[Dev-luatex] OTF engine in LuaTeX

Barry Schwartz chemoelectric at chemoelectric.org
Mon Dec 29 05:17:01 CET 2008


Hans Hagen <pragma at wxs.nl> skribis:
> not even that, you just (re)construct node lists and manipulate glyph nodes 
> (which can have lig info)

I just get concerned when I see reference to stuff like ligature info,
because in general, and speaking in part as an amateur font designer,
it seems difficult to stray from just strictly following the algorithm
(an algorithm that is treated oddly casually in the spec). For
example, once you throw in contextual alternates and contextual
ligatures, you have two or more lookup tables to go through, with any
number of single, multiple, and ligature substitutions, which have to
be performed in order. Just throwing in 'dlig' along with 'liga', or
even just one of them, is likely to get you two or more lookups to go
through, with arbitrary substitutions performed in-between. In
general, how can one know what the result will be without just going
through lookup lists or equivalent data structures?

I'd like to know if there are some shortcuts safely applicable to the
general case, but I've failed completely to come up with any and after
a while stopped trying. :)

I've moved on to wonder how best to handle chaining contextual
substitutions that look at glyphs in more than one word at a
time.




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