[HarfBuzz] Tai Tham NGA, SAKOT is not Kinzi

[Richard Wordingham]

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_!

> >> 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.

> 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_.

> 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?  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.

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.

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.

Richard.