[HarfBuzz] HarfBuzz shaping of R2L text

[Eli Zaretskii]

> Date: Thu, 30 May 2019 21:19:00 +0100
> From: Richard Wordingham <richard.wordingham at ntlworld.com>
> Cc: harfbuzz at lists.freedesktop.org
> 
> > I don't see any reordering here (with HarfBuzz), but maybe it's
> > because the only font I have that covers Myanmar is Code2000.
> 
> That's probably the problem.  I have Version 1.171 of the font, and the
> closest is comes to layout support for Myanmar is empty lists of
> lookups for undefined script "myan".  The script tag should be "mymr",
> so HarfBuzz applies no script-specific shaping.  There may be other
> issues, as changing "myan" to "mymr" doesn't fix the problem.

That figures, as Emacs by default claims there are no fonts on this
system that support Myanmar, and I need to force it use Code2000.

I will try with other fonts later.