patrick andries wrote:
> (*) Does anaybody know how glyphs variants and ligatures (see the
> substitution feature in Opentype) should be selected from fo ? I believe
> there is currently no such mechanism. Should we wait until another version of
> XSL-FO? Extensions ?
IIRC the spec mentions it's at the whim of the processor to
provide ligatures. There are also various code points assigned
to ligatures and presentation forms, for example U+FB01, which
could be used in the FO source (at the risk of confusing
hyphenation, spell checkers and others). If such characters
are mapped to glyphs by a font, FOP can handle them.
Also, the discussion whether presentation forms have to be
expressed by the characters itself or out of band, for example
as fonts, has never ended. XSLFO obviously provides font
specification, how presentational forms expressed as Unicode
characters have to be handled is not mentioned at all in the
spec and presumably left to the processor.
It shouldn't be all that much work to provide mappings from
presentational forms to canonical code points and hook them into the
character lookup: if the lookup for the currently selected fonts fails,
the mapping kicks in, perhaps selecting a new first priority font and
repeating the lookup with the mapping result. This could also
easily map fi to "fi". The other way around ("fi" -> fi)
is much more difficult, because of overlapping mappings needing
look-aheads (the ff and ffi ligatures) and irregularities, for
example "auffinden" does not use the ffi ligature.
J.Pietschmann
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