#5001 Beam disappears with TupletNumber.avoid-slur = #'outside

[Simon Albrecht]

Reported by Risto Vääräniemi.
See also discussion on the user list.

Starting somewhere between 2.19.25 and .29, the following code has the second beam squashed somewhat to the left edge of the type area (output attached):

:::TeX
\relative c'' {
  \tuplet 3/2 {a8( g a)}
  \override TupletNumber.avoid-slur = #'outside
  \tuplet 3/2 {a8( g a)}
}

Harm pointed out three potentially related issues
and gave some further test code:

:::TeX
suicideTN =
\override TupletNumber #'before-line-breaking =
  #(lambda (grob) (ly:grob-suicide! grob))

omitTN = \override TupletNumber #'stencil = #'()

hideTN = \override TupletNumber #'transparent = ##t

avoidSlurOutside = \override TupletNumber #'avoid-slur = #'outside


printTuplets =
#(define-music-function (parser location nmbr mus mus2)
(integer? ly:music? ly:music?)
#{
\relative c'' {
  $mus2
  $mus
  \repeat unfold $nmbr \times 2/3 { g8^( a) g }
}
#})

nr = 4

\markup \rounded-box \fill-line { "default" }

\markup "default"
\printTuplets #nr {}{}

\markup "suicide TupletNumber-grob"
\printTuplets #nr \suicideTN {}

\markup "omit TupletNumber.stencil"
\printTuplets #nr \omitTN {}

\markup "TupletNumber.transparent = ##t"
\printTuplets #nr \hideTN {}

\markup \rounded-box \fill-line { "avoid-slur : outside" }

\markup "default"
\printTuplets #nr {} \avoidSlurOutside

\markup "suicide TupletNumber-grob"
\printTuplets #nr \suicideTN \avoidSlurOutside

\markup "omit TupletNumber.stencil"
\printTuplets #nr \omitTN \avoidSlurOutside

\markup "TupletNumber.transparent = ##t"
\printTuplets #nr \hideTN \avoidSlurOutside

[Thomas Morley]

A possible work-around:
Set avoid-slur 'ignore and adjust Y-offset of the TupletNumber.

adjustTN =
#(define-music-function (val)(number?)
#{
  \once \override TupletNumber.Y-offset =
    #(lambda (grob) 
      (+ (ly:tuplet-number::calc-y-offset grob) val))
#})

\relative c'' {
  %% The default case
  \tuplet 3/2 {a8^( g a)}
  %% The bug seems not to be present for avoid-sur 'ignore
  %% Hence you could workaround with:
  \once \override TupletNumber.avoid-slur = #'ignore
  \adjustTN 1.1
  \tuplet 3/2 {a8^( g a)}
}