Description of problem:
Gtk internally uses the following check to decide whether to use RTL or LTR widgets direction:

  /* Translate to default:RTL if you want your widgets
   * to be RTL, otherwise translate to default:LTR.
   * Do *not* translate it to "predefinito:LTR", if it
   * it isn't default:LTR or default:RTL it will not work 
   */
    char *e = _("default:LTR");
    if (strcmp (e, "default:RTL")==0) 
      gtk_widget_set_default_direction (GTK_TEXT_DIR_RTL);
    else if (strcmp (e, "default:LTR"))
      g_warning ("Whoever translated default:LTR did so wrongly.\n");

However, if an external tool/library wants to decide whether Gtk would use RTL or LTR, it needs to do the same check, e.g. (in Python):

    xlated = gettext.ldgettext("gtk30", "default:LTR")
    if xlated == "default:LTR":
        Gtk.Widget.set_default_direction(Gtk.TextDirection.LTR)
    else:
        Gtk.Widget.set_default_direction(Gtk.TextDirection.RTL)

This is not a good solution as it depends on an internal implementation of the check used by the Gtk toolkit. If Gtk developers decide to change it or for example just change the particular string used for the check, such a solution will stop working.

Version-Release number of selected component (if applicable):
gtk3-3.9.14-1.fc20

Actual results:
No function providing information about the default widget direction exported by the Gtk library.

Expected results:
A function hiding the internal implementation.

Additional info:
I understand this information is quite rarely needed, but there are some applications that make use of it (e.g. the Anaconda installer).