Vertically centering text in a Lilypond Dynamics staff

Question

When engraving my own scores, I like to have all dynamics centered vertically. In Lilypond, we can easily do this by inserting a Dynamics "staff" between the two staves of a piano score.

Whereas standard dynamic markings of f, mp, etc. are vertically centered, text dynamics are not:

\version "2.20.0"

right = \relative c'' {
  c1 c c c
}

left = \relative c' {
  c1 c c c
}

dynamics = {
  s1\f s-"text" s^"text" s_"text"
}

\score {
  \new PianoStaff <<
    \new Staff = "right" \right
    \new Dynamics = "dynamics" \dynamics
    \new Staff = "left" \left
  >>
  \layout { }
}

How can I vertically center these text dynamics?

Answer 1

The problem here is that TextScript grobs use by default ly:side-position-interface::y-aligned-side for Y-offset, so they are treated as side position elements, that is, positioned either over or under the parent.

To get a different behaviour simply override Y-offset. If you use for example self-alignment-interface::y-aligned-on-self you can set the Y-offset to 0 with alignment determined by self-alignment-Y. So you can use a callback for self-alignment-Y to use the value of direction to be able to use -"text" for center, ^"text" for up and _"text" for down.

Of course you can do other things with Y-offset as well, but this is what I described above:

\version "2.22.0"

right = \relative c'' {
  c1 c c c
}

left = \relative c' {
  c1 c c c
}

dynamics = {
  s1\f s-"text" s^"text" s_"text"
}

\score {
  \new PianoStaff <<
    \new Staff = "right" \right
    \new Dynamics = "dynamics" \with {
      % Will use self-alignment-Y to place element
      \override TextScript.Y-offset = #self-alignment-interface::y-aligned-on-self
      % Use negative value of direction, i.e. CENTER -> align to center, UP -> align to bottom, DOWN -> align to top
      \override TextScript.self-alignment-Y = #(lambda (grob) (- (ly:grob-property grob 'direction)))
      % use CENTER as default direction instead of DOWN
      \override TextScript.direction = #CENTER
           
    } \dynamics
    \new Staff = "left" \left
  >>
  \layout { }
}

Answer 2

I do this with a Y-offset:

\version "2.20.0"

right = \relative c'' {
  c1 c c c
}

left = \relative c' {
  c1 c c c
}

dynamics = {
  \override TextScript.Y-offset = -0.5
  s1\f s^"text" 
}

\score {
  \new PianoStaff <<
    \new Staff = "right" \right
    \new Dynamics = "dynamics" \dynamics
    \new Staff = "left" \left
  >>
  \layout { }
}