I tried to use ly.grob-original, though, in the real code it first
returned #<Grob Item >.
Namely a dead grob, on which ly:grob-suicide! was called,
and on which grob::is-live? will return #f.
That's the sort of thing that can happen if your callback
gets called after line breaking, at a point where the original
has been killed due to break-visibility. Observe:
\version "2.23.10"
#(define (debug grob)
(ly:message "~s ~s"
(ly:item-break-dir grob)
(ly:grob-original grob)))
{
\override Staff.BarLine.before-line-breaking = #debug
\override Staff.BarLine.after-line-breaking = #debug
c'1
}
After some further hours of work, following a different idea, it now
displays #<Grob BarLine > (as it should).
I'm not able to say what happened, I'm not able to debug because of
that unhelpful (oh, I'm very polite this evening) guile messages, see
the other thread.
I'm overtired like hell, close to trashing the whole project, and
close to advertising everyone to not use LilyPond for huge custom
codings.
Well, how about rolling up your sleeves and working
on that issue with unhelpful messages? See also my recent
message to lilypond-devel about the need for help to
fix regressions.
Best,
Jean
