code: public void addListener(ILabelProviderListener listener)
  	{
  		if (fListeners == null)
  		{
  			fListeners = new ListenerList();
  		}
  		fListeners.add(listener);
  		if (fProblemChangedListener == null)
  		{
  			fProblemChangedListener = new IProblemChangedListener() {
  				public void problemsChanged(IResource[] changedResources,
  						boolean isMarkerChange)
  				{
  					fireProblemsChanged(changedResources, isMarkerChange);
  				}
  			};
  			VdmUIPlugin.getDefault()
  					.getProblemMarkerManager()
  					.addListener(fProblemChangedListener);
  		}
  	}
docs: /*
  (non-Javadoc)
  
  @see IBaseLabelProvider#addListener(ILabelProviderListener)