1 ;;;; This file is part of LilyPond, the GNU music typesetter.
3 ;;;; Copyright (C) 2000--2012 Jan Nieuwenhuizen <janneke@gnu.org>
5 ;;;; LilyPond is free software: you can redistribute it and/or modify
6 ;;;; it under the terms of the GNU General Public License as published by
7 ;;;; the Free Software Foundation, either version 3 of the License, or
8 ;;;; (at your option) any later version.
10 ;;;; LilyPond is distributed in the hope that it will be useful,
11 ;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
12 ;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 ;;;; GNU General Public License for more details.
15 ;;;; You should have received a copy of the GNU General Public License
16 ;;;; along with LilyPond. If not, see <http://www.gnu.org/licenses/>.
18 ;; Determine whether an auto beam should be extended to the right
19 ;; of the current stem. In general, we start anywhere except on
20 ;; the last note of a beat. We end according to the follwing rules,
21 ;; in order of decreasing priority:
24 ;; 2. end <greater type>
25 ;; 3. if 1-2 not specified, end at beatStructure intervals
30 ;; 1. override for specific duration type
31 ;; 2. overrides apply to shorter durations
33 ;; defined in scm/time-signature-settings.scm:
34 ;; 1. Default grouping for common time signatures
36 (define-public (default-auto-beam-check context dir measure-pos test-beam)
37 (define (get name default)
38 (let ((value (ly:context-property context name)))
39 (if (not (null? value)) value default)))
41 (define (beaming<? a b)
42 (ly:moment<? (fraction->moment (car a))
43 (fraction->moment (car b))))
45 (define (ending-moments group-list start-beat base-moment)
46 (if (null? group-list)
48 (let ((new-start (+ start-beat (car group-list))))
49 (cons (ly:moment-mul (ly:make-moment new-start 1) base-moment)
50 (ending-moments (cdr group-list) new-start base-moment)))))
52 (define (larger-setting test-beam sorted-alist)
53 (if (null? sorted-alist)
55 (let* ((first-key (caar sorted-alist))
56 (first-moment (fraction->moment first-key)))
57 (if (moment<=? test-beam first-moment)
59 (larger-setting test-beam (cdr sorted-alist))))))
61 (define (beat-end? moment beat-structure)
62 (pair? (member moment beat-structure))) ;; member returns a list if found, not #t
64 (define (use-special-3-4-rules? fraction base-moment exceptions)
65 "Should we use special 3/4 time signature beaming rules?"
66 (and (equal? fraction '(3 . 4))
67 (equal? base-moment (ly:make-moment 1 4))
68 (null? (assoc-get '(1 . 8) exceptions '()))))
70 ;; Start of actual auto-beam test routine
73 ;; Don't start auto beams on grace notes
74 (if (and (!= (ly:moment-grace-numerator (ly:context-now context)) 0)
77 (let* ((base-moment (get 'baseMoment (ly:make-moment 1 4)))
78 (measure-length (get 'measureLength (ly:make-moment 1 1)))
79 (time-signature-fraction
80 (get 'timeSignatureFraction '(4 . 4)))
81 (beat-structure (get 'beatStructure '(1 1 1 1)))
82 (beat-endings (ending-moments beat-structure 0 base-moment))
83 (exceptions (sort (assoc-get 'end
84 (get 'beamExceptions '())
87 (function (if (= dir START) 'begin 'end))
88 (beam-whole-measure (get 'beamWholeMeasure #t))
89 (beam-half-measure (get 'beamHalfMeasure #f))
90 (type (moment->fraction test-beam))
91 (non-grace (ly:make-moment
92 (ly:moment-main-numerator measure-pos)
93 (ly:moment-main-denominator measure-pos)))
94 (pos (if (ly:moment<? non-grace ZERO-MOMENT)
95 (ly:moment-add measure-length non-grace)
97 (type-grouping (assoc-get type exceptions '()))
98 (default-rule (if (null? type-grouping)
99 (larger-setting test-beam exceptions)
101 (default-grouping (if (pair? default-rule)
104 (default-beat-length (if (pair? default-rule)
107 (exception-grouping (if (null? type-grouping)
110 (grouping-moment (if (null? type-grouping)
111 (fraction->moment default-beat-length)
113 (exception-moments (ending-moments
114 exception-grouping 0 grouping-moment)))
117 ;; Start rules -- start anywhere unless 3/4 with default rules
118 ;; #t if beam is to start
119 (or (not (use-special-3-4-rules?
120 time-signature-fraction
122 exceptions)) ;; start anywhere if not default 3/4
123 (= (ly:moment-main-numerator pos) 0) ;; start at beginning of measure
124 (and beam-half-measure
125 (equal? type '(1 . 8))
126 (equal? pos (ly:make-moment 3 8))) ;; start at mid-measure if 1/8 note beam
127 (beat-end? pos beat-endings) ;; start if at start of beat
128 (and (not (equal? test-beam base-moment)) ;; is beat split?
129 (not (beat-end? (ly:moment-add pos test-beam)
130 beat-endings)))) ;; will this note end the beat
131 ;; End rules -- #t if beam is to end
132 (or (= (ly:moment-main-numerator pos) 0) ;; end at measure beginning
133 (if (use-special-3-4-rules?
134 time-signature-fraction
137 ;; special rule for default 3/4 beaming
138 (if (and (equal? type '(1 . 8))
139 (or beam-whole-measure
140 (and beam-half-measure
141 (not (equal? pos (ly:make-moment 3 8))))))
143 (beat-end? pos beat-endings))
144 ;; rules for all other cases -- check for applicable exception
145 (if (null? exception-grouping)
146 (beat-end? pos beat-endings) ;; no exception, so check beat ending
147 (member pos exception-moments)))))))) ;; check exception rule