Re: treble and bass clef simultaneously

[Aaron Hill]

On 2019-03-27 6:46 am, Werner LEMBERG wrote:
> > > > > for a solitary bass note I want to have a bass clef, not
> > > > > affecting anything else in the staff.  How can I fix the attached
> > > > > example?  I guess I need a music function that adjusts the
> > > > > vertical note offset of the upper voice...
> > > >
> > > > Could you use an "ossia" that overlaps the staff?  [...]
> > >
> > > A very nice idea, thanks!  I admit that I would never have thought
> > > of that.  Your example is almost perfect, except that I would like
> > > to avoid the horizontal gap caused by bass clef.  What property
> > > controls that?  I tried to modify some `Clef' properties given in
> > > `define-grobs.scm', but I didn't get the desired effect.
> >
> > Has the potential for overlapping ink, but try this:
> >
> > %%%%
> >   \override Clef.X-extent = #'(1.5 . 1.5)
> > %%%%
>
> Thanks, but this helps only partially.
>
> I've now extended the example, see the attached stuff.  There are
> still two problems.
>
> * The overlay fails if used within a `PianoStaff' context.  This is a
>   showstopper.
>
> * The small bass clef is placed before a barline.
>
> Ideas?

When staves are part of a group (such as PianoStaff), then it is 
important to use staff-staff-padding, not default-staff-staff-padding.  
So I goofed there.

As penance, try out the following:

%%%%
\version "2.19.82"

fakeBassClef = #(define-music-function (align-above treble bass)
  ((string? #f) ly:music? ly:music?)

  (define (context-id? id) (and (string? id) (not (string-null? id))))
  (define prefix-with-bass-clef
    (grob-transformer 'stencil (lambda (grob orig)
      (grob-interpret-markup grob #{
        \markup \with-dimensions-from \stencil $orig \overlay {
          \stencil $orig
          \translate #'(-3 . 0) \fontsize #-2 \musicglyph "clefs.F"
        }
      #} ))))

  #{
    % When alignAboveContext is unspecified, attempt to find it.
    \applyContext #(lambda (context)
      (if (not (context-id? align-above))
        (let* ((staff (ly:context-find context 'Staff))
              (id (and (ly:context? staff) (ly:context-id staff))))
          (if (context-id? id) (set! align-above id)
            (ly:warning "fakeBassClef: No named Staff found.")))))
    <<
      { \voiceOne #treble \oneVoice }
      \new Staff \with {
        \remove "Time_signature_engraver"
        \remove "Clef_engraver"
        \omit StaffSymbol

        #(ly:make-context-mod `((apply ,(lambda (c)
          (if (context-id? align-above)
            (set! (ly:context-property c 'alignAboveContext)
                  align-above))))))

        % Force overlap by using a very large negative padding.
        \override VerticalAxisGroup.staff-staff-spacing =
          #'((basic-distance . 0) (minimum-distance . 0)
              (padding . -100) (stretchability . 0))
      } {
        \clef "bass" \voiceTwo
        \once \override NoteHead.stencil = #prefix-with-bass-clef
        #bass \oneVoice
      }
    >>
  #} )
%%%%

I have tried to separate some concerns here and document a bit.  I also 
grabbed some logic from David K. that attempts to automatically 
determine the name of the context to align above.  Its robustness is 
questionable, so as a fallback I enabled an optional argument to the 
music function.


-- Aaron Hill