[luatex] information about ligatures

[Paul Isambert]

Stephan Hennig <mailing_list at arcor.de> a écrit:
> Hi,
> 
> is there a robust way to recognize glyph nodes corresponding to
> ligatures in node lists, say in pre_linebreak_filter?  I'm thinking
> about ligatures not having a standard code point in the Unicode
> encoding, like ck-ligatures from black-letter fonts.
> 
> Is there a robust way to get information about the constituting
> characters of such a ligature, e.g., characters 'c' and 'k' in case of a
> ck-ligature?  (I do not want to disable ligatures in output.)

Ligatures are char nodes (id 37) with special subtype 2, and they have
a “components” field which is a nodelist containing the ligature’s
components.

Note that you should also consider discretionary nodes; and
“pre_linebreak_filter” will not catch ligatures in boxes (use
“hpack_filter” for that).

Best,
Paul