decoration

The decoration this component paints through; Decoration.None until the library writes one.

Only the library writes it, on the event dispatch thread, and only with a value that differs from the one held. An implementation stores the value and does nothing else: after writing, the library repaints the component, and where the paint outsets changed, its Foundation parent fits its bounds around its layout bounds, and under any other parent the library revalidates it. A superclass constructor that repaints, as JPanel's does, runs before the implementation's own fields are set; such an implementation answers Decoration.None from a getter while no value is stored.