[HarfBuzz] Tai Tham NGA, SAKOT is not Kinzi

[Richard Wordingham]

On Sun, 21 Apr 2013 22:07:53 +0700
Theppitak Karoonboonyanan <thep at linux.thai.net> wrote:

> This could be the solution we're seeking. But how should the font do
> the signalling?

The method used before was the presence or absence of a certain
substitution within some feature.

> This makes me get back to read to your thread starting post more
> carefully. Yeah, you said Mai Kang Lai is shifted right to the midway
> between the first and the second consonant. I read that as "shifting
> school". Probably, we should check how "sangkho" is written in Khuen,
> then.

I couldn't find any examples.  But I did find an example of อัญเชิญ
(first line of my Khuen sample in
http://homepage.ntlworld.com/richard.wordingham/lanna/maikanglai.pdf ),
with the first nasal spelt with MAI KANG LAI. I think that should be
good enough.

> I withdraw my claim that it would be less problematic to let Lao shift
> Mai Kang Lai in the font. I've experimented with the SAKOT-less
> encoding scheme and I've got boundary problem with some words
> like <SA, MAI KANG LAI, LOW KHA, RA, HIGH TA, NA, HIGH PA,
> NA, AA, MA> (สงฺฆรตนปณาม). With SAKOT-less encoding scheme,
> Mai Kang Lai continues being shifted over following consonants.
> But as the rule comprises multiple stages, the shift is incomplete
> and causes duplicates of Mai Kang Lai along the rendered text.
> Getting over this would be tricky.

I assume yuo're using the ligature substitution (look-up type 4)
followed by the mulitiple substitution (look-up type 2).  One solution
is to use different glyphs for swapped and unswapped MAI KANG LAI.

> Regarding the question about multiple forms of the same word,
> it's already true. For example, "sangkho" can be written either:
> - <HIGH SA, MAI KANG, LOW KHA, E, AA>
> - <HIGH SA, NGA, SAKOT, LOW KHA, E, AA>
> - <HIGH SA, MAI KANG LAI, [SAKOT,] LOW KHA, E, AA>
> What if we accept that the last one can be split into 2 different
> forms? Just like the multiple forms of "tanglai", it should not be a
> surprise if there exists a book that explains the several ways to
> write "sangkho" in Lanna by considering the shifting and non-shifting
> Mai Kang Lai as different forms.

I think the appropriate character to distinguish the last two forms is
ZWNJ.

I'm pleased you've found the spelling with plain MAI KANG; I was
wondering what had happened to it.

Richard.