Fix black rests in secondVoiceStyle

2025-10-23 23:31:28 +02:00
parent 3b0c320839
commit 0b97261553
3 changed files with 92 additions and 1 deletions
--- a/private_includes/base/merge_rests_engraver_override.ily
+++ b/private_includes/base/merge_rests_engraver_override.ily
@@ -0,0 +1,86 @@
+Better_Merge_rests_engraver =
+#(lambda (context)
+  (define (has-one-or-less? lst) (or (null? lst) (null? (cdr lst))))
+  (define (has-at-least-two? lst) (not (has-one-or-less? lst)))
+  (define (all-equal? lst pred)
+    (or (has-one-or-less? lst)
+        (and (pred (car lst) (cadr lst)) (all-equal? (cdr lst) pred))))
+  (define (measure-count-eqv? a b)
+    (eqv?
+     (ly:grob-property a 'measure-count)
+     (ly:grob-property b 'measure-count)))
+
+  (define (rests-all-unpitched? rests)
+    "Returns true when all rests do not override the staff-position grob
+    property. When a rest has a position set we do not want to merge rests at
+    that position."
+    (every (lambda (rest) (null? (ly:grob-property rest 'staff-position))) rests))
+
+  (define (less-by-layer a b)
+    (<
+      (ly:grob-property b 'layer)
+      (ly:grob-property a 'layer)))
+
+  (define (merge-mmrests mmrests)
+    "Move all multimeasure rests to the single voice location."
+    (if (all-equal? mmrests measure-count-eqv?)
+        (begin
+          (for-each
+           (lambda (rest) (ly:grob-set-property! rest 'direction CENTER))
+           mmrests)
+          (for-each
+           (lambda (rest) (ly:grob-set-property! rest 'transparent #t))
+           (cdr (sort mmrests less-by-layer))))))
+
+  (define (merge-rests rests)
+    (for-each
+     (lambda (rest) (ly:grob-set-property! rest 'staff-position 0))
+     rests)
+    (for-each
+     (lambda (rest) (ly:grob-set-property! rest 'transparent #t))
+     (cdr (sort rests less-by-layer))))
+
+  (let ((mmrests '())
+        (rests '())
+        (dots '()))
+    (make-engraver
+     ((start-translation-timestep translator)
+      (set! rests '())
+      (set! mmrests '())
+      (set! dots '()))
+     (acknowledgers
+      ((dot-column-interface engraver grob source-engraver)
+       (if (not (ly:context-property context 'suspendRestMerging #f))
+           (set!
+            dots
+            (append (ly:grob-array->list (ly:grob-object grob 'dots))
+                    dots))))
+      ((rest-interface engraver grob source-engraver)
+       (cond
+        ((ly:context-property context 'suspendRestMerging #f)
+         #f)
+        ((grob::has-interface grob 'multi-measure-rest-interface)
+         (set! mmrests (cons grob mmrests)))
+        (else
+         (set! rests (cons grob rests))))))
+     ((stop-translation-timestep translator)
+      (let (;; get a list of the rests 'duration-lengths, 'duration-log does
+            ;; not take dots into account
+            (durs
+             (map
+              (lambda (g)
+                (ly:duration->moment
+                 (ly:prob-property
+                  (ly:grob-property g 'cause)
+                  'duration)))
+              rests)))
+        (if (and
+             (has-at-least-two? rests)
+             (all-equal? durs equal?)
+             (rests-all-unpitched? rests))
+            (begin
+              (merge-rests rests)
+              ;; ly:grob-suicide! works nicely for dots, as opposed to rests.
+              (if (pair? dots) (for-each ly:grob-suicide! (cdr dots)))))
+        (if (has-at-least-two? mmrests)
+            (merge-mmrests mmrests)))))))