This example shows the importance of passing the reference of the positioned container. If your layer is nested in positioned element, then you must pass an id of or a reference to that element, because child elements of the positioned container will be placed according to its boundary.
Otherwise, Hider will not be located where it's supposed to be (like in first example below) and it would seem that WCH is doing nothing.
WCH is invoked with: WCH.Apply('al')
Positioned container
Child elements of the positioned container will be placed according to its boundary.
WCH is invoked with: WCH.Apply('al2', 'cont2')
Positioned container