2 * AT-SPI - Assistive Technology Service Provider Interface
3 * (Gnome Accessibility Project; http://developer.gnome.org/projects/gap)
5 * Copyright 2008 Novell, Inc.
6 * Copyright 2008, 2009 Codethink Ltd.
8 * This library is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Library General Public
10 * License as published by the Free Software Foundation; either
11 * version 2 of the License, or (at your option) any later version.
13 * This library is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Library General Public License for more details.
18 * You should have received a copy of the GNU Library General Public
19 * License along with this library; if not, write to the
20 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
21 * Boston, MA 02111-1307, USA.
29 #include "accessible-register.h"
32 * This module is responsible for keeping track of all the AtkObjects in
33 * the application, so that they can be accessed remotely and placed in
34 * a client side cache.
36 * To access an AtkObject remotely we need to provide a D-Bus object
37 * path for it. The D-Bus object paths used have a standard prefix
38 * (SPI_ATK_OBJECT_PATH_PREFIX). Appended to this prefix is a string
39 * representation of an integer reference. So to access an AtkObject
40 * remotely we keep a Hashtable that maps the given reference to
41 * the AtkObject pointer. An object in this hash table is said to be 'registered'.
43 * The architecture of AT-SPI dbus is such that AtkObjects are not
44 * remotely reference counted. This means that we need to keep track of
45 * object destruction. When an object is destroyed it must be 'deregistered'
46 * To do this lookup we keep a dbus-id attribute on each AtkObject.
48 * In addition to accessing the objects remotely we must be able to update
49 * the client side cache. This is done using the 'update' signal of the
50 * org.freedesktop.atspi.Tree interface. The update signal should send out
51 * all of the cacheable data for an Accessible object.
58 * This code seems very brittle.
59 * I would prefer changes to be made to
60 * gail and the ATK interface so that all Accessible
61 * objects are registered with an exporting module.
63 * This is the same system as Qt has with the QAccessibleBridge
64 * and QAccessibleBridgePlugin. It entails some rather
65 * large structural changes to ATK though:
67 * Removing infinite spaces (Child access no longer references child).
68 * Removing lazy creation of accessible objects.
71 #define SPI_ATK_OBJECT_PATH_PREFIX "/org/freedesktop/atspi/accessible"
72 #define SPI_ATK_OBJECT_PATH_DESKTOP "/root"
74 #define SPI_ATK_PATH_PREFIX_LENGTH 33
75 #define SPI_ATK_OBJECT_REFERENCE_TEMPLATE SPI_ATK_OBJECT_PATH_PREFIX "/%d"
78 static GHashTable *ref2ptr = NULL; /* Used for converting a D-Bus path (Reference) to the object pointer */
80 static guint counter = 1;
82 static GStaticRecMutex registration_mutex = G_STATIC_REC_MUTEX_INIT;
84 /*---------------------------------------------------------------------------*/
86 static GStaticMutex recursion_check_guard = G_STATIC_MUTEX_INIT;
87 static gboolean recursion_check = FALSE;
90 recursion_check_and_set ()
93 g_static_mutex_lock (&recursion_check_guard);
94 ret = recursion_check;
95 recursion_check = TRUE;
96 g_static_mutex_unlock (&recursion_check_guard);
101 recursion_check_unset ()
103 g_static_mutex_lock (&recursion_check_guard);
104 recursion_check = FALSE;
105 g_static_mutex_unlock (&recursion_check_guard);
108 /*---------------------------------------------------------------------------*/
111 * Each AtkObject must be asssigned a D-Bus path (Reference)
113 * This function provides an integer reference for a new
117 assign_reference(void)
120 /* Reference of 0 not allowed as used as direct key in hash table */
127 * Returns the reference of the object, or 0 if it is not registered.
130 object_to_ref (AtkObject *accessible)
132 return GPOINTER_TO_INT(g_object_get_data (G_OBJECT (accessible), "dbus-id"));
136 * Converts the Accessible object reference to its D-Bus object path
139 ref_to_path (guint ref)
141 return g_strdup_printf(SPI_ATK_OBJECT_REFERENCE_TEMPLATE, ref);
144 /*---------------------------------------------------------------------------*/
147 * Callback for when a registered AtkObject is destroyed.
149 * Removes the AtkObject from the reference lookup tables, meaning
150 * it is no longer exposed over D-Bus.
153 deregister_accessible (gpointer data, GObject *accessible)
156 g_assert (ATK_IS_OBJECT (accessible));
158 ref = object_to_ref (ATK_OBJECT(accessible));
161 g_hash_table_remove(ref2ptr, GINT_TO_POINTER(ref));
166 * Called to register an AtkObject with AT-SPI and expose it over D-Bus.
169 register_accessible (AtkObject *accessible)
172 g_assert(ATK_IS_OBJECT(accessible));
174 ref = assign_reference();
176 g_hash_table_insert (ref2ptr, GINT_TO_POINTER(ref), accessible);
177 g_object_set_data (G_OBJECT(accessible), "dbus-id", GINT_TO_POINTER(ref));
178 g_object_weak_ref(G_OBJECT(accessible), deregister_accessible, NULL);
181 /*---------------------------------------------------------------------------*/
185 * This function checks that the ref-count of an accessible
188 * There is not currently any remote reference counting
189 * in AT-SPI D-Bus so objects that are remotely owned are not
192 * TODO Add debug wrapper
195 non_owned_accessible (AtkObject *accessible)
197 if ((G_OBJECT (accessible))->ref_count <= 1)
199 g_warning ("AT-SPI: Child referenced that is not owned by its parent");
207 #endif /* SPI_ATK_DEBUG */
209 /*---------------------------------------------------------------------------*/
212 has_manages_descendants (AtkObject *accessible)
215 gboolean result = FALSE;
217 /* This is dangerous, refing the state set
218 * seems to do wierd things to the tree & cause recursion
219 * by modifying the tree alot.
221 state = atk_object_ref_state_set (accessible);
222 if (atk_state_set_contains_state (state, ATK_STATE_MANAGES_DESCENDANTS))
225 g_warning ("AT-SPI: Object with 'Manages descendants' states not currently handled by AT-SPI");
229 g_object_unref (state);
235 * Registers a subtree of accessible objects
236 * rooted at the accessible object provided.
238 * The leaf nodes do not have their children
239 * registered. A node is considered a leaf
240 * if it has the state "manages-descendants"
241 * or if it has already been registered.
244 register_subtree (AtkObject *accessible)
246 AtkObject *current, *tmp;
252 current = g_object_ref (accessible);
253 if (has_manages_descendants (current))
255 g_object_unref (current);
259 stack = g_queue_new ();
261 register_accessible (current);
262 g_queue_push_head (stack, GINT_TO_POINTER (0));
265 * The index held on the stack is the next child node
266 * that needs processing at the corresponding level in the tree.
268 while (!g_queue_is_empty (stack))
270 /* Find the next child node that needs processing */
272 i = GPOINTER_TO_INT(g_queue_peek_head (stack));
275 while (i < atk_object_get_n_accessible_children (current) &&
278 tmp = atk_object_ref_accessible_child (current, i);
281 non_owned_accessible (tmp);
284 if (object_to_ref (tmp))
286 /* If its already registered, just update */
287 spi_emit_cache_update (tmp, atk_adaptor_app_data->bus);
289 else if (has_manages_descendants (tmp))
291 /* If it has manages descendants, just register and update */
292 register_accessible (tmp);
293 spi_emit_cache_update (tmp, atk_adaptor_app_data->bus);
302 g_object_unref (G_OBJECT (tmp));
310 /* Push onto stack */
312 register_accessible (current);
314 g_queue_peek_head_link (stack)->data = GINT_TO_POINTER (i);
315 g_queue_push_head (stack, GINT_TO_POINTER (0));
320 spi_emit_cache_update (current, atk_adaptor_app_data->bus);
322 current = atk_object_get_parent (current);
323 g_object_unref (G_OBJECT (tmp));
324 g_queue_pop_head (stack);
327 g_queue_free (stack);
330 /*---------------------------------------------------------------------------*/
333 * Called when an already registered object is updated in such a
334 * way that client side cache needs to be updated.
337 update_accessible (AtkObject *accessible)
340 g_assert(ATK_IS_OBJECT(accessible));
342 ref = object_to_ref (accessible);
345 spi_emit_cache_update (accessible, atk_adaptor_app_data->bus);
349 /*---------------------------------------------------------------------------*/
352 atk_dbus_foreach_registered(GHFunc func, gpointer data)
354 g_hash_table_foreach(ref2ptr, func, data);
358 * Used to lookup an AtkObject from its D-Bus path.
361 atk_dbus_path_to_object (const char *path)
368 if (strncmp(path, SPI_ATK_OBJECT_PATH_PREFIX, SPI_ATK_PATH_PREFIX_LENGTH) != 0)
371 path += SPI_ATK_PATH_PREFIX_LENGTH; /* Skip over the prefix */
373 if (!g_strcmp0 (SPI_ATK_OBJECT_PATH_DESKTOP, path))
374 return atk_get_root();
380 data = g_hash_table_lookup (ref2ptr, GINT_TO_POINTER(index));
382 return ATK_OBJECT (data);
388 * Used to lookup a D-Bus path from the AtkObject.
391 atk_dbus_object_to_path (AtkObject *accessible)
395 ref = object_to_ref (accessible);
399 return ref_to_path (ref);
403 atk_dbus_desktop_object_path ()
405 return g_strdup (SPI_ATK_OBJECT_PATH_PREFIX SPI_ATK_OBJECT_PATH_DESKTOP);
408 /*---------------------------------------------------------------------------*/
411 * Events are not evaluated for non-registered accessibles.
413 * When a property change is made on a registered accessible
414 * the client side cache should be updated.
416 * When a parent is changed the subtree is de-registered
417 * if the parent is not attached to the root accessible.
420 tree_update_listener (GSignalInvocationHint *signal_hint,
421 guint n_param_values,
422 const GValue *param_values,
425 AtkObject *accessible;
426 AtkPropertyValues *values;
427 const gchar *pname = NULL;
429 g_static_rec_mutex_lock (®istration_mutex);
431 /* Ensure that only registered accessibles
432 * have their signals processed.
434 accessible = g_value_get_object (¶m_values[0]);
435 g_assert (ATK_IS_OBJECT (accessible));
437 if (object_to_ref (accessible))
440 if (recursion_check_and_set ())
441 g_warning ("AT-SPI: Recursive use of registration module");
444 values = (AtkPropertyValues*) g_value_get_pointer (¶m_values[1]);
445 pname = values[0].property_name;
446 if (strcmp (pname, "accessible-name") == 0 ||
447 strcmp (pname, "accessible-description") == 0)
449 update_accessible (accessible);
451 /* Parent value us updated by child-add signal of parent object */
453 recursion_check_unset ();
456 g_static_rec_mutex_unlock (®istration_mutex);
462 * Events are not evaluated for non registered accessibles.
464 * When the children of a registered accessible are changed
465 * the subtree, rooted at the child is registered.
468 tree_update_children_listener (GSignalInvocationHint *signal_hint,
469 guint n_param_values,
470 const GValue *param_values,
473 AtkObject *accessible;
474 const gchar *detail = NULL;
477 g_static_rec_mutex_lock (®istration_mutex);
479 /* Ensure that only registered accessibles
480 * have their signals processed.
482 accessible = g_value_get_object (¶m_values[0]);
483 g_assert (ATK_IS_OBJECT (accessible));
485 if (object_to_ref (accessible))
488 if (recursion_check_and_set ())
489 g_warning ("AT-SPI: Recursive use of registration module");
492 if (signal_hint->detail)
493 detail = g_quark_to_string (signal_hint->detail);
495 if (!strcmp (detail, "add"))
498 int index = g_value_get_uint (param_values + 1);
499 child = g_value_get_pointer (param_values + 2);
501 if (!ATK_IS_OBJECT (child))
503 child = atk_object_ref_accessible_child (accessible, index);
505 non_owned_accessible (child);
508 register_subtree (child);
511 recursion_check_unset ();
514 g_static_rec_mutex_unlock (®istration_mutex);
520 * Initializes required global data. The update and removal lists
521 * and the reference lookup tables.
523 * Initializes all of the required D-Bus interfaces.
526 atk_dbus_initialize (AtkObject *root)
529 ref2ptr = g_hash_table_new(g_direct_hash, g_direct_equal);
532 if (g_thread_supported ())
533 g_message ("AT-SPI: Threads enabled");
536 register_subtree (root);
538 atk_add_global_event_listener (tree_update_listener, "Gtk:AtkObject:property-change");
539 atk_add_global_event_listener (tree_update_children_listener, "Gtk:AtkObject:children-changed");
542 /*END------------------------------------------------------------------------*/