# Draw a specific sprite on the view
	#
	# This method must be implemented for each specific view.
	# A traditional way of implementation is to use a double-dispatch mechanism
	#
	#     class MyView
	#         super View
	#         redef fun draw_sprite(s) do s.draw_on_myview(self)
	#     end
	#     redef class Sprite
	#         # How to draw a sprite on my specific view
	#         fun draw_on_myview(myview: MyView) is abstract
	#     end
	fun draw_sprite(s: Sprite) is abstract