From 2c18ae02874d6e5bbb579603f4de64274ba9faaf Mon Sep 17 00:00:00 2001
From: David Kastrup <dak@gnu.org>
Date: Sat, 16 Mar 2013 17:35:53 +0100
Subject: [PATCH] Issue 3249: Make a PostEvents container class for packaging
 several postevents

Previously it was not possible to assign multiple postevents to a
single variable or pass them as the result of an event function.  This
patch wraps multiple events in such situations inside of a PostEvents
post-event and unwraps them when used again in the parser.
---
 lily/parser.yy             | 41 ++++++++++++++++++++++++++++++++++----
 scm/define-music-types.scm |  6 ++++++
 2 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/lily/parser.yy b/lily/parser.yy
index 79560ab1d7..ee413b301f 100644
--- a/lily/parser.yy
+++ b/lily/parser.yy
@@ -596,7 +596,28 @@ identifier_init:
 	| output_def
 	| context_def_spec_block
 	| music_assign
-	| post_event_nofinger
+	| post_event_nofinger post_events
+	{
+		$$ = scm_reverse_x ($2, SCM_EOL);
+		if (Music *m = unsmob_music ($1))
+		{
+			if (m->is_mus_type ("post-event-wrapper"))
+				$$ = scm_append
+					(scm_list_2 (m->get_property ("elements"),
+						     $$));
+			else
+				$$ = scm_cons ($1, $$);
+		}
+		if (scm_is_pair ($$)
+		    && scm_is_null (scm_cdr ($$)))
+			$$ = scm_car ($$);
+		else
+		{
+			Music * m = MY_MAKE_MUSIC ("PostEvents", @$);
+			m->set_property ("elements", $$);
+			$$ = m->unprotect ();
+		}
+	}
 	| number_expression
 	| FRACTION
 	| string
@@ -2490,9 +2511,21 @@ post_events:
 		$$ = SCM_EOL;
 	}
 	| post_events post_event {
-		if (unsmob_music ($2)) {
-			unsmob_music ($2)->set_spot (@2);
-			$$ = scm_cons ($2, $$);
+		$$ = $1;
+		if (Music *m = unsmob_music ($2))
+		{
+			if (m->is_mus_type ("post-event-wrapper"))
+			{
+				for (SCM p = m->get_property ("elements");
+				     scm_is_pair (p);
+				     p = scm_cdr (p))
+				{
+					$$ = scm_cons (scm_car (p), $$);
+				}
+			} else {
+				m->set_spot (@2);
+				$$ = scm_cons ($2, $$);
+			}
 		}
 	}
 	;
diff --git a/scm/define-music-types.scm b/scm/define-music-types.scm
index 6d40ce0f56..1090d332b4 100644
--- a/scm/define-music-types.scm
+++ b/scm/define-music-types.scm
@@ -437,6 +437,12 @@ Syntax: @var{note}@code{\\(} and @var{note}@code{\\)}")
 	(types . (general-music post-event span-event event phrasing-slur-event))
 	))
 
+    (PostEvents
+     . ((description . "Container for several postevents.
+
+This can be used to package several events into a single one.  Should not be seen outside of the parser.")
+        (types . (post-event post-event-wrapper))))
+
     (PropertySet
      . ((description . "Set a context property.
 
-- 
2.39.5