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,
140 GSettingsBackend *backend;
147 g_settings_backend_watch_weak_notify (gpointer data,
148 GObject *where_the_object_was)
150 GSettingsBackend *backend = data;
151 GSettingsBackendWatch **ptr;
153 /* search and remove */
154 g_mutex_lock (&backend->priv->lock);
155 for (ptr = &backend->priv->watches; *ptr; ptr = &(*ptr)->next)
156 if ((*ptr)->target == where_the_object_was)
158 GSettingsBackendWatch *tmp = *ptr;
161 g_slice_free (GSettingsBackendWatch, tmp);
163 g_mutex_unlock (&backend->priv->lock);
167 /* we didn't find it. that shouldn't happen. */
168 g_assert_not_reached ();
172 * g_settings_backend_watch:
173 * @backend: a #GSettingsBackend
174 * @target: the GObject (typically GSettings instance) to call back to
175 * @context: (allow-none): a #GMainContext, or %NULL
178 * Registers a new watch on a #GSettingsBackend.
180 * note: %NULL @context does not mean "default main context" but rather,
181 * "it is okay to dispatch in any context". If the default main context
182 * is specifically desired then it must be given.
184 * note also: if you want to get meaningful values for the @origin_tag
185 * that appears as an argument to some of the callbacks, you *must* have
186 * @context as %NULL. Otherwise, you are subject to cross-thread
187 * dispatching and whatever owned @origin_tag at the time that the event
188 * occurred may no longer own it. This is a problem if you consider that
189 * you may now be the new owner of that address and mistakenly think
190 * that the event in question originated from yourself.
192 * tl;dr: If you give a non-%NULL @context then you must ignore the
193 * value of @origin_tag given to any callbacks.
196 g_settings_backend_watch (GSettingsBackend *backend,
197 const GSettingsListenerVTable *vtable,
199 GMainContext *context)
201 GSettingsBackendWatch *watch;
203 /* For purposes of discussion, we assume that our target is a
204 * GSettings instance.
206 * Our strategy to defend against the final reference dropping on the
207 * GSettings object in a thread other than the one that is doing the
208 * dispatching is as follows:
210 * 1) hold a GObject reference on the GSettings during an outstanding
211 * dispatch. This ensures that the delivery is always possible.
213 * 2) hold a weak reference on the GSettings at other times. This
214 * allows us to receive early notification of pending destruction
215 * of the object. At this point, it is still safe to obtain a
216 * reference on the GObject to keep it alive, so #1 will work up
217 * to that point. After that point, we'll have been able to drop
218 * the watch from the list.
220 * Note, in particular, that it's not possible to simply have an
221 * "unwatch" function that gets called from the finalize function of
222 * the GSettings instance because, by that point it is no longer
223 * possible to keep the object alive using g_object_ref() and we would
224 * have no way of knowing this.
226 * Note also that we do not need to hold a reference on the main
227 * context here since the GSettings instance does that for us and we
228 * will receive the weak notify long before it is dropped. We don't
229 * even need to hold it during dispatches because our reference on the
230 * GSettings will prevent the finalize from running and dropping the
231 * ref on the context.
233 * All access to the list holds a mutex. We have some strategies to
234 * avoid some of the pain that would be associated with that.
237 watch = g_slice_new (GSettingsBackendWatch);
238 watch->context = context;
239 watch->vtable = vtable;
240 watch->target = target;
241 g_object_weak_ref (target, g_settings_backend_watch_weak_notify, backend);
243 /* linked list prepend */
244 g_mutex_lock (&backend->priv->lock);
245 watch->next = backend->priv->watches;
246 backend->priv->watches = watch;
247 g_mutex_unlock (&backend->priv->lock);
251 g_settings_backend_unwatch (GSettingsBackend *backend,
254 /* Our caller surely owns a reference on 'target', so the order of
255 * these two calls is unimportant.
257 g_object_weak_unref (target, g_settings_backend_watch_weak_notify, backend);
258 g_settings_backend_watch_weak_notify (backend, target);
262 g_settings_backend_invoke_closure (gpointer user_data)
264 GSettingsBackendClosure *closure = user_data;
266 closure->function (closure->target, closure->backend, closure->name,
267 closure->origin_tag, closure->names);
269 g_object_unref (closure->backend);
270 g_object_unref (closure->target);
271 g_strfreev (closure->names);
272 g_free (closure->name);
274 g_slice_free (GSettingsBackendClosure, closure);
280 g_settings_backend_dispatch_signal (GSettingsBackend *backend,
281 gsize function_offset,
284 const gchar * const *names)
286 GSettingsBackendWatch *suffix, *watch, *next;
288 /* We're in a little bit of a tricky situation here. We need to hold
289 * a lock while traversing the list, but we don't want to hold the
290 * lock while calling back into user code.
292 * Since we're not holding the lock while we call user code, we can't
293 * render the list immutable. We can, however, store a pointer to a
294 * given suffix of the list and render that suffix immutable.
296 * Adds will never modify the suffix since adds always come in the
297 * form of prepends. We can also prevent removes from modifying the
298 * suffix since removes only happen in response to the last reference
299 * count dropping -- so just add a reference to everything in the
302 g_mutex_lock (&backend->priv->lock);
303 suffix = backend->priv->watches;
304 for (watch = suffix; watch; watch = watch->next)
305 g_object_ref (watch->target);
306 g_mutex_unlock (&backend->priv->lock);
308 /* The suffix is now immutable, so this is safe. */
309 for (watch = suffix; watch; watch = next)
311 GSettingsBackendClosure *closure;
313 closure = g_slice_new (GSettingsBackendClosure);
314 closure->backend = g_object_ref (backend);
315 closure->target = watch->target; /* we took our ref above */
316 closure->function = G_STRUCT_MEMBER (void *, watch->vtable,
318 closure->name = g_strdup (name);
319 closure->origin_tag = origin_tag;
320 closure->names = g_strdupv ((gchar **) names);
322 /* we do this here because 'watch' may not live to the end of this
323 * iteration of the loop (since we may unref the target below).
328 g_main_context_invoke (watch->context,
329 g_settings_backend_invoke_closure,
332 g_settings_backend_invoke_closure (closure);
337 * g_settings_backend_changed:
338 * @backend: a #GSettingsBackend implementation
339 * @key: the name of the key
340 * @origin_tag: the origin tag
342 * Signals that a single key has possibly changed. Backend
343 * implementations should call this if a key has possibly changed its
346 * @key must be a valid key (ie starting with a slash, not containing
347 * '//', and not ending with a slash).
349 * The implementation must call this function during any call to
350 * g_settings_backend_write(), before the call returns (except in the
351 * case that no keys are actually changed and it cares to detect this
352 * fact). It may not rely on the existence of a mainloop for
353 * dispatching the signal later.
355 * The implementation may call this function at any other time it likes
356 * in response to other events (such as changes occurring outside of the
357 * program). These calls may originate from a mainloop or may originate
358 * in response to any other action (including from calls to
359 * g_settings_backend_write()).
361 * In the case that this call is in response to a call to
362 * g_settings_backend_write() then @origin_tag must be set to the same
363 * value that was passed to that call.
368 g_settings_backend_changed (GSettingsBackend *backend,
372 g_return_if_fail (G_IS_SETTINGS_BACKEND (backend));
373 g_return_if_fail (is_key (key));
375 g_settings_backend_dispatch_signal (backend,
376 G_STRUCT_OFFSET (GSettingsListenerVTable,
378 key, origin_tag, NULL);
382 * g_settings_backend_keys_changed:
383 * @backend: a #GSettingsBackend implementation
384 * @path: the path containing the changes
385 * @items: (array zero-terminated=1): the %NULL-terminated list of changed keys
386 * @origin_tag: the origin tag
388 * Signals that a list of keys have possibly changed. Backend
389 * implementations should call this if keys have possibly changed their
392 * @path must be a valid path (ie starting and ending with a slash and
393 * not containing '//'). Each string in @items must form a valid key
394 * name when @path is prefixed to it (ie: each item must not start or
395 * end with '/' and must not contain '//').
397 * The meaning of this signal is that any of the key names resulting
398 * from the contatenation of @path with each item in @items may have
401 * The same rules for when notifications must occur apply as per
402 * g_settings_backend_changed(). These two calls can be used
403 * interchangeably if exactly one item has changed (although in that
404 * case g_settings_backend_changed() is definitely preferred).
406 * For efficiency reasons, the implementation should strive for @path to
407 * be as long as possible (ie: the longest common prefix of all of the
408 * keys that were changed) but this is not strictly required.
413 g_settings_backend_keys_changed (GSettingsBackend *backend,
415 gchar const * const *items,
418 g_return_if_fail (G_IS_SETTINGS_BACKEND (backend));
419 g_return_if_fail (is_path (path));
421 /* XXX: should do stricter checking (ie: inspect each item) */
422 g_return_if_fail (items != NULL);
424 g_settings_backend_dispatch_signal (backend,
425 G_STRUCT_OFFSET (GSettingsListenerVTable,
427 path, origin_tag, items);
431 * g_settings_backend_path_changed:
432 * @backend: a #GSettingsBackend implementation
433 * @path: the path containing the changes
434 * @origin_tag: the origin tag
436 * Signals that all keys below a given path may have possibly changed.
437 * Backend implementations should call this if an entire path of keys
438 * have possibly changed their values.
440 * @path must be a valid path (ie starting and ending with a slash and
441 * not containing '//').
443 * The meaning of this signal is that any of the key which has a name
444 * starting with @path may have changed.
446 * The same rules for when notifications must occur apply as per
447 * g_settings_backend_changed(). This call might be an appropriate
448 * reasponse to a 'reset' call but implementations are also free to
449 * explicitly list the keys that were affected by that call if they can
452 * For efficiency reasons, the implementation should strive for @path to
453 * be as long as possible (ie: the longest common prefix of all of the
454 * keys that were changed) but this is not strictly required. As an
455 * example, if this function is called with the path of "/" then every
456 * single key in the application will be notified of a possible change.
461 g_settings_backend_path_changed (GSettingsBackend *backend,
465 g_return_if_fail (G_IS_SETTINGS_BACKEND (backend));
466 g_return_if_fail (is_path (path));
468 g_settings_backend_dispatch_signal (backend,
469 G_STRUCT_OFFSET (GSettingsListenerVTable,
471 path, origin_tag, NULL);
475 * g_settings_backend_writable_changed:
476 * @backend: a #GSettingsBackend implementation
477 * @key: the name of the key
479 * Signals that the writability of a single key has possibly changed.
481 * Since GSettings performs no locking operations for itself, this call
482 * will always be made in response to external events.
487 g_settings_backend_writable_changed (GSettingsBackend *backend,
490 g_return_if_fail (G_IS_SETTINGS_BACKEND (backend));
491 g_return_if_fail (is_key (key));
493 g_settings_backend_dispatch_signal (backend,
494 G_STRUCT_OFFSET (GSettingsListenerVTable,
500 * g_settings_backend_path_writable_changed:
501 * @backend: a #GSettingsBackend implementation
502 * @path: the name of the path
504 * Signals that the writability of all keys below a given path may have
507 * Since GSettings performs no locking operations for itself, this call
508 * will always be made in response to external events.
513 g_settings_backend_path_writable_changed (GSettingsBackend *backend,
516 g_return_if_fail (G_IS_SETTINGS_BACKEND (backend));
517 g_return_if_fail (is_path (path));
519 g_settings_backend_dispatch_signal (backend,
520 G_STRUCT_OFFSET (GSettingsListenerVTable,
521 path_writable_changed),
534 g_settings_backend_flatten_one (gpointer key,
538 FlattenState *state = user_data;
539 const gchar *skey = key;
542 g_return_val_if_fail (is_key (key), TRUE);
544 /* calculate longest common prefix */
545 if (state->prefix == NULL)
549 /* first key? just take the prefix up to the last '/' */
550 state->prefix = g_strdup (skey);
551 last_byte = strrchr (state->prefix, '/') + 1;
552 state->prefix_len = last_byte - state->prefix;
557 /* find the first character that does not match. we will
558 * definitely find one because the prefix ends in '/' and the key
559 * does not. also: no two keys in the tree are the same.
561 for (i = 0; state->prefix[i] == skey[i]; i++);
563 /* check if we need to shorten the prefix */
564 if (state->prefix[i] != '\0')
566 /* find the nearest '/', terminate after it */
567 while (state->prefix[i - 1] != '/')
570 state->prefix[i] = '\0';
571 state->prefix_len = i;
576 /* save the entire item into the array.
577 * the prefixes will be removed later.
579 *state->keys++ = key;
582 *state->values++ = value;
588 * g_settings_backend_flatten_tree:
589 * @tree: a #GTree containing the changes
590 * @path: (out): the location to save the path
591 * @keys: (out) (transfer container) (array zero-terminated=1): the
592 * location to save the relative keys
593 * @values: (out) (allow-none) (transfer container) (array zero-terminated=1):
594 * the location to save the values, or %NULL
596 * Calculate the longest common prefix of all keys in a tree and write
597 * out an array of the key names relative to that prefix and,
598 * optionally, the value to store at each of those keys.
600 * You must free the value returned in @path, @keys and @values using
601 * g_free(). You should not attempt to free or unref the contents of
607 g_settings_backend_flatten_tree (GTree *tree,
612 FlattenState state = { 0, };
615 nnodes = g_tree_nnodes (tree);
617 *keys = state.keys = g_new (const gchar *, nnodes + 1);
618 state.keys[nnodes] = NULL;
622 *values = state.values = g_new (GVariant *, nnodes + 1);
623 state.values[nnodes] = NULL;
626 g_tree_foreach (tree, g_settings_backend_flatten_one, &state);
627 g_return_if_fail (*keys + nnodes == state.keys);
629 *path = state.prefix;
631 *--state.keys += state.prefix_len;
635 * g_settings_backend_changed_tree:
636 * @backend: a #GSettingsBackend implementation
637 * @tree: a #GTree containing the changes
638 * @origin_tag: the origin tag
640 * This call is a convenience wrapper. It gets the list of changes from
641 * @tree, computes the longest common prefix and calls
642 * g_settings_backend_changed().
647 g_settings_backend_changed_tree (GSettingsBackend *backend,
654 g_return_if_fail (G_IS_SETTINGS_BACKEND (backend));
656 g_settings_backend_flatten_tree (tree, &path, &keys, NULL);
663 g_print ("changed_tree(): prefix %s\n", path);
664 for (i = 0; keys[i]; i++)
665 g_print (" %s\n", keys[i]);
670 g_settings_backend_keys_changed (backend, path, keys, origin_tag);
676 * g_settings_backend_read:
677 * @backend: a #GSettingsBackend implementation
678 * @key: the key to read
679 * @expected_type: a #GVariantType
680 * @default_value: if the default value should be returned
682 * Reads a key. This call will never block.
684 * If the key exists, the value associated with it will be returned.
685 * If the key does not exist, %NULL will be returned.
687 * The returned value will be of the type given in @expected_type. If
688 * the backend stored a value of a different type then %NULL will be
691 * If @default_value is %TRUE then this gets the default value from the
692 * backend (ie: the one that the backend would contain if
693 * g_settings_reset() were called).
695 * Returns: the value that was read, or %NULL
698 g_settings_backend_read (GSettingsBackend *backend,
700 const GVariantType *expected_type,
701 gboolean default_value)
705 value = G_SETTINGS_BACKEND_GET_CLASS (backend)
706 ->read (backend, key, expected_type, default_value);
709 value = g_variant_take_ref (value);
711 if G_UNLIKELY (value && !g_variant_is_of_type (value, expected_type))
713 g_variant_unref (value);
721 * g_settings_backend_read_user_value:
722 * @backend: a #GSettingsBackend implementation
723 * @key: the key to read
724 * @expected_type: a #GVariantType
726 * Reads the 'user value' of a key.
728 * This is the value of the key that the user has control over and has
729 * set for themselves. Put another way: if the user did not set the
730 * value for themselves, then this will return %NULL (even if the
731 * sysadmin has provided a default value).
733 * Returns: the value that was read, or %NULL
736 g_settings_backend_read_user_value (GSettingsBackend *backend,
738 const GVariantType *expected_type)
742 value = G_SETTINGS_BACKEND_GET_CLASS (backend)
743 ->read_user_value (backend, key, expected_type);
746 value = g_variant_take_ref (value);
748 if G_UNLIKELY (value && !g_variant_is_of_type (value, expected_type))
750 g_variant_unref (value);
758 * g_settings_backend_write:
759 * @backend: a #GSettingsBackend implementation
760 * @key: the name of the key
761 * @value: a #GVariant value to write to this key
762 * @origin_tag: the origin tag
764 * Writes exactly one key.
766 * This call does not fail. During this call a
767 * #GSettingsBackend::changed signal will be emitted if the value of the
768 * key has changed. The updated key value will be visible to any signal
771 * One possible method that an implementation might deal with failures is
772 * to emit a second "changed" signal (either during this call, or later)
773 * to indicate that the affected keys have suddenly "changed back" to their
776 * Returns: %TRUE if the write succeeded, %FALSE if the key was not writable
779 g_settings_backend_write (GSettingsBackend *backend,
786 g_variant_ref_sink (value);
787 success = G_SETTINGS_BACKEND_GET_CLASS (backend)
788 ->write (backend, key, value, origin_tag);
789 g_variant_unref (value);
795 * g_settings_backend_write_tree:
796 * @backend: a #GSettingsBackend implementation
797 * @tree: a #GTree containing key-value pairs to write
798 * @origin_tag: the origin tag
800 * Writes one or more keys. This call will never block.
802 * The key of each item in the tree is the key name to write to and the
803 * value is a #GVariant to write. The proper type of #GTree for this
804 * call can be created with g_settings_backend_create_tree(). This call
805 * might take a reference to the tree; you must not modified the #GTree
806 * after passing it to this call.
808 * This call does not fail. During this call a #GSettingsBackend::changed
809 * signal will be emitted if any keys have been changed. The new values of
810 * all updated keys will be visible to any signal callbacks.
812 * One possible method that an implementation might deal with failures is
813 * to emit a second "changed" signal (either during this call, or later)
814 * to indicate that the affected keys have suddenly "changed back" to their
818 g_settings_backend_write_tree (GSettingsBackend *backend,
822 return G_SETTINGS_BACKEND_GET_CLASS (backend)
823 ->write_tree (backend, tree, origin_tag);
827 * g_settings_backend_reset:
828 * @backend: a #GSettingsBackend implementation
829 * @key: the name of a key
830 * @origin_tag: the origin tag
832 * "Resets" the named key to its "default" value (ie: after system-wide
833 * defaults, mandatory keys, etc. have been taken into account) or possibly
837 g_settings_backend_reset (GSettingsBackend *backend,
841 G_SETTINGS_BACKEND_GET_CLASS (backend)
842 ->reset (backend, key, origin_tag);
846 * g_settings_backend_get_writable:
847 * @backend: a #GSettingsBackend implementation
848 * @key: the name of a key
850 * Finds out if a key is available for writing to. This is the
851 * interface through which 'lockdown' is implemented. Locked down
852 * keys will have %FALSE returned by this call.
854 * You should not write to locked-down keys, but if you do, the
855 * implementation will deal with it.
857 * Returns: %TRUE if the key is writable
860 g_settings_backend_get_writable (GSettingsBackend *backend,
863 return G_SETTINGS_BACKEND_GET_CLASS (backend)
864 ->get_writable (backend, key);
868 * g_settings_backend_unsubscribe:
869 * @backend: a #GSettingsBackend
870 * @name: a key or path to subscribe to
872 * Reverses the effect of a previous call to
873 * g_settings_backend_subscribe().
876 g_settings_backend_unsubscribe (GSettingsBackend *backend,
879 G_SETTINGS_BACKEND_GET_CLASS (backend)
880 ->unsubscribe (backend, name);
884 * g_settings_backend_subscribe:
885 * @backend: a #GSettingsBackend
886 * @name: a key or path to subscribe to
888 * Requests that change signals be emitted for events on @name.
891 g_settings_backend_subscribe (GSettingsBackend *backend,
894 G_SETTINGS_BACKEND_GET_CLASS (backend)
895 ->subscribe (backend, name);
899 g_settings_backend_finalize (GObject *object)
901 GSettingsBackend *backend = G_SETTINGS_BACKEND (object);
903 g_mutex_clear (&backend->priv->lock);
905 G_OBJECT_CLASS (g_settings_backend_parent_class)
910 ignore_subscription (GSettingsBackend *backend,
916 g_settings_backend_real_read_user_value (GSettingsBackend *backend,
918 const GVariantType *expected_type)
920 return g_settings_backend_read (backend, key, expected_type, FALSE);
924 g_settings_backend_init (GSettingsBackend *backend)
926 backend->priv = g_settings_backend_get_instance_private (backend);
927 g_mutex_init (&backend->priv->lock);
931 g_settings_backend_class_init (GSettingsBackendClass *class)
933 GObjectClass *gobject_class = G_OBJECT_CLASS (class);
935 class->subscribe = ignore_subscription;
936 class->unsubscribe = ignore_subscription;
938 class->read_user_value = g_settings_backend_real_read_user_value;
940 gobject_class->finalize = g_settings_backend_finalize;
944 g_settings_backend_variant_unref0 (gpointer data)
947 g_variant_unref (data);
951 * g_settings_backend_create_tree:
953 * This is a convenience function for creating a tree that is compatible
954 * with g_settings_backend_write(). It merely calls g_tree_new_full()
955 * with strcmp(), g_free() and g_variant_unref().
957 * Returns: a new #GTree
960 g_settings_backend_create_tree (void)
962 return g_tree_new_full ((GCompareDataFunc) strcmp, NULL,
963 g_free, g_settings_backend_variant_unref0);
967 g_settings_backend_verify (gpointer impl)
969 GSettingsBackend *backend = impl;
971 if (strcmp (G_OBJECT_TYPE_NAME (backend), "GMemorySettingsBackend") == 0 &&
972 g_strcmp0 (g_getenv ("GSETTINGS_BACKEND"), "memory") != 0)
974 g_message ("Using the 'memory' GSettings backend. Your settings "
975 "will not be saved or shared with other applications.");
978 g_settings_has_backend = TRUE;
983 * g_settings_backend_get_default:
985 * Returns the default #GSettingsBackend. It is possible to override
986 * the default by setting the `GSETTINGS_BACKEND` environment variable
987 * to the name of a settings backend.
989 * The user gets a reference to the backend.
991 * Returns: (transfer full): the default #GSettingsBackend
996 g_settings_backend_get_default (void)
998 GSettingsBackend *backend;
1000 backend = _g_io_module_get_default (G_SETTINGS_BACKEND_EXTENSION_POINT_NAME,
1001 "GSETTINGS_BACKEND",
1002 g_settings_backend_verify);
1003 return g_object_ref (backend);
1007 * g_settings_backend_get_permission:
1008 * @backend: a #GSettingsBackend
1011 * Gets the permission object associated with writing to keys below
1012 * @path on @backend.
1014 * If this is not implemented in the backend, then a %TRUE
1015 * #GSimplePermission is returned.
1017 * Returns: a non-%NULL #GPermission. Free with g_object_unref()
1020 g_settings_backend_get_permission (GSettingsBackend *backend,
1023 GSettingsBackendClass *class = G_SETTINGS_BACKEND_GET_CLASS (backend);
1025 if (class->get_permission)
1026 return class->get_permission (backend, path);
1028 return g_simple_permission_new (TRUE);
1032 * g_settings_backend_sync_default:
1034 * Syncs the default backend.
1037 g_settings_backend_sync_default (void)
1039 if (g_settings_has_backend)
1041 GSettingsBackendClass *class;
1042 GSettingsBackend *backend;
1044 backend = g_settings_backend_get_default ();
1045 class = G_SETTINGS_BACKEND_GET_CLASS (backend);
1048 class->sync (backend);