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

[Andrew Cunningham]

I was wondering if myanmar , etc should be included in indic engine, or
wether it would be better to fork the indic engine rather than overloading
it with divergent rules?


On Thursday, 24 May 2012, Behdad Esfahbod <behdad at behdad.org> wrote:
> On 05/23/2012 06:48 PM, Andrew Cunningham wrote:
>> I think what Ed is saying is that Tai Tham follows a similar model to
Myanmar
>> rather than a pure Indic model, where you have a distinct medials vs
subjoined
>> consonants wher subjoined consonants require a virama and medials don't
>
> I see.  Thanks for the clarification.
>
>> Par of a fundamental change between myanar in unicode 4.1 and 5.1
>
> Good to know.  I'll give HB a run on my Myanmar corpus and see if I can
fix a
> few high-impact issues.
>
>> Will look at my sources to confirm for Tai Tham.
>
> Thanks,
> b
>
>> A.
>>
>> On Thursday, 24 May 2012, Behdad Esfahbod <behdad at behdad.org
>> <mailto:behdad at behdad.org>> wrote:
>>> Hi Thep,
>>>
>>> Humm, the message from Ed hat you are replying to never made it to me
or to
>>> the list.  Replies inline.
>>>
>>>
>>> On 05/23/2012 06:53 AM, Theppitak Karoonboonyanan wrote:
>>>> Hi, Ed, Behdad,
>>>>
>>>> On Sun, May 20, 2012 at 3:45 AM, Ed Trager <ed.trager at gmail.com
>> <mailto:ed.trager at gmail.com>> wrote:
>>>>> On Fri, May 18, 2012 at 5:48 PM, Behdad Esfahbod <behdad at behdad.org
>> <mailto: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).
>>>
>>> I'm not questioning the separate encoding.  I don't care :-).  What I'm
saying
>>> is that you need a SAKOT before them for them to be considered part of
the
>>> same syllable according to the Indic OpenType spec and my
implementation.
>>> Now, if you think Unicode intended these to subjoin without a SAKOT,
then I
>>> like you to point me to documentation about that.
>>>
>>> If that is the case, we would need changes to the Indic machine.  Not
>>> impossible, but I first want to make sure that it is indeed the case.
>>>
>>> behdad
>>>
>>>
>>>
>>>>> 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.
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>>
>> --
>> Andrew Cunningham
>> Senior Project Manager, Research and Development
>> Vicnet
>> State Library of Victoria
>> Australia
>>
>> andrewc at vicnet.net.au <mailto:andrewc at vicnet.net.au>
>> lang.support at gmail.com <mailto:lang.support at gmail.com>
>

-- 
Andrew Cunningham
Senior Project Manager, Research and Development
Vicnet
State Library of Victoria
Australia

andrewc at vicnet.net.au
lang.support at gmail.com
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