[luatex] information about ligatures

[Stephan Hennig]

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.)

Best regards,
Stephan Hennig