Paints the specified component appropriately for the look and feel.
This method is invoked from the ComponentUI.update method when
the specified component is being painted. Subclasses should override
this method and use the specified Graphics object to
render the content of the component.
Returns the specified component's preferred size appropriate for
the look and feel. If null is returned, the preferred
size will be calculated by the component's layout manager instead
(this is the preferred approach for any component with a specific
layout manager installed). The default implementation of this
method returns null.
c - the component whose preferred size is being queried;
this argument is often ignored,
but might be used if the UI object is stateless
and shared by multiple components
Returns:
a Dimension object containing given component's preferred
size appropriate for the look and feel