[HarfBuzz] Mai Kang Lai in Tai Tham, summary draft

[Richard Wordingham]

On Wed, 22 May 2013 11:23:14 +1000
Andrew Cunningham <lang.support at gmail.com> wrote:

> I need to think about it and see how variation in positioning has been
> handled in other contexts, i.e. MYANMAR SIGN DOT BELOW in its
> positioning in Karen languages vs Burmese and Mon.
> 
> Although I think the Tai Tham discussion and the way the fonts are
> evolving has already taken us to the stage where the fonts will be
> designed for Barfbuzz and will not render correctly on Uniscribe.

Is there yet a Tai Tham definition for Uniscribe?  Is there an embargoed
definition?

> Regarding the choice between solution one and solution two; are there
> examples of the positioning being contrastive, i.e. the same document
> using two or three of the differening conventions to mark
> distinctions between works? Or is it purely stylistic i.e. differing
> calligraphic and typographic conventions?

I don't understand your question, unless 'works' is a typo for
'words'.  If you meant 'words', then I would say 'no', though it may be
possible to devise arrangements of glyphs whose meaning depends on which
convention is in use.

The short answer is that these are stylistic differences.

> If the difference is purely stylistic .. that leads us to solution 2.
 
> For solution 2 there seems to be two options:
 
> 1) fonts tailored for a specific typographic/stylistic convention; or
> 
> 2) more typographically advanced fonts using graphite or opentype
> features to accommodate the variations, would it be possible to
> handle it as a variant glyph or stylistic set?

It would be possible in graphite; the problem comes with technologies
that can't transpose glyphs while keeping track of the backing store
correspondences.  The problem is epitomised by Pali nominative singular 
_saṅgho_ 'the community of Buddhist monks'. One style wants the glyph
order <HIGH SA, MAI KANG LAI, SIGN E, LOW KHA, SIGN AA> and the other
wants the glyph order <HIGH SA, SIGN E, LOW KHA, MAI KANG LAI, SIGN
AA>.  (The encoding is <HIGH SA, MAI KANG LAI, LOW KHA, SIGN E, SIGN
AA>.

The problem is not that we need different fonts for the various styles;
the problem is that we seem to need different *reordering* rules.

> I hope with a bit of spare time next week I can sit down and try
> experimenting with a minimal font, and see what could be done.

The question is whether GPOS can sensibly convert one of the two orders
above to the other.

Richard.