+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; fret diagrams
+
+(define-public (determine-frets context grob notes string-numbers)
+ (define (ensure-number a b)
+ (if (number? a)
+ a
+ b))
+(let*
+ ((tunings (ly:context-property context 'stringTunings))
+ (minimum-fret (ensure-number
+ (ly:context-property context 'minimumFret) 0))
+ (max-stretch (ensure-number
+ (ly:context-property context 'maximumFretStretch) 4))
+ (string-frets (determine-frets-mf notes string-numbers
+ minimum-fret max-stretch
+ tunings)))
+
+
+ (set! (ly:grob-property grob 'string-count) (length tunings))
+ (set! (ly:grob-property grob 'string-fret-finger-combinations) string-frets)
+
+ ))
+
+(define-public (determine-frets-mf notes string-numbers
+ minimum-fret max-stretch
+ tunings)
+
+ (define (calc-fret pitch string tuning)
+ (- (ly:pitch-semitones pitch) (list-ref tuning (1- string))))
+
+ (define (note-pitch a)
+ (ly:event-property a 'pitch))
+
+ (define (note-pitch<? a b)
+ (ly:pitch<? (note-pitch a)
+ (note-pitch b)))
+
+ (define (note-finger ev)
+ (let* ((articulations (ly:event-property ev 'articulations))
+ (finger-found #f))
+
+ (map (lambda (art)
+ (let*
+ ((num (ly:event-property art 'digit)))
+
+ (if (and (eq? 'fingering-event (ly:event-property art 'class))
+ (number? num))
+ (set! finger-found num))))
+ articulations)
+
+ finger-found))
+
+ (define (note-string ev)
+ (let* ((articulations (ly:event-property ev 'articulations))
+ (string-found #f))
+
+ (map (lambda (art)
+ (let*
+ ((num (ly:event-property art 'string-number)))
+
+ (if (number? num)
+ (set! string-found num))))
+ articulations)
+
+ string-found))
+
+ (define (del-string string)
+ (if (number? string)
+ (set! free-strings
+ (delete string free-strings))))
+ (define specified-frets '())
+ (define free-strings '())
+
+ (define (close-enough fret)
+ (reduce
+ (lambda (x y)
+ (and x y))
+ #t
+ (map (lambda (specced-fret)
+ (> max-stretch (abs (- fret specced-fret))))
+ specified-frets)
+ ))
+
+ (define (string-qualifies string pitch)
+ (let*
+ ((fret (calc-fret pitch string tunings)))
+
+ (and (>= fret minimum-fret)
+ (close-enough fret))
+
+ ))
+
+ (define string-fret-fingering-tuples '())
+ (define (set-fret note string)
+ (set! string-fret-fingering-tuples
+ (cons (list string
+ (calc-fret (ly:event-property note 'pitch)
+ string tunings)
+ (note-finger note))
+ string-fret-fingering-tuples))
+ (del-string string))
+
+
+ ;;; body.
+ (set! specified-frets
+ (filter identity (map
+ (lambda (note)
+ (if (note-string note)
+ (calc-fret (note-pitch note)
+ (note-string note) tunings)
+ #f))
+ notes)))
+
+
+ (set! free-strings (map 1+ (iota (length tunings))))
+
+ (for-each (lambda (note)
+ (del-string (note-string note)))
+ notes)
+
+
+ (for-each
+ (lambda (note)
+ (if (note-string note)
+ (set-fret note (note-string note))
+ (let*
+ ((string (find (lambda (string) (string-qualifies string
+ (note-pitch note)))
+ (reverse free-strings))))
+ (if string
+ (set-fret note string)
+ (ly:warning "No string for pitch ~a (given frets ~a)" (note-pitch note)
+ specified-frets))
+
+ )))
+ (sort notes note-pitch<?))
+
+ string-fret-fingering-tuples)