gio/gdbusnamewatching.c

   1 /* GDBus - GLib D-Bus Library
   2  *
   3  * Copyright (C) 2008-2010 Red Hat, Inc.
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2.1 of the License, or (at your option) any later version.
   9  *
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General
  16  * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
  17  *
  18  * Author: David Zeuthen <davidz@redhat.com>
  19  */
  20
  21 #include "config.h"
  22
  23 #include <stdlib.h>
  24 #include <string.h>
  25
  26 #include "gdbusutils.h"
  27 #include "gdbusnamewatching.h"
  28 #include "gdbuserror.h"
  29 #include "gdbusprivate.h"
  30 #include "gdbusconnection.h"
  31
  32 #include "glibintl.h"
  33
  34 /**
  35  * SECTION:gdbusnamewatching
  36  * @title: Watching Bus Names
  37  * @short_description: Simple API for watching bus names
  38  * @include: gio/gio.h
  39  *
  40  * Convenience API for watching bus names.
  41  *
  42  * A simple example for watching a name can be found in
  43  * [gdbus-example-watch-name.c](https://git.gnome.org/browse/glib/tree/gio/tests/gdbus-example-watch-name.c)
  44  */
  45
  46 G_LOCK_DEFINE_STATIC (lock);
  47
  48 /* ---------------------------------------------------------------------------------------------------- */
  49
  50 typedef enum
  51 {
  52   PREVIOUS_CALL_NONE = 0,
  53   PREVIOUS_CALL_APPEARED,
  54   PREVIOUS_CALL_VANISHED,
  55 } PreviousCall;
  56
  57 typedef struct
  58 {
  59   volatile gint             ref_count;
  60   guint                     id;
  61   gchar                    *name;
  62   GBusNameWatcherFlags      flags;
  63   gchar                    *name_owner;
  64   GBusNameAppearedCallback  name_appeared_handler;
  65   GBusNameVanishedCallback  name_vanished_handler;
  66   gpointer                  user_data;
  67   GDestroyNotify            user_data_free_func;
  68   GMainContext             *main_context;
  69
  70   GDBusConnection          *connection;
  71   gulong                    disconnected_signal_handler_id;
  72   guint                     name_owner_changed_subscription_id;
  73
  74   PreviousCall              previous_call;
  75
  76   gboolean                  cancelled;
  77   gboolean                  initialized;
  78 } Client;
  79
  80 /* Must be accessed atomically. */
  81 static volatile guint next_global_id = 1;
  82
  83 /* Must be accessed with @lock held. */
  84 static GHashTable *map_id_to_client = NULL;
  85
  86 static Client *
  87 client_ref (Client *client)
  88 {
  89   g_atomic_int_inc (&client->ref_count);
  90   return client;
  91 }
  92
  93 static void
  94 client_unref (Client *client)
  95 {
  96   if (g_atomic_int_dec_and_test (&client->ref_count))
  97     {
  98       if (client->connection != NULL)
  99         {
 100           if (client->name_owner_changed_subscription_id > 0)
 101             g_dbus_connection_signal_unsubscribe (client->connection, client->name_owner_changed_subscription_id);
 102           if (client->disconnected_signal_handler_id > 0)
 103             g_signal_handler_disconnect (client->connection, client->disconnected_signal_handler_id);
 104           g_object_unref (client->connection);
 105         }
 106       g_free (client->name);
 107       g_free (client->name_owner);
 108       g_main_context_unref (client->main_context);
 109       if (client->user_data_free_func != NULL)
 110         client->user_data_free_func (client->user_data);
 111       g_free (client);
 112     }
 113 }
 114
 115 /* ---------------------------------------------------------------------------------------------------- */
 116
 117 typedef enum
 118 {
 119   CALL_TYPE_NAME_APPEARED,
 120   CALL_TYPE_NAME_VANISHED
 121 } CallType;
 122
 123 typedef struct
 124 {
 125   Client *client;
 126
 127   /* keep this separate because client->connection may
 128    * be set to NULL after scheduling the call
 129    */
 130   GDBusConnection *connection;
 131
 132   /* ditto */
 133   gchar *name_owner;
 134
 135   CallType call_type;
 136 } CallHandlerData;
 137
 138 static void
 139 call_handler_data_free (CallHandlerData *data)
 140 {
 141   if (data->connection != NULL)
 142     g_object_unref (data->connection);
 143   g_free (data->name_owner);
 144   client_unref (data->client);
 145   g_free (data);
 146 }
 147
 148 static void
 149 actually_do_call (Client *client, GDBusConnection *connection, const gchar *name_owner, CallType call_type)
 150 {
 151   /* The client might have been cancelled (g_bus_unwatch_name()) while we were
 152    * sitting in the #GMainContext dispatch queue. */
 153   if (client->cancelled)
 154     return;
 155
 156   switch (call_type)
 157     {
 158     case CALL_TYPE_NAME_APPEARED:
 159       if (client->name_appeared_handler != NULL)
 160         {
 161           client->name_appeared_handler (connection,
 162                                          client->name,
 163                                          name_owner,
 164                                          client->user_data);
 165         }
 166       break;
 167
 168     case CALL_TYPE_NAME_VANISHED:
 169       if (client->name_vanished_handler != NULL)
 170         {
 171           client->name_vanished_handler (connection,
 172                                          client->name,
 173                                          client->user_data);
 174         }
 175       break;
 176
 177     default:
 178       g_assert_not_reached ();
 179       break;
 180     }
 181 }
 182
 183 static gboolean
 184 call_in_idle_cb (gpointer _data)
 185 {
 186   CallHandlerData *data = _data;
 187   actually_do_call (data->client, data->connection, data->name_owner, data->call_type);
 188   return FALSE;
 189 }
 190
 191 static void
 192 schedule_call_in_idle (Client *client, CallType call_type)
 193 {
 194   CallHandlerData *data;
 195   GSource *idle_source;
 196
 197   data = g_new0 (CallHandlerData, 1);
 198   data->client = client_ref (client);
 199   data->connection = client->connection != NULL ? g_object_ref (client->connection) : NULL;
 200   data->name_owner = g_strdup (client->name_owner);
 201   data->call_type = call_type;
 202
 203   idle_source = g_idle_source_new ();
 204   g_source_set_priority (idle_source, G_PRIORITY_HIGH);
 205   g_source_set_callback (idle_source,
 206                          call_in_idle_cb,
 207                          data,
 208                          (GDestroyNotify) call_handler_data_free);
 209   g_source_set_name (idle_source, "[gio, gdbusnamewatching.c] call_in_idle_cb");
 210   g_source_attach (idle_source, client->main_context);
 211   g_source_unref (idle_source);
 212 }
 213
 214 static void
 215 do_call (Client *client, CallType call_type)
 216 {
 217   GMainContext *current_context;
 218
 219   /* only schedule in idle if we're not in the right thread */
 220   current_context = g_main_context_ref_thread_default ();
 221   if (current_context != client->main_context)
 222     schedule_call_in_idle (client, call_type);
 223   else
 224     actually_do_call (client, client->connection, client->name_owner, call_type);
 225   g_main_context_unref (current_context);
 226 }
 227
 228 static void
 229 call_appeared_handler (Client *client)
 230 {
 231   if (client->previous_call != PREVIOUS_CALL_APPEARED)
 232     {
 233       client->previous_call = PREVIOUS_CALL_APPEARED;
 234       if (!client->cancelled && client->name_appeared_handler != NULL)
 235         {
 236           do_call (client, CALL_TYPE_NAME_APPEARED);
 237         }
 238     }
 239 }
 240
 241 static void
 242 call_vanished_handler (Client *client)
 243 {
 244   if (client->previous_call != PREVIOUS_CALL_VANISHED)
 245     {
 246       client->previous_call = PREVIOUS_CALL_VANISHED;
 247       if (!client->cancelled && client->name_vanished_handler != NULL)
 248         {
 249           do_call (client, CALL_TYPE_NAME_VANISHED);
 250         }
 251     }
 252 }
 253
 254 /* ---------------------------------------------------------------------------------------------------- */
 255
 256 /* Return a reference to the #Client for @watcher_id, or %NULL if it’s been
 257  * unwatched. This is safe to call from any thread. */
 258 static Client *
 259 dup_client (guint watcher_id)
 260 {
 261   Client *client;
 262
 263   G_LOCK (lock);
 264
 265   g_assert (watcher_id != 0);
 266   g_assert (map_id_to_client != NULL);
 267
 268   client = g_hash_table_lookup (map_id_to_client, GUINT_TO_POINTER (watcher_id));
 269
 270   if (client != NULL)
 271     client_ref (client);
 272
 273   G_UNLOCK (lock);
 274
 275   return client;
 276 }
 277
 278 /* Could be called from any thread, so it could be called after client_unref()
 279  * has started finalising the #Client. Avoid that by looking up the #Client
 280  * atomically. */
 281 static void
 282 on_connection_disconnected (GDBusConnection *connection,
 283                             gboolean         remote_peer_vanished,
 284                             GError          *error,
 285                             gpointer         user_data)
 286 {
 287   guint watcher_id = GPOINTER_TO_UINT (user_data);
 288   Client *client = NULL;
 289
 290   client = dup_client (watcher_id);
 291   if (client == NULL)
 292     return;
 293
 294   if (client->name_owner_changed_subscription_id > 0)
 295     g_dbus_connection_signal_unsubscribe (client->connection, client->name_owner_changed_subscription_id);
 296   if (client->disconnected_signal_handler_id > 0)
 297     g_signal_handler_disconnect (client->connection, client->disconnected_signal_handler_id);
 298   g_object_unref (client->connection);
 299   client->disconnected_signal_handler_id = 0;
 300   client->name_owner_changed_subscription_id = 0;
 301   client->connection = NULL;
 302
 303   call_vanished_handler (client);
 304
 305   client_unref (client);
 306 }
 307
 308 /* ---------------------------------------------------------------------------------------------------- */
 309
 310 /* Will always be called from the thread which acquired client->main_context. */
 311 static void
 312 on_name_owner_changed (GDBusConnection *connection,
 313                        const gchar      *sender_name,
 314                        const gchar      *object_path,
 315                        const gchar      *interface_name,
 316                        const gchar      *signal_name,
 317                        GVariant         *parameters,
 318                        gpointer          user_data)
 319 {
 320   guint watcher_id = GPOINTER_TO_UINT (user_data);
 321   Client *client = NULL;
 322   const gchar *name;
 323   const gchar *old_owner;
 324   const gchar *new_owner;
 325
 326   client = dup_client (watcher_id);
 327   if (client == NULL)
 328     return;
 329
 330   if (!client->initialized)
 331     goto out;
 332
 333   if (g_strcmp0 (object_path, "/org/freedesktop/DBus") != 0 ||
 334       g_strcmp0 (interface_name, "org.freedesktop.DBus") != 0 ||
 335       g_strcmp0 (sender_name, "org.freedesktop.DBus") != 0)
 336     goto out;
 337
 338   g_variant_get (parameters,
 339                  "(&s&s&s)",
 340                  &name,
 341                  &old_owner,
 342                  &new_owner);
 343
 344   /* we only care about a specific name */
 345   if (g_strcmp0 (name, client->name) != 0)
 346     goto out;
 347
 348   if ((old_owner != NULL && strlen (old_owner) > 0) && client->name_owner != NULL)
 349     {
 350       g_free (client->name_owner);
 351       client->name_owner = NULL;
 352       call_vanished_handler (client);
 353     }
 354
 355   if (new_owner != NULL && strlen (new_owner) > 0)
 356     {
 357       g_warn_if_fail (client->name_owner == NULL);
 358       g_free (client->name_owner);
 359       client->name_owner = g_strdup (new_owner);
 360       call_appeared_handler (client);
 361     }
 362
 363  out:
 364   client_unref (client);
 365 }
 366
 367 /* ---------------------------------------------------------------------------------------------------- */
 368
 369 static void
 370 get_name_owner_cb (GObject      *source_object,
 371                    GAsyncResult *res,
 372                    gpointer      user_data)
 373 {
 374   Client *client = user_data;
 375   GVariant *result;
 376   const char *name_owner;
 377
 378   name_owner = NULL;
 379   result = NULL;
 380
 381   result = g_dbus_connection_call_finish (client->connection,
 382                                           res,
 383                                           NULL);
 384   if (result != NULL)
 385     {
 386       g_variant_get (result, "(&s)", &name_owner);
 387     }
 388
 389   if (name_owner != NULL)
 390     {
 391       g_warn_if_fail (client->name_owner == NULL);
 392       client->name_owner = g_strdup (name_owner);
 393       call_appeared_handler (client);
 394     }
 395   else
 396     {
 397       call_vanished_handler (client);
 398     }
 399
 400   client->initialized = TRUE;
 401
 402   if (result != NULL)
 403     g_variant_unref (result);
 404   client_unref (client);
 405 }
 406
 407 /* ---------------------------------------------------------------------------------------------------- */
 408
 409 static void
 410 invoke_get_name_owner (Client *client)
 411 {
 412   g_dbus_connection_call (client->connection,
 413                           "org.freedesktop.DBus",  /* bus name */
 414                           "/org/freedesktop/DBus", /* object path */
 415                           "org.freedesktop.DBus",  /* interface name */
 416                           "GetNameOwner",          /* method name */
 417                           g_variant_new ("(s)", client->name),
 418                           G_VARIANT_TYPE ("(s)"),
 419                           G_DBUS_CALL_FLAGS_NONE,
 420                           -1,
 421                           NULL,
 422                           (GAsyncReadyCallback) get_name_owner_cb,
 423                           client_ref (client));
 424 }
 425
 426 /* ---------------------------------------------------------------------------------------------------- */
 427
 428 static void
 429 start_service_by_name_cb (GObject      *source_object,
 430                           GAsyncResult *res,
 431                           gpointer      user_data)
 432 {
 433   Client *client = user_data;
 434   GVariant *result;
 435
 436   result = NULL;
 437
 438   result = g_dbus_connection_call_finish (client->connection,
 439                                           res,
 440                                           NULL);
 441   if (result != NULL)
 442     {
 443       guint32 start_service_result;
 444       g_variant_get (result, "(u)", &start_service_result);
 445
 446       if (start_service_result == 1) /* DBUS_START_REPLY_SUCCESS */
 447         {
 448           invoke_get_name_owner (client);
 449         }
 450       else if (start_service_result == 2) /* DBUS_START_REPLY_ALREADY_RUNNING */
 451         {
 452           invoke_get_name_owner (client);
 453         }
 454       else
 455         {
 456           g_warning ("Unexpected reply %d from StartServiceByName() method", start_service_result);
 457           call_vanished_handler (client);
 458           client->initialized = TRUE;
 459         }
 460     }
 461   else
 462     {
 463       /* Errors are not unexpected; the bus will reply e.g.
 464        *
 465        *   org.freedesktop.DBus.Error.ServiceUnknown: The name org.gnome.Epiphany2
 466        *   was not provided by any .service files
 467        *
 468        * This doesn't mean that the name doesn't have an owner, just
 469        * that it's not provided by a .service file. So proceed to
 470        * invoke GetNameOwner().
 471        */
 472       invoke_get_name_owner (client);
 473     }
 474
 475   if (result != NULL)
 476     g_variant_unref (result);
 477   client_unref (client);
 478 }
 479
 480 /* ---------------------------------------------------------------------------------------------------- */
 481
 482 static void
 483 has_connection (Client *client)
 484 {
 485   /* listen for disconnection */
 486   client->disconnected_signal_handler_id = g_signal_connect (client->connection,
 487                                                              "closed",
 488                                                              G_CALLBACK (on_connection_disconnected),
 489                                                              GUINT_TO_POINTER (client->id));
 490
 491   /* start listening to NameOwnerChanged messages immediately */
 492   client->name_owner_changed_subscription_id = g_dbus_connection_signal_subscribe (client->connection,
 493                                                                                    "org.freedesktop.DBus",  /* name */
 494                                                                                    "org.freedesktop.DBus",  /* if */
 495                                                                                    "NameOwnerChanged",      /* signal */
 496                                                                                    "/org/freedesktop/DBus", /* path */
 497                                                                                    client->name,
 498                                                                                    G_DBUS_SIGNAL_FLAGS_NONE,
 499                                                                                    on_name_owner_changed,
 500                                                                                    GUINT_TO_POINTER (client->id),
 501                                                                                    NULL);
 502
 503   if (client->flags & G_BUS_NAME_WATCHER_FLAGS_AUTO_START)
 504     {
 505       g_dbus_connection_call (client->connection,
 506                               "org.freedesktop.DBus",  /* bus name */
 507                               "/org/freedesktop/DBus", /* object path */
 508                               "org.freedesktop.DBus",  /* interface name */
 509                               "StartServiceByName",    /* method name */
 510                               g_variant_new ("(su)", client->name, 0),
 511                               G_VARIANT_TYPE ("(u)"),
 512                               G_DBUS_CALL_FLAGS_NONE,
 513                               -1,
 514                               NULL,
 515                               (GAsyncReadyCallback) start_service_by_name_cb,
 516                               client_ref (client));
 517     }
 518   else
 519     {
 520       /* check owner */
 521       invoke_get_name_owner (client);
 522     }
 523 }
 524
 525
 526 static void
 527 connection_get_cb (GObject      *source_object,
 528                    GAsyncResult *res,
 529                    gpointer      user_data)
 530 {
 531   Client *client = user_data;
 532
 533   client->connection = g_bus_get_finish (res, NULL);
 534   if (client->connection == NULL)
 535     {
 536       call_vanished_handler (client);
 537       goto out;
 538     }
 539
 540   has_connection (client);
 541
 542  out:
 543   client_unref (client);
 544 }
 545
 546 /* ---------------------------------------------------------------------------------------------------- */
 547
 548 /**
 549  * g_bus_watch_name:
 550  * @bus_type: The type of bus to watch a name on.
 551  * @name: The name (well-known or unique) to watch.
 552  * @flags: Flags from the #GBusNameWatcherFlags enumeration.
 553  * @name_appeared_handler: (nullable): Handler to invoke when @name is known to exist or %NULL.
 554  * @name_vanished_handler: (nullable): Handler to invoke when @name is known to not exist or %NULL.
 555  * @user_data: User data to pass to handlers.
 556  * @user_data_free_func: (nullable): Function for freeing @user_data or %NULL.
 557  *
 558  * Starts watching @name on the bus specified by @bus_type and calls
 559  * @name_appeared_handler and @name_vanished_handler when the name is
 560  * known to have an owner respectively known to lose its
 561  * owner. Callbacks will be invoked in the
 562  * [thread-default main context][g-main-context-push-thread-default]
 563  * of the thread you are calling this function from.
 564  *
 565  * You are guaranteed that one of the handlers will be invoked after
 566  * calling this function. When you are done watching the name, just
 567  * call g_bus_unwatch_name() with the watcher id this function
 568  * returns.
 569  *
 570  * If the name vanishes or appears (for example the application owning
 571  * the name could restart), the handlers are also invoked. If the
 572  * #GDBusConnection that is used for watching the name disconnects, then
 573  * @name_vanished_handler is invoked since it is no longer
 574  * possible to access the name.
 575  *
 576  * Another guarantee is that invocations of @name_appeared_handler
 577  * and @name_vanished_handler are guaranteed to alternate; that
 578  * is, if @name_appeared_handler is invoked then you are
 579  * guaranteed that the next time one of the handlers is invoked, it
 580  * will be @name_vanished_handler. The reverse is also true.
 581  *
 582  * This behavior makes it very simple to write applications that want
 583  * to take action when a certain [name exists][gdbus-watching-names].
 584  * Basically, the application should create object proxies in
 585  * @name_appeared_handler and destroy them again (if any) in
 586  * @name_vanished_handler.
 587  *
 588  * Returns: An identifier (never 0) that can be used with
 589  * g_bus_unwatch_name() to stop watching the name.
 590  *
 591  * Since: 2.26
 592  */
 593 guint
 594 g_bus_watch_name (GBusType                  bus_type,
 595                   const gchar              *name,
 596                   GBusNameWatcherFlags      flags,
 597                   GBusNameAppearedCallback  name_appeared_handler,
 598                   GBusNameVanishedCallback  name_vanished_handler,
 599                   gpointer                  user_data,
 600                   GDestroyNotify            user_data_free_func)
 601 {
 602   Client *client;
 603
 604   g_return_val_if_fail (g_dbus_is_name (name), 0);
 605
 606   G_LOCK (lock);
 607
 608   client = g_new0 (Client, 1);
 609   client->ref_count = 1;
 610   client->id = (guint) g_atomic_int_add (&next_global_id, 1); /* TODO: uh oh, handle overflow */
 611   client->name = g_strdup (name);
 612   client->flags = flags;
 613   client->name_appeared_handler = name_appeared_handler;
 614   client->name_vanished_handler = name_vanished_handler;
 615   client->user_data = user_data;
 616   client->user_data_free_func = user_data_free_func;
 617   client->main_context = g_main_context_ref_thread_default ();
 618
 619   if (map_id_to_client == NULL)
 620     {
 621       map_id_to_client = g_hash_table_new (g_direct_hash, g_direct_equal);
 622     }
 623   g_hash_table_insert (map_id_to_client,
 624                        GUINT_TO_POINTER (client->id),
 625                        client);
 626
 627   g_bus_get (bus_type,
 628              NULL,
 629              connection_get_cb,
 630              client_ref (client));
 631
 632   G_UNLOCK (lock);
 633
 634   return client->id;
 635 }
 636
 637 /**
 638  * g_bus_watch_name_on_connection:
 639  * @connection: A #GDBusConnection.
 640  * @name: The name (well-known or unique) to watch.
 641  * @flags: Flags from the #GBusNameWatcherFlags enumeration.
 642  * @name_appeared_handler: (nullable): Handler to invoke when @name is known to exist or %NULL.
 643  * @name_vanished_handler: (nullable): Handler to invoke when @name is known to not exist or %NULL.
 644  * @user_data: User data to pass to handlers.
 645  * @user_data_free_func: (nullable): Function for freeing @user_data or %NULL.
 646  *
 647  * Like g_bus_watch_name() but takes a #GDBusConnection instead of a
 648  * #GBusType.
 649  *
 650  * Returns: An identifier (never 0) that can be used with
 651  * g_bus_unwatch_name() to stop watching the name.
 652  *
 653  * Since: 2.26
 654  */
 655 guint g_bus_watch_name_on_connection (GDBusConnection          *connection,
 656                                       const gchar              *name,
 657                                       GBusNameWatcherFlags      flags,
 658                                       GBusNameAppearedCallback  name_appeared_handler,
 659                                       GBusNameVanishedCallback  name_vanished_handler,
 660                                       gpointer                  user_data,
 661                                       GDestroyNotify            user_data_free_func)
 662 {
 663   Client *client;
 664
 665   g_return_val_if_fail (G_IS_DBUS_CONNECTION (connection), 0);
 666   g_return_val_if_fail (g_dbus_is_name (name), 0);
 667
 668   G_LOCK (lock);
 669
 670   client = g_new0 (Client, 1);
 671   client->ref_count = 1;
 672   client->id = (guint) g_atomic_int_add (&next_global_id, 1); /* TODO: uh oh, handle overflow */
 673   client->name = g_strdup (name);
 674   client->flags = flags;
 675   client->name_appeared_handler = name_appeared_handler;
 676   client->name_vanished_handler = name_vanished_handler;
 677   client->user_data = user_data;
 678   client->user_data_free_func = user_data_free_func;
 679   client->main_context = g_main_context_ref_thread_default ();
 680
 681   if (map_id_to_client == NULL)
 682     map_id_to_client = g_hash_table_new (g_direct_hash, g_direct_equal);
 683
 684   g_hash_table_insert (map_id_to_client,
 685                        GUINT_TO_POINTER (client->id),
 686                        client);
 687
 688   client->connection = g_object_ref (connection);
 689   G_UNLOCK (lock);
 690
 691   has_connection (client);
 692
 693   return client->id;
 694 }
 695
 696 typedef struct {
 697   GClosure *name_appeared_closure;
 698   GClosure *name_vanished_closure;
 699 } WatchNameData;
 700
 701 static WatchNameData *
 702 watch_name_data_new (GClosure *name_appeared_closure,
 703                      GClosure *name_vanished_closure)
 704 {
 705   WatchNameData *data;
 706
 707   data = g_new0 (WatchNameData, 1);
 708
 709   if (name_appeared_closure != NULL)
 710     {
 711       data->name_appeared_closure = g_closure_ref (name_appeared_closure);
 712       g_closure_sink (name_appeared_closure);
 713       if (G_CLOSURE_NEEDS_MARSHAL (name_appeared_closure))
 714         g_closure_set_marshal (name_appeared_closure, g_cclosure_marshal_generic);
 715     }
 716
 717   if (name_vanished_closure != NULL)
 718     {
 719       data->name_vanished_closure = g_closure_ref (name_vanished_closure);
 720       g_closure_sink (name_vanished_closure);
 721       if (G_CLOSURE_NEEDS_MARSHAL (name_vanished_closure))
 722         g_closure_set_marshal (name_vanished_closure, g_cclosure_marshal_generic);
 723     }
 724
 725   return data;
 726 }
 727
 728 static void
 729 watch_with_closures_on_name_appeared (GDBusConnection *connection,
 730                                       const gchar     *name,
 731                                       const gchar     *name_owner,
 732                                       gpointer         user_data)
 733 {
 734   WatchNameData *data = user_data;
 735   GValue params[3] = { G_VALUE_INIT, G_VALUE_INIT, G_VALUE_INIT };
 736
 737   g_value_init (&params[0], G_TYPE_DBUS_CONNECTION);
 738   g_value_set_object (&params[0], connection);
 739
 740   g_value_init (&params[1], G_TYPE_STRING);
 741   g_value_set_string (&params[1], name);
 742
 743   g_value_init (&params[2], G_TYPE_STRING);
 744   g_value_set_string (&params[2], name_owner);
 745
 746   g_closure_invoke (data->name_appeared_closure, NULL, 3, params, NULL);
 747
 748   g_value_unset (params + 0);
 749   g_value_unset (params + 1);
 750   g_value_unset (params + 2);
 751 }
 752
 753 static void
 754 watch_with_closures_on_name_vanished (GDBusConnection *connection,
 755                                       const gchar     *name,
 756                                       gpointer         user_data)
 757 {
 758   WatchNameData *data = user_data;
 759   GValue params[2] = { G_VALUE_INIT, G_VALUE_INIT };
 760
 761   g_value_init (&params[0], G_TYPE_DBUS_CONNECTION);
 762   g_value_set_object (&params[0], connection);
 763
 764   g_value_init (&params[1], G_TYPE_STRING);
 765   g_value_set_string (&params[1], name);
 766
 767   g_closure_invoke (data->name_vanished_closure, NULL, 2, params, NULL);
 768
 769   g_value_unset (params + 0);
 770   g_value_unset (params + 1);
 771 }
 772
 773 static void
 774 bus_watch_name_free_func (gpointer user_data)
 775 {
 776   WatchNameData *data = user_data;
 777
 778   if (data->name_appeared_closure != NULL)
 779     g_closure_unref (data->name_appeared_closure);
 780
 781   if (data->name_vanished_closure != NULL)
 782     g_closure_unref (data->name_vanished_closure);
 783
 784   g_free (data);
 785 }
 786
 787 /**
 788  * g_bus_watch_name_with_closures: (rename-to g_bus_watch_name)
 789  * @bus_type: The type of bus to watch a name on.
 790  * @name: The name (well-known or unique) to watch.
 791  * @flags: Flags from the #GBusNameWatcherFlags enumeration.
 792  * @name_appeared_closure: (nullable): #GClosure to invoke when @name is known
 793  * to exist or %NULL.
 794  * @name_vanished_closure: (nullable): #GClosure to invoke when @name is known
 795  * to not exist or %NULL.
 796  *
 797  * Version of g_bus_watch_name() using closures instead of callbacks for
 798  * easier binding in other languages.
 799  *
 800  * Returns: An identifier (never 0) that can be used with
 801  * g_bus_unwatch_name() to stop watching the name.
 802  *
 803  * Since: 2.26
 804  */
 805 guint
 806 g_bus_watch_name_with_closures (GBusType                 bus_type,
 807                                 const gchar             *name,
 808                                 GBusNameWatcherFlags     flags,
 809                                 GClosure                *name_appeared_closure,
 810                                 GClosure                *name_vanished_closure)
 811 {
 812   return g_bus_watch_name (bus_type,
 813           name,
 814           flags,
 815           name_appeared_closure != NULL ? watch_with_closures_on_name_appeared : NULL,
 816           name_vanished_closure != NULL ? watch_with_closures_on_name_vanished : NULL,
 817           watch_name_data_new (name_appeared_closure, name_vanished_closure),
 818           bus_watch_name_free_func);
 819 }
 820
 821 /**
 822  * g_bus_watch_name_on_connection_with_closures: (rename-to g_bus_watch_name_on_connection)
 823  * @connection: A #GDBusConnection.
 824  * @name: The name (well-known or unique) to watch.
 825  * @flags: Flags from the #GBusNameWatcherFlags enumeration.
 826  * @name_appeared_closure: (nullable): #GClosure to invoke when @name is known
 827  * to exist or %NULL.
 828  * @name_vanished_closure: (nullable): #GClosure to invoke when @name is known
 829  * to not exist or %NULL.
 830  *
 831  * Version of g_bus_watch_name_on_connection() using closures instead of callbacks for
 832  * easier binding in other languages.
 833  *
 834  * Returns: An identifier (never 0) that can be used with
 835  * g_bus_unwatch_name() to stop watching the name.
 836  *
 837  * Since: 2.26
 838  */
 839 guint g_bus_watch_name_on_connection_with_closures (
 840                                       GDBusConnection          *connection,
 841                                       const gchar              *name,
 842                                       GBusNameWatcherFlags      flags,
 843                                       GClosure                 *name_appeared_closure,
 844                                       GClosure                 *name_vanished_closure)
 845 {
 846   return g_bus_watch_name_on_connection (connection,
 847           name,
 848           flags,
 849           name_appeared_closure != NULL ? watch_with_closures_on_name_appeared : NULL,
 850           name_vanished_closure != NULL ? watch_with_closures_on_name_vanished : NULL,
 851           watch_name_data_new (name_appeared_closure, name_vanished_closure),
 852           bus_watch_name_free_func);
 853 }
 854
 855 /**
 856  * g_bus_unwatch_name:
 857  * @watcher_id: An identifier obtained from g_bus_watch_name()
 858  *
 859  * Stops watching a name.
 860  *
 861  * Note that there may still be D-Bus traffic to process (relating to watching
 862  * and unwatching the name) in the current thread-default #GMainContext after
 863  * this function has returned. You should continue to iterate the #GMainContext
 864  * until the #GDestroyNotify function passed to g_bus_watch_name() is called, in
 865  * order to avoid memory leaks through callbacks queued on the #GMainContext
 866  * after it’s stopped being iterated.
 867  *
 868  * Since: 2.26
 869  */
 870 void
 871 g_bus_unwatch_name (guint watcher_id)
 872 {
 873   Client *client;
 874
 875   g_return_if_fail (watcher_id > 0);
 876
 877   client = NULL;
 878
 879   G_LOCK (lock);
 880   if (watcher_id == 0 ||
 881       map_id_to_client == NULL ||
 882       (client = g_hash_table_lookup (map_id_to_client, GUINT_TO_POINTER (watcher_id))) == NULL)
 883     {
 884       g_warning ("Invalid id %d passed to g_bus_unwatch_name()", watcher_id);
 885       goto out;
 886     }
 887
 888   client->cancelled = TRUE;
 889   g_warn_if_fail (g_hash_table_remove (map_id_to_client, GUINT_TO_POINTER (watcher_id)));
 890
 891  out:
 892   G_UNLOCK (lock);
 893
 894   /* do callback without holding lock */
 895   if (client != NULL)
 896     {
 897       client_unref (client);
 898     }
 899 }