    indexing
    	description: "EiffelVision screen, implementation interface."
    	legal: "See notice at end of class."
    	status: "See notice at end of class."
    	date: "$Date: 2006-01-22 18:25:44 -0800 (Sun, 22 Jan 2006) $"
    	revision: "$Revision: 56675 $"

    class interface
    	EV_SCREEN_IMP

    create
    	make (an_interface: like interface)
    			-- Create `Current', a screen object.
    		require -- from EV_ANY_I
    			an_interface_not_void: an_interface /= Void
    		ensure -- from EV_ANY_I
    			interface_assigned: interface = an_interface
    			base_make_called: base_make_called

    feature -- Access

    	arc_cosine (v: REAL_32): REAL_32
    			-- Trigonometric arccosine of `v'
    			-- (from SINGLE_MATH)

    	arc_sine (v: REAL_32): REAL_32
    			-- Trigonometric arcsine of `v'
    			-- (from SINGLE_MATH)

    	arc_tangent (v: REAL_32): REAL_32
    			-- Trigonometric arctangent of `v'
    			-- (from SINGLE_MATH)

    	background_color: EV_COLOR
    			-- Color used to fill figures.
    			-- (from EV_DRAWABLE_IMP)

    	ceiling (v: REAL_32): REAL_32
    			-- Least integral value greater than or equal to `v'
    			-- (from SINGLE_MATH)

    	check_instruction: INTEGER_32 is 7
    			-- Exception code for violated check
    			-- (from EXCEP_CONST)

    	class_invariant: INTEGER_32 is 6
    			-- Exception code for violated class invariant
    			-- (from EXCEP_CONST)

    	clip_area: EV_RECTANGLE
    			-- Clip area used to clip drawing.
    			-- If set to Void, no clipping is applied.
    			-- (from EV_DRAWABLE_IMP)

    	com_exception: INTEGER_32 is 28
    			-- Exception code for a COM error.
    			-- (from EXCEP_CONST)

    	cosine (v: REAL_32): REAL_32
    			-- Trigonometric cosine of radian `v' approximated
    			-- in the range [-pi/4, +pi/4]
    			-- (from SINGLE_MATH)

    	create_on_deferred: INTEGER_32 is 17
    			-- Create on deferred
    			-- (from EXCEP_CONST)

    	dashed_line_style: BOOLEAN
    			-- Are lines drawn dashed?
    			-- (from EV_DRAWABLE_IMP)

    	dc: WEL_SCREEN_DC
    			-- DC for drawing.

    	developer_exception: INTEGER_32 is 24
    			-- Exception code for developer exception
    			-- (from EXCEP_CONST)

    	dollar_applied_to_melted_feature: INTEGER_32 is 26
    			-- $ applied to melted feature
    			-- (from EXCEP_CONST)

    	drawing_mode: INTEGER_32
    			-- Logical operation on pixels when drawing.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from  EV_DRAWABLE_I
    			True

    	eiffel_runtime_fatal_error: INTEGER_32 is 25
    			-- Eiffel run-time fatal error
    			-- (from EXCEP_CONST)

    	eiffel_runtime_panic: INTEGER_32 is 13
    			-- Eiffel run-time panic
    			-- (from EXCEP_CONST)

    	euler: REAL_64 is 2.7182818284590452354
    			-- Logarithm base
    			-- (from MATH_CONST)

    	exception_in_signal_handler: INTEGER_32 is 20
    			-- Exception in signal handler
    			-- (from EXCEP_CONST)

    	external_exception: INTEGER_32 is 18
    			-- Exception code for operating system error
    			-- which does not set the `errno' variable
    			-- (Unix-specific)
    			-- (from EXCEP_CONST)

    	floating_point_exception: INTEGER_32 is 5
    			-- Exception code for floating point exception
    			-- (from EXCEP_CONST)

    	floor (v: REAL_32): REAL_32
    			-- Greatest integral value less than or equal to `v'
    			-- (from SINGLE_MATH)

    	font: EV_FONT
    			-- Font of `Current'.
    			-- (from EV_FONTABLE_IMP)
    		require -- from  EV_FONTABLE_I
    			True
    		ensure -- from EV_FONTABLE_I
    			not_void: Result /= Void

    	foreground_color: EV_COLOR
    			-- Color used for lines and text.
    			-- (from EV_DRAWABLE_IMP)

    	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)

    	incorrect_inspect_value: INTEGER_32 is 9
    			-- Exception code for inspect value which is not one
    			-- of the inspect constants, if there is no Else_part
    			-- (from EXCEP_CONST)

    	internal_font: EV_FONT
    			-- Font of `Current' for internal queries.
    			-- Faster than calling font as we do not need to
    			-- create a new EV_FONT every time.
    			-- (from EV_FONTABLE_IMP)

    	internal_font_height: INTEGER_32
    			-- Height required to correctly display font of `Current' in pixels.
    			-- (from EV_FONTABLE_IMP)
    		ensure -- from EV_FONTABLE_IMP
    			result_non_negative: Result >= 0

    	io_exception: INTEGER_32 is 21
    			-- Exception code for I/O error
    			-- (from EXCEP_CONST)

    	line_width: INTEGER_32
    			-- Line thickness.
    			-- (from EV_DRAWABLE_IMP)

    	log (v: REAL_32): REAL_32
    			-- Natural logarithm of `v'
    			-- (from SINGLE_MATH)
    		require -- from SINGLE_MATH
    			v > 0.0

    	log10 (v: REAL_32): REAL_32
    			-- Base 10 logarithm of `v'
    			-- (from SINGLE_MATH)
    		require -- from SINGLE_MATH
    			v > 0.0

    	log_2 (v: REAL_32): REAL_32
    			-- Base 2 logarithm of `v'
    			-- (from SINGLE_MATH)
    		require -- from SINGLE_MATH
    			v > 0.0

    	loop_invariant: INTEGER_32 is 11
    			-- Exception code for violated loop invariant
    			-- (from EXCEP_CONST)

    	loop_variant: INTEGER_32 is 10
    			-- Exception code for non-decreased loop variant
    			-- (from EXCEP_CONST)

    	no_more_memory: INTEGER_32 is 2
    			-- Exception code for failed memory allocation
    			-- (from EXCEP_CONST)

    	number_of_codes: INTEGER_32 is 29
    			-- How many codes are there to represent exceptions?
    			-- (from EXCEP_CONST)

    	operating_system_exception: INTEGER_32 is 22
    			-- Exception code for operating system error
    			-- which sets the `errno' variable
    			-- (Unix-specific)
    			-- (from EXCEP_CONST)

    	out_of_memory: INTEGER_32 is 15
    			-- Out of memory (cannot be ignored)
    			-- (from EXCEP_CONST)

    	pi: REAL_64 is 3.14159265358979323846
    			-- (from MATH_CONST)

    	postcondition: INTEGER_32 is 4
    			-- Exception code for violated postcondition
    			-- (from EXCEP_CONST)

    	precondition: INTEGER_32 is 3
    			-- Exception code for violated precondition
    			-- (from EXCEP_CONST)

    	rescue_exception: INTEGER_32 is 14
    			-- Exception code for exception in rescue clause
    			-- (from EXCEP_CONST)

    	resumption_failed: INTEGER_32 is 16
    			-- Resumption failed (retry did not succeed)
    			-- (from EXCEP_CONST)

    	retrieve_exception: INTEGER_32 is 23
    			-- Exception code for retrieval error
    			-- may be raised by `retrieved' in `IO_MEDIUM'.
    			-- (from EXCEP_CONST)

    	routine_failure: INTEGER_32 is 8
    			-- Exception code for failed routine
    			-- (from EXCEP_CONST)

    	runtime_check_exception: INTEGER_32 is 29
    			-- Exception code for runtime check being violated.
    			-- (from EXCEP_CONST)

    	runtime_io_exception: INTEGER_32 is 27
    			-- Exception code for I/O error raised by runtime functions
    			-- such as store/retrieve, file access...
    			-- (from EXCEP_CONST)

    	signal_exception: INTEGER_32 is 12
    			-- Exception code for operating system signal
    			-- (from EXCEP_CONST)

    	sine (v: REAL_32): REAL_32
    			-- Trigonometric sine of radian `v' approximated
    			-- in range [-pi/4, +pi/4]
    			-- (from SINGLE_MATH)

    	sqrt (v: REAL_32): REAL_32
    			-- Square root of `v'
    			-- (from SINGLE_MATH)
    		require -- from SINGLE_MATH
    			v >= 0.0

    	sqrt2: REAL_64 is 1.41421356237309504880
    			-- Square root of 2
    			-- (from MATH_CONST)

    	sub_pixmap (area: EV_RECTANGLE): EV_PIXMAP
    			-- Return the subpixmap of `Current' described by rectangle `area'.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			area_not_void: area /= Void
    		ensure -- from EV_DRAWABLE_I
    			result_not_void: Result /= Void

    	tangent (v: REAL_32): REAL_32
    			-- Trigonometric tangent of radian `v' approximated
    			-- in range [-pi/4, +pi/4]
    			-- (from SINGLE_MATH)

    	tile: EV_PIXMAP
    			-- Pixmap that is used to instead of background_color.
    			-- If set to Void, background_color is used to fill.
    			-- (from EV_DRAWABLE_IMP)

    	valid_code (c: INTEGER_32): BOOLEAN
    			-- Is `c' a valid code to represent some kind of exceptions?
    			-- (from EXCEP_CONST)

    	void_assigned_to_expanded: INTEGER_32 is 19
    			-- Exception code for assignment of void value
    			-- to expanded entity
    			-- (from EXCEP_CONST)

    	void_call_target: INTEGER_32 is 1
    			-- Exception code for feature applied to void reference
    			-- (from EXCEP_CONST)

    feature -- Measurement

    	height: INTEGER_32
    			-- Height of `Current'.
    		require -- from  EV_DRAWABLE_I
    			True
    		ensure -- from EV_DRAWABLE_I
    			positive: Result > 0

    	horizontal_resolution: INTEGER_32
    			-- Number of pixels per inch along screen width.
    		ensure -- from EV_SCREEN_I
    			positive: Result > 0

    	redraw
    			-- Force screen to redraw itself.

    	vertical_resolution: INTEGER_32
    			-- Number of pixels per inch along screen height.
    		ensure -- from EV_SCREEN_I
    			positive: Result > 0

    	virtual_height: INTEGER_32
    			-- Virtual height of `Current'

    	virtual_width: INTEGER_32
    			-- Virtual width of `Current'

    	virtual_x: INTEGER_32
    			-- X position of virtual screen in main display coordinates

    	virtual_y: INTEGER_32
    			-- Y position of virtual screen in main display coordinates

    	width: INTEGER_32
    			-- Width of `Current'.
    		require -- from  EV_DRAWABLE_I
    			True
    		ensure -- from EV_DRAWABLE_I
    			positive: Result > 0

    feature -- Comparison

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

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

    	is_equal (other: like Current): BOOLEAN
    			-- 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

    	assertion_violation: BOOLEAN
    			-- Is last exception originally due to a violated
    			-- assertion or non-decreasing variant?
    			-- (from EXCEPTIONS)

    	exception_class_name: STRING_8
    			-- Name of the class that includes the recipient
    			-- of original form of last exception
    			-- (from EXCEPTIONS)

    	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

    	destroyed: BOOLEAN
    			-- Is `Current' destroyed?

    	developer_exception_name: STRING_8
    			-- Name of last developer-raised exception
    			-- (from EXCEPTIONS)
    		require -- from EXCEPTIONS
    			applicable: is_developer_exception

    	exception: INTEGER_32
    			-- Code of last exception that occurred
    			-- (from EXCEPTIONS)

    	exception_trace: STRING_8
    			-- String representation of the exception trace
    			-- (from EXCEPTIONS)

    	is_developer_exception: BOOLEAN
    			-- Is the last exception originally due to
    			-- a developer exception?
    			-- (from EXCEPTIONS)

    	is_developer_exception_of_name (name: STRING_8): BOOLEAN
    			-- Is the last exception originally due to a developer
    			-- exception of name `name'?
    			-- (from EXCEPTIONS)

    	is_signal: BOOLEAN
    			-- Is last exception originally due to an external
    			-- event (operating system signal)?
    			-- (from EXCEPTIONS)

    	is_system_exception: BOOLEAN
    			-- Is last exception originally due to an
    			-- external event (operating system error)?
    			-- (from EXCEPTIONS)

    	meaning (except: INTEGER_32): STRING_8
    			-- A message in English describing what `except' is
    			-- (from EXCEPTIONS)

    	original_class_name: STRING_8
    			-- Name of the class that includes the recipient
    			-- of original form of last exception
    			-- (from EXCEPTIONS)

    	original_exception: INTEGER_32
    			-- Original code of last exception that triggered
    			-- current exception
    			-- (from EXCEPTIONS)

    	original_recipient_name: STRING_8
    			-- Name of the routine whose execution was
    			-- interrupted by original form of last exception
    			-- (from EXCEPTIONS)

    	original_tag_name: STRING_8
    			-- Assertion tag for original form of last
    			-- assertion violation.
    			-- (from EXCEPTIONS)

    	pointer_position: EV_COORDINATE
    			-- Position of the screen pointer.

    	recipient_name: STRING_8
    			-- Name of the routine whose execution was
    			-- interrupted by last exception
    			-- (from EXCEPTIONS)

    	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))

    	tag_name: STRING_8
    			-- Tag of last violated assertion clause
    			-- (from EXCEPTIONS)

    	widget_at_mouse_pointer: EV_WIDGET
    			-- Widget at mouse pointer if any.
    			-- (from EV_SCREEN_I)

    	widget_at_position (x, y: INTEGER_32): EV_WIDGET
    			-- Widget at position (`x', `y') if any.

    feature -- Status setting

    	catch (code: INTEGER_32)
    			-- Make sure that any exception of code `code' will be
    			-- caught. This is the default.
    			-- (from EXCEPTIONS)

    	destroy
    			-- Destroy actual object.
    		require -- from  EV_ANY_I
    			True
    		ensure -- from EV_ANY_I
    			is_in_destroy_set: is_in_destroy
    			is_destroyed_set: is_destroyed

    	die (code: INTEGER_32)
    			-- Terminate execution with exit status `code',
    			-- without triggering an exception.
    			-- (from EXCEPTIONS)

    	ignore (code: INTEGER_32)
    			-- Make sure that any exception of code `code' will be
    			-- ignored. This is not the default.
    			-- (from EXCEPTIONS)

    	message_on_failure
    			-- Print an exception history table
    			-- in case of failure.
    			-- This is the default.
    			-- (from EXCEPTIONS)

    	no_message_on_failure
    			-- Do not print an exception history table
    			-- in case of failure.
    			-- (from EXCEPTIONS)

    	exception_raise (name: STRING_8)
    			-- Raise a developer exception of name `name'.
    			-- (from EXCEPTIONS)

    	raise_retrieval_exception (name: STRING_8)
    			-- Raise a retrieval exception of name `name'.
    			-- (from EXCEPTIONS)

    	set_default_font
    			-- Make system to use default font.
    			-- (from EV_FONTABLE_IMP)

    feature -- Element change

    	disable_dashed_line_style
    			-- Draw lines solid.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from  EV_DRAWABLE_I
    			True
    		ensure -- from EV_DRAWABLE_I
    			dashed_line_style_disabled: is_usable implies not interface.dashed_line_style

    	enable_dashed_line_style
    			-- Draw lines dashed.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from  EV_DRAWABLE_I
    			True
    		ensure -- from EV_DRAWABLE_I
    			dashed_line_style_enabled: is_usable implies interface.dashed_line_style

    	remove_clipping
    			-- Do not apply any clipping.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from  EV_DRAWABLE_I
    			True
    		ensure -- from EV_DRAWABLE_I
    			clip_area_void: is_usable implies interface.clip_area = Void

    	remove_tile
    			-- Do not apply a tile when filling.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from  EV_DRAWABLE_I
    			True
    		ensure -- from EV_DRAWABLE_I
    			tile_void: is_usable implies interface.tile = Void

    	set_background_color (a_color: EV_COLOR)
    			-- Assign `a_color' to background_color.
    			-- (from EV_DRAWABLE_IMP)
    		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_clip_area (an_area: EV_RECTANGLE)
    			-- Set an area to clip to.
    			-- Set to Void when no clipping should be applied.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			an_area_not_void: an_area /= Void
    		ensure -- from EV_DRAWABLE_I
    			clip_area_assigned: is_usable implies interface.clip_area.is_equal (an_area)

    	set_clip_region (a_region: EV_REGION)
    			-- Set an area to clip to.
    			-- Set to Void when no clipping should be applied.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			a_region_not_void: a_region /= Void

    	set_drawing_mode (a_mode: INTEGER_32)
    			-- Set drawing mode to `a_mode'.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			a_mode_valid: valid_drawing_mode (a_mode)
    		ensure -- from EV_DRAWABLE_I
    			drawing_mode_assigned: is_usable implies interface.drawing_mode = a_mode

    	set_font (a_font: EV_FONT)
    			-- Set font to `a_font'.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_FONTABLE_I
    			a_font_not_void: a_font /= Void
    		ensure -- from EV_FONTABLE_I
    			assigned: is_usable implies font.is_equal (a_font)

    	set_foreground_color (a_color: EV_COLOR)
    			-- Assign `a_color' to foreground_color
    			-- (from EV_DRAWABLE_IMP)
    		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_line_width (a_width: INTEGER_32)
    			-- Assign `a_width' to line_width.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			a_width_positive_or_zero: a_width >= 0
    		ensure -- from EV_DRAWABLE_I
    			line_width_assigned: is_usable implies interface.line_width = a_width

    	set_tile (a_pixmap: EV_PIXMAP)
    			-- Set tile used to fill figures.
    			-- Set to Void to use background_color to fill.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			a_pixmap_not_void: a_pixmap /= Void
    		ensure -- from EV_DRAWABLE_I
    			tile_assigned: is_usable implies interface.tile /= Void

    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)

    feature -- Implementation

    	interface: EV_SCREEN

    feature -- Basic operation

    	fake_key_press (a_key: EV_KEY)
    			-- Simulate the user pressing `a_key'.

    	fake_key_release (a_key: EV_KEY)
    			-- Simulate the user releasing `a_key'.

    	fake_pointer_button_press (a_button: INTEGER_32)
    			-- Simulate the user pressing a `a_button'
    			-- on the pointing device.

    	fake_pointer_button_release (a_button: INTEGER_32)
    			-- Simulate the user releasing a `a_button'
    			-- on the pointing device.

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

    	set_pointer_position (x, y: INTEGER_32)
    			-- Set pointer_position to (`x',`y`).

    feature -- Clearing and drawing operations

    	clear
    			-- Erase `Current' with background_color.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from  EV_DRAWABLE_I
    			True

    	clear_rectangle (x1, y1, a_width, a_height: INTEGER_32)
    			-- Draw rectangle with upper-left corner on (`x', `y')
    			-- with size `a_width' and `a_height' in background_color.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from  EV_DRAWABLE_I
    			True

    feature -- Constants

    	drawing_mode_and: INTEGER_32 is 3
    			-- Drawing mode where bitwise AND is performed when a
    			-- pixel is drawn.
    			--
    			-- T\S | 0 | 1 |
    			-- -------------
    			--   0 | 0 | 0 |
    			-- -------------
    			--   1 | 0 | 1 |
    			-- (from EV_DRAWABLE_CONSTANTS)

    	drawing_mode_copy: INTEGER_32 is 0
    			-- Normal drawing mode.
    			--
    			-- T\S | 0 | 1 |
    			-- -------------
    			--   0 | 0 | 1 |
    			-- -------------
    			--   1 | 0 | 1 |
    			-- (from EV_DRAWABLE_CONSTANTS)

    	drawing_mode_invert: INTEGER_32 is 2
    			-- Drawing mode where bits are inverted before drawn.
    			--
    			-- T\S | 0 | 1 |
    			-- -------------
    			--   0 | 1 | 0 |
    			-- -------------
    			--   1 | 1 | 0 |
    			-- (from EV_DRAWABLE_CONSTANTS)

    	drawing_mode_or: INTEGER_32 is 4
    			-- Drawing mode where bitwise OR is performed when a
    			-- pixel is drawn.
    			--
    			-- T\S | 0 | 1 |
    			-- -------------
    			--   0 | 0 | 1 |
    			-- -------------
    			--   1 | 1 | 1 |
    			-- (from EV_DRAWABLE_CONSTANTS)

    	drawing_mode_xor: INTEGER_32 is 1
    			-- Drawing mode where bitwise XOR is performed when a
    			-- pixel is drawn.
    			--
    			-- T\S | 0 | 1 |
    			-- -------------
    			--   0 | 0 | 1 |
    			-- -------------
    			--   1 | 1 | 0 |
    			-- (from EV_DRAWABLE_CONSTANTS)

    feature -- Contract support

    	valid_drawing_mode (a_mode: INTEGER_32): BOOLEAN
    			-- Is `a_mode' a valid drawing mode?
    			-- (from EV_DRAWABLE_CONSTANTS)

    feature -- Drawing operations

    	bounding_area: EV_RECTANGLE
    			-- Temporary rectangle used internally.
    			-- (from EV_DRAWABLE_IMP)

    	draw_arc (x, y: INTEGER_32; a_bounding_width, a_bounding_height: INTEGER_32; a_start_angle, an_aperture: REAL_32)
    			-- Draw part of an ellipse defined by a rectangular area with an
    			-- upper left corner at `x',`y', width `a_bounding_width' and height
    			-- `a_bounding_height'.
    			-- Start at `a_start_angle' and stop at `a_start_angle' + `an_aperture'.
    			-- Angles are measured in radians, and go
    			-- counterclockwise from the 3 o'clock angle.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			a_bounding_width_positive_or_zero: a_bounding_width >= 0
    			a_bounding_width_positive_or_zero: a_bounding_height >= 0

    	draw_ellipse (x, y, a_bounding_width, a_bounding_height: INTEGER_32)
    			-- Draw an ellipse defined by a rectangular area with an
    			-- upper left corner at `x',`y', width `a_bounding_width' and height
    			-- `a_bounding_height'.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			a_bounding_width_positive_or_zero: a_bounding_width >= 0
    			a_bounding_height_positive_or_zero: a_bounding_height >= 0

    	draw_ellipsed_text (x, y: INTEGER_32; a_text: STRING_GENERAL; clipping_width: INTEGER_32)
    			-- Draw `a_text' with left of baseline at (`x', `y') using font.
    			-- Text is clipped to `clipping_width' in pixels and ellipses are displayed
    			-- to show truncated characters if any.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			a_text_not_void: a_text /= Void
    			clipping_width_positive: clipping_width >= 0

    	draw_ellipsed_text_top_left (x, y: INTEGER_32; a_text: STRING_GENERAL; clipping_width: INTEGER_32)
    			-- Draw `a_text' with top left corner at (`x', `y') using font.
    			-- Text is clipped to `clipping_width' in pixels and ellipses are displayed
    			-- to show truncated characters if any.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			a_text_not_void: a_text /= Void
    			clipping_width_positive: clipping_width >= 0

    	draw_pie_slice (x, y: INTEGER_32; a_bounding_width, a_bounding_height: INTEGER_32; a_start_angle, an_aperture: REAL_32)
    			-- Draw part of an ellipse defined by a rectangular area with an
    			-- upper left corner at `x',`y', width `a_bounding_width' and height
    			-- `a_bounding_height'.
    			-- Start at `a_start_angle' and stop at `a_start_angle' + `an_aperture'.
    			-- The arc is then closed by two segments through (`x', 'y').
    			-- Angles are measured in radians, start at the
    			-- 3 o'clock angle and grow counterclockwise.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			a_bounding_width_positive_or_zero: a_bounding_width >= 0
    			a_bounding_height_positive_or_zero: a_bounding_height >= 0

    	draw_pixmap (x, y: INTEGER_32; a_pixmap: EV_PIXMAP)
    			-- Draw `a_pixmap' with upper-left corner on (`x', `y').
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			a_pixmap_not_void: a_pixmap /= Void

    	draw_point (x, y: INTEGER_32)
    			-- Draw point at (`x', `y').
    			-- (from EV_DRAWABLE_IMP)
    		require -- from  EV_DRAWABLE_I
    			True

    	draw_polyline (points: ARRAY [EV_COORDINATE]; is_closed: BOOLEAN)
    			-- Draw line segments between subsequent points in
    			-- `points'. If `is_closed' draw line segment between first
    			-- and last point in `points'.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			points_not_void: points /= Void

    	draw_rectangle (x, y, a_width, a_height: INTEGER_32)
    			-- Draw rectangle with upper-left corner on (`x', `y')
    			-- with size `a_width' and `a_height'.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			a_width_positive_or_zero: a_width >= 0
    			a_height_positive_or_zero: a_height >= 0

    	draw_rotated_text (x, y: INTEGER_32; a_angle: REAL_32; a_text: STRING_GENERAL)
    			-- Draw rotated text `a_text' with left of baseline at (`x', `y') using font.
    			-- Rotation is number of radians counter-clockwise from horizontal plane.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			a_text_not_void: a_text /= Void

    	draw_segment (x1, y1, x2, y2: INTEGER_32)
    			-- Draw line segment from (`x1', 'y1') to (`x2', 'y2').
    			-- (from EV_DRAWABLE_IMP)
    		require -- from  EV_DRAWABLE_I
    			True

    	draw_straight_line (x1, y1, x2, y2: INTEGER_32)
    			-- Draw infinite straight line through (`x1','y1') and (`x2','y2').
    			-- (from EV_DRAWABLE_I)

    	draw_sub_pixmap (x, y: INTEGER_32; a_pixmap: EV_PIXMAP; area: EV_RECTANGLE)
    			-- Draw `area' of `a_pixmap' with upper-left corner on (`x', `y').
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			a_pixmap_not_void: a_pixmap /= Void
    			area_not_void: area /= Void

    	draw_text (x, y: INTEGER_32; a_text: STRING_GENERAL)
    			-- Draw `a_text' with left of baseline at (`x', `y') using font.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			a_text_not_void: a_text /= Void

    	draw_text_top_left (x, y: INTEGER_32; a_text: STRING_GENERAL)
    			-- Draw `a_text' with top left corner at (`x', `y') using font.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			a_text_not_void: a_text /= Void

    	internal_draw_text (x, y: INTEGER_32; angle: REAL_32; clipping_width: INTEGER_32; from_baseline: BOOLEAN; a_text: STRING_GENERAL)
    			-- Draw `a_text' with top left corner at (`x', `y') using font.
    			-- Text is clipped to `clipping_width' in pixels and ellipses are displayed
    			-- to show truncated characters if any.
    			-- Text is rotated counter-clockwise from the horizontal axis `degrees' degrees.
    			-- (from EV_DRAWABLE_IMP)

    feature -- Filling operations

    	fill_ellipse (x, y, a_bounding_width, a_bounding_height: INTEGER_32)
    			-- Fill an ellipse defined by a rectangular area with an
    			-- upper left corner at `x',`y', width `a_bounding_width' and height
    			-- `a_bounding_height'.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			a_bounding_width_positive_or_zero: a_bounding_width >= 0
    			a_bounding_height_positive_or_zero: a_bounding_height >= 0

    	fill_pie_slice (x, y: INTEGER_32; a_bounding_width, a_bounding_height: INTEGER_32; a_start_angle, an_aperture: REAL_32)
    			-- Fill part of an ellipse defined by a rectangular area with an
    			-- upper left corner at `x',`y', width `a_bounding_width' and height
    			-- `a_bounding_height'.
    			-- Start at `a_start_angle' and stop at `a_start_angle' + `an_aperture'.
    			-- The arc is then closed by two segments through (`x', 'y').
    			-- Angles are measured in radians, start at the 3
    			-- o'clock angle and grow counterclockwise.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			a_bounding_width_positive_or_zero: a_bounding_width >= 0
    			a_bounding_height_positive_or_zero: a_bounding_height >= 0

    	fill_polygon (points: ARRAY [EV_COORDINATE])
    			-- Draw line segments between subsequent points in `points'.
    			-- Fill all enclosed area's with foreground_color.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			points_not_void: points /= Void

    	fill_rectangle (x, y, a_width, a_height: INTEGER_32)
    			-- Draw rectangle with upper-left corner on (`x', `y')
    			-- with size `a_width' and `a_height'. Fill with foreground_color.
    			-- (from EV_DRAWABLE_IMP)
    		require -- from EV_DRAWABLE_I
    			a_width_positive_or_zero: a_width >= 0
    			a_height_positive_or_zero: a_height >= 0

    feature -- Output

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

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

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

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

    feature -- Platform

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

    feature --EV_ANY_I -- Implementation

    	get_dc
    			-- Get dc.
    			-- By default does nothing, but is
    			-- redefined by primitives that do not keep a consistent
    			-- dc. Example : EV_DRAWING_AREA_IMP
    			-- (from EV_DRAWABLE_IMP)

    	release_dc
    			-- Release dc.
    			-- By default does nothing, but is
    			-- redefined by primitives that do not keep a consistent
    			-- dc. Example : EV_DRAWING_AREA_IMP
    			-- (from EV_DRAWABLE_IMP)

    invariant
    	dc_not_void: dc /= Void

    		-- 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_DRAWABLE_IMP
    	reference_tracked_on_brush: internal_brush /= Void implies internal_brush.reference_tracked
    	brush_exists: internal_brush /= Void implies internal_brush.exists
    	reference_tracked_on_pen: internal_pen /= Void implies internal_pen.reference_tracked

    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_SCREEN_IMP