glib/docs/reference/gio/gdbus-codegen.xml
Emmanuele Bassi f2c4eb8cbb docs: Mention that generated code should not be kept
Code generated by gdbus-codegen should neither be checked in into
revision control, nor should be distributed.

https://bugzilla.gnome.org/show_bug.cgi?id=710133
2013-10-28 12:47:16 -04:00

880 lines
33 KiB
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>--generate-docbook</option> <replaceable>OUTFILES</replaceable></arg>
<arg><option>--xml-files</option> <replaceable>FILE</replaceable></arg>
<group choice="plain" rep="repeat">
<arg>
<option>--annotate</option>
<replaceable>ELEMENT</replaceable>
<replaceable>KEY</replaceable>
<replaceable>VALUE</replaceable>
</arg>
</group>
<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. The tool reads
<ulink
url="http://dbus.freedesktop.org/doc/dbus-specification.html#introspection-format">D-Bus
Introspection XML</ulink> files and generates output files. The
tool currently supports generating C code (via
<option>--generate-c-code</option>) and Docbook XML (via
<option>--generate-docbook</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>
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>
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>
</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>.
</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>--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>--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>
</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 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. Similary, 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
contructed) 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://live.gnome.org/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://bugzilla.gnome.org/enter_bug.cgi?product=glib">https://bugzilla.gnome.org/enter_bug.cgi?product=glib</ulink>.
</para>
</refsect1>
<refsect1>
<title>See also</title>
<para>
<citerefentry>
<refentrytitle>gdbus</refentrytitle><manvolnum>1</manvolnum>
</citerefentry>
</para>
</refsect1>
</refentry>