Allows for automatic renumbering of measure numbers at volta repeats.

[lilypond.git] / scm / define-music-callbacks.scm

diff --git a/scm/define-music-callbacks.scm b/scm/define-music-callbacks.scm
index 0cbd96b862658c504841edda2af8fb35cb870ecf..06d616f8b014e3cfbb4e57da6811315af3020f07 100644 (file)
--- a/scm/define-music-callbacks.scm
+++ b/scm/define-music-callbacks.scm
@@ -34,6 +34,34 @@ to be used by the sequential-iterator"
          (make-music 'BarCheck
                      'origin location))))
 
+(define (make-volta-set music)
+  (let* ((alts (ly:music-property music 'elements))
+         (lalts (length alts))
+         (times (ly:music-property music 'repeat-count)))
+    (map (lambda (x y)
+           (make-music
+             'SequentialMusic
+             'elements
+               ;; set properties for proper bar numbering
+               (append
+                 (list (make-music 'AlternativeEvent
+                                   'alternative-dir (if (= y 0)
+                                                        -1
+                                                        0)
+                                   'alternative-increment
+                                     (if (= 0 y)
+                                         (1+ (- times
+                                                lalts))
+                                             1)))
+                       (list x)
+                       (if (= y (1- lalts))
+                           (list (make-music 'AlternativeEvent
+                                             'alternative-dir 1
+                                             'alternative-increment 0))
+                           '()))))
+         alts
+         (iota lalts))))
+
 (define (make-ottava-set music)
   "Set context properties for an ottava bracket."
   (let ((octavation (ly:music-property music 'ottava-number)))