public function getEscapeSequencesByPath ( $dx = null, $dy = null ) {
        if ( is_null($dx) === true ) {
            $dx = $this->_currentPosition[0] - $this->_ancorPosition[0];
        }
        if ( is_null($dy) === true ) {
            $dy = $this->_currentPosition[1] - $this->_ancorPosition[1];
        }
        return self::getMovingEscapeSequences($dx, $dy);
    }