/* * Copyright © 2009, 2010 Codethink Limited * Copyright © 2010 Red Hat, Inc. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2 of the licence, or (at your option) any later version. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the * Free Software Foundation, Inc., 59 Temple Place - Suite 330, * Boston, MA 02111-1307, USA. * * Authors: Ryan Lortie * Matthias Clasen */ #include "config.h" #include "gsettingsbackendinternal.h" #include "gnullsettingsbackend.h" #include "giomodule-priv.h" #include "gio-marshal.h" #include #include #include #include #include "gioalias.h" G_DEFINE_ABSTRACT_TYPE (GSettingsBackend, g_settings_backend, G_TYPE_OBJECT) typedef struct _GSettingsBackendClosure GSettingsBackendClosure; typedef struct _GSettingsBackendWatch GSettingsBackendWatch; struct _GSettingsBackendPrivate { GSettingsBackendWatch *watches; GStaticMutex lock; gchar *context; }; enum { PROP_0, PROP_CONTEXT }; /** * SECTION:gsettingsbackend * @title: GSettingsBackend * @short_description: an interface for settings backend implementations * @include: gio/gsettingsbackend.h * @see_also: #GSettings, #GIOExtensionPoint * * The #GSettingsBackend interface defines a generic interface for * non-strictly-typed data that is stored in a hierarchy. To implement * an alternative storage backend for #GSettings, you need to implement * the #GSettingsBackend interface and then make it implement the * extension point #G_SETTINGS_BACKEND_EXTENSION_POINT_NAME. * * The interface defines methods for reading and writing values, a * method for determining if writing of certain values will fail * (lockdown) and a change notification mechanism. * * The semantics of the interface are very precisely defined and * implementations must carefully adhere to the expectations of * callers that are documented on each of the interface methods. * * Some of the GSettingsBackend functions accept or return a #GTree. * These trees always have strings as keys and #GVariant as values. * g_settings_backend_create_tree() is a convenience function to create * suitable trees. * * * The #GSettingsBackend API is exported to allow third-party * implementations, but does not carry the same stability guarantees * as the public GIO API. For this reason, you have to define the * C preprocessor symbol #G_SETTINGS_ENABLE_BACKEND before including * gio/gsettingsbackend.h * **/ static gboolean is_key (const gchar *key) { gint length; gint i; g_return_val_if_fail (key != NULL, FALSE); g_return_val_if_fail (key[0] == '/', FALSE); for (i = 1; key[i]; i++) g_return_val_if_fail (key[i] != '/' || key[i + 1] != '/', FALSE); length = i; g_return_val_if_fail (key[length - 1] != '/', FALSE); return TRUE; } static gboolean is_path (const gchar *path) { gint length; gint i; g_return_val_if_fail (path != NULL, FALSE); g_return_val_if_fail (path[0] == '/', FALSE); for (i = 1; path[i]; i++) g_return_val_if_fail (path[i] != '/' || path[i + 1] != '/', FALSE); length = i; g_return_val_if_fail (path[length - 1] == '/', FALSE); return TRUE; } GMainContext * g_settings_backend_get_active_context (void) { GMainContext *context; GSource *source; if ((source = g_main_current_source ())) context = g_source_get_context (source); else { context = g_main_context_get_thread_default (); if (context == NULL) context = g_main_context_default (); } return context; } struct _GSettingsBackendWatch { GObject *target; GMainContext *context; GSettingsBackendChangedFunc changed; GSettingsBackendPathChangedFunc path_changed; GSettingsBackendKeysChangedFunc keys_changed; GSettingsBackendWritableChangedFunc writable_changed; GSettingsBackendPathWritableChangedFunc path_writable_changed; GSettingsBackendWatch *next; }; struct _GSettingsBackendClosure { void (*function) (GSettingsBackend *backend, GObject *target, const gchar *name, gpointer data1, gpointer data2); GSettingsBackend *backend; GObject *target; gchar *name; gpointer data1; GBoxedFreeFunc data1_free; gpointer data2; }; static void g_settings_backend_watch_weak_notify (gpointer data, GObject *where_the_object_was) { GSettingsBackend *backend = data; GSettingsBackendWatch **ptr; /* search and remove */ g_static_mutex_lock (&backend->priv->lock); for (ptr = &backend->priv->watches; *ptr; ptr = &(*ptr)->next) if ((*ptr)->target == where_the_object_was) { GSettingsBackendWatch *tmp = *ptr; *ptr = tmp->next; g_slice_free (GSettingsBackendWatch, tmp); g_static_mutex_unlock (&backend->priv->lock); return; } /* we didn't find it. that shouldn't happen. */ g_assert_not_reached (); } /*< private > * g_settings_backend_watch: * @backend: a #GSettingsBackend * @target: the GObject (typically GSettings instance) to call back to * @context: a #GMainContext, or %NULL * ...: callbacks... * * Registers a new watch on a #GSettingsBackend. * * note: %NULL @context does not mean "default main context" but rather, * "it is okay to dispatch in any context". If the default main context * is specifically desired then it must be given. * * note also: if you want to get meaningful values for the @origin_tag * that appears as an argument to some of the callbacks, you *must* have * @context as %NULL. Otherwise, you are subject to cross-thread * dispatching and whatever owned @origin_tag at the time that the event * occured may no longer own it. This is a problem if you consider that * you may now be the new owner of that address and mistakenly think * that the event in question originated from yourself. * * tl;dr: If you give a non-%NULL @context then you must ignore the * value of @origin_tag given to any callbacks. **/ void g_settings_backend_watch (GSettingsBackend *backend, GObject *target, GMainContext *context, GSettingsBackendChangedFunc changed, GSettingsBackendPathChangedFunc path_changed, GSettingsBackendKeysChangedFunc keys_changed, GSettingsBackendWritableChangedFunc writable_changed, GSettingsBackendPathWritableChangedFunc path_writable_changed) { GSettingsBackendWatch *watch; /* For purposes of discussion, we assume that our target is a * GSettings instance. * * Our strategy to defend against the final reference dropping on the * GSettings object in a thread other than the one that is doing the * dispatching is as follows: * * 1) hold a GObject reference on the GSettings during an outstanding * dispatch. This ensures that the delivery is always possible. * * 2) hold a weak reference on the GSettings at other times. This * allows us to receive early notification of pending destruction * of the object. At this point, it is still safe to obtain a * reference on the GObject to keep it alive, so #1 will work up * to that point. After that point, we'll have been able to drop * the watch from the list. * * Note, in particular, that it's not possible to simply have an * "unwatch" function that gets called from the finalize function of * the GSettings instance because, by that point it is no longer * possible to keep the object alive using g_object_ref() and we would * have no way of knowing this. * * Note also that we do not need to hold a reference on the main * context here since the GSettings instance does that for us and we * will receive the weak notify long before it is dropped. We don't * even need to hold it during dispatches because our reference on the * GSettings will prevent the finalize from running and dropping the * ref on the context. * * All access to the list holds a mutex. We have some strategies to * avoid some of the pain that would be associated with that. */ watch = g_slice_new (GSettingsBackendWatch); watch->context = context; watch->target = target; g_object_weak_ref (target, g_settings_backend_watch_weak_notify, backend); watch->changed = changed; watch->path_changed = path_changed; watch->keys_changed = keys_changed; watch->writable_changed = writable_changed; watch->path_writable_changed = path_writable_changed; /* linked list prepend */ g_static_mutex_lock (&backend->priv->lock); watch->next = backend->priv->watches; backend->priv->watches = watch; g_static_mutex_unlock (&backend->priv->lock); } void g_settings_backend_unwatch (GSettingsBackend *backend, GObject *target) { /* Our caller surely owns a reference on 'target', so the order of * these two calls is unimportant. */ g_object_weak_unref (target, g_settings_backend_watch_weak_notify, backend); g_settings_backend_watch_weak_notify (backend, target); } static gboolean g_settings_backend_invoke_closure (gpointer user_data) { GSettingsBackendClosure *closure = user_data; closure->function (closure->backend, closure->target, closure->name, closure->data1, closure->data2); closure->data1_free (closure->data1); g_object_unref (closure->backend); g_object_unref (closure->target); g_free (closure->name); g_slice_free (GSettingsBackendClosure, closure); return FALSE; } static gpointer pointer_id (gpointer a) { return a; } static void pointer_ignore (gpointer a) { } static void g_settings_backend_dispatch_signal (GSettingsBackend *backend, gsize function_offset, const gchar *name, gpointer data1, GBoxedCopyFunc data1_copy, GBoxedFreeFunc data1_free, gpointer data2) { GMainContext *context, *here_and_now; GSettingsBackendWatch *watch; /* We need to hold the mutex here (to prevent a node from being * deleted as we are traversing the list). Since we should not * re-enter user code while holding this mutex, we create a * one-time-use GMainContext and populate it with the events that we * would have called directly. We dispatch these events after * releasing the lock. Note that the GObject reference is acquired on * the target while holding the mutex and the mutex needs to be held * as part of the destruction of any GSettings instance (via the weak * reference handling). This is the key to the safety of the whole * setup. */ if (data1_copy == NULL) data1_copy = pointer_id; if (data1_free == NULL) data1_free = pointer_ignore; context = g_settings_backend_get_active_context (); here_and_now = g_main_context_new (); /* traverse the (immutable while holding lock) list */ g_static_mutex_lock (&backend->priv->lock); for (watch = backend->priv->watches; watch; watch = watch->next) { GSettingsBackendClosure *closure; GSource *source; closure = g_slice_new (GSettingsBackendClosure); closure->backend = g_object_ref (backend); closure->target = g_object_ref (watch->target); closure->function = G_STRUCT_MEMBER (void *, watch, function_offset); closure->name = g_strdup (name); closure->data1 = data1_copy (data1); closure->data1_free = data1_free; closure->data2 = data2; source = g_idle_source_new (); g_source_set_priority (source, G_PRIORITY_DEFAULT); g_source_set_callback (source, g_settings_backend_invoke_closure, closure, NULL); if (watch->context && watch->context != context) g_source_attach (source, watch->context); else g_source_attach (source, here_and_now); g_source_unref (source); } g_static_mutex_unlock (&backend->priv->lock); while (g_main_context_iteration (here_and_now, FALSE)); g_main_context_unref (here_and_now); } /** * g_settings_backend_changed: * @backend: a #GSettingsBackend implementation * @key: the name of the key * @origin_tag: the origin tag * * Signals that a single key has possibly changed. Backend * implementations should call this if a key has possibly changed its * value. * * @key must be a valid key (ie: starting with a slash, not containing * '//', and not ending with a slash). * * The implementation must call this function during any call to * g_settings_backend_write(), before the call returns (except in the * case that no keys are actually changed and it cares to detect this * fact). It may not rely on the existence of a mainloop for * dispatching the signal later. * * The implementation may call this function at any other time it likes * in response to other events (such as changes occuring outside of the * program). These calls may originate from a mainloop or may originate * in response to any other action (including from calls to * g_settings_backend_write()). * * In the case that this call is in response to a call to * g_settings_backend_write() then @origin_tag must be set to the same * value that was passed to that call. * * Since: 2.26 **/ void g_settings_backend_changed (GSettingsBackend *backend, const gchar *key, gpointer origin_tag) { g_return_if_fail (G_IS_SETTINGS_BACKEND (backend)); g_return_if_fail (is_key (key)); g_settings_backend_dispatch_signal (backend, G_STRUCT_OFFSET (GSettingsBackendWatch, changed), key, origin_tag, NULL, NULL, NULL); } /** * g_settings_backend_keys_changed: * @backend: a #GSettingsBackend implementation * @path: the path containing the changes * @items: the %NULL-terminated list of changed keys * @origin_tag: the origin tag * * Signals that a list of keys have possibly changed. Backend * implementations should call this if keys have possibly changed their * values. * * @path must be a valid path (ie: starting and ending with a slash and * not containing '//'). Each string in @items must form a valid key * name when @path is prefixed to it (ie: each item must not start or * end with '/' and must not contain '//'). * * The meaning of this signal is that any of the key names resulting * from the contatenation of @path with each item in @items may have * changed. * * The same rules for when notifications must occur apply as per * g_settings_backend_changed(). These two calls can be used * interchangeably if exactly one item has changed (although in that * case g_settings_backend_changed() is definitely preferred). * * For efficiency reasons, the implementation should strive for @path to * be as long as possible (ie: the longest common prefix of all of the * keys that were changed) but this is not strictly required. * * Since: 2.26 */ void g_settings_backend_keys_changed (GSettingsBackend *backend, const gchar *path, gchar const * const *items, gpointer origin_tag) { g_return_if_fail (G_IS_SETTINGS_BACKEND (backend)); g_return_if_fail (is_path (path)); /* XXX: should do stricter checking (ie: inspect each item) */ g_return_if_fail (items != NULL); g_settings_backend_dispatch_signal (backend, G_STRUCT_OFFSET (GSettingsBackendWatch, keys_changed), path, (gpointer) items, (GBoxedCopyFunc) g_strdupv, (GBoxedFreeFunc) g_strfreev, origin_tag); } /** * g_settings_backend_path_changed: * @backend: a #GSettingsBackend implementation * @path: the path containing the changes * @origin_tag: the origin tag * * Signals that all keys below a given path may have possibly changed. * Backend implementations should call this if an entire path of keys * have possibly changed their values. * * @path must be a valid path (ie: starting and ending with a slash and * not containing '//'). * * The meaning of this signal is that any of the key which has a name * starting with @path may have changed. * * The same rules for when notifications must occur apply as per * g_settings_backend_changed(). This call might be an appropriate * reasponse to a 'reset' call but implementations are also free to * explicitly list the keys that were affected by that call if they can * easily do so. * * For efficiency reasons, the implementation should strive for @path to * be as long as possible (ie: the longest common prefix of all of the * keys that were changed) but this is not strictly required. As an * example, if this function is called with the path of "/" then every * single key in the application will be notified of a possible change. * * Since: 2.26 */ void g_settings_backend_path_changed (GSettingsBackend *backend, const gchar *path, gpointer origin_tag) { g_return_if_fail (G_IS_SETTINGS_BACKEND (backend)); g_return_if_fail (is_path (path)); g_settings_backend_dispatch_signal (backend, G_STRUCT_OFFSET (GSettingsBackendWatch, path_changed), path, origin_tag, NULL, NULL, NULL); } /** * g_settings_backend_writable_changed: * @backend: a #GSettingsBackend implementation * @key: the name of the key * * Signals that the writability of a single key has possibly changed. * * Since GSettings performs no locking operations for itself, this call * will always be made in response to external events. * * Since: 2.26 **/ void g_settings_backend_writable_changed (GSettingsBackend *backend, const gchar *key) { g_return_if_fail (G_IS_SETTINGS_BACKEND (backend)); g_return_if_fail (is_key (key)); g_settings_backend_dispatch_signal (backend, G_STRUCT_OFFSET (GSettingsBackendWatch, writable_changed), key, NULL, NULL, NULL, NULL); } /** * g_settings_backend_path_writable_changed: * @backend: a #GSettingsBackend implementation * @path: the name of the path * * Signals that the writability of all keys below a given path may have * changed. * * Since GSettings performs no locking operations for itself, this call * will always be made in response to external events. * * Since: 2.26 **/ void g_settings_backend_path_writable_changed (GSettingsBackend *backend, const gchar *path) { g_return_if_fail (G_IS_SETTINGS_BACKEND (backend)); g_return_if_fail (is_path (path)); g_settings_backend_dispatch_signal (backend, G_STRUCT_OFFSET (GSettingsBackendWatch, path_writable_changed), path, NULL, NULL, NULL, NULL); } typedef struct { const gchar **keys; GVariant **values; gint prefix_len; gchar *prefix; } FlattenState; static gboolean g_settings_backend_flatten_one (gpointer key, gpointer value, gpointer user_data) { FlattenState *state = user_data; const gchar *skey = key; gint i; g_return_val_if_fail (is_key (key), TRUE); /* calculate longest common prefix */ if (state->prefix == NULL) { gchar *last_byte; /* first key? just take the prefix up to the last '/' */ state->prefix = g_strdup (skey); last_byte = strrchr (state->prefix, '/') + 1; state->prefix_len = last_byte - state->prefix; *last_byte = '\0'; } else { /* find the first character that does not match. we will * definitely find one because the prefix ends in '/' and the key * does not. also: no two keys in the tree are the same. */ for (i = 0; state->prefix[i] == skey[i]; i++); /* check if we need to shorten the prefix */ if (state->prefix[i] != '\0') { /* find the nearest '/', terminate after it */ while (state->prefix[i - 1] != '/') i--; state->prefix[i] = '\0'; state->prefix_len = i; } } /* save the entire item into the array. * the prefixes will be removed later. */ *state->keys++ = key; if (state->values) *state->values++ = value; return FALSE; } /** * g_settings_backend_flatten_tree: * @tree: a #GTree containing the changes * @path: the location to save the path * @keys: the location to save the relative keys * @values: the location to save the values, or %NULL * * Calculate the longest common prefix of all keys in a tree and write * out an array of the key names relative to that prefix and, * optionally, the value to store at each of those keys. * * You must free the value returned in @path, @keys and @values using * g_free(). You should not attempt to free or unref the contents of * @keys or @values. * * Since: 2.26 **/ void g_settings_backend_flatten_tree (GTree *tree, gchar **path, const gchar ***keys, GVariant ***values) { FlattenState state = { 0, }; gsize nnodes; nnodes = g_tree_nnodes (tree); *keys = state.keys = g_new (const gchar *, nnodes + 1); state.keys[nnodes] = NULL; if (values != NULL) { *values = state.values = g_new (GVariant *, nnodes + 1); state.values[nnodes] = NULL; } g_tree_foreach (tree, g_settings_backend_flatten_one, &state); g_return_if_fail (*keys + nnodes == state.keys); *path = state.prefix; while (nnodes--) *--state.keys += state.prefix_len; } /** * g_settings_backend_changed_tree: * @backend: a #GSettingsBackend implementation * @tree: a #GTree containing the changes * @origin_tag: the origin tag * * This call is a convenience wrapper. It gets the list of changes from * @tree, computes the longest common prefix and calls * g_settings_backend_changed(). * * Since: 2.26 **/ void g_settings_backend_changed_tree (GSettingsBackend *backend, GTree *tree, gpointer origin_tag) { GSettingsBackendWatch *watch; const gchar **keys; gchar *path; g_return_if_fail (G_IS_SETTINGS_BACKEND (backend)); g_settings_backend_flatten_tree (tree, &path, &keys, NULL); for (watch = backend->priv->watches; watch; watch = watch->next) watch->keys_changed (backend, watch->target, path, keys, origin_tag); g_free (path); g_free (keys); } /*< private > * g_settings_backend_read: * @backend: a #GSettingsBackend implementation * @key: the key to read * @expected_type: a #GVariantType hint * @returns: the value that was read, or %NULL * * Reads a key. This call will never block. * * If the key exists, the value associated with it will be returned. * If the key does not exist, %NULL will be returned. * * If @expected_type is given, it serves as a type hint to the backend. * If you expect a key of a certain type then you should give * @expected_type to increase your chances of getting it. Some backends * may ignore this argument and return values of a different type; it is * mostly used by backends that don't store strong type information. */ GVariant * g_settings_backend_read (GSettingsBackend *backend, const gchar *key, const GVariantType *expected_type, gboolean default_value) { return G_SETTINGS_BACKEND_GET_CLASS (backend) ->read (backend, key, expected_type, default_value); } /*< private > * g_settings_backend_write: * @backend: a #GSettingsBackend implementation * @key: the name of the key * @value: a #GVariant value to write to this key * @origin_tag: the origin tag * @returns: %TRUE if the write succeeded, %FALSE if the key was not writable * * Writes exactly one key. * * This call does not fail. During this call a * #GSettingsBackend::changed signal will be emitted if the value of the * key has changed. The updated key value will be visible to any signal * callbacks. * * One possible method that an implementation might deal with failures is * to emit a second "changed" signal (either during this call, or later) * to indicate that the affected keys have suddenly "changed back" to their * old values. */ gboolean g_settings_backend_write (GSettingsBackend *backend, const gchar *key, GVariant *value, gpointer origin_tag) { return G_SETTINGS_BACKEND_GET_CLASS (backend) ->write (backend, key, value, origin_tag); } /*< private > * g_settings_backend_write_keys: * @backend: a #GSettingsBackend implementation * @values: a #GTree containing key-value pairs to write * @origin_tag: the origin tag * * Writes one or more keys. This call will never block. * * The key of each item in the tree is the key name to write to and the * value is a #GVariant to write. The proper type of #GTree for this * call can be created with g_settings_backend_create_tree(). This call * might take a reference to the tree; you must not modified the #GTree * after passing it to this call. * * This call does not fail. During this call a #GSettingsBackend::changed * signal will be emitted if any keys have been changed. The new values of * all updated keys will be visible to any signal callbacks. * * One possible method that an implementation might deal with failures is * to emit a second "changed" signal (either during this call, or later) * to indicate that the affected keys have suddenly "changed back" to their * old values. */ gboolean g_settings_backend_write_keys (GSettingsBackend *backend, GTree *tree, gpointer origin_tag) { return G_SETTINGS_BACKEND_GET_CLASS (backend) ->write_keys (backend, tree, origin_tag); } /*< private > * g_settings_backend_reset: * @backend: a #GSettingsBackend implementation * @key: the name of a key * @origin_tag: the origin tag * * "Resets" the named key to its "default" value (ie: after system-wide * defaults, mandatory keys, etc. have been taken into account) or possibly * unsets it. */ void g_settings_backend_reset (GSettingsBackend *backend, const gchar *key, gpointer origin_tag) { G_SETTINGS_BACKEND_GET_CLASS (backend) ->reset (backend, key, origin_tag); } /*< private > * g_settings_backend_reset_path: * @backend: a #GSettingsBackend implementation * @name: the name of a key or path * @origin_tag: the origin tag * * "Resets" the named path. This means that every key under the path is * reset. */ void g_settings_backend_reset_path (GSettingsBackend *backend, const gchar *path, gpointer origin_tag) { G_SETTINGS_BACKEND_GET_CLASS (backend) ->reset_path (backend, path, origin_tag); } /*< private > * g_settings_backend_get_writable: * @backend: a #GSettingsBackend implementation * @key: the name of a key * @returns: %TRUE if the key is writable * * Finds out if a key is available for writing to. This is the * interface through which 'lockdown' is implemented. Locked down * keys will have %FALSE returned by this call. * * You should not write to locked-down keys, but if you do, the * implementation will deal with it. */ gboolean g_settings_backend_get_writable (GSettingsBackend *backend, const gchar *key) { return G_SETTINGS_BACKEND_GET_CLASS (backend) ->get_writable (backend, key); } /*< private > * g_settings_backend_unsubscribe: * @backend: a #GSettingsBackend * @name: a key or path to subscribe to * * Reverses the effect of a previous call to * g_settings_backend_subscribe(). */ void g_settings_backend_unsubscribe (GSettingsBackend *backend, const char *name) { G_SETTINGS_BACKEND_GET_CLASS (backend) ->unsubscribe (backend, name); } /*< private > * g_settings_backend_subscribe: * @backend: a #GSettingsBackend * @name: a key or path to subscribe to * * Requests that change signals be emitted for events on @name. */ void g_settings_backend_subscribe (GSettingsBackend *backend, const gchar *name) { G_SETTINGS_BACKEND_GET_CLASS (backend) ->subscribe (backend, name); } static void g_settings_backend_set_property (GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec) { GSettingsBackend *backend = G_SETTINGS_BACKEND (object); switch (prop_id) { case PROP_CONTEXT: backend->priv->context = g_value_dup_string (value); break; default: G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec); break; } } static void g_settings_backend_get_property (GObject *object, guint prop_id, GValue *value, GParamSpec *pspec) { GSettingsBackend *backend = G_SETTINGS_BACKEND (object); switch (prop_id) { case PROP_CONTEXT: g_value_set_string (value, backend->priv->context); break; default: G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec); break; } } static void g_settings_backend_finalize (GObject *object) { GSettingsBackend *backend = G_SETTINGS_BACKEND (object); g_static_mutex_unlock (&backend->priv->lock); g_free (backend->priv->context); G_OBJECT_CLASS (g_settings_backend_parent_class) ->finalize (object); } static void ignore_subscription (GSettingsBackend *backend, const gchar *key) { } static void g_settings_backend_init (GSettingsBackend *backend) { backend->priv = G_TYPE_INSTANCE_GET_PRIVATE (backend, G_TYPE_SETTINGS_BACKEND, GSettingsBackendPrivate); g_static_mutex_init (&backend->priv->lock); } static void g_settings_backend_class_init (GSettingsBackendClass *class) { GObjectClass *gobject_class = G_OBJECT_CLASS (class); class->subscribe = ignore_subscription; class->unsubscribe = ignore_subscription; gobject_class->get_property = g_settings_backend_get_property; gobject_class->set_property = g_settings_backend_set_property; gobject_class->finalize = g_settings_backend_finalize; g_type_class_add_private (class, sizeof (GSettingsBackendPrivate)); /** * GSettingsBackend:context: * * The "context" property gives a hint to the backend as to * what storage to use. It is up to the implementation to make * use of this information. * * E.g. DConf supports "user", "system", "defaults" and "login" * contexts. * * If your backend supports different contexts, you should also * provide an implementation of the supports_context() class * function in #GSettingsBackendClass. */ g_object_class_install_property (gobject_class, PROP_CONTEXT, g_param_spec_string ("context", P_("Context"), P_("An identifier to decide which storage to use"), "", G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY | G_PARAM_STATIC_STRINGS)); } /*< private > * g_settings_backend_create_tree: * @returns: a new #GTree * * This is a convenience function for creating a tree that is compatible * with g_settings_backend_write(). It merely calls g_tree_new_full() * with strcmp(), g_free() and g_variant_unref(). */ GTree * g_settings_backend_create_tree (void) { return g_tree_new_full ((GCompareDataFunc) strcmp, NULL, g_free, (GDestroyNotify) g_variant_unref); } static gpointer get_default_backend (const gchar *context) { GIOExtension *extension = NULL; GIOExtensionPoint *point; GList *extensions; const gchar *env; GType type; _g_io_modules_ensure_loaded (); point = g_io_extension_point_lookup (G_SETTINGS_BACKEND_EXTENSION_POINT_NAME); if ((env = getenv ("GSETTINGS_BACKEND"))) { extension = g_io_extension_point_get_extension_by_name (point, env); if (extension == NULL) g_warning ("Can't find GSettings backend '%s' given in " "GSETTINGS_BACKEND environment variable", env); } if (extension == NULL) { extensions = g_io_extension_point_get_extensions (point); if (extensions == NULL) g_error ("No GSettingsBackend implementations exist."); extension = extensions->data; } if (context[0] != '\0') /* (context != "") */ { GSettingsBackendClass *backend_class; GTypeClass *class; class = g_io_extension_ref_class (extension); backend_class = G_SETTINGS_BACKEND_CLASS (class); if (backend_class->supports_context == NULL || !backend_class->supports_context (context)) { g_type_class_unref (class); return NULL; } g_type_class_unref (class); } type = g_io_extension_get_type (extension); return g_object_new (type, "context", context, NULL); } static GHashTable *g_settings_backends; /*< private > * g_settings_backend_get_with_context: * @context: a context that might be used by the backend to determine * which storage to use, or %NULL to use the default storage * @returns: the default #GSettingsBackend * * Returns the default #GSettingsBackend. It is possible to override * the default by setting the GSETTINGS_BACKEND * environment variable to the name of a settings backend. * * The @context parameter can be used to indicate that a different * than the default storage is desired. E.g. the DConf backend lets * you use "user", "system", "defaults" and "login" as contexts. * * If @context is not supported by the implementation, this function * returns an instance of the #GSettingsMemoryBackend. * See g_settings_backend_supports_context(), * * The user does not own the return value and it must not be freed. */ GSettingsBackend * g_settings_backend_get_with_context (const gchar *context) { GSettingsBackend *backend; g_return_val_if_fail (context != NULL, NULL); _g_io_modules_ensure_extension_points_registered (); if (g_settings_backends == NULL) g_settings_backends = g_hash_table_new (g_str_hash, g_str_equal); backend = g_hash_table_lookup (g_settings_backends, context); if (!backend) { backend = get_default_backend (context); if (!backend) backend = g_null_settings_backend_new (); g_hash_table_insert (g_settings_backends, g_strdup (context), backend); } return g_object_ref (backend); } /*< private > * g_settings_backend_supports_context: * @context: a context string that might be passed to * g_settings_backend_new_with_context() * @returns: #TRUE if @context is supported * * Determines if the given context is supported by the default * GSettingsBackend implementation. */ gboolean g_settings_backend_supports_context (const gchar *context) { GSettingsBackend *backend; g_return_val_if_fail (context != NULL, FALSE); backend = get_default_backend (context); if (backend) { g_object_unref (backend); return TRUE; } return FALSE; } /** * g_settings_backend_setup: * @context: a context string (not %NULL or "") * @backend: a #GSettingsBackend * * Sets up @backend for use with #GSettings. * * If you create a #GSettings with its context property set to @context * then it will use the backend given to this function. See * g_settings_new_with_context(). * * The backend must be set up before any settings objects are created * for the named context. * * It is not possible to specify a backend for the default context. * * This function takes a reference on @backend and never releases it. * * Since: 2.26 **/ void g_settings_backend_setup (const gchar *context, GSettingsBackend *backend) { g_return_if_fail (context[0] != '\0'); g_return_if_fail (G_IS_SETTINGS_BACKEND (backend)); if (g_settings_backends == NULL) g_settings_backends = g_hash_table_new (g_str_hash, g_str_equal); if (g_hash_table_lookup (g_settings_backends, context)) g_error ("A GSettingsBackend already exists for context '%s'", context); g_hash_table_insert (g_settings_backends, g_strdup (context), g_object_ref (backend)); } #define __G_SETTINGS_BACKEND_C__ #include "gioaliasdef.c"