===============================
API changes in dbus-python 0.80
===============================

:Author: Simon McVittie
:Contact: simon.mcvittie@collabora.co.uk
:Organization: `Collabora Ltd`_
:Date: 2006-11-23

.. _Collabora Ltd: http://www.collabora.co.uk/

Type changes
============

* The Byte constructor accepts either single-byte strings, or integers in
  the range 0 to 255.

* There is no Variant type any more. Instead, the ``variant_level``
  attribute on D-Bus types gives the number of variant wrappers in
  which it is contained; this is to remove ambiguity. For instance, calling
  this method::

    @dbus.service.method('com.example', in_signature='v', out_signature='') 
    def Print(self, variant):
        print repr(variant)

  yields the following results::

    # on the wire: Variant containing Int32
    Int32(0, variant_level=1)
    # on the wire: Variant containing Variant containing Int32
    Int32(0, variant_level=2)

  Once an object of a D-Bus type has been constructed, its
  ``variant_level`` cannot be altered.

* The D-Bus integer types (dbus.Int32, etc.) are properly range-checked.

* The Array constructor takes arguments (iterable[, signature])
  rather than (iterable[, type][, signature]); ditto for Dict.

Calling conventions
===================

* In method parameters, method returns from proxy methods, etc.,
  integers arrive as instances of dbus.Int32 etc., bytes arrive as
  Byte, and so on, rather than everything being converted to an
  appropriate built-in Python type. This means you can tell exactly
  what arguments went over the bus, and their types.

* Proxy methods with multiple return values return a tuple rather than
  a list.

* Calling a proxy method with reply ignored, or with async
  handlers, returns None

``dbus_bindings``
=================

* ConnectionError no longer exists (it was never raised)

* ``dbus_bindings`` is now called ``_dbus_bindings``, and is considerably
  different internally:

  * connections are private at the libdbus level: shared connections
    are only shared among Python code

  * The MessageIter stuff is now done in C: there's a much simpler
    Python API, ``Message.append(...)`` where positional arguments are
    the things to be appended, and the keyword argument ``signature``
    controls how objects are interpreted

  * The signature-guessing algorithm used if there is no proper
    signature is exposed as a static method,
    ``Message.guess_signature(*args)``

  * Bus is a subclass of Connection rather than being a wrapper object
    which has-a Connection

  * The timeouts in _send_with_reply and in _send_with_reply_and_block
    are in (possibly fractional) seconds, as is conventional in Python

  * The specialized Message subclasses have names ending with Message

* There is a small amount of compatibility glue in a new
  ``dbus_bindings`` module (also ``dbus.dbus_bindings``)
  which should enable most current code to work - this is deprecated,
  and will disappear in a future version of dbus-python

Main loops
==========

Main loop handling is different - instead of the
``use_default_mainloop`` keyword argument to Bus and subclasses, there's now
``mainloop`` which takes an instance of dbus.mainloop.NativeMainLoop.

Alternatively, you can set a default main loop by calling
``dbus.set_default_main_loop()`` and passing it a NativeMainLoop, or
by passing ``set_as_default=True`` to the factory function
from which you obtained the native main loop.

The plan is that in a future version of dbus-python there will be an
abstract base class dbus.mainloop.MainLoop (or something); when it's added,
instances of its subclasses will be accepted wherever a NativeMainLoop
instance is now. This will let you wrap main loops using a Python API.
This will be used to implement SimpleMainLoop (a pure-Python main loop
which can only do D-Bus) and a Twisted main-loop wrapper.

The only working mainloop implementation is (still) GLib; you can get
a NativeMainLoop instance by::

  from dbus.mainloop.glib import DBusGMainLoop
  my_native_main_loop = DBusGMainLoop(set_as_default=True)

The above is how the highly magical ``dbus.glib`` module is now implemented.
At some point ``dbus.glib`` will be deprecated, since it's non-obvious,
and pychecker will usually complain if you use it correctly!

At the moment the GLib main loop always uses the default main context;
python-gobject will probably need to add some extra API before we can
allow other main-contexts to be used.

..
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