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

[Andrew Cunningham]

Thanks Martin.

On 24 May 2012 14:59, Martin Hosken <mhosken at gmail.com> wrote:
> Dear Behdad,
>
>> Good to know.  I'll give HB a run on my Myanmar corpus and see if I can fix a
>> few high-impact issues.
>
> I would commend UTN#11 as worth reading at least the first half, on this. It'll give you a good feel for what's involved.
>
> In the case of Tai Tham, we took the Myanmar model as the basis and built on it. Tai Tham writing systems have the extra fun that you can subjoin a final and even the start of another word. So you can get fun things like:
>
> U+1A3B U+1A66 U+1A76 U+1A60 U+1A36 U+1A6C U+1A26 = p + ii + tone2 + sakot + n + o + ng
>
> and this common spelling:
>
> U+1A20 U+1A63 U+1A60 U+1A36 : k + aa + sakot + n
>
> Of course you can also mix prevowels and medials into this mix:
>
> U+1A4B U+1A6B U+1A36 U+1A60 U+1A32 U+1A55 U+1A63 U+1A60 U+1A3F : ?a + vowel + n + sakot + t + medial ra + aa + sakot + y
>
> Tai Tham is just plain fun :)
>
> Yours,
> Martin
>
>
>>
>> > 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>
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-- 
Andrew Cunningham
Senior Project Manager, Research and Development
Vicnet
State Library of Victoria
Australia

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