On Fri, 30 Jan 2015 17:02:31 +0900 Leone Kim <[email protected]> wrote:
> Thanks for your reply, Richard. and sorry for late answer. > That was so helpful to make a guideline for my program. > Here's few more thing to ask. > > Q1. In your reply, > You said > >Lookup 1 would convert it to > > > >x.initial y.initial z.initial a.initial g.isol > > > >Lookup 2 would convert it to > > > >x.initial y.medial z.medial a.medial g.final > > but from left-right side order, when y.initial changed into y.medial > z.initial cannot be changed cause at that time, glyph in front of > z.ini is y.medial > > so it seems like i need to add medials to lookup 2 backtrack > coverage, is this right? I included all forms of letter in my concept of the coverage 'letter', so it is already done. (I see I wasn't consistent in naming between 'letter' and 'letters'.) So, yes, they do need to be included. As 'letter' is likely to be a single range or two ranges of glyph indices if only working with ASCII characters, it is probably more micro-efficient to work with such a broad class of glyphs! It certainly keeps it easier to code. > Q2. I think the problem suggested by Q1. can be fixed also by using > "Reverse chaining contextual single" Lookup. > So, does harfbuzz support "Reverse chaining contextual single"? I don't use it yet in my font, but I suspect it is heavily used in some Arabic script fonts, and in principle is not difficult, so I would be flabbergasted if it weren't implemented in HarfBuzz. Apple also supports OpenType layout for Arabic. One thing I would worry about with it is the range of subsidiary lookup types supported. It is only supposed to use single lookups, and I suspect that the behaviour if that rule is not observed would be highly variable from layout engine to layout engine. Richard. _______________________________________________ HarfBuzz mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/harfbuzz
