Merge_rests_engraver: fix vertical rest positions (issue 334740043 by address@hidden)

[lilypond]

Reviewers: ,

Message:
See
https://lists.gnu.org/archive/html/lilypond-user/2017-10/msg00012.html
for sort of bug report on the user list.

Description:
Merge_rests_engraver: fix vertical rest positions

When used with \magnifyStaff the engraver failed to position merged
rests correctly. Using staff-position instead of Y-offset for vertical
positioning fixes this.

Please review this at https://codereview.appspot.com/334740043/

Affected files (+9, -15 lines):
  M scm/scheme-engravers.scm


Index: scm/scheme-engravers.scm
diff --git a/scm/scheme-engravers.scm b/scm/scheme-engravers.scm
index  
3480610c4caee25a8bb8dd2b97e9accf2147f7d0..c9fc6cd78c715afddc35d6aad17dfd130373bca4  
100644
--- a/scm/scheme-engravers.scm
+++ b/scm/scheme-engravers.scm
@@ -128,20 +128,14 @@ if there were one voice."
   (define (is-single-bar-rest? mmrest)
     (eqv? (ly:grob-property mmrest 'measure-count) 1))

-  (define (is-whole-rest? rest)
-    (eqv? (ly:grob-property rest 'duration-log) 0))
-
-  (define (mmrest-offset mmrest)
+  (define (mmrest-position mmrest)
   "For single measures they should hang from the second line from the top
-  (offset of 1). For longer multimeasure rests they should be centered on  
the
-  middle line (offset of 0).
+  (staff-position of 2). For longer multimeasure rests they should be  
centered on the
+  middle line (staff-position of 0).
   NOTE: For one-line staves full single measure rests should be positioned  
at
   0, but I don't anticipate this engraver's use in that case. No errors are
   given in this case."
-    (if (is-single-bar-rest? mmrest) 1 0))
-
-  (define (rest-offset rest)
-    (if (is-whole-rest? rest) 1 0))
+    (if (is-single-bar-rest? mmrest) 2 0))

   (define (rest-eqv rest-len-prop)
     "Compare rests according the given property"
@@ -158,12 +152,12 @@ if there were one voice."
   (define (merge-mmrests rests)
   "Move all multimeasure rests to the single voice location."
     (if (all-equal rests (rest-eqv 'measure-count))
-      (merge-rests rests mmrest-offset)))
+      (merge-rests rests mmrest-position)))

-  (define (merge-rests rests offset-function)
-    (let ((y-offset (offset-function (car rests))))
+  (define (merge-rests rests position-function)
+    (let ((staff-pos (position-function (car rests))))
       (for-each
-        (lambda (rest) (ly:grob-set-property! rest 'Y-offset y-offset))
+        (lambda (rest) (ly:grob-set-property! rest 'staff-position  
staff-pos))
         rests))
     (for-each
       (lambda (rest) (ly:grob-set-property! rest 'transparent #t))
@@ -217,7 +211,7 @@ if there were one voice."
                 (all-equal durs moment=?)
                 (rests-all-unpitched rests))
               (begin
-                (merge-rests rests rest-offset)
+                (merge-rests rests (lambda (r) 0))
                 ;; 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 curr-mmrests)