[luatex] Opentype init/medi/fina.

Arthur Reutenauer arthur.reutenauer at normalesup.org
Thu Jun 2 20:26:31 CEST 2011

> So that such an analysis must be done depends only on the tags themselves?

  Yes, there is a semantic value to the feature tags, as opposed to the lookups that implement them (otherwise there would be little point in having two different levels).  This is why there can be "typographic" and "linguistic" features (smcp would be of the former type, init of the latter).

> I.e. you have to know that even though init and e.g. smcp point to similar lookups (simple substitution), they shouldn't be treated similarly: in the case of smcp, the lookup suffices, while in the case of init it doesn't. It is surprising that nothing in the font signals such a difference...

  The features an OpenType font contains are only half the story.  The complete implementation of an OpenType-compliant system needs to take into account the specification of the layout engine (that commands to apply some features in a specific order, to do contextual analysis, etc.).  There is indeed an implementation choice here, but it has been made at the very beginning of OpenType.  In my opinion, it provides for a more balanced workload between the font designer and the implementer of the typesetting system.


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