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

<refentry id="gdbus-codegen" lang="en">

<refentryinfo>
  <title>gdbus</title>
  <productname>GIO</productname>
  <authorgroup>
    <author>
      <contrib>Developer</contrib>
      <firstname>David</firstname>
      <surname>Zeuthen</surname>
      <email>zeuthen@gmail.com</email>
    </author>
  </authorgroup>
</refentryinfo>

<refmeta>
  <refentrytitle>gdbus-codegen</refentrytitle>
  <manvolnum>1</manvolnum>
  <refmiscinfo class="manual">User Commands</refmiscinfo>
</refmeta>

<refnamediv>
  <refname>gdbus-codegen</refname>
  <refpurpose>D-Bus code and documentation generator</refpurpose>
</refnamediv>

<refsynopsisdiv>
  <cmdsynopsis>
    <command>gdbus-codegen</command>
    <arg><option>-h</option>, <option>--help</option></arg>
    <arg><option>--interface-prefix</option> <replaceable>org.project.Prefix</replaceable></arg>
    <arg><option>--generate-c-code</option> <replaceable>OUTFILES</replaceable></arg>
    <arg><option>--c-namespace</option> <replaceable>YourProject</replaceable></arg>
    <arg><option>--c-generate-object-manager</option></arg>
    <arg><option>--c-generate-autocleanup</option> none|objects|all</arg>
    <arg><option>--output-directory</option> <replaceable>OUTDIR</replaceable></arg>
    <arg><option>--generate-docbook</option> <replaceable>OUTFILES</replaceable></arg>
    <arg><option>--pragma-once</option></arg>
    <arg><option>--xml-files</option> <replaceable>FILE</replaceable></arg>
    <arg><option>--header</option></arg>
    <arg><option>--body</option></arg>
    <arg><option>--interface-info-header</option></arg>
    <arg><option>--interface-info-body</option></arg>
    <arg><option>--output</option> <replaceable>OUTFILE</replaceable></arg>
    <group choice="plain" rep="repeat">
      <arg>
        <option>--annotate</option>
        <replaceable>ELEMENT</replaceable>
        <replaceable>KEY</replaceable>
        <replaceable>VALUE</replaceable>
      </arg>
    </group>
    <arg><option>--glib-min-required</option> <replaceable>VERSION</replaceable></arg>
    <arg><option>--glib-max-allowed</option> <replaceable>VERSION</replaceable></arg>
    <arg choice="plain">FILE</arg>
    <arg>
      <arg choice="plain" rep="repeat">FILE</arg>
    </arg>
  </cmdsynopsis>
</refsynopsisdiv>

<refsect1>
  <title>Description</title>
  <para>
    <command>gdbus-codegen</command> is used to generate code and/or
    documentation for one or more D-Bus interfaces.
  </para>
  <para>
    <command>gdbus-codegen</command> reads
    <ulink
    url="http://dbus.freedesktop.org/doc/dbus-specification.html#introspection-format">D-Bus
    Introspection XML</ulink> from files passed as additional
    arguments on the command line and generates output files.
    It currently supports generating C source code (via
    <option>--body</option>) or header (via <option>--header</option>)
    and Docbook XML (via <option>--generate-docbook</option>). Alternatively,
    more restricted C source code and headers can be generated, which just
    contain the interface information (as <type>GDBusInterfaceInfo</type>
    structures) using <option>--interface-info-body</option> and
    <option>--interface-info-header</option>.
  </para>
</refsect1>

<refsect1>
  <title>Generating C code</title>
  <para>
    When generating C code, a
    #GInterface<!-- -->-derived type is generated for each D-Bus
    interface. Additionally, for every generated type,
    <type>FooBar</type>, two concrete instantiable types,
    <type>FooBarProxy</type> and <type>FooBarSkeleton</type>, 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.
  </para>
  <para>
    For C code generation either <option>--body</option> that
    generates source code, <option>--header</option> that
    generates headers, <option>--interface-info-body</option> that generates
    interface information source code, or
    <option>--interface-info-header</option> that generates interface information
    headers, can be used. These options must be used along with
    <option>--output</option>, which is used to specify the file to output to.
  </para>
  <para>
    Both files can be generated at the same time by using
    <option>--generate-c-code</option>, but this option is deprecated.
    In this case <option>--output</option> cannot be used due to the
    generation of multiple files. Instead pass
    <option>--output-directory</option> to specify the directory to put
    the output files in. By default the current directory will be used.
  </para>
  <para>
    The name of each generated C type is derived from the D-Bus
    interface name stripped with the prefix given with
    <option>--interface-prefix</option> and with the dots removed and
    initial characters capitalized. For example, for the D-Bus
    interface <literal>com.acme.Coyote</literal> the name used is
    <literal>ComAcmeCoyote</literal>. For the D-Bus interface
    <literal>org.project.Bar.Frobnicator</literal> with
    <option>--interface-prefix</option>
    <literal>org.project.</literal>, the name used is
    <literal>BarFrobnicator</literal>.
  </para>
  <para>
    For methods, signals and properties, if not specified, the name
    defaults to the name of the method, signal or property.
  </para>
  <para>
    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).
  </para>
  <para>
    If the value given by the <literal>org.gtk.GDBus.C.Name</literal>
    annotation or the <option>--c-namespace</option> option contains
    an underscore (sometimes called <emphasis>Ugly_Case</emphasis>),
    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
    <literal>net.MyCorp.MyApp.iSCSITarget</literal> with the value
    <literal>iSCSI_Target</literal> the CamelCase form is
    <literal>iSCSITarget</literal> while the lower-case form is
    <literal>iscsi_target</literal>. If the annotation is used on the
    method <literal>EjectTheiPod</literal> with the value
    <literal>Eject_The_iPod</literal>, the lower-case form is
    <literal>eject_the_ipod</literal>.
  </para>
</refsect1>

<refsect1>
  <title>Generating Docbook documentation</title>
  <para>
    Each generated Docbook XML file (see the
    <option>--generate-docbook</option> option for details) is a <ulink
    url="http://www.docbook.org/tdg/en/html/refentry.html"><literal>RefEntry</literal></ulink>
    article describing the D-Bus interface.
  </para>
</refsect1>

<refsect1>
  <title>Options</title>
  <para>
    The following options are supported:
  </para>
  <variablelist>

    <varlistentry>
      <term><option>-h</option>, <option>--help</option></term>
      <listitem>
        <para>
          Show help and exit.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>--xml-files</option> <replaceable>FILE</replaceable></term>
      <listitem>
        <para>
          This option is deprecated; use positional arguments instead.
          The D-Bus introspection XML file.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>--interface-prefix</option> <replaceable>org.project.Prefix.</replaceable></term>
      <listitem>
        <para>
          A prefix to strip from all D-Bus interface names when
          calculating the typename for the C binding and the Docbook
          <ulink
          url="http://www.docbook.org/tdg/en/html/primary.html">sortas
          attribute</ulink>.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>--generate-docbook</option> <replaceable>OUTFILES</replaceable></term>
      <listitem>
        <para>
          Generate Docbook Documentation for each D-Bus interface and
          put it in <filename>OUTFILES-NAME.xml</filename> where
          <literal>NAME</literal> is a place-holder for the interface
          name, e.g. <literal>net.Corp.FooBar</literal> and so on.
        </para>
        <para>
          Pass <option>--output-directory</option> to specify the directory
          to put the output files in. By default the current directory
          will be used.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>--generate-c-code</option> <replaceable>OUTFILES</replaceable></term>
      <listitem>
        <para>
          Generate C code for all D-Bus interfaces and put it in
          <filename>OUTFILES.c</filename> and
          <filename>OUTFILES.h</filename> including any sub-directories. If you want the files to
          be output in a different location use <option>--output-directory</option> as <filename>OUTFILES.h</filename>
          including sub-directories will be referenced from <filename>OUTFILES.c</filename>.
        </para>
        <para>
          The full paths would then be <literal>$(OUTDIR)/$(dirname $OUTFILES)/$(basename $OUTFILES).{c,h}</literal>.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>--c-namespace</option> <replaceable>YourProject</replaceable></term>
      <listitem>
        <para>
          The namespace to use for generated C code. This is expected
          to be in <ulink
          url="http://en.wikipedia.org/wiki/CamelCase">CamelCase</ulink>
          or <emphasis>Ugly_Case</emphasis> (see above).
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>--pragma-once</option></term>
      <listitem>
        <para>
          If this option is passed, the
          <ulink url="https://en.wikipedia.org/wiki/Pragma_once">&#35;pragma once</ulink>
          preprocessor directive is used instead of include guards.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>--c-generate-object-manager</option></term>
      <listitem>
        <para>
          If this option is passed, suitable #GDBusObject,
          #GDBusObjectProxy, #GDBusObjectSkeleton and
          #GDBusObjectManagerClient subclasses are generated.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>--c-generate-autocleanup</option> none|objects|all</term>
      <listitem>
        <para>
          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.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>--output-directory</option> <replaceable>OUTDIR</replaceable></term>
      <listitem>
        <para>
          Directory to output generated source to. Equivalent to changing directory before generation.
        </para>
        <para>
          This option cannot be used with <option>--body</option>,
          <option>--header</option>, <option>--interface-info-body</option> or
          <option>--interface-info-header</option>; and
          <option>--output</option> must be used.
        </para>

      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>--header</option></term>
      <listitem>
        <para>
          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 <option>--output</option>.
        </para>
        <para>
          Using <option>--generate-c-code</option>, <option>--generate-docbook</option> or
          <option>--output-directory</option> are not allowed to be used along with
          <option>--header</option> and <option>--body</option> options, because these options
          are used to generate only one file.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>--body</option></term>
      <listitem>
        <para>
          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 <option>--output</option>.
        </para>
        <para>
          Using <option>--generate-c-code</option>, <option>--generate-docbook</option> or
          <option>--output-directory</option> are not allowed to be used along with
          <option>--header</option> and <option>--body</option> options, because these options
          are used to generate only one file.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>--interface-info-header</option></term>
      <listitem>
        <para>
          If this option is passed, it will generate the header code for the
          <type>GDBusInterfaceInfo</type> structures only and will write it to
          the disk by using the path and file name provided by
          <option>--output</option>.
        </para>
        <para>
          Using <option>--generate-c-code</option>, <option>--generate-docbook</option> or
          <option>--output-directory</option> are not allowed to be used along with
          the <option>--interface-info-header</option> and
          <option>--interface-info-body</option> options, because these options
          are used to generate only one file.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>--interface-info-body</option></term>
      <listitem>
        <para>
          If this option is passed, it will generate the source code for the
          <type>GDBusInterfaceInfo</type> structures only and will write it to
          the disk by using the path and file name provided by
          <option>--output</option>.
        </para>
        <para>
          Using <option>--generate-c-code</option>, <option>--generate-docbook</option> or
          <option>--output-directory</option> are not allowed to be used along with
          the <option>--interface-info-header</option> and
          <option>--interface-info-body</option> options, because these options
          are used to generate only one file.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>--output</option> <replaceable>OUTFILE</replaceable></term>
      <listitem>
        <para>
          The full path where the header (<option>--header</option>,
          <option>--interface-info-header</option>) or the source code
          (<option>--body</option>, <option>--interface-info-body</option>) will
          be written, using the path and filename provided by
          <option>--output</option>. The full path could be something like
          <literal>$($OUTFILE).{c,h}</literal>.
        </para>
        <para>
          Using <option>--generate-c-code</option>, <option>--generate-docbook</option> or
          <option>--output-directory</option> is not allowed along with
          <option>--output</option>, because the latter is used to generate only one file.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>--annotate</option> <replaceable>ELEMENT</replaceable> <replaceable>KEY</replaceable> <replaceable>VALUE</replaceable></term>
      <listitem>
        <para>
          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:
        </para>
<informalexample><programlisting><![CDATA[
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
]]></programlisting></informalexample>
        <para>
          Any UTF-8 string can be used for <replaceable>KEY</replaceable> and <replaceable>VALUE</replaceable>.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>--glib-min-required</option> <replaceable>VERSION</replaceable></term>
      <listitem>
        <para>
          Specifies the minimum version of GLib which the code generated by
          <command>gdbus-codegen</command> can depend on. This may be used to
          make backwards-incompatible changes in the output or behaviour of
          <command>gdbus-codegen</command> in future, which users may opt in to
          by increasing the value they pass for <option>--glib-min-required</option>.
          If this option is not passed, the output from <command>gdbus-codegen</command>
          is guaranteed to be compatible with all versions of GLib from 2.30
          upwards, as that is when <command>gdbus-codegen</command> was first
          released.
        </para>
        <para>
          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.
        </para>
        <para>
          The version number must be of the form
          <literal><replaceable>MAJOR</replaceable>.<replaceable>MINOR</replaceable>.<replaceable>MICRO</replaceable></literal>,
          where all parts are integers. <replaceable>MINOR</replaceable> and
          <replaceable>MICRO</replaceable> are optional. The version number may not be smaller
          than <literal>2.30</literal>.
        </para>
        <para>
          If the version number is <literal>2.64</literal> or greater, the generated code will
          have the following features: (1) If a method has <literal>h</literal> (file
          descriptor) parameter(s), a <type>GUnixFDList</type> parameter will exist in the
          generated code for it (whereas previously the annotation
          <literal>org.gtk.GDBus.C.UnixFD</literal> was required), and (2) Method call functions will
          have two additional arguments to allow the user to specify <type>GDBusCallFlags</type>
          and a timeout value, as is possible when using <function>g_dbus_proxy_call()</function>.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>--glib-max-allowed</option> <replaceable>VERSION</replaceable></term>
      <listitem>
        <para>
          Specifies the maximum version of GLib which the code generated by
          <command>gdbus-codegen</command> can depend on. This may be used to
          ensure that code generated by <command>gdbus-codegen</command> is
          compilable with specific older versions of GLib that your software has
          to support.
        </para>
        <para>
          The version number must be of the form
          <literal><replaceable>MAJOR</replaceable>.<replaceable>MINOR</replaceable>.<replaceable>MICRO</replaceable></literal>,
          where all parts are integers. <replaceable>MINOR</replaceable> and
          <replaceable>MICRO</replaceable> are optional. The version number must
          be greater than or equal to that passed to <option>--glib-min-required</option>.
          It defaults to the version of GLib which provides this <command>gdbus-codegen</command>.
        </para>
      </listitem>
    </varlistentry>

  </variablelist>
</refsect1>

<refsect1>
  <title>Supported D-Bus Annotations</title>
  <para>
    The following D-Bus annotations are supported by
    <command>gdbus-codegen</command>:
  </para>

  <variablelist>

    <varlistentry>
      <term><literal>org.freedesktop.DBus.Deprecated</literal></term>
      <listitem>
        <para>
          Can be used on any <literal>&lt;interface&gt;</literal>,
          <literal>&lt;method&gt;</literal>,
          <literal>&lt;signal&gt;</literal> and
          <literal>&lt;property&gt;</literal> element to specify that
          the element is deprecated if its value is
          <literal>true</literal>. Note that this annotation is
          defined in the <ulink
          url="http://dbus.freedesktop.org/doc/dbus-specification.html#introspection-format">D-Bus
          specification</ulink> and can only assume the values
          <literal>true</literal> and <literal>false</literal>. 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.
        </para>
        <para>
          When generating C code, this annotation is used to add
          #G_GNUC_DEPRECATED to generated functions for the element.
        </para>
        <para>
          When generating Docbook XML, a deprecation warning will
          appear along the documentation for the element.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><literal>org.gtk.GDBus.Since</literal></term>
      <listitem>
        <para>
          Can be used on any <literal>&lt;interface&gt;</literal>,
          <literal>&lt;method&gt;</literal>,
          <literal>&lt;signal&gt;</literal> and
          <literal>&lt;property&gt;</literal> element to specify the
          version (any free-form string but compared using a
          version-aware sort function) the element appeared in.
        </para>
        <para>
          When generating C code, this field is used to ensure
          function pointer order for preserving ABI/API, see <xref
          linkend="gdbus-code-stability"/>.
        </para>
        <para>
          When generating Docbook XML, the value of this tag appears
          in the documentation.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><literal>org.gtk.GDBus.DocString</literal></term>
      <listitem>
        <para>
          A string with Docbook content for documentation. This annotation can
          be used on <literal>&lt;interface&gt;</literal>,
          <literal>&lt;method&gt;</literal>,
          <literal>&lt;signal&gt;</literal>,
          <literal>&lt;property&gt;</literal> and
          <literal>&lt;arg&gt;</literal> elements.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><literal>org.gtk.GDBus.DocString.Short</literal></term>
      <listitem>
        <para>
          A string with Docbook content for short/brief
          documentation. This annotation can only be used on
          <literal>&lt;interface&gt;</literal> elements.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><literal>org.gtk.GDBus.C.Name</literal></term>
      <listitem>
        <para>
          Can be used on any <literal>&lt;interface&gt;</literal>,
          <literal>&lt;method&gt;</literal>,
          <literal>&lt;signal&gt;</literal> and
          <literal>&lt;property&gt;</literal> element to specify the
          name to use when generating C code. The value is expected to
          be in <ulink
          url="http://en.wikipedia.org/wiki/CamelCase">CamelCase</ulink>
          or <emphasis>Ugly_Case</emphasis> (see above).
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><literal>org.gtk.GDBus.C.ForceGVariant</literal></term>
      <listitem>
        <para>
          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 <literal>&lt;arg&gt;</literal> and
          <literal>&lt;property&gt;</literal> element.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><literal>org.gtk.GDBus.C.UnixFD</literal></term>
      <listitem>
        <para>
          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
          <literal>&lt;method&gt;</literal> elements.
        </para>
      </listitem>
    </varlistentry>

  </variablelist>

  <para>
    As an easier alternative to using the
    <literal>org.gtk.GDBus.DocString</literal> annotation, note that
    parser used by <command>gdbus-codegen</command> parses XML
    comments in a way similar to <ulink
    url="http://www.gtk.org/gtk-doc/">gtk-doc</ulink>:
<informalexample><programlisting><![CDATA[
<!--
  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>
]]></programlisting></informalexample>
  </para>
  <para>
    Note that <literal><![CDATA[@since]]></literal> can be used in any inline
    documentation bit (e.g. for interfaces, methods, signals and
    properties) to set the <literal>org.gtk.GDBus.Since</literal>
    annotation. For the <literal>org.gtk.GDBus.DocString</literal>
    annotation (and inline comments), note that substrings of the form
    <literal><![CDATA[#net.Corp.Bar]]></literal>,
    <literal><![CDATA[net.Corp.Bar.FooMethod()]]></literal>,
    <literal><![CDATA[#net.Corp.Bar::BarSignal]]></literal> and
    <literal><![CDATA[#net.Corp.InlineDocs:BazProperty]]></literal> are all
    expanded to links to the respective interface, method, signal and
    property.
    Additionally, substrings starting with <literal>@</literal> and <literal>%</literal> characters are rendered as
    <ulink url="http://www.docbook.org/tdg/en/html/parameter.html">parameter</ulink> and
    <ulink url="http://www.docbook.org/tdg/en/html/constant.html">constant</ulink> respectively.
  </para>
  <para>
    If both XML comments and
    <literal>org.gtk.GDBus.DocString</literal> or
    <literal>org.gtk.GDBus.DocString.Short</literal> annotations are
    present, the latter wins.
  </para>
</refsect1>

<refsect1>
  <title>Example</title>
  <para>
    Consider the following D-Bus Introspection XML.
  </para>
  <informalexample><programlisting><![CDATA[
<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>
]]></programlisting>
  </informalexample>
  <para>
    If <command>gdbus-codegen</command> is used on this file like this:
  </para>
<informalexample><programlisting><![CDATA[
gdbus-codegen --generate-c-code myapp-generated       \
              --c-namespace MyApp                     \
              --interface-prefix net.corp.MyApp.      \
              net.Corp.MyApp.Frobber.xml
]]></programlisting></informalexample>
  <para>
    two files called
    <filename>myapp-generated.[ch]</filename> are
    generated. The files provide an abstract
    #GTypeInterface<!-- -->-derived type called
    <type>MyAppFrobber</type> as well as two instantiable types with
    the same name but suffixed with <type>Proxy</type> and
    <type>Skeleton</type>. The generated file, roughly, contains the
    following facilities:
  </para>
<informalexample><programlisting><![CDATA[
/* 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,
                                 gpointer 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);
]]></programlisting></informalexample>
  <para>
    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:
  </para>
  <informaltable>
    <tgroup cols="3">
      <thead>
        <row>
          <entry></entry>
          <entry>Client</entry>
          <entry>Server</entry>
        </row>
      </thead>
      <tbody>
        <row>
          <entry>Types</entry>
          <entry>Use <type>MyAppFrobberProxy</type></entry>
          <entry>Any type implementing the <type>MyAppFrobber</type> interface</entry>
        </row>
        <row>
          <entry>Methods</entry>
          <entry>Use <function>m_a_f_hello_world()</function> to call.</entry>
          <entry>Receive via the <function>handle_hello_world()</function> signal handler. Complete the call with <function>m_a_f_complete_hello_world()</function></entry>
        </row>
        <row>
          <entry>Signals</entry>
          <entry>Connect to the <function>::notification</function> GObject signal.</entry>
          <entry>Use <function>m_a_f_emit_notification()</function> to emit signal.</entry>
        </row>
        <row>
          <entry>Properties (Reading)</entry>
          <entry>Use <function>m_a_f_get_verbose()</function> or <parameter>:verbose</parameter>.</entry>
          <entry>Implement #GObject<!-- -->'s <function>get_property()</function> vfunc.</entry>
        </row>
        <row>
          <entry>Properties (writing)</entry>
          <entry>Use <function>m_a_f_set_verbose()</function> or <parameter>:verbose</parameter>.</entry>
          <entry>Implement #GObject<!-- -->'s <function>set_property()</function> vfunc.</entry>
        </row>
      </tbody>
    </tgroup>
  </informaltable>

  <refsect2>
    <title>Client-side usage</title>
    <para>
      You can use the generated proxy type with the generated
      constructors:
    </para>
    <informalexample><programlisting><![CDATA[
    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);
]]></programlisting></informalexample>
    <para>
      Instead of using the generic #GDBusProxy facilities, one can use
      the generated methods such as
      <function>my_app_frobber_call_hello_world()</function> to invoke
      the <function>net.Corp.MyApp.Frobber.HelloWorld()</function>
      D-Bus method, connect to the
      <function>::notification</function> GObject signal to receive
      the <function>net.Corp.MyApp.Frobber::Notication</function>
      D-Bus signal and get/set the
      <parameter>net.Corp.MyApp.Frobber:Verbose</parameter> D-Bus
      Property using either the GObject property
      <parameter>:verbose</parameter> or the
      <function>my_app_get_verbose()</function> and
      <function>my_app_set_verbose()</function> methods. Use the
      standard #GObject::notify signal to listen to property changes.
    </para>
    <para>
      Note that all property access is via #GDBusProxy<!-- -->'s
      property cache so no I/O is ever done when reading properties.
      Also note that setting a property will cause the
      <ulink url="http://dbus.freedesktop.org/doc/dbus-specification.html#standard-interfaces-properties">org.freedesktop.DBus.Properties.Set</ulink> method 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.
    </para>
  </refsect2>

  <refsect2>
    <title>Server-side usage</title>
    <para>
      The generated <type>MyAppFrobber</type> interface is designed so
      it is easy to implement it in a #GObject
      subclass. For example, to handle
      <function>HelloWorld()</function> method invocations, set the
      vfunc for <function>handle_hello_hello_world()</function> in the
      <type>MyAppFrobberIface</type> structure. Similarly, to handle
      the <parameter>net.Corp.MyApp.Frobber:Verbose</parameter>
      property override the <parameter>:verbose</parameter> #GObject
      property from the subclass. To emit a signal, use
      e.g. <function>my_app_emit_signal()</function> or
      g_signal_emit_by_name().
    </para>
    <para>
      Instead of subclassing, it is often easier to use the generated
      <type>MyAppFrobberSkeleton</type> subclass. To handle incoming
      method calls, use <function>g_signal_connect()</function> with
      the <function>::handle-*</function> signals and instead of
      overriding #GObject<!-- -->'s
      <function>get_property()</function> and
      <function>set_property()</function> vfuncs, use
      g_object_get() and
      g_object_set() or the generated property
      getters and setters (the generated class has an internal
      property bag implementation).
    </para>
    <informalexample><programlisting><![CDATA[
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 */
    }
]]></programlisting></informalexample>
    <para>
      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
      <link linkend="g-main-context-push-thread-default">thread-default main loop</link>
      of the thread where the skeleton object was
      constructed) and will cause emissions of the <ulink
      url="http://dbus.freedesktop.org/doc/dbus-specification.html#standard-interfaces-properties">org.freedesktop.DBus.Properties::PropertiesChanged</ulink>
      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.
    </para>
  </refsect2>
</refsect1>

<refsect1>
  <title>C Type Mapping</title>
  <para>
    Scalar types
    (type-strings
    <link linkend="G-VARIANT-TYPE-BOOLEAN:CAPS">'b'</link>,
    <link linkend="G-VARIANT-TYPE-BYTE:CAPS">'y'</link>,
    <link linkend="G-VARIANT-TYPE-INT16:CAPS">'n'</link>,
    <link linkend="G-VARIANT-TYPE-UINT16:CAPS">'q'</link>,
    <link linkend="G-VARIANT-TYPE-INT32:CAPS">'i'</link>,
    <link linkend="G-VARIANT-TYPE-UINT32:CAPS">'u'</link>,
    <link linkend="G-VARIANT-TYPE-INT64:CAPS">'x'</link>,
    <link linkend="G-VARIANT-TYPE-UINT64:CAPS">'t'</link> and
    <link linkend="G-VARIANT-TYPE-DOUBLE:CAPS">'d'</link>)
    ),
    strings (type-strings
    <link linkend="G-VARIANT-TYPE-STRING:CAPS">'s'</link>,
    <link linkend="G-VARIANT-TYPE-BYTESTRING:CAPS">'ay'</link>,
    <link linkend="G-VARIANT-TYPE-OBJECT-PATH:CAPS">'o'</link> and
    <link linkend="G-VARIANT-TYPE-SIGNATURE:CAPS">'g'</link>) and
    arrays of string (type-strings
    <link linkend="G-VARIANT-TYPE-STRING-ARRAY:CAPS">'as'</link>,
    <link linkend="G-VARIANT-TYPE-OBJECT-PATH-ARRAY:CAPS">'ao'</link> and
    <link linkend="G-VARIANT-TYPE-BYTESTRING-ARRAY:CAPS">'aay'</link>)
    are mapped to the natural types,
    e.g. #gboolean, #gdouble, #gint, <link linkend="gchararray">gchar*</link>,
    <link linkend="GStrv">gchar**</link> and
    so on. Everything else is mapped to the #GVariant
    type.
  </para>
  <para>
    This automatic mapping can be turned off by using the annotation
    <literal>org.gtk.GDBus.C.ForceGVariant</literal> - 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 <link linkend="G-VARIANT-TYPE-BYTESTRING:CAPS">'ay'</link>)
    for data that could have embedded NUL bytes.
  </para>
</refsect1>

<refsect1 id="gdbus-code-stability">
  <title>Stability Guarantees</title>
  <para>
    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 its C ABI either. The ABI of the generated instance and
    class structures will be preserved as well.
  </para>
  <para>
    The ABI of the generated #GType<!-- -->s will be preserved only if
    the <literal>org.gtk.GDBus.Since</literal> annotation is used
    judiciously — this is because the VTable for the #GInterface
    relies on functions 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 they <literal>org.gtk.GDBus.Since</literal> annotation using
    a greater version number than previous versions.
  </para>
  <para>
    The generated C code currently happens to be annotated with <ulink
    url="http://www.gtk.org/gtk-doc/">gtk-doc</ulink> / <ulink
    url="https://wiki.gnome.org/Projects/GObjectIntrospection">GObject
    Introspection</ulink> comments / annotations. The layout and
    contents might change in the future so no guarantees about
    e.g. <literal>SECTION</literal> usage etc. is given.
  </para>
  <para>
    While the generated Docbook for D-Bus interfaces isn't expected to
    change, no guarantees are given at this point.
  </para>
  <para>
    It is important to note that the generated code should not be
    checked into revision control systems, nor it should be included
    in distributed source archives.
  </para>
</refsect1>

<refsect1>
  <title>Bugs</title>
  <para>
    Please send bug reports to either the distribution bug tracker
    or the upstream bug tracker at
    <ulink url="https://gitlab.gnome.org/GNOME/glib/issues/new">https://gitlab.gnome.org/GNOME/glib/issues/new</ulink>.
  </para>
</refsect1>

<refsect1>
  <title>See also</title>
  <para>
    <citerefentry>
      <refentrytitle>gdbus</refentrytitle><manvolnum>1</manvolnum>
    </citerefentry>
  </para>
</refsect1>

</refentry>