Re: Issue 3918: Add \alternatingTimeSignatures (issue 97110045)

[Urs Liska]

Am 17.05.2014 01:51, schrieb Thomas Morley:
> 2014-05-17 0:38 GMT+02:00 Urs Liska <address@hidden>:
> > Am 16.05.2014 09:41, schrieb address@hidden:
>
> > > Well, we have \omit already.  What if we had
> > > \appearance [markup] [grobname or music]
> > >
> > > Which would basically be the syntactic sugar for overriding the stencil
> > > with an appropriate grob-interpret-markup?
> > >
> > > That way one could just define some markup function for formatting time
> > > signatures and use it either in markup contexts or indeed for overriding
> > > a time signature.
> >
> >
> > If I understand you correctly this would mean that one would write
> >
> > \appearance \fractionList #'((6 8)(5 4)) Score.TimeSignature
> >
> > instead of
> >
> > \override Score.TimeSignature.stencil = \fractionList #'((6 8)(5 4))
> >
> > ?
>
> I think David thought of something at the lines of the following function:
>
> appearance =
> #(define-music-function (parser location mrkp item)
>     (markup? symbol-list-or-music?)
>   (let ((stil (lambda (item)
>                 (grob-interpret-markup item mrkp))))
>     #{ \tweak stencil #stil #item #}))
>
> \relative c' {
>      \appearance
>        \markup "XY"
>        Staff.Clef
>
>      \appearance
>        \markup
>          \override #'(baseline-skip . 0)
>          \override #'(word-space . 0.2)
>          \line {
>            \center-column { \number 3 \number 4 }
>            \center-column { \number 6 \number 8 }
>          }
>        Score.TimeSignature
>      c1
> }

That looks good.
With a little modification (just skipping the wrapping of the generated 
markup to a stencil one could still use fractionList with that like:

\appearance \fractionList #'(#t (6 8)(7 8)) Score.TimeSignature

What do you think?

a) \appearance still seems a bit odd because it's not a verb.
   \use would be appropriate but I'm not sure if that's too generic
   to be used for the discussed function.
b) What would be the right order of operations?
   I assume "appearance" should be included first
   (or in one combined step because it's not so useful to first
   add \fractionList just to modify it immediately afterwards.

Urs

> Cheers,
>    Harm

modified-fractionList.ly
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