## Client-side GObject bindings

dbus-glib comes with dbus-binding-tool, which can produce somewhat nice client-side wrappers for a D-Bus interface. GDBus does not have code-generation at this point, but GDBusProxy is designed to allow the creating of client-side wrappers by subclassing GDBusProxy.

For an example of a GDBusProxy-derived class that wraps a D-Bus interface in a type-safe way, see Example 18, “GDBusProxy subclass example”. The comparison is as follows:

Table 8. Wrapping the org.freedesktop.Accounts.User D-Bus interface in the AccountUser GObject type

D-Bus concept | GObject concept
--- | ---
AutomaticLogin property | `AccountsUser:automatic-login` GObject property C getter: `accounts_user_get_automatic_login()` Watch changes via the `notify::automatic-login` signal
RealName property | `AccountsUser:real-name` GObject property C getter: `accounts_user_get_real_name()` Watch changes via the `notify::real-name signal`
UserName property | `AccountsUser:user-name` GObject property C getter: `accounts_user_get_user_name()` Watch changes via the `notify::user-name` signal
Changed signal | `AccountsUser::changed` GObject signal Watch via e.g. `g_signal_connect()`
Frobnicate method | Use `accounts_user_frobnicate()` + `accounts_user_frobnicate_finish()` or `accounts_user_frobnicate_sync()` to invoke

Example 18. GDBusProxy subclass example

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    #include <gio/gio.h>

    /* ---------------------------------------------------------------------------------------------------- */
    /* The D-Bus interface definition we want to create a GDBusProxy-derived type for: */
    /* ---------------------------------------------------------------------------------------------------- */

    static const gchar introspection_xml[] =
      "<node>"
      "  <interface name='org.freedesktop.Accounts.User'>"
      "    <method name='Frobnicate'>"
      "      <arg name='flux' type='s' direction='in'/>"
      "      <arg name='baz' type='s' direction='in'/>"
      "      <arg name='result' type='s' direction='out'/>"
      "    </method>"
      "    <signal name='Changed'/>"
      "    <property name='AutomaticLogin' type='b' access='readwrite'/>"
      "    <property name='RealName' type='s' access='read'/>"
      "    <property name='UserName' type='s' access='read'/>"
      "  </interface>"
      "</node>";

    /* ---------------------------------------------------------------------------------------------------- */
    /* Definition of the AccountsUser type */
    /* ---------------------------------------------------------------------------------------------------- */

    #define ACCOUNTS_TYPE_USER         (accounts_user_get_type ())
    #define ACCOUNTS_USER(o)           (G_TYPE_CHECK_INSTANCE_CAST ((o), ACCOUNTS_TYPE_USER, AccountsUser))
    #define ACCOUNTS_USER_CLASS(k)     (G_TYPE_CHECK_CLASS_CAST((k), ACCOUNTS_TYPE_USER, AccountsUserClass))
    #define ACCOUNTS_USER_GET_CLASS(o) (G_TYPE_INSTANCE_GET_CLASS ((o), ACCOUNTS_TYPE_USER, AccountsUserClass))
    #define ACCOUNTS_IS_USER(o)        (G_TYPE_CHECK_INSTANCE_TYPE ((o), ACCOUNTS_TYPE_USER))
    #define ACCOUNTS_IS_USER_CLASS(k)  (G_TYPE_CHECK_CLASS_TYPE ((k), ACCOUNTS_TYPE_USER))

    typedef struct _AccountsUser        AccountsUser;
    typedef struct _AccountsUserClass   AccountsUserClass;
    typedef struct _AccountsUserPrivate AccountsUserPrivate;

    struct _AccountsUser
    {
      /*< private >*/
      GDBusProxy parent_instance;
      AccountsUserPrivate *priv;
    };

    struct _AccountsUserClass
    {
      /*< private >*/
      GDBusProxyClass parent_class;
      void (*changed) (AccountsUser *user);
    };

    GType        accounts_user_get_type            (void) G_GNUC_CONST;

    const gchar *accounts_user_get_user_name       (AccountsUser        *user);
    const gchar *accounts_user_get_real_name       (AccountsUser        *user);
    gboolean     accounts_user_get_automatic_login (AccountsUser        *user);

    void         accounts_user_frobnicate          (AccountsUser        *user,
                                                    const gchar         *flux,
                                                    gint                 baz,
                                                    GCancellable        *cancellable,
                                                    GAsyncReadyCallback  callback,
                                                    gpointer             user_data);
    gchar       *accounts_user_frobnicate_finish   (AccountsUser        *user,
                                                    GAsyncResult        *res,
                                                    GError             **error);
    gchar       *accounts_user_frobnicate_sync     (AccountsUser        *user,
                                                    const gchar         *flux,
                                                    gint                 baz,
                                                    GCancellable        *cancellable,
                                                    GError             **error);

    /* ---------------------------------------------------------------------------------------------------- */
    /* Implementation of the AccountsUser type */
    /* ---------------------------------------------------------------------------------------------------- */

    /* A more efficient approach than parsing XML is to use const static
     * GDBusInterfaceInfo, GDBusMethodInfo, ... structures
     */
    static GDBusInterfaceInfo *
    accounts_user_get_interface_info (void)
    {
      static gsize has_info = 0;
      static GDBusInterfaceInfo *info = NULL;
      if (g_once_init_enter (&has_info))
        {
          GDBusNodeInfo *introspection_data;
          introspection_data = g_dbus_node_info_new_for_xml (introspection_xml, NULL);
          info = introspection_data->interfaces[0];
          g_once_init_leave (&has_info, 1);
        }
      return info;
    }

    enum
    {
      PROP_0,
      PROP_USER_NAME,
      PROP_REAL_NAME,
      PROP_AUTOMATIC_LOGIN,
    };

    enum
    {
      CHANGED_SIGNAL,
      LAST_SIGNAL
    };

    static guint signals[LAST_SIGNAL] = {0};

    G_DEFINE_TYPE (AccountsUser, accounts_user, G_TYPE_DBUS_PROXY);

    static void
    accounts_user_finalize (GObject *object)
    {
      G_GNUC_UNUSED AccountsUser *user = ACCOUNTS_USER (object);

      if (G_OBJECT_CLASS (accounts_user_parent_class)->finalize != NULL)
        G_OBJECT_CLASS (accounts_user_parent_class)->finalize (object);
    }

    static void
    accounts_user_init (AccountsUser *user)
    {
      /* Sets the expected interface */
      g_dbus_proxy_set_interface_info (G_DBUS_PROXY (user), accounts_user_get_interface_info ());
    }

    static void
    accounts_user_get_property (GObject    *object,
                                guint       prop_id,
                                GValue     *value,
                                GParamSpec *pspec)
    {
      AccountsUser *user = ACCOUNTS_USER (object);

      switch (prop_id)
        {
        case PROP_USER_NAME:
          g_value_set_string (value, accounts_user_get_user_name (user));
          break;

        case PROP_REAL_NAME:
          g_value_set_string (value, accounts_user_get_real_name (user));
          break;

        case PROP_AUTOMATIC_LOGIN:
          g_value_set_boolean (value, accounts_user_get_automatic_login (user));
          break;

        default:
          G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
          break;
        }
    }

    const gchar *
    accounts_user_get_user_name (AccountsUser *user)
    {
      GVariant *value;
      const gchar *ret;
      g_return_val_if_fail (ACCOUNTS_IS_USER (user), NULL);
      value = g_dbus_proxy_get_cached_property (G_DBUS_PROXY (user), "UserName");
      ret = g_variant_get_string (value, NULL);
      g_variant_unref (value);
      return ret;
    }

    const gchar *
    accounts_user_get_real_name (AccountsUser *user)
    {
      GVariant *value;
      const gchar *ret;
      g_return_val_if_fail (ACCOUNTS_IS_USER (user), NULL);
      value = g_dbus_proxy_get_cached_property (G_DBUS_PROXY (user), "RealName");
      ret = g_variant_get_string (value, NULL);
      g_variant_unref (value);
      return ret;
    }

    gboolean
    accounts_user_get_automatic_login (AccountsUser *user)
    {
      GVariant *value;
      gboolean ret;
      g_return_val_if_fail (ACCOUNTS_IS_USER (user), FALSE);
      value = g_dbus_proxy_get_cached_property (G_DBUS_PROXY (user), "AutomaticLogin");
      ret = g_variant_get_boolean (value);
      g_variant_unref (value);
      return ret;
    }

    static void
    accounts_user_g_signal (GDBusProxy   *proxy,
                            const gchar  *sender_name,
                            const gchar  *signal_name,
                            GVariant     *parameters)
    {
      AccountsUser *user = ACCOUNTS_USER (proxy);
      if (g_strcmp0 (signal_name, "Changed") == 0)
        g_signal_emit (user, signals[CHANGED_SIGNAL], 0);
    }

    static void
    accounts_user_g_properties_changed (GDBusProxy          *proxy,
                                        GVariant            *changed_properties,
                                        const gchar* const  *invalidated_properties)
    {
      AccountsUser *user = ACCOUNTS_USER (proxy);
      GVariantIter *iter;
      const gchar *key;

      if (changed_properties != NULL)
        {
          g_variant_get (changed_properties, "a{sv}", &iter);
          while (g_variant_iter_next (iter, "{&sv}", &key, NULL))
            {
              if (g_strcmp0 (key, "AutomaticLogin") == 0)
                g_object_notify (G_OBJECT (user), "automatic-login");
              else if (g_strcmp0 (key, "RealName") == 0)
                g_object_notify (G_OBJECT (user), "real-name");
              else if (g_strcmp0 (key, "UserName") == 0)
                g_object_notify (G_OBJECT (user), "user-name");
            }
          g_variant_iter_free (iter);
        }
    }

    static void
    accounts_user_class_init (AccountsUserClass *klass)
    {
      GObjectClass *gobject_class;
      GDBusProxyClass *proxy_class;

      gobject_class = G_OBJECT_CLASS (klass);
      gobject_class->get_property = accounts_user_get_property;
      gobject_class->finalize = accounts_user_finalize;

      proxy_class = G_DBUS_PROXY_CLASS (klass);
      proxy_class->g_signal             = accounts_user_g_signal;
      proxy_class->g_properties_changed = accounts_user_g_properties_changed;

      g_object_class_install_property (gobject_class,
                                       PROP_USER_NAME,
                                       g_param_spec_string ("user-name",
                                                            "User Name",
                                                            "The user name of the user",
                                                            NULL,
                                                            G_PARAM_READABLE |
                                                            G_PARAM_STATIC_STRINGS));

      g_object_class_install_property (gobject_class,
                                       PROP_REAL_NAME,
                                       g_param_spec_string ("real-name",
                                                            "Real Name",
                                                            "The real name of the user",
                                                            NULL,
                                                            G_PARAM_READABLE |
                                                            G_PARAM_STATIC_STRINGS));

      g_object_class_install_property (gobject_class,
                                       PROP_AUTOMATIC_LOGIN,
                                       g_param_spec_boolean ("automatic-login",
                                                             "Automatic Login",
                                                             "Whether the user is automatically logged in",
                                                             FALSE,
                                                             G_PARAM_READABLE |
                                                             G_PARAM_STATIC_STRINGS));

      signals[CHANGED_SIGNAL] = g_signal_new ("changed",
                                              ACCOUNTS_TYPE_USER,
                                              G_SIGNAL_RUN_LAST,
                                              G_STRUCT_OFFSET (AccountsUserClass, changed),
                                              NULL,
                                              NULL,
                                              g_cclosure_marshal_VOID__VOID,
                                              G_TYPE_NONE,
                                              0);
    }

    gchar *
    accounts_user_frobnicate_sync (AccountsUser        *user,
                                   const gchar         *flux,
                                   gint                 baz,
                                   GCancellable        *cancellable,
                                   GError             **error)
    {
      gchar *ret;
      GVariant *value;

      g_return_val_if_fail (ACCOUNTS_IS_USER (user), NULL);

      ret = NULL;

      value = g_dbus_proxy_call_sync (G_DBUS_PROXY (user),
                                      "Frobnicate",
                                      g_variant_new ("(si)",
                                                     flux,
                                                     baz),
                                      G_DBUS_CALL_FLAGS_NONE,
                                      -1,
                                      cancellable,
                                      error);
      if (value != NULL)
        {
          g_variant_get (value, "(s)", &ret);
          g_variant_unref (value);
        }
      return ret;
    }

    void
    accounts_user_frobnicate (AccountsUser        *user,
                              const gchar         *flux,
                              gint                 baz,
                              GCancellable        *cancellable,
                              GAsyncReadyCallback  callback,
                              gpointer             user_data)
    {
      g_return_if_fail (ACCOUNTS_IS_USER (user));
      g_dbus_proxy_call (G_DBUS_PROXY (user),
                         "Frobnicate",
                         g_variant_new ("(si)",
                                        flux,
                                        baz),
                         G_DBUS_CALL_FLAGS_NONE,
                         -1,
                         cancellable,
                         callback,
                         user_data);
    }

    gchar *
    accounts_user_frobnicate_finish (AccountsUser        *user,
                                     GAsyncResult        *res,
                                     GError             **error)
    {
      gchar *ret;
      GVariant *value;

      ret = NULL;
      value = g_dbus_proxy_call_finish (G_DBUS_PROXY (user), res, error);
      if (value != NULL)
        {
          g_variant_get (value, "(s)", &ret);
          g_variant_unref (value);
        }
      return ret;
    }

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

    gint
    main (gint argc, gchar *argv[])
    {
      return 0;
    }