[luatex] What are user-defined whatsit nodes?

[Stephan Hennig]

Am 23.11.2014 um 19:43 schrieb Hans Hagen:

> you can just reconstruct the original from the (nested) ligatures,

I have experimented with code like that.  The problem is that triple
ligatures can be broken in two ways:


  ffl   =>
             ff + l  Leuchtstofflampe (fluorescent lamp)

             f + fl  Tiefflieger (low-level attack aircraft)

The former case is easy, since components of the ffl ligature are glyphs
'ff' and 'l'.  The second case requires to compose the fl ligature from
raw font information, since it is not readily available.  Effectively,
this means implementing a full ligaturing routine.  I wouldn't want to
do that.  Is there any interface available that given two glyphs returns
a ligature of those glyphs?

Best regards,
Stephan Hennig