Returns collection of widget part names, that need to be repainted as a result of a property change.

Object's classifier.Child object that has changed, or null.Attribute that has changed.<h2>Dependencies</h2><div class="INSET">None</div> <h2>Behavior</h2> The default behavior returns <code>null,</code> so the widget is not repainted. If child is not <code>null,</code> attribute is an attribute of the child object, otherwise it's an attribute of the object.(c) SAP AG 2003-2006. All rights reserved.