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

[Thomas Morley]

Am Sa., 16. Juli 2022 um 14:05 Uhr schrieb Jean Abou Samra <jean@abou-samra.fr>:
>
>
>
> > Le 16 juil. 2022 à 13:01, Thomas Morley <thomasmorley65@gmail.com> a écrit :
> >
> > Hi,
> >
> > I'm trying to code an engraver setting a pointer from BarLine to
> > previous NoteHead and an override for BarLine.Y-offset acting upon
> > that pointer.
> > It does not work, if the BarLine is at end.
> >
> > Here a stripped down example (every security is removed and all is
> > heavily simplified):
> >
> > %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> >
> > \version "2.23.9"
> >
> > tst =
> > #(lambda (ctx)
> >  (let ((nc #f)
> >        (bar #f))
> >  (make-engraver
> >    (acknowledgers
> >      ((bar-line-interface engraver grob source-engraver)
> >        (set! bar grob))
> >      ((note-head-interface engraver grob source-engraver)
> >        (set! nc grob)))
> >    ((stop-translation-timestep engraver)
> >      (if (and nc bar)
> >          (ly:grob-set-object! bar 'element nc))))))
> >
> > moveBarLineToPrevHead =
> >  \override Staff.BarLine.Y-offset =
> >    #(lambda (grob)
> >      (let* ((prev-head (ly:grob-object grob 'element))
> >             (staff-pos
> >               (if (ly:grob? prev-head)
> >                   (ly:grob-property prev-head 'staff-position #f)
> >                   #f)))
> >       (pretty-print
> >         (list
> >           (cons 'prev-head prev-head)
> >           (cons 'staff-pos staff-pos)))
> >       (/ (or staff-pos 10) 2)))
> >
> > \layout {
> >  \context {
> >      \Staff
> >      \consists \tst
> >      \moveBarLineToPrevHead
> >  }
> > }
> >
> > \new Staff { b4 \bar "." b }
> > \new Staff { b4 \bar "." }
> >
> > %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> >
> > I'm aware the (main) difference between the two staves is the
> > break-direction of the BarLine.
> >
> > Though, how to catch it ?
> > Or how to do it different?
> >
> > Thanks,
> >  Harm
>
>
> In a given timestep, the currentCommandColumn is at the _left_ of the 
> currentMusicalColumn. You’re storing a pointer to the next note head, not the 
> previous.
>
> Jean
>
>

Hi Jean,

thanks for the hint.
Alas, the code below _ensures_ the NoteHead _before_ the BarLine is
taken (if I'm wrong here, I am completely lost), and again the
override for BarLine.Y-offset fails.

tst =
#(lambda (ctx)
  (let ((nhds '())
        (bar #f))
  (make-engraver
    (acknowledgers
      ((bar-line-interface engraver grob source-engraver)
        (set! bar grob))
      ((note-head-interface engraver grob source-engraver)
        (set! nhds (cons (cons (ly:context-current-moment ctx) grob) nhds))))
    ((stop-translation-timestep engraver)
      (let* ((curr (ly:context-current-moment ctx))
             (nhds-to-consider
               (remove
                 (lambda (x)
                   (equal? (car x) curr))
                 nhds))
             (sorted-nhds
               (reverse
                 (sort
                   nhds-to-consider
                   (lambda (x y)
                     (ly:moment<? (car x) (car y)))))))
    (if (and (ly:grob? bar) (pair? nhds))
        (begin
          (ly:grob-set-property! (cdr (car sorted-nhds)) 'color red)
          (ly:grob-set-object! bar 'element (car sorted-nhds))
          (set! bar #f))))))))

moveBarLineToPrevHead =
  \override Staff.BarLine.Y-offset =
    #(lambda (grob)
      (let* ((bar-elt (ly:grob-object grob 'element))
             (prev-head (cdr bar-elt))
             (staff-pos
               (if (ly:grob? prev-head)
                   (ly:grob-property prev-head 'staff-position #f)
                   #f)))
       (pretty-print bar-elt)
       (/ (or staff-pos 10) 2)))

\layout {
  \context {
      \Staff
      \consists \tst
      \moveBarLineToPrevHead
  }
}

%\new Staff { b4 \bar "." b }
\new Staff { b4 b \bar "." }


Further hints are much appreciated.

Cheers,
  Harm