indexing

	description: "[

		A wrapper / adaptor for a drawable to make it rotateable and zoomable.
		
		The position and size of such objects is defined through the transformed drawable.
		Changing the position of an EM_TRANSFORMER is possible (`set_x_y')
		but changing any of the transformation parameters will recalculate `Current's position.
		
		EM_TRANSFORMER should not be used to excessively because it uses a buffer to draw
		the drawable before rotating it. Especially when you only want to zoom and/or scroll
		your drawable, better use an EM_ZOOMABLE_CONTAINER.

	]"
	date: "$Date$"
	revision: "$Revision$"

class EM_TRANSFORMER

inherit

	EM_DRAWABLE

	DOUBLE_MATH

	EM_SHARED_SUBSYSTEMS
		export {NONE} all end

	EM_SHARED_BITMAP_FACTORY
		export {NONE} all end

create

	make_with_drawable

feature -- Initialization

	make_with_drawable (a_drawable: EM_DRAWABLE) is
			-- Initialize `Current' to transform `a_drawable' when drawing.
		do
			initialize_events

			drawable := a_drawable
			create rotation_center.make (drawable.width / 2, drawable.height / 2)
			zoom_factor := 1.0
			rotation_angle := 0
			if video_subsystem.video_surface /= Void then
				is_anti_aliasing_enabled := video_subsystem.video_surface.is_anti_aliasing_enabled
			else
				is_anti_aliasing_enabled := True
			end
			set_visible (True)
		ensure
			drawable_set: drawable = a_drawable
		end

feature -- Status report

	drawable: EM_DRAWABLE
			-- Drawable that is transformed

	zoom_factor: DOUBLE
			-- Zoom factor by which to zoom `drawable'

	rotation_center: EM_VECTOR_2D
			-- Rotation center relative to position of `drawable'

	rotation_angle: DOUBLE
			-- Rotation angle by which to rotate `drawable' around `rotation_center' (in degree)

	width: INTEGER
			-- Width of `Current'

	height: INTEGER
			-- Height of `Current'

	is_anti_aliasing_enabled: BOOLEAN
			-- Is the transformation done with anti aliasing?

feature -- Status setting

	set_drawable (a_drawable: EM_DRAWABLE) is
			-- Set `drawable' to `a_drawable'.
		require
			a_drawable_not_void: a_drawable /= Void
		do
			drawable := a_drawable
			update_bounding_box
		ensure
			drawable_set: drawable = a_drawable
		end

	set_zoom_factor (a_zoom_factor: DOUBLE) is
			-- Set `zoom_factor' to `a_zoom_factor'.
		require
			a_zoom_factor_positive: a_zoom_factor > 0
		do
			zoom_factor := a_zoom_factor
			update_bounding_box
		ensure
			zoom_factor_set: zoom_factor = a_zoom_factor
		end

	set_rotation_center (a_position: EM_VECTOR_2D) is
			-- Set `rotation_center' to `a_position'.
		require
			a_position_not_void: a_position /= Void
		do
			rotation_center := a_position
			update_bounding_box
		ensure
			rotation_center_set: rotation_center = a_position
		end

	set_rotation_angle (an_angle: DOUBLE) is
			-- Set `rotation_angle' to `an_angle' in degrees.
		do
			rotation_angle := an_angle
			update_bounding_box
		ensure
			rotation_angle_set: rotation_angle = an_angle
		end

	set_anti_aliasing_enabled (a_bool: BOOLEAN) is
			-- Set `is_anti_aliasing_enabled' to `a_bool'.
		do
			is_anti_aliasing_enabled := a_bool
		ensure
			is_anti_aliasing_enabled_set: is_anti_aliasing_enabled = a_bool
		end

	update_bounding_box is
			-- Calculate `bounding_box' where `Current' draws the transformed `drawable'.
		local
			bbox: EM_RECTANGLE
			p1, p2, p3, p4: EM_VECTOR_2D
			angle_in_rad: DOUBLE
			x1, y1, x2, y2: DOUBLE
		do
			bbox := drawable.bounding_box
			bbox.zoom (zoom_factor)

			-- Calculate rotated position.
			angle_in_rad := rotation_angle * Pi / 180
			p1 := bbox.upper_left.rotation (rotation_center, - angle_in_rad)
			p2 := bbox.upper_right.rotation (rotation_center, - angle_in_rad)
			p3 := bbox.lower_right.rotation (rotation_center, - angle_in_rad)
			p4 := bbox.lower_left.rotation (rotation_center, - angle_in_rad)

			-- Calculate and set bounding box.
			x1 := p1.x.min (p2.x).min (p3.x). min (p4.x)
			y1 := p1.y.min (p2.y).min (p3.y). min (p4.y)
			x2 := p1.x.max (p2.x).max (p3.x). max (p4.x)
			y2 := p1.y.max (p2.y).max (p3.y). max (p4.y)
			x := x1.floor
			y := y1.floor
			width := x2.ceiling - x
			height := y2.ceiling - y

		end

	draw (a_drawing_interface: EM_SURFACE) is
			-- Draw `Current' with `a_drawing_interface'.
		local
			zoomed_width: INTEGER
			zoomed_height: INTEGER
			transformed_drawable: EM_SURFACE -- buffer
		do
			if is_visible then

				-- Create a buffer with right width and height for zooming the drawable.
				zoomed_width := (drawable.width * zoom_factor).ceiling
				zoomed_height := (drawable.height * zoom_factor).ceiling
				Bitmap_factory.create_empty_surface (zoomed_width, zoomed_height)
				transformed_drawable := Bitmap_factory.last_surface
				transformed_drawable.set_anti_aliasing_enabled (is_anti_aliasing_enabled)

				-- Zoom the drawable (transform coordinates to draw it zoomed).
				transformed_drawable.transform_coordinates (drawable.bounding_box)
				drawable.draw (transformed_drawable)

				-- Rotate the zoomed buffer.
				if (rotation_angle.rounded \\ 360) /= 0 then
					transformed_drawable.rotate (rotation_angle)
				end

				-- Draw the transformed drawable at `Current's position.
				a_drawing_interface.blit_surface (transformed_drawable, x, y)
			end
		end

end