public function paint(c:Component, g:Graphics, r:Rectangle):VoidDescription copied from ComponentUI
 Notifies this UI delegate that it's time to paint the specified
 component.  This method is invoked by Component 
 when the specified component is being painted.
 
In general this method need be overridden by subclasses; all look-and-feel rendering code should reside in this method. And there is a default background paint method, you should call it in your overridden paint method.