services/presence/psutils, buddy: Track NameOwnerChanged in IP4AddressMonitor

This means Buddy and its subclasses no longer need to care about
NameOwnerChanged at all.

The old code might not have worked anyway, since it was watching for
NameOwnerChanged on the session bus, but invoking NM methods on the system bus.

services/presence/buddy.py

@@ -533,19 +533,12 @@ class GenericOwner(Buddy):
         self._owner = True
 
         self._bus = dbus.SessionBus()
-        self._bus.add_signal_receiver(self._name_owner_changed_cb,
-                                    signal_name="NameOwnerChanged",
-                                    dbus_interface="org.freedesktop.DBus")
 
     def _ip4_address_changed_cb(self, monitor, address):
         """Handle IPv4 address change, set property to generate event"""
         props = {_PROP_IP4_ADDRESS: address}
         self.set_properties(props)
 
-    def _name_owner_changed_cb(self, name, old, new):
-        """Handle D-Bus services we care about appearing and disappearing."""
-        self._ip4_addr_monitor.handle_name_owner_changed(name, old, new)
-
     def get_registered(self):
         """Retrieve whether owner has registered with presence server"""
         return self._registered

services/presence/psutils.py

@@ -53,23 +53,13 @@ class IP4AddressMonitor(gobject.GObject):
     def __init__(self):
         gobject.GObject.__init__(self)
         self._nm_present = False
+        self._nm_has_been_present = False
         self._matches = []
         self._addr = None
         self._nm_obj = None
 
         sys_bus = dbus.SystemBus()
-        bus_object = sys_bus.get_object('org.freedesktop.DBus', '/org/freedesktop/DBus')
-        try:
-            if bus_object.GetNameOwner(NM_SERVICE, dbus_interface='org.freedesktop.DBus'):
-                self._nm_present = True
-        except dbus.DBusException:
-            pass
-
-        if self._nm_present:
-            self._connect_to_nm()
-        else:
-            addr = self._get_address_fallback()
-            self._update_address(addr)
+        self._watch = sys_bus.watch_name_owner(NM_SERVICE, self._nm_owner_cb)
 
     def do_get_property(self, pspec):
         if pspec.name == "address":
@@ -163,20 +153,23 @@ class IP4AddressMonitor(gobject.GObject):
         if new_state == 4: # NM_STATE_DISCONNECTED
             self._update_address(None)
 
-    def handle_name_owner_changed(self, name, old, new):
+    def _nm_owner_cb(self, unique_name):
         """Clear state when NM goes away"""
-        if name != NM_SERVICE:
-            return
-        if (old and len(old)) and (not new and not len(new)):
-            # NM went away
+        if unique_name == '':
+            # NM went away, or isn't there at all
             self._nm_present = False
             for match in self._matches:
                 match.remove()
             self._matches = []
-            self._update_address(None)
-        elif (not old and not len(old)) and (new and len(new)):
+            if self._nm_has_been_present:
+                self._update_address(None)
+            else:
+                addr = self._get_address_fallback()
+                self._update_address(addr)
+        elif not self._nm_present:
             # NM started up
             self._nm_present = True
+            self._nm_has_been_present = True
             self._connect_to_nm()
 
     def _get_iface_address(self, iface):