{ if (viewport != null) remove(viewport);  viewport = v;  add(v);  revalidate(); repaint(); }
{ JViewport old = viewport; removeNonNull(old); viewport = v; addNonNull(v); revalidate(); repaint(); firePropertyChange(VIEWPORT_CHANGED_PROPERTY, old, v); sync(); }
    public void setViewport(JViewport v)    {	if (viewport != null)	    remove(viewport);	viewport = v;			add(v);		revalidate();	repaint();    }