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I'm trying to write a desktop environment that supports the global menu Before I get started with my main task In PyQt I'm trying to get the dbus code to work with QtDBus as a proof of concept. Here's the pretty-printed output and method signature I got from d-feet:

GetMenus() -> (Array of [Struct of (Uint32,String,Object Path)] menus)

[(60817412L, u':1.155', '/com/canonical/menu/3A00004'),
 (58725289L, u':1.151', '/com/canonical/menu/38013A9'),
 (58720393L, u':1.151', '/com/canonical/menu/3800089'),
 (62916305L, u':1.159', '/com/canonical/menu/3C006D1'),
 (54526127L, u':1.129', '/com/canonical/menu/34000AF'),
 (58725701L, u':1.151', '/com/canonical/menu/3801545'),
 (25167093L, u':1.22', '/com/canonical/menu/18004F5'),
 (58726237L, u':1.151', '/com/canonical/menu/380175D'),
 (60825279L, u':1.155', '/com/canonical/menu/3A01EBF'),
 (58721371L, u':1.151', '/com/canonical/menu/380045B'),
 (25165828L, u':1.22', '/com/canonical/menu/1800004')]

This is the code I wrote in PyQt expecting something similar:

from PyQt4.QtGui import QApplication
from PyQt4.QtDBus import QDBus
from PyQt4.QtDBus import QDBusConnection
from PyQt4.QtDBus import QDBusInterface

desktop = QApplication([])
session_bus_connection = QDBusConnection.sessionBus()
service_name = 'com.canonical.AppMenu.Registrar'
service_path = 'com/canonical/AppMenu/Registrar'
interface = 'com.canonical.AppMenu.Registrar'
menu = QDBusInterface(service_name, service_path, interface, QDBusConnection.sessionBus())
reply = menu.call('GetMenus')
print reply.arguments()
desktop.exec_()

This is the output actually I get from the code above:

christopher@xx-pc:~/Documents/Code$ python desktop_dbus.py
process 2613: arguments to dbus_message_new_method_call() were incorrect, assertion "_dbus_check_is_valid_path (path)" failed in file ../../dbus/dbus-message.c line 1204.
This is normally a bug in some application using the D-Bus library.
process 2613: arguments to dbus_message_set_auto_start() were incorrect, assertion "message != NULL" failed in file ../../dbus/dbus-message.c line 2885.
This is normally a bug in some application using the D-Bus library.
process 2613: arguments to dbus_message_iter_init_append() were incorrect, assertion "message != NULL" failed in file ../../dbus/dbus-message.c line 2284.
This is normally a bug in some application using the D-Bus library.
QDBusConnection: error: could not send message to service "com.canonical.AppMenu.Registrar" path "com/canonical/AppMenu/Registrar" interface "org.freedesktop.DBus.Introspectable" member "Introspect": 
[]

Can anyone tell me why the message isn't being sent?

  • 2
    As the first error indicates, your service_path is wrong. All DBus paths start with a /. – Jjed Jun 9 '12 at 3:08
  • The question may be valuable as an example on how to get started with pyqt and dbus. Thanks. – John S Gruber Jun 9 '12 at 4:55
2

Answer based on this comment by Jjed:

process 2613: arguments to dbus_message_new_method_call() were incorrect
 assertion "_dbus_check_is_valid_path (path)" failed in file ../../dbus/dbus-message.c line 1204.
This is normally a bug in some application using the D-Bus library.

This indicates the problem, which is your service_path. All DBus paths start with /, so you should change

service_path = 'com/canonical/AppMenu/Registrar'

to

service_path = '/com/canonical/AppMenu/Registrar'

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