How can I set the default direction?

Hi,

A lot of arabic users don't know the RL/LR marks do even exist. They are 
used to set their given editor in LTR or RTL mode (namely R-CTRL+R-SHIFT 
in Notepad).

Apparently FriBidi takes the direction of the first character as the 
leading one.

Is there any way to tell log2vis what the default direction is without 
having to programmatically add the mark at the beginning of the string?

Thanks!