[HarfBuzz] Tai Tham NGA, SAKOT is not Kinzi

[Theppitak Karoonboonyanan]

On Thu, Apr 25, 2013 at 4:35 PM, Martin Hosken <mhosken at gmail.com> wrote:

>> In a Lanna tutorial [1], it's stated in page 12 that MAI KANG LAI is placed on
>> the second consonant only. But the position is actually in the middle.
>>
>>   [1] http://dl.dropbox.com/u/12266813/TaiTham/lanna-tutorial.pdf
>
> I think this is a wrong analysis. On p23 of the same pdf the last example
> shows the mai tang lai over the following glyph which is an -e vowel.
> So clearly the mai tang lai is not associated with the second consonant.
> In my analysing this character I came to the conclusion that for Lanna,
> Khuen and Lue, mai kang lai is a final on the first consonant, even if it
> hangs out to the right quite a long way.

I was probably wrong for the illustration. But please note the explanation
(in Thai), which explicitly says "to be placed on the second consonant only".

For the illustration which really obeys this rule, please see the samples
from Prof. Manee Phayomyong's book:

https://dl.dropboxusercontent.com/u/12266813/TaiTham/manee_1.jpeg

And a live tutorial by a monk (in Kham Muang):

http://www.youtube.com/watch?v=Qk4_tPnL3us#t=09m14s

So, my conclusion is rather: there are two different styles in Lanna
for Mai Kang Lai.

>From the name "Mai Kang Lai" (literally "Running Mai Kang"), and from
the explanations in textbooks (even though it's not strictly obeyed in many
places), I believe the shifting version is traditional style, which is still
preserved in Lao Tham, while the non-shifting version is new style.

>> For Lao Tham, [2] on page 14, [3] on page 15, it's clearly placed on the
>> second consonant.
>>
>>   [2] http://www.laomanuscripts.net/downloads/tham_pali.pdf
>>   [3] http://www.esansawang.in.th/esanweb/es3_text/palitx_web.pdf
>
> Is this Lao Tham or Isaan? Anyway, it's a new discovery to me,
> so thank you for finding it.

The first one is from Lao PDR, and the second one is from Ubolratchathani
of Thailand. However, I think it's hard to distinguish between Lao and
Esaan Tham to the point that they can be treated as one.

> It's tricky to decide how to mark this ordering. I think we have two
> choices to make:
>
> 1. We don't encode the difference. We keep the mai tang lai encoded after
> the first consonant (which also puts it in front of the second consonant,
> so the encoding position is unchanged) and we say that the difference in
> rendering position is stylistic. Thus an OT engine would need a specific
> feature to trigger the reordering (given that GPOS can't attach forwards,
> only backwards).
>
> 2. We encode the difference. I like Thep's suggestion of using sakot for
> this.  Thus an encoding of C1, vowels, mai kang lai, sakot, C2
>
> The difference in position *is* stylistic. As to whether it's based purely
> on language or whether it's language and style, I don't know. But the
> difference in position carries no meaning. This would argue for approach 1.
> On the other hand, such a radical rendering difference can be argued as
> being a spelling difference, and this favours approach 2.

Thanks for the good summary. AFAIK, I think the styling issue lies only in
Lanna. Other languages, at least for Lao/Esaan Tham, seem to have only
one style.

> Approach 2 is
> also easier for an OpenType engine. But it is harder for users who would
> have to use a special keyboard to do the reordering. Mind you they would
> have to have that for approach 1 also, so there's nothing to be gained there.

I can't grab this part. What's special in the sequence? I think all (Mai Kang
Lai, Sakot, consonants) should be available in ordinary Tai Tham keyboards.

And what's specially required for approach 1, where only Sakot is omitted?
Rather, the complexity of approach 1 is on fonts and rendering engines.
Did you mean to say this?

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