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

[Ed Trager]

Hi, Thep!

By "other engines" do you mean "Graphite"?

Once I get the glyph work and the (OpenType-based-) tone and vowel mark
GPOS positioning work completed in the Hariphunchai font, then I'll be
ready to work on the Graphite rule set.  Hopefully Martin Hosken will be
available to help introduce the Graphite tools and tricks to get that done
correctly.

The Graphite rule set for Hariphunchai should also work for Khottabun.
 When the time is ripe, hopefully you and I will be able to coordinate on
this to make sure we "kill two birds with one stone."

For Hariphunchai, the plan is to complete the Graphite rules first.  The
reason for this is straightforward:  There is only one version of Graphite
and thus we can avoid the issues of different implementations and versions
that plague OpenType.

Once the Graphite reference implementation is completed and well-tested in
Hariphunchai, then it will make sense to follow up with the OpenType
implementation.

- Ed


On Wed, Nov 14, 2012 at 8:36 PM, Theppitak Karoonboonyanan <
thep at linux.thai.net> wrote:

> 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/
>
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