From d5ec16b680c1e411b3adf27eadfde3add7b59bca Mon Sep 17 00:00:00 2001
From: David Kastrup <dak@gnu.org>
Date: Tue, 1 Nov 2011 18:51:40 +0100
Subject: [PATCH] Implement \once as music function able to operate on complex
 stuff.

---
 lily/lily-lexer.cc             |  1 -
 lily/parser.yy                 |  6 +-----
 ly/music-functions-init.ly     | 12 ++++++++++++
 scm/ly-syntax-constructors.scm |  5 ++---
 4 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/lily/lily-lexer.cc b/lily/lily-lexer.cc
index 1298604f12..b19639b579 100644
--- a/lily/lily-lexer.cc
+++ b/lily/lily-lexer.cc
@@ -72,7 +72,6 @@ static Keyword_ent the_key_tab[]
   {"name", NAME},
   {"new", NEWCONTEXT},
   {"notemode", NOTEMODE},
-  {"once", ONCE},
   {"override", OVERRIDE},
   {"paper", PAPER},
   {"remove", REMOVE},
diff --git a/lily/parser.yy b/lily/parser.yy
index 0adb95c2f5..1e693c89c0 100644
--- a/lily/parser.yy
+++ b/lily/parser.yy
@@ -229,7 +229,6 @@ void set_music_properties (Music *p, SCM a);
 %token MIDI "\\midi"
 %token NAME "\\name"
 %token NOTEMODE "\\notemode"
-%token ONCE "\\once"
 %token OVERRIDE "\\override"
 %token PAPER "\\paper"
 %token REMOVE "\\remove"
@@ -1614,10 +1613,7 @@ simple_music_property_def:
 
 music_property_def:
 	simple_music_property_def {
-		$$ = LOWLEVEL_MAKE_SYNTAX (ly_lily_module_constant ("property-operation"), scm_cons (PARSER->self_scm (), scm_cons2 (make_input (@$), SCM_BOOL_F, $1)));
-	}
-	| ONCE simple_music_property_def {
-		$$ = LOWLEVEL_MAKE_SYNTAX (ly_lily_module_constant ("property-operation"), scm_cons (PARSER->self_scm (), scm_cons2 (make_input (@$), SCM_BOOL_T, $2)));
+		$$ = LOWLEVEL_MAKE_SYNTAX (ly_lily_module_constant ("property-operation"), scm_cons2 (PARSER->self_scm (), make_input (@$), $1));
 	}
 	;
 
diff --git a/ly/music-functions-init.ly b/ly/music-functions-init.ly
index 185ee7be38..5dad573ac0 100644
--- a/ly/music-functions-init.ly
+++ b/ly/music-functions-init.ly
@@ -578,6 +578,18 @@ octaveCheck =
    (make-music 'RelativeOctaveCheck
                'pitch pitch))
 
+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))
+
 ottava =
 #(define-music-function (parser location octave) (integer?)
    (_i "Set the octavation.")
diff --git a/scm/ly-syntax-constructors.scm b/scm/ly-syntax-constructors.scm
index 841ad92e97..ee6140ab1f 100644
--- a/scm/ly-syntax-constructors.scm
+++ b/scm/ly-syntax-constructors.scm
@@ -177,7 +177,7 @@ into a @code{MultiMeasureTextEvent}."
     (if create-new (set! (ly:music-property csm 'create-new) #t))
     csm))
 
-(define-ly-syntax (property-operation parser location once ctx music-type symbol . args)
+(define-ly-syntax (property-operation parser location ctx music-type symbol . args)
   (let* ((props (case music-type
 		  ((PropertySet) (list 'value (car args)))
 		  ((PropertyUnset) '())
@@ -191,11 +191,10 @@ into a @code{MultiMeasureTextEvent}."
 		       (list 'grob-property-path (car args))
 		       (list 'grob-property-path args)))
 		  (else (ly:error (_ "Invalid property operation ~a") music-type))))
-	 (oprops (if once (cons* 'once once props) props))
 	 (m (apply make-music music-type
 		   'symbol symbol
 		   'origin location
-		   oprops)))
+		   props)))
     (make-music 'ContextSpeccedMusic
 		'element m
 		'context-type ctx
-- 
2.39.5