebble.
    			-- It will be called once each time a pick on the item area of the grid occurs, the result
    			-- will be assigned to pebble for the duration of transport.
    			-- When a pick occurs on an item, the item itself is passed.
    			-- If a pick occurs and no item is present, then Void is passed.
    			-- To handle this data use `a_function' of type
    			-- FUNCTION [ANY, TUPLE [EV_GRID_ITEM], ANY] and return the
    			-- pebble as a function of EV_GRID_ITEM.

    	set_item_veto_pebble_function (a_function: FUNCTION [ANY, TUPLE [EV_GRID_ITEM, ANY], BOOLEAN])
    			-- Assign `a_function' to item_veto_pebble_function.
    		ensure
    			item_veto_pebble_function_set: item_veto_pebble_function = a_function

    	user_pebble_function_intermediary (a_x, a_y: INTEGER_32): ANY
    			-- Intermediary function used for grid item pick and drop.

    	user_pebble_function_intermediary_locked (a_x, a_y: INTEGER_32; locked: EV_GRID_LOCKED_I): ANY
    			-- Intermediary function used for grid item pick and drop on the widgets comprising the locked columns and rows.

    	veto_pebble_function_intermediary (a_pebble: ANY): BOOLEAN
    			-- Intermediary function used for pebble vetoing.

    feature -- Platform

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

    feature -- Status Report

    	is_displayed: BOOLEAN
    			-- Is `Current' visible on the screen?
    			-- False if `Current' is entirely obscured by another window.
    			-- (from EV_WIDGET_I)

    	is_show_requested: BOOLEAN
    			-- Will `Current' be displayed when its parent is?
    			-- See also is_displayed.
    			-- (from EV_WIDGET_I)

    invariant
    	drawer_not_void: is_initialized implies drawer /= Void
    	drawable_not_void: is_initialized implies drawable /= Void
    	header_positioned_corrently: is_initialized implies header_viewport.x_offset >= 0 and header_viewport.y_offset = 0
    	internal_client_y_valid_while_vertical_scrollbar_hidden: is_initialized and then is_vertical_scroll_bar_show_requested and then not vertical_scroll_bar.is_show_requested implies internal_client_y = 0
    	internal_client_y_valid_while_vertical_scrollbar_shown: is_initialized and then vertical_scroll_bar.is_show_requested implies internal_client_y >= 0
    	internal_client_x_valid_while_horizontal_scrollbar_hidden: is_initialized and then is_horizontal_scroll_bar_show_requested and then not horizontal_scroll_bar.is_show_requested implies internal_client_x = 0
    	internal_client_x_valid_while_horizontal_scrollbar_shown: is_initialized and then horizontal_scroll_bar.is_show_requested implies internal_client_x >= 0
    	row_heights_fixed_implies_row_offsets_void: is_initialized and then not uses_row_offsets implies row_offsets = Void
    	row_lists_count_equal: is_initialized implies internal_row_data.count = rows.count
    	displayed_column_count_not_greater_than_column_count: is_initialized implies displayed_column_count <= column_count
    	computed_visible_row_count_equals_row_when_not_users_row_offsets: is_initialized and then not uses_row_offsets implies visible_row_count = row_count
    	computed_visible_row_count_no_greater_than_rows: is_initialized implies visible_row_count <= row_count
    	tree_disabled_implies_visible_rows_equal_hidden_rows: is_initialized and then not is_tree_enabled implies row_count - non_displayed_row_count = visible_row_count
    	internal_viewport_positions_equal_to_viewports: is_initialized implies (viewport.x_offset = viewport_x_offset and viewport.y_offset = viewport_y_offset)
    	tree_node_connector_color_not_void: is_initialized implies tree_node_connector_color /= Void

    		-- from EV_WIDGET_I
    	is_displayed_implies_show_requested: is_usable and is_displayed implies is_show_requested

    		-- from EV_PICK_AND_DROPABLE_I
    	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
    	pebble_function_takes_two_integer_open_operands: pebble_function /= Void implies pebble_function.valid_operands ([1, 1])

    		-- from EV_ANY_I
    	interface_coupled: is_usable implies interface /= Void and then interface.implementation = Current
    	base_make_called: base_make_called

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

    		-- from EV_DOCKABLE_SOURCE_I
    	widget_or_item_source: not (widget_source_being_docked /= Void and item_source_being_docked /= Void)
    	dock_executing: is_dock_executing implies widget_source_being_docked /= Void or item_source_being_docked /= Void

    		-- from EV_POSITIONED_I
    	minimum_width_positive_or_zero: is_usable implies minimum_width >= 0
    	minimum_height_positive_or_zero: is_usable implies minimum_height >= 0

    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_GRID_I