Subject: Re: bug#20140: 24.4; M17n shaper output rejected

From: Richard Wordingham <[email-masked]>
Date: Tue, 15 Feb 2022 01:27:34 +0000

On Mon, 14 Feb 2022 22:14:27 +0000
Richard Wordingham <[email-masked]> wrote:

> On Mon, 14 Feb 2022 15:19:36 +0200
> Eli Zaretskii <[email-masked]> wrote:
> 
> > > Date: Sun, 13 Feb 2022 20:53:10 +0000
> > > From: Richard Wordingham <[email-masked]>
> > > Cc: [email-masked], [email-masked]

> > > You should also add CGJ and ZWNJ, and some people may appreciate
> > > ZWJ - the Khottabun font has ligatures involving ZWJ, though it
> > > may just be an experimental feature - and ultimately WJ, for when
> > > someone writes a Tai Tham word breaker.    
> > 
> > How should I add CGJ and ZWNJ?  What are the rules?
> >   
> > > Oh, and Thai and Lao mai t(r)i and mai chat(t)awa and U+0324
> > > COMBINING DIAERESIS BELOW turn up occasionally - U+0324 is
> > > supported in Thep's Khottabun font, and my Da Lekh series
> > > supports Thai mai tri and mai chattawa. These characters seem to
> > > work with HarfBuzz.    
> > 
> > Not sure I understand: what patterns/rules should be added for
> > these?  
> 
> Add them all to "M" in the definition of tai-tham-composable-pattern.
> Strictly, U+0324 should also be added to "S", but I'd be surprised to
> see it in a genuine spelling.

In view of Wyn Owen's report (A Description and Linguistic Analysis of
the Tai Khuen Writing System, JSEALS 10.1 (2017)
https://evols.library.manoa.hawaii.edu/bitstream/10524/52403/1/09_Owen2017description.pdf)
on Tai Khuen spelling, one should also add U+0E49 THAI CHARACTER MAI
THO to "M". And, of course, as all 5 non-Tai Tham tone marks used with
the Tai Tham script have canonical combining class greater than 9, they
should be added to "S" - i.e. add U+0E49 to U+0E4B and U+0EC9 and
U+0ECB to "S".

Richard.