Re: Combining crossStaff with a central beam

[Thomas Morley]

Am Sa., 19. Feb. 2022 um 19:45 Uhr schrieb Paul Hodges <pwh@cassland.org>:
>
> I am trying to set the attached image (both staves are bass clef).  I have 
> written the tuplet (without the note on the top staff in the first chord) in 
> my lower staff voice and jumping between staves as required; the missing note 
> I have set in my top staff voice as the first note of a tuplet with bracket 
> and number hidden and followed by the required skip.  But I can't find any 
> way to make the two parts of the first chord join up, because the \crossStaff 
> directive requires the stems to be in the same direction, and here they are 
> inherently not so.
>
> Any ideas?
>
> I can produce non-working code if required, but I think the description of 
> the problem is enough.
>
> Paul

Afaict, \crossStaff does not _require_ Stems in the same direction.
Ofcourse different directions usually make the Stem to far apart from
each other to connect them.
Though, if you move a NoteColumn so that the Stems are very close,
they are connectable.
Sometimes this is very tedious, but quite often the below defined
pushNC works nicely:

pushNC =
\once \override NoteColumn.X-offset =
  #(lambda (grob)
    (let* ((p-c (ly:grob-parent grob X))
           (p-c-elts (ly:grob-object p-c 'elements))
           (stems
             (if (ly:grob-array? p-c-elts)
                 (filter
                   (lambda (elt)(grob::has-interface elt 'stem-interface))
                   (ly:grob-array->list p-c-elts))
                 #f))
           (stems-x-exts
             (if stems
                 (map
                   (lambda (stem)
                     (ly:grob-extent
                       stem
                       (ly:grob-common-refpoint grob stem X)
                       X))
                   stems)
                 '()))
           (sane-ext
             (filter interval-sane? stems-x-exts))
           (cars (map car sane-ext)))
    (if (pair? cars)
        (abs (- (apply max cars)  (apply min cars)))
        0)))

\layout {
  \context {
    \Score
    \consists #Span_stem_engraver
  }
}
\new PianoStaff <<
  \new Staff = "1" {
      \pushNC
      g''4*1/8 s16.
  }
  \new Staff = "2" {
      \clef "bass"
      \override Beam.auto-knee-gap = 1
      \override Beam.positions =
      #(grob-transformer 'positions
        (lambda (grob original) (coord-translate original -1)))
      \override TupletBracket.direction = #DOWN
      \override TupletBracket.bracket-visibility = ##t
      \tuplet 5/4 {
        \crossStaff <b,! f>32[
        \change Staff = "1"
        c''' bis'
        \change Staff = "2"
        a <b, f>]

      }
  }
>>

HTH,
  Harm

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