switch (ev.getType()) {
case ADD :
// Add room to its group at the index indicated by the event
// to ensure the 3D rooms are drawn in the same order as in the plan
addObject(group, room, ev.getIndex(), true, false);
room.addPropertyChangeListener(roomChangeListener);
break;
case DELETE :
deleteObject(room);
room.removePropertyChangeListener(roomChangeListener);
break;