public void registerPropertyListeners() {
        DefaultView view = (DefaultView) app.getView();
        if (view.getActiveTab() != null) {
            Canvas activeCanvas = view.getActiveTab();
            PropertyChangeListener[] pcls = activeCanvas.getPropertyChangeListeners();
            for (PropertyChangeListener p : pcls) {
                if (p instanceof SavePropertyChangeListener) {
                    activeCanvas.removePropertyChangeListener(p);
                }
            }
            activeCanvas.addPropertyChangeListener(new SavePropertyChangeListener());
        }
    }