Re: How To Selectively Show a Staff

[David Wright]

On Sun 18 Oct 2020 at 23:43:18 (+0200), Jean Abou Samra wrote:
> 
> Le 18/10/2020 à 17:40, Marc Shepherd a écrit :
> > In a score where "RemoveAllEmptyStaves" is set, a staff will
> > normally not show in a system where it has all rests.
> > 
> > Sometimes, you may /want/a staff (temporarily) to appear on a
> > specific system, even though it contains all rests. What’s the
> > command or setting to do this?
> > 
> Well, I can't explain the output of:
> 
> \version "2.23.0"
> 
> showIt = \set Staff.keepAliveInterfaces = #'(rest-interface)
> hideIt = \unset Staff.keepAliveInterfaces
> 
> \new Score \with \RemoveAllEmptyStaves
> <<
>   {
>     R1 R1 R1 \break
>     R1 R1 R1 \break
>     \showIt
>     R1 R1 R1 \break
>     \hideIt
>     R1 R1 R1 \break
>     R1 R1 R1 \break
>   }
>   {
>     \repeat unfold 15 { c'1 }
>   }
> >>
> 
> I would expect just the third staff to be shown, but in fact the
> second and the fourth are also printed.
> 
> Do folks here think this is a bug? Am I missing something?
> 
> Anyway, there is this workaround:
> 
> \version "2.23.0"
> 
> \new Score \with \RemoveAllEmptyStaves
> <<
>   {
>     R1\break
>     << { \oneVoice R1 } \\ { \once \hideNotes c'1 } >> \break
>     R1\break
>   }
>   {
>     \repeat unfold 3 { c'1 }
>   }

I just moved the show/hide away from the line ends, because I don't
know precisely when each component of the source is seen/enacted.
There may be some look behind/ahead.

Cheers,
David.

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