\offset Y-offset (was: Distance of a grob from its reference point)

[Paolo Prete]

Hello Aaron,

sorry for the (a bit) late reply.

I'm looking at your code and I don't understand what is it intended to do.
You write: "% Test with bracket that is positioned by Y-offset."
but from what I see, the bracket is positioned by both
outside-staff-padding and y-offset inside \shiftOttavaBracket.
What do you mean, then?
In addition, please can you write at the beginning of the snippet what you
are going to demonstrate? IIUC, what you are going to demonstrate is
something that depends on the result of another snippet. Please, can you
put all in the same example? Otherwise all becomes too hard to be
understood/used.

Thanks,
P

%%%%
\version "2.19.83"

#(define (addRuler color left right)
  (grob-transformer 'stencil (lambda (grob orig)
    (ly:stencil-add
      (grob-interpret-markup grob #{
        \markup \with-dimensions-from \null
        \with-color #color \path #0.1 #`(
          (moveto ,left 0) (lineto ,right 0)
          (moveto ,left 1) (lineto ,right 1)
          (moveto ,left 2) (lineto ,right 2)
        ) #})
      orig))))

notesI = \fixed c''' { \mark "mark" \ottava 1 d8 8 4 \ottava 0 d,2 }
notesII = \fixed c''' { \mark "mark" \ottava 1 a8( 8) 4 \ottava 0 a,2 }

shiftOttavaBracket = #(define-music-function (amount) (number?)
  (let ((half (/ amount 2)))
    #{
      \offset Y-offset #half Staff.OttavaBracket

\override Staff.OttavaBracket.outside-staff-padding = #(+ 0.46 half)

      \override Staff.OttavaBracket.extra-offset = #`(0 . ,half)
    #}))

unshiftOttavaBracket = {
  \revert Staff.OttavaBracket.Y-offset
  \revert Staff.OttavaBracket.outside-staff-padding
  \revert Staff.OttavaBracket.extra-offset
}

{
  \omit Staff.Clef \omit Staff.TimeSignature
  \override Score.RehearsalMark.self-alignment-X = #LEFT

  % Test with bracket that is positioned by Y-offset.
  \override Staff.OttavaBracket.stencil = #(addRuler red -5 10)
  \notesI
  \shiftOttavaBracket 1
  \notesI
  \shiftOttavaBracket 2
  \notesI
  \unshiftOttavaBracket

  % Test with bracket that is positioned by outside-staff.
  \override Staff.OttavaBracket.stencil = #(addRuler blue -5 10)
  \notesII
  \shiftOttavaBracket 1
  \notesII
  \shiftOttavaBracket 2
  \notesII
}
%%%%