draw a series of connected lines on the map, calling callback when done

def draw_lines(self, callback):
        '''draw a series of connected lines on the map, calling callback when done'''
        from MAVProxy.modules.mavproxy_map import mp_slipmap
        self.draw_callback = callback
        self.draw_line = []
        self.map.add_object(mp_slipmap.SlipDefaultPopup(None))