Layer.Layer

Specifies the window (an object of the Window class) that will own this layer.
Once the window is determined, it cannot be changed.

Specifies the layer that will be the parent of this layer. If null is specified, it will be the primary layer.
There can only be one primary layer in a window, and it is the parent layer of all layers that must exist when using layers.
However, some drawing devices (configurable in Window.drawDevice) allow windows to have multiple primary layers.
The parent of the layer can be changed with the Layer.parent property.