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 */
126 * Returns the reference of the object, or 0 if it is not registered.
129 object_to_ref (AtkObject *accessible)
131 return GPOINTER_TO_INT(g_object_get_data (G_OBJECT (accessible), "dbus-id"));
135 * Converts the Accessible object reference to its D-Bus object path
138 ref_to_path (guint ref)
140 return g_strdup_printf(SPI_ATK_OBJECT_REFERENCE_TEMPLATE, ref);
143 /*---------------------------------------------------------------------------*/
146 * Callback for when a registered AtkObject is destroyed.
148 * Removes the AtkObject from the reference lookup tables, meaning
149 * it is no longer exposed over D-Bus.
152 deregister_accessible (gpointer data, GObject *accessible)
155 g_assert (ATK_IS_OBJECT (accessible));
157 ref = object_to_ref (ATK_OBJECT(accessible));
160 g_hash_table_remove(ref2ptr, GINT_TO_POINTER(ref));
165 * Called to register an AtkObject with AT-SPI and expose it over D-Bus.
168 register_accessible (AtkObject *accessible)
171 g_assert(ATK_IS_OBJECT(accessible));
173 ref = assign_reference();
175 g_hash_table_insert (ref2ptr, GINT_TO_POINTER(ref), accessible);
176 g_object_set_data (G_OBJECT(accessible), "dbus-id", GINT_TO_POINTER(ref));
177 g_object_weak_ref(G_OBJECT(accessible), deregister_accessible, NULL);
180 /*---------------------------------------------------------------------------*/
184 * This function checks that the ref-count of an accessible
187 * There is not currently any remote reference counting
188 * in AT-SPI D-Bus so objects that are remotely owned are not
191 * TODO Add debug wrapper
194 non_owned_accessible (AtkObject *accessible)
196 if ((G_OBJECT (accessible))->ref_count <= 1)
198 g_warning ("AT-SPI: Child referenced that is not owned by its parent");
206 #endif /* SPI_ATK_DEBUG */
208 /*---------------------------------------------------------------------------*/
211 has_manages_descendants (AtkObject *accessible)
214 gboolean result = FALSE;
216 /* This is dangerous, refing the state set
217 * seems to do wierd things to the tree & cause recursion
218 * by modifying the tree alot.
220 state = atk_object_ref_state_set (accessible);
221 if (atk_state_set_contains_state (state, ATK_STATE_MANAGES_DESCENDANTS))
224 g_warning ("AT-SPI: Object with 'Manages descendants' states not currently handled by AT-SPI");
228 g_object_unref (state);
234 * Registers a subtree of accessible objects
235 * rooted at the accessible object provided.
237 * The leaf nodes do not have their children
238 * registered. A node is considered a leaf
239 * if it has the state "manages-descendants"
240 * or if it has already been registered.
243 register_subtree (AtkObject *accessible)
245 AtkObject *current, *tmp;
251 current = g_object_ref (accessible);
252 if (has_manages_descendants (current))
254 g_object_unref (current);
258 stack = g_queue_new ();
260 register_accessible (current);
261 g_queue_push_head (stack, GINT_TO_POINTER (0));
264 * The index held on the stack is the next child node
265 * that needs processing at the corresponding level in the tree.
267 while (!g_queue_is_empty (stack))
269 /* Find the next child node that needs processing */
271 i = GPOINTER_TO_INT(g_queue_peek_head (stack));
274 while (i < atk_object_get_n_accessible_children (current) &&
277 tmp = atk_object_ref_accessible_child (current, i);
280 non_owned_accessible (tmp);
283 if (object_to_ref (tmp))
285 /* If its already registered, just update */
286 spi_emit_cache_update (tmp, atk_adaptor_app_data->bus);
288 else if (has_manages_descendants (tmp))
290 /* If it has manages descendants, just register and update */
291 register_accessible (tmp);
292 spi_emit_cache_update (tmp, atk_adaptor_app_data->bus);
301 g_object_unref (G_OBJECT (tmp));
309 /* Push onto stack */
311 register_accessible (current);
313 g_queue_peek_head_link (stack)->data = GINT_TO_POINTER (i);
314 g_queue_push_head (stack, GINT_TO_POINTER (0));
319 spi_emit_cache_update (current, atk_adaptor_app_data->bus);
321 current = atk_object_get_parent (current);
322 g_object_unref (G_OBJECT (tmp));
323 g_queue_pop_head (stack);
326 g_queue_free (stack);
329 /*---------------------------------------------------------------------------*/
332 * Called when an already registered object is updated in such a
333 * way that client side cache needs to be updated.
336 update_accessible (AtkObject *accessible)
339 g_assert(ATK_IS_OBJECT(accessible));
341 ref = object_to_ref (accessible);
344 spi_emit_cache_update (accessible, atk_adaptor_app_data->bus);
348 /*---------------------------------------------------------------------------*/
351 atk_dbus_foreach_registered(GHFunc func, gpointer data)
353 g_hash_table_foreach(ref2ptr, func, data);
357 * Used to lookup an AtkObject from its D-Bus path.
360 atk_dbus_path_to_object (const char *path)
367 if (strncmp(path, SPI_ATK_OBJECT_PATH_PREFIX, SPI_ATK_PATH_PREFIX_LENGTH) != 0)
370 path += SPI_ATK_PATH_PREFIX_LENGTH; /* Skip over the prefix */
372 if (!g_strcmp0 (SPI_ATK_OBJECT_PATH_DESKTOP, path))
373 return atk_get_root();
379 data = g_hash_table_lookup (ref2ptr, GINT_TO_POINTER(index));
381 return ATK_OBJECT (data);
387 * Used to lookup a D-Bus path from the AtkObject.
390 atk_dbus_object_to_path (AtkObject *accessible)
394 ref = object_to_ref (accessible);
398 return ref_to_path (ref);
402 atk_dbus_desktop_object_path ()
404 return g_strdup (SPI_ATK_OBJECT_PATH_PREFIX SPI_ATK_OBJECT_PATH_DESKTOP);
407 /*---------------------------------------------------------------------------*/
410 * Events are not evaluated for non-registered accessibles.
412 * When a property change is made on a registered accessible
413 * the client side cache should be updated.
415 * When a parent is changed the subtree is de-registered
416 * if the parent is not attached to the root accessible.
419 tree_update_listener (GSignalInvocationHint *signal_hint,
420 guint n_param_values,
421 const GValue *param_values,
424 AtkObject *accessible;
425 AtkPropertyValues *values;
426 const gchar *pname = NULL;
428 g_static_rec_mutex_lock (®istration_mutex);
430 /* Ensure that only registered accessibles
431 * have their signals processed.
433 accessible = g_value_get_object (¶m_values[0]);
434 g_assert (ATK_IS_OBJECT (accessible));
436 if (object_to_ref (accessible))
439 if (recursion_check_and_set ())
440 g_warning ("AT-SPI: Recursive use of registration module");
443 values = (AtkPropertyValues*) g_value_get_pointer (¶m_values[1]);
444 pname = values[0].property_name;
445 if (strcmp (pname, "accessible-name") == 0 ||
446 strcmp (pname, "accessible-description") == 0)
448 update_accessible (accessible);
450 /* Parent value us updated by child-add signal of parent object */
452 recursion_check_unset ();
455 g_static_rec_mutex_unlock (®istration_mutex);
461 * Events are not evaluated for non registered accessibles.
463 * When the children of a registered accessible are changed
464 * the subtree, rooted at the child is registered.
467 tree_update_children_listener (GSignalInvocationHint *signal_hint,
468 guint n_param_values,
469 const GValue *param_values,
472 AtkObject *accessible;
473 const gchar *detail = NULL;
476 g_static_rec_mutex_lock (®istration_mutex);
478 /* Ensure that only registered accessibles
479 * have their signals processed.
481 accessible = g_value_get_object (¶m_values[0]);
482 g_assert (ATK_IS_OBJECT (accessible));
484 if (object_to_ref (accessible))
487 if (recursion_check_and_set ())
488 g_warning ("AT-SPI: Recursive use of registration module");
491 if (signal_hint->detail)
492 detail = g_quark_to_string (signal_hint->detail);
494 if (!strcmp (detail, "add"))
497 int index = g_value_get_uint (param_values + 1);
498 child = g_value_get_pointer (param_values + 2);
500 if (!ATK_IS_OBJECT (child))
502 child = atk_object_ref_accessible_child (accessible, index);
504 non_owned_accessible (child);
507 register_subtree (child);
510 recursion_check_unset ();
513 g_static_rec_mutex_unlock (®istration_mutex);
519 * Initializes required global data. The update and removal lists
520 * and the reference lookup tables.
522 * Initializes all of the required D-Bus interfaces.
525 atk_dbus_initialize (AtkObject *root)
528 ref2ptr = g_hash_table_new(g_direct_hash, g_direct_equal);
531 if (g_thread_supported ())
532 g_message ("AT-SPI: Threads enabled");
535 register_subtree (root);
537 atk_add_global_event_listener (tree_update_listener, "Gtk:AtkObject:property-change");
538 atk_add_global_event_listener (tree_update_children_listener, "Gtk:AtkObject:children-changed");
541 /*END------------------------------------------------------------------------*/