protected function setBackgroundPositionProperty( $value, $priority = self::PRIORITY_NORMAL )
    {
        $parts = preg_split( '/\s+/', trim( $value ), 2 );
        $this->setRawProperty( 'background-position', $value, $priority );

        if ( count( $parts ) < 2 )
        {
            return $this;
        }

        list( $x, $y ) = $parts;
        return $this->setRawProperty( 'background-position-x', $x, $priority )
                    ->setRawProperty( 'background-position-y', $y, $priority );
    }