(ly:music-property arg 'tags)))
arg)
+temporary =
+#(define-music-function (parser location music)
+ (ly:music?)
+ (_i "Make any @code{\\override} in @var{music} replace an existing
+grob property value only temporarily, restoring the old value when a
+corresponding @code{\\revert} is executed. This is achieved by
+clearing the @samp{pop-first} property normally set on
+@code{\\override}s.
+
+An @code{\\override}/@/@code{\\revert} sequence created by using
+@code{\\temporary} and @code{\\undo} on the same music containing
+overrides will cancel out perfectly or cause a@tie{}warning.
+
+Non-property-related music is ignored, warnings are generated for any
+property-changing music that isn't an @code{\\override}.")
+ (define warned #f)
+ (for-some-music
+ (lambda (m)
+ (and (or (music-is-of-type? m 'layout-instruction-event)
+ (music-is-of-type? m 'context-specification)
+ (music-is-of-type? m 'apply-context)
+ (music-is-of-type? m 'time-signature-music))
+ (case (ly:music-property m 'name)
+ ((OverrideProperty)
+ (if (ly:music-property m 'pop-first #f)
+ (set! (ly:music-property m 'pop-first) '()))
+ (if (ly:music-property m 'once #f)
+ (set! (ly:music-property m 'once) '()))
+ #t)
+ ((ContextSpeccedMusic)
+ #f)
+ (else
+ (if (not warned)
+ (begin
+ (ly:input-warning location (_ "Cannot make ~a revertible")
+ (ly:music-property m 'name))
+ (set! warned #t)))
+ #t))))
+ music)
+ music)
+
time =
#(define-music-function (parser location beat-structure fraction)
((number-list? '()) fraction?)
(ly:music?)
(_i "Convert @code{\\override} and @code{\\set} in @var{music} to
@code{\\revert} and @code{\\unset}, respectively. Any reverts and
-unsets already in @var{music} are ignored and not converted.")
+unsets already in @var{music} cause a warning. Non-property-related music is ignored.")
+ (define warned #f)
(let loop
((music music))
(let
((lst
(fold-some-music
(lambda (m) (or (music-is-of-type? m 'layout-instruction-event)
- (music-is-of-type? m 'context-specification)))
+ (music-is-of-type? m 'context-specification)
+ (music-is-of-type? m 'apply-context)
+ (music-is-of-type? m 'time-signature-music)))
(lambda (m overrides)
(case (ly:music-property m 'name)
((OverrideProperty)
'element (loop (ly:music-property m 'element))
'context-type (ly:music-property m 'context-type))
overrides))
- (else overrides)))
+ (else
+ (if (not warned)
+ (begin
+ (ly:input-warning location (_ "Cannot revert ~a")
+ (ly:music-property m 'name))
+ (set! warned #t)))
+ overrides)))
'()
music)))
(cond