[HarfBuzz] Tai Tham NGA, SAKOT is not Kinzi

Tue Apr 9 23:08:06 PDT 2013

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:
>
>> Is that recommended by Unicode? Why using <SAKOT, LA> when
>> MEDIAL LA is available? Especially for Lao Tham, there are two
>> variants of MEDIAL LA (U+1A56 SIGN MEDIAL LA, and the other similar to
>> U+1A57 SIGN LA TANG LAI). So, one should be explicit which one to use,
>> the situation similar to U+1A63 VOWEL AA and U+1A64 VOWEL TALL AA.
>
> MEDIAL LA and LA TANG LAI are given in the code charts.  L2/07-007 give
> the form of <SAKOT, LA>.  It is very similar to LA TANG LA, but without
> the horizontal cross-piece.  Words with 'ho nam' are very variable
> between <HIGH HA, SAKOT, LA> and <HIGH HA, MEDIAL LA>.

I see. So, LA TANG LAI is not relevant here. (What's its use, BTW?)

>> 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

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.

The typeset course from Wat Suan Dok you mentioned is somewhat
different from what I have learned. Can it be exception?

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>.

>> For Lao Tham, the shift is not as far as the position on "boomaa".
>> It's just shifted at most to the middle between the consonant and
>> vowel AA. But for "booma", it's centered right above BA.
>
> That's what I've seen a lot of in Northern Thai.  However, material that
> has been written using a computer font (I don't about mechanical
> printing) has <AA, MAI KANG> that looks like THAI CHARACTER SARA AM in
> so far as the position of the MAI KANG is considered.  I think of that
> as a Bangkok style.  A relevant divide is what happens to the tone
> mark - does it stay on the middle of the consonant, or does it join the
> mai kang?  When searching a document for examples, one sees just how
> large a proportion of the cases in Thai are the word น้ำ 'water', but
> this word is no use as an example in Tai Tham because NA and AA merge
> and MAI KANG and TONE-2 then naturally occur together.  Fortunately,
> whether the tone mark goes after or above MAI KANG is naturally handled
> by GPOS.

Unfortunately, tone marks are never used in traditional Lao Tham.
So, I don't have an evidence for this yet.

>> The former, if it's really to be done for Tham, is similar to the
>> case of Thai SARA AM (U+0E33), which has already been handled by
>> rendering engines.
>
> The problem is not in doing the rearrangement of <HIGH TA, TONE-1, AA,
> MAI KANG> to <HIGH TA, MAI KANG, TONE-1, AA>; it is that it is wanted
> for some styles but not for others.  There is also the complication that
> <NA, TONE-2, AA, MAI KANG> needs to be rearranged in all styles so
> that TONE-2 may be placed on or to the right of MAI KANG.
>
> The SEA shaper appears not to handle it.  Unfortunately, I'm finding it
> hard to see what the HarfBuzz shaper does just from reading the code.

I still have to think on this case. No idea yet at the moment.

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