Re: Slur position : "catching" Llilypond values...

[David Nalesnik]

On 2/7/11, Éditions IN NOMINE <address@hidden> wrote:
> Well, let me explain  :-)
>
> I often use \once \override Voice.Slur #'positions = #'(a . b) to adjust
> Slur position, and most of the time, I only need to modify only one of a or
> b.
>
> I'd like to be able to "catch" the default a or b value and tell Lily not to
> touch it, so that I could tell Lily something like :
>
> \once \override Voice.Slur #'positions = #'(* . b)
>
> with * = default value, which would mean "whatever you want"

Hello,

There probably is a better way to do this, but the function below
seems to do the trick.  It adds an offset to the Y-coordinate of
either or both of the slur's attachment points.  Setting one value of
the pair to zero will leave one end-point as it is.  (See attached
files.)

offsetPositions =
  #(define-music-function (parser location offsets) (pair?)
    #{
       \once \override Slur #'positions = #(lambda (grob)
         `(,(+ (car $offsets) (cdar (ly:slur::calc-control-points grob))) .
           ,(+ (cdr $offsets) (cdr (cadddr (ly:slur::calc-control-points 
grob))))))
    #})


--David

slur positions offset.ly
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