Bug? Mismatched grace notes at beginning of staff cause extra clefs in other staffs

[Lucas Werkmeister]

Hi everyone,

I found what I suspect is a LilyPond bug, but I’m not sure yet :) minimal example:

\version "2.18.2"

<<
  \new Staff { \grace c' c' }
  \new Staff { \clef "bass" }
>>

Instead of beginning with a bass clef, the lower staff begins with a violin clef and then has a bass clef right after the time signature. If a different key signature is set (omitted in the above example for brevity), the accidentals are only printed after that extra clef as well, and the whole group (bass clef and accidentals) is shifted to the left so that it overlaps the time signature.

This seems to happen when the two staves begin with different amounts of grace notes. A workaround is to add a silent grace note to the lower staff (\grace s) – just make sure that it’s the same duration as the real grace note in the upper staff: if it’s longer (e. g. a simple \grace s without explicit duration if the current duration is 4 and the duration of the other grace note is 8), then the upper staff will have the same problem instead (extra clef – same as the original one in this case – and accidentals only after that).

Unfortunately, I’m unable to check if this still happens in the current development version of LilyPond since I’m getting an error when building from Git, but that’s for a different email :) perhaps someone else can check that, so I don’t open a bug report for something that’s already fixed? (Or perhaps it’s simply expected that grace notes should be aligned between staves? But that would surprise me.)

Oh, and for the sake of people googling for this error – it also affects \acciaccatura, \appoggiatura and \slashedGrace.

Cheers,
Lucas