/**
* Sets the global document direction declaration. Default is left-to-right (ltr).
*
* @param string $dir The language direction to be set
*
* @return Document instance of $this to allow chaining
*
* @since 1.7.0
*/
public function setDirection($dir = 'ltr')
{
$this->direction = strtolower($dir);
return $this;
}