# Sort `SpriteContext` by their `draw_order`
private class DrawOrderComparator
	super Comparator

	# This class can't set COMPARED because
	# `the public property cannot contain the private type...`
	#redef type COMPARED: SpriteContext

	# Require: `a isa SpriteContext and b isa SpriteContext`
	redef fun compare(a, b)
	do return a.as(SpriteContext).draw_order <=> b.as(SpriteContext).draw_order
end