[HarfBuzz] Tai Tham NGA, SAKOT is not Kinzi

[Theppitak Karoonboonyanan]

On Wed, Apr 3, 2013 at 4:53 AM, Richard Wordingham
<richard.wordingham at ntlworld.com> wrote:
> On 7 January 2013, Behdad Esfahbod replied to Theppitak Karoonboonyaan:
>
>>> - Final NGA (U+1A59) with virama following is not reordered after
>>>   the next base consonant (at the end of line 4).
>
>> Oh, that's new.  We need to figure out how to implement that.  That
>> one will be tricky.
>
> If it has now been implemented for Tai Tham, please reverse it.  It does
> *not* represent kinzi.  The sequence occurs as normal NGA with a
> subscript consonant in the 'Lanna-Thai Dictionary, Maefahluang
> Volume' (MFL), e.g. in <U+1A48 TAI THAM LETTER HIGH SA, U+1A26 TAI THAM
> LETTER NGA, U+1A60 TAI THAM SIGN SAKOT, U+1A25 TAI THAM LETTER LOW KHA>
> 'sangha'.  Indeed, <NGA, SAKOT, WA> can represent a phonetic initial
> cluster in Northern Thai, and as in Burmese is written with a normal
> NGA plus a subscript consonant.
>
> A separate character exists for 'kinzi', U+1A58 TAI THAM SIGN MAI KANG
> LAI.  It is regularly used for 'sangha' in the Tai Khuen articles in
> 'ᨡᩮᨾᩁᨭᩛᨶᨣᩬᩁᨩ᩠ᨿᨦᨲᩩᨦ / เขมรัฐนครเชียงตุง / Chieng Tung: Its Way of Life',
> where the word is written <U+1A48, U+1A58, U+1A25>, with U+1A58
> appearing midway between the base consonants.

I second this change, then. I was confused between MAI KANG LAI and
FINAL NGA because in Lao Tham, the two signs are the same.
(Both are called Mai Ang Lan in Lao.)

So, my proposal for Lao Tham is to apply above rule with U+1A58 instead.

And Lao Tham fonts can then provide two identical glyphs for U+1A58 and
U+1A59, with only the former affected by the rule.

> Mai kang lai is written rather differently in Northern Thailand, and it
> was proposed as separate character, at 1A5A, in the proposal with
> Unicore reference L2/07007 and ISO reference ISO/IEC
> JTC1/SC2/WG2/N3207R. Unfortunately, the ISO committee copy is no longer
> on line.  I get the impression that in Thailand the symbol is in
> transition from appearing above the second base consonant to appearing
> above the first consonant.  I have a text book consistently showing it
> on the first consonant, a text book showing between the two consonants,
> and a text book consistently showing it on the second consonant except
> in _tanglai_ 'all', 'many'.
>
> The MFL explains that the symbol appears on the second consonant
> and gives two examples starting <SA, MAI KANG LAI> in which the symbol
> appears on the following consonant.  Neither word appears in the body
> of the dictionary. The appearance in the MFL is best explained as there
> being inhibiting factors which prevent it appearing on the second
> consonant, such as a vowel above or SIGN RA.  However, in the body
> of the dictionary, words starting <SA, MAI KANG LAI> are consistently
> written with MAI KANG LAI above the SA!

In Lao Tham manuscripts and tutorial texts I have seen so far, it's
consistently written above the second base consonant.
This includes Lao Tham documents found in North-Eastern Thailand.

But when the same sign functions as FINAL NGA (U+1A59), its logical
positioning is after the syllable's vowel, such as ᨿᩩᩙ, ᨶᩣᩙ, ᩈ᩠ᨿᩙ, ᨴᩬᩙ.

> A noteworthy example is Northern Thai _tanglai_ <LOW TA, MAI KANG
> LAI, SIGN LA, AA, SAKOT, YA> 'all', 'many', where MAI KANG LAI
> almost always starts above the initial consonant.  This may be because
> SIGN LA is part of the same syllable as LOW TA.  The textbook showing
> it between consonants shows it, in this case, between SIGN LA and the
> vowel AA.
>
> Is there a problem with supporting this variety in positioning?

Can it be distinguished with the presence of following SAKOT?

For example:

<SA, MAI KANG LAI, LOW KHA, VOWEL E, VOWEL AA>
= MAI KANG LAI above SA

<SA, MAI KANG LAI, SAKOT, LOW KHA, VOWEL E, VOWEL AA>
= MAI KANG LAI above LOW KHA

Regards,
--
Theppitak Karoonboonyanan
http://linux.thai.net/~thep/