Re: cross-staff versions of \arpeggioArrowUp etc.

[Joe Neeman]

On Tue, 2009-08-04 at 14:01 -0700, Mark Polesky wrote:
> Mark Polesky wrote:
> 
> > Otherwise, does this look good?
> 
> I'm sorry to keep doing this, but I keep finding ways of
> improving this. Now I think users should find this very
> intuitive, although the internal workings are more complex.
> 
> I've attached the most recent version, which includes an
> annotated example at the bottom, which explains the behind-
> the-scenes operations.
> 
> Anyone want to have a look at it?
> Anyone have any comments/suggestions?

I'd like to second Neil's objection regarding the hard-coding of
GrandStaff/PianoStaff/StaffGroup as contexts containing
Span_arpeggio_engraver. Given the flexibility of contexts and engravers
in lilypond, it isn't a good idea to assume that certain contexts are
the only ones to provide a particular functionality.

Also, one other minor comment:
> #(define (find-spannable-context context)
>   (let ((spannable-contexts '(GrandStaff PianoStaff StaffGroup)))
>     (if (member (ly:context-name context) spannable-contexts)
>         context
>         (let ((parent (ly:context-parent context)))
>           (if parent
>               (let ((parent-name (ly:context-name parent)))
>                 (if (member parent-name spannable-contexts)
>                     parent
>                     (find-spannable-context parent)))
>               #f)))))

you've written out the recursion twice: it should be
        (let ((parent (ly:context-parent context)))
          (if parent
              (find-spannable-context parent)
              #f))

Cheers,
Joe
>