gio/gdelayedsettingsbackend.c - third_party/glib - Git at Google

 /*
  * Copyright © 2009, 2010 Codethink Limited
  *
  * 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 2.1 of the License, 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, see <http://www.gnu.org/licenses/>.
  *
  * Author: Ryan Lortie <desrt@desrt.ca>
  */

 #include "config.h"

 #include "gdelayedsettingsbackend.h"
 #include "gsettingsbackendinternal.h"

 #include <string.h>


 struct _GDelayedSettingsBackendPrivate
 {
   GSettingsBackend *backend;
   GMutex lock;
   GTree *delayed;

   GMainContext *owner_context;
   gpointer owner;
 };

 G_DEFINE_TYPE_WITH_PRIVATE (GDelayedSettingsBackend,
                             g_delayed_settings_backend,
                             G_TYPE_SETTINGS_BACKEND)

 static gboolean
 invoke_notify_unapplied (gpointer data)
 {
   g_object_notify (data, "has-unapplied");
   g_object_unref (data);

   return FALSE;
 }

 static void
 g_delayed_settings_backend_notify_unapplied (GDelayedSettingsBackend *delayed)
 {
   GMainContext *target_context;
   GObject *target;

   g_mutex_lock (&delayed->priv->lock);
   if (delayed->priv->owner)
     {
       target_context = delayed->priv->owner_context;
       target = g_object_ref (delayed->priv->owner);
     }
   else
     {
       target_context = NULL;
       target = NULL;
     }
   g_mutex_unlock (&delayed->priv->lock);

   if (target != NULL)
     g_main_context_invoke (target_context, invoke_notify_unapplied, target);
 }


 static GVariant *
 g_delayed_settings_backend_read (GSettingsBackend   *backend,
                                  const gchar        *key,
                                  const GVariantType *expected_type,
                                  gboolean            default_value)
 {
   GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (backend);
   gpointer result = NULL;

   if (!default_value)
     {
       g_mutex_lock (&delayed->priv->lock);
       if (g_tree_lookup_extended (delayed->priv->delayed, key, NULL, &result))
         {
           /* NULL in the tree means we should consult the default value */
           if (result != NULL)
             g_variant_ref (result);
           else
             default_value = TRUE;
         }
       g_mutex_unlock (&delayed->priv->lock);
     }

   if (result == NULL)
     result = g_settings_backend_read (delayed->priv->backend, key,
                                       expected_type, default_value);

   return result;
 }

 static GVariant *
 g_delayed_settings_backend_read_user_value (GSettingsBackend   *backend,
                                             const gchar        *key,
                                             const GVariantType *expected_type)
 {
   GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (backend);
   gboolean value_found = FALSE;
   gpointer result = NULL;

   /* If we find an explicit NULL in our changeset then we want to return
    * NULL (because the user value has been reset).
    *
    * Otherwise, chain up.
    */
   g_mutex_lock (&delayed->priv->lock);
   value_found = g_tree_lookup_extended (delayed->priv->delayed, key, NULL, &result);
   if (result)
     g_variant_ref (result);
   g_mutex_unlock (&delayed->priv->lock);

   if (value_found)
     return result;

   return g_settings_backend_read_user_value (delayed->priv->backend, key, expected_type);
 }

 static gboolean
 g_delayed_settings_backend_write (GSettingsBackend *backend,
                                   const gchar      *key,
                                   GVariant         *value,
                                   gpointer          origin_tag)
 {
   GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (backend);
   gboolean was_empty;

   g_mutex_lock (&delayed->priv->lock);
   was_empty = g_tree_nnodes (delayed->priv->delayed) == 0;
   g_tree_insert (delayed->priv->delayed, g_strdup (key),
                  g_variant_ref_sink (value));
   g_mutex_unlock (&delayed->priv->lock);

   g_settings_backend_changed (backend, key, origin_tag);

   if (was_empty)
     g_delayed_settings_backend_notify_unapplied (delayed);

   return TRUE;
 }

 static gboolean
 add_to_tree (gpointer key,
              gpointer value,
              gpointer user_data)
 {
   g_tree_insert (user_data, g_strdup (key), g_variant_ref (value));
   return FALSE;
 }

 static gboolean
 g_delayed_settings_backend_write_tree (GSettingsBackend *backend,
                                        GTree            *tree,
                                        gpointer          origin_tag)
 {
   GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (backend);
   gboolean was_empty;

   g_mutex_lock (&delayed->priv->lock);
   was_empty = g_tree_nnodes (delayed->priv->delayed) == 0;

   g_tree_foreach (tree, add_to_tree, delayed->priv->delayed);
   g_mutex_unlock (&delayed->priv->lock);

   g_settings_backend_changed_tree (backend, tree, origin_tag);

   if (was_empty)
     g_delayed_settings_backend_notify_unapplied (delayed);

   return TRUE;
 }

 static gboolean
 g_delayed_settings_backend_get_writable (GSettingsBackend *backend,
                                          const gchar      *name)
 {
   GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (backend);

   return g_settings_backend_get_writable (delayed->priv->backend, name);
 }

 static void
 g_delayed_settings_backend_reset (GSettingsBackend *backend,
                                   const gchar      *key,
                                   gpointer          origin_tag)
 {
   GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (backend);
   gboolean was_empty;

   g_mutex_lock (&delayed->priv->lock);
   was_empty = g_tree_nnodes (delayed->priv->delayed) == 0;
   g_tree_insert (delayed->priv->delayed, g_strdup (key), NULL);
   g_mutex_unlock (&delayed->priv->lock);

   if (was_empty)
     g_delayed_settings_backend_notify_unapplied (delayed);
 }

 static void
 g_delayed_settings_backend_subscribe (GSettingsBackend *backend,
                                       const char       *name)
 {
   GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (backend);

   g_settings_backend_subscribe (delayed->priv->backend, name);
 }

 static void
 g_delayed_settings_backend_unsubscribe (GSettingsBackend *backend,
                                         const char       *name)
 {
   GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (backend);

   g_settings_backend_unsubscribe (delayed->priv->backend, name);
 }

 static GPermission *
 g_delayed_settings_backend_get_permission (GSettingsBackend *backend,
                                            const gchar      *path)
 {
   GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (backend);

   return g_settings_backend_get_permission (delayed->priv->backend, path);
 }


 /* method calls */
 gboolean
 g_delayed_settings_backend_get_has_unapplied (GDelayedSettingsBackend *delayed)
 {
   /* we don't need to lock for this... */

   return g_tree_nnodes (delayed->priv->delayed) > 0;
 }

 void
 g_delayed_settings_backend_apply (GDelayedSettingsBackend *delayed)
 {
   if (g_tree_nnodes (delayed->priv->delayed) > 0)
     {
       gboolean success;
       GTree *tmp;

       g_mutex_lock (&delayed->priv->lock);
       tmp = delayed->priv->delayed;
       delayed->priv->delayed = g_settings_backend_create_tree ();
       success = g_settings_backend_write_tree (delayed->priv->backend,
                                                tmp, delayed->priv);
       g_mutex_unlock (&delayed->priv->lock);

       if (!success)
         g_settings_backend_changed_tree (G_SETTINGS_BACKEND (delayed),
                                          tmp, NULL);

       g_tree_unref (tmp);

       g_delayed_settings_backend_notify_unapplied (delayed);
     }
 }

 void
 g_delayed_settings_backend_revert (GDelayedSettingsBackend *delayed)
 {
   if (g_tree_nnodes (delayed->priv->delayed) > 0)
     {
       GTree *tmp;

       g_mutex_lock (&delayed->priv->lock);
       tmp = delayed->priv->delayed;
       delayed->priv->delayed = g_settings_backend_create_tree ();
       g_mutex_unlock (&delayed->priv->lock);
       g_settings_backend_changed_tree (G_SETTINGS_BACKEND (delayed), tmp, NULL);
       g_tree_unref (tmp);

       g_delayed_settings_backend_notify_unapplied (delayed);
     }
 }

 /* change notification */
 static void
 delayed_backend_changed (GObject          *target,
                          GSettingsBackend *backend,
                          const gchar      *key,
                          gpointer          origin_tag)
 {
   GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (target);

   if (origin_tag != delayed->priv)
     g_settings_backend_changed (G_SETTINGS_BACKEND (delayed),
                                 key, origin_tag);
 }

 static void
 delayed_backend_keys_changed (GObject             *target,
                               GSettingsBackend    *backend,
                               const gchar         *path,
                               gpointer             origin_tag,
                               const gchar * const *items)
 {
   GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (target);

   if (origin_tag != delayed->priv)
     g_settings_backend_keys_changed (G_SETTINGS_BACKEND (delayed),
                                      path, items, origin_tag);
 }

 static void
 delayed_backend_path_changed (GObject          *target,
                               GSettingsBackend *backend,
                               const gchar      *path,
                               gpointer          origin_tag)
 {
   GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (target);

   if (origin_tag != delayed->priv)
     g_settings_backend_path_changed (G_SETTINGS_BACKEND (delayed),
                                      path, origin_tag);
 }

 static void
 delayed_backend_writable_changed (GObject          *target,
                                   GSettingsBackend *backend,
                                   const gchar      *key)
 {
   GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (target);
   gboolean last_one = FALSE;

   g_mutex_lock (&delayed->priv->lock);

   if (g_tree_lookup (delayed->priv->delayed, key) != NULL &&
       !g_settings_backend_get_writable (delayed->priv->backend, key))
     {
       /* drop the key from our changeset if it just became read-only.
        * no need to signal since the writable change below implies it.
        *
        * note that the item in the tree may very well be set to NULL in
        * the case that the user stored a reset.  we intentionally don't
        * drop the key in this case since a reset will always succeed
        * (even against a non-writable key).
        */
       g_tree_remove (delayed->priv->delayed, key);

       /* if that was the only key... */
       last_one = g_tree_nnodes (delayed->priv->delayed) == 0;
     }

   g_mutex_unlock (&delayed->priv->lock);

   if (last_one)
     g_delayed_settings_backend_notify_unapplied (delayed);

   g_settings_backend_writable_changed (G_SETTINGS_BACKEND (delayed), key);
 }

 /* slow method until we get foreach-with-remove in GTree
  */
 typedef struct
 {
   const gchar *path;
   const gchar **keys;
   gsize index;
 } CheckPrefixState;

 static gboolean
 check_prefix (gpointer key,
               gpointer value,
               gpointer data)
 {
   CheckPrefixState *state = data;

   if (g_str_has_prefix (key, state->path))
     state->keys[state->index++] = key;

   return FALSE;
 }

 static void
 delayed_backend_path_writable_changed (GObject          *target,
                                        GSettingsBackend *backend,
                                        const gchar      *path)
 {
   GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (target);
   gboolean last_one = FALSE;
   gsize n_keys;

   g_mutex_lock (&delayed->priv->lock);

   n_keys = g_tree_nnodes (delayed->priv->delayed);

   if (n_keys > 0)
     {
       CheckPrefixState state = { path, g_new (const gchar *, n_keys) };
       gsize i;

       /* collect a list of possibly-affected keys (ie: matching the path) */
       g_tree_foreach (delayed->priv->delayed, check_prefix, &state);

       /* drop the keys that have been affected.
        *
        * don't drop 'reset' keys (see above) */
       for (i = 0; i < state.index; i++)
         if (g_tree_lookup (delayed->priv->delayed, state.keys[i]) != NULL &&
             !g_settings_backend_get_writable (delayed->priv->backend,
                                               state.keys[i]))
           g_tree_remove (delayed->priv->delayed, state.keys[i]);

       g_free (state.keys);

       last_one = g_tree_nnodes (delayed->priv->delayed) == 0;
     }

   g_mutex_unlock (&delayed->priv->lock);

   if (last_one)
     g_delayed_settings_backend_notify_unapplied (delayed);

   g_settings_backend_path_writable_changed (G_SETTINGS_BACKEND (delayed),
                                             path);
 }

 static void
 g_delayed_settings_backend_finalize (GObject *object)
 {
   GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (object);

   g_mutex_clear (&delayed->priv->lock);
   g_object_unref (delayed->priv->backend);
   g_tree_unref (delayed->priv->delayed);

   /* if our owner is still alive, why are we finalizing? */
   g_assert (delayed->priv->owner == NULL);

   G_OBJECT_CLASS (g_delayed_settings_backend_parent_class)
     ->finalize (object);
 }

 static void
 g_delayed_settings_backend_class_init (GDelayedSettingsBackendClass *class)
 {
   GSettingsBackendClass *backend_class = G_SETTINGS_BACKEND_CLASS (class);
   GObjectClass *object_class = G_OBJECT_CLASS (class);

   backend_class->read = g_delayed_settings_backend_read;
   backend_class->read_user_value = g_delayed_settings_backend_read_user_value;
   backend_class->write = g_delayed_settings_backend_write;
   backend_class->write_tree = g_delayed_settings_backend_write_tree;
   backend_class->reset = g_delayed_settings_backend_reset;
   backend_class->get_writable = g_delayed_settings_backend_get_writable;
   backend_class->subscribe = g_delayed_settings_backend_subscribe;
   backend_class->unsubscribe = g_delayed_settings_backend_unsubscribe;
   backend_class->get_permission = g_delayed_settings_backend_get_permission;

   object_class->finalize = g_delayed_settings_backend_finalize;
 }

 static void
 g_delayed_settings_backend_init (GDelayedSettingsBackend *delayed)
 {
   delayed->priv = g_delayed_settings_backend_get_instance_private (delayed);
   delayed->priv->delayed = g_settings_backend_create_tree ();
   g_mutex_init (&delayed->priv->lock);
 }

 static void
 g_delayed_settings_backend_disown (gpointer  data,
                                    GObject  *where_the_object_was)
 {
   GDelayedSettingsBackend *delayed = data;

   g_mutex_lock (&delayed->priv->lock);
   delayed->priv->owner_context = NULL;
   delayed->priv->owner = NULL;
   g_mutex_unlock (&delayed->priv->lock);
 }

 GDelayedSettingsBackend *
 g_delayed_settings_backend_new (GSettingsBackend *backend,
                                 gpointer          owner,
                                 GMainContext     *owner_context)
 {
   static GSettingsListenerVTable vtable = {
     delayed_backend_changed,
     delayed_backend_path_changed,
     delayed_backend_keys_changed,
     delayed_backend_writable_changed,
     delayed_backend_path_writable_changed
   };
   GDelayedSettingsBackend *delayed;

   delayed = g_object_new (G_TYPE_DELAYED_SETTINGS_BACKEND, NULL);
   delayed->priv->backend = g_object_ref (backend);
   delayed->priv->owner_context = owner_context;
   delayed->priv->owner = owner;

   g_object_weak_ref (owner, g_delayed_settings_backend_disown, delayed);

   g_settings_backend_watch (delayed->priv->backend,
                             &vtable, G_OBJECT (delayed), NULL);

   return delayed;
 }
	/*
	* Copyright © 2009, 2010 Codethink Limited
	*
	* 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 2.1 of the License, 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, see <http://www.gnu.org/licenses/>.
	*
	* Author: Ryan Lortie <desrt@desrt.ca>
	*/

	#include "config.h"

	#include "gdelayedsettingsbackend.h"
	#include "gsettingsbackendinternal.h"

	#include <string.h>


	struct _GDelayedSettingsBackendPrivate
	{
	GSettingsBackend *backend;
	GMutex lock;
	GTree *delayed;

	GMainContext *owner_context;
	gpointer owner;
	};

	G_DEFINE_TYPE_WITH_PRIVATE (GDelayedSettingsBackend,
	g_delayed_settings_backend,
	G_TYPE_SETTINGS_BACKEND)

	static gboolean
	invoke_notify_unapplied (gpointer data)
	{
	g_object_notify (data, "has-unapplied");
	g_object_unref (data);

	return FALSE;
	}

	static void
	g_delayed_settings_backend_notify_unapplied (GDelayedSettingsBackend *delayed)
	{
	GMainContext *target_context;
	GObject *target;

	g_mutex_lock (&delayed->priv->lock);
	if (delayed->priv->owner)
	{
	target_context = delayed->priv->owner_context;
	target = g_object_ref (delayed->priv->owner);
	}
	else
	{
	target_context = NULL;
	target = NULL;
	}
	g_mutex_unlock (&delayed->priv->lock);

	if (target != NULL)
	g_main_context_invoke (target_context, invoke_notify_unapplied, target);
	}


	static GVariant *
	g_delayed_settings_backend_read (GSettingsBackend *backend,
	const gchar *key,
	const GVariantType *expected_type,
	gboolean default_value)
	{
	GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (backend);
	gpointer result = NULL;

	if (!default_value)
	{
	g_mutex_lock (&delayed->priv->lock);
	if (g_tree_lookup_extended (delayed->priv->delayed, key, NULL, &result))
	{
	/* NULL in the tree means we should consult the default value */
	if (result != NULL)
	g_variant_ref (result);
	else
	default_value = TRUE;
	}
	g_mutex_unlock (&delayed->priv->lock);
	}

	if (result == NULL)
	result = g_settings_backend_read (delayed->priv->backend, key,
	expected_type, default_value);

	return result;
	}

	static GVariant *
	g_delayed_settings_backend_read_user_value (GSettingsBackend *backend,
	const gchar *key,
	const GVariantType *expected_type)
	{
	GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (backend);
	gboolean value_found = FALSE;
	gpointer result = NULL;

	/* If we find an explicit NULL in our changeset then we want to return
	* NULL (because the user value has been reset).
	*
	* Otherwise, chain up.
	*/
	g_mutex_lock (&delayed->priv->lock);
	value_found = g_tree_lookup_extended (delayed->priv->delayed, key, NULL, &result);
	if (result)
	g_variant_ref (result);
	g_mutex_unlock (&delayed->priv->lock);

	if (value_found)
	return result;

	return g_settings_backend_read_user_value (delayed->priv->backend, key, expected_type);
	}

	static gboolean
	g_delayed_settings_backend_write (GSettingsBackend *backend,
	const gchar *key,
	GVariant *value,
	gpointer origin_tag)
	{
	GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (backend);
	gboolean was_empty;

	g_mutex_lock (&delayed->priv->lock);
	was_empty = g_tree_nnodes (delayed->priv->delayed) == 0;
	g_tree_insert (delayed->priv->delayed, g_strdup (key),
	g_variant_ref_sink (value));
	g_mutex_unlock (&delayed->priv->lock);

	g_settings_backend_changed (backend, key, origin_tag);

	if (was_empty)
	g_delayed_settings_backend_notify_unapplied (delayed);

	return TRUE;
	}

	static gboolean
	add_to_tree (gpointer key,
	gpointer value,
	gpointer user_data)
	{
	g_tree_insert (user_data, g_strdup (key), g_variant_ref (value));
	return FALSE;
	}

	static gboolean
	g_delayed_settings_backend_write_tree (GSettingsBackend *backend,
	GTree *tree,
	gpointer origin_tag)
	{
	GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (backend);
	gboolean was_empty;

	g_mutex_lock (&delayed->priv->lock);
	was_empty = g_tree_nnodes (delayed->priv->delayed) == 0;

	g_tree_foreach (tree, add_to_tree, delayed->priv->delayed);
	g_mutex_unlock (&delayed->priv->lock);

	g_settings_backend_changed_tree (backend, tree, origin_tag);

	if (was_empty)
	g_delayed_settings_backend_notify_unapplied (delayed);

	return TRUE;
	}

	static gboolean
	g_delayed_settings_backend_get_writable (GSettingsBackend *backend,
	const gchar *name)
	{
	GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (backend);

	return g_settings_backend_get_writable (delayed->priv->backend, name);
	}

	static void
	g_delayed_settings_backend_reset (GSettingsBackend *backend,
	const gchar *key,
	gpointer origin_tag)
	{
	GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (backend);
	gboolean was_empty;

	g_mutex_lock (&delayed->priv->lock);
	was_empty = g_tree_nnodes (delayed->priv->delayed) == 0;
	g_tree_insert (delayed->priv->delayed, g_strdup (key), NULL);
	g_mutex_unlock (&delayed->priv->lock);

	if (was_empty)
	g_delayed_settings_backend_notify_unapplied (delayed);
	}

	static void
	g_delayed_settings_backend_subscribe (GSettingsBackend *backend,
	const char *name)
	{
	GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (backend);

	g_settings_backend_subscribe (delayed->priv->backend, name);
	}

	static void
	g_delayed_settings_backend_unsubscribe (GSettingsBackend *backend,
	const char *name)
	{
	GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (backend);

	g_settings_backend_unsubscribe (delayed->priv->backend, name);
	}

	static GPermission *
	g_delayed_settings_backend_get_permission (GSettingsBackend *backend,
	const gchar *path)
	{
	GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (backend);

	return g_settings_backend_get_permission (delayed->priv->backend, path);
	}


	/* method calls */
	gboolean
	g_delayed_settings_backend_get_has_unapplied (GDelayedSettingsBackend *delayed)
	{
	/* we don't need to lock for this... */

	return g_tree_nnodes (delayed->priv->delayed) > 0;
	}

	void
	g_delayed_settings_backend_apply (GDelayedSettingsBackend *delayed)
	{
	if (g_tree_nnodes (delayed->priv->delayed) > 0)
	{
	gboolean success;
	GTree *tmp;

	g_mutex_lock (&delayed->priv->lock);
	tmp = delayed->priv->delayed;
	delayed->priv->delayed = g_settings_backend_create_tree ();
	success = g_settings_backend_write_tree (delayed->priv->backend,
	tmp, delayed->priv);
	g_mutex_unlock (&delayed->priv->lock);

	if (!success)
	g_settings_backend_changed_tree (G_SETTINGS_BACKEND (delayed),
	tmp, NULL);

	g_tree_unref (tmp);

	g_delayed_settings_backend_notify_unapplied (delayed);
	}
	}

	void
	g_delayed_settings_backend_revert (GDelayedSettingsBackend *delayed)
	{
	if (g_tree_nnodes (delayed->priv->delayed) > 0)
	{
	GTree *tmp;

	g_mutex_lock (&delayed->priv->lock);
	tmp = delayed->priv->delayed;
	delayed->priv->delayed = g_settings_backend_create_tree ();
	g_mutex_unlock (&delayed->priv->lock);
	g_settings_backend_changed_tree (G_SETTINGS_BACKEND (delayed), tmp, NULL);
	g_tree_unref (tmp);

	g_delayed_settings_backend_notify_unapplied (delayed);
	}
	}

	/* change notification */
	static void
	delayed_backend_changed (GObject *target,
	GSettingsBackend *backend,
	const gchar *key,
	gpointer origin_tag)
	{
	GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (target);

	if (origin_tag != delayed->priv)
	g_settings_backend_changed (G_SETTINGS_BACKEND (delayed),
	key, origin_tag);
	}

	static void
	delayed_backend_keys_changed (GObject *target,
	GSettingsBackend *backend,
	const gchar *path,
	gpointer origin_tag,
	const gchar * const *items)
	{
	GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (target);

	if (origin_tag != delayed->priv)
	g_settings_backend_keys_changed (G_SETTINGS_BACKEND (delayed),
	path, items, origin_tag);
	}

	static void
	delayed_backend_path_changed (GObject *target,
	GSettingsBackend *backend,
	const gchar *path,
	gpointer origin_tag)
	{
	GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (target);

	if (origin_tag != delayed->priv)
	g_settings_backend_path_changed (G_SETTINGS_BACKEND (delayed),
	path, origin_tag);
	}

	static void
	delayed_backend_writable_changed (GObject *target,
	GSettingsBackend *backend,
	const gchar *key)
	{
	GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (target);
	gboolean last_one = FALSE;

	g_mutex_lock (&delayed->priv->lock);

	if (g_tree_lookup (delayed->priv->delayed, key) != NULL &&
	!g_settings_backend_get_writable (delayed->priv->backend, key))
	{
	/* drop the key from our changeset if it just became read-only.
	* no need to signal since the writable change below implies it.
	*
	* note that the item in the tree may very well be set to NULL in
	* the case that the user stored a reset. we intentionally don't
	* drop the key in this case since a reset will always succeed
	* (even against a non-writable key).
	*/
	g_tree_remove (delayed->priv->delayed, key);

	/* if that was the only key... */
	last_one = g_tree_nnodes (delayed->priv->delayed) == 0;
	}

	g_mutex_unlock (&delayed->priv->lock);

	if (last_one)
	g_delayed_settings_backend_notify_unapplied (delayed);

	g_settings_backend_writable_changed (G_SETTINGS_BACKEND (delayed), key);
	}

	/* slow method until we get foreach-with-remove in GTree
	*/
	typedef struct
	{
	const gchar *path;
	const gchar **keys;
	gsize index;
	} CheckPrefixState;

	static gboolean
	check_prefix (gpointer key,
	gpointer value,
	gpointer data)
	{
	CheckPrefixState *state = data;

	if (g_str_has_prefix (key, state->path))
	state->keys[state->index++] = key;

	return FALSE;
	}

	static void
	delayed_backend_path_writable_changed (GObject *target,
	GSettingsBackend *backend,
	const gchar *path)
	{
	GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (target);
	gboolean last_one = FALSE;
	gsize n_keys;

	g_mutex_lock (&delayed->priv->lock);

	n_keys = g_tree_nnodes (delayed->priv->delayed);

	if (n_keys > 0)
	{
	CheckPrefixState state = { path, g_new (const gchar *, n_keys) };
	gsize i;

	/* collect a list of possibly-affected keys (ie: matching the path) */
	g_tree_foreach (delayed->priv->delayed, check_prefix, &state);

	/* drop the keys that have been affected.
	*
	* don't drop 'reset' keys (see above) */
	for (i = 0; i < state.index; i++)
	if (g_tree_lookup (delayed->priv->delayed, state.keys[i]) != NULL &&
	!g_settings_backend_get_writable (delayed->priv->backend,
	state.keys[i]))
	g_tree_remove (delayed->priv->delayed, state.keys[i]);

	g_free (state.keys);

	last_one = g_tree_nnodes (delayed->priv->delayed) == 0;
	}

	g_mutex_unlock (&delayed->priv->lock);

	if (last_one)
	g_delayed_settings_backend_notify_unapplied (delayed);

	g_settings_backend_path_writable_changed (G_SETTINGS_BACKEND (delayed),
	path);
	}

	static void
	g_delayed_settings_backend_finalize (GObject *object)
	{
	GDelayedSettingsBackend *delayed = G_DELAYED_SETTINGS_BACKEND (object);

	g_mutex_clear (&delayed->priv->lock);
	g_object_unref (delayed->priv->backend);
	g_tree_unref (delayed->priv->delayed);

	/* if our owner is still alive, why are we finalizing? */
	g_assert (delayed->priv->owner == NULL);

	G_OBJECT_CLASS (g_delayed_settings_backend_parent_class)
	->finalize (object);
	}

	static void
	g_delayed_settings_backend_class_init (GDelayedSettingsBackendClass *class)
	{
	GSettingsBackendClass *backend_class = G_SETTINGS_BACKEND_CLASS (class);
	GObjectClass *object_class = G_OBJECT_CLASS (class);

	backend_class->read = g_delayed_settings_backend_read;
	backend_class->read_user_value = g_delayed_settings_backend_read_user_value;
	backend_class->write = g_delayed_settings_backend_write;
	backend_class->write_tree = g_delayed_settings_backend_write_tree;
	backend_class->reset = g_delayed_settings_backend_reset;
	backend_class->get_writable = g_delayed_settings_backend_get_writable;
	backend_class->subscribe = g_delayed_settings_backend_subscribe;
	backend_class->unsubscribe = g_delayed_settings_backend_unsubscribe;
	backend_class->get_permission = g_delayed_settings_backend_get_permission;

	object_class->finalize = g_delayed_settings_backend_finalize;
	}

	static void
	g_delayed_settings_backend_init (GDelayedSettingsBackend *delayed)
	{
	delayed->priv = g_delayed_settings_backend_get_instance_private (delayed);
	delayed->priv->delayed = g_settings_backend_create_tree ();
	g_mutex_init (&delayed->priv->lock);
	}

	static void
	g_delayed_settings_backend_disown (gpointer data,
	GObject *where_the_object_was)
	{
	GDelayedSettingsBackend *delayed = data;

	g_mutex_lock (&delayed->priv->lock);
	delayed->priv->owner_context = NULL;
	delayed->priv->owner = NULL;
	g_mutex_unlock (&delayed->priv->lock);
	}

	GDelayedSettingsBackend *
	g_delayed_settings_backend_new (GSettingsBackend *backend,
	gpointer owner,
	GMainContext *owner_context)
	{
	static GSettingsListenerVTable vtable = {
	delayed_backend_changed,
	delayed_backend_path_changed,
	delayed_backend_keys_changed,
	delayed_backend_writable_changed,
	delayed_backend_path_writable_changed
	};
	GDelayedSettingsBackend *delayed;

	delayed = g_object_new (G_TYPE_DELAYED_SETTINGS_BACKEND, NULL);
	delayed->priv->backend = g_object_ref (backend);
	delayed->priv->owner_context = owner_context;
	delayed->priv->owner = owner;

	g_object_weak_ref (owner, g_delayed_settings_backend_disown, delayed);

	g_settings_backend_watch (delayed->priv->backend,
	&vtable, G_OBJECT (delayed), NULL);

	return delayed;
	}