2 * Copyright © 2009, 2010 Codethink Limited
3 * Copyright © 2010 Red Hat, Inc.
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 licence, or (at your option) any later version.
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.
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
18 * Authors: Ryan Lortie <desrt@desrt.ca>
19 * Matthias Clasen <mclasen@redhat.com>
24 #include "gsettingsbackendinternal.h"
25 #include "gsimplepermission.h"
26 #include "giomodule-priv.h"
34 typedef struct _GSettingsBackendClosure GSettingsBackendClosure;
35 typedef struct _GSettingsBackendWatch GSettingsBackendWatch;
37 struct _GSettingsBackendPrivate
39 GSettingsBackendWatch *watches;
43 G_DEFINE_ABSTRACT_TYPE_WITH_PRIVATE (GSettingsBackend, g_settings_backend, G_TYPE_OBJECT)
45 /* For g_settings_backend_sync_default(), we only want to actually do
46 * the sync if the backend already exists. This avoids us creating an
47 * entire GSettingsBackend in order to call a do-nothing sync()
48 * operation on it. This variable lets us avoid that.
50 static gboolean g_settings_has_backend;
53 * SECTION:gsettingsbackend
54 * @title: GSettingsBackend
55 * @short_description: Interface for settings backend implementations
56 * @include: gio/gsettingsbackend.h
57 * @see_also: #GSettings, #GIOExtensionPoint
59 * The #GSettingsBackend interface defines a generic interface for
60 * non-strictly-typed data that is stored in a hierarchy. To implement
61 * an alternative storage backend for #GSettings, you need to implement
62 * the #GSettingsBackend interface and then make it implement the
63 * extension point #G_SETTINGS_BACKEND_EXTENSION_POINT_NAME.
65 * The interface defines methods for reading and writing values, a
66 * method for determining if writing of certain values will fail
67 * (lockdown) and a change notification mechanism.
69 * The semantics of the interface are very precisely defined and
70 * implementations must carefully adhere to the expectations of
71 * callers that are documented on each of the interface methods.
73 * Some of the GSettingsBackend functions accept or return a #GTree.
74 * These trees always have strings as keys and #GVariant as values.
75 * g_settings_backend_create_tree() is a convenience function to create
78 * The GSettingsBackend API is exported to allow third-party
79 * implementations, but does not carry the same stability guarantees
80 * as the public GIO API. For this reason, you have to define the
81 * C preprocessor symbol %G_SETTINGS_ENABLE_BACKEND before including
82 * `gio/gsettingsbackend.h`.
86 is_key (const gchar *key)
91 g_return_val_if_fail (key != NULL, FALSE);
92 g_return_val_if_fail (key[0] == '/', FALSE);
94 for (i = 1; key[i]; i++)
95 g_return_val_if_fail (key[i] != '/' || key[i + 1] != '/', FALSE);
99 g_return_val_if_fail (key[length - 1] != '/', FALSE);
105 is_path (const gchar *path)
110 g_return_val_if_fail (path != NULL, FALSE);
111 g_return_val_if_fail (path[0] == '/', FALSE);
113 for (i = 1; path[i]; i++)
114 g_return_val_if_fail (path[i] != '/' || path[i + 1] != '/', FALSE);
118 g_return_val_if_fail (path[length - 1] == '/', FALSE);
123 struct _GSettingsBackendWatch
126 const GSettingsListenerVTable *vtable;
127 GMainContext *context;
128 GSettingsBackendWatch *next;
131 struct _GSettingsBackendClosure
133 void (*function) (GObject *target,
134 GSettingsBackend *backend,
139 GSettingsBackend *backend;
143 GBoxedFreeFunc data1_free;
148 g_settings_backend_watch_weak_notify (gpointer data,
149 GObject *where_the_object_was)
151 GSettingsBackend *backend = data;
152 GSettingsBackendWatch **ptr;
154 /* search and remove */
155 g_mutex_lock (&backend->priv->lock);
156 for (ptr = &backend->priv->watches; *ptr; ptr = &(*ptr)->next)
157 if ((*ptr)->target == where_the_object_was)
159 GSettingsBackendWatch *tmp = *ptr;
162 g_slice_free (GSettingsBackendWatch, tmp);
164 g_mutex_unlock (&backend->priv->lock);
168 /* we didn't find it. that shouldn't happen. */
169 g_assert_not_reached ();
173 * g_settings_backend_watch:
174 * @backend: a #GSettingsBackend
175 * @target: the GObject (typically GSettings instance) to call back to
176 * @context: (allow-none): a #GMainContext, or %NULL
179 * Registers a new watch on a #GSettingsBackend.
181 * note: %NULL @context does not mean "default main context" but rather,
182 * "it is okay to dispatch in any context". If the default main context
183 * is specifically desired then it must be given.
185 * note also: if you want to get meaningful values for the @origin_tag
186 * that appears as an argument to some of the callbacks, you *must* have
187 * @context as %NULL. Otherwise, you are subject to cross-thread
188 * dispatching and whatever owned @origin_tag at the time that the event
189 * occurred may no longer own it. This is a problem if you consider that
190 * you may now be the new owner of that address and mistakenly think
191 * that the event in question originated from yourself.
193 * tl;dr: If you give a non-%NULL @context then you must ignore the
194 * value of @origin_tag given to any callbacks.
197 g_settings_backend_watch (GSettingsBackend *backend,
198 const GSettingsListenerVTable *vtable,
200 GMainContext *context)
202 GSettingsBackendWatch *watch;
204 /* For purposes of discussion, we assume that our target is a
205 * GSettings instance.
207 * Our strategy to defend against the final reference dropping on the
208 * GSettings object in a thread other than the one that is doing the
209 * dispatching is as follows:
211 * 1) hold a GObject reference on the GSettings during an outstanding
212 * dispatch. This ensures that the delivery is always possible.
214 * 2) hold a weak reference on the GSettings at other times. This
215 * allows us to receive early notification of pending destruction
216 * of the object. At this point, it is still safe to obtain a
217 * reference on the GObject to keep it alive, so #1 will work up
218 * to that point. After that point, we'll have been able to drop
219 * the watch from the list.
221 * Note, in particular, that it's not possible to simply have an
222 * "unwatch" function that gets called from the finalize function of
223 * the GSettings instance because, by that point it is no longer
224 * possible to keep the object alive using g_object_ref() and we would
225 * have no way of knowing this.
227 * Note also that we do not need to hold a reference on the main
228 * context here since the GSettings instance does that for us and we
229 * will receive the weak notify long before it is dropped. We don't
230 * even need to hold it during dispatches because our reference on the
231 * GSettings will prevent the finalize from running and dropping the
232 * ref on the context.
234 * All access to the list holds a mutex. We have some strategies to
235 * avoid some of the pain that would be associated with that.
238 watch = g_slice_new (GSettingsBackendWatch);
239 watch->context = context;
240 watch->vtable = vtable;
241 watch->target = target;
242 g_object_weak_ref (target, g_settings_backend_watch_weak_notify, backend);
244 /* linked list prepend */
245 g_mutex_lock (&backend->priv->lock);
246 watch->next = backend->priv->watches;
247 backend->priv->watches = watch;
248 g_mutex_unlock (&backend->priv->lock);
252 g_settings_backend_unwatch (GSettingsBackend *backend,
255 /* Our caller surely owns a reference on 'target', so the order of
256 * these two calls is unimportant.
258 g_object_weak_unref (target, g_settings_backend_watch_weak_notify, backend);
259 g_settings_backend_watch_weak_notify (backend, target);
263 g_settings_backend_invoke_closure (gpointer user_data)
265 GSettingsBackendClosure *closure = user_data;
267 closure->function (closure->target, closure->backend, closure->name,
268 closure->data1, closure->data2);
270 closure->data1_free (closure->data1);
271 g_object_unref (closure->backend);
272 g_object_unref (closure->target);
273 g_free (closure->name);
275 g_slice_free (GSettingsBackendClosure, closure);
281 pointer_id (gpointer a)
287 pointer_ignore (gpointer a)
292 g_settings_backend_dispatch_signal (GSettingsBackend *backend,
293 gsize function_offset,
296 GBoxedCopyFunc data1_copy,
297 GBoxedFreeFunc data1_free,
300 GSettingsBackendWatch *suffix, *watch, *next;
302 if (data1_copy == NULL)
303 data1_copy = pointer_id;
305 if (data1_free == NULL)
306 data1_free = pointer_ignore;
308 /* We're in a little bit of a tricky situation here. We need to hold
309 * a lock while traversing the list, but we don't want to hold the
310 * lock while calling back into user code.
312 * Since we're not holding the lock while we call user code, we can't
313 * render the list immutable. We can, however, store a pointer to a
314 * given suffix of the list and render that suffix immutable.
316 * Adds will never modify the suffix since adds always come in the
317 * form of prepends. We can also prevent removes from modifying the
318 * suffix since removes only happen in response to the last reference
319 * count dropping -- so just add a reference to everything in the
322 g_mutex_lock (&backend->priv->lock);
323 suffix = backend->priv->watches;
324 for (watch = suffix; watch; watch = watch->next)
325 g_object_ref (watch->target);
326 g_mutex_unlock (&backend->priv->lock);
328 /* The suffix is now immutable, so this is safe. */
329 for (watch = suffix; watch; watch = next)
331 GSettingsBackendClosure *closure;
333 closure = g_slice_new (GSettingsBackendClosure);
334 closure->backend = g_object_ref (backend);
335 closure->target = watch->target; /* we took our ref above */
336 closure->function = G_STRUCT_MEMBER (void *, watch->vtable,
338 closure->name = g_strdup (name);
339 closure->data1 = data1_copy (data1);
340 closure->data1_free = data1_free;
341 closure->data2 = data2;
343 /* we do this here because 'watch' may not live to the end of this
344 * iteration of the loop (since we may unref the target below).
349 g_main_context_invoke (watch->context,
350 g_settings_backend_invoke_closure,
353 g_settings_backend_invoke_closure (closure);
358 * g_settings_backend_changed:
359 * @backend: a #GSettingsBackend implementation
360 * @key: the name of the key
361 * @origin_tag: the origin tag
363 * Signals that a single key has possibly changed. Backend
364 * implementations should call this if a key has possibly changed its
367 * @key must be a valid key (ie starting with a slash, not containing
368 * '//', and not ending with a slash).
370 * The implementation must call this function during any call to
371 * g_settings_backend_write(), before the call returns (except in the
372 * case that no keys are actually changed and it cares to detect this
373 * fact). It may not rely on the existence of a mainloop for
374 * dispatching the signal later.
376 * The implementation may call this function at any other time it likes
377 * in response to other events (such as changes occurring outside of the
378 * program). These calls may originate from a mainloop or may originate
379 * in response to any other action (including from calls to
380 * g_settings_backend_write()).
382 * In the case that this call is in response to a call to
383 * g_settings_backend_write() then @origin_tag must be set to the same
384 * value that was passed to that call.
389 g_settings_backend_changed (GSettingsBackend *backend,
393 g_return_if_fail (G_IS_SETTINGS_BACKEND (backend));
394 g_return_if_fail (is_key (key));
396 g_settings_backend_dispatch_signal (backend,
397 G_STRUCT_OFFSET (GSettingsListenerVTable,
399 key, origin_tag, NULL, NULL, NULL);
403 * g_settings_backend_keys_changed:
404 * @backend: a #GSettingsBackend implementation
405 * @path: the path containing the changes
406 * @items: (array zero-terminated=1): the %NULL-terminated list of changed keys
407 * @origin_tag: the origin tag
409 * Signals that a list of keys have possibly changed. Backend
410 * implementations should call this if keys have possibly changed their
413 * @path must be a valid path (ie starting and ending with a slash and
414 * not containing '//'). Each string in @items must form a valid key
415 * name when @path is prefixed to it (ie: each item must not start or
416 * end with '/' and must not contain '//').
418 * The meaning of this signal is that any of the key names resulting
419 * from the contatenation of @path with each item in @items may have
422 * The same rules for when notifications must occur apply as per
423 * g_settings_backend_changed(). These two calls can be used
424 * interchangeably if exactly one item has changed (although in that
425 * case g_settings_backend_changed() is definitely preferred).
427 * For efficiency reasons, the implementation should strive for @path to
428 * be as long as possible (ie: the longest common prefix of all of the
429 * keys that were changed) but this is not strictly required.
434 g_settings_backend_keys_changed (GSettingsBackend *backend,
436 gchar const * const *items,
439 g_return_if_fail (G_IS_SETTINGS_BACKEND (backend));
440 g_return_if_fail (is_path (path));
442 /* XXX: should do stricter checking (ie: inspect each item) */
443 g_return_if_fail (items != NULL);
445 g_settings_backend_dispatch_signal (backend,
446 G_STRUCT_OFFSET (GSettingsListenerVTable,
448 path, (gpointer) items,
449 (GBoxedCopyFunc) g_strdupv,
450 (GBoxedFreeFunc) g_strfreev,
455 * g_settings_backend_path_changed:
456 * @backend: a #GSettingsBackend implementation
457 * @path: the path containing the changes
458 * @origin_tag: the origin tag
460 * Signals that all keys below a given path may have possibly changed.
461 * Backend implementations should call this if an entire path of keys
462 * have possibly changed their values.
464 * @path must be a valid path (ie starting and ending with a slash and
465 * not containing '//').
467 * The meaning of this signal is that any of the key which has a name
468 * starting with @path may have changed.
470 * The same rules for when notifications must occur apply as per
471 * g_settings_backend_changed(). This call might be an appropriate
472 * reasponse to a 'reset' call but implementations are also free to
473 * explicitly list the keys that were affected by that call if they can
476 * For efficiency reasons, the implementation should strive for @path to
477 * be as long as possible (ie: the longest common prefix of all of the
478 * keys that were changed) but this is not strictly required. As an
479 * example, if this function is called with the path of "/" then every
480 * single key in the application will be notified of a possible change.
485 g_settings_backend_path_changed (GSettingsBackend *backend,
489 g_return_if_fail (G_IS_SETTINGS_BACKEND (backend));
490 g_return_if_fail (is_path (path));
492 g_settings_backend_dispatch_signal (backend,
493 G_STRUCT_OFFSET (GSettingsListenerVTable,
495 path, origin_tag, NULL, NULL, NULL);
499 * g_settings_backend_writable_changed:
500 * @backend: a #GSettingsBackend implementation
501 * @key: the name of the key
503 * Signals that the writability of a single key has possibly changed.
505 * Since GSettings performs no locking operations for itself, this call
506 * will always be made in response to external events.
511 g_settings_backend_writable_changed (GSettingsBackend *backend,
514 g_return_if_fail (G_IS_SETTINGS_BACKEND (backend));
515 g_return_if_fail (is_key (key));
517 g_settings_backend_dispatch_signal (backend,
518 G_STRUCT_OFFSET (GSettingsListenerVTable,
520 key, NULL, NULL, NULL, NULL);
524 * g_settings_backend_path_writable_changed:
525 * @backend: a #GSettingsBackend implementation
526 * @path: the name of the path
528 * Signals that the writability of all keys below a given path may have
531 * Since GSettings performs no locking operations for itself, this call
532 * will always be made in response to external events.
537 g_settings_backend_path_writable_changed (GSettingsBackend *backend,
540 g_return_if_fail (G_IS_SETTINGS_BACKEND (backend));
541 g_return_if_fail (is_path (path));
543 g_settings_backend_dispatch_signal (backend,
544 G_STRUCT_OFFSET (GSettingsListenerVTable,
545 path_writable_changed),
546 path, NULL, NULL, NULL, NULL);
558 g_settings_backend_flatten_one (gpointer key,
562 FlattenState *state = user_data;
563 const gchar *skey = key;
566 g_return_val_if_fail (is_key (key), TRUE);
568 /* calculate longest common prefix */
569 if (state->prefix == NULL)
573 /* first key? just take the prefix up to the last '/' */
574 state->prefix = g_strdup (skey);
575 last_byte = strrchr (state->prefix, '/') + 1;
576 state->prefix_len = last_byte - state->prefix;
581 /* find the first character that does not match. we will
582 * definitely find one because the prefix ends in '/' and the key
583 * does not. also: no two keys in the tree are the same.
585 for (i = 0; state->prefix[i] == skey[i]; i++);
587 /* check if we need to shorten the prefix */
588 if (state->prefix[i] != '\0')
590 /* find the nearest '/', terminate after it */
591 while (state->prefix[i - 1] != '/')
594 state->prefix[i] = '\0';
595 state->prefix_len = i;
600 /* save the entire item into the array.
601 * the prefixes will be removed later.
603 *state->keys++ = key;
606 *state->values++ = value;
612 * g_settings_backend_flatten_tree:
613 * @tree: a #GTree containing the changes
614 * @path: (out): the location to save the path
615 * @keys: (out) (transfer container) (array zero-terminated=1): the
616 * location to save the relative keys
617 * @values: (out) (allow-none) (transfer container) (array zero-terminated=1):
618 * the location to save the values, or %NULL
620 * Calculate the longest common prefix of all keys in a tree and write
621 * out an array of the key names relative to that prefix and,
622 * optionally, the value to store at each of those keys.
624 * You must free the value returned in @path, @keys and @values using
625 * g_free(). You should not attempt to free or unref the contents of
631 g_settings_backend_flatten_tree (GTree *tree,
636 FlattenState state = { 0, };
639 nnodes = g_tree_nnodes (tree);
641 *keys = state.keys = g_new (const gchar *, nnodes + 1);
642 state.keys[nnodes] = NULL;
646 *values = state.values = g_new (GVariant *, nnodes + 1);
647 state.values[nnodes] = NULL;
650 g_tree_foreach (tree, g_settings_backend_flatten_one, &state);
651 g_return_if_fail (*keys + nnodes == state.keys);
653 *path = state.prefix;
655 *--state.keys += state.prefix_len;
659 * g_settings_backend_changed_tree:
660 * @backend: a #GSettingsBackend implementation
661 * @tree: a #GTree containing the changes
662 * @origin_tag: the origin tag
664 * This call is a convenience wrapper. It gets the list of changes from
665 * @tree, computes the longest common prefix and calls
666 * g_settings_backend_changed().
671 g_settings_backend_changed_tree (GSettingsBackend *backend,
678 g_return_if_fail (G_IS_SETTINGS_BACKEND (backend));
680 g_settings_backend_flatten_tree (tree, &path, &keys, NULL);
687 g_print ("changed_tree(): prefix %s\n", path);
688 for (i = 0; keys[i]; i++)
689 g_print (" %s\n", keys[i]);
694 g_settings_backend_keys_changed (backend, path, keys, origin_tag);
700 * g_settings_backend_read:
701 * @backend: a #GSettingsBackend implementation
702 * @key: the key to read
703 * @expected_type: a #GVariantType
704 * @default_value: if the default value should be returned
706 * Reads a key. This call will never block.
708 * If the key exists, the value associated with it will be returned.
709 * If the key does not exist, %NULL will be returned.
711 * The returned value will be of the type given in @expected_type. If
712 * the backend stored a value of a different type then %NULL will be
715 * If @default_value is %TRUE then this gets the default value from the
716 * backend (ie: the one that the backend would contain if
717 * g_settings_reset() were called).
719 * Returns: the value that was read, or %NULL
722 g_settings_backend_read (GSettingsBackend *backend,
724 const GVariantType *expected_type,
725 gboolean default_value)
729 value = G_SETTINGS_BACKEND_GET_CLASS (backend)
730 ->read (backend, key, expected_type, default_value);
733 value = g_variant_take_ref (value);
735 if G_UNLIKELY (value && !g_variant_is_of_type (value, expected_type))
737 g_variant_unref (value);
745 * g_settings_backend_read_user_value:
746 * @backend: a #GSettingsBackend implementation
747 * @key: the key to read
748 * @expected_type: a #GVariantType
750 * Reads the 'user value' of a key.
752 * This is the value of the key that the user has control over and has
753 * set for themselves. Put another way: if the user did not set the
754 * value for themselves, then this will return %NULL (even if the
755 * sysadmin has provided a default value).
757 * Returns: the value that was read, or %NULL
760 g_settings_backend_read_user_value (GSettingsBackend *backend,
762 const GVariantType *expected_type)
766 value = G_SETTINGS_BACKEND_GET_CLASS (backend)
767 ->read_user_value (backend, key, expected_type);
770 value = g_variant_take_ref (value);
772 if G_UNLIKELY (value && !g_variant_is_of_type (value, expected_type))
774 g_variant_unref (value);
782 * g_settings_backend_write:
783 * @backend: a #GSettingsBackend implementation
784 * @key: the name of the key
785 * @value: a #GVariant value to write to this key
786 * @origin_tag: the origin tag
788 * Writes exactly one key.
790 * This call does not fail. During this call a
791 * #GSettingsBackend::changed signal will be emitted if the value of the
792 * key has changed. The updated key value will be visible to any signal
795 * One possible method that an implementation might deal with failures is
796 * to emit a second "changed" signal (either during this call, or later)
797 * to indicate that the affected keys have suddenly "changed back" to their
800 * Returns: %TRUE if the write succeeded, %FALSE if the key was not writable
803 g_settings_backend_write (GSettingsBackend *backend,
810 g_variant_ref_sink (value);
811 success = G_SETTINGS_BACKEND_GET_CLASS (backend)
812 ->write (backend, key, value, origin_tag);
813 g_variant_unref (value);
819 * g_settings_backend_write_tree:
820 * @backend: a #GSettingsBackend implementation
821 * @tree: a #GTree containing key-value pairs to write
822 * @origin_tag: the origin tag
824 * Writes one or more keys. This call will never block.
826 * The key of each item in the tree is the key name to write to and the
827 * value is a #GVariant to write. The proper type of #GTree for this
828 * call can be created with g_settings_backend_create_tree(). This call
829 * might take a reference to the tree; you must not modified the #GTree
830 * after passing it to this call.
832 * This call does not fail. During this call a #GSettingsBackend::changed
833 * signal will be emitted if any keys have been changed. The new values of
834 * all updated keys will be visible to any signal callbacks.
836 * One possible method that an implementation might deal with failures is
837 * to emit a second "changed" signal (either during this call, or later)
838 * to indicate that the affected keys have suddenly "changed back" to their
842 g_settings_backend_write_tree (GSettingsBackend *backend,
846 return G_SETTINGS_BACKEND_GET_CLASS (backend)
847 ->write_tree (backend, tree, origin_tag);
851 * g_settings_backend_reset:
852 * @backend: a #GSettingsBackend implementation
853 * @key: the name of a key
854 * @origin_tag: the origin tag
856 * "Resets" the named key to its "default" value (ie: after system-wide
857 * defaults, mandatory keys, etc. have been taken into account) or possibly
861 g_settings_backend_reset (GSettingsBackend *backend,
865 G_SETTINGS_BACKEND_GET_CLASS (backend)
866 ->reset (backend, key, origin_tag);
870 * g_settings_backend_get_writable:
871 * @backend: a #GSettingsBackend implementation
872 * @key: the name of a key
874 * Finds out if a key is available for writing to. This is the
875 * interface through which 'lockdown' is implemented. Locked down
876 * keys will have %FALSE returned by this call.
878 * You should not write to locked-down keys, but if you do, the
879 * implementation will deal with it.
881 * Returns: %TRUE if the key is writable
884 g_settings_backend_get_writable (GSettingsBackend *backend,
887 return G_SETTINGS_BACKEND_GET_CLASS (backend)
888 ->get_writable (backend, key);
892 * g_settings_backend_unsubscribe:
893 * @backend: a #GSettingsBackend
894 * @name: a key or path to subscribe to
896 * Reverses the effect of a previous call to
897 * g_settings_backend_subscribe().
900 g_settings_backend_unsubscribe (GSettingsBackend *backend,
903 G_SETTINGS_BACKEND_GET_CLASS (backend)
904 ->unsubscribe (backend, name);
908 * g_settings_backend_subscribe:
909 * @backend: a #GSettingsBackend
910 * @name: a key or path to subscribe to
912 * Requests that change signals be emitted for events on @name.
915 g_settings_backend_subscribe (GSettingsBackend *backend,
918 G_SETTINGS_BACKEND_GET_CLASS (backend)
919 ->subscribe (backend, name);
923 g_settings_backend_finalize (GObject *object)
925 GSettingsBackend *backend = G_SETTINGS_BACKEND (object);
927 g_mutex_clear (&backend->priv->lock);
929 G_OBJECT_CLASS (g_settings_backend_parent_class)
934 ignore_subscription (GSettingsBackend *backend,
940 g_settings_backend_real_read_user_value (GSettingsBackend *backend,
942 const GVariantType *expected_type)
944 return g_settings_backend_read (backend, key, expected_type, FALSE);
948 g_settings_backend_init (GSettingsBackend *backend)
950 backend->priv = g_settings_backend_get_instance_private (backend);
951 g_mutex_init (&backend->priv->lock);
955 g_settings_backend_class_init (GSettingsBackendClass *class)
957 GObjectClass *gobject_class = G_OBJECT_CLASS (class);
959 class->subscribe = ignore_subscription;
960 class->unsubscribe = ignore_subscription;
962 class->read_user_value = g_settings_backend_real_read_user_value;
964 gobject_class->finalize = g_settings_backend_finalize;
968 g_settings_backend_variant_unref0 (gpointer data)
971 g_variant_unref (data);
975 * g_settings_backend_create_tree:
977 * This is a convenience function for creating a tree that is compatible
978 * with g_settings_backend_write(). It merely calls g_tree_new_full()
979 * with strcmp(), g_free() and g_variant_unref().
981 * Returns: a new #GTree
984 g_settings_backend_create_tree (void)
986 return g_tree_new_full ((GCompareDataFunc) strcmp, NULL,
987 g_free, g_settings_backend_variant_unref0);
991 g_settings_backend_verify (gpointer impl)
993 GSettingsBackend *backend = impl;
995 if (strcmp (G_OBJECT_TYPE_NAME (backend), "GMemorySettingsBackend") == 0 &&
996 g_strcmp0 (g_getenv ("GSETTINGS_BACKEND"), "memory") != 0)
998 g_message ("Using the 'memory' GSettings backend. Your settings "
999 "will not be saved or shared with other applications.");
1002 g_settings_has_backend = TRUE;
1007 * g_settings_backend_get_default:
1009 * Returns the default #GSettingsBackend. It is possible to override
1010 * the default by setting the `GSETTINGS_BACKEND` environment variable
1011 * to the name of a settings backend.
1013 * The user gets a reference to the backend.
1015 * Returns: (transfer full): the default #GSettingsBackend
1020 g_settings_backend_get_default (void)
1022 GSettingsBackend *backend;
1024 backend = _g_io_module_get_default (G_SETTINGS_BACKEND_EXTENSION_POINT_NAME,
1025 "GSETTINGS_BACKEND",
1026 g_settings_backend_verify);
1027 return g_object_ref (backend);
1031 * g_settings_backend_get_permission:
1032 * @backend: a #GSettingsBackend
1035 * Gets the permission object associated with writing to keys below
1036 * @path on @backend.
1038 * If this is not implemented in the backend, then a %TRUE
1039 * #GSimplePermission is returned.
1041 * Returns: a non-%NULL #GPermission. Free with g_object_unref()
1044 g_settings_backend_get_permission (GSettingsBackend *backend,
1047 GSettingsBackendClass *class = G_SETTINGS_BACKEND_GET_CLASS (backend);
1049 if (class->get_permission)
1050 return class->get_permission (backend, path);
1052 return g_simple_permission_new (TRUE);
1056 * g_settings_backend_sync_default:
1058 * Syncs the default backend.
1061 g_settings_backend_sync_default (void)
1063 if (g_settings_has_backend)
1065 GSettingsBackendClass *class;
1066 GSettingsBackend *backend;
1068 backend = g_settings_backend_get_default ();
1069 class = G_SETTINGS_BACKEND_GET_CLASS (backend);
1072 class->sync (backend);