Re: Dashed Stem

[David Nalesnik]

Hi Urs,

On Fri, May 11, 2012 at 7:06 AM, Urs Liska <address@hidden> wrote:

Am I right that you can't make a Stem dashed? I didn"t find anything in the IR.

What would then be the proper way to attach a dashed line to a note in place of the Stem?

Here's something I came up with.  It's not ideal.  If you compare the substitute stems with ordinary stems, you'll find differences.  (These relate, I think, to how rounded the lines are--to 'blot-diameter.)  But hopefully this will do.

The argument allows you to specify the number of dashes in your stem.

\version "2.15.38"

#(define (dashed-stem num)

  (lambda (grob)

    (let* ((stencil (ly:stem::print grob))

           (ext (ly:stencil-extent stencil Y))

           (len (interval-length ext))

           (lst '())

           (factors

             (map

               (lambda (x) (* (/ len (1- (* 2 num))) x))

               (iota (* 2 num)))))

     (define (helper args)

       (set! lst

             (cons

               (make-line-stencil

                 0.13 ;; thickness

                 0 (+ (car ext) (car args))

                 0 (+ (car ext) (cadr args)))

               lst))

       (if (null? (cddr args))

           lst

           (helper (cddr args))))

     (if (zero? num)

         stencil

         (apply ly:stencil-add (helper factors))))))

\relative c'' {

  \once \override Stem #'stencil = #(dashed-stem 2)

  c

  \once \override Stem #'stencil = #(dashed-stem 3)

  d

  \once \override Stem #'stencil = #(dashed-stem 4)

  e

  \once \override Stem #'stencil = #(dashed-stem 5)

  f

}

HTH,

David