Re: How to get bounding NoteColumns of the first of consecutive TextSpanners

[David Nalesnik]

On Wed, Mar 3, 2021 at 3:17 PM David Nalesnik <david.nalesnik@gmail.com> wrote:

>
> The only thing I can think of at the moment is to compare the
> StaffSymbol of the left bound with that of each of the NoteColumns on
> the right.  Of course, I realize right away that that will break down
> if the spanner crosses a line break. (Use an override of
> 'before-line-breaking?)
>
> Here's the code I hacked up.  I'll keep thinking about this.
>
> Best,
> David
>
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>
> #(define tst
>    (lambda (grob)
>      (let* ((left-bound (ly:spanner-bound grob LEFT))
>             (right-bound (ly:spanner-bound grob RIGHT))
>             (ncs-from-grob
>              (ly:grob-array->list (ly:grob-object grob 'note-columns)))
>             (right-bound-elts
>              (ly:grob-array->list
>               (ly:grob-object right-bound 'elements)))
>             (ncs-from-right-bound
>              (filter
>               (lambda (elt) (grob::has-interface elt 'note-column-interface))
>               right-bound-elts))
>             (left-bound-staff-symbol (ly:grob-object left-bound 
> 'staff-symbol))
>             (same-staff-right-bound-nc
>              (filter
>               (lambda (nc)
>                 (eq? (ly:grob-object nc 'staff-symbol)
>                      left-bound-staff-symbol))
>               ncs-from-right-bound))
>             )
>        (ly:grob-set-property!
>         (ly:grob-array-ref
>          (ly:grob-object (car same-staff-right-bound-nc) 'note-heads)
>          0)
>         'color red)
>        (pretty-print
>         (list
>          left-bound
>          right-bound
>          ncs-from-grob
>          (equal? left-bound (car ncs-from-grob))
>          ncs-from-right-bound
>          same-staff-right-bound-nc
>          )))))
>
> mus = {
>   bes4-\tweak #'after-line-breaking #tst
>   \startTextSpan
>   b\stopTextSpan
>   \startTextSpan
>   bis\stopTextSpan
> }
>
> <<
>   { a4 a a }
>   \mus
>   { c' c' c' }
> >>

Rather than comparing with the StaffSymbol of the left bound, it would
be better to look at the StaffSymbol of the TextSpanner:

#(define tst
   (lambda (grob)
     (let* ((left-bound (ly:spanner-bound grob LEFT))
            (right-bound (ly:spanner-bound grob RIGHT))
            (ncs-from-grob
             (ly:grob-array->list (ly:grob-object grob 'note-columns)))
            (right-bound-elts
             (ly:grob-array->list
              (ly:grob-object right-bound 'elements)))
            (ncs-from-right-bound
             (filter
              (lambda (elt) (grob::has-interface elt 'note-column-interface))
              right-bound-elts))
            (spanner-staff-symbol (ly:grob-object grob 'staff-symbol))
            (same-staff-right-nc
             (filter
              (lambda (nc)
                (eq? (ly:grob-object nc 'staff-symbol)
                     spanner-staff-symbol))
              ncs-from-right-bound))
            )
       (ly:grob-set-property!
        (ly:grob-array-ref
         (ly:grob-object (car same-staff-right-nc) 'note-heads)
         0)
        'color red)
       (pretty-print
        (list
         left-bound
         right-bound
         ncs-from-grob
         (equal? left-bound (car ncs-from-grob))
         ncs-from-right-bound
         same-staff-right-nc
         )))))

mus = {
  bes4-\tweak #'after-line-breaking #tst
  \startTextSpan
  b\stopTextSpan
  \startTextSpan
  bis\stopTextSpan
}

<<
  { a4 a a }
  \mus
  { c' c' c' }
>>

%%%%%%%%%%%
HTH,
David