On Tue, Dec 12, 2006 at 08:56:06PM +0600, Christopher Fynn wrote:
>
> Rich Felker wrote:
>
> >Whether it's possible to support all combinations efficiently, I don't
> >know. The OpenType system is very poorly designed from what I can
> >tell. In the Tibetan fonts I've examined, rather than just saying
> >"character U+0F62 needs to use an alternate glyph when followed by any
> >of {list here} combining characters", there are individual ligature
> >combination tables for each pairing. Whether this is just lack of
> >understanding on the font designer's part or fundamental limitations
> >of OpenType, I'm not sure.
>
> Although you can build Tibetan stacks using contextual substitutions
> I've found through trial and error that it is generally much more
> efficient to have pre-composed consonant stacks and simple
> (non-contextual) GSUB lookups. You will probably still need some
> contextual lookups for vowel marks and for a few variant forms of stacks
> - especially in cursive style Tibetan - but having a lot of contextual
> substitution lookups in a Tibetan font seems to slow everything to a
> crawl especially with long documents.
OK, so basically it's a workaround for poor OpenType implementations.
Got it. Thanks for the explanation.
BTW, I heard there was a mailing list specifically for Tibetan
font/script issues. Is that still active, and if so, how can I
subscribe?
Rich
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