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# Copyright 2012 Canonical Ltd.
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# Zygmunt Krynicki <zygmunt.krynicki@canonical.com>
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License version 3,
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# as published by the Free Software Foundation.
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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Module for working with UDisks2 from python.
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There are two main classes that are interesting here.
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The first class is UDisksObserver, which is easy to setup and has pythonic API
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to all of the stuff that happens in UDisks2. It offers simple signal handlers
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for any changes that occur in UDisks2 that were advertised by DBus.
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The second class is UDisksModel, that builds on the observer class to offer
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persistent collection of objects managed by UDisks2.
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To work with this model you will likely want to look at:
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http://udisks.freedesktop.org/docs/latest/ref-dbus.html
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from dbus import Interface, PROPERTIES_IFACE
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from dbus.exceptions import DBusException
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from checkbox.dbus import drop_dbus_type
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__all__ = ['UDisks2Observer', 'UDisks2Model', 'Signal', 'is_udisks2_supported',
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def is_udisks2_supported(system_bus):
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Check if udisks2 is available on the system bus.
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Calling this _may_ trigger activation of the UDisks2 daemon but it
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should only happen on systems where it is already expected to run all
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observer = UDisks2Observer()
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logging.debug("Trying to connect to UDisks2...")
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observer.connect_to_bus(system_bus)
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except DBusException as exc:
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if exc.get_dbus_name() == "org.freedesktop.DBus.Error.ServiceUnknown":
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logging.debug("No UDisks2 on the system bus")
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logging.debug("Got UDisks2 connection")
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def map_udisks1_connection_bus(udisks1_connection_bus):
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Map the value of udisks1 ConnectionBus property to the corresponding values
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in udisks2. This a lossy function as some values are no longer supported.
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Incorrect values raise LookupError
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'ata_serial_esata': '', # gone from udisks2
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'firewire': 'ieee1394', # renamed
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'scsi': '', # gone from udisks2
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'sdio': 'sdio', # as-is
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}[udisks1_connection_bus]
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def lookup_udev_device(udisks2_object, udev_devices):
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Find the udev_device that corresponds to the udisks2 object
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Devices are matched by unix filesystem path of the special file (device).
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The udisks2_object must implement the block device interface (so that the
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block device path can be determined) or a ValueError is raised.
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The udisks2_object must be the dictionary that maps from interface names to
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dictionaries of properties. For compatible data see
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UDisks2Model.managed_objects The udev_devices must be a list of udev
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device, as returned from GUdev.
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If there is no match, LookupError is raised with the unix block device
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block_props = udisks2_object[UDISKS2_BLOCK_INTERFACE]
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raise ValueError("udisks2_object must be a block device")
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block_dev = block_props['Device']
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for udev_device in udev_devices:
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if udev_device.get_device_file() == block_dev:
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raise LookupError(block_dev)
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# The well-known name for the ObjectManager interface, sadly it is not a part
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# of the python binding along with the rest of well-known names.
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OBJECT_MANAGER_INTERFACE = "org.freedesktop.DBus.ObjectManager"
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# The well-known name of the filesystem interface implemented by certain
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# objects exposed by UDisks2
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UDISKS2_FILESYSTEM_INTERFACE = "org.freedesktop.UDisks2.Filesystem"
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# The well-known name of the block (device) interface implemented by certain
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# objects exposed by UDisks2
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UDISKS2_BLOCK_INTERFACE = "org.freedesktop.UDisks2.Block"
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# The well-known name of the drive interface implemented by certain objects
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UDISKS2_DRIVE_INTERFACE = "org.freedesktop.UDisks2.Drive"
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Basic signal that supports arbitrary listeners.
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While this class can be used directly it is best used with the helper
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decorator Signal.define on a member function. The function body is ignored,
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apart from the documentation.
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The function name then becomes a unique (per encapsulating class instance)
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object (an instance of this Signal class) that is created on demand.
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In practice you just have a documentation and use
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object.signal_name.connect() and object.signal_name(*args, **kwargs) to
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def __init__(self, signal_name):
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Construct a signal with the given name
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self._signal_name = signal_name
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def connect(self, listener):
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Connect a new listener to this signal
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That listener will be called whenever fire() is invoked on the signal
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self._listeners.append(listener)
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def disconnect(self, listener):
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Disconnect an existing listener from this signal
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self._listeners.remove(listener)
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def fire(self, args, kwargs):
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Fire this signal with the specified arguments and keyword arguments.
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Typically this is used by using __call__() on this object which is more
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natural as it does all the argument packing/unpacking transparently.
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for listener in self._listeners:
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listener(*args, **kwargs)
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def __call__(self, *args, **kwargs):
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Call fire() with all arguments forwarded transparently
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self.fire(args, kwargs)
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def define(cls, dummy_func):
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Helper decorator to define a signal descriptor in a class
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The decorated function is never called but is used to get
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return _SignalDescriptor(dummy_func)
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class _SignalDescriptor:
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Descriptor for convenient signal access.
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Typically this class is used indirectly, when accessed from Signal.define
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method decorator. It is used to do all the magic required when accessing
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signal name on a class or instance.
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def __init__(self, dummy_func):
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self.signal_name = dummy_func.__name__
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self.__doc__ = dummy_func.__doc__
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return "<SignalDecorator for signal: %r>" % self.signal_name
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def __get__(self, instance, owner):
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# Ensure that the instance has __signals__ property
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if not hasattr(instance, "__signals__"):
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instance.__signals__ = {}
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if self.signal_name not in instance.__signals__:
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instance.__signals__[self.signal_name] = Signal(self.signal_name)
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return instance.__signals__[self.signal_name]
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def __set__(self, instance, value):
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raise AttributeError("You cannot overwrite signals")
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def __delete__(self, instance):
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raise AttributeError("You cannot delete signals")
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class UDisks2Observer:
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Class for observing ongoing changes in UDisks2
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Create a UDisks2 model.
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The model must be connected to a bus before it is first used, see
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# Proxy to the UDisks2 object
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self._udisks2_obj = None
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# Proxy to the ObjectManager interface exposed by UDisks2 object
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self._udisks2_obj_manager = None
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def on_initial_objects(self, managed_objects):
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Signal fired when the initial list of objects becomes available
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def on_interfaces_added(self, object_path, interfaces_and_properties):
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Signal fired when one or more interfaces gets added to a specific
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def on_interfaces_removed(self, object_path, interfaces):
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Signal fired when one or more interface gets removed from a specific
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def on_properties_changed(self, interface_name, changed_properties,
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invalidated_properties, sender=None):
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Signal fired when one or more property changes value or becomes
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def connect_to_bus(self, bus):
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Establish initial connection to UDisks2 on the specified DBus bus.
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This will also load the initial set of objects from UDisks2 and thus
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fire the on_initial_objects() signal from the model. Please call this
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method only after connecting that signal if you want to observe that
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# Once everything is ready connect to udisks2
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self._connect_to_udisks2(bus)
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# And read all the initial objects and setup
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# change event handlers
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self._get_initial_objects()
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def _connect_to_udisks2(self, bus):
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Setup the initial connection to UDisks2
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This step can fail if UDisks2 is not available and cannot be
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# Access the /org/freedesktop/UDisks2 object sitting on the
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# org.freedesktop.UDisks2 bus name. This will trigger the necessary
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# activation if udisksd is not running for any reason
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logging.debug("Accessing main UDisks2 object")
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self._udisks2_obj = bus.get_object(
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"org.freedesktop.UDisks2", "/org/freedesktop/UDisks2")
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# Now extract the standard ObjectManager interface so that we can
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# observe and iterate the collection of objects that UDisks2 provides.
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logging.debug("Accessing ObjectManager interface on UDisks2 object")
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self._udisks2_obj_manager = Interface(
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self._udisks2_obj, OBJECT_MANAGER_INTERFACE)
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# Connect to the PropertiesChanged signal. Here unlike before we want
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# to listen to all signals, regardless of who was sending them in the
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logging.debug("Setting up DBus signal handler for PropertiesChanged")
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bus.add_signal_receiver(
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self._on_properties_changed,
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signal_name="PropertiesChanged",
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dbus_interface=PROPERTIES_IFACE,
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# Use the sender_keyword keyword argument to indicate that we wish
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# to know the sender of each signal. For consistency with other
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# signals we choose to use the 'object_path' keyword argument.
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sender_keyword='sender')
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def _get_initial_objects(self):
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Get the initial collection of objects.
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Needs to be called before the first signals from DBus are observed.
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Requires a working connection to UDisks2.
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# Having this interface we can now peek at the existing objects.
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# We can use the standard method GetManagedObjects() to do that
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logging.debug("Accessing GetManagedObjects() on UDisks2 object")
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managed_objects = self._udisks2_obj_manager.GetManagedObjects()
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managed_objects = drop_dbus_type(managed_objects)
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# Fire the public signal for getting initial objects
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self.on_initial_objects(managed_objects)
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# Connect our internal handles to the DBus signal handlers
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logging.debug("Setting up DBus signal handler for InterfacesAdded")
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self._udisks2_obj_manager.connect_to_signal(
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"InterfacesAdded", self._on_interfaces_added)
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logging.debug("Setting up DBus signal handler for InterfacesRemoved")
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self._udisks2_obj_manager.connect_to_signal(
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"InterfacesRemoved", self._on_interfaces_removed)
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def _on_interfaces_added(self, object_path, interfaces_and_properties):
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Internal callback that is called by DBus
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This function is responsible for firing the public signal
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# Convert from dbus types
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object_path = drop_dbus_type(object_path)
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interfaces_and_properties = drop_dbus_type(interfaces_and_properties)
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# Log what's going on
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logging.debug("The object %r has gained the following interfaces and "
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"properties: %r", object_path, interfaces_and_properties)
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# Call the signal handler
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self.on_interfaces_added(object_path, interfaces_and_properties)
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def _on_interfaces_removed(self, object_path, interfaces):
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Internal callback that is called by DBus
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This function is responsible for firing the public signal
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# Convert from dbus types
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object_path = drop_dbus_type(object_path)
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interfaces = drop_dbus_type(interfaces)
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# Log what's going on
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logging.debug("The object %r has lost the following interfaces: %r",
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object_path, interfaces)
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# Call the signal handler
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self.on_interfaces_removed(object_path, interfaces)
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def _on_properties_changed(self, interface_name, changed_properties,
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invalidated_properties, sender=None):
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Internal callback that is called by DBus
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This function is responsible for firing the public signal
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# Convert from dbus types
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interface_name = drop_dbus_type(interface_name)
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changed_properties = drop_dbus_type(changed_properties)
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invalidated_properties = drop_dbus_type(invalidated_properties)
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sender = drop_dbus_type(sender)
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# Log what's going on
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logging.debug("Some object with the interface %r has changed "
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"properties: %r and invalidated properties %r "
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interface_name, changed_properties,
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invalidated_properties, sender)
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# Call the signal handler
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self.on_properties_changed(interface_name, changed_properties,
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invalidated_properties, sender)
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Model for working with UDisks2
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This class maintains a persistent model of what UDisks2 knows about, based
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on the UDisks2Observer class and the signals it offers.
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def __init__(self, observer):
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Create a UDisks2 model.
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The model will track changes using the specified observer (which is
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expected to be a UDisks2Observer instance)
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You should only connect the observer to the bus after creating the
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model otherwise the initial objects will not be detected.
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# Local state, everything that UDisks2 tells us
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self._managed_objects = {}
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self._observer = observer
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# Connect all the signals to the observer
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self._observer.on_initial_objects.connect(self._on_initial_objects)
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self._observer.on_interfaces_added.connect(self._on_interfaces_added)
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self._observer.on_interfaces_removed.connect(
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self._on_interfaces_removed)
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self._observer.on_properties_changed.connect(
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self._on_properties_changed)
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Signal sent whenever the collection of managed object changes
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Note that this signal is fired _after_ the change has occurred
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def managed_objects(self):
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A collection of objects that is managed by this model. All changes as
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well as the initial state, are reflected here.
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return self._managed_objects
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def _on_initial_objects(self, managed_objects):
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Internal callback called when we get the initial collection of objects
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self._managed_objects = drop_dbus_type(managed_objects)
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def _on_interfaces_added(self, object_path, interfaces_and_properties):
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Internal callback called when an interface is added to certain object
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# Update internal state
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if object_path not in self._managed_objects:
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self._managed_objects[object_path] = {}
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obj = self._managed_objects[object_path]
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obj.update(interfaces_and_properties)
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# Fire the change signal
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def _on_interfaces_removed(self, object_path, interfaces):
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Internal callback called when an interface is removed from a certain
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# Update internal state
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if object_path in self._managed_objects:
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obj = self._managed_objects[object_path]
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for interface in interfaces:
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# Fire the change signal
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def _on_properties_changed(self, interface_name, changed_properties,
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invalidated_properties, sender=None):
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# XXX: This is a workaround the fact that we cannot
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# properly track changes to all properties :-(
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self._managed_objects = drop_dbus_type(
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self._observer._udisks2_obj_manager.GetManagedObjects())
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# Fire the change signal()
added
removed
checkbox-support/checkbox_support/dbus/udisks2.py
