void onValueChanged(String ov, String nv) {
   String[] vs = (String[]) propertiesHash.get(nv);
   if (vs == null) vs = new String[0];
   String[] ovs = getSelectedProperties();
   if (ov != null && ovs != null) propertiesHash.put(ov, ovs);
   setSelectedProperties(vs);
   propertyListEditor.updateBar();
 }