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Each actor managed by a BinLayout policy should reside inside its own "layer", with horizontal and vertical alignment. The :x-align and :y-align properties of the BinLayout are the default alignment policies, which are copied to each new "layer" when it is created. The set_alignment() and get_alignment() methods of BinLayout can be changed to operate on a specific "layer". The whole machinery uses the new ChildMeta support inside the LayoutManager base abstract class.