200 lines
6.4 KiB
ReStructuredText
200 lines
6.4 KiB
ReStructuredText
Ecore DBus Mainloop integration
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===============================
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How to use the main loop
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-----------------------------
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Python-EFL provide the necessary main loop integration to let
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python-dbus use the Ecore main loop to perform async stuff. The only
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function you need to use from the efl is: DBusEcoreMainLoop()
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The function returns a NativeMainLoop to attach the Ecore main loop to D-Bus
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from within Python. In practice you just need to pass the NativeMainLoop
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as the 'mainloop' param when you connect to a bus.
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This is how you connect to a dbus bus:
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.. code-block:: python
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import dbus
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from efl import ecore
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from efl.dbus_mainloop import DBusEcoreMainLoop
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# connect to the session bus
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bus = dbus.SessionBus(mainloop=DBusEcoreMainLoop())
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# or to the system bus
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bus = dbus.SystemBus(mainloop=DBusEcoreMainLoop())
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Once you have your bus connected you can just normally use all the python-dbus
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functionality. This is the reason why you will not find any docs about dbus
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here (except for some basic examples).
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It's therefore highly suggested to read the official python-dbus tutorial and
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to use the python-dbus reference, you will find all the links in the bottom
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of the page.
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Proxy objects
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-------------
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In the dbus world to interact with an object you need to know:
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- the name of the service, ex: `org.enlightenment.FileManager`
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- the path to the object you are intrested, ex: `/org/enlightenment/FileManager`
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- the interface to interact with, ex: `org.enlightenment.FileManager`
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.. code-block:: python
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obj = bus.get_object(named_service, object_path)
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iface = dbus.Interface(obj, iface_name)
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then, on the iface object, you can call methods, connect to signals and access
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properties.
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Calling methods
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---------------
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There are at least two way to call methods on a remote object, the first
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example show how to do it the simple way, while the second show a much more
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complex but much powerfull async way. Note: using the sync way can make your
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app lag or halt forever if the remote keep too much time to respond.
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Both the examples use the ``OpenDirectory(s)`` method of the Enlightenment
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file manager to open a new window in the `/tmp` directory.
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.. code-block:: python
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# synchronous call
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obj = bus.get_object('org.enlightenment.FileManager',
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'/org/enlightenment/FileManager')
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iface = dbus.Interface(obj, 'org.enlightenment.FileManager')
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# directly
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iface.OpenDirectory('/tmp')
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# or using a method object
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meth = iface.get_dbus_method('OpenDirectory')
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meth('/tmp')
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.. code-block:: python
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# asynchronous call
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def reply_handler(*params):
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print("Method return: " + str(params))
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def error_handler(*params):
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print("Method error")
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obj = bus.get_object('org.enlightenment.FileManager',
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'/org/enlightenment/FileManager')
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iface = dbus.Interface(obj, 'org.enlightenment.FileManager')
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iface.OpenDirectory('/tmp',
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reply_handler=reply_handler,
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error_handler=error_handler)
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ecore.main_loop_begin()
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Accessing properties
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--------------------
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To access properties you need to use the standard **org.freedesktop.DBus.Properties**
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interface that all the objects provide. Methods on this iterface are:
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- Get(s interface, s propname) → (v value)
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- GetAll(s interface) → (a{sv} props)
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- Set(s interface, s propname, v value)
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The example show how to get the value of the `DaemonVersion` prop of `UDisks`
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.. code-block:: python
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bus = dbus.SystemBus(mainloop=DBusEcoreMainLoop())
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obj = bus.get_object('org.freedesktop.UDisks',
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'/org/freedesktop/UDisks')
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props_iface = dbus.Interface(obj, 'org.freedesktop.DBus.Properties')
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value = props_iface.Get('org.freedesktop.UDisks', 'DaemonVersion')
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Connecting signals
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------------------
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.. literalinclude:: ../../examples/dbus/test_signal_simple.py
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Introspection
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-------------
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To get information for a given proxy object you need to use the ``Introspect()``
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method on the **org.freedesktop.DBus.Introspectable** interface.
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The introspection will return an XML string that describe all the interfaces
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available on the object, with all the methods, properties and signals info.
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.. code-block:: python
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bus = dbus.SessionBus(mainloop=DBusEcoreMainLoop())
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obj = bus.get_object('org.enlightenment.FileManager',
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'/org/enlightenment/FileManager')
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iface = dbus.Interface(obj, 'org.freedesktop.DBus.Introspectable')
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xml_string = iface.Introspect()
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This other example show how to do recursive introspection on a given service,
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starting from the root object path ``/``
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.. code-block:: python
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import dbus
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import xml.etree.ElementTree as ElementTree
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from efl import ecore
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from efl.dbus_mainloop import DBusEcoreMainLoop
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def recursive_introspect(bus, named_service, object_path):
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print('Introspecting obj "%s" on service "%s"' % \
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(object_path, named_service))
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# introspect
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obj = bus.get_object(named_service, object_path)
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iface = dbus.Interface(obj, 'org.freedesktop.DBus.Introspectable')
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xml_string = iface.Introspect()
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# parse
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for xml_node in ElementTree.fromstring(xml_string):
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# found an interface
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if xml_node.tag == 'interface':
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print(' Found interface: ' + xml_node.attrib['name'])
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for child in xml_node:
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if child.tag == 'property':
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print(' Found property: ' + child.attrib['name'])
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if child.tag == 'method':
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print(' Found method: ' + child.attrib['name'])
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if child.tag == 'signal':
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print(' Found signal: ' + child.attrib['name'])
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# found another node, introspect it...
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if xml_node.tag == 'node':
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if object_path == '/':
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object_path = ''
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new_path = '/'.join((object_path, xml_node.attrib['name']))
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recursive_introspect(bus, named_service, new_path)
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bus = dbus.SystemBus(mainloop=DBusEcoreMainLoop())
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recursive_introspect(bus, 'org.freedesktop.UDisks', '/')
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References
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----------
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- `dbus tutorial <http://dbus.freedesktop.org/doc/dbus-tutorial.html>`_
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- `python-dbus tutorial <http://dbus.freedesktop.org/doc/dbus-python/doc/tutorial.html>`_
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- `python-dbus reference <http://dbus.freedesktop.org/doc/dbus-python/api/index.html>`_
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