Flared horizontal bracket ties

[Andrew Bernard]

Here is a wonderful function created for me by Thomas Morley, for
flared ties. It may be of interest to others, but my question is, how
can I modify this code to draw dashed lines, with controllable dash
period and dash fraction?

Andrew

%==================

%{
  Flared horizontal bracket ties
  by Thomas Morley
%}


#(define ((flared-tie coords) grob)

   (define (pair-to-list pair)
     (list (car pair) (cdr pair)))

   (define (normalize-coords goods x y dir)
     (map
      (lambda (coord)
        (cons (* x (car coord)) (* y dir (cdr coord))))
      goods))

   (define (my-c-p-s points thick)
     (make-connected-path-stencil
      points
      thick
      1.0
      1.0
      #f
      #f))

   ; outer let to trigger suicide
   (let ((sten (ly:tie::print grob)))
     (if (grob::is-live? grob)
         (let* ((layout (ly:grob-layout grob))
                (line-thickness (ly:output-def-lookup layout 'line-thickness))
                (thickness (ly:grob-property grob 'thickness 0.1))
                (used-thick (* line-thickness thickness))
                (dir (ly:grob-property grob 'direction))
                (xex (ly:stencil-extent sten X))
                (yex (ly:stencil-extent sten Y))
                (lenx (interval-length xex))
                (leny (interval-length yex))
                (yex (ly:stencil-extent sten Y))
                (xtrans (car xex))
                (ytrans (if (> dir 0)(car yex) (cdr yex)))
                (uplist
                 (map pair-to-list
                   (normalize-coords coords lenx (* leny 2) dir))))

           (ly:stencil-translate
            (my-c-p-s uplist used-thick)
            (cons xtrans ytrans)))
         '())))

%{
#(define flare-tie
  (flared-tie '((0 . 0) (0.1 . 0.2) (0.9 . 0.2) (1.0 . 0.0))))
%}

#(define flare-tie
   (flared-tie '((0 . 0) (0.1 . 0.3) (0.9 . 0.3) (1.0 . 0.0))))