Playlist: refresh new tags after database update

Fixes regression from commit e96779d.

Makefile.am

@@ -178,6 +178,7 @@ src_mpd_SOURCES = \
 	src/PlaylistVector.cxx src/PlaylistVector.hxx \
 	src/PlaylistInfo.hxx \
 	src/PlaylistDatabase.cxx src/PlaylistDatabase.hxx \
+	src/PlaylistUpdate.cxx \
 	src/IdTable.hxx \
 	src/Queue.cxx src/Queue.hxx \
 	src/QueuePrint.cxx src/QueuePrint.hxx \

src/Partition.cxx

@@ -24,7 +24,7 @@
 void
 Partition::DatabaseModified()
 {
-	playlist.FullIncrementVersions();
+	playlist.DatabaseModified();
 }
 
 void

src/Playlist.cxx

@@ -28,13 +28,6 @@
 
 #include <assert.h>
 
-void
-playlist::FullIncrementVersions()
-{
-	queue.ModifyAll();
-	idle_add(IDLE_PLAYLIST);
-}
-
 void
 playlist::TagModified(Song &&song)
 {

src/Playlist.hxx

@@ -135,7 +135,10 @@ public:
 	 */
 	void TagModified(Song &&song);
 
-	void FullIncrementVersions();
+	/**
+	 * The database has been modified.  Pull all updates.
+	 */
+	void DatabaseModified();
 
 	PlaylistResult AppendSong(player_control &pc,
 				  Song *song,

src/PlaylistUpdate.cxx

@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2003-2013 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "Playlist.hxx"
+#include "DatabaseGlue.hxx"
+#include "DatabasePlugin.hxx"
+#include "Song.hxx"
+#include "tag/Tag.hxx"
+#include "Idle.hxx"
+#include "util/Error.hxx"
+
+static bool
+UpdatePlaylistSong(const Database &db, Song &song)
+{
+	if (!song.IsInDatabase() || !song.IsDetached())
+		/* only update Songs instances that are "detached"
+		   from the Database */
+		return false;
+
+	Song *original = db.GetSong(song.uri, IgnoreError());
+	if (original == nullptr)
+		/* not found - shouldn't happen, because the update
+		   thread should ensure that all stale Song instances
+		   have been purged */
+		return false;
+
+	if (original->mtime == song.mtime) {
+		/* not modified */
+		db.ReturnSong(original);
+		return false;
+	}
+
+	song.mtime = original->mtime;
+
+	if (original->tag != nullptr)
+		song.ReplaceTag(Tag(*original->tag));
+
+	db.ReturnSong(original);
+	return true;
+}
+
+void
+playlist::DatabaseModified()
+{
+	const Database *db = GetDatabase();
+	if (db == nullptr)
+		/* how can this ever happen? */
+		return;
+
+	bool modified = false;
+
+	for (unsigned i = 0, n = queue.GetLength(); i != n; ++i) {
+		if (UpdatePlaylistSong(*db, queue.Get(i))) {
+			queue.ModifyAtPosition(i);
+			modified = true;
+		}
+	}
+
+	if (modified) {
+		queue.IncrementVersion();
+		idle_add(IDLE_PLAYLIST);
+	}
+}

src/Queue.cxx

@@ -85,15 +85,6 @@ queue::ModifyAtOrder(unsigned _order)
 	ModifyAtPosition(position);
 }
 
-void
-queue::ModifyAll()
-{
-	for (unsigned i = 0; i < length; i++)
-		items[i].version = version;
-
-	IncrementVersion();
-}
-
 unsigned
 queue::Append(Song *song, uint8_t priority)
 {

src/Queue.hxx

@@ -258,11 +258,6 @@ struct queue {
 	 */
 	void ModifyAtOrder(unsigned order);
 
-	/**
-	 * Marks all songs as "modified" and increments the version number.
-	 */
-	void ModifyAll();
-
 	/**
 	 * Appends a song to the queue and returns its position.  Prior to
 	 * that, the caller must check if the queue is already full.