Re: Getting context-definiton, while being in applyContext

[Thomas Morley]

Am So., 18. Nov. 2018 um 19:19 Uhr schrieb David Kastrup <address@hidden>:
>
> Thomas Morley <address@hidden> writes:
>
> > Hi,
> >
> > consider the code below. I'd like to restrict usage to Staff-like
> > contexts, i.e. Staff, Tab- and DrumStaff, etc would be ok, but
> > container-contexts like StaffGroup, etc should lead to return '().
> >
> > Pseudo-code:
> >
> > \new Staff(Group)
> >   \with {
> >     \applyContext
> >      #(lambda (context)
> >        (if <condition>
> >            ;; Do something, if we are in a Staff-like context
> >            ;;   Multiple Bottom-contexts may happen
> >            (lambda (x) ...)
> >            ;; Do nothing if we are are in container-contexts like 
> > ChoirStaff,
> >            ;; StaffGroup, etc
> >            '()
> >        )
> >   }
> > { c''1 }
> >
> > I thought the <condition> could be "Do I have the Staff_symbol_engraver?"
> > Though, how to code?
> >     \applyContext
> >      #(lambda (context)
> >        (ly:context-def-lookup context 'consists))
> > does not work, because 'context' is not a context-definition.
> >
> > Any hint how to proceed would be great.
>
> Why don't you check whether they have a Staff alias?  Basically if
> looking up 'Staff returns the context itself.
>
> --
> David Kastrup

You mean like below?

foo =
  \applyContext
    #(lambda (ctx)
       (let* ((ctx-name (ly:context-name ctx))
              (staff-ctx-def (ly:output-find-context-def $defaultlayout 'Staff))
              (staff-like? (assoc-get ctx-name staff-ctx-def #f)))

       (if staff-like?
           (format #t "\n\tI'm in a staff-like context: ~a" ctx-name)
           (format #t "\n\tWrong here in: ~a" ctx-name))))

\score {
  <<
    \new StaffGroup R1
    \new Staff R1
    \new TabStaff R1
    \new DrumStaff R1
    \new ChoirStaff R1
  >>
  \layout {
      \context Staff \foo
    \context {
      \StaffGroup
      \foo
    }
    \context {
      \ChoirStaff
      \foo
    }
  }
}

Thanks,
  Harm