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"""Module for high-level communication over the FreeDesktop.org Bus (DBus)
DBus allows you to share and access remote objects between processes
running on the desktop, and also to access system services (such as
the print spool).
To use DBus, first get a Bus object, which provides a connection to one
of a few standard dbus-daemon instances that might be running. From the
Bus you can get a RemoteService. A service is provided by an application or
process connected to the Bus, and represents a set of objects. Once you
have a RemoteService you can get a RemoteObject that implements a specific interface
(an interface is just a standard group of member functions). Then you can call
those member functions directly.
You can think of a complete method call as looking something like:
Bus:SESSION -> Service:org.gnome.Evolution -> Object:/org/gnome/Evolution/Inbox -> Interface: org.gnome.Evolution.MailFolder -> Method: Forward('message1', 'seth@gnome.org')
This communicates over the SESSION Bus to the org.gnome.Evolution process to call the
Forward method of the /org/gnome/Evolution/Inbox object (which provides the
org.gnome.Evolution.MailFolder interface) with two string arguments.
For example, the dbus-daemon itself provides a service and some objects:
# Get a connection to the desktop-wide SESSION bus
bus = dbus.Bus(dbus.Bus.TYPE_SESSION)
# Get the service provided by the dbus-daemon named org.freedesktop.DBus
dbus_service = bus.get_service('org.freedesktop.DBus')
# Get a reference to the desktop bus' standard object, denoted
# by the path /org/freedesktop/DBus. The object /org/freedesktop/DBus
# implements the 'org.freedesktop.DBus' interface
dbus_object = dbus_service.get_object('/org/freedesktop/DBus',
'org.freedesktop.DBus')
# One of the member functions in the org.freedesktop.DBus interface
# is ListServices(), which provides a list of all the other services
# registered on this bus. Call it, and print the list.
print(dbus_object.ListServices())
"""
import dbus_bindings
class Bus:
"""A connection to a DBus daemon.
One of three possible standard buses, the SESSION, SYSTEM,
or ACTIVATION bus
"""
TYPE_SESSION = dbus_bindings.BUS_SESSION
TYPE_SYSTEM = dbus_bindings.BUS_SYSTEM
TYPE_ACTIVATION = dbus_bindings.BUS_ACTIVATION
def __init__(self, bus_type=TYPE_SESSION, glib_mainloop=True):
self._connection = dbus_bindings.bus_get(bus_type)
if (glib_mainloop):
self._connection.setup_with_g_main()
def get_service(self, service_name="org.freedesktop.Broadcast"):
"""Get one of the RemoteServices connected to this Bus. service_name
is just a string of the form 'com.widgetcorp.MyService'
"""
return RemoteService(self._connection, service_name)
def get_connection(self):
"""Get the dbus_bindings.Connection object associated with this Bus"""
return self._connection
class RemoteObject:
"""A remote Object.
A RemoteObject is provided by a RemoteService on a particular Bus. RemoteObjects
have member functions, and can be called like normal Python objects.
"""
def __init__(self, connection, service_name, object_path, interface):
self._connection = connection
self._service_name = service_name
self._object_path = object_path
self._interface = interface
def __getattr__(self, member):
if member == '__call__':
return object.__call__
else:
return RemoteMethod(self._connection, self._service_name,
self._object_path, self._interface, member)
class RemoteMethod:
"""A remote Method.
Typically a member of a RemoteObject. Calls to the
method produce messages that travel over the Bus and are routed
to a specific Service.
"""
def __init__(self, connection, service_name, object_path, interface, method_name):
self._connection = connection
self._service_name = service_name
self._object_path = object_path
self._interface = interface
self._method_name = method_name
def __call__(self, *args):
print ("Going to call object(%s).interface(%s).method(%s)"
% (self._object_path, self._interface, self._method_name))
message = dbus_bindings.MethodCall(self._object_path, self._interface, self._method_name)
message.set_destination(self._service_name)
# Add the arguments to the function
iter = message.get_iter()
for arg in args:
print ("Adding arg %s" % (arg))
print ("Append success is %d" % (iter.append(arg)))
print ("Args now %s" % (message.get_args_list()))
reply_message = self._connection.send_with_reply_and_block(message, 5000)
args_tuple = reply_message.get_args_list()
if (len(args_tuple) == 0):
return
elif (len(args_tuple) == 1):
return args_tuple[0]
else:
return args_tuple
class Service:
"""A base class for exporting your own Services across the Bus
Just inherit from Service, providing the name of your service
(e.g. org.designfu.SampleService).
"""
def __init__(self, service_name, bus=None):
self._service_name = service_name
if bus == None:
# Get the default bus
self._bus = Bus()
else:
self._bus = bus
dbus_bindings.bus_acquire_service(self._bus.get_connection(), service_name)
def get_bus(self):
"""Get the Bus this Service is on"""
return self._bus
class Object:
"""A base class for exporting your own Objects across the Bus.
Just inherit from Object and provide a list of methods to share
across the Bus. These will appear as member functions of your
ServiceObject.
"""
def __init__(self, object_path, methods_to_share, service):
self._object_path = object_path
self._service = service
self._bus = service.get_bus()
self._connection = self._bus.get_connection()
self._method_name_to_method = self._build_method_dictionary(methods_to_share)
self._connection.register_object_path(object_path, self._unregister_cb, self._message_cb)
def _unregister_cb(self, connection):
print ("Unregister")
def _message_cb(self, connection, message):
target_method_name = message.get_member()
target_method = self._method_name_to_method[target_method_name]
args = message.get_args_list()
retval = target_method(*args)
reply = dbus_bindings.MethodReturn(message)
if retval != None:
reply.append(retval)
self._connection.send(reply)
def _build_method_dictionary(self, methods):
dictionary = {}
for method in methods:
if dictionionary.has_key(method.__name__):
print ('WARNING: registering DBus Object methods, already have a method named %s' % (method.__name__)
dictionary[method.__name__] = method
return dictionary
class RemoteService:
"""A remote service providing objects.
A service is typically a process or application that provides
remote objects, but can also be the broadcast service that
receives signals from all applications on the Bus.
"""
def __init__(self, connection, service_name):
self._connection = connection
self._service_name = service_name
def get_object(self, object_path, interface):
"""Get an object provided by this Service that implements a
particular interface. object_path is a string of the form
'/com/widgetcorp/MyService/MyObject1'. interface looks a lot
like a service_name (they're often the same) and is of the form,
'com.widgetcorp.MyInterface', and mostly just defines the
set of member functions that will be present in the object.
"""
return RemoteObject(self._connection, self._service_name, object_path, interface)
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