Alter dbus.server.Server API to have pseudo-signals

By either appending to a list of callbacks, or subclassing and providing a
method, you can be notified when connections are added or removed.
Inspired by the DBusServer patch from Huang Peng.

2 files changed, 57 insertions, 15 deletions

diff --git a/dbus/server.py b/dbus/server.py
index 2cf11c8..d690e1a 100644
--- a/dbus/server.py
+++ b/dbus/server.py
@@ -32,7 +32,8 @@ class Server(_Server):
     other applications.
 
     This class is not useful to instantiate directly: you must subclass it and
-    provide an implementation of the _on_new_connection method.
+    either extend the method connection_added, or append to the
+    list on_connection_added.
 
     :Since: 0.82.5
     """
@@ -57,19 +58,58 @@ class Server(_Server):
         return super(Server, cls).__new__(cls, address, connection_class,
                 mainloop, auth_mechanisms)
 
+    def __init__(self, *args, **kwargs):
+
+        self.__connections = {}
+
+        self.on_connection_added = []
+        """A list of callbacks to invoke when a connection is added.
+        They receive two arguments: this Server and the new Connection."""
+
+        self.on_connection_removed = []
+        """A list of callbacks to invoke when a connection becomes
+        disconnected. They receive two arguments: this Server and the removed
+        Connection."""
+
+    # This method name is hard-coded in _dbus_bindings._Server.
+    # This is not public API.
     def _on_new_connection(self, conn):
+        conn.call_on_disconnection(self.connection_removed)
+        self.connection_added(conn)
+
+    def connection_added(self, conn):
         """Respond to the creation of a new Connection.
 
+        This base-class implementation just invokes the callbacks in
+        the on_connection_added attribute.
+
         :Parameters:
             `conn` : dbus.connection.Connection
-                A D-Bus connection.
+                A D-Bus connection which has just been added.
 
                 The type of this parameter is whatever was passed
                 to the Server constructor as the ``connection_class``.
         """
-        raise NotImplementedError('Subclasses of Server must implement '
-                '_on_new_connection')
+        if self.on_connection_added:
+            for cb in self.on_connection_added:
+                cb(conn)
+
+    def connection_removed(self, conn):
+        """Respond to the disconnection of a Connection.
 
+        This base-class implementation just invokes the callbacks in
+        the on_connection_removed attribute.
+
+        :Parameters:
+            `conn` : dbus.connection.Connection
+                A D-Bus connection which has just become disconnected.
+
+                The type of this parameter is whatever was passed
+                to the Server constructor as the ``connection_class``.
+        """
+        if self.on_connection_removed:
+            for cb in self.on_connection_removed:
+                cb(conn)
 
     address      = property(_Server.get_address)
     id           = property(_Server.get_id)
diff --git a/test/test-server.py b/test/test-server.py
index aef27c9..b909d84 100755
--- a/test/test-server.py
+++ b/test/test-server.py
@@ -26,22 +26,23 @@ class TestService(dbus.service.Object):
 
         return ''.join(text)
 
-class TestServer(dbus.server.Server):
-    def __init__(self, *args, **kwargs):
-        super(TestServer, self).__init__(*args, **kwargs)
-        self.__connections = list()
-
-    def _on_new_connection(self, conn):
-        print 'new connection: %r' % conn
-        self.__connections.append(conn)
-        TestService(conn)
-
 pin, pout = os.pipe()
 child = os.fork()
 
 if 0 == child:
     DBusGMainLoop(set_as_default=True)
-    server = TestServer('unix:tmpdir=/tmp')
+    server = dbus.server.Server('unix:tmpdir=/tmp')
+
+    def new_connection(conn):
+        print "new connection, %r" % conn
+        TestService(conn)
+
+    def connection_gone(conn):
+        print "goodbye, %r" % conn
+
+    # Instantiate a TestService every time a connection is created
+    server.on_connection_added.append(new_connection)
+    server.on_connection_removed.append(connection_gone)
 
     os.write(pout, server.address)
     os.close(pout)
@@ -72,3 +73,4 @@ else:
         text = line.strip()
         print 'reverse(%s): %s' % (text, object.reverse(text))
 
+    client.close()