aligning marks with time signature fails with more than one staff

[Andrew Hawryluk]

This one has me stumped. The initial tempo mark of a piece
should be left-aligned with the time signature. If I comment out the
second Staff context in this example then the alignment is perfect,
but when both staffs are present it shifts the mark to the right
somewhat. (See attached images.)

Any ideas what might cause this effect? I have already tried different
staff start delimiters (StaffGroup, GrandStaff, no delimeter), and the
effect is the same each time.

-AH


\version "2.11.38"

\paper { ragged-right = ##t }

timeAlign = {
       \once \override Score.RehearsalMark #'self-alignment-X = #-1
       \once \override Score.RehearsalMark #'break-align-symbols =
#'(time-signature)
       \once \override Staff.TimeSignature
#'break-align-anchor-alignment = #LEFT
}

larghetto = {\timeAlign \mark \markup \normalsize \bold {Larghetto} }

\score {
       \new PianoStaff {
       <<
               \context Staff = "RH" { \time 6/8 \key e \minor \larghetto b'4}
               \context Staff = "LH" { r8 r8 }
       >>
       }
}

onestaff.png
Description: PNG image

twostaffs.png
Description: PNG image

comparison.png
Description: PNG image