protected void processMouseEvent(MouseEvent e)
	{
		if(e.getID() == MouseEvent.MOUSE_PRESSED)
		{
			if(e.getX() >= XLEN || e.getY() >= YLEN) return;
			point p = new point((double)e.getX()/XLEN,
					    (double)e.getY()/YLEN,
					    current_value);
			point_list.addElement(p);
			draw_point(p);
		}
	}