    indexing
    	description: "This class processes the scroll messages associated to a window."
    	legal: "See notice at end of class."
    	status: "See notice at end of class."
    	date: "$Date: 2006-09-21 17:04:32 -0700 (Thu, 21 Sep 2006) $"
    	revision: "$Revision: 63798 $"

    class interface
    	WEL_SCROLLER

    create
    	make (a_window: WEL_COMPOSITE_WINDOW; horizontal_size, vertical_size, line, page: INTEGER_32)
    			-- Make a scroller associated to `a_window' using
    			-- `horizontal_size' and `vertical_size' as the
    			-- size of the scrollable area. `line' and `page'
    			-- specify the scroll incrementation for a line and
    			-- a page.
    		require
    			a_window_not_void: a_window /= Void
    			a_window_exists: a_window.exists
    			positive_horizontal_size: horizontal_size > 0
    			positive_vertical_size: vertical_size > 0
    			positive_line: line >= 0
    			valid_line: line < horizontal_size and then line < vertical_size
    			positive_page: page >= 0
    			valid_page: page < horizontal_size and then page < vertical_size
    		ensure
    			window_set: window = a_window

    	make_with_options (a_window: WEL_COMPOSITE_WINDOW; a_minimal_horizontal_position, a_maximal_horizontal_position, a_minimal_vertical_position, a_maximal_vertical_position, a_horizontal_line, a_horizontal_page, a_vertical_line, a_vertical_page: INTEGER_32)
    			-- Make a scroller associated to `a_window'.
    			-- `a_minimal_horizontal_position' and
    			-- `a_maximal_horizontal_position' specify the
    			-- horizontal scroll range.
    			-- `a_minimal_vertical_position' and
    			-- `a_maximal_vertical_position' specify the
    			-- vertical scroll range.
    			-- `a_horizontal_line' and `a_horizontal_page' specify
    			-- the scroll incrementation for a horizontal line and
    			-- page.
    			-- `a_vertical_line' and `a_vertical_page' specify
    			-- the scroll incrementation for a vertical line and
    			-- page.
    		require
    			a_window_not_void: a_window /= Void
    			a_window_exists: a_window.exists
    			consistent_horizontal_range: a_minimal_horizontal_position < a_maximal_horizontal_position
    			consistent_vertical_range: a_minimal_vertical_position < a_maximal_vertical_position
    			positive_horizontal_line: a_horizontal_line >= 0
    			positive_vertical_line: a_vertical_line >= 0
    			positive_horizontal_page: a_horizontal_page >= 0
    			positive_vertical_page: a_vertical_page >= 0
    		ensure
    			window_set: window = a_window
    			minimal_horizontal_position_set: minimal_horizontal_position = a_minimal_horizontal_position
    			maximal_horizontal_position_set: maximal_horizontal_position = a_maximal_horizontal_position
    			minimal_vertical_position_set: minimal_vertical_position = a_minimal_vertical_position
    			maximal_vertical_position_set: maximal_vertical_position = a_maximal_vertical_position

    feature -- Initialization

    	make (a_window: WEL_COMPOSITE_WINDOW; horizontal_size, vertical_size, line, page: INTEGER_32)
    			-- Make a scroller associated to `a_window' using
    			-- `horizontal_size' and `vertical_size' as the
    			-- size of the scrollable area. `line' and `page'
    			-- specify the scroll incrementation for a line and
    			-- a page.
    		require
    			a_window_not_void: a_window /= Void
    			a_window_exists: a_window.exists
    			positive_horizontal_size: horizontal_size > 0
    			positive_vertical_size: vertical_size > 0
    			positive_line: line >= 0
    			valid_line: line < horizontal_size and then line < vertical_size
    			positive_page: page >= 0
    			valid_page: page < horizontal_size and then page < vertical_size
    		ensure
    			window_set: window = a_window

    	make_with_options (a_window: WEL_COMPOSITE_WINDOW; a_minimal_horizontal_position, a_maximal_horizontal_position, a_minimal_vertical_position, a_maximal_vertical_position, a_horizontal_line, a_horizontal_page, a_vertical_line, a_vertical_page: INTEGER_32)
    			-- Make a scroller associated to `a_window'.
    			-- `a_minimal_horizontal_position' and
    			-- `a_maximal_horizontal_position' specify the
    			-- horizontal scroll range.
    			-- `a_minimal_vertical_position' and
    			-- `a_maximal_vertical_position' specify the
    			-- vertical scroll range.
    			-- `a_horizontal_line' and `a_horizontal_page' specify
    			-- the scroll incrementation for a horizontal line and
    			-- page.
    			-- `a_vertical_line' and `a_vertical_page' specify
    			-- the scroll incrementation for a vertical line and
    			-- page.
    		require
    			a_window_not_void: a_window /= Void
    			a_window_exists: a_window.exists
    			consistent_horizontal_range: a_minimal_horizontal_position < a_maximal_horizontal_position
    			consistent_vertical_range: a_minimal_vertical_position < a_maximal_vertical_position
    			positive_horizontal_line: a_horizontal_line >= 0
    			positive_vertical_line: a_vertical_line >= 0
    			positive_horizontal_page: a_horizontal_page >= 0
    			positive_vertical_page: a_vertical_page >= 0
    		ensure
    			window_set: window = a_window
    			minimal_horizontal_position_set: minimal_horizontal_position = a_minimal_horizontal_position
    			maximal_horizontal_position_set: maximal_horizontal_position = a_maximal_horizontal_position
    			minimal_vertical_position_set: minimal_vertical_position = a_minimal_vertical_position
    			maximal_vertical_position_set: maximal_vertical_position = a_maximal_vertical_position

    feature -- Access

    	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)

    	horizontal_line: INTEGER_32
    			-- Number of horizontal scroll units per line

    	horizontal_page: INTEGER_32
    			-- Number of scroll units per page
    		require
    			window_exists: window.exists

    	horizontal_position: INTEGER_32
    			-- Current position of the horizontal scroll box
    		require
    			window_exists: window.exists

    	maximal_horizontal_position: INTEGER_32
    			-- Maxium position of the horizontal scroll box
    		require
    			window_exists: window.exists

    	maximal_vertical_position: INTEGER_32
    			-- Maxium position of the vertical scroll box
    		require
    			window_exists: window.exists

    	minimal_horizontal_position: INTEGER_32
    			-- Minimum position of the horizontal scroll box
    		require
    			window_exists: window.exists

    	minimal_vertical_position: INTEGER_32
    			-- Minimum position of the vertical scroll box
    		require
    			window_exists: window.exists

    	vertical_line: INTEGER_32
    			-- Number of vertical scroll units per line

    	vertical_page: INTEGER_32
    			-- Number of scroll units per page
    		require
    			window_exists: window.exists

    	vertical_position: INTEGER_32
    			-- Current position of the vertical scroll box
    		require
    			window_exists: window.exists

    	window: WEL_COMPOSITE_WINDOW
    			-- Window which has the scroller

    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

    	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

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

    	valid_maximal_horizontal_position (a_position: INTEGER_32): BOOLEAN
    			-- Is `a_position' valid for setting the horizontal_position.

    	valid_maximal_vertical_position (a_position: INTEGER_32): BOOLEAN
    			-- Is `a_position' valid for setting the vertical_position.

    feature -- Element change

    	set_horizontal_line (unit: INTEGER_32)
    			-- Set horizontal_line with `unit'.
    		require
    			positive_unit: unit >= 0
    		ensure
    			horizontal_line_set: horizontal_line = unit

    	set_horizontal_page (page_magnitude: INTEGER_32)
    			-- Set horizontal_page with `unit'.
    		require
    			window_exists: window.exists
    			positive_unit: page_magnitude >= 0
    		ensure
    			horizontal_page_set: horizontal_page = page_magnitude

    	set_horizontal_position (position: INTEGER_32)
    			-- Set horizontal_position with `position'.
    		require
    			window_exists: window.exists
    			position_small_enough: valid_maximal_horizontal_position (position)
    			position_large_enough: position >= minimal_horizontal_position
    		ensure
    			horizontal_position_set: horizontal_position = position

    	set_horizontal_range (minimum, maximum: INTEGER_32)
    			-- Set `horizontal_minimum_range' and
    			-- `horizontal_maximal_range' with `minimum' and
    			-- `maximum'.
    		require
    			window_exists: window.exists
    			consistent_range: minimum <= maximum
    		ensure
    			horizontal_minimum_range_set: minimal_horizontal_position = minimum
    			horizontal_maximal_range_set: maximal_horizontal_position = maximum

    	set_vertical_line (unit: INTEGER_32)
    			-- Set vertical_line with `unit'.
    		require
    			positive_unit: unit >= 0
    		ensure
    			vertical_line_set: vertical_line = unit

    	set_vertical_page (page_magnitude: INTEGER_32)
    			-- Set vertical_page with `unit'.
    		require
    			window_exists: window.exists
    			positive_unit: page_magnitude >= 0
    		ensure
    			vertical_page_set: vertical_page = page_magnitude

    	set_vertical_position (position: INTEGER_32)
    			-- Set vertical_position with `position'.
    		require
    			window_exists: window.exists
    			position_small_enough: valid_maximal_vertical_position (position)
    			position_large_enough: position >= minimal_vertical_position
    		ensure
    			vertical_position_set: vertical_position = position

    	set_vertical_range (minimum, maximum: INTEGER_32)
    			-- Set minimal_vertical_position and
    			-- maximal_vertical_position with `minimum' and
    			-- `maximum'.
    		require
    			window_exists: window.exists
    			consistent_range: minimum <= maximum
    		ensure
    			minimal_vertical_position_set: minimal_vertical_position = minimum
    			maximal_vertical_position_set: maximal_vertical_position = maximum

    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

    	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)

    	horizontal_update (inc, position: INTEGER_32)
    			-- Update the window and the horizontal scroll box with
    			-- `inc' and `position'.
    		require
    			window_exists: window.exists
    			position_small_enough: position <= maximal_horizontal_position
    			position_large_enough: position >= minimal_horizontal_position
    		ensure
    			horizontal_position_set: horizontal_position = position

    	on_horizontal_scroll (scroll_code, pos: INTEGER_32)
    			-- Scroll the window horizontaly.
    		require
    			window_exists: window.exists

    	on_vertical_scroll (scroll_code, pos: INTEGER_32)
    			-- Scroll the window verticaly.
    		require
    			window_exists: window.exists

    	vertical_update (inc, position: INTEGER_32)
    			-- Update the window and the vertical scroll box with
    			-- `inc' and `position'.
    		require
    			window_exists: window.exists
    			position_small_enough: position <= maximal_vertical_position
    			position_large_enough: position >= minimal_vertical_position
    		ensure
    			vertical_position_set: vertical_position = position

    feature -- Output

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

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

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

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

    feature -- Platform

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

    invariant
    	window_not_void: window /= Void
    	horizontal_position_small_enough: window.exists implies horizontal_position <= maximal_horizontal_position
    	horizontal_position_large_enough: window.exists implies horizontal_position >= minimal_horizontal_position
    	vertical_position_small_enough: window.exists implies vertical_position <= maximal_vertical_position
    	vertical_position_large_enough: window.exists implies vertical_position >= minimal_vertical_position
    	consistent_horizontal_range: window.exists implies minimal_horizontal_position <= maximal_horizontal_position
    	consistent_vertical_range: window.exists implies minimal_vertical_position <= maximal_vertical_position
    	positive_horizontal_line: horizontal_line >= 0
    	positive_vertical_line: vertical_line >= 0
    	positive_horizontal_page: horizontal_page >= 0
    	positive_vertical_page: vertical_page >= 0

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

    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 WEL_SCROLLER