[HarfBuzz] vertical text for RTL scripts?

[Eli Zaretskii]

> From: Phil M Perry <philperry at hvc.rr.com>
> Date: Sun, 12 Jul 2020 10:15:31 -0400
> 
> Now, if I specify TTB direction, what should I see? Likewise, what 
> should BTT direction show? I know very little about RTL/bidi scripts, 
> and googling for examples gives ambiguous and conflicting information. I 
> realize that most scripts and languages are rarely written vertically, 
> except for East Asian (CJK) languages, but it would be nice to know that 
> the code is handling them correctly.
> 
> If you want to write Hebrew vertically, would you choose TTB or BBT? 

Hebrew is not written vertically, no more than English or German are.
So if you must write it vertically, I guess TTB would be the preferred
layout, like with Latin scripts.  For example, that's how
vertically-laid-out shop signs are made.