[Bug] Incorrect cross-staff spacing from optical corrections

[Abraham Lee]

Devs,

Two things in this report.

1) The following minimal example shows inconsistent horizontal spacing
_between_ cross-staff beamed groups, even though the optically corrected
spacing _within_ each group is excellent.

2) The beams should also be flat, shouldn't they, since there is no net
vertical movement across the beamed group?

%%%%%%%%%%%

\version "2.19.36"

cu = \change Staff = "up"
cd = \change Staff = "dn"

upper = {
  \key d \major
  \repeat unfold 8 {
    fis''16 \cd cis'' \cu
  }
}

lower = {
  \key d \major
  s1
}

\score {
  \new PianoStaff <<
    \new Staff = "up" \upper
    \new Staff = "dn" \lower
  >>
  \header { piece = "Incorrect spacing" }
}

%%%%%%%%%%%

The spacing/beaming can be corrected pretty easily like this:

%%%%%%%%%%%

upper_corrected = {
  \key d \major
  \override Beam.concaveness = #10000
  \repeat unfold 4 {
    fis''16 \cd cis'' \cu fis'' \cd cis'' \cu

    % this is for the fis'' in the next group
    \once \override NoteColumn.X-offset = #1.1
  }
}

\score {
  \new PianoStaff <<
    \new Staff = "up" \upper_corrected
    \new Staff = "dn" \lower
  >>
  \header { piece = "Correct spacing" }
}

%%%%%%%%%%%

Turning OFF the optical corrections (via the NoteSpacing layout object)
results in correct rhythmic spacing in both staves (at the expense of stem
placement, obviously).

Best,
Abraham

lilypond-cross-staff-spacing-default.png
Description: PNG image

lilypond-cross-staff-spacing-corrected.png
Description: PNG image