Use bus_watch_namespace() for more robust monitoring of mpris players appearing or disappearing on the bus.

Approved by Charles Kerr, PS Jenkins bot.

7 files changed, 463 insertions, 217 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index ec43b8f..a28147d 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -20,6 +20,7 @@ vala_init(indicator-sound-service
     --vapidir=${CMAKE_SOURCE_DIR}/vapi/
     --vapidir=.
     --target-glib=2.36
+    --pkg=bus-watcher
 )
 
 vala_add(indicator-sound-service
@@ -47,19 +48,12 @@ vala_add(indicator-sound-service
   media-player-list.vala
   DEPENDS
     media-player
-    mpris2-watcher
+    mpris2-interfaces
 )
 vala_add(indicator-sound-service
   mpris2-interfaces.vala
 )
 vala_add(indicator-sound-service
-  mpris2-watcher.vala
-  DEPENDS
-    media-player
-    mpris2-interfaces
-    freedesktop-interfaces
-)
-vala_add(indicator-sound-service
   freedesktop-interfaces.vala
 )
 vala_add(indicator-sound-service
@@ -89,6 +83,7 @@ set(
   INDICATOR_SOUND_SOURCES
   ${project_VALA_SOURCES}
   ${project_VALA_C}
+  bus-watch-namespace.c
   ${SYMBOLS_PATH}
 )
 
diff --git a/src/Makefile.am.THIS b/src/Makefile.am.THIS
new file mode 100644
index 0000000..1a82a18
--- /dev/null
+++ b/src/Makefile.am.THIS
@@ -0,0 +1,39 @@
+pkglibexec_PROGRAMS = indicator-sound-service
+
+indicator_sound_service_SOURCES = \
+	service.vala \
+	main.vala \
+	volume-control.vala \
+	media-player.vala \
+	media-player-list.vala \
+	mpris2-interfaces.vala \
+	freedesktop-interfaces.vala \
+	sound-menu.vala \
+	bus-watch-namespace.c \
+	bus-watch-namespace.h
+
+indicator_sound_service_VALAFLAGS = \
+  --ccode \
+  --vapidir=$(top_srcdir)/vapi/ \
+  --vapidir=./ \
+  --thread \
+  --pkg config \
+  --pkg gio-2.0 \
+  --pkg gio-unix-2.0 \
+  --pkg libxml-2.0 \
+  --pkg libpulse \
+  --pkg libpulse-mainloop-glib \
+  --pkg bus-watcher \
+  --target-glib=2.36
+
+# -w to disable warnings for vala-generated code
+indicator_sound_service_CFLAGS = $(PULSEAUDIO_CFLAGS) \
+	$(SOUNDSERVICE_CFLAGS) \
+	$(GCONF_CFLAGS) \
+	$(COVERAGE_CFLAGS) \
+	-DLIBEXECDIR=\"$(libexecdir)\" \
+	-w \
+	-DGETTEXT_PACKAGE=\"$(GETTEXT_PACKAGE)\"
+
+indicator_sound_service_LDADD = $(PULSEAUDIO_LIBS) $(SOUNDSERVICE_LIBS) $(GCONF_LIBS)
+indicator_sound_service_LDFLAGS = $(COVERAGE_LDFLAGS)
diff --git a/src/bus-watch-namespace.c b/src/bus-watch-namespace.c
new file mode 100644
index 0000000..f20905c
--- /dev/null
+++ b/src/bus-watch-namespace.c
@@ -0,0 +1,349 @@
+/*
+ * Copyright 2013 Canonical Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author: Lars Uebernickel <lars.uebernickel@canonical.com>
+ */
+
+#include <gio/gio.h>
+#include <string.h>
+#include "bus-watch-namespace.h"
+
+typedef struct
+{
+  guint                     id;
+  gchar                    *name_space;
+  GBusNameAppearedCallback  appeared_handler;
+  GBusNameVanishedCallback  vanished_handler;
+  gpointer                  user_data;
+  GDestroyNotify            user_data_destroy;
+
+  GDBusConnection          *connection;
+  GCancellable             *cancellable;
+  GHashTable               *names;
+  guint                     subscription_id;
+} NamespaceWatcher;
+
+typedef struct
+{
+  NamespaceWatcher *watcher;
+  gchar            *name;
+} GetNameOwnerData;
+
+static guint namespace_watcher_next_id;
+static GHashTable *namespace_watcher_watchers;
+
+static void
+namespace_watcher_stop (gpointer data)
+{
+  NamespaceWatcher *watcher = data;
+
+  g_cancellable_cancel (watcher->cancellable);
+  g_object_unref (watcher->cancellable);
+
+  if (watcher->subscription_id)
+    g_dbus_connection_signal_unsubscribe (watcher->connection, watcher->subscription_id);
+
+  if (watcher->vanished_handler)
+    {
+      GHashTableIter it;
+      const gchar *name;
+
+      g_hash_table_iter_init (&it, watcher->names);
+      while (g_hash_table_iter_next (&it, (gpointer *) &name, NULL))
+        watcher->vanished_handler (watcher->connection, name, watcher->user_data);
+    }
+
+  if (watcher->user_data_destroy)
+    watcher->user_data_destroy (watcher->user_data);
+
+  if (watcher->connection)
+    {
+      g_signal_handlers_disconnect_by_func (watcher->connection, namespace_watcher_stop, watcher);
+      g_object_unref (watcher->connection);
+    }
+
+  g_hash_table_unref (watcher->names);
+
+  g_hash_table_remove (namespace_watcher_watchers, GUINT_TO_POINTER (watcher->id));
+  if (g_hash_table_size (namespace_watcher_watchers) == 0)
+    g_clear_pointer (&namespace_watcher_watchers, g_hash_table_destroy);
+
+  g_free (watcher->name_space);
+
+  g_free (watcher);
+}
+
+static void
+namespace_watcher_name_appeared (NamespaceWatcher *watcher,
+                                 const gchar      *name,
+                                 const gchar      *owner)
+{
+  /* There's a race between NameOwnerChanged signals arriving and the
+   * ListNames/GetNameOwner sequence returning, so this function might
+   * be called more than once for the same name. To ensure that
+   * appeared_handler is only called once for each name, it is only
+   * called when inserting the name into watcher->names (each name is
+   * only inserted once there).
+   */
+  if (g_hash_table_contains (watcher->names, name))
+    return;
+
+  g_hash_table_add (watcher->names, g_strdup (name));
+
+  if (watcher->appeared_handler)
+    watcher->appeared_handler (watcher->connection, name, owner, watcher->user_data);
+}
+
+static void
+namespace_watcher_name_vanished (NamespaceWatcher *watcher,
+                                 const gchar      *name)
+{
+  if (g_hash_table_remove (watcher->names, name) && watcher->vanished_handler)
+    watcher->vanished_handler (watcher->connection, name, watcher->user_data);
+}
+
+static gboolean
+dbus_name_has_namespace (const gchar *name,
+                         const gchar *name_space)
+{
+  gint len_name;
+  gint len_namespace;
+
+  len_name = strlen (name);
+  len_namespace = strlen (name_space);
+
+  if (len_name < len_namespace)
+    return FALSE;
+
+  if (memcmp (name_space, name, len_namespace) != 0)
+    return FALSE;
+
+  return len_namespace == len_name || name[len_namespace] == '.';
+}
+
+static void
+name_owner_changed (GDBusConnection *connection,
+                    const gchar     *sender_name,
+                    const gchar     *object_path,
+                    const gchar     *interface_name,
+                    const gchar     *signal_name,
+                    GVariant        *parameters,
+                    gpointer         user_data)
+{
+  NamespaceWatcher *watcher = user_data;
+  const gchar *name;
+  const gchar *old_owner;
+  const gchar *new_owner;
+
+  g_variant_get (parameters, "(&s&s&s)", &name, &old_owner, &new_owner);
+
+  if (old_owner[0] != '\0')
+    namespace_watcher_name_vanished (watcher, name);
+
+  if (new_owner[0] != '\0')
+    namespace_watcher_name_appeared (watcher, name, new_owner);
+}
+
+static void
+got_name_owner (GObject      *object,
+                GAsyncResult *result,
+                gpointer      user_data)
+{
+  GetNameOwnerData *data = user_data;
+  GError *error = NULL;
+  GVariant *reply;
+  const gchar *owner;
+
+  reply = g_dbus_connection_call_finish (G_DBUS_CONNECTION (object), result, &error);
+
+  if (g_error_matches (error, G_IO_ERROR, G_IO_ERROR_CANCELLED))
+    {
+      g_error_free (error);
+      goto out;
+    }
+
+  if (reply == NULL)
+    {
+      if (!g_error_matches (error, G_DBUS_ERROR, G_DBUS_ERROR_NAME_HAS_NO_OWNER))
+        g_warning ("bus_watch_namespace: error calling org.freedesktop.DBus.GetNameOwner: %s", error->message);
+      g_error_free (error);
+      goto out;
+    }
+
+  g_variant_get (reply, "(&s)", &owner);
+  namespace_watcher_name_appeared (data->watcher, data->name, owner);
+
+  g_variant_unref (reply);
+
+out:
+  g_free (data->name);
+  g_slice_free (GetNameOwnerData, data);
+}
+
+static void
+names_listed (GObject      *object,
+              GAsyncResult *result,
+              gpointer      user_data)
+{
+  NamespaceWatcher *watcher;
+  GError *error = NULL;
+  GVariant *reply;
+  GVariantIter *iter;
+  const gchar *name;
+
+  reply = g_dbus_connection_call_finish (G_DBUS_CONNECTION (object), result, &error);
+
+  if (g_error_matches (error, G_IO_ERROR, G_IO_ERROR_CANCELLED))
+    {
+      g_error_free (error);
+      return;
+    }
+
+  watcher = user_data;
+
+  if (reply == NULL)
+    {
+      g_warning ("bus_watch_namespace: error calling org.freedesktop.DBus.ListNames: %s", error->message);
+      g_error_free (error);
+      return;
+    }
+
+  g_variant_get (reply, "(as)", &iter);
+  while (g_variant_iter_next (iter, "&s", &name))
+    {
+      if (dbus_name_has_namespace (name, watcher->name_space))
+        {
+          GetNameOwnerData *data = g_slice_new (GetNameOwnerData);
+          data->watcher = watcher;
+          data->name = g_strdup (name);
+          g_dbus_connection_call (watcher->connection, "org.freedesktop.DBus", "/",
+                                  "org.freedesktop.DBus", "GetNameOwner",
+                                  g_variant_new ("(s)", name), G_VARIANT_TYPE ("(s)"),
+                                  G_DBUS_CALL_FLAGS_NONE, -1, watcher->cancellable,
+                                  got_name_owner, data);
+        }
+    }
+
+  g_variant_iter_free (iter);
+  g_variant_unref (reply);
+}
+
+static void
+connection_closed (GDBusConnection *connection,
+                   gboolean         remote_peer_vanished,
+                   GError          *error,
+                   gpointer         user_data)
+{
+  NamespaceWatcher *watcher = user_data;
+
+  namespace_watcher_stop (watcher);
+}
+
+static void
+got_bus (GObject      *object,
+         GAsyncResult *result,
+         gpointer      user_data)
+{
+  GDBusConnection *connection;
+  NamespaceWatcher *watcher;
+  GError *error = NULL;
+
+  connection = g_bus_get_finish (result, &error);
+
+  if (g_error_matches (error, G_IO_ERROR, G_IO_ERROR_CANCELLED))
+    {
+      g_error_free (error);
+      return;
+    }
+
+  watcher = user_data;
+
+  if (connection == NULL)
+    {
+      namespace_watcher_stop (watcher);
+      return;
+    }
+
+  watcher->connection = connection;
+  g_signal_connect (watcher->connection, "closed", G_CALLBACK (connection_closed), watcher);
+
+  watcher->subscription_id =
+    g_dbus_connection_signal_subscribe (watcher->connection, "org.freedesktop.DBus",
+                                        "org.freedesktop.DBus", "NameOwnerChanged", "/org/freedesktop/DBus",
+                                        watcher->name_space, G_DBUS_SIGNAL_FLAGS_MATCH_ARG0_NAMESPACE,
+                                        name_owner_changed, watcher, NULL);
+
+  g_dbus_connection_call (watcher->connection, "org.freedesktop.DBus", "/",
+                          "org.freedesktop.DBus", "ListNames", NULL, G_VARIANT_TYPE ("(as)"),
+                          G_DBUS_CALL_FLAGS_NONE, -1, watcher->cancellable,
+                          names_listed, watcher);
+}
+
+guint
+bus_watch_namespace (GBusType                  bus_type,
+                     const gchar              *name_space,
+                     GBusNameAppearedCallback  appeared_handler,
+                     GBusNameVanishedCallback  vanished_handler,
+                     gpointer                  user_data,
+                     GDestroyNotify            user_data_destroy)
+{
+  NamespaceWatcher *watcher;
+
+  /* same rules for interfaces and well-known names */
+  g_return_val_if_fail (name_space != NULL && g_dbus_is_interface_name (name_space), 0);
+  g_return_val_if_fail (appeared_handler || vanished_handler, 0);
+
+  watcher = g_new0 (NamespaceWatcher, 1);
+  watcher->id = namespace_watcher_next_id++;
+  watcher->name_space = g_strdup (name_space);
+  watcher->appeared_handler = appeared_handler;
+  watcher->vanished_handler = vanished_handler;
+  watcher->user_data = user_data;
+  watcher->user_data_destroy = user_data_destroy;
+  watcher->cancellable = g_cancellable_new ();
+  watcher->names = g_hash_table_new_full (g_str_hash, g_str_equal, g_free, NULL);
+
+  if (namespace_watcher_watchers == NULL)
+    namespace_watcher_watchers = g_hash_table_new (g_direct_hash, g_direct_equal);
+  g_hash_table_insert (namespace_watcher_watchers, GUINT_TO_POINTER (watcher->id), watcher);
+
+  g_bus_get (bus_type, watcher->cancellable, got_bus, watcher);
+
+  return watcher->id;
+}
+
+void
+bus_unwatch_namespace (guint id)
+{
+  /* namespace_watcher_stop() might have already removed the watcher
+   * with @id in the case of a connection error. Thus, this function
+   * doesn't warn when @id is absent from the hash table.
+   */
+
+  if (namespace_watcher_watchers)
+    {
+      NamespaceWatcher *watcher;
+
+      watcher = g_hash_table_lookup (namespace_watcher_watchers, GUINT_TO_POINTER (id));
+      if (watcher)
+        {
+          /* make sure vanished() is not called as a result of this function */
+          g_hash_table_remove_all (watcher->names);
+
+          namespace_watcher_stop (watcher);
+        }
+    }
+}
diff --git a/src/bus-watch-namespace.h b/src/bus-watch-namespace.h
new file mode 100644
index 0000000..215f6be
--- /dev/null
+++ b/src/bus-watch-namespace.h
@@ -0,0 +1,34 @@
+/*
+ * Copyright 2013 Canonical Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author: Lars Uebernickel <lars.uebernickel@canonical.com>
+ */
+
+#ifndef __BUS_WATCH_NAMESPACE_H__
+#define __BUS_WATCH_NAMESPACE_H__
+
+#include <gio/gio.h>
+
+guint       bus_watch_namespace         (GBusType                  bus_type,
+                                         const gchar              *name_space,
+                                         GBusNameAppearedCallback  appeared_handler,
+                                         GBusNameVanishedCallback  vanished_handler,
+                                         gpointer                  user_data,
+                                         GDestroyNotify            user_data_destroy);
+
+void        bus_unwatch_namespace       (guint id);
+
+#endif
diff --git a/src/media-player-list.vala b/src/media-player-list.vala
index 6eb5fc9..62badc2 100644
--- a/src/media-player-list.vala
+++ b/src/media-player-list.vala
@@ -26,9 +26,7 @@ public class MediaPlayerList {
 	public MediaPlayerList () {
 		this._players = new HashTable<string, MediaPlayer> (str_hash, str_equal);
 
-		this.mpris_watcher = new Mpris2Watcher ();
-		this.mpris_watcher.client_appeared.connect (this.player_appeared);
-		this.mpris_watcher.client_disappeared.connect (this.player_disappeared);
+		BusWatcher.watch_namespace (BusType.SESSION, "org.mpris.MediaPlayer2", this.player_appeared, this.player_disappeared);
 	}
 
 	/* only valid while the list is not changed */
@@ -113,15 +111,21 @@ public class MediaPlayerList {
 	public signal void player_removed (MediaPlayer player);
 
 	HashTable<string, MediaPlayer> _players;
-	Mpris2Watcher mpris_watcher;
 
-	void player_appeared (string desktop_id, string dbus_name, bool use_playlists) {
-		var player = this.insert (desktop_id);
-		if (player != null)
-			player.attach (dbus_name);
+	void player_appeared (DBusConnection connection, string name, string owner) {
+		try {
+			MprisRoot mpris2_root = Bus.get_proxy_sync (BusType.SESSION, name, MPRIS_MEDIA_PLAYER_PATH);
+
+			var player = this.insert (mpris2_root.DesktopEntry);
+			if (player != null)
+				player.attach (name);
+		}
+		catch (Error e) {
+			warning ("unable to create mpris proxy for '%s': %s", name, e.message);
+		}
 	}
 
-	void player_disappeared (string dbus_name) {
+	void player_disappeared (DBusConnection connection, string dbus_name) {
 		MediaPlayer? player = this._players.find ( (name, player) => {
 			return player.dbus_name == dbus_name;
 		});
diff --git a/src/mpris2-watcher.vala b/src/mpris2-watcher.vala
deleted file mode 100644
index 4a1ab6e..0000000
--- a/src/mpris2-watcher.vala
+++ /dev/null
@@ -1,200 +0,0 @@
-/*
-Copyright 2010 Canonical Ltd.
-
-Authors:
-    Conor Curran <conor.curran@canonical.com>
-
-This program is free software: you can redistribute it and/or modify it 
-under the terms of the GNU General Public License version 3, as published 
-by the Free Software Foundation.
-
-This program is distributed in the hope that it will be useful, but 
-WITHOUT ANY WARRANTY; without even the implied warranties of 
-MERCHANTABILITY, SATISFACTORY QUALITY, 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, see <http://www.gnu.org/licenses/>.
-*/
-
-using Xml;
-
-public class Mpris2Watcher : GLib.Object
-{
-  DBusConnection session_bus;
-
-  public signal void client_appeared ( string desktop_file_name,
-                                       string dbus_name,
-                                       bool use_playlists );
-  public signal void client_disappeared ( string dbus_name );
-
-  public Mpris2Watcher ()
-  {
-  }
-
-  construct
-  {
-    const string match_rule = "type='signal'," +
-                              "sender='org.freedesktop.DBus'," +
-                              "interface='org.freedesktop.DBus'," +
-                              "member='NameOwnerChanged'," +
-                              "path='/org/freedesktop/DBus'," +
-                              "arg0namespace='org.mpris.MediaPlayer2'";
-    try {
-      this.session_bus = Bus.get_sync (BusType.SESSION);
-
-      this.session_bus.call_sync ("org.freedesktop.DBus",
-                                  "/",
-                                  "org.freedesktop.DBus",
-                                  "AddMatch",
-                                  new Variant ("(s)", match_rule),
-                                  VariantType.TUPLE,
-                                  DBusCallFlags.NONE,
-                                  -1);
-
-      this.session_bus.signal_subscribe ("org.freedesktop.DBus",
-                                         "org.freedesktop.DBus",
-                                         "NameOwnerChanged",
-                                         "/org/freedesktop/DBus",
-                                         null,
-                                         DBusSignalFlags.NO_MATCH_RULE,
-                                         this.name_owner_changed);
-
-      this.check_for_active_clients.begin();
-    }
-    catch (GLib.Error e) {
-      warning ("unable to set up name watch for mrpis clients: %s", e.message);
-    }
-  }
-
-  // At startup check to see if there are clients up that we are interested in
-  // More relevant for development and daemon's like mpd. 
-  async void check_for_active_clients()
-  {
-    Variant interfaces;
-
-    try {
-      interfaces = yield this.session_bus.call ("org.freedesktop.DBus",
-                                                "/",
-                                                "org.freedesktop.DBus",
-                                                "ListNames",
-                                                null,
-                                                new VariantType ("(as)"),
-                                                DBusCallFlags.NONE,
-                                                -1);
-    }
-    catch (GLib.Error e) {
-      warning ("unable to search for existing mpris clients: %s ", e.message);
-      return;
-    }
-
-    foreach (var val in interfaces.get_child_value (0)) {
-      var address = (string) val;
-      if (address.has_prefix (MPRIS_PREFIX)){
-        MprisRoot? mpris2_root = this.create_mpris_root(address);
-        if (mpris2_root == null) return;
-        bool use_playlists = this.supports_playlists ( address );
-        client_appeared (mpris2_root.DesktopEntry + ".desktop", address, use_playlists);
-      }
-    }
-  }
-
-  void name_owner_changed (DBusConnection con, string sender, string object_path,
-                                  string interface_name, string signal_name, Variant parameters)
-  {
-    string name, previous_owner, current_owner;
-
-    parameters.get ("(sss)", out name, out previous_owner, out current_owner);
-
-    MprisRoot? mpris2_root = this.create_mpris_root (name);
-    if (mpris2_root == null) return;
-
-    if (previous_owner != "" && current_owner == "") {
-      debug ("Client '%s' gone down", name);
-      client_disappeared (name);
-    }
-    else if (previous_owner == "" && current_owner != "") {
-      debug ("Client '%s' has appeared", name);
-      bool use_playlists = this.supports_playlists ( name );
-      client_appeared (mpris2_root.DesktopEntry + ".desktop", name, use_playlists);
-    }
-  }
-
-  private MprisRoot? create_mpris_root ( string name ){
-    MprisRoot mpris2_root = null;
-    if ( name.has_prefix (MPRIS_PREFIX) ){
-      try {
-        mpris2_root = Bus.get_proxy_sync (  BusType.SESSION,
-                                            name,
-                                            MPRIS_MEDIA_PLAYER_PATH );
-      }
-      catch (IOError e){
-        warning( "Mpris2watcher could not create a root interface: %s",
-                  e.message );
-      }
-    }
-    return mpris2_root;
-  }
-
-  private bool supports_playlists ( string name )
-  {
-    FreeDesktopIntrospectable introspectable;
-
-    try {
-      /* The dbusproxy flag parameter is needed to ensure Banshee does not 
-       blow up. I suspect the issue is that if you
-       try to instantiate a dbus object which does not have any properties 
-       associated  with it, gdbus will attempt to fetch the properties (this is
-       in the documentation) but the banshee mpris dbus object more than likely 
-       causes a crash because it doesn't check for the presence of properties 
-       before attempting to access them.
-      */
-      introspectable = Bus.get_proxy_sync (  BusType.SESSION,
-                                             name,
-                                             MPRIS_MEDIA_PLAYER_PATH, 
-                                             GLib.DBusProxyFlags.DO_NOT_LOAD_PROPERTIES);
-      var results = introspectable.Introspect();
-      return this.parse_interfaces (results);
-    }
-    catch (IOError e){
-      warning( "Could not create an introspectable object: %s",
-                e.message );
-    }
-    return false;
-  }
-
-  private bool parse_interfaces( string interface_info )
-  {
-    //parse the document from path
-    bool result = false;
-    Xml.Doc* xml_doc = Parser.parse_doc (interface_info);
-    if (xml_doc == null) {
-      warning ("Mpris2Watcher - parse-interfaces - failed to instantiate xml doc");
-      return false;
-    }
-    //get the root node. notice the dereferencing operator -> instead of .
-    Xml.Node* root_node = xml_doc->get_root_element ();
-    if (root_node == null) {
-      //free the document manually before throwing because the garbage collector can't work on pointers
-      delete xml_doc;
-      warning ("Mpris2Watcher - the interface info xml is empty");
-      return false;
-    }
-
-    //let's parse those nodes
-    for (Xml.Node* iter = root_node->children; iter != null; iter = iter->next) {
-      //spaces btw. tags are also nodes, discard them
-      if (iter->type != ElementType.ELEMENT_NODE){
-        continue;
-      }
-      Xml.Attr* attributes = iter->properties; //get the node's name    
-      string interface_name = attributes->children->content;
-      debug ( "this dbus object has interface %s ", interface_name );
-      if ( interface_name == MPRIS_PREFIX.concat("Playlists")){
-        result = true;
-      }
-    }
-    delete xml_doc;
-    return result;
-  }  
-}
diff --git a/vapi/bus-watcher.vapi b/vapi/bus-watcher.vapi
new file mode 100644
index 0000000..60dacff
--- /dev/null
+++ b/vapi/bus-watcher.vapi
@@ -0,0 +1,25 @@
+/*
+ * Copyright 2013 Canonical Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; version 3.
+ *
+ * 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors:
+ *      Lars Uebernickel <lars.uebernickel@canonical.com>
+ */
+
+namespace BusWatcher {
+	[CCode (cheader_filename = "bus-watch-namespace.h", cname = "bus_watch_namespace")]
+	public static uint watch_namespace (GLib.BusType bus_type, string name_space,
+			[CCode (delegate_target_pos = 4.9)] owned GLib.BusNameAppearedCallback? name_appeared,
+			[CCode (delegate_target_pos = 4.9)] owned GLib.BusNameVanishedCallback? name_vanished);
+}