[HarfBuzz] Tai Tham NGA, SAKOT is not Kinzi

[Theppitak Karoonboonyanan]

On Thu, Apr 11, 2013 at 6:08 AM, Richard Wordingham
<richard.wordingham at ntlworld.com> wrote:
> On Wed, 10 Apr 2013 13:08:06 +0700
> Theppitak Karoonboonyanan <thep at linux.thai.net> wrote:
>
>> On Fri, Apr 5, 2013 at 6:23 AM, Richard Wordingham
>> <richard.wordingham at ntlworld.com> wrote:
>> > On Thu, 4 Apr 2013 13:10:53 +0700
>> > Theppitak Karoonboonyanan <thep at linux.thai.net> wrote:
>
>> So, LA TANG LAI is not relevant here. (What's its use, BTW?)
>
> <LOW TA, LA TANG LAI> is yet another way of writing _tanglai_.
> Actually, LA TANG LAI looks like the subjoined form of another,
> unencoded symbol, which can be seen in Table 16 in
> http://www.seasite.niu.edu/tai/TaiLue/graphic%20blends.htm - yet
> another way of writing _tanglai_!

Ah, thanks. This one is more familiar to me. It's usually written this way
in Lao Tham, except that the shape represented by <SAKOT, LA> is used
instead of LA TANG LAI.

>> >> Now I wonder how far MAI KANG & MAI KANG LAI is shifted to the
>> >> left in Khuen/Lanna.
>> >
>> > In Tai Khuen, or at least, printed material, MAI KANG LAI is placed
>> > between the two consonants.  The typeset course notes from Wat Suan
>> > Dok (Chiang Mai, Northern Thai) clearly show it on the first base
>> > consonant.
>>
>> 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
>
> As Firefox presents the tutorial, the PDF is faulty.  The choeng
> consonants don't appear at all!  The rule is kept to on p.12 as well as
> the font allows.  Mai kang lai has been mapped to phinthu, so there is
> no way the author can put the mai kang lai on LOW KHA in _sankho_
> (สังโฆ).
>
> Problems with fonts is why I have preferred to work from hand-written
> materials.

What I really mean to refer to is the explanation text, which is in Thai.
It translates: "(Mai Kang Lai sign) is called "Mai Kang Lai", and is equivalent
to "Ang" (Mai Han Akat + NGA). It is used as final sound by placing on the
second consonant only."

What appears on Evince for "sangkho" is that Mai Kang Lai is placed in the
middle between SA and vowel E, which may be limitation of the document
preparation system.

What I really mean is the explanation. The same applies to the tutorial clip
in another mail (starting at 9:14), but the position of Mai Kang Lai in samples
in that clip is clearer, no shift.

>> 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
>
>> With the information I have, I tend to think that its natural
>> position is on the second consonant, while it may be shifted to the
>> left as the matter of style.
>
> Certainly its original position is on the second consonant.
>
>> The typeset course from Wat Suan Dok you mentioned is somewhat
>> different from what I have learned. Can it be exception?
>
> It's not unique.  I have also found it in a small, largely handwritten
> handbook, even for the word _sankho_.

I'd like to see some sample, for education's sake. Especially, is it explicitly
explained in words?

>> If so, and if "tanglai" invalidates the use of kinzi model, how about
>> having the rendering engine preprocess it without SAKOT? For example:
>> <SA, MAI KANG LAI, LOW KHA, E, AA> ->
>> <SA, E, LOW KHA, MAI KANG LAI, AA>.
>
> If a font is to replicate the style of the handbook, can a GPOS table
> effectively rearrange the latter back to look like SA, MAI KANG LAI, E,
> LOW KHA, AA?

The same question applies to the other style as well. Can the GPOS
do the same to shift it to second consonant on the lack of preprocessing?

In fact, my font also features some complicated GSUB rules to handle this,
which I try to get rid of by the aids of rendering engine. Meanwhile, doing so
would cause the other school to bear the same load instead.

The question is, which one should be the default, and which one should be
the exception? As we discuss so far, only some parts of Lanna (which I
haven't seen myself yet) advocates the non-shifting Mai Kang Lai, while
Khuen, Lao, and the other parts of Lanna itself, all advocate the shifting
version. (That's why it's called "Mai Kang Lai", isn't it?)

Meanwhile, Lanna seems to be more dynamic in styles, which makes things
more complicated. For Lao, there is only one school. So, it's less
problematic to bear the complication. But what about the shifting school of
Khuen/Lanna?

>  Looking through 'Chieng Tung: Its Way of Life', I found
> <LETTER A, MAI KANG LAI, HIGH KA, MEDIAL RA, I, SAKOT, SSA> and <LETTER
> A, MAI KANG LAI, LOW CA, E, I, SAKOT, NYA>.  In both cases, the mai
> kang lai comes immediately after the LETTER A in visual order.

This would make the rules more complicated. Lao Tham has nothing to do
with this in case it has to bear the complication.

I just wonder how the shifting school of Khuen/Lanna would handle this case
in the font alone. It would be much more complicated than letting the
rendering engine do the job.

The Kinzi model to distinguish this just comes back to my mind, but we
cannot break "tanglai" at the same time. (Again, there is no "tanglai"
with Mai Kang Lai in Lao Tham. So, no problem for Lao here, either.
Just thinking about Khuen/Lanna.)

Another way, which I think most users tend to abuse already, is to encode
it in semi-visual order, such as <HIGH SA, LOW KHA, MAI KANG LAI, E, AA>.
Can we accept that?

> A seemingly simple solution would be to let the font control whether
> the rearrangement is done - I think I've seen something along these
> lines for another script.  It won't handle such cases as the usual rule
> in the MFL, where a vowel above or ra hong on the second consonant
> throws the mai kang lai back on to the preceding consonant.

I tend to choose only one school to support. That would simplify things a lot.
So far, I haven't seen any evidence of the non-shifting school myself.
But my study is also limited, especially outside Lao Tham.

> Going through the Tai Khuen passages in that book, I found a case (on
> p.150) where <HIGH SA, MAI KANG LAI, LOW KHA> had a line break before
> the LOW KHA.  That may have been a mistake, and I'm not sure how
> significant it is to rendering.

I have only seen counter-examples in Lao Tham. For example, the word
<MA, U, MAI KANG LAI, LOW KA, U, RA> is seen in a palm leaf
manuscript to break between <U> and <MAI KANG LAI>, with <MAI KANG LAI>
over <LOW KA> on the next line.

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