MetronomeMark.break-align-symbols not heeded in custom context

[Simon Albrecht]

Hi Peter, hello bug-list,

I distilled the example some more:

%%%%%%%%%%%%%%%%%
\version "2.19.80"

\layout {
  \context {
    \name "MarkLine"
    \type "Engraver_group"
    \consists Output_property_engraver
    \consists Axis_group_engraver
    \consists Metronome_mark_engraver
    \override MetronomeMark.break-align-symbols = #'(time-signature)
    \override VerticalAxisGroup.staff-staff-spacing =
    #'((basic-distance . 0)
       (minimum-distance . 0)
       (padding . 1)
       (stretchability . 3))
    \override MetronomeMark.font-shape = #'italic
  }
  \context {
    \Score
    \accepts MarkLine
    %\override MetronomeMark.break-align-symbols = #'()
  }
}

global = \tempo "Largo"

<<
  \new MarkLine \global
  \new Staff << \global { 1 } >>
>>
%%%%%%%%%%%%%%%%%%%%%
(output attached)

The tempo mark in MarkLine behaves like one in Staff with no 
break-align-symbols (uncomment the override to test). I think they 
should both be aligned to the time signature.
As a perhaps unrelated side note: With that override uncommented, the 
vertical order of the marks is flipped.

Best, Simon

Screenshot from 2018-02-14 17-00-26.png
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