[luatex] information about ligatures

Stephan Hennig mailing_list at arcor.de
Thu Jan 9 18:49:36 CET 2014

Am 06.01.2014 20:10, schrieb Philipp Gesang:
> ···<date: 2014-01-06, Monday>···<from: Stephan Hennig>···
>> What callback does luaotfload use for the processing?
> The font handler is applied to both the pre_linebreak_filter and
> the hpack_filter.

Interesting.  I'd have expected luaotfload being active earlier on, like
in the ligaturing and kerning callbacks.  Why is luaotfload active only
that late?

>> And what is the way to go for packages fighting for a callback?
> luatexbase.add_to_callback() without priority (append).
>> If callbacks are "just chained", how can I be sure that luaotfload
>> has already done its processing before my package?
> Luaotfload inserts the callbacks into the chain at highest priority.
> As long as you do not specify a priority, you should be fine.

Thanks!  (Somehow I have the feeling that I've had asked the same
question already before. :)

>> >       mode | liga
>> >            |  -     +
>> >       -----+--------
>> >       base | 256   258
>> >       node | 256   256
>> OK, what does that teach me?
> That you should be able to call the inverse operation
> (node.unprotect_glyphs()) on the node list to restore the
> original values.

Didn't got that.

>> I think I'll just look at (and follow) the components field to
>> parse ligatures and hope for the best ...
> I came up with this heuristic:
> http://tex.stackexchange.com/a/120529/14066

Yes, I'm already doing something similar.  For the time being it works.
 Will reconsider node.unprotect_glyphs() in stormy weather.

Best regards,
Stephan Hennig

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