There are in fact about 70 combinations of marks that may be needed for polytonic Greek that are not precomposed in Unicode. This includes the upsilon + smooth breathing already mentioned, epsilon and omicron with circumflex (and with breathings) used in epigraphy, as well as all the doubtful vowels with macron plus accents/breathings. The latter are used in grammars and reference books that want to show quantity (not normally printed in standard editions of literary texts).
If I were to make a complete OT Greek font, with all the above as well as the combinations already in Unicode, which would provide better performance: substitutions or positioning via OT features? David > However, I agree that in the case of polytonic Greek, > given the relatively small number of unencoded glyphs that would be > required, it makes more sense to use ligature substitutions. > > John Hudson
