Test token for text direction?

Hi,

I wonder if there is a possibility to test the text direction 
(left-to-right or right-to-left), at least I haven't found anything.

I am documenting keyboard shortcuts containing "Left" and "Right" keys 
(arrows). They have a different meaning in ltr and in rtl (going back 
vs. going forward). It's a GTK+ app and in GTK+ there is a 
GtkShortcutsWindow which is capable of doing that, I was looking for 
something similar in Mallard. GtkShortcutsShortcuts have a "direction" 
property which makes the shortcut only appear if it matches the direction.

Thanks,
Gabor