Aligned-above lyrics stick to wrong staff when stretching

[Arvid Grøtting]

>:-)

Hi,

let me first say that 2.11.20 does seem to resolve most of the bugs in the
new vertical spacing engine.  Right now I only have one small nit to pick:
Lyrics contexts aligned above a given staff should stay close to that
staff when stretching.  That is, in the case below, you should have:

title
<spring>
lyrics
staff
lyrics
<spring>
lyrics
staff
lyrics
<spring>
...etc.

Minor detail, but annoying (and definitely wrong) when the stretch
gets big.

Here's a quite minimal example; it's hard to make it much smaller and
still get reasonable stretching...

-- Arvid


\version "2.11.20"

\header { 
  title = "Aligned-above lyrics should stay close to their staff"
  texidoc = "Lyrics aligned above a context should stay close to that context
when stretching.

With 2.11.20, the Bass I lyric line here sticks to the Tenor staff, below
the Tenor II lyrics." 
}

\paper { ragged-last-bottom = ##f }

tune = \relative c { \repeat unfold 2 { c4( e) g2 | \break c1 } \bar "|."  }

\score {

  \context ChoirStaff <<

    \new Staff = tenors <<
      \clef "treble_8"
      \new Voice = tenori { \voiceOne \tune }
      \new Voice = tenorii { \voiceTwo \tune }
    >>
    \new Staff = basses <<
      \clef "bass"
      \new Voice = bassi { \voiceOne \tune }
      \new Voice = bassii { \voiceTwo \tune }
    >>

    \new Lyrics \with {alignAboveContext=tenors} \lyricsto tenori {
      Te -- nor one!  A -- _ bove!
    }
    \new Lyrics \with {alignBelowContext=tenors} \lyricsto tenorii {
      Te -- nor two!  Be -- _ low!
    }
    \new Lyrics \with {alignAboveContext=basses}  \lyricsto bassi {
      Bas -- ses one!  A -- _ bove!
    }
    \new Lyrics \with {alignBelowContext=basses} \lyricsto bassii {
      Bas -- ses two!  Be -- _ low!
    }
  >>
  \layout {}
 }