Re: how to write a scheme function to override glissando properties

[Marc Mouries]

This slide function is great. I always have to tweak the glissando 
command because it is always too small.



On 12/19/2010 3:26 PM, jakob lund wrote:
> I
>
> 2010/12/19 Marc Hohl<address@hidden>:
> > Am 16.12.2010 17:04, schrieb Patrick Schmidt:
> > > [...]
> > > Hi Marc,
> > >
> > > thanks for your solution but I'm still trying to find out what's wrong
> > > with the scheme function I posted. I discussed the need for this function
> > > with Carl and he gave me some advice:
> > > http://www.mail-archive.com/address@hidden/msg32745.html.
> > >
> > > It might be impossible to find a general set of values for staves and tab
> > > staves. If I don't succeed I learned something about writing scheme
> > > functions, at least. Maybe you can spot the mistake in the function?
> > Hm, I don't know what's wrong - I tried something like
> >
> > slide =
> > #(define-music-function (parser location len thick beg end) (number? number?
> > ly:music? ly:music?)
> >   #{
> >      \once \override Glissando #'minimum-length = $len
> >      \once \override Glissando #'thickness = $thick
> >      \once \override Glissando #'springs-and-rods =
> > #ly:spanner::set-spacing-rods
> >       $beg \glissando $end
> >   #})
> >
> >
> > myMusic = \relative c' {
> >   \slide #10 #5 a4 b4\3
> > }
> >
> > \score {
> > <<
> >   \new Staff {
> >    \new Voice {
> >      \clef "treble_8"
> >      \myMusic
> >    }
> >   }
> >   \new TabStaff {
> >    \new TabVoice {
> >      \myMusic
> >    }
> >   }
> > }
> >
> > and that doesn't work either. I don't understand why ...
> I think what happens is that the start note, passed to your function,
> is already wrapped up in an object. \glissando is meant for use with a
> single note, rather than with a music object.
>
> You can use scheme to add the `start glissando' property to the object though:
>
> \version "2.13.40"
>
> slide = #(define-music-function (parser location length startnote)
>                                 (number? ly:music?)
>                                 #{
>   \once\override Voice.Glissando #'minimum-length = $length
>   \once\override Voice.Glissando #'springs-and-rods =
> #ly:spanner::set-spacing-rods
>       #(begin
>             (set! (ly:music-property $startnote 'elements)
>           (cons (make-music (quote GlissandoEvent))
>                 (ly:music-property $startnote 'elements)
>                 ))
>        (ly:export     $startnote))
> #})
>
> { \slide #7 a'' e'' }
>
> this page contains a similar example
> http://lilypond.org/doc/v2.13/Documentation/extending/adding-articulation-to-notes-_0028example_0029
>
> Jakob
>
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