indexing
	description:
		"Curves as defined by two points, a `start_angle' and%N%
		%`aperture'."
	status: "See notice at end of class"
	keywords: "figure, arc, curve"
	date: "$Date$"
	revision: "$Revision$"

class
	EV_FIGURE_ARC

inherit
	EV_ATOMIC_FIGURE
		export
			{ANY} Pi
		redefine
			default_create
		end

	EV_DOUBLE_POINTED_FIGURE
		undefine
			default_create
		end

create
	default_create,
	make_with_points

feature {NONE} -- Initialization

	default_create is
			-- Create with some `start_angle' and `aperture'.
		do
			Precursor {EV_ATOMIC_FIGURE}
			start_angle := 0.2
			aperture := Pi
		end

feature -- Access

	start_angle: DOUBLE
			-- Angle that defines start of arc.

	aperture: DOUBLE
			-- Angle that defines percentage of arc.

feature -- Status setting

	set_start_angle (a_start_angle: DOUBLE) is
			-- Set `start_angle' to `a_start_angle'.
		require
			a_start_angle_within_bounds:
				a_start_angle >= 0 and a_start_angle <= 2 * Pi
		do
			start_angle := a_start_angle
		ensure
			start_angle_assigned: start_angle = a_start_angle
		end

	set_aperture (an_aperture: DOUBLE) is
			-- Set `aperture' to `an_aperture'.
		require
			an_aperture_within_bounds:
				an_aperture >= 0 and an_aperture <= 2 * Pi
		do
			aperture := an_aperture
		ensure
			aperture_assigned: aperture = an_aperture
		end

feature -- Events

	position_on_figure (x, y: INTEGER): BOOLEAN is
			-- Is (`x', `y') on this figure?
		local
			ay, ax, bx, by, cx, cy, top, left: INTEGER
			angle, end_angle: DOUBLE
			angle_inside: BOOLEAN
		do
			if aperture /= 0.0 then
				ax := point_a.x_abs
				ay := point_a.y_abs
				bx := point_b.x_abs
				by := point_b.y_abs
				left := ax.min (bx)
				top := ay.min (by)
				cx := left + (bx - ax).abs // 2
				cy := top + (by - ay).abs // 2
				angle := line_angle (x, y, cx, cy)
				end_angle := modulo (start_angle + aperture, 2 * Pi)
				if start_angle < end_angle then
					angle_inside := angle >= start_angle and angle <= end_angle
				else
					angle_inside := angle >= start_angle or angle <= end_angle
				end
				Result := point_on_ellipse_boundary (x, y, cx, cy, cx - left, cy - top, line_width ) and angle_inside
			else
				Result := False
			end	
		end

feature {EV_FIGURE_DRAWING_ROUTINES} -- Access

	metrics: TUPLE [INTEGER, INTEGER, INTEGER, INTEGER] is
			-- [`top_left_x', `top_left_y', `width', `height']
		local
			ay, ax, bx, by: INTEGER
		do
			ax := point_a.x_abs
			ay := point_a.y_abs
			bx := point_b.x_abs
			by := point_b.y_abs
			Result := [ax.min (bx), ay.min (by), (bx - ax).abs, (by - ay).abs]
		end

invariant
	start_angle_within_bounds: start_angle >= 0 and then start_angle <= 2 * Pi
	aperture_within_bounds: aperture >= 0 and then aperture <= 2 * Pi

end -- class EV_FIGURE_ARC

--|----------------------------------------------------------------
--| EiffelVision2: library of reusable components for ISE Eiffel.
--| Copyright (C) 1986-2001 Interactive Software Engineering Inc.
--| All rights reserved. Duplication and distribution prohibited.
--| May be used only with ISE Eiffel, under terms of user license. 
--| Contact ISE for any other use.
--|
--| Interactive Software Engineering Inc.
--| ISE Building
--| 360 Storke Road, Goleta, CA 93117 USA
--| Telephone 805-685-1006, Fax 805-685-6869
--| Electronic mail <info@eiffel.com>
--| Customer support: http://support.eiffel.com>
--| For latest info see award-winning pages: http://www.eiffel.com
--|----------------------------------------------------------------