Re: Add an arbitrary music property

[Thomas Morley]

2018-06-08 21:26 GMT+02:00 Urs Liska <address@hidden>:
> Hi,
>
> is there anything wrong with adding an arbitrary property to a
> SequentialMusic like that:
>
> \version "2.19.80"
>
> someNote = { c' d' }
>
> #(set! (ly:music-property someNote 'foo) "bar")
>
> \displayMusic \someNote
>
> ?
>
> The following is a MWE of a new extension I plan for scholarLY, and it seems
> to work. \sic and \corr add such an arbitrary property to the music while
> \choice uses that to retrieve one element out of a list of music
> expressions.
>
> \version "2.19.80"
>
> #(define selection 'sic)
> %#(define selection 'corr)
>
> choice =
> #(define-music-function (mus) (ly:music?)
>    (let*
>     ((elts
>       (map
>        (lambda (expr)
>          (cons (ly:music-property expr 'choiceType) expr))
>        (ly:music-property mus 'elements)))
>       (chosen (assq-ref elts selection)))
>     (if chosen
>         chosen
>         (first (ly:music-property mus 'elements)))))
>
> tagMusic =
> #(define-void-function (mus tag)(ly:music? symbol?)
>    (set! (ly:music-property mus 'choiceType) tag))
>
> sic =
> #(define-music-function (mus) (ly:music?)
>    (tagMusic mus 'sic)
>    mus)
>
> corr =
> #(define-music-function (mus) (ly:music?)
>    (tagMusic mus 'corr)
>    mus)
>
> \relative {
>   c' c g' g |
>   \choice {
>     \sic { g }
>     \corr { a }
>   }
>   a g2
> }
>
> But before proceeding I'd like to know if I'm not doing anything stupid by
> injecting two list items like so:
>
> (make-music
>
> 'SequentialMusic
>
> 'choiceType
>
> 'sic
>
> 'elements
>
> (list (make-music
>
> 'NoteEvent
>
> 'pitch
>
> (ly:make-pitch -1 4)
>
> 'duration
>
> (ly:make-duration 2))))
>
>
> Urs


Hi Urs,

this looks more or less the same as with custom-grob-properties.
Probably a bit safer, if you register them in `all-music-properties'
calling `music-property-description'.

Look at
http://lsr.di.unimi.it/LSR/Item?id=977
for an example

Cheers,
  Harm