Re: Align above "current" staff

[Aaron Hill]

On 2020-09-27 3:23 am, Martín Rincón Botero wrote:
> I hope this message lands in the right 2018 thread. I find an ossia
> function very worth the work! I tried several things yesterday but
> none of them really worked. I amended a few details to Urs/David's
> code (a couple of \with attributes) but there are still some minor
> issues (other than this big 13 years old bug
> https://gitlab.com/lilypond/lilypond/-/issues/127).
>
> When I look at the code (see below) I would expect this to happen:
> \ossia {%ossiamusic} {%music}. What happens is the opposite. This is
> trivial, since the only thing you have to tell the user is that the
> normal music goes before the ossia music, but it makes me wonder why
> anyways... Other minor issues are that the ossia music doesn't inherit
> the clef from the normal music, and that placing all this inside a
> \relative is not reliable (the first note of whichever of both
> components might be in an unexpected octave). Does Urs, who started
> working on this, or David (or anyone :-)) have any idea on how to
> solve these minor issues? Here the amended code with an example that
> demonstrate them:
>
> [ . . . ]

Firstly let me be clear that I have not chased down all information 
relating to this thread, so I very well might be missing important 
details.

I can see no reason why the order of arguments could not be swapped so 
that the ossia-music comes first.  This is very useful as it clarifies 
why \relative works the way it does.  The ossia-music expression gets 
processed before the remaining music.  The first "c" in the remaining 
music follows the final "e" in the ossia-music, not the "g" is the 
preceding music.

Regarding clefs, I have a patched version of \ossia that attempts to 
match the current clef settings by mimicking how \clef works:

%%%%
\version "2.20.0"

\layout {
  \context {
    \Staff
    \name OssiaStaff
    \alias Staff
    \remove "Time_signature_engraver"
    \magnifyStaff #2/3
    \hide Clef
    firstClef = ##f
  }
  \inherit-acceptability OssiaStaff Staff
}

ossia =
#(define-music-function
  (ossia-music music)
  (ly:music? ly:music?)
  (let ((staff-name #f)
        (clef-props '(clefGlyph
                      middleCClefPosition
                      clefPosition
                      clefTransposition
                      clefTranspositionStyle)))
    (define (initialize context)
      (set! staff-name
        (ly:context-id (ly:context-find context 'Staff)))
      (set! clef-props
        (map (lambda (prop)
               (cons prop (ly:context-property context prop)))
             clef-props)))
    (define (update context)
      (ly:context-set-property! context
        'alignAboveContext staff-name)
      (for-each (lambda (prop)
                  (ly:context-set-property! context
                    (car prop) (cdr prop)))
                clef-props)
      (ly:set-middle-C! context))
    #{ \applyContext #initialize
       << \new OssiaStaff
            \with #(ly:make-context-mod `((apply ,update)))
            { #ossia-music }
          #music >> #}))

\new Staff = "viola" \relative {
  \clef alto
  c'4 d e g
  \ossia { e^"Treble clef? No, it's alto now." d f e }
         { c^"c'? Yes, because \\relative says so." b c d }
  c b c2
}
%%%%

Note that I went ahead and defined an OssiaStaff context so that 
properties relating to it are not buried within the \ossia function.  
Also a little refactoring should make the function's logic a little 
easier to follow.


-- Aaron Hill

ossia.cropped.png
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