/** Override parent's behaviour by enabling start and end object observing */
 @Override
 public void setValidated(boolean validated) {
   super.setValidated(validated);
   if (!enabledStartObjectObserving) {
     enableStartObjectObserving(startObject);
   }
   if (!enabledEndObjectObserving) {
     enableEndObjectObserving(endObject);
   }
 }
 public void observeRelevantObjects() {
   enableStartObjectObserving(getStartObject());
   enableEndObjectObserving(getEndObject());
 }
 public final void setStartObject(ShapeGraphicalRepresentation<?> aStartObject) {
   startObject = aStartObject;
   if (!enabledStartObjectObserving) {
     enableStartObjectObserving(startObject);
   }
 }