[HarfBuzz] HarfBuzz shaping of R2L text

[Eli Zaretskii]

> Date: Thu, 30 May 2019 19:48:34 +0100
> From: Richard Wordingham <richard.wordingham at ntlworld.com>
> 
> The reordering is that the order in the backing store is:
> 
> <LETTER...KA, SIGN E, SIGN AA>
> 
> but the ordering in the display, left to right, is:
> 
> <SIGN E, LETTER...KA, SIGN AA>
> 
> I'd be surprised if this caused much problem.  I think the big issue is
> related to the different meaning of advance width for left-to right and
> right-to-left layout.  The OpenType scheme just changes the order of
> the major base glyphs for (non-Kharoshthi) Indic reordering, so what you
> see on the page is what you have in the glyph sequence. 

I don't see any reordering here (with HarfBuzz), but maybe it's
because the only font I have that covers Myanmar is Code2000.