glib/docs/reference/gio/gdbus-codegen.rst

.. _gdbus-codegen(1):
.. meta::
   :copyright: Copyright 2011, 2013, 2016 Red Hat, Inc.
   :copyright: Copyright 2013, 2022 Emmanuele Bassi
   :copyright: Copyright 2017 Patrick Griffis
   :copyright: Copyright 2018 Iñigo Martínez
   :copyright: Copyright 2018, 2019 Endless Mobile, Inc.
   :copyright: Copyright 2020 Endless OS Foundation, LLC
   :copyright: Copyright 2020 Chun-wei Fan
   :license: LGPL-2.1-or-later
..
   This has to be duplicated from above to make it machine-readable by `reuse`:
   SPDX-FileCopyrightText: 2011, 2013, 2016 Red Hat, Inc.
   SPDX-FileCopyrightText: 2013, 2022 Emmanuele Bassi
   SPDX-FileCopyrightText: 2017 Patrick Griffis
   SPDX-FileCopyrightText: 2018 Iñigo Martínez
   SPDX-FileCopyrightText: 2018, 2019 Endless Mobile, Inc.
   SPDX-FileCopyrightText: 2020 Endless OS Foundation, LLC
   SPDX-FileCopyrightText: 2020 Chun-wei Fan
   SPDX-License-Identifier: LGPL-2.1-or-later

=============
gdbus-codegen
=============

--------------------------------------
D-Bus code and documentation generator
--------------------------------------

SYNOPSIS
--------

|  **gdbus-codegen**
|    [--help]
|    [--interface-prefix *org.project.Prefix*]
|    [--header | --body | --interface-info-header | --interface-info-body | --generate-c-code *OUTFILES*]
|    [--c-namespace *YourProject*]
|    [--c-generate-object-manager]
|    [--c-generate-autocleanup none|objects|all]
|    [--output-directory *OUTDIR* | --output *OUTFILE*]
|    [--generate-docbook *OUTFILES*]
|    [--generate-rst *OUTFILES*]
|    [--pragma-once]
|    [--xml-files *FILE*]
|    [--symbol-decorator *DECORATOR* [--symbol-decorator-header *HEADER*] [--symbol-decorator-define *DEFINE*]]
|    [--annotate *ELEMENT* *KEY* *VALUE*]…
|    [--glib-min-required *VERSION*]
|    [--glib-max-allowed *VERSION*]
|    *FILE*…

DESCRIPTION
-----------

``gdbus-codegen`` is used to generate code and/or documentation for one or more
D-Bus interfaces.

``gdbus-codegen`` reads
`D-Bus Introspection XML <https://dbus.freedesktop.org/doc/dbus-specification.html#introspection-format>`_
from files passed as additional arguments on the command line and generates
output files. It currently supports generating C source code (via ``--body``) or
header (via ``--header``) and DocBook XML (via ``--generate-docbook``).
Alternatively, more restricted C source code and headers can be generated, which
just contain the interface information (as ``GDBusInterfaceInfo`` structures)
using ``--interface-info-body`` and ``--interface-info-header``.

GENERATING C CODE
-----------------

When generating C code, a ``GInterface`` derived type is generated for each
D-Bus interface. Additionally, for every generated type, ``FooBar``, two
concrete instantiatable types, ``FooBarProxy`` and ``FooBarSkeleton``,
implementing said interface are also generated. The former is derived from
``GDBusProxy`` and intended for use on the client side while the latter is
derived from the ``GDBusInterfaceSkeleton`` type making it easy to export on a
``GDBusConnection`` either directly or via a ``GDBusObjectManagerServer``
instance.

For C code generation either ``--body`` that generates source code, ``--header``
that generates headers, ``--interface-info-body`` that generates interface
information source code, or ``--interface-info-header`` that generates interface
information headers, can be used. These options must be used along with
``--output``, which is used to specify the file to output to.

Both files can be generated at the same time by using ``--generate-c-code``, but
this option is deprecated. In this case ``--output`` cannot be used due to the
generation of multiple files. Instead pass ``--output-directory`` to specify the
directory to put the output files in. By default the current directory will be
used.

The name of each generated C type is derived from the D-Bus interface name
stripped with the prefix given with ``--interface-prefix`` and with the dots
removed and initial characters capitalized. For example, for the D-Bus
interface ``com.acme.Coyote`` the name used is ``ComAcmeCoyote``. For the D-Bus
interface ``org.project.Bar.Frobnicator`` with ``--interface-prefix`` set to
``org.project.``, the name used is ``BarFrobnicator``.

For methods, signals and properties, if not specified, the name defaults to the
name of the method, signal or property.

Two forms of the name are used — the CamelCase form and the lower-case form. The
CamelCase form is used for the ``GType`` and struct name, while lower-case form
is used in function names. The lower-case form is calculated by converting from
CamelCase to lower-case and inserting underscores at word boundaries (using
certain heuristics).

If the value given by the ``org.gtk.GDBus.C.Name`` annotation or the
``--c-namespace`` option contains an underscore (sometimes called *Ugly_Case*),
then the camel-case name is derived by removing all underscores, and the
lower-case name is derived by lower-casing the string. This is useful in some
situations where abbreviations are used. For example, if the annotation is used
on the interface ``net.MyCorp.MyApp.iSCSITarget`` with the value
``iSCSI_Target`` the CamelCase form is ``iSCSITarget`` while the lower-case form
is ``iscsi_target``. If the annotation is used on the method ``EjectTheiPod``
with the value ``Eject_The_iPod``, the lower-case form is ``eject_the_ipod``.

GENERATING DOCBOOK DOCUMENTATION
--------------------------------

Each generated DocBook XML file (see the ``--generate-docbook`` option for
details) is a ``RefEntry`` article describing the D-Bus interface. (See the
`DocBook documentation <https://tdg.docbook.org/tdg/4.5/refentry.html>`_.)

GENERATING RESTRUCTUREDTEXT DOCUMENTATION
-----------------------------------------

Each generated reStructuredText file (see the ``--generate-rst`` option for
details) is a plain text
`reStructuredText <https://docutils.sourceforge.io/rst.html>`_ document
describing the D-Bus interface.

OPTIONS
-------

The following options are supported:

``-h``, ``--help``

  Show help and exit.

``--xml-files`` *FILE*

  This option is deprecated; use positional arguments instead.  The D-Bus
  introspection XML file.

``--interface-prefix`` *org.project.Prefix.*

  A prefix to strip from all D-Bus interface names when
  calculating the type name for the C binding and the DocBook ``sortas``
  `attribute <https://tdg.docbook.org/tdg/4.5/primary.html>`_.

``--generate-docbook`` *OUTFILES*

  Generate DocBook Documentation for each D-Bus interface and put it in
  ``OUTFILES-NAME.xml`` where ``NAME`` is a placeholder for the interface
  name, e.g. ``net.Corp.FooBar`` and so on.

  Pass ``--output-directory`` to specify the directory to put the output files
  in. By default the current directory will be used.

``--generate-rst`` *OUTFILES*

  Generate reStructuredText Documentation for each D-Bus interface and put it in
  ``OUTFILES-NAME.rst`` where ``NAME`` is a placeholder for the interface
  name, e.g. ``net.Corp.FooBar`` and so on.

  Pass ``--output-directory`` to specify the directory to put the output files
  in. By default the current directory will be used.

``--generate-c-code`` *OUTFILES*

  Generate C code for all D-Bus interfaces and put it in ``OUTFILES.c`` and
  ``OUTFILES.h`` including any sub-directories. If you want the files to be
  output in a different location use ``--output-directory`` as ``OUTFILES.h``
  including sub-directories will be referenced from ``OUTFILES.c``.

  The full paths would then be
  ``$(OUTDIR)/$(dirname $OUTFILES)/$(basename $OUTFILES).{c,h}``.

``--c-namespace`` *YourProject*

  The namespace to use for generated C code. This is expected to be in
  `CamelCase <https://en.wikipedia.org/wiki/Camel_case>`_ or *Ugly_Case* (see
  above).

``--pragma-once``

  If this option is passed, the
  `#pragma once <https://en.wikipedia.org/wiki/Pragma_once>`_ preprocessor
  directive is used instead of include guards.

``--c-generate-object-manager``

  If this option is passed, suitable ``GDBusObject``, ``GDBusObjectProxy``,
  ``GDBusObjectSkeleton`` and ``GDBusObjectManagerClient`` subclasses are
  generated.

``--c-generate-autocleanup`` none|objects|all

  This option influences what types autocleanup functions are
  generated for. ``none`` means to not generate any autocleanup functions.
  ``objects`` means to generate them for object types, and ``all`` means to
  generate them for object types and interfaces. The default is ``objects``
  due to a corner case in backwards compatibility with a few projects,
  but you should likely switch your project to use ``all``.
  This option was added in GLib 2.50.

``--output-directory`` *OUTDIR*

  Directory to output generated source to. Equivalent to changing directory
  before generation.

  This option cannot be used with ``--body``, ``--header``,
  ``--interface-info-body`` or ``--interface-info-header``; and ``--output``
  must be used.

``--header``

  If this option is passed, it will generate the header code and write it to the
  disk by using the path and file name provided by ``--output``.

  Using ``--generate-c-code``, ``--generate-docbook`` or ``--output-directory``
  are not allowed to be used along with ``--header`` and ``--body`` options,
  because these options are used to generate only one file.

``--body``

  If this option is passed, it will generate the source code and write it to the
  disk by using the path and file name provided by ``--output``.

  Using ``--generate-c-code``, ``--generate-docbook`` or ``--output-directory``
  are not allowed to be used along with ``--header`` and ``--body`` options,
  because these options are used to generate only one file.

``--interface-info-header``

  If this option is passed, it will generate the header code for the
  ``GDBusInterfaceInfo`` structures only and will write it to the disk by using
  the path and file name provided by ``--output``.

  Using ``--generate-c-code``, ``--generate-docbook`` or ``--output-directory``
  are not allowed to be used along with the ``--interface-info-header`` and
  ``--interface-info-body`` options, because these options are used to generate
  only one file.

``--interface-info-body``

  If this option is passed, it will generate the source code for the
  ``GDBusInterfaceInfo`` structures only and will write it to the disk by using
  the path and file name provided by ``--output``.

  Using ``--generate-c-code``, ``--generate-docbook`` or ``--output-directory``
  are not allowed to be used along with the ``--interface-info-header`` and
  ``--interface-info-body`` options, because these options are used to generate
  only one file.

``--symbol-decorator`` *DECORATOR*

  If a ``DECORATOR`` is passed in with this option, all the generated function
  prototypes in the generated header will be marked with ``DECORATOR``. This can
  be used, for instance, to export symbols from code generated with
  ``gdbus-codegen``.

  This option was added in GLib 2.66.

``--symbol-decorator-header`` *HEADER*

  If a ``HEADER`` is passed in with this option, the generated header will put a
  ``#include HEADER`` before the rest of the items, except for the inclusion
  guards or ``#pragma once`` (if ``--pragma-once`` is used).  This is used if
  using another header file is needed for the decorator passed in via
  ``--symbol-decorator`` to be defined.

  This option was added in GLib 2.66.

  This option can only be used if ``--symbol-decorator`` is used.

``--symbol-decorator-define`` *DEFINE*

  If a ``DEFINE`` is passed in with this option, the generated source will add a
  ``#define DEFINE`` before the rest of the items.  This is used if a particular
  macro is needed to ensure the decorator passed in via ``--symbol-decorator``
  uses the correct definition when the generated source is being compiled.

  This option was added in GLib 2.66.

  This option can only be used if ``--symbol-decorator`` is used.

``--output`` *OUTFILE*

  The full path where the header (``--header``, ``--interface-info-header``) or
  the source code (``--body``, ``--interface-info-body``) will be written, using
  the path and filename provided by ``--output``. The full path could be
  something like ``$($OUTFILE).{c,h}``.

  Using ``--generate-c-code``, ``--generate-docbook`` or ``--output-directory``
  is not allowed along with ``--output``, because the latter is used to generate
  only one file.

``--annotate`` *ELEMENT* *KEY* *VALUE*

  Used to inject D-Bus annotations into the given XML files. It can be used with
  interfaces, methods, signals, properties and arguments in the following way::

     gdbus-codegen --c-namespace MyApp                           \
       --generate-c-code myapp-generated                         \
       --annotate "org.project.InterfaceName"                    \
         org.gtk.GDBus.C.Name MyFrobnicator                      \
       --annotate "org.project.InterfaceName:Property"           \
         bar bat                                                 \
       --annotate "org.project.InterfaceName.Method()"           \
         org.freedesktop.DBus.Deprecated true                    \
       --annotate "org.project.InterfaceName.Method()[arg_name]" \
         snake hiss                                              \
       --annotate "org.project.InterfaceName::Signal"            \
         cat meow                                                \
       --annotate "org.project.InterfaceName::Signal[arg_name]"  \
         dog wuff                                                \
       myapp-dbus-interfaces.xml

  Any UTF-8 string can be used for *KEY* and *VALUE*.

``--glib-min-required`` *VERSION*

  Specifies the minimum version of GLib which the code generated by
  ``gdbus-codegen`` can depend on. This may be used to make
  backwards-incompatible changes in the output or behaviour of ``gdbus-codegen``
  in future, which users may opt in to by increasing the value they pass for
  ``--glib-min-required``. If this option is not passed, the output from
  ``gdbus-codegen`` is guaranteed to be compatible with all versions of GLib
  from 2.30 upwards, as that is when ``gdbus-codegen`` was first released.

  Note that some version parameters introduce incompatible changes: all callers
  of the generated code might need to be updated, and if the generated code is
  part of a library’s API or ABI, then increasing the version parameter can
  result in an API or ABI break.

  The version number must be of the form ``MAJOR.MINOR.MICRO``, where all parts
  are integers. ``MINOR`` and ``MICRO`` are optional. The version number may not
  be smaller than ``2.30``.

  If the version number is ``2.64`` or greater, the generated code will
  have the following features:

  1. If a method has ``h`` (file descriptor) parameter(s), a ``GUnixFDList``
     parameter will exist in the generated code for it (whereas previously the
     annotation ``org.gtk.GDBus.C.UnixFD`` was required), and
  2. Method call functions will have two additional arguments to allow the user
     to specify ``GDBusCallFlags`` and a timeout value, as is possible when
     using ``g_dbus_proxy_call()``.

``--glib-max-allowed`` *VERSION*

  Specifies the maximum version of GLib which the code generated by
  ``gdbus-codegen`` can depend on. This may be used to ensure that code
  generated by ``gdbus-codegen`` is compilable with specific older versions of
  GLib that your software has to support.

  The version number must be of the form ``MAJOR.MINOR.MICRO``, where all parts
  are integers. ``MINOR`` and ``MICRO`` are optional. The version number must be
  greater than or equal to that passed to ``--glib-min-required``.
  It defaults to the version of GLib which provides this ``gdbus-codegen``.

SUPPORTED D-BUS ANNOTATIONS
---------------------------

The following D-Bus annotations are supported by ``gdbus-codegen``:

``org.freedesktop.DBus.Deprecated``

  Can be used on any ``<interface>``, ``<method>``, ``<signal>`` and
  ``<property>`` element to specify that the element is deprecated if its value
  is ``true``. Note that this annotation is defined in the
  `D-Bus specification <https://dbus.freedesktop.org/doc/dbus-specification.html#introspection-format>`_
  and can only assume the values ``true`` and ``false``. In particular, you
  cannot specify the version that the element was deprecated in nor any helpful
  deprecation message. Such information should be added to the element
  documentation instead.

  When generating C code, this annotation is used to add ``G_GNUC_DEPRECATED``
  to generated functions for the element.

  When generating DocBook XML, a deprecation warning will appear along the
  documentation for the element.

``org.gtk.GDBus.Since``

  Can be used on any ``<interface>``, ``<method>``, ``<signal>`` and
  ``<property>`` element to specify the version (any free-form string but
  compared using a version-aware sort function) the element appeared in.

  When generating C code, this field is used to ensure
  function pointer order for preserving ABI/API, see ‘STABILITY GUARANTEES’.

  When generating DocBook XML, the value of this tag appears in the
  documentation.

``org.gtk.GDBus.DocString``

  A string with DocBook content for documentation. This annotation can
  be used on ``<interface>``, ``<method>``, ``<signal>``, ``<property>`` and
  ``<arg>`` elements.

``org.gtk.GDBus.DocString.Short``

  A string with DocBook content for short/brief documentation. This annotation
  can only be used on ``<interface>`` elements.

``org.gtk.GDBus.C.Name``

  Can be used on any ``<interface>``, ``<method>``, ``<signal>`` and
  ``<property>`` element to specify the name to use when generating C code. The
  value is expected to be in
  `CamelCase <https://en.wikipedia.org/wiki/Camel_case>`_ or *Ugly_Case* (see
  above).

``org.gtk.GDBus.C.ForceGVariant``

  If set to a non-empty string, a ``GVariant`` instance will be used instead of
  the natural C type. This annotation can be used on any ``<arg>`` and
  ``<property>`` element.

``org.gtk.GDBus.C.UnixFD``

  If set to a non-empty string, the generated code will include parameters to
  exchange file descriptors using the ``GUnixFDList`` type. This annotation can
  be used on ``<method>`` elements.

As an easier alternative to using the ``org.gtk.GDBus.DocString`` annotation,
note that parser used by ``gdbus-codegen`` parses XML comments in a way similar
to `gtk-doc <https://developer-old.gnome.org/gtk-doc-manual/stable/>`_::

   <!--
     net.Corp.Bar:
     @short_description: A short description

     A <emphasis>longer</emphasis> description.

     This is a new paragraph.
   -->
   <interface name="net.corp.Bar">
     <!--
       FooMethod:
       @greeting: The docs for greeting parameter.
       @response: The docs for response parameter.

       The docs for the actual method.
     -->
     <method name="FooMethod">
       <arg name="greeting" direction="in" type="s"/>
       <arg name="response" direction="out" type="s"/>
     </method>

     <!--
       BarSignal:
       @blah: The docs for blah parameter.
       @boo: The docs for boo parameter.
       @since: 2.30

       The docs for the actual signal.
     -->
     <signal name="BarSignal">
       <arg name="blah" type="s"/>
       <arg name="boo" type="s"/>
     </signal>

     <!-- BazProperty: The docs for the property. -->
     <property name="BazProperty" type="s" access="read"/>
   </interface>

Note that ``@since`` can be used in any inline documentation bit (e.g. for
interfaces, methods, signals and properties) to set the ``org.gtk.GDBus.Since``
annotation. For the ``org.gtk.GDBus.DocString`` annotation (and inline
comments), note that substrings of the form ``#net.Corp.Bar``,
``net.Corp.Bar.FooMethod()``, ``#net.Corp.Bar::BarSignal`` and
``#net.Corp.InlineDocs:BazProperty`` are all expanded to links to the respective
interface, method, signal and property. Additionally, substrings starting with
``@`` and ``%`` characters are rendered as
`parameter <https://tdg.docbook.org/tdg/4.5/parameter.html>`_ and
`constant <https://tdg.docbook.org/tdg/4.5/constant.html>`_ respectively.

If both XML comments and ``org.gtk.GDBus.DocString`` or
``org.gtk.GDBus.DocString.Short`` annotations are present, the latter wins.

EXAMPLE
-------

Consider the following D-Bus Introspection XML::

   <node>
     <interface name="net.Corp.MyApp.Frobber">
       <method name="HelloWorld">
         <arg name="greeting" direction="in" type="s"/>
         <arg name="response" direction="out" type="s"/>
       </method>

       <signal name="Notification">
         <arg name="icon_blob" type="ay"/>
         <arg name="height" type="i"/>
         <arg name="messages" type="as"/>
       </signal>

       <property name="Verbose" type="b" access="readwrite"/>
     </interface>
   </node>

If ``gdbus-codegen`` is used on this file like this::

   gdbus-codegen --generate-c-code myapp-generated       \
                 --c-namespace MyApp                     \
                 --interface-prefix net.corp.MyApp.      \
                 net.Corp.MyApp.Frobber.xml

two files called ``myapp-generated.[ch]`` are generated. The files provide an
abstract ``GTypeInterface`` derived type called ``MyAppFrobber`` as well as two
instantiatable types with the same name but suffixed with ``Proxy`` and
``Skeleton``. The generated file, roughly, contains the following facilities::

   /* GType macros for the three generated types */
   #define MY_APP_TYPE_FROBBER (my_app_frobber_get_type ())
   #define MY_APP_TYPE_FROBBER_SKELETON (my_app_frobber_skeleton_get_type ())
   #define MY_APP_TYPE_FROBBER_PROXY (my_app_frobber_proxy_get_type ())

   typedef struct _MyAppFrobber MyAppFrobber; /* Dummy typedef */

   typedef struct
   {
     GTypeInterface parent_iface;

     /* Signal handler for the ::notification signal */
     void (*notification) (MyAppFrobber *proxy,
                           GVariant *icon_blob,
                           gint height,
                           const gchar* const *messages);

     /* Signal handler for the ::handle-hello-world signal */
     gboolean (*handle_hello_world) (MyAppFrobber *proxy,
                                     GDBusMethodInvocation *invocation,
                                     const gchar *greeting);
   } MyAppFrobberIface;

   /* Asynchronously calls HelloWorld() */
   void
   my_app_frobber_call_hello_world (MyAppFrobber *proxy,
                                    const gchar *greeting,
                                    GCancellable *cancellable,
                                    GAsyncReadyCallback callback,
                                    gp ointer user_data);
   gboolean
   my_app_frobber_call_hello_world_finish (MyAppFrobber *proxy,
                                           gchar **out_response,
                                           GAsyncResult *res,
                                           GError **error);

   /* Synchronously calls HelloWorld(). Blocks calling thread. */
   gboolean
   my_app_frobber_call_hello_world_sync (MyAppFrobber *proxy,
                                         const gchar *greeting,
                                         gchar **out_response,
                                         GCancellable *cancellable,
                                         GError **error);

   /* Completes handling the HelloWorld() method call */
   void
   my_app_frobber_complete_hello_world (MyAppFrobber *object,
                                        GDBusMethodInvocation *invocation,
                                        const gchar *response);

   /* Emits the ::notification signal / Notification() D-Bus signal */
   void
   my_app_frobber_emit_notification (MyAppFrobber *object,
                                     GVariant *icon_blob,
                                     gint height,
                                     const gchar* const *messages);

   /* Gets the :verbose GObject property / Verbose D-Bus property.
    * Does no blocking I/O.
    */
   gboolean my_app_frobber_get_verbose (MyAppFrobber *object);

   /* Sets the :verbose GObject property / Verbose D-Bus property.
    * Does no blocking I/O.
    */
   void my_app_frobber_set_verbose (MyAppFrobber *object,
                                    gboolean      value);

   /* Gets the interface info */
   GDBusInterfaceInfo *my_app_frobber_interface_info (void);

   /* Creates a new skeleton object, ready to be exported */
   MyAppFrobber *my_app_frobber_skeleton_new (void);

   /* Client-side proxy constructors.
    *
    * Additionally, _new_for_bus(), _new_for_bus_finish() and
    * _new_for_bus_sync() proxy constructors are also generated.
    */
   void
   my_app_frobber_proxy_new        (GDBusConnection     *connection,
                                    GDBusProxyFlags      flags,
                                    const gchar         *name,
                                    const gchar         *object_path,
                                    GCancellable        *cancellable,
                                    GAsyncReadyCallback  callback,
                                    gpointer             user_data);
   MyAppFrobber *
   my_app_frobber_proxy_new_finish (GAsyncResult        *res,
                                    GError             **error);
   MyAppFrobber *
   my_app_frobber_proxy_new_sync   (GDBusConnection     *connection,
                                    GDBusProxyFlags      flags,
                                    const gchar         *name,
                                    const gchar         *object_path,
                                    GCancellable        *cancellable,
                                    GError             **error);

Thus, for every D-Bus method, there will be three C functions for calling the
method, one ``GObject`` signal for handling an incoming call and one C function
for completing an incoming call. For every D-Bus signal, there’s one ``GObject``
signal and one C function for emitting it. For every D-Bus property, two C
functions are generated (one setter, one getter) and one ``GObject`` property.
The following table summarizes the generated facilities and where they are
applicable:

.. table::
   :widths: auto

   ====================  =========================================================  =================================================================================================================
   Symbol type           Client                                                     Server
   ====================  =========================================================  =================================================================================================================
   Types                 Use ``MyAppFrobberProxy``.                                 Any type implementing the ``MyAppFrobber`` interface.
   Methods               Use ``m_a_f_hello_world()`` to call.                       Receive via the ``handle_hello_world()`` signal handler. Complete the call with ``m_a_f_complete_hello_world()``.
   Signals               Connect to the ``::notification`` signal.                  Use ``m_a_f_emit_notification()`` to emit signal.
   Properties (Reading)  Use ``m_a_f_get_verbose()`` or the ``:verbose`` property.  Implement the ``get_property()`` vfunc of ``GObject``.
   Properties (writing)  Use ``m_a_f_set_verbose()`` or the ``:verbose`` property.  Implement the ``set_property()`` vfunc of ``GObject``.
   ====================  =========================================================  =================================================================================================================

Client-side usage
^^^^^^^^^^^^^^^^^

You can use the generated proxy type with the generated constructors::

   MyAppFrobber *proxy;
   GError *error;

   error = NULL;
   proxy = my_app_frobber_proxy_new_for_bus_sync (
               G_BUS_TYPE_SESSION,
               G_DBUS_PROXY_FLAGS_NONE,
               "net.Corp.MyApp",              /* bus name */
               "/net/Corp/MyApp/SomeFrobber", /* object */
               NULL,                          /* GCancellable* */
               &error);
   /* do stuff with proxy */
   g_object_unref (proxy);

Instead of using the generic ``GDBusProxy`` facilities, one can use the
generated methods such as ``my_app_frobber_call_hello_world()`` to invoke
the ``net.Corp.MyApp.Frobber.HelloWorld()`` D-Bus method, connect to the
``::notification`` ``GObject`` signal to receive the
``net.Corp.MyApp.Frobber::Notification`` D-Bus signal and get/set the
``net.Corp.MyApp.Frobber:Verbose`` D-Bus Property using either the ``GObject``
property ``:verbose`` or the ``my_app_get_verbose()`` and
``my_app_set_verbose()`` methods. Use the standard ``GObject::notify`` signal to
listen to property changes.

Note that all property access is via the ``GDBusProxy`` property cache so no I/O
is ever done when reading properties. Also note that setting a property will
cause the ``org.freedesktop.DBus.Properties.Set`` method
(`documentation <https://dbus.freedesktop.org/doc/dbus-specification.html#standard-interfaces-properties>`_)
to be called on the remote object. This call, however, is asynchronous so
setting a property won’t block. Further, the change is delayed and no error
checking is possible.

Server-side usage
^^^^^^^^^^^^^^^^^

The generated ``MyAppFrobber`` interface is designed so it is easy to implement
it in a ``GObject`` subclass. For example, to handle ``HelloWorld()`` method
invocations, set the vfunc for ``handle_hello_hello_world()`` in the
``MyAppFrobberIface`` structure. Similarly, to handle the
``net.Corp.MyApp.Frobber:Verbose`` property override the ``:verbose``
``GObject`` property from the subclass. To emit a signal, use e.g.
``my_app_emit_signal()`` or ``g_signal_emit_by_name()``.

Instead of subclassing, it is often easier to use the generated
``MyAppFrobberSkeleton`` subclass. To handle incoming method calls, use
``g_signal_connect()`` with the ``::handle-*`` signals and instead of
overriding the ``get_property()`` and ``set_property()`` vfuncs from
``GObject``, use ``g_object_get()`` and ``g_object_set()`` or the generated
property getters and setters (the generated class has an internal property bag
implementation).

For example::

   static gboolean
   on_handle_hello_world (MyAppFrobber           *interface,
                          GDBusMethodInvocation  *invocation,
                          const gchar            *greeting,
                          gpointer                user_data)
   {
     if (g_strcmp0 (greeting, "Boo") != 0)
       {
         gchar *response;
         response = g_strdup_printf ("Word! You said ‘%s’.", greeting);
         my_app_complete_hello_world (interface, invocation, response);
         g_free (response);
       }
     else
       {
         g_dbus_method_invocation_return_error (invocation,
                    MY_APP_ERROR,
                    MY_APP_ERROR_NO_WHINING,
                    "Hey, %s, there will be no whining!",
                    g_dbus_method_invocation_get_sender (invocation));
       }
     return TRUE;
   }

     […]

     interface = my_app_frobber_skeleton_new ();
     my_app_frobber_set_verbose (interface, TRUE);

     g_signal_connect (interface,
                       "handle-hello-world",
                       G_CALLBACK (on_handle_hello_world),
                       some_user_data);

     […]

     error = NULL;
     if (!g_dbus_interface_skeleton_export (G_DBUS_INTERFACE_SKELETON (interface),
                                            connection,
                                            "/path/of/dbus_object",
                                            &error))
       {
         /* handle error */
       }

To facilitate atomic changesets (multiple properties changing at the same time),
``GObject::notify`` signals are queued up when received. The queue is drained in
an idle handler (which is called from the thread-default main loop of the thread
where the skeleton object was constructed) and will cause emissions of the
``org.freedesktop.DBus.Properties::PropertiesChanged``
(`documentation <https://dbus.freedesktop.org/doc/dbus-specification.html#standard-interfaces-properties>`_)
signal with all the properties that have changed. Use
``g_dbus_interface_skeleton_flush()`` or ``g_dbus_object_skeleton_flush()`` to
empty the queue immediately. Use ``g_object_freeze_notify()`` and
``g_object_thaw_notify()`` for atomic changesets if on a different thread.

C TYPE MAPPING
--------------

Scalar types (type strings ``b``, ``y``, ``n``, ``q``, ``i``, ``u``, ``x``,
``t`` and ``d``), strings (type strings ``s``, ``ay``, ``o`` and ``g``) and
arrays of strings (type strings ``as``, ``ao`` and ``aay``) are mapped to the
natural types, e.g. ``gboolean``, ``gdouble``, ``gint``, ``gchar*``, ``gchar**``
and so on. Everything else is mapped to the ``GVariant`` type.

This automatic mapping can be turned off by using the annotation
``org.gtk.GDBus.C.ForceGVariant`` — if used then a ``GVariant`` is always
exchanged instead of the corresponding native C type. This annotation may be
convenient to use when using bytestrings (type string ``ay``) for data that
could have embedded nul bytes.

STABILITY GUARANTEES
--------------------

The generated C functions are guaranteed to not change their ABI. That is, if a
method, signal or property does not change its signature in the introspection
XML, the generated C functions will not change their C ABI either. The ABI of
the generated instance and class structures will be preserved as well.

The ABI of the generated ``GType`` instances will be preserved only if the
``org.gtk.GDBus.Since`` annotation is used judiciously — this is because the
VTable for the ``GInterface`` relies on function pointers for signal handlers.
Specifically, if a D-Bus method, property or signal or is added to a D-Bus
interface, then ABI of the generated ``GInterface`` type is preserved if, and
only if, each added method, property signal is annotated with the
``org.gtk.GDBus.Since`` annotation using a greater version number than previous
versions.

The generated C code currently happens to be annotated with
`gtk-doc <https://developer-old.gnome.org/gtk-doc-manual/stable/>`_ and
`GObject Introspection <https://gi.readthedocs.io/en/latest/>`_ comments and
annotations. The layout and contents might change in the future so no guarantees
about e.g. ``SECTION`` usage etc. are given.

While the generated DocBook for D-Bus interfaces isn’t expected to change, no
guarantees are given at this point.

It is important to note that the generated code should not be checked into
version control systems, nor it should be included in distributed source
archives.

BUGS
----

Please send bug reports to either the distribution bug tracker or the
`upstream bug tracker <https://gitlab.gnome.org/GNOME/glib/issues/new>`_.

SEE ALSO
--------

`gdbus(1) <man:gdbus(1)>`_