Re: Code pointer from end-BarLine to previous NoteHead.?

[Jean Abou Samra]

> 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