Barry Schwartz wrote:
It's probably a good idea to have many eyes looking at that code,
because there seems to be a tendency to implement feature support
incorrectly (including myself when I first started dealing with
OpenType features in my hobby work). A common effect that I have seen
with both Ant and HarfBuzz is for ligatures to be applied before
small-caps-substitution.
well, one reason for doing it in lua is that there can be several
solutions and i'm pretty sure that there will be; the code used in
context mkiv can be a starting point (it will have hooks and such) but i
know the tex community good enough to know that different solutions will
pop up; also, since ms and adobe and whoever seem to interpret things
differently we might end up with even more variants (apart from the need
to deal with buggy fonts)
(btw, so far i made three variants just to get an idea of open type and
curently i'm making a new one)
one thing that would help is simple test fonts (like the ones that idris
makes, so that's one area where help is needed)
It is important to keep in mind that features are not ordered; they
are simply sets of lookup indexes. What you do is compute the union of
all the lookups of the selected features, and then do the lookups in
the order they appear in the lookup table.
indeed
It concerns me a little that LuaTeX should be able to handle ligatures
but not line-breaks in the middle of ligatures, because
ligature-lookups in OpenType are handled just like any other
substitution lookup. They don't require any special code different
from that of other lookup types; from my point of view, LuaTeX
shouldn't have to know anything about ligatures, just how to select
and execute lookups.
not even that, you just (re)construct node lists and manipulate glyph
nodes (which can have lig info)
I studied the mkiv code several weeks ago but never in enough depth to
see what was going on in there. Also I don't know much at all about
OpenType support for non-LGC scripts.
i expect to have more final code sometime in januari
Hans
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