[luatex] Opentype init/medi/fina.
zappathustra at free.fr
Thu Jun 2 13:01:28 CEST 2011
The init, medi and fina tags in OT fonts set variants of glyphs
according to position (used by arabic fonts or scripts). Now you'd think
it's a contextual substitution.
those features should be implemented as single substitutions (GSYB
lookup type 1), and that "the application is responsible for noting word
Now, in my (ideal) view of opentype, tags are just pointers to lookups,
and only lookup types decide how things are implemented, so that you can
ignore the tag once you have the lookup. But this is not the case here:
the tag modifies how the lookup should be implemented (so that a simple
substitution should be implemented as a contextual one).
So: have I misunderstood something? Or: should I correct my view of tags
and lookups (so that tags can't be ignored)? And in the latter case, any
idea why init/medi/fina weren't implemented as contextual subtitutions
in the first place (as are e.g. word-final variants in Minion)?
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