gio/gdbusconnection.h

   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 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, write to the
  17  * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  18  * Boston, MA 02111-1307, USA.
  19  *
  20  * Author: David Zeuthen <davidz@redhat.com>
  21  */
  22
  23 #if !defined (__GIO_GIO_H_INSIDE__) && !defined (GIO_COMPILATION)
  24 #error "Only <gio/gio.h> can be included directly."
  25 #endif
  26
  27 #ifndef __G_DBUS_CONNECTION_H__
  28 #define __G_DBUS_CONNECTION_H__
  29
  30 #include <gio/giotypes.h>
  31
  32 G_BEGIN_DECLS
  33
  34 #define G_TYPE_DBUS_CONNECTION         (g_dbus_connection_get_type ())
  35 #define G_DBUS_CONNECTION(o)           (G_TYPE_CHECK_INSTANCE_CAST ((o), G_TYPE_DBUS_CONNECTION, GDBusConnection))
  36 #define G_IS_DBUS_CONNECTION(o)        (G_TYPE_CHECK_INSTANCE_TYPE ((o), G_TYPE_DBUS_CONNECTION))
  37
  38 GType            g_dbus_connection_get_type                   (void) G_GNUC_CONST;
  39
  40 /* ---------------------------------------------------------------------------------------------------- */
  41
  42 void              g_bus_get                    (GBusType             bus_type,
  43                                                 GCancellable        *cancellable,
  44                                                 GAsyncReadyCallback  callback,
  45                                                 gpointer             user_data);
  46 GDBusConnection  *g_bus_get_finish             (GAsyncResult        *res,
  47                                                 GError             **error);
  48 GDBusConnection  *g_bus_get_sync               (GBusType            bus_type,
  49                                                 GCancellable       *cancellable,
  50                                                 GError            **error);
  51
  52 /* ---------------------------------------------------------------------------------------------------- */
  53
  54 void             g_dbus_connection_new                        (GIOStream              *stream,
  55                                                                const gchar            *guid,
  56                                                                GDBusConnectionFlags    flags,
  57                                                                GDBusAuthObserver      *observer,
  58                                                                GCancellable           *cancellable,
  59                                                                GAsyncReadyCallback     callback,
  60                                                                gpointer                user_data);
  61 GDBusConnection *g_dbus_connection_new_finish                 (GAsyncResult           *res,
  62                                                                GError                **error);
  63 GDBusConnection *g_dbus_connection_new_sync                   (GIOStream              *stream,
  64                                                                const gchar            *guid,
  65                                                                GDBusConnectionFlags    flags,
  66                                                                GDBusAuthObserver      *observer,
  67                                                                GCancellable           *cancellable,
  68                                                                GError                **error);
  69
  70 void             g_dbus_connection_new_for_address            (const gchar            *address,
  71                                                                GDBusConnectionFlags    flags,
  72                                                                GDBusAuthObserver      *observer,
  73                                                                GCancellable           *cancellable,
  74                                                                GAsyncReadyCallback     callback,
  75                                                                gpointer                user_data);
  76 GDBusConnection *g_dbus_connection_new_for_address_finish     (GAsyncResult           *res,
  77                                                                GError                **error);
  78 GDBusConnection *g_dbus_connection_new_for_address_sync       (const gchar            *address,
  79                                                                GDBusConnectionFlags    flags,
  80                                                                GDBusAuthObserver      *observer,
  81                                                                GCancellable           *cancellable,
  82                                                                GError                **error);
  83
  84 /* ---------------------------------------------------------------------------------------------------- */
  85
  86 void             g_dbus_connection_start_message_processing   (GDBusConnection    *connection);
  87 gboolean         g_dbus_connection_is_closed                  (GDBusConnection    *connection);
  88 GIOStream       *g_dbus_connection_get_stream                 (GDBusConnection    *connection);
  89 const gchar     *g_dbus_connection_get_guid                   (GDBusConnection    *connection);
  90 const gchar     *g_dbus_connection_get_unique_name            (GDBusConnection    *connection);
  91 GCredentials    *g_dbus_connection_get_peer_credentials       (GDBusConnection    *connection);
  92 gboolean         g_dbus_connection_get_exit_on_close          (GDBusConnection    *connection);
  93 void             g_dbus_connection_set_exit_on_close          (GDBusConnection    *connection,
  94                                                                gboolean            exit_on_close);
  95 GDBusCapabilityFlags  g_dbus_connection_get_capabilities      (GDBusConnection    *connection);
  96
  97 /* ---------------------------------------------------------------------------------------------------- */
  98
  99 void             g_dbus_connection_close                          (GDBusConnection     *connection,
 100                                                                    GCancellable        *cancellable,
 101                                                                    GAsyncReadyCallback  callback,
 102                                                                    gpointer             user_data);
 103 gboolean         g_dbus_connection_close_finish                   (GDBusConnection     *connection,
 104                                                                    GAsyncResult        *res,
 105                                                                    GError             **error);
 106 gboolean         g_dbus_connection_close_sync                     (GDBusConnection     *connection,
 107                                                                    GCancellable        *cancellable,
 108                                                                    GError             **error);
 109
 110 /* ---------------------------------------------------------------------------------------------------- */
 111
 112 void             g_dbus_connection_flush                          (GDBusConnection     *connection,
 113                                                                    GCancellable        *cancellable,
 114                                                                    GAsyncReadyCallback  callback,
 115                                                                    gpointer             user_data);
 116 gboolean         g_dbus_connection_flush_finish                   (GDBusConnection     *connection,
 117                                                                    GAsyncResult        *res,
 118                                                                    GError             **error);
 119 gboolean         g_dbus_connection_flush_sync                     (GDBusConnection     *connection,
 120                                                                    GCancellable        *cancellable,
 121                                                                    GError             **error);
 122
 123 /* ---------------------------------------------------------------------------------------------------- */
 124
 125 gboolean         g_dbus_connection_send_message                   (GDBusConnection     *connection,
 126                                                                    GDBusMessage        *message,
 127                                                                    GDBusSendMessageFlags flags,
 128                                                                    volatile guint32    *out_serial,
 129                                                                    GError             **error);
 130 void             g_dbus_connection_send_message_with_reply        (GDBusConnection     *connection,
 131                                                                    GDBusMessage        *message,
 132                                                                    GDBusSendMessageFlags flags,
 133                                                                    gint                 timeout_msec,
 134                                                                    volatile guint32    *out_serial,
 135                                                                    GCancellable        *cancellable,
 136                                                                    GAsyncReadyCallback  callback,
 137                                                                    gpointer             user_data);
 138 GDBusMessage    *g_dbus_connection_send_message_with_reply_finish (GDBusConnection     *connection,
 139                                                                    GAsyncResult        *res,
 140                                                                    GError             **error);
 141 GDBusMessage    *g_dbus_connection_send_message_with_reply_sync   (GDBusConnection     *connection,
 142                                                                    GDBusMessage        *message,
 143                                                                    GDBusSendMessageFlags flags,
 144                                                                    gint                 timeout_msec,
 145                                                                    volatile guint32    *out_serial,
 146                                                                    GCancellable        *cancellable,
 147                                                                    GError             **error);
 148
 149 /* ---------------------------------------------------------------------------------------------------- */
 150
 151 gboolean  g_dbus_connection_emit_signal                       (GDBusConnection    *connection,
 152                                                                const gchar        *destination_bus_name,
 153                                                                const gchar        *object_path,
 154                                                                const gchar        *interface_name,
 155                                                                const gchar        *signal_name,
 156                                                                GVariant           *parameters,
 157                                                                GError            **error);
 158 void      g_dbus_connection_call                              (GDBusConnection    *connection,
 159                                                                const gchar        *bus_name,
 160                                                                const gchar        *object_path,
 161                                                                const gchar        *interface_name,
 162                                                                const gchar        *method_name,
 163                                                                GVariant           *parameters,
 164                                                                const GVariantType *reply_type,
 165                                                                GDBusCallFlags      flags,
 166                                                                gint                timeout_msec,
 167                                                                GCancellable       *cancellable,
 168                                                                GAsyncReadyCallback callback,
 169                                                                gpointer            user_data);
 170 GVariant *g_dbus_connection_call_finish                       (GDBusConnection    *connection,
 171                                                                GAsyncResult       *res,
 172                                                                GError            **error);
 173 GVariant *g_dbus_connection_call_sync                         (GDBusConnection    *connection,
 174                                                                const gchar        *bus_name,
 175                                                                const gchar        *object_path,
 176                                                                const gchar        *interface_name,
 177                                                                const gchar        *method_name,
 178                                                                GVariant           *parameters,
 179                                                                const GVariantType *reply_type,
 180                                                                GDBusCallFlags      flags,
 181                                                                gint                timeout_msec,
 182                                                                GCancellable       *cancellable,
 183                                                                GError            **error);
 184 void      g_dbus_connection_call_with_unix_fd_list            (GDBusConnection    *connection,
 185                                                                const gchar        *bus_name,
 186                                                                const gchar        *object_path,
 187                                                                const gchar        *interface_name,
 188                                                                const gchar        *method_name,
 189                                                                GVariant           *parameters,
 190                                                                const GVariantType *reply_type,
 191                                                                GDBusCallFlags      flags,
 192                                                                gint                timeout_msec,
 193                                                                GUnixFDList        *fd_list,
 194                                                                GCancellable       *cancellable,
 195                                                                GAsyncReadyCallback callback,
 196                                                                gpointer            user_data);
 197 GVariant *g_dbus_connection_call_with_unix_fd_list_finish     (GDBusConnection    *connection,
 198                                                                GUnixFDList       **out_fd_list,
 199                                                                GAsyncResult       *res,
 200                                                                GError            **error);
 201 GVariant *g_dbus_connection_call_with_unix_fd_list_sync       (GDBusConnection    *connection,
 202                                                                const gchar        *bus_name,
 203                                                                const gchar        *object_path,
 204                                                                const gchar        *interface_name,
 205                                                                const gchar        *method_name,
 206                                                                GVariant           *parameters,
 207                                                                const GVariantType *reply_type,
 208                                                                GDBusCallFlags      flags,
 209                                                                gint                timeout_msec,
 210                                                                GUnixFDList        *fd_list,
 211                                                                GUnixFDList       **out_fd_list,
 212                                                                GCancellable       *cancellable,
 213                                                                GError            **error);
 214
 215 /* ---------------------------------------------------------------------------------------------------- */
 216
 217
 218 /**
 219  * GDBusInterfaceMethodCallFunc:
 220  * @connection: A #GDBusConnection.
 221  * @sender: The unique bus name of the remote caller.
 222  * @object_path: The object path that the method was invoked on.
 223  * @interface_name: The D-Bus interface name the method was invoked on.
 224  * @method_name: The name of the method that was invoked.
 225  * @parameters: A #GVariant tuple with parameters.
 226  * @invocation: A #GDBusMethodInvocation object that can be used to return a value or error.
 227  * @user_data: The @user_data #gpointer passed to g_dbus_connection_register_object().
 228  *
 229  * The type of the @method_call function in #GDBusInterfaceVTable.
 230  *
 231  * Since: 2.26
 232  */
 233 typedef void (*GDBusInterfaceMethodCallFunc) (GDBusConnection       *connection,
 234                                               const gchar           *sender,
 235                                               const gchar           *object_path,
 236                                               const gchar           *interface_name,
 237                                               const gchar           *method_name,
 238                                               GVariant              *parameters,
 239                                               GDBusMethodInvocation *invocation,
 240                                               gpointer               user_data);
 241
 242 /**
 243  * GDBusInterfaceGetPropertyFunc:
 244  * @connection: A #GDBusConnection.
 245  * @sender: The unique bus name of the remote caller.
 246  * @object_path: The object path that the method was invoked on.
 247  * @interface_name: The D-Bus interface name for the property.
 248  * @property_name: The name of the property to get the value of.
 249  * @error: Return location for error.
 250  * @user_data: The @user_data #gpointer passed to g_dbus_connection_register_object().
 251  *
 252  * The type of the @get_property function in #GDBusInterfaceVTable.
 253  *
 254  * Returns: A #GVariant with the value for @property_name or %NULL if
 255  *     @error is set. If the returned #GVariant is floating, it is
 256  *     consumed - otherwise its reference count is decreased by one.
 257  *
 258  * Since: 2.26
 259  */
 260 typedef GVariant *(*GDBusInterfaceGetPropertyFunc) (GDBusConnection       *connection,
 261                                                     const gchar           *sender,
 262                                                     const gchar           *object_path,
 263                                                     const gchar           *interface_name,
 264                                                     const gchar           *property_name,
 265                                                     GError               **error,
 266                                                     gpointer               user_data);
 267
 268 /**
 269  * GDBusInterfaceSetPropertyFunc:
 270  * @connection: A #GDBusConnection.
 271  * @sender: The unique bus name of the remote caller.
 272  * @object_path: The object path that the method was invoked on.
 273  * @interface_name: The D-Bus interface name for the property.
 274  * @property_name: The name of the property to get the value of.
 275  * @value: The value to set the property to.
 276  * @error: Return location for error.
 277  * @user_data: The @user_data #gpointer passed to g_dbus_connection_register_object().
 278  *
 279  * The type of the @set_property function in #GDBusInterfaceVTable.
 280  *
 281  * Returns: %TRUE if the property was set to @value, %FALSE if @error is set.
 282  *
 283  * Since: 2.26
 284  */
 285 typedef gboolean  (*GDBusInterfaceSetPropertyFunc) (GDBusConnection       *connection,
 286                                                     const gchar           *sender,
 287                                                     const gchar           *object_path,
 288                                                     const gchar           *interface_name,
 289                                                     const gchar           *property_name,
 290                                                     GVariant              *value,
 291                                                     GError               **error,
 292                                                     gpointer               user_data);
 293
 294 /**
 295  * GDBusInterfaceVTable:
 296  * @method_call: Function for handling incoming method calls.
 297  * @get_property: Function for getting a property.
 298  * @set_property: Function for setting a property.
 299  *
 300  * Virtual table for handling properties and method calls for a D-Bus
 301  * interface.
 302  *
 303  * If you want to handle getting/setting D-Bus properties asynchronously, simply
 304  * register an object with the <literal>org.freedesktop.DBus.Properties</literal>
 305  * D-Bus interface using g_dbus_connection_register_object().
 306  *
 307  * Since: 2.26
 308  */
 309 struct _GDBusInterfaceVTable
 310 {
 311   GDBusInterfaceMethodCallFunc  method_call;
 312   GDBusInterfaceGetPropertyFunc get_property;
 313   GDBusInterfaceSetPropertyFunc set_property;
 314
 315   /*< private >*/
 316   /* Padding for future expansion - also remember to update
 317    * gdbusconnection.c:_g_dbus_interface_vtable_copy() when
 318    * changing this.
 319    */
 320   gpointer padding[8];
 321 };
 322
 323 guint            g_dbus_connection_register_object            (GDBusConnection            *connection,
 324                                                                const gchar                *object_path,
 325                                                                GDBusInterfaceInfo         *interface_info,
 326                                                                const GDBusInterfaceVTable *vtable,
 327                                                                gpointer                    user_data,
 328                                                                GDestroyNotify              user_data_free_func,
 329                                                                GError                    **error);
 330 gboolean         g_dbus_connection_unregister_object          (GDBusConnection            *connection,
 331                                                                guint                       registration_id);
 332
 333 /* ---------------------------------------------------------------------------------------------------- */
 334
 335 /**
 336  * GDBusSubtreeEnumerateFunc:
 337  * @connection: A #GDBusConnection.
 338  * @sender: The unique bus name of the remote caller.
 339  * @object_path: The object path that was registered with g_dbus_connection_register_subtree().
 340  * @user_data: The @user_data #gpointer passed to g_dbus_connection_register_subtree().
 341  *
 342  * The type of the @enumerate function in #GDBusSubtreeVTable.
 343  *
 344  * This function is called when generating introspection data and also
 345  * when preparing to dispatch incoming messages in the event that the
 346  * %G_DBUS_SUBTREE_FLAGS_DISPATCH_TO_UNENUMERATED_NODES flag is not
 347  * specified (ie: to verify that the object path is valid).
 348  *
 349  * Hierarchies are not supported; the items that you return should not
 350  * contain the '/' character.
 351  *
 352  * The return value will be freed with g_strfreev().
 353  *
 354  * Returns: A newly allocated array of strings for node names that are children of @object_path.
 355  *
 356  * Since: 2.26
 357  */
 358 typedef gchar** (*GDBusSubtreeEnumerateFunc) (GDBusConnection       *connection,
 359                                               const gchar           *sender,
 360                                               const gchar           *object_path,
 361                                               gpointer               user_data);
 362
 363 /**
 364  * GDBusSubtreeIntrospectFunc:
 365  * @connection: A #GDBusConnection.
 366  * @sender: The unique bus name of the remote caller.
 367  * @object_path: The object path that was registered with g_dbus_connection_register_subtree().
 368  * @node: A node that is a child of @object_path (relative to @object_path) or %NULL for the root of the subtree.
 369  * @user_data: The @user_data #gpointer passed to g_dbus_connection_register_subtree().
 370  *
 371  * The type of the @introspect function in #GDBusSubtreeVTable.
 372  *
 373  * Subtrees are flat.  @node, if non-%NULL, is always exactly one
 374  * segment of the object path (ie: it never contains a slash).
 375  *
 376  * This function should return %NULL to indicate that there is no object
 377  * at this node.
 378  *
 379  * If this function returns non-%NULL, the return value is expected to
 380  * be a %NULL-terminated array of pointers to #GDBusInterfaceInfo
 381  * structures describing the interfaces implemented by @node.  This
 382  * array will have g_dbus_interface_info_unref() called on each item
 383  * before being freed with g_free().
 384  *
 385  * The difference between returning %NULL and an array containing zero
 386  * items is that the standard DBus interfaces will returned to the
 387  * remote introspector in the empty array case, but not in the %NULL
 388  * case.
 389  *
 390  * Returns: A %NULL-terminated array of pointers to #GDBusInterfaceInfo, or %NULL.
 391  *
 392  * Since: 2.26
 393  */
 394 typedef GDBusInterfaceInfo ** (*GDBusSubtreeIntrospectFunc) (GDBusConnection       *connection,
 395                                                              const gchar           *sender,
 396                                                              const gchar           *object_path,
 397                                                              const gchar           *node,
 398                                                              gpointer               user_data);
 399
 400 /**
 401  * GDBusSubtreeDispatchFunc:
 402  * @connection: A #GDBusConnection.
 403  * @sender: The unique bus name of the remote caller.
 404  * @object_path: The object path that was registered with g_dbus_connection_register_subtree().
 405  * @interface_name: The D-Bus interface name that the method call or property access is for.
 406  * @node: A node that is a child of @object_path (relative to @object_path) or %NULL for the root of the subtree.
 407  * @out_user_data: Return location for user data to pass to functions in the returned #GDBusInterfaceVTable (never %NULL).
 408  * @user_data: The @user_data #gpointer passed to g_dbus_connection_register_subtree().
 409  *
 410  * The type of the @dispatch function in #GDBusSubtreeVTable.
 411  *
 412  * Subtrees are flat.  @node, if non-%NULL, is always exactly one
 413  * segment of the object path (ie: it never contains a slash).
 414  *
 415  * Returns: A #GDBusInterfaceVTable or %NULL if you don't want to handle the methods.
 416  *
 417  * Since: 2.26
 418  */
 419 typedef const GDBusInterfaceVTable * (*GDBusSubtreeDispatchFunc) (GDBusConnection             *connection,
 420                                                                   const gchar                 *sender,
 421                                                                   const gchar                 *object_path,
 422                                                                   const gchar                 *interface_name,
 423                                                                   const gchar                 *node,
 424                                                                   gpointer                    *out_user_data,
 425                                                                   gpointer                     user_data);
 426
 427 /**
 428  * GDBusSubtreeVTable:
 429  * @enumerate: Function for enumerating child nodes.
 430  * @introspect: Function for introspecting a child node.
 431  * @dispatch: Function for dispatching a remote call on a child node.
 432  *
 433  * Virtual table for handling subtrees registered with g_dbus_connection_register_subtree().
 434  *
 435  * Since: 2.26
 436  */
 437 struct _GDBusSubtreeVTable
 438 {
 439   GDBusSubtreeEnumerateFunc  enumerate;
 440   GDBusSubtreeIntrospectFunc introspect;
 441   GDBusSubtreeDispatchFunc   dispatch;
 442
 443   /*< private >*/
 444   /* Padding for future expansion - also remember to update
 445    * gdbusconnection.c:_g_dbus_subtree_vtable_copy() when
 446    * changing this.
 447    */
 448   gpointer padding[8];
 449 };
 450
 451 guint            g_dbus_connection_register_subtree           (GDBusConnection            *connection,
 452                                                                const gchar                *object_path,
 453                                                                const GDBusSubtreeVTable   *vtable,
 454                                                                GDBusSubtreeFlags           flags,
 455                                                                gpointer                    user_data,
 456                                                                GDestroyNotify              user_data_free_func,
 457                                                                GError                    **error);
 458 gboolean         g_dbus_connection_unregister_subtree         (GDBusConnection            *connection,
 459                                                                guint                       registration_id);
 460
 461 /* ---------------------------------------------------------------------------------------------------- */
 462
 463 /**
 464  * GDBusSignalCallback:
 465  * @connection: A #GDBusConnection.
 466  * @sender_name: The unique bus name of the sender of the signal.
 467  * @object_path: The object path that the signal was emitted on.
 468  * @interface_name: The name of the interface.
 469  * @signal_name: The name of the signal.
 470  * @parameters: A #GVariant tuple with parameters for the signal.
 471  * @user_data: User data passed when subscribing to the signal.
 472  *
 473  * Signature for callback function used in g_dbus_connection_signal_subscribe().
 474  *
 475  * Since: 2.26
 476  */
 477 typedef void (*GDBusSignalCallback) (GDBusConnection  *connection,
 478                                      const gchar      *sender_name,
 479                                      const gchar      *object_path,
 480                                      const gchar      *interface_name,
 481                                      const gchar      *signal_name,
 482                                      GVariant         *parameters,
 483                                      gpointer          user_data);
 484
 485 guint            g_dbus_connection_signal_subscribe           (GDBusConnection     *connection,
 486                                                                const gchar         *sender,
 487                                                                const gchar         *interface_name,
 488                                                                const gchar         *member,
 489                                                                const gchar         *object_path,
 490                                                                const gchar         *arg0,
 491                                                                GDBusSignalFlags     flags,
 492                                                                GDBusSignalCallback  callback,
 493                                                                gpointer             user_data,
 494                                                                GDestroyNotify       user_data_free_func);
 495 void             g_dbus_connection_signal_unsubscribe         (GDBusConnection     *connection,
 496                                                                guint                subscription_id);
 497
 498 /* ---------------------------------------------------------------------------------------------------- */
 499
 500 /**
 501  * GDBusMessageFilterFunction:
 502  * @connection: (transfer none): A #GDBusConnection.
 503  * @message: (transfer full): A locked #GDBusMessage that the filter function takes ownership of.
 504  * @incoming: %TRUE if it is a message received from the other peer, %FALSE if it is
 505  * a message to be sent to the other peer.
 506  * @user_data: User data passed when adding the filter.
 507  *
 508  * Signature for function used in g_dbus_connection_add_filter().
 509  *
 510  * A filter function is passed a #GDBusMessage and expected to return
 511  * a #GDBusMessage too. Passive filter functions that don't modify the
 512  * message can simply return the @message object:
 513  * |[
 514  * static GDBusMessage *
 515  * passive_filter (GDBusConnection *connection
 516  *                 GDBusMessage    *message,
 517  *                 gboolean         incoming,
 518  *                 gpointer         user_data)
 519  * {
 520  *   /<!-- -->* inspect @message *<!-- -->/
 521  *   return message;
 522  * }
 523  * ]|
 524  * Filter functions that wants to drop a message can simply return %NULL:
 525  * |[
 526  * static GDBusMessage *
 527  * drop_filter (GDBusConnection *connection
 528  *              GDBusMessage    *message,
 529  *              gboolean         incoming,
 530  *              gpointer         user_data)
 531  * {
 532  *   if (should_drop_message)
 533  *     {
 534  *       g_object_unref (message);
 535  *       message = NULL;
 536  *     }
 537  *   return message;
 538  * }
 539  * ]|
 540  * Finally, a filter function may modify a message by copying it:
 541  * |[
 542  * static GDBusMessage *
 543  * modifying_filter (GDBusConnection *connection
 544  *                   GDBusMessage    *message,
 545  *                   gboolean         incoming,
 546  *                   gpointer         user_data)
 547  * {
 548  *   GDBusMessage *copy;
 549  *   GError *error;
 550  *
 551  *   error = NULL;
 552  *   copy = g_dbus_message_copy (message, &error);
 553  *   /<!-- -->* handle @error being is set *<!-- -->/
 554  *   g_object_unref (message);
 555  *
 556  *   /<!-- -->* modify @copy *<!-- -->/
 557  *
 558  *   return copy;
 559  * }
 560  * ]|
 561  * If the returned #GDBusMessage is different from @message and cannot
 562  * be sent on @connection (it could use features, such as file
 563  * descriptors, not compatible with @connection), then a warning is
 564  * logged to <emphasis>standard error</emphasis>. Applications can
 565  * check this ahead of time using g_dbus_message_to_blob() passing a
 566  * #GDBusCapabilityFlags value obtained from @connection.
 567  *
 568  * Returns: (transfer full) (allow-none): A #GDBusMessage that will be freed with
 569  * g_object_unref() or %NULL to drop the message. Passive filter
 570  * functions can simply return the passed @message object.
 571  *
 572  * Since: 2.26
 573  */
 574 typedef GDBusMessage *(*GDBusMessageFilterFunction) (GDBusConnection *connection,
 575                                                      GDBusMessage    *message,
 576                                                      gboolean         incoming,
 577                                                      gpointer         user_data);
 578
 579 guint g_dbus_connection_add_filter (GDBusConnection            *connection,
 580                                     GDBusMessageFilterFunction  filter_function,
 581                                     gpointer                    user_data,
 582                                     GDestroyNotify              user_data_free_func);
 583
 584 void  g_dbus_connection_remove_filter (GDBusConnection    *connection,
 585                                        guint               filter_id);
 586
 587 /* ---------------------------------------------------------------------------------------------------- */
 588
 589
 590 G_END_DECLS
 591
 592 #endif /* __G_DBUS_CONNECTION_H__ */