1. 6.x includes/bootstrap.inc LANGUAGE_RTL
  2. 7.x includes/bootstrap.inc LANGUAGE_RTL

Language written right to left. Possible value of $language->direction.

3 uses of LANGUAGE_RTL
locale_languages_overview_form in includes/locale.inc
User interface for the language overview screen.
template_preprocess_book_export_html in modules/book/book.module
Process variables for book-export-html.tpl.php.
_locale_get_predefined_list in includes/locale.inc
Some of the common languages with their English and native names


includes/bootstrap.inc, line 214
Functions that need to be loaded on every Drupal request.


define('LANGUAGE_RTL', 1);