Re: Staff switch line (documentation?) bug

[Graham Percival]

On 22-Feb-05, at 7:01 AM, Yuval Harel wrote:
> Sorry, this still seems wrong to me.
>
> First, PianoStaff.followVoice=##t usually does not produce voice  
> followers where the staff is not switched. When it behaves well it is  
> still a useful feature, and should be documented. Also, I think the  
> behavior I've shown should still be considered a bug.
>
> Second, the new example given in the documentation  
> (http://lilypond.org/doc/v2.5/Documentation/user/out-www/lilypond/ 
> Staff-switch-lines.html) is misleading, and IMO bad style. The  
> property is set before the context in which it belongs is  
> instantiated. If I understand correctly, this only works because the  
> staff and voice context are unnamed. Someone not yet familiar with  
> \set commands will expect this example to always work throughout the  
> piano staff. But it won't have effect outside the main voice, and will  
> produce an unexpected extra Staff if the first staff is named (it  
> probably is going to be named eventually, if the piece has any staff  
> switches in the opposite direction).

Sorry, I'm lost here.  Anybody else want to comment on this?  On a  
question of
style, or programming, or documentation?


> Also, I don't understand why the example code shows a {c} but the  
> output shows a {c'}.

I can answer this issue.  :)    The example is created with the option  
[relative=1].  Even
though we don't have a \relative c' {}  in the text that's displayed,  
LilyPond treats it
as if it has \relative c' {} in there.


> I suggest that \showStaffSwitch be changed to mean {\set  
> PianoStaff.followVoice=##t}, and the documentation to say:
>
> """
> Whenever a voice switches to another staff, a line connecting the  
> notes can be printed automatically. This is switched on using  
> \showStaffSwitch, and turned off using \hideStaffSwitch.
>
>      \context PianoStaff <<
>        \context Staff=one \context Voice {
>          \showStaffSwitch
>          c'1
>          \change Staff=two
>          b2 a
>          \change Staff=one
>          \hideStaffSwitch
>          c'1
>          \change Staff=two
>          b2 a
>        }
>       \context Staff=two { \clef bass s1*4 }
>      >>
>
> \showStaffSwitch will show staff-switch lines for all voice in the  
> current PianoStaff. It is equivalent to {\set PianoStaff.followVoice =  
> ##t}. To produce lines for the current voice only, use {\set  
> followVoice = ##t}.
> """
>
> Thanks,
>         Yuval<property-init.ly.patch>