On 27 Mar 2011, at 21:42, [email protected] wrote: > On Sun, 27 Mar 2011, Paul Isambert wrote: >> Both, actually. The font by itself does nothing, it simply indicates what the >> rendering engine should do. I suppose (because it's seems the simplest way >> here) that this is implemented as a ligature. > > By that logic it could be said that no software ever does anything, it > only indicates what the computer hardware should do. What I meant was, > does the handling of variation selectors consist entirely of a feature > table with "sub xxx yyy by zzz" entries, so that it could be turned on in > XeTeX the same way we turn on ligatures? That's a simple yes/no question. > As you say it would make sense for the answer to be "yes", but I haven't > been able to find an authoritative answer on the Net.
Variation sequences _could_ be implemented using a ligature mechanism, but this is not in fact how it's normally done. There is a special 'cmap' subtable (format 14) used to map sequences of <base character, variation selector> to glyphs, without the requirement for the variation selector code by itself to map to a glyph ID at all. I don't think the current xetex code supports this, although it should be a pretty minor update if someone wants to work on a patch.... JK -------------------------------------------------- Subscriptions, Archive, and List information, etc.: http://tug.org/mailman/listinfo/xetex
