[HarfBuzz] Tai Tham Shaping Question #2 : MEDIAL RA

[Theppitak Karoonboonyanan]

On Thu, Nov 15, 2012 at 2:53 AM, Behdad Esfahbod <behdad at behdad.org> wrote:
> On 12-11-14 01:15 AM, Theppitak Karoonboonyanan wrote:
>> On Tue, Nov 13, 2012 at 4:45 AM, Behdad Esfahbod <behdad at behdad.org> wrote:
>>> Ed!
>>>
>>> There's no way we can fix these without a font!  Just send the font first
>>> already :).  Jonathan and I are having yet another HarfBuzz Hackfest week this
>>> week and like to address the remaining issues for "Tai *" scripts :).
>>
>> While waiting for Ed, you may try Khottabun font for Lao/Esaan Tham script,
>> another Tai Tham variation used in Lao and northeastern Thailand:
>>
>>  http://linux.thai.net/~thep/esaan-scripts/fonts/Khottabun.ttf
>>
>> The font, however, has provided all the reordering rules in GSUB, so that it
>> can still display on absence of rendering engine preprocessing. It may not be
>> good for your testing, but you can get some idea of the requirements from it.
>
> Humm.  Then it's not interesting indeed.  Even worse, those rules may conflict
> with the engine processing :|.

I know. That's why I said it might not be good for your testing. Just hope to
provide some sample for comparison using another system without the
processing.

And I hope the sample text in the test page could still be some help.

One common case that's still missing in the test page, though, is "ᨯᩪᩕᩣ",
where MEDIAL RA has to be shifted left by two positions.
The sequence is:

  U+1A2F TAI THAM LETTER DA
  U+1A6A TAI THAM VOWEL SIGN UU
  U+1A55 TAI THAM CONSONANT SIGN MEDIAL RA
  U+1A63 TAI THAM VOWEL SIGN AA

And the rendered sequence should be:

  U+1A55 TAI THAM CONSONANT SIGN MEDIAL RA
  U+1A2F TAI THAM LETTER DA
  U+1A6A TAI THAM VOWEL SIGN UU
  U+1A63 TAI THAM VOWEL SIGN AA

Regarding the font development, since we want to make progress on other
parts of the language support, such as input method, adding GSUB is all
we can do while the rendering engine supports are still lacking.

Once HarfBuzz supports it, I'll remove the rules and distribute two
different versions of the font, one for HarfBuzz, the other for other
engines.

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