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;;;; This file is part of LilyPond, the GNU music typesetter.
;;;;
;;;; Copyright (C) 2000--2020 Jan Nieuwenhuizen <[email protected]>
;;;;
;;;; LilyPond is free software: you can redistribute it and/or modify
;;;; it under the terms of the GNU General Public License as published by
;;;; the Free Software Foundation, either version 3 of the License, or
;;;; (at your option) any later version.
;;;;
;;;; LilyPond is distributed in the hope that it will be useful,
;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;;;; GNU General Public License for more details.
;;;;
;;;; You should have received a copy of the GNU General Public License
;;;; along with LilyPond. If not, see <http://www.gnu.org/licenses/>.
;; Determine whether an auto beam should be extended to the right
;; of the current stem. We start anywhere, except mid-measure in
;; 3/4 time. We end according to the follwing rules, in order of
;; decreasing priority:
;;
;; 1. end <type>
;; 2. end <greater type>
;; 3. if 1-2 not specified, end at beatStructure intervals
;;
;; Rationale:
;;
;; [user override]
;; 1. override for specific duration type
;; 2. overrides apply to shorter durations
;;
;; defined in scm/time-signature-settings.scm:
;; 1. Default grouping for common time signatures
(define-public (default-auto-beam-check context dir measure-pos test-beam)
(define (get name default)
(let ((value (ly:context-property context name)))
(if (not (null? value)) value default)))
(define (ending-moments group-list base-length)
(let ((beat 0))
(map-in-order (lambda (x)
(set! beat (+ beat x))
(* base-length beat))
group-list)))
(define (larger-setting type sorted-alist)
(assoc type sorted-alist <=))
(define (beat-end? moment beat-endings)
(pair? (memv moment beat-endings))) ;; member returns a list if found, not #t
;; Start of actual auto-beam test routine
;;
;;
;; Don't start auto beams on grace notes
(and (or (zero? (ly:moment-grace (ly:context-now context)))
(!= dir START))
(let* ((base-length (cond ((get 'baseMoment #f) => ly:moment-main)
(else 1/4)))
(measure-length (cond ((get 'measureLength #f) => ly:moment-main)
(else 1)))
(time-signature-fraction
(get 'timeSignatureFraction '(4 . 4)))
(beat-structure (get 'beatStructure '(1 1 1 1)))
(beat-endings (ending-moments beat-structure base-length))
(exceptions (sort (map
(lambda (a)
(if (pair? (car a))
(cons (/ (caar a) (cdar a))
(cdr a))
a))
(assoc-get 'end
(get 'beamExceptions '())
'()))
car<))
(function (if (= dir START) 'begin 'end))
(beam-half-measure (get 'beamHalfMeasure #t))
(type (ly:moment-main test-beam))
(non-grace (ly:moment-main measure-pos))
(pos (if (negative? non-grace)
(+ measure-length non-grace)
non-grace))
(type-grouping (assoc-get type exceptions '()))
(default-rule (and (null? type-grouping)
(larger-setting type exceptions)))
(default-grouping (and default-rule (cdr default-rule)))
(default-beat-length (and default-rule (car default-rule)))
(exception-grouping (if (null? type-grouping)
default-grouping
type-grouping))
(grouping-moment (if (null? type-grouping)
default-beat-length
type))
(exception-moments (and exception-grouping
(ending-moments
exception-grouping grouping-moment))))
(if (= dir START)
;; Start rules -- #t if beam is allowed to start
(or beam-half-measure ;; Start anywhere, but option for mid-measure
(not (= (+ pos pos) measure-length))
(not (= 3 (car time-signature-fraction))) ;; in triple meter
(not (= (denominator type) ;; when the beamed note is 1/6 of a measure
(* 2 (cdr time-signature-fraction)))))
;; End rules -- #t if beam is required to end
(or (zero? pos) ;; end at measure beginning
(if exception-grouping
(beat-end? pos exception-moments) ;; check exception rule
(beat-end? pos beat-endings))))))) ;; no exception, so check beat ending
(define-public (extract-beam-exceptions music)
"Creates a value useful for setting @code{beamExceptions} from @var{music}."
(define (car> a b) (> (car a) (car b)))
(define (beatify! lst)
;; takes a collection of end points, sorts them, and returns the
;; non-zero differences as beaming pattern
(let ((s (sort-list! lst <)))
(remove! zero?
(map - s (cons 0 s)))))
(let ((res '()))
(let analyze ((m (unfold-repeats-fully (event-chord-reduce music)))
(pos 0))
;; enter beam ends from m starting at pos into res, return new pos
(cond ((music-is-of-type? m 'bar-check) 0)
((music-is-of-type? m 'simultaneous-music)
(fold (lambda (m prev) (max (analyze m pos) prev))
pos
(ly:music-property m 'elements)))
((not (music-is-of-type? m 'rhythmic-event))
(let ((elt (ly:music-property m 'element)))
(fold analyze
(if (ly:music? elt) (analyze elt pos) pos)
(ly:music-property m 'elements))))
;; Have rhythmic event.
((any
(lambda (art)
(and (music-is-of-type? art 'beam-event)
(= (ly:music-property art 'span-direction START) STOP)))
(ly:music-property m 'articulations))
(let* ((len (duration-length (ly:music-property m 'duration)))
(pos (+ pos len))
(ass (assv len res)))
(cond ((or (zero? len) (not (integer? (/ pos len))))
(ly:warning m (_ "Beam end fits no pattern")))
(ass
(set-cdr! ass (cons (/ pos len) (cdr ass))))
(else
(set! res (cons (list len (/ pos len)) res))))
pos))
(else
(+ pos (duration-length (ly:music-property m 'duration))))))
;; takes the output from the loop, generates actual beam exceptions
(list
(cons 'end
(map!
(lambda (l)
(cons (car l)
(beatify! (cdr l))))
(sort-list! res car>))))))
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