Issue 3603: Make \tweak ... Grob equivalent to \override rather than \once \override

This simplifies several uses of tweak for both tweak and override.
When desired, one can use \once \tweak in order to get either tweak or
override-once semantics: in the case of the tweak semantics, \once
will just ignore the contained expression.

diff --git a/ly/music-functions-init.ly b/ly/music-functions-init.ly
index d33bf9da814ae8e2123fa2ab65d50f21bf817f55..02c6ac6531a01775563d6afe61bd37827fb65066 100644 (file)
--- a/ly/music-functions-init.ly
+++ b/ly/music-functions-init.ly
@@ -434,7 +434,7 @@ to the preceding note or rest as a post-event with @code{-}.")
               'automatically-numbered (not mark)
               'text (or mark (make-null-markup))
               'footnote-text footnote)))
-     #{ \tweak footnote-music #mus #item #}))
+     #{ \once \tweak footnote-music #mus #item #}))
 
 grace =
 #(def-grace-function startGraceMusic stopGraceMusic
@@ -495,9 +495,7 @@ If @var{item} is a symbol list of form @code{GrobName} or
 @code{Context.GrobName}, the result is an override for the grob name
 specified by it.  If @var{item} is a music expression, the result is
 the same music expression with an appropriate tweak applied to it.")
-   (if (ly:music? item)
-       #{ \tweak transparent ##t #item #}
-       #{ \override #item . transparent = ##t #}))
+   #{ \tweak transparent ##t #item #})
 
 inStaffSegno =
 #(define-music-function (parser location) ()
@@ -723,21 +721,28 @@ If @var{item} is a symbol list of form @code{GrobName} or
 @code{Context.GrobName}, the result is an override for the grob name
 specified by it.  If @var{item} is a music expression, the result is
 the same music expression with an appropriate tweak applied to it.")
-   (if (ly:music? item)
-       #{ \tweak stencil ##f #item #}
-       #{ \override #item . stencil = ##f #}))
+   #{ \tweak stencil ##f #item #})
 
 once =
 #(define-music-function (parser location music) (ly:music?)
-   (_i "Set @code{once} to @code{#t} on all layout instruction events in @var{music}.")
-   (music-map
-    (lambda (m)
-      (cond ((music-is-of-type? m 'layout-instruction-event)
-            (set! (ly:music-property m 'once) #t))
-           ((ly:duration? (ly:music-property m 'duration))
-            (ly:music-warning m (_ "Cannot apply \\once to timed music"))))
-      m)
-    music))
+   (_i "Set @code{once} to @code{#t} on all layout instruction events
+in @var{music}.  This will complain about music with an actual
+duration.  As a special exception, if @var{music} contains
+@samp{tweaks} it will be silently ignored in order to allow for
+@code{\\once \\tweak} to work as both one-time override and proper
+tweak.")
+   (if (not (pair? (ly:music-property music 'tweaks)))
+       (for-some-music
+        (lambda (m)
+          (cond ((music-is-of-type? m 'layout-instruction-event)
+                 (set! (ly:music-property m 'once) #t)
+                 #t)
+                ((ly:duration? (ly:music-property m 'duration))
+                 (ly:music-warning m (_ "Cannot apply \\once to timed music"))
+                 #t)
+                (else #f)))
+        music))
+   music)
 
 ottava =
 #(define-music-function (parser location octave) (integer?)
@@ -1225,7 +1230,7 @@ appropriate tweak applied.")
        (if (>= total-found 2)
            (helper siblings offsets)
            (offset-control-points (car offsets)))))
-   #{ \tweak control-points #shape-curve #item #})
+   #{ \once \tweak control-points #shape-curve #item #})
 
 shiftDurations =
 #(define-music-function (parser location dur dots arg)
@@ -1453,10 +1458,14 @@ an indirectly created grob (@samp{Accidental} is caused by
 are affected.
 
 As a special case, @var{item} may be a symbol list specifying a grob
-path, in which case @code{\\once\\override} is called on it instead of
+path, in which case @code{\\override} is called on it instead of
 creating tweaked music.  This is mainly useful when using
 @code{\\tweak} as as a component for building other functions.
 
+If this use case would call for @code{\\once \\override} rather than a
+plain @code{\\override}, writing @code{\\once \\tweak @dots{}} can be
+convenient.
+
 @var{prop} can contain additional elements in which case a nested
 property (inside of an alist) is tweaked.")
    (if (ly:music? item)
@@ -1481,7 +1490,7 @@ property (inside of an alist) is tweaked.")
              (b (check-grob-path prop parser location
                                  #:start 2)))
          (if (and a b)
-             #{ \once\override #(append a b) = #value #}
+             #{ \override #(append a b) = #value #}
              (make-music 'Music)))))
 
 undo =