Quintenzirkel/2

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#(define (st-rot stencil myangle)
   ;; just for shortening the code
   (ly:stencil-rotate stencil myangle 0 0))

#(define (x-width mystencil)
   (let* ((x-ext (ly:stencil-extent mystencil X)))
     (- (cdr x-ext) (car x-ext))))

#(define (y-width mystencil)
   (let* ((y-ext (ly:stencil-extent mystencil Y)))
     (- (cdr y-ext) (car y-ext))))

#(define (bogen winkel)
   (* ( / winkel 180) PI))

#(define (kreis-punkt radius winkel)
   ;; this function returns the coordinates of a point on a circumference
   ;; as pair depending on radius and angle
   ;; like a clock: start at midnight ;-)
   ;; winkel = angle (in degrees)
   ;; '(x . y)
   (let* ((wiboma (bogen winkel)) ;; calculate angle as radian measure
           (x-sin (sin wiboma))
           (y-cos (cos wiboma))
           (x-cor (* x-sin radius))
           (y-cor (* y-cos radius)))
     (cons x-cor y-cor)))

#(define (mittel-punkt stencil)
   ;; returns the coordinates of the middle of the stencil als pair
   ;; '( x-middle . y-middle)
   (let*
    ((x-li (car (ly:stencil-extent stencil X)))
     (x-re (cdr (ly:stencil-extent stencil X)))
     (y-li (car (ly:stencil-extent stencil Y)))
     (y-re (cdr (ly:stencil-extent stencil Y))))
    (cons (/ (+ x-li x-re) 2) (/ (+ y-li y-re) 2))))

#(define (move-to-circle radius winkel stencil)
   ;; move a stencil to the edge of a cirle
   ;; depending on radius and angle
   ;; the arithmetic middle of the stenil coordinates is the reference point
   ;; which is moved with its `mittel-punkt' to `kreis-punkt'
   (let* ((mittel (mittel-punkt stencil))
          (mittel-x (car mittel))
          (mittel-y (cdr mittel))
          (kreis (kreis-punkt radius winkel))
          (kreis-x (car kreis))
          (kreis-y (cdr kreis)))
     (ly:stencil-translate stencil
       (cons
        (- kreis-x mittel-x)
        (- kreis-y mittel-y)))))

#(define-markup-command (move-markup layout props mymark radius winkel)
   (markup? number? number?)
   (move-to-circle radius winkel (interpret-markup layout props mymark)))

#(define (move-to-circle-x radius winkel stencil delta)
   ;; move stencil down (at six)
   ;; winkel=0:  left aligned
   ;; winkel<>0: right aligned
   ;; just for Fis/Ges Dur needed
   ;; two scales at six
   (let* ((mittel (mittel-punkt stencil))
          (mittel-x (car mittel))
          (mittel-y (cdr mittel))
          (kreis (kreis-punkt radius winkel))
          (kreis-x (car kreis))
          (kreis-y (cdr kreis)))
     (if (= winkel 0)
         (ly:stencil-translate stencil
           (cons
            (+ (* -2 mittel-x) delta)
            (* radius -1)))
         (ly:stencil-translate stencil
           (cons
            delta
            (* radius -1))))))

#(define-markup-command (move-markup-x layout props mymark radius winkel delta)
   (markup? number? number? number?)
   (move-to-circle-x radius winkel (interpret-markup layout props mymark) delta))

#(define-markup-command (move-and-scale layout props mymark faktor x-offset)
   (markup? number? number?)
   (ly:stencil-translate
    (ly:stencil-scale
     (interpret-markup layout props mymark)
     faktor faktor)
    (cons x-offset 0))
   )

#(define QC-radius 30) %% inner radius of the cirle
#(define Abstand 1.45)  %% try what looks best
#(define ticker-len 1.07)
#(define outer-radius (* QC-radius Abstand)) %% outer radius
#(define Dur-radius (* QC-radius 1.16))  %% try what looks best
#(define moll-radius (/ QC-radius 1.3)) %% try what looks best

#(define ticker-line
   ;; this is the archetype of the ticker lines
   ;; that connect the majors with the minors
   ;; I combine six of them rotated at 30, 60, ... degrees
   (make-filled-box-stencil (cons -0.1 0.1)
     (cons (* -1 QC-radius ticker-len) (* QC-radius ticker-len))))