[HarfBuzz] Tai Tham / Lanna (iso15924="lana") shaping question

[Theppitak Karoonboonyanan]

Hi, Ed, Behdad,

On Sun, May 20, 2012 at 3:45 AM, Ed Trager <ed.trager at gmail.com> wrote:
> On Fri, May 18, 2012 at 5:48 PM, Behdad Esfahbod <behdad at behdad.org> wrote:
>> On 05/18/2012 04:02 PM, Ed Trager wrote:
>>>
>>> In Tai Tham, U+1A6E VOWEL SIGN E needs to be shifted all the way to
>>> the left so that the final visual appearance would be:
>>
>> Are you sure?  Without U+1A60 TAI THAM SIGN SAKOT before the subjoined
>> consonant?  Reading Unicode suggests that you need that sign betwee PA and LA.
>
> For most subjoined consonants, yes, that's true.  But note in
> particular that U+1A56 MEDIAL LA and U+1A57 MEDIAL LA TANG LAI were
> encoded separately.  In the case of these two "LA" signs, I believe
> there are two reasons justifying the separate encoding:
>
> (1) These are variant forms of the same subjoined letter LA:
> apparently, there is no other good way to do it other than encoding
> both.
>
> (2) Both of these LA signs can be part of triple consonant clusters,
> i.e. "KLW" appears in the common word Thai / Tai word for banana,
> กล้วย, "klwy" .  In Tai Tham, both the L and the W appear as
> below-base stacked forms (and actually the "y" is also a subjoined
> form, but it's kind of hanging off the right side of the whole stack).
>
> There are some other separately-encoded subjoining consonant signs:
> U+1A5B, U+1A5C, U+1A5D, U+1A5E.

Please also count U+1A55 (MEDIAL RA) in the rule, although it's not a
subjoined form.

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