GDBUS-CODEGEN(1) User Commands GDBUS-CODEGEN(1)
NAME
gdbus-codegen - D-Bus code and documentation generator
SYNOPSIS
gdbus-codegen [-h, --help] [--interface-prefix org.project.Prefix] [--generate-c-code OUTFILES] [--c-namespace YourProject]
[--c-generate-object-manager] [--generate-docbook OUTFILES] [--xml-files FILE] [--annotate ELEMENT KEY VALUE]... FILE
[FILE...]
DESCRIPTION
gdbus-codegen is used to generate code and/or documentation for one or more D-Bus interfaces. The tool reads D-Bus Introspection XML[1]
files and generates output files. The tool currently supports generating C code (via --generate-c-code) and Docbook XML (via
--generate-docbook).
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 instantiable 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.
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-prefixorg.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[2] article describing the D-Bus interface.
OPTIONS
The following options are supported:
-h, --help
Show help and exit.
--xml-files FILE
The D-Bus introspection XML file.
--interface-prefix org.project.Prefix.
A prefix to strip from all D-Bus interface names when calculating the typename for the C binding and the Docbook sortas attribute[3].
--generate-docbook OUTFILES
Generate Docbook Documentation for each D-Bus interface and put it in OUTFILES-NAME.xml where NAME is a place-holder for the interface
name, e.g. net.Corp.FooBar and so on.
--generate-c-code OUTFILES
Generate C code for all D-Bus interfaces and put it in OUTFILES.c and OUTFILES.h.
--c-namespace YourProject
The namespace to use for generated C code. This is expected to be in CamelCase[4] or Ugly_Case (see above).
--c-generate-object-manager
If this option is passed, suitable #GDBusObject, #GDBusObjectProxy, #GDBusObjectSkeleton and #GDBusObjectManagerClient subclasses are
generated.
--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.
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[1] 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 the section called "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[4] 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[5]:
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[6]
and constant[7] 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 instantiable 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,
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);
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:
+---------------------+--------------------------------------+--------------------------------------+
| | 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 | Use m_a_f_emit_notification() to |
| | GObject signal. | emit signal. |
+---------------------+--------------------------------------+--------------------------------------+
|Properties (Reading) | Use m_a_f_get_verbose() or :verbose. | Implement #GObject's get_property() |
| | | vfunc. |
+---------------------+--------------------------------------+--------------------------------------+
|Properties (writing) | Use m_a_f_set_verbose() or :verbose. | Implement #GObject's set_property() |
| | | vfunc. |
+---------------------+--------------------------------------+--------------------------------------+
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 the ::notification GObject signal to receive the
net.Corp.MyApp.Frobber::Notication 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 #GDBusProxy 's 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[8] 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.
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. Similary, 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 #GObject 's get_property() and set_property() 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).
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
contructed) and will cause emissions of the org.freedesktop.DBus.Properties::PropertiesChanged[8] 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 and and and 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
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 its C ABI either.
The ABI of the generated #GType s will be preserved only if the org.gtk.GDBus.Since 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 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[5] / GObject Introspection[9] comments / annotations. The layout and
contents might change in the future so no guarantees about e.g. SECTION usage etc. is given.
While the generated Docbook for D-Bus interfaces isn't expected to change, no guarantees are given at this point.
BUGS
Please send bug reports to either the distribution bug tracker or the upstream bug tracker at
https://bugzilla.gnome.org/enter_bug.cgi?product=glib.
SEE ALSO
gdbus(1)
NOTES
1. D-Bus Introspection XML
http://dbus.freedesktop.org/doc/dbus-specification.html#introspection-format
2. RefEntry
http://www.docbook.org/tdg/en/html/refentry.html
3. sortas attribute
http://www.docbook.org/tdg/en/html/primary.html
4. CamelCase
http://en.wikipedia.org/wiki/CamelCase
5. gtk-doc
http://www.gtk.org/gtk-doc/
6. parameter
http://www.docbook.org/tdg/en/html/parameter.html
7. constant
http://www.docbook.org/tdg/en/html/constant.html
8. org.freedesktop.DBus.Properties.Set
http://dbus.freedesktop.org/doc/dbus-specification.html#standard-interfaces-properties
9. GObject Introspection
https://live.gnome.org/GObjectIntrospection
GIO
GDBUS-CODEGEN(1)