Extend API for activities notifications

Add a new method, called notify_user, to the base
Activity class.

This method can be used by activity developers to
send notifications to the new notification front
end. ie.,

    self.notify_user('New High Score!',
                     'Your score is over 8999')

src/sugar3/activity/activity.py

@@ -82,6 +82,7 @@ from sugar3.graphics.window import Window
 from sugar3.graphics.alert import Alert
 from sugar3.graphics.icon import Icon
 from sugar3.datastore import datastore
+from sugar3.bundle.activitybundle import ActivityBundle
 from gi.repository import SugarExt
 
 _ = lambda msg: gettext.dgettext('sugar-toolkit-gtk3', msg)
@@ -94,6 +95,10 @@ J_DBUS_SERVICE = 'org.laptop.Journal'
 J_DBUS_PATH = '/org/laptop/Journal'
 J_DBUS_INTERFACE = 'org.laptop.Journal'
 
+N_BUS_NAME = 'org.freedesktop.Notifications'
+N_OBJ_PATH = '/org/freedesktop/Notifications'
+N_IFACE_NAME = 'org.freedesktop.Notifications'
+
 CONN_INTERFACE_ACTIVITY_PROPERTIES = 'org.laptop.Telepathy.ActivityProperties'
 
 PREVIEW_SIZE = style.zoom(300), style.zoom(225)
@@ -633,6 +638,21 @@ class Activity(Window, Gtk.Container):
         """
         raise NotImplementedError
 
+    def notify_user(self, summary, body):
+        """
+        Display a notification with the given summary and body.
+        The notification will go under the activities icon in the frame.
+        """
+        bundle = ActivityBundle(get_bundle_path())
+        icon = bundle.get_icon()
+
+        bus = dbus.SessionBus()
+        notify_obj = bus.get_object(N_BUS_NAME, N_OBJ_PATH)
+        notifications = dbus.Interface(notify_obj, N_IFACE_NAME)
+
+        notifications.Notify(self.get_id(), 0, '', summary, body, [],
+                             {'x-sugar-icon-file-name': icon}, -1)
+
     def __save_cb(self):
         logging.debug('Activity.__save_cb')
         self._updating_jobject = False