Re: How to delete a created Glissando without impact on line break?

Am So., 28. Juni 2026 um 19:28 Uhr schrieb Dan Eble
<[email protected]>:
>
> On 2026-06-28 08:33, Thomas Morley wrote:
> >
> > To fix #6946 it would be sufficient to create only those Glissando
> > grobs really needed, then there would be no need to delete some of
> > them afterwards.
> > There seem to be some conditions for that purpose in the original
> > cc-engraver, but I don't understand them sufficiently.
>
> Harm,
>
> Issue #6946 seems to be a recurrence of issue #1639, which was fixed in
> b8dfb88ca356cdde12cccb4cf57ecc64397c137b.  That change defers grob
> suicide until other engravers have had the opportunity to acknowledge
> the end of the spanner.
>
> Probably, the best response would be to update the Scheme implementation
> of Glissando_engraver to defer grob suicide similarly.  Since the issue
> is a regression, the change would ideally be kept minimal so that it
> could easily be back-ported to 2.26.

For the initial codes-example of this thread  that would probably mean:

#(define-public My_glissando_engraver
  (lambda (context)
    (let ((glissando-event #f)
          (start-glissando-line #f)
          (stop-glissando-line #f)
          (to-kill '())
          (gliss-grob #f))

      (make-engraver
       (listeners
        ((glissando-event this-engraver event)
         (set! glissando-event event)
         (set! start-glissando-line #t)))

       (acknowledgers
        ((note-column-interface this-engraver grob source-engraver)
          (when stop-glissando-line
            (ly:engraver-announce-end-grob this-engraver gliss-grob
              (ly:context-property context 'currentMusicalColumn))
            (set! to-kill (cons gliss-grob to-kill))
            (set! stop-glissando-line #f)
            (set! gliss-grob #f))

          (when start-glissando-line
            (set! gliss-grob
              (ly:engraver-make-grob
                this-engraver 'Glissando glissando-event))
            (set! start-glissando-line #f)
            (set! glissando-event #f)
            (set! stop-glissando-line #t))))
       ((stop-translation-timestep this-engraver)
        (for-each ly:grob-suicide! to-kill))
       ;((finalize this-engraver)
       ; (for-each ly:grob-suicide! to-kill))
            ))))

Doing it in `stop-translation-timestep` seems to work, though Mike's
fix for #1639 does it in `finalize`.
Do you have an advice on it?
Well, I could try it out by running regtests, but maybe you have some
insight already.

> Secondarily, it might be helpful to make Spanner_break_forbid_engraver
> more robust in the presence of dead grobs.  I'll investigate this part.

That would be great.

> --
> Dan
>

Many thanks,
Harm