USE Indic Syllabic Category

[Richard Wordingham via Unicode]

On Sat, 23 Feb 2019 14:46:27 +0800
梁海 Liang Hai via Unicode <unicode at unicode.org> wrote:

> USE wasn’t designed to allow such a syllable structure. Tai Tham’s
> being supported by USE is kind of an oversight. And although it’s
> appropriate to allow conjoined consonants to follow post-base-spacing
> vowel signs,

There's a quick hack there.  As U+1A63 TAI THAM VOWEL SIGN AA and
1A64 U+TAI THAM VOWEL SIGN TALL AA start grapheme clusters, just promote
them to BASE.  It also solves the problem of tone mark placement.  It
does postpone the handling of the <NA, SIGN AA> ligature to after the
dissolution of syllable boundaries, which could force unwelcome changes
in a Pali-only Tai Tham font, if such exist. At least one font has an
extensive set of ligatures for the sequences <NA, SAKOT, x, SIGN AA>.
I have to handle the ligature after the dissolution because of the
syllable boundary in <NA, tone, SIGN AA>. 

A quick hack for the likes of Tai Lü ᨻᩭ᩠ᩅ᩻ᩣ <U+1A3B, U+1A6D, U+1A60,
U+1A45, U+1A7B, U+1A63> /pɔi vaː/ ‘because’ may be more troublesome
even if one omits U+1A7B TAI THAM SIGN MAI SAM.  You probably won't
like it anyway, because a good rendering looks more like the
nonsense words /pvɔi paː/ or /pvɔi pvaː/.  (I think the cluster /pv/
does not exist in any form in Tai Lü, and that would rule it out.)

Richard.