Generating code and docs

Using gdbus-codegen

dbus-glib comes with dbus-binding-tool, which can produce somewhat nice client- and server-side wrappers for a D-Bus interface. With GDBus, gdbus-codegen is used and like its counterpart, it also takes D-Bus Introspection XML as input:

Example 23. Example D-Bus Introspection XML

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<node>
  <!-- org.gtk.GDBus.Example.ObjectManager.Animal:
       @short_description: Example docs generated by gdbus-codegen
       @since: 2.30

       This D-Bus interface is used to describe a simple animal.
    -->
  <interface name="org.gtk.GDBus.Example.ObjectManager.Animal">
    <!-- Mood: The mood of the animal.
         @since: 2.30

         Known values for this property include
         <literal>Happy</literal> and <literal>Sad</literal>. Use the
         org.gtk.GDBus.Example.ObjectManager.Animal.Poke() method to
         change this property.

         This property influences how often the animal jumps up and
         down, see the
         #org.gtk.GDBus.Example.ObjectManager.Animal::Jumped signal
         for more details.
    -->
    <property name="Mood" type="s" access="read"/>

    <!--
        Poke:
        @make_sad: Whether to make the animal sad.
        @make_happy: Whether to make the animal happy.
        @since: 2.30

        Method used to changing the mood of the animal. See also the
        #org.gtk.GDBus.Example.ObjectManager.Animal:Mood property.
      -->
    <method name="Poke">
      <arg direction="in" type="b" name="make_sad"/>
      <arg direction="in" type="b" name="make_happy"/>
    </method>

    <!--
        Jumped:
        @height: Height, in meters, that the animal jumped.
        @since: 2.30

        Emitted when the animal decides to jump.
      -->
    <signal name="Jumped">
      <arg type="d" name="height"/>
    </signal>
  </interface>

  <!-- org.gtk.GDBus.Example.ObjectManager.Cat:
       @short_description: More example docs generated by gdbus-codegen

       This D-Bus interface is used to describe a cat. Right now there
       are no properties, methods or signals associated with this
       interface so it is essentially a <ulink
       url="http://en.wikipedia.org/wiki/Marker_interface_pattern">Marker
       Interface</ulink>.

       Note that D-Bus objects implementing this interface also
       implement the #org.gtk.GDBus.Example.ObjectManager.Animal
       interface.
    -->
  <interface name="org.gtk.GDBus.Example.ObjectManager.Cat">
  </interface>
</node>

If this XML is processed like this

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gdbus-codegen --interface-prefix org.gtk.GDBus.Example.ObjectManager. \
              --generate-c-code generated-code                        \
              --c-namespace Example                       \
              --c-generate-object-manager                 \
              --generate-docbook generated-docs                       \
              gdbus-example-objectmanager.xml

then two files generated-code.h and generated-code.c are generated. Additionally, two XML files generated-docs-org.gtk.GDBus.Example.ObjectManager.Animal and generated-docs-org.gtk.GDBus.Example.ObjectManager.Cat with Docbook XML are generated. For an example of what the docs look like see the Animal D-Bus interface documentation. and the Cat D-Bus interface documentation.

While the contents of generated-code.h and generated-code.c are best described by the gdbus-codegen manual page, brief examples of how this generated code can be used can be found in Example 24, “Server-side application using generated code” and Example 25, “Client-side application using generated code”. Additionally, since the generated code has 100% gtk-doc coverage, see ExampleAnimal, ExampleCat, ExampleObject and ExampleObjectManagerClient pages for documentation.

Example 24. Server-side application using generated code

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#include "gdbus-example-objectmanager-generated.h"

/* ---------------------------------------------------------------------------------------------------- */

static GDBusObjectManagerServer *manager = NULL;

static gboolean
on_animal_poke (ExampleAnimal          *animal,
                GDBusMethodInvocation  *invocation,
                gboolean                make_sad,
                gboolean                make_happy,
                gpointer                user_data)
{
  if ((make_sad && make_happy) || (!make_sad && !make_happy))
    {
      g_dbus_method_invocation_return_dbus_error (invocation,
                                                  "org.gtk.GDBus.Examples.ObjectManager.Error.Failed",
                                                  "Exactly one of make_sad or make_happy must be TRUE");
      goto out;
    }

  if (make_sad)
    {
      if (g_strcmp0 (example_animal_get_mood (animal), "Sad") == 0)
        {
          g_dbus_method_invocation_return_dbus_error (invocation,
                                                      "org.gtk.GDBus.Examples.ObjectManager.Error.SadAnimalIsSad",
                                                      "Sad animal is already sad");
          goto out;
        }

      example_animal_set_mood (animal, "Sad");
      example_animal_complete_poke (animal, invocation);
      goto out;
    }

  if (make_happy)
    {
      if (g_strcmp0 (example_animal_get_mood (animal), "Happy") == 0)
        {
          g_dbus_method_invocation_return_dbus_error (invocation,
                                                      "org.gtk.GDBus.Examples.ObjectManager.Error.HappyAnimalIsHappy",
                                                      "Happy animal is already happy");
          goto out;
        }

      example_animal_set_mood (animal, "Happy");
      example_animal_complete_poke (animal, invocation);
      goto out;
    }

  g_assert_not_reached ();

 out:
  return TRUE; /* to indicate that the method was handled */
}


static void
on_bus_acquired (GDBusConnection *connection,
                 const gchar     *name,
                 gpointer         user_data)
{
  ExampleObjectSkeleton *object;
  guint n;

  g_print ("Acquired a message bus connection\n");

  /* Create a new org.freedesktop.DBus.ObjectManager rooted at /example/Animals */
  manager = g_dbus_object_manager_server_new ("/example/Animals");

  for (n = 0; n < 10; n++)
    {
      gchar *s;
      ExampleAnimal *animal;

      /* Create a new D-Bus object at the path /example/Animals/N where N is 000..009 */
      s = g_strdup_printf ("/example/Animals/%03d", n);
      object = example_object_skeleton_new (s);
      g_free (s);

      /* Make the newly created object export the interface
       * org.gtk.GDBus.Example.ObjectManager.Animal (note
       * that @object takes its own reference to @animal).
       */
      animal = example_animal_skeleton_new ();
      example_animal_set_mood (animal, "Happy");
      example_object_skeleton_set_animal (object, animal);
      g_object_unref (animal);

      /* Cats are odd animals - so some of our objects implement the
       * org.gtk.GDBus.Example.ObjectManager.Cat interface in addition
       * to the .Animal interface
       */
      if (n % 2 == 1)
        {
          ExampleCat *cat;
          cat = example_cat_skeleton_new ();
          example_object_skeleton_set_cat (object, cat);
          g_object_unref (cat);
        }

      /* Handle Poke() D-Bus method invocations on the .Animal interface */
      g_signal_connect (animal,
                        "handle-poke",
                        G_CALLBACK (on_animal_poke),
                        NULL); /* user_data */

      /* Export the object (@manager takes its own reference to @object) */
      g_dbus_object_manager_server_export (manager, G_DBUS_OBJECT_SKELETON (object));
      g_object_unref (object);
    }

  /* Export all objects */
  g_dbus_object_manager_server_set_connection (manager, connection);
}

static void
on_name_acquired (GDBusConnection *connection,
                  const gchar     *name,
                  gpointer         user_data)
{
  g_print ("Acquired the name %s\n", name);
}

static void
on_name_lost (GDBusConnection *connection,
              const gchar     *name,
              gpointer         user_data)
{
  g_print ("Lost the name %s\n", name);
}


gint
main (gint argc, gchar *argv[])
{
  GMainLoop *loop;
  guint id;

  g_type_init ();

  loop = g_main_loop_new (NULL, FALSE);

  id = g_bus_own_name (G_BUS_TYPE_SESSION,
                       "org.gtk.GDBus.Examples.ObjectManager",
                       G_BUS_NAME_OWNER_FLAGS_ALLOW_REPLACEMENT |
                       G_BUS_NAME_OWNER_FLAGS_REPLACE,
                       on_bus_acquired,
                       on_name_acquired,
                       on_name_lost,
                       loop,
                       NULL);

  g_main_loop_run (loop);

  g_bus_unown_name (id);
  g_main_loop_unref (loop);

  return 0;
}

Example 25. Client-side application using generated code

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#include "gdbus-example-objectmanager-generated.h"

/* ---------------------------------------------------------------------------------------------------- */

static void
print_objects (GDBusObjectManager *manager)
{
  GList *objects;
  GList *l;

  g_print ("Object manager at %s\n", g_dbus_object_manager_get_object_path (manager));
  objects = g_dbus_object_manager_get_objects (manager);
  for (l = objects; l != NULL; l = l->next)
    {
      ExampleObject *object = EXAMPLE_OBJECT (l->data);
      GList *interfaces;
      GList *ll;
      g_print (" - Object at %s\n", g_dbus_object_get_object_path (G_DBUS_OBJECT (object)));

      interfaces = g_dbus_object_get_interfaces (G_DBUS_OBJECT (object));
      for (ll = interfaces; ll != NULL; ll = ll->next)
        {
          GDBusInterface *interface = G_DBUS_INTERFACE (ll->data);
          g_print ("   - Interface %s\n", g_dbus_interface_get_info (interface)->name);

          /* Note that @interface is really a GDBusProxy instance - and additionally also
           * an ExampleAnimal or ExampleCat instance - either of these can be used to
           * invoke methods on the remote object. For example, the generated function
           *
           *  void example_animal_call_poke_sync (ExampleAnimal  *proxy,
           *                                      gboolean        make_sad,
           *                                      gboolean        make_happy,
           *                                      GCancellable   *cancellable,
           *                                      GError        **error);
           *
           * can be used to call the Poke() D-Bus method on the .Animal interface.
           * Additionally, the generated function
           *
           *  const gchar *example_animal_get_mood (ExampleAnimal *object);
           *
           * can be used to get the value of the :Mood property.
           */
        }
      g_list_free_full (interfaces, g_object_unref);
    }
  g_list_free_full (objects, g_object_unref);
}

static void
on_object_added (GDBusObjectManager *manager,
                 GDBusObject        *object,
                 gpointer            user_data)
{
  gchar *owner;
  owner = g_dbus_object_manager_client_get_name_owner (G_DBUS_OBJECT_MANAGER_CLIENT (manager));
  g_print ("Added object at %s (owner %s)\n", g_dbus_object_get_object_path (object), owner);
  g_free (owner);
}

static void
on_object_removed (GDBusObjectManager *manager,
                   GDBusObject        *object,
                   gpointer            user_data)
{
  gchar *owner;
  owner = g_dbus_object_manager_client_get_name_owner (G_DBUS_OBJECT_MANAGER_CLIENT (manager));
  g_print ("Removed object at %s (owner %s)\n", g_dbus_object_get_object_path (object), owner);
  g_free (owner);
}

static void
on_notify_name_owner (GObject    *object,
                      GParamSpec *pspec,
                      gpointer    user_data)
{
  GDBusObjectManagerClient *manager = G_DBUS_OBJECT_MANAGER_CLIENT (object);
  gchar *name_owner;

  name_owner = g_dbus_object_manager_client_get_name_owner (manager);
  g_print ("name-owner: %s\n", name_owner);
  g_free (name_owner);
}

static void
on_interface_proxy_properties_changed (GDBusObjectManagerClient *manager,
                                       GDBusObjectProxy         *object_proxy,
                                       GDBusProxy               *interface_proxy,
                                       GVariant                 *changed_properties,
                                       const gchar *const       *invalidated_properties,
                                       gpointer                  user_data)
{
  GVariantIter iter;
  const gchar *key;
  GVariant *value;
  gchar *s;

  g_print ("Properties Changed on %s:\n", g_dbus_object_get_object_path (G_DBUS_OBJECT (object_proxy)));
  g_variant_iter_init (&iter, changed_properties);
  while (g_variant_iter_next (&iter, "{&sv}", &key, &value))
    {
      s = g_variant_print (value, TRUE);
      g_print ("  %s -> %s\n", key, s);
      g_variant_unref (value);
      g_free (s);
    }
}

gint
main (gint argc, gchar *argv[])
{
  GDBusObjectManager *manager;
  GMainLoop *loop;
  GError *error;
  gchar *name_owner;

  manager = NULL;
  loop = NULL;

  g_type_init ();

  loop = g_main_loop_new (NULL, FALSE);

  error = NULL;
  manager = example_object_manager_client_new_for_bus_sync (G_BUS_TYPE_SESSION,
                                                            G_DBUS_OBJECT_MANAGER_CLIENT_FLAGS_NONE,
                                                            "org.gtk.GDBus.Examples.ObjectManager",
                                                            "/example/Animals",
                                                            NULL, /* GCancellable */
                                                            &error);
  if (manager == NULL)
    {
      g_printerr ("Error getting object manager client: %s", error->message);
      g_error_free (error);
      goto out;
    }

  name_owner = g_dbus_object_manager_client_get_name_owner (G_DBUS_OBJECT_MANAGER_CLIENT (manager));
  g_print ("name-owner: %s\n", name_owner);
  g_free (name_owner);

  print_objects (manager);

  g_signal_connect (manager,
                    "notify::name-owner",
                    G_CALLBACK (on_notify_name_owner),
                    NULL);
  g_signal_connect (manager,
                    "object-added",
                    G_CALLBACK (on_object_added),
                    NULL);
  g_signal_connect (manager,
                    "object-removed",
                    G_CALLBACK (on_object_removed),
                    NULL);
  g_signal_connect (manager,
                    "interface-proxy-properties-changed",
                    G_CALLBACK (on_interface_proxy_properties_changed),
                    NULL);

  g_main_loop_run (loop);

 out:
  if (manager != NULL)
    g_object_unref (manager);
  if (loop != NULL)
    g_main_loop_unref (loop);

  return 0;
}