Massively reorganise the client-side

This commit represents a rather complete rethinking of DConfEngine.

  - the different kinds of sources are now properly abstracted.  This
    will make landing NFS support substantially easier.

  - there is now substantially more internal documentation

  - DConfEngineMessage is gone and replaced with ordinary function calls
    to be implemented by the D-Bus glue code

  - the GDBus glue has been factored out and is now shared between the
    client library and GSettings

  - the "outstanding" queue logic from the GSettings backend is now in
    the engine

  - all changes now go through a single API that accepts a (new)
    DConfChangeset object.  Currently this only supports the current
    operations (ie: setting and resetting).  In the future this object
    will also support the directory operations required by GSettingsList
    and will be the basis for the new approach to implementing the
    'delayed' GSettingsBackend (which will be the method by which those
    two concepts can co-exist).

The (internal) API of the engine changed substantially.  This caused the
following:

  - the libdconf client library has been rewritten in C.  Most of the
    complicated aspects of it (that made it more convenience to use
    Vala) are now gone.

  - during the rewrite of libdconf, the DConfClient API changed a bit to
    look more like a proper GObject.  It now makes GIO-style use of
    thread-default main contexts and uses GObject signals for
    notifications (instead of hand-rolled callbacks).

  - the GSettings backend has been substantially simplified (the
    "outstanding" logic is gone).  No externally-visible changes.

  - the dbus-1 backend has taken a copy of the old engine code for now
    until it can be ported to the new engine and sufficiently tested.
    No externally-visible changes.

  - the dconf commandline tool and dconf-editor required minor changes
    to adjust to the DConfClient API changes

There is a substantial amount of cleaning up and finishing of work to be
done.  There are many stubs remaining.  There are likely still a large
number of bugs.

2 files changed, 55 insertions, 550 deletions

diff --git a/gsettings/Makefile.am b/gsettings/Makefile.am
index e35926e..7baf7c2 100644
--- a/gsettings/Makefile.am
+++ b/gsettings/Makefile.am
@@ -3,10 +3,9 @@ INCLUDES = -I$(top_srcdir)/common -I$(top_srcdir)/gvdb -I$(top_srcdir)/engine $(
 
 giomodules_PROGRAMS = libdconfsettings.so
 
-libdconfsettings_so_LDADD = $(gio_LIBS) ../common/libdconf-common-shared.a
+libdconfsettings_so_LDADD = $(gio_LIBS) ../engine/libdconf-engine.a ../gdbus/libdconf-gdbus.a
 libdconfsettings_so_LDFLAGS = -shared
 libdconfsettings_so_SOURCES = \
-	../engine/dconf-engine.c	\
 	../gvdb/gvdb-reader.c		\
 	dconfcontext.h			\
 	dconfcontext.c			\
diff --git a/gsettings/dconfsettingsbackend.c b/gsettings/dconfsettingsbackend.c
index cdf0550..85aef4e 100644
--- a/gsettings/dconfsettingsbackend.c
+++ b/gsettings/dconfsettingsbackend.c
@@ -29,411 +29,15 @@
 #include "dconfcontext.h"
 
 typedef GSettingsBackendClass DConfSettingsBackendClass;
-typedef struct _Outstanding Outstanding;
 
 typedef struct
 {
   GSettingsBackend backend;
-
-  GDBusConnection *session_bus;
-  GDBusConnection *system_bus;
-  guint session_subscription;
-  guint system_subscription;
-
-  Outstanding *outstanding;
-  gchar *anti_expose_tag;
-
-  DConfEngine *engine;
-  GMutex lock;
-  GCond sync_cond;
-  gint sync_waiters;
+  DConfEngine     *engine;
 } DConfSettingsBackend;
 
 static GType dconf_settings_backend_get_type (void);
-G_DEFINE_TYPE (DConfSettingsBackend,
-               dconf_settings_backend,
-               G_TYPE_SETTINGS_BACKEND)
-
-static void
-dconf_settings_backend_signal (GDBusConnection *connection,
-                               const gchar     *sender_name,
-                               const gchar     *object_path,
-                               const gchar     *interface_name,
-                               const gchar     *signal_name,
-                               GVariant        *parameters,
-                               gpointer         user_data)
-{
-  DConfSettingsBackend *dcsb = user_data;
-  const gchar *anti_expose;
-  const gchar **rels;
-  const gchar *path;
-  gchar bus_type;
-
-  if (connection == dcsb->session_bus)
-    {
-      anti_expose = dcsb->anti_expose_tag;
-      bus_type = 'e';
-    }
-
-  else if (connection == dcsb->system_bus)
-    {
-      anti_expose = NULL;
-      bus_type = 'y';
-    }
-
-  else
-    g_assert_not_reached ();
-
-  if (dconf_engine_decode_notify (dcsb->engine, anti_expose,
-                                  &path, &rels, bus_type,
-                                  sender_name, interface_name,
-                                  signal_name, parameters))
-    {
-      GSettingsBackend *backend = G_SETTINGS_BACKEND (dcsb);
-
-      if (!g_str_has_suffix (path, "/"))
-        g_settings_backend_changed (backend, path, NULL);
-
-      else if (rels[0] == NULL)
-        g_settings_backend_path_changed (backend, path, NULL);
-
-      else
-        g_settings_backend_keys_changed (backend, path, rels, NULL);
-
-      g_free (rels);
-    }
-
-  if (dconf_engine_decode_writability_notify (&path, interface_name,
-                                              signal_name, parameters))
-    {
-      GSettingsBackend *backend = G_SETTINGS_BACKEND (dcsb);
-
-      if (g_str_has_suffix (path, "/"))
-        {
-          g_settings_backend_path_writable_changed (backend, path);
-          g_settings_backend_path_changed (backend, path, NULL);
-        }
-
-      else
-        {
-          g_settings_backend_writable_changed (backend, path);
-          g_settings_backend_changed (backend, path, NULL);
-        }
-    }
-}
-
-static void
-dconf_settings_backend_send (DConfSettingsBackend *dcsb,
-                             DConfEngineMessage   *dcem,
-                             GAsyncReadyCallback   callback,
-                             gpointer              user_data)
-{
-  GDBusConnection *connection;
-  gint i;
-
-  for (i = 0; i < dcem->n_messages; i++)
-    {
-      GError *error = NULL;
-
-      switch (dcem->bus_types[i])
-        {
-        case 'e':
-          if (dcsb->session_bus == NULL && callback)
-            {
-              dcsb->session_bus =
-                g_bus_get_sync (G_BUS_TYPE_SESSION, NULL, &error);
-
-              if (dcsb->session_bus != NULL)
-                dcsb->session_subscription =
-                  g_dbus_connection_signal_subscribe (dcsb->session_bus, NULL,
-                                                      "ca.desrt.dconf.Writer",
-                                                      NULL, NULL, NULL,
-                                                      G_DBUS_SIGNAL_FLAGS_NO_MATCH_RULE,
-                                                      dconf_settings_backend_signal,
-                                                      dcsb, NULL);
-            }
-          connection = dcsb->session_bus;
-          break;
-
-        case 'y':
-          if (dcsb->system_bus == NULL && callback)
-            {
-              dcsb->system_bus =
-                g_bus_get_sync (G_BUS_TYPE_SYSTEM, NULL, &error);
-
-              if (dcsb->system_bus != NULL)
-                dcsb->system_subscription =
-                  g_dbus_connection_signal_subscribe (dcsb->system_bus, NULL,
-                                                      "ca.desrt.dconf.Writer",
-                                                      NULL, NULL, NULL,
-                                                      G_DBUS_SIGNAL_FLAGS_NO_MATCH_RULE,
-                                                      dconf_settings_backend_signal,
-                                                      dcsb, NULL);
-            }
-          connection = dcsb->system_bus;
-          break;
-
-        default:
-          g_assert_not_reached ();
-        }
-
-      if (connection == NULL && callback != NULL)
-        {
-          g_assert (error != NULL);
-
-          g_warning ("%s", error->message);
-          g_error_free (error);
-
-          callback (NULL, NULL, user_data);
-        }
-
-      if (connection != NULL)
-        g_dbus_connection_call (connection,
-                                dcem->bus_name,
-                                dcem->object_path,
-                                dcem->interface_name,
-                                dcem->method_name,
-                                dcem->parameters[i],
-                                dcem->reply_type,
-                                0, 120000, NULL, callback, user_data);
-    }
-}
-
-static GVariant *
-dconf_settings_backend_send_finish (GObject      *source,
-                                    GAsyncResult *result)
-{
-  GError *error = NULL;
-  GVariant *reply;
-
-  if (source == NULL)
-    return NULL;
-
-  reply = g_dbus_connection_call_finish (G_DBUS_CONNECTION (source),
-                                         result, &error);
-
-  if (reply == NULL)
-    {
-      /* This should only be hit in the case that something is seriously
-       * wrong with the installation (ie: the service can't be started,
-       * etc).  Bug #641768 requests some notification of these kinds of
-       * situations in the context of the gsettings(1) commandline tool,
-       * so a g_warning() is appropriate here.
-       */
-
-      g_warning ("%s", error->message);
-      g_error_free (error);
-    }
-
-  return reply;
-}
-
-struct _Outstanding
-{
-  Outstanding *next;
-
-  DConfSettingsBackend *dcsb;
-  DConfEngineMessage    dcem;
-
-  gchar    *set_key;
-  GVariant *set_value;
-  GTree    *tree;
-};
-
-static void
-dconf_settings_backend_outstanding_returned (GObject      *source,
-                                             GAsyncResult *result,
-                                             gpointer      user_data)
-{
-  Outstanding *outstanding = user_data;
-  DConfSettingsBackend *dcsb;
-  GVariant *reply;
-
-  dcsb = outstanding->dcsb;
-
-  /* One way or another we no longer need this hooked into the list.
-   */
-  g_mutex_lock (&dcsb->lock);
-  {
-    Outstanding **tmp;
-
-    for (tmp = &dcsb->outstanding; tmp; tmp = &(*tmp)->next)
-      if (*tmp == outstanding)
-        {
-          *tmp = outstanding->next;
-          break;
-        }
-
-    if (dcsb->outstanding == NULL && dcsb->sync_waiters)
-      g_cond_broadcast (&dcsb->sync_cond);
-  }
-  g_mutex_unlock (&dcsb->lock);
-
-  reply = dconf_settings_backend_send_finish (source, result);
-
-  if (reply)
-    {
-      /* Success.
-       *
-       * We want to ensure that we don't emit an extra change
-       * notification signal when we see the signal that the service is
-       * about to send, so store the tag so we know to ignore it when
-       * the signal comes.
-       *
-       * No thread safety issue here since this variable is only
-       * accessed from the worker thread.
-       */
-      g_free (dcsb->anti_expose_tag);
-      g_variant_get_child (reply, 0, "s", &dcsb->anti_expose_tag);
-      g_variant_unref (reply);
-    }
-  else
-    {
-      /* An error of some kind.
-       *
-       * We already removed the outstanding entry from the list, so the
-       * unmodified database is now visible to the client.  Change
-       * notify so that they see it.
-       */
-      if (outstanding->set_key)
-        g_settings_backend_changed (G_SETTINGS_BACKEND (dcsb),
-                                    outstanding->set_key, NULL);
-
-      else
-        g_settings_backend_changed_tree (G_SETTINGS_BACKEND (dcsb),
-                                         outstanding->tree, NULL);
-    }
-
-  dconf_engine_message_destroy (&outstanding->dcem);
-  g_object_unref (outstanding->dcsb);
-  g_free (outstanding->set_key);
-
-  if (outstanding->set_value)
-    g_variant_unref (outstanding->set_value);
-
-  if (outstanding->tree)
-    g_tree_unref (outstanding->tree);
-
-  g_slice_free (Outstanding, outstanding);
-}
-
-static gboolean
-dconf_settings_backend_send_outstanding (gpointer data)
-{
-  Outstanding *outstanding = data;
-
-  dconf_settings_backend_send (outstanding->dcsb,
-                               &outstanding->dcem,
-                               dconf_settings_backend_outstanding_returned,
-                               outstanding);
-
-  return FALSE;
-}
-
-static void
-dconf_settings_backend_queue (DConfSettingsBackend *dcsb,
-                              DConfEngineMessage   *dcem,
-                              const gchar          *set_key,
-                              GVariant             *set_value,
-                              GTree                *tree)
-{
-  Outstanding *outstanding;
-
-  outstanding = g_slice_new (Outstanding);
-  outstanding->dcsb = g_object_ref (dcsb);
-  outstanding->dcem = *dcem;
-
-  outstanding->set_key = g_strdup (set_key);
-  outstanding->set_value = set_value ? g_variant_ref_sink (set_value) : NULL;
-  outstanding->tree = tree ? g_tree_ref (tree) : NULL;
-
-  g_mutex_lock (&dcsb->lock);
-  outstanding->next = dcsb->outstanding;
-  dcsb->outstanding = outstanding;
-  g_mutex_unlock (&dcsb->lock);
-
-  g_main_context_invoke (dconf_context_get (),
-                         dconf_settings_backend_send_outstanding,
-                         outstanding);
-}
-
-static gboolean
-dconf_settings_backend_scan_outstanding_tree (GTree       *tree,
-                                              const gchar *key,
-                                              gsize        key_length,
-                                              gpointer    *value)
-{
-  gchar *mykey;
-
-  mykey = g_alloca (key_length + 1);
-  memcpy (mykey, key, key_length + 1);
-
-  while (!g_tree_lookup_extended (tree, mykey, NULL, value) &&
-         --key_length)
-    {
-      while (mykey[key_length - 1] != '/')
-        key_length--;
-
-      mykey[key_length] = '\0';
-    }
-
-  return key_length != 0;
-}
-
-static gboolean
-dconf_settings_backend_scan_outstanding (DConfSettingsBackend  *backend,
-                                         const gchar           *key,
-                                         GVariant             **value)
-{
-  gboolean found = FALSE;
-  Outstanding *node;
-  gsize length;
-
-  length = strlen (key);
-
-  if G_LIKELY (backend->outstanding == NULL)
-    return FALSE;
-
-  g_mutex_lock (&backend->lock);
-
-  for (node = backend->outstanding; node; node = node->next)
-    {
-      if (node->set_key)
-        {
-          if (strcmp (key, node->set_key) == 0)
-            {
-              if (node->set_value != NULL)
-                *value = g_variant_ref (node->set_value);
-              else
-                *value = NULL;
-
-              found = TRUE;
-              break;
-            }
-        }
-
-      else
-        {
-          gpointer result;
-
-          if (dconf_settings_backend_scan_outstanding_tree (node->tree, key,
-                                                            length, &result))
-            {
-              if (result)
-                *value = g_variant_ref (result);
-              else
-                *value = NULL;
-
-              found = TRUE;
-              break;
-            }
-        }
-    }
-
-  g_mutex_unlock (&backend->lock);
-
-  return found;
-}
+G_DEFINE_TYPE (DConfSettingsBackend, dconf_settings_backend, G_TYPE_SETTINGS_BACKEND)
 
 static GVariant *
 dconf_settings_backend_read (GSettingsBackend   *backend,
@@ -443,17 +47,9 @@ dconf_settings_backend_read (GSettingsBackend   *backend,
 {
   DConfSettingsBackend *dcsb = (DConfSettingsBackend *) backend;
 
-  if (!default_value)
-    {
-      GVariant *value;
+  /* XXX default value */
 
-      if (dconf_settings_backend_scan_outstanding (dcsb, key, &value))
-        return value;
-
-      return dconf_engine_read (dcsb->engine, key);
-    }
-  else
-    return dconf_engine_read_default (dcsb->engine, key);
+  return dconf_engine_read (dcsb->engine, NULL, key);
 }
 
 static gboolean
@@ -463,15 +59,26 @@ dconf_settings_backend_write (GSettingsBackend *backend,
                               gpointer          origin_tag)
 {
   DConfSettingsBackend *dcsb = (DConfSettingsBackend *) backend;
-  DConfEngineMessage dcem;
+  DConfChangeset *change;
+  gboolean success;
 
-  if (!dconf_engine_write (dcsb->engine, key, value, &dcem, NULL))
-    return FALSE;
+  change = dconf_changeset_new ();
+  dconf_changeset_set (change, key, value);
+
+  success = dconf_engine_change_fast (dcsb->engine, change, NULL);
+  dconf_changeset_unref (change);
+
+  return success;
+}
 
-  dconf_settings_backend_queue (dcsb, &dcem, key, value, NULL);
-  g_settings_backend_changed (backend, key, origin_tag);
+static gboolean
+dconf_settings_backend_add_to_changeset (gpointer key,
+                                         gpointer value,
+                                         gpointer data)
+{
+  dconf_changeset_set (data, key, value);
 
-  return TRUE;
+  return FALSE;
 }
 
 static gboolean
@@ -480,24 +87,14 @@ dconf_settings_backend_write_tree (GSettingsBackend *backend,
                                    gpointer          origin_tag)
 {
   DConfSettingsBackend *dcsb = (DConfSettingsBackend *) backend;
-  DConfEngineMessage dcem;
-  const gchar **keys;
-  GVariant **values;
+  DConfChangeset *change;
   gboolean success;
-  gchar *prefix;
 
-  g_settings_backend_flatten_tree (tree, &prefix, &keys, &values);
+  change= dconf_changeset_new ();
+  g_tree_foreach (tree, dconf_settings_backend_add_to_changeset, change);
 
-  if ((success = dconf_engine_write_many (dcsb->engine, prefix,
-                                          keys, values, &dcem, NULL)))
-    {
-      dconf_settings_backend_queue (dcsb, &dcem, NULL, NULL, tree);
-      g_settings_backend_keys_changed (backend, prefix, keys, origin_tag);
-    }
-
-  g_free (prefix);
-  g_free (values);
-  g_free (keys);
+  success = dconf_engine_change_fast (dcsb->engine, change, NULL);
+  dconf_changeset_unref (change);
 
   return success;
 }
@@ -519,111 +116,13 @@ dconf_settings_backend_get_writable (GSettingsBackend *backend,
   return dconf_engine_is_writable (dcsb->engine, name);
 }
 
-typedef struct
-{
-  DConfSettingsBackend *dcsb;
-  guint64 state;
-  gchar *name;
-  gint outstanding;
-} OutstandingWatch;
-
-static OutstandingWatch *
-outstanding_watch_new (DConfSettingsBackend *dcsb,
-                       const gchar          *name)
-{
-  OutstandingWatch *watch;
-
-  watch = g_slice_new (OutstandingWatch);
-  watch->dcsb = g_object_ref (dcsb);
-  watch->state = dconf_engine_get_state (dcsb->engine);
-  watch->outstanding = 0;
-  watch->name = g_strdup (name);
-
-  return watch;
-}
-
-static void
-outstanding_watch_free (OutstandingWatch *watch)
-{
-  if (--watch->outstanding == 0)
-    {
-      g_object_unref (watch->dcsb);
-      g_free (watch->name);
-
-      g_slice_free (OutstandingWatch, watch);
-    }
-}
-
-static void
-add_match_done (GObject      *source,
-                GAsyncResult *result,
-                gpointer      user_data)
-{
-  OutstandingWatch *watch = user_data;
-  GError *error = NULL;
-  GVariant *reply;
-
-  /* couldn't connect to DBus */
-  if (source == NULL)
-    {
-      outstanding_watch_free (watch);
-      return;
-    }
-
-  reply = g_dbus_connection_call_finish (G_DBUS_CONNECTION (source),
-                                         result, &error);
-
-  if (reply == NULL)
-    {
-      g_critical ("DBus AddMatch for dconf path '%s': %s",
-                  watch->name, error->message);
-      outstanding_watch_free (watch);
-      g_error_free (error);
-
-      return;
-    }
-
-  else
-    g_variant_unref (reply); /* it is just an empty tuple */
-
-  /* In the normal case we can just free everything and be done.
-   *
-   * There is a fleeting chance, however, that the database has changed
-   * in the meantime.  In that case we can only assume that the subject
-   * of this watch changed in that time period and emit a signal to that
-   * effect.
-   */
-  if (dconf_engine_get_state (watch->dcsb->engine) != watch->state)
-    g_settings_backend_path_changed (G_SETTINGS_BACKEND (watch->dcsb),
-                                     watch->name, NULL);
-
-  outstanding_watch_free (watch);
-}
-
-static gboolean
-dconf_settings_backend_subscribe_context_func (gpointer data)
-{
-  OutstandingWatch *watch = data;
-  DConfEngineMessage dcem;
-
-  dconf_engine_watch (watch->dcsb->engine, watch->name, &dcem);
-  watch->outstanding = dcem.n_messages;
-
-  dconf_settings_backend_send (watch->dcsb, &dcem, add_match_done, watch);
-  dconf_engine_message_destroy (&dcem);
-
-  return FALSE;
-}
-
 static void
 dconf_settings_backend_subscribe (GSettingsBackend *backend,
                                   const gchar      *name)
 {
   DConfSettingsBackend *dcsb = (DConfSettingsBackend *) backend;
 
-  g_main_context_invoke (dconf_context_get (),
-                         dconf_settings_backend_subscribe_context_func,
-                         outstanding_watch_new (dcsb, name));
+  dconf_engine_watch_fast (dcsb->engine, name);
 }
 
 static void
@@ -631,42 +130,40 @@ dconf_settings_backend_unsubscribe (GSettingsBackend *backend,
                                     const gchar      *name)
 {
   DConfSettingsBackend *dcsb = (DConfSettingsBackend *) backend;
-  DConfEngineMessage dcem;
 
-  dconf_engine_unwatch (dcsb->engine, name, &dcem);
-  dconf_settings_backend_send (dcsb, &dcem, NULL, NULL);
-  dconf_engine_message_destroy (&dcem);
+  dconf_engine_unwatch_fast (dcsb->engine, name);
 }
 
 static void
 dconf_settings_backend_sync (GSettingsBackend *backend)
 {
-  DConfSettingsBackend *dcsb = (DConfSettingsBackend *) backend;
-
-  if (!dcsb->outstanding)
-    return;
-
-  g_mutex_lock (&dcsb->lock);
-
-  dcsb->sync_waiters++;
-  while (dcsb->outstanding)
-    g_cond_wait (&dcsb->sync_cond, &dcsb->lock);
-  dcsb->sync_waiters--;
-
-  g_mutex_unlock (&dcsb->lock);
+  /* XXX implement sync */
 }
 
 static void
 dconf_settings_backend_init (DConfSettingsBackend *dcsb)
 {
-  dcsb->engine = dconf_engine_new (NULL);
-  g_mutex_init (&dcsb->lock);
-  g_cond_init (&dcsb->sync_cond);
+  dcsb->engine = dconf_engine_new (dcsb);
+}
+
+static void
+dconf_settings_backend_finalize (GObject *object)
+{
+  DConfSettingsBackend *dcsb = (DConfSettingsBackend *) object;
+
+  dconf_engine_free (dcsb->engine);
+
+  G_OBJECT_CLASS (dconf_settings_backend_parent_class)
+    ->finalize (object);
 }
 
 static void
 dconf_settings_backend_class_init (GSettingsBackendClass *class)
 {
+  GObjectClass *object_class = G_OBJECT_CLASS (class);
+
+  object_class->finalize = dconf_settings_backend_finalize;
+
   class->read = dconf_settings_backend_read;
   class->write = dconf_settings_backend_write;
   class->write_tree = dconf_settings_backend_write_tree;
@@ -697,3 +194,12 @@ g_io_module_query (void)
 {
   return g_strsplit (G_SETTINGS_BACKEND_EXTENSION_POINT_NAME, "!", 0);
 }
+
+void
+dconf_engine_change_notify (DConfEngine         *engine,
+                            const gchar         *prefix,
+                            const gchar * const *changes,
+                            const gchar         *tag,
+                            gpointer             user_data)
+{
+}