Decorator (WIP)

A visual element that changes its appearance by listening specific events. It can has "pressed", "hover", "selected" or normal appearance:

Pressed - enables on mouse down message. Selected - whether decorator selected or not. Hovered - mouse is over decorator. Normal - not selected, pressed, hovered.

This element is widely used to provide some generic visual behaviour for various widgets. For example it used to decorate button, items in items control.