| GDBUS-CODEGEN() | GDBUS-CODEGEN() |
NAME¶
gdbus-codegen - D-Bus code and documentation generator
SYNOPSIS¶
gdbus-codegen
[--help] [--interface-prefix org.project.Prefix] [--header | --body | --interface-info-header | --interface-info-body | --generate-c-code OUTFILES] [--c-namespace YourProject] [--c-generate-object-manager] [--c-generate-autocleanup none|objects|all] [--output-directory OUTDIR | --output OUTFILE] [--generate-docbook OUTFILES] [--generate-rst OUTFILES] [--pragma-once] [--xml-files FILE] [--symbol-decorator DECORATOR [--symbol-decorator-header HEADER] [--symbol-decorator-define DEFINE]] [--annotate ELEMENT KEY VALUE]… [--glib-min-required VERSION] [--glib-max-allowed VERSION] FILE…
DESCRIPTION¶
gdbus-codegen is used to generate code and/or documentation for one or more D-Bus interfaces.
gdbus-codegen reads D-Bus Introspection XML <https://dbus.freedesktop.org/doc/dbus-specification.html#introspection-format>
from files passed as additional arguments on the command line and generates output files. It currently supports generating C source code (via --body) or header (via --header) and DocBook XML (via --generate-docbook). Alternatively, more restricted C source code and headers can be generated, which just contain the interface information (as GDBusInterfaceInfo structures) using --interface-info-body and --interface-info-header.
GENERATING C CODE¶
When generating C code, a GInterface derived type is generated for each D-Bus interface. Additionally, for every generated type, FooBar, two concrete instantiatable types, FooBarProxy and FooBarSkeleton, implementing said interface are also generated. The former is derived from GDBusProxy and intended for use on the client side while the latter is derived from the GDBusInterfaceSkeleton type making it easy to export on a GDBusConnection either directly or via a GDBusObjectManagerServer instance.
For C code generation either --body that generates source code, --header that generates headers, --interface-info-body that generates interface information source code, or --interface-info-header that generates interface information headers, can be used. These options must be used along with --output, which is used to specify the file to output to.
Both files can be generated at the same time by using --generate-c-code, but this option is deprecated. In this case --output cannot be used due to the generation of multiple files. Instead pass --output-directory to specify the directory to put the output files in. By default the current directory will be used.
The name of each generated C type is derived from the D-Bus interface name stripped with the prefix given with --interface-prefix and with the dots removed and initial characters capitalized. For example, for the D-Bus interface com.acme.Coyote the name used is ComAcmeCoyote. For the D-Bus interface org.project.Bar.Frobnicator with --interface-prefix set to org.project., the name used is BarFrobnicator.
For methods, signals and properties, if not specified, the name defaults to the name of the method, signal or property.
Two forms of the name are used — the CamelCase form and the lower-case form. The CamelCase form is used for the GType and struct name, while lower-case form is used in function names. The lower-case form is calculated by converting from CamelCase to lower-case and inserting underscores at word boundaries (using certain heuristics).
If the value given by the org.gtk.GDBus.C.Name annotation or the --c-namespace option contains an underscore (sometimes called Ugly_Case), then the camel-case name is derived by removing all underscores, and the lower-case name is derived by lower-casing the string. This is useful in some situations where abbreviations are used. For example, if the annotation is used on the interface net.MyCorp.MyApp.iSCSITarget with the value iSCSI_Target the CamelCase form is iSCSITarget while the lower-case form is iscsi_target. If the annotation is used on the method EjectTheiPod with the value Eject_The_iPod, the lower-case form is eject_the_ipod.
GENERATING DOCBOOK DOCUMENTATION¶
Each generated DocBook XML file (see the --generate-docbook option for details) is a RefEntry article describing the D-Bus interface. (See the DocBook documentation <https://tdg.docbook.org/tdg/4.5/refentry.html> .)
GENERATING RESTRUCTUREDTEXT DOCUMENTATION¶
Each generated reStructuredText file (see the
--generate-rst option for details) is a plain text reStructuredText
<https://docutils.sourceforge.io/rst.html>
document describing the D-Bus interface.
OPTIONS¶
The following options are supported:
-h, --help
--xml-files FILE
--interface-prefix org.project.Prefix.
--generate-docbook OUTFILES
Pass --output-directory to specify the directory to put the output files in. By default the current directory will be used.
--generate-rst OUTFILES
Pass --output-directory to specify the directory to put the output files in. By default the current directory will be used.
--generate-c-code OUTFILES
The full paths would then be $(OUTDIR)/$(dirname $OUTFILES)/$(basename $OUTFILES).{c,h}.
--c-namespace YourProject
or Ugly_Case (see above).
--pragma-once
preprocessor directive is used instead of include guards.
--c-generate-object-manager
--c-generate-autocleanup none|objects|all
--output-directory OUTDIR
This option cannot be used with --body, --header, --interface-info-body or --interface-info-header; and --output must be used.
--header
Using --generate-c-code, --generate-docbook or --output-directory are not allowed to be used along with --header and --body options, because these options are used to generate only one file.
--body
Using --generate-c-code, --generate-docbook or --output-directory are not allowed to be used along with --header and --body options, because these options are used to generate only one file.
--interface-info-header
Using --generate-c-code, --generate-docbook or --output-directory are not allowed to be used along with the --interface-info-header and --interface-info-body options, because these options are used to generate only one file.
--interface-info-body
Using --generate-c-code, --generate-docbook or --output-directory are not allowed to be used along with the --interface-info-header and --interface-info-body options, because these options are used to generate only one file.
--symbol-decorator DECORATOR
This option was added in GLib 2.66.
--symbol-decorator-header HEADER
This option was added in GLib 2.66.
This option can only be used if --symbol-decorator is used.
--symbol-decorator-define DEFINE
This option was added in GLib 2.66.
This option can only be used if --symbol-decorator is used.
--output OUTFILE
Using --generate-c-code, --generate-docbook or --output-directory is not allowed along with --output, because the latter is used to generate only one file.
Since GLib 2.80, if OUTFILE is the literal string -, the header or source code will be written to standard output.
For --body and --interface-info-body, the generated code will not automatically #include a corresponding header file when writing to standard output, because there is no obvious name for that header file. This might make it necessary to use cc -include foo.h, or generate a filename like foo-impl.h and #include it into a wrapper .c file.
For --header and --interface-info-header, there is no obvious name for a traditional multiple-inclusion guard when writing to standard output, so using the --pragma-once option is recommended.
In the rare situation that the intended output filename starts with -, it should be prefixed with ./.
--annotate ELEMENT KEY VALUE
gdbus-codegen --c-namespace MyApp \
--generate-c-code myapp-generated \
--annotate "org.project.InterfaceName" \
org.gtk.GDBus.C.Name MyFrobnicator \
--annotate "org.project.InterfaceName:Property" \
bar bat \
--annotate "org.project.InterfaceName.Method()" \
org.freedesktop.DBus.Deprecated true \
--annotate "org.project.InterfaceName.Method()[arg_name]" \
snake hiss \
--annotate "org.project.InterfaceName::Signal" \
cat meow \
--annotate "org.project.InterfaceName::Signal[arg_name]" \
dog wuff \
myapp-dbus-interfaces.xml
Any UTF-8 string can be used for KEY and VALUE.
--glib-min-required VERSION
Note that some version parameters introduce incompatible changes: all callers of the generated code might need to be updated, and if the generated code is part of a library’s API or ABI, then increasing the version parameter can result in an API or ABI break.
The version number must be of the form MAJOR.MINOR.MICRO, where all parts are integers. MINOR and MICRO are optional. The version number may not be smaller than 2.30.
If the version number is 2.64 or greater, the generated code will have the following features:
- 1.
- If a method has h (file descriptor) parameter(s), a GUnixFDList parameter will exist in the generated code for it (whereas previously the annotation org.gtk.GDBus.C.UnixFD was required), and
- 2.
- Method call functions will have two additional arguments to allow the user to specify GDBusCallFlags and a timeout value, as is possible when using g_dbus_proxy_call().
--glib-max-allowed VERSION
The version number must be of the form MAJOR.MINOR.MICRO, where all parts are integers. MINOR and MICRO are optional. The version number must be greater than or equal to that passed to --glib-min-required. It defaults to the version of GLib which provides this gdbus-codegen.
SUPPORTED D-BUS ANNOTATIONS¶
The following D-Bus annotations are supported by gdbus-codegen:
org.freedesktop.DBus.Deprecated
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
When generating C code, this field is used to ensure function pointer order for preserving ABI/API, see ‘STABILITY GUARANTEES’.
When generating DocBook XML, the value of this tag appears in the documentation.
org.gtk.GDBus.DocString
org.gtk.GDBus.DocString.Short
org.gtk.GDBus.C.Name
or Ugly_Case (see above).
org.gtk.GDBus.C.ForceGVariant
org.gtk.GDBus.C.UnixFD
As an easier alternative to using the org.gtk.GDBus.DocString annotation, note that parser used by gdbus-codegen parses XML comments in a way similar to gtk-doc <https://gitlab.gnome.org/GNOME/gtk-doc/> :
<!--
net.Corp.Bar:
@short_description: A short description
A <emphasis>longer</emphasis> description.
This is a new paragraph. --> <interface name="net.corp.Bar">
<!--
FooMethod:
@greeting: The docs for greeting parameter.
@response: The docs for response parameter.
The docs for the actual method.
-->
<method name="FooMethod">
<arg name="greeting" direction="in" type="s"/>
<arg name="response" direction="out" type="s"/>
</method>
<!--
BarSignal:
@blah: The docs for blah parameter.
@boo: The docs for boo parameter.
@since: 2.30
The docs for the actual signal.
-->
<signal name="BarSignal">
<arg name="blah" type="s"/>
<arg name="boo" type="s"/>
</signal>
<!-- BazProperty: The docs for the property. -->
<property name="BazProperty" type="s" access="read"/> </interface>
Note that @since can be used in any inline documentation
bit (e.g. for interfaces, methods, signals and properties) to set the
org.gtk.GDBus.Since annotation. For the
org.gtk.GDBus.DocString annotation (and inline comments), note that
substrings of the form #net.Corp.Bar,
net.Corp.Bar.FooMethod(), #net.Corp.Bar::BarSignal and
#net.Corp.InlineDocs:BazProperty are all expanded to links to the
respective interface, method, signal and property. Additionally, substrings
starting with @ and % characters are rendered as parameter
<https://tdg.docbook.org/tdg/4.5/parameter.html>
and constant <https://tdg.docbook.org/tdg/4.5/constant.html>
respectively.
If both XML comments and org.gtk.GDBus.DocString or org.gtk.GDBus.DocString.Short annotations are present, the latter wins.
EXAMPLE¶
Consider the following D-Bus Introspection XML:
<node>
<interface name="net.Corp.MyApp.Frobber">
<method name="HelloWorld">
<arg name="greeting" direction="in" type="s"/>
<arg name="response" direction="out" type="s"/>
</method>
<signal name="Notification">
<arg name="icon_blob" type="ay"/>
<arg name="height" type="i"/>
<arg name="messages" type="as"/>
</signal>
<property name="Verbose" type="b" access="readwrite"/>
</interface> </node>
If gdbus-codegen is used on this file like this:
gdbus-codegen --generate-c-code myapp-generated \
--c-namespace MyApp \
--interface-prefix net.corp.MyApp. \
net.Corp.MyApp.Frobber.xml
two files called myapp-generated.[ch] are generated. The files provide an abstract GTypeInterface derived type called MyAppFrobber as well as two instantiatable types with the same name but suffixed with Proxy and Skeleton. The generated file, roughly, contains the following facilities:
/* GType macros for the three generated types */
#define MY_APP_TYPE_FROBBER (my_app_frobber_get_type ())
#define MY_APP_TYPE_FROBBER_SKELETON (my_app_frobber_skeleton_get_type ())
#define MY_APP_TYPE_FROBBER_PROXY (my_app_frobber_proxy_get_type ())
typedef struct _MyAppFrobber MyAppFrobber; /* Dummy typedef */
typedef struct
{
GTypeInterface parent_iface;
/* Signal handler for the ::notification signal */
void (*notification) (MyAppFrobber *proxy,
GVariant *icon_blob,
gint height,
const gchar* const *messages);
/* Signal handler for the ::handle-hello-world signal */
gboolean (*handle_hello_world) (MyAppFrobber *proxy,
GDBusMethodInvocation *invocation,
const gchar *greeting);
} MyAppFrobberIface;
/* Asynchronously calls HelloWorld() */
void
my_app_frobber_call_hello_world (MyAppFrobber *proxy,
const gchar *greeting,
GCancellable *cancellable,
GAsyncReadyCallback callback,
gp ointer user_data);
gboolean
my_app_frobber_call_hello_world_finish (MyAppFrobber *proxy,
gchar **out_response,
GAsyncResult *res,
GError **error);
/* Synchronously calls HelloWorld(). Blocks calling thread. */
gboolean
my_app_frobber_call_hello_world_sync (MyAppFrobber *proxy,
const gchar *greeting,
gchar **out_response,
GCancellable *cancellable,
GError **error);
/* Completes handling the HelloWorld() method call */
void
my_app_frobber_complete_hello_world (MyAppFrobber *object,
GDBusMethodInvocation *invocation,
const gchar *response);
/* Emits the ::notification signal / Notification() D-Bus signal */
void
my_app_frobber_emit_notification (MyAppFrobber *object,
GVariant *icon_blob,
gint height,
const gchar* const *messages);
/* Gets the :verbose GObject property / Verbose D-Bus property.
* Does no blocking I/O.
*/
gboolean my_app_frobber_get_verbose (MyAppFrobber *object);
/* Sets the :verbose GObject property / Verbose D-Bus property.
* Does no blocking I/O.
*/
void my_app_frobber_set_verbose (MyAppFrobber *object,
gboolean value);
/* Gets the interface info */
GDBusInterfaceInfo *my_app_frobber_interface_info (void);
/* Creates a new skeleton object, ready to be exported */
MyAppFrobber *my_app_frobber_skeleton_new (void);
/* Client-side proxy constructors.
*
* Additionally, _new_for_bus(), _new_for_bus_finish() and
* _new_for_bus_sync() proxy constructors are also generated.
*/
void
my_app_frobber_proxy_new (GDBusConnection *connection,
GDBusProxyFlags flags,
const gchar *name,
const gchar *object_path,
GCancellable *cancellable,
GAsyncReadyCallback callback,
gpointer user_data);
MyAppFrobber *
my_app_frobber_proxy_new_finish (GAsyncResult *res,
GError **error);
MyAppFrobber *
my_app_frobber_proxy_new_sync (GDBusConnection *connection,
GDBusProxyFlags flags,
const gchar *name,
const gchar *object_path,
GCancellable *cancellable,
GError **error);
Thus, for every D-Bus method, there will be three C functions for calling the method, one GObject signal for handling an incoming call and one C function for completing an incoming call. For every D-Bus signal, there’s one GObject signal and one C function for emitting it. For every D-Bus property, two C functions are generated (one setter, one getter) and one GObject property. The following table summarizes the generated facilities and where they are applicable:
| Symbol type | Client | Server |
| Types | Use MyAppFrobberProxy. | Any type implementing the MyAppFrobber interface. |
| Methods | Use m_a_f_hello_world() to call. | Receive via the handle_hello_world() signal handler. Complete the call with m_a_f_complete_hello_world(). |
| Signals | Connect to the ::notification signal. | Use m_a_f_emit_notification() to emit signal. |
| Properties (Reading) | Use m_a_f_get_verbose() or the :verbose property. | Implement the get_property() vfunc of GObject. |
| Properties (writing) | Use m_a_f_set_verbose() or the :verbose property. | Implement the set_property() vfunc of GObject. |
Client-side usage¶
You can use the generated proxy type with the generated constructors:
MyAppFrobber *proxy; GError *error; error = NULL; proxy = my_app_frobber_proxy_new_for_bus_sync (
G_BUS_TYPE_SESSION,
G_DBUS_PROXY_FLAGS_NONE,
"net.Corp.MyApp", /* bus name */
"/net/Corp/MyApp/SomeFrobber", /* object */
NULL, /* GCancellable* */
&error); /* do stuff with proxy */ g_object_unref (proxy);
Instead of using the generic GDBusProxy facilities, one can use the generated methods such as my_app_frobber_call_hello_world() to invoke the net.Corp.MyApp.Frobber.HelloWorld() D-Bus method, connect to the ::notification GObject signal to receive the net.Corp.MyApp.Frobber::Notification D-Bus signal and get/set the net.Corp.MyApp.Frobber:Verbose D-Bus Property using either the GObject property :verbose or the my_app_get_verbose() and my_app_set_verbose() methods. Use the standard GObject::notify signal to listen to property changes.
Note that all property access is via the GDBusProxy property cache so no I/O is ever done when reading properties. Also note that setting a property will cause the org.freedesktop.DBus.Properties.Set method (documentation <https://dbus.freedesktop.org/doc/dbus-specification.html#standard-interfaces-properties> ) to be called on the remote object. This call, however, is asynchronous so setting a property won’t block. Further, the change is delayed and no error checking is possible.
Server-side usage¶
The generated MyAppFrobber interface is designed so it is easy to implement it in a GObject subclass. For example, to handle HelloWorld() method invocations, set the vfunc for handle_hello_hello_world() in the MyAppFrobberIface structure. Similarly, to handle the net.Corp.MyApp.Frobber:Verbose property override the :verbose GObject property from the subclass. To emit a signal, use e.g. my_app_emit_signal() or g_signal_emit_by_name().
Instead of subclassing, it is often easier to use the generated MyAppFrobberSkeleton subclass. To handle incoming method calls, use g_signal_connect() with the ::handle-* signals and instead of overriding the get_property() and set_property() vfuncs from GObject, use g_object_get() and g_object_set() or the generated property getters and setters (the generated class has an internal property bag implementation).
For example:
static gboolean on_handle_hello_world (MyAppFrobber *interface,
GDBusMethodInvocation *invocation,
const gchar *greeting,
gpointer user_data) {
if (g_strcmp0 (greeting, "Boo") != 0)
{
gchar *response;
response = g_strdup_printf ("Word! You said ‘%s’.", greeting);
my_app_complete_hello_world (interface, invocation, response);
g_free (response);
}
else
{
g_dbus_method_invocation_return_error (invocation,
MY_APP_ERROR,
MY_APP_ERROR_NO_WHINING,
"Hey, %s, there will be no whining!",
g_dbus_method_invocation_get_sender (invocation));
}
return TRUE; }
[…]
interface = my_app_frobber_skeleton_new ();
my_app_frobber_set_verbose (interface, TRUE);
g_signal_connect (interface,
"handle-hello-world",
G_CALLBACK (on_handle_hello_world),
some_user_data);
[…]
error = NULL;
if (!g_dbus_interface_skeleton_export (G_DBUS_INTERFACE_SKELETON (interface),
connection,
"/path/of/dbus_object",
&error))
{
/* handle error */
}
To facilitate atomic changesets (multiple properties changing at the same time), GObject::notify signals are queued up when received. The queue is drained in an idle handler (which is called from the thread-default main loop of the thread where the skeleton object was constructed) and will cause emissions of the org.freedesktop.DBus.Properties::PropertiesChanged (documentation <https://dbus.freedesktop.org/doc/dbus-specification.html#standard-interfaces-properties> ) signal with all the properties that have changed. Use g_dbus_interface_skeleton_flush() or g_dbus_object_skeleton_flush() to empty the queue immediately. Use g_object_freeze_notify() and g_object_thaw_notify() for atomic changesets if on a different thread.
C TYPE MAPPING¶
Scalar types (type strings b, y, n, q, i, u, x, t and d), strings (type strings s, ay, o and g) and arrays of strings (type strings as, ao and aay) are mapped to the natural types, e.g. gboolean, gdouble, gint, gchar*, gchar** and so on. Everything else is mapped to the GVariant type.
This automatic mapping can be turned off by using the annotation org.gtk.GDBus.C.ForceGVariant — if used then a GVariant is always exchanged instead of the corresponding native C type. This annotation may be convenient to use when using bytestrings (type string ay) for data that could have embedded nul bytes.
STABILITY GUARANTEES¶
The generated C functions are guaranteed to not change their ABI. That is, if a method, signal or property does not change its signature in the introspection XML, the generated C functions will not change their C ABI either. The ABI of the generated instance and class structures will be preserved as well.
The ABI of the generated GType instances will be preserved only if the org.gtk.GDBus.Since annotation is used judiciously — this is because the VTable for the GInterface relies on function pointers for signal handlers. Specifically, if a D-Bus method, property or signal or is added to a D-Bus interface, then ABI of the generated GInterface type is preserved if, and only if, each added method, property signal is annotated with the org.gtk.GDBus.Since annotation using a greater version number than previous versions.
The generated C code currently happens to be annotated with
gtk-doc <https://gitlab.gnome.org/GNOME/gtk-doc/>
and GObject Introspection <https://gi.readthedocs.io/en/latest/>
comments and annotations. The layout and contents might change in the future
so no guarantees about e.g. SECTION usage etc. are given.
While the generated DocBook for D-Bus interfaces isn’t expected to change, no guarantees are given at this point.
It is important to note that the generated code should not be checked into version control systems, nor it should be included in distributed source archives.
BUGS¶
Please send bug reports to either the distribution bug tracker or the upstream bug tracker <https://gitlab.gnome.org/GNOME/glib/issues/new> .
SEE ALSO¶
<gdbus(1)>