Re: Expert question on named contexts

[Trevor Daniels]

Mats Bengtsson asked 
> Trevor Daniels wrote:
> > My understanding is that the name given to a context is
> > stored internally as the context's id.  You can display this
> > with the ly:context-id function.  In the example above both
> > contexts have id set to "myvoice", as least that's what this
> > function returns.
>
> I take the opportunity to ask another "basic" question.
> The ly:context-id function, as well as many other functions,
> take a context as the input. I have never realized how you
> get hold of this context id. For example, how did you print the
> context id:s in my example?

There may be better ways, but this works, and is adequate
for experimentation:

displayID =
#(lambda (grob creationContext currentContext)
 (format #t "\n~a" grob)
 (format #t " was called in a ~a"
   (ly:context-name currentContext))
 (format #t " context with an id of ~a"
   (ly:context-id currentContext))
 (format #t " in staff position ~a"
   (ly:grob-property grob 'staff-position)))

<<
\new Staff ="StaffA" {
 \new Voice = "VoiceA" {
   \applyOutput #'Voice #displayID
   g'
 }
}
\new Staff = "StaffA" {
 \new Voice = "VoiceA" {
   \applyOutput #'Voice #displayID
   c''
 }
}
> >


>    /Mats

Trevor