add GtkMenuTrackerItem

Add a new class, GtkMenuTrackerItem that represents a menu item, to be
used with GtkMenuTracker.

GtkMenuTracker's insert callback now works in terms of this new type
(instead of passing reference to the model and an index to the item).

GtkMenuShell now handles all of the binding tasks internally, mostly
through the use of property bindings.  Having bindings for the label and
visibility attributes, in partiular, will help with supporting upcoming
extensions to GMenuModel.

GtkModelMenu has been reduced to a helper class that has nothing to do
with GMenuModel.  It represents something closer to an "ideal" API for
GtkMenuItem if we didn't have compatibility concerns (eg: not emitting
"activate" when setting toggle state, no separate subclasses per menu
item type, supporting icons, etc.) Improvements to GtkMenuItem could
eventually shrink the size of this class or remove the need for it
entirely.

Some GtkActionHelper functionality has been duplicated in
GtkMenuTracker, which is suboptimal.  The duplication exists so that
other codebases (such as Unity and gnome-shell) can reuse the
GtkMenuTracker code, whereas GtkActionHelper is very much tied to
GtkWidget.  Supporting binding arbitrary GtkWidgets to actions vs.
supporting the full range of GMenuModel features for menu items turns
out to be two overlapping but not entirely similar problems.  Some of
the duplication (such as roles) can be removed from GtkActionHelper once
Gtk's internal Mac OS menubar support is ported to GtkMenuTracker.

The intent to reuse the code outside of Gtk is also the reason for the
unusual treatment of the enum type introduced in this comment.

This adds no new "public" API to the Gtk library, other than types that
we cannot make private due to GType limitations.

1 files changed, 731 insertions, 0 deletions

diff --git a/gtk/gtkmenutrackeritem.c b/gtk/gtkmenutrackeritem.c
new file mode 100644
index 0000000000..3c6e8f54a8
--- /dev/null
+++ b/gtk/gtkmenutrackeritem.c
@@ -0,0 +1,731 @@
+/*
+ * Copyright © 2013 Canonical 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 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.
+ *
+ * Author: Ryan Lortie <desrt@desrt.ca>
+ */
+
+#include "config.h"
+
+#include "gtkmenutrackeritem.h"
+
+typedef GObjectClass GtkMenuTrackerItemClass;
+
+struct _GtkMenuTrackerItem
+{
+  GObject parent_instance;
+
+  GtkActionObservable *observable;
+  gchar *action_namespace;
+  GMenuItem *item;
+  GtkMenuTrackerItemRole role : 4;
+  guint is_separator : 1;
+  guint can_activate : 1;
+  guint sensitive : 1;
+  guint toggled : 1;
+  guint submenu_shown : 1;
+  guint submenu_requested : 1;
+};
+
+enum {
+  PROP_0,
+  PROP_IS_SEPARATOR,
+  PROP_HAS_SUBMENU,
+  PROP_LABEL,
+  PROP_ICON,
+  PROP_SENSITIVE,
+  PROP_VISIBLE,
+  PROP_ROLE,
+  PROP_TOGGLED,
+  PROP_ACCEL,
+  PROP_SUBMENU_SHOWN,
+  N_PROPS
+};
+
+static GParamSpec *gtk_menu_tracker_item_pspecs[N_PROPS];
+
+static void gtk_menu_tracker_item_init_observer_iface (GtkActionObserverInterface *iface);
+G_DEFINE_TYPE_WITH_CODE (GtkMenuTrackerItem, gtk_menu_tracker_item, G_TYPE_OBJECT,
+                         G_IMPLEMENT_INTERFACE (GTK_TYPE_ACTION_OBSERVER, gtk_menu_tracker_item_init_observer_iface))
+
+GType
+gtk_menu_tracker_item_role_get_type (void)
+{
+  static gsize gtk_menu_tracker_item_role_type;
+
+  if (g_once_init_enter (&gtk_menu_tracker_item_role_type))
+    {
+      static const GEnumValue values[] = {
+        { GTK_MENU_TRACKER_ITEM_ROLE_NORMAL, "GTK_MENU_TRACKER_ITEM_ROLE_NORMAL", "normal" },
+        { GTK_MENU_TRACKER_ITEM_ROLE_CHECK, "GTK_MENU_TRACKER_ITEM_ROLE_CHECK", "check" },
+        { GTK_MENU_TRACKER_ITEM_ROLE_RADIO, "GTK_MENU_TRACKER_ITEM_ROLE_RADIO", "radio" },
+        { 0, NULL, NULL }
+      };
+      GType type;
+
+      type = g_enum_register_static ("GtkMenuTrackerItemRole", values);
+
+      g_once_init_leave (&gtk_menu_tracker_item_role_type, type);
+    }
+
+  return gtk_menu_tracker_item_role_type;
+}
+
+static void
+gtk_menu_tracker_item_get_property (GObject    *object,
+                                    guint       prop_id,
+                                    GValue     *value,
+                                    GParamSpec *pspec)
+{
+  GtkMenuTrackerItem *self = GTK_MENU_TRACKER_ITEM (object);
+
+  switch (prop_id)
+    {
+    case PROP_IS_SEPARATOR:
+      g_value_set_boolean (value, gtk_menu_tracker_item_get_is_separator (self));
+      break;
+    case PROP_HAS_SUBMENU:
+      g_value_set_boolean (value, gtk_menu_tracker_item_get_has_submenu (self));
+      break;
+    case PROP_LABEL:
+      g_value_set_string (value, gtk_menu_tracker_item_get_label (self));
+      break;
+    case PROP_ICON:
+      g_value_set_object (value, gtk_menu_tracker_item_get_icon (self));
+      break;
+    case PROP_SENSITIVE:
+      g_value_set_boolean (value, gtk_menu_tracker_item_get_sensitive (self));
+      break;
+    case PROP_VISIBLE:
+      g_value_set_boolean (value, gtk_menu_tracker_item_get_visible (self));
+      break;
+    case PROP_ROLE:
+      g_value_set_enum (value, gtk_menu_tracker_item_get_role (self));
+      break;
+    case PROP_TOGGLED:
+      g_value_set_boolean (value, gtk_menu_tracker_item_get_toggled (self));
+      break;
+    case PROP_ACCEL:
+      g_value_set_string (value, gtk_menu_tracker_item_get_accel (self));
+      break;
+    case PROP_SUBMENU_SHOWN:
+      g_value_set_boolean (value, gtk_menu_tracker_item_get_submenu_shown (self));
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+  }
+}
+
+static void
+gtk_menu_tracker_item_finalize (GObject *object)
+{
+  GtkMenuTrackerItem *self = GTK_MENU_TRACKER_ITEM (object);
+
+  g_free (self->action_namespace);
+
+  if (self->observable)
+    g_object_unref (self->observable);
+
+  g_object_unref (self->item);
+
+  G_OBJECT_CLASS (gtk_menu_tracker_item_parent_class)->finalize (object);
+}
+
+static void
+gtk_menu_tracker_item_init (GtkMenuTrackerItem * self)
+{
+}
+
+static void
+gtk_menu_tracker_item_class_init (GtkMenuTrackerItemClass *class)
+{
+  class->get_property = gtk_menu_tracker_item_get_property;
+  class->finalize = gtk_menu_tracker_item_finalize;
+
+  gtk_menu_tracker_item_pspecs[PROP_IS_SEPARATOR] =
+    g_param_spec_boolean ("is-separator", "", "", FALSE, G_PARAM_STATIC_STRINGS | G_PARAM_READABLE);
+  gtk_menu_tracker_item_pspecs[PROP_HAS_SUBMENU] =
+    g_param_spec_boolean ("has-submenu", "", "", FALSE, G_PARAM_STATIC_STRINGS | G_PARAM_READABLE);
+  gtk_menu_tracker_item_pspecs[PROP_LABEL] =
+    g_param_spec_string ("label", "", "", NULL, G_PARAM_STATIC_STRINGS | G_PARAM_READABLE);
+  gtk_menu_tracker_item_pspecs[PROP_ICON] =
+    g_param_spec_object ("icon", "", "", G_TYPE_ICON, G_PARAM_STATIC_STRINGS | G_PARAM_READABLE);
+  gtk_menu_tracker_item_pspecs[PROP_SENSITIVE] =
+    g_param_spec_boolean ("sensitive", "", "", FALSE, G_PARAM_STATIC_STRINGS | G_PARAM_READABLE);
+  gtk_menu_tracker_item_pspecs[PROP_VISIBLE] =
+    g_param_spec_boolean ("visible", "", "", FALSE, G_PARAM_STATIC_STRINGS | G_PARAM_READABLE);
+  gtk_menu_tracker_item_pspecs[PROP_ROLE] =
+    g_param_spec_enum ("role", "", "",
+                       GTK_TYPE_MENU_TRACKER_ITEM_ROLE, GTK_MENU_TRACKER_ITEM_ROLE_NORMAL,
+                       G_PARAM_STATIC_STRINGS | G_PARAM_READABLE);
+  gtk_menu_tracker_item_pspecs[PROP_TOGGLED] =
+    g_param_spec_boolean ("toggled", "", "", FALSE, G_PARAM_STATIC_STRINGS | G_PARAM_READABLE);
+  gtk_menu_tracker_item_pspecs[PROP_ACCEL] =
+    g_param_spec_string ("accel", "", "", NULL, G_PARAM_STATIC_STRINGS | G_PARAM_READABLE);
+  gtk_menu_tracker_item_pspecs[PROP_SUBMENU_SHOWN] =
+    g_param_spec_boolean ("submenu-shown", "", "", FALSE, G_PARAM_STATIC_STRINGS | G_PARAM_READABLE);
+
+  g_object_class_install_properties (class, N_PROPS, gtk_menu_tracker_item_pspecs);
+}
+
+static void
+gtk_menu_tracker_item_action_added (GtkActionObserver   *observer,
+                                    GtkActionObservable *observable,
+                                    const gchar         *action_name,
+                                    const GVariantType  *parameter_type,
+                                    gboolean             enabled,
+                                    GVariant            *state)
+{
+  GtkMenuTrackerItem *self = GTK_MENU_TRACKER_ITEM (observer);
+  GVariant *action_target;
+
+  action_target = g_menu_item_get_attribute_value (self->item, G_MENU_ATTRIBUTE_TARGET, NULL);
+
+  self->can_activate = (action_target == NULL && parameter_type == NULL) ||
+                        (action_target != NULL && parameter_type != NULL &&
+                        g_variant_is_of_type (action_target, parameter_type));
+
+  if (!self->can_activate)
+    {
+      if (action_target)
+        g_variant_unref (action_target);
+      return;
+    }
+
+  self->sensitive = enabled;
+
+  if (action_target != NULL && state != NULL)
+    {
+      self->toggled = g_variant_equal (state, action_target);
+      self->role = GTK_MENU_TRACKER_ITEM_ROLE_RADIO;
+    }
+
+  else if (state != NULL && g_variant_is_of_type (state, G_VARIANT_TYPE_BOOLEAN))
+    {
+      self->toggled = g_variant_get_boolean (state);
+      self->role = GTK_MENU_TRACKER_ITEM_ROLE_CHECK;
+    }
+
+  g_object_freeze_notify (G_OBJECT (self));
+
+  if (self->sensitive)
+    g_object_notify_by_pspec (G_OBJECT (self), gtk_menu_tracker_item_pspecs[PROP_SENSITIVE]);
+
+  if (self->toggled)
+    g_object_notify_by_pspec (G_OBJECT (self), gtk_menu_tracker_item_pspecs[PROP_TOGGLED]);
+
+  if (self->role != GTK_MENU_TRACKER_ITEM_ROLE_NORMAL)
+    g_object_notify_by_pspec (G_OBJECT (self), gtk_menu_tracker_item_pspecs[PROP_ROLE]);
+
+  g_object_thaw_notify (G_OBJECT (self));
+
+  if (action_target)
+    g_variant_unref (action_target);
+}
+
+static void
+gtk_menu_tracker_item_action_enabled_changed (GtkActionObserver   *observer,
+                                              GtkActionObservable *observable,
+                                              const gchar         *action_name,
+                                              gboolean             enabled)
+{
+  GtkMenuTrackerItem *self = GTK_MENU_TRACKER_ITEM (observer);
+
+  if (!self->can_activate)
+    return;
+
+  if (self->sensitive == enabled)
+    return;
+
+  self->sensitive = enabled;
+
+  g_object_notify_by_pspec (G_OBJECT (self), gtk_menu_tracker_item_pspecs[PROP_SENSITIVE]);
+}
+
+static void
+gtk_menu_tracker_item_action_state_changed (GtkActionObserver   *observer,
+                                            GtkActionObservable *observable,
+                                            const gchar         *action_name,
+                                            GVariant            *state)
+{
+  GtkMenuTrackerItem *self = GTK_MENU_TRACKER_ITEM (observer);
+  GVariant *action_target;
+  gboolean was_toggled;
+
+  if (!self->can_activate)
+    return;
+
+  action_target = g_menu_item_get_attribute_value (self->item, G_MENU_ATTRIBUTE_TARGET, NULL);
+  was_toggled = self->toggled;
+
+  if (action_target)
+    {
+      self->toggled = g_variant_equal (state, action_target);
+      g_variant_unref (action_target);
+    }
+
+  else if (g_variant_is_of_type (state, G_VARIANT_TYPE_BOOLEAN))
+    self->toggled = g_variant_get_boolean (state);
+
+  else
+    self->toggled = FALSE;
+
+  if (self->toggled != was_toggled)
+    g_object_notify_by_pspec (G_OBJECT (self), gtk_menu_tracker_item_pspecs[PROP_TOGGLED]);
+}
+
+static void
+gtk_menu_tracker_item_action_removed (GtkActionObserver   *observer,
+                                      GtkActionObservable *observable,
+                                      const gchar         *action_name)
+{
+  GtkMenuTrackerItem *self = GTK_MENU_TRACKER_ITEM (observer);
+
+  if (!self->can_activate)
+    return;
+
+  g_object_freeze_notify (G_OBJECT (self));
+
+  if (self->sensitive)
+    {
+      self->sensitive = FALSE;
+      g_object_notify_by_pspec (G_OBJECT (self), gtk_menu_tracker_item_pspecs[PROP_SENSITIVE]);
+    }
+
+  if (self->toggled)
+    {
+      self->toggled = FALSE;
+      g_object_notify_by_pspec (G_OBJECT (self), gtk_menu_tracker_item_pspecs[PROP_TOGGLED]);
+    }
+
+  if (self->role != GTK_MENU_TRACKER_ITEM_ROLE_NORMAL)
+    {
+      self->role = GTK_MENU_TRACKER_ITEM_ROLE_NORMAL;
+      g_object_notify_by_pspec (G_OBJECT (self), gtk_menu_tracker_item_pspecs[PROP_ROLE]);
+    }
+
+  g_object_thaw_notify (G_OBJECT (self));
+}
+
+static void
+gtk_menu_tracker_item_init_observer_iface (GtkActionObserverInterface *iface)
+{
+  iface->action_added = gtk_menu_tracker_item_action_added;
+  iface->action_enabled_changed = gtk_menu_tracker_item_action_enabled_changed;
+  iface->action_state_changed = gtk_menu_tracker_item_action_state_changed;
+  iface->action_removed = gtk_menu_tracker_item_action_removed;
+}
+
+GtkMenuTrackerItem *
+_gtk_menu_tracker_item_new (GtkActionObservable *observable,
+                            GMenuModel          *model,
+                            gint                 item_index,
+                            const gchar         *action_namespace,
+                            gboolean             is_separator)
+{
+  GtkMenuTrackerItem *self;
+  const gchar *action_name;
+
+  g_return_val_if_fail (GTK_IS_ACTION_OBSERVABLE (observable), NULL);
+  g_return_val_if_fail (G_IS_MENU_MODEL (model), NULL);
+
+  self = g_object_new (GTK_TYPE_MENU_TRACKER_ITEM, NULL);
+  self->item = g_menu_item_new_from_model (model, item_index);
+  self->action_namespace = g_strdup (action_namespace);
+  self->observable = g_object_ref (observable);
+  self->is_separator = is_separator;
+
+  if (!is_separator && g_menu_item_get_attribute (self->item, "action", "&s", &action_name))
+    {
+      GActionGroup *group = G_ACTION_GROUP (observable);
+      const GVariantType *parameter_type;
+      gboolean enabled;
+      GVariant *state;
+      gboolean found;
+
+      state = NULL;
+
+      if (action_namespace)
+        {
+          gchar *full_action;
+
+          full_action = g_strjoin (".", action_namespace, action_name, NULL);
+          gtk_action_observable_register_observer (self->observable, full_action, GTK_ACTION_OBSERVER (self));
+          found = g_action_group_query_action (group, full_action, &enabled, &parameter_type, NULL, NULL, &state);
+          g_free (full_action);
+        }
+      else
+        {
+          gtk_action_observable_register_observer (self->observable, action_name, GTK_ACTION_OBSERVER (self));
+          found = g_action_group_query_action (group, action_name, &enabled, &parameter_type, NULL, NULL, &state);
+        }
+
+      if (found)
+        gtk_menu_tracker_item_action_added (GTK_ACTION_OBSERVER (self), observable, NULL, parameter_type, enabled, state);
+      else
+        gtk_menu_tracker_item_action_removed (GTK_ACTION_OBSERVER (self), observable, NULL);
+
+      if (state)
+        g_variant_unref (state);
+    }
+  else
+    self->sensitive = TRUE;
+
+  return self;
+}
+
+GtkActionObservable *
+_gtk_menu_tracker_item_get_observable (GtkMenuTrackerItem *self)
+{
+  return self->observable;
+}
+
+/**
+ * gtk_menu_tracker_item_get_is_separator:
+ * @self: A #GtkMenuTrackerItem instance
+ *
+ * Returns whether the menu item is a separator. If so, only
+ * certain properties may need to be obeyed. See the documentation
+ * for #GtkMenuTrackerItem.
+ */
+gboolean
+gtk_menu_tracker_item_get_is_separator (GtkMenuTrackerItem *self)
+{
+  return self->is_separator;
+}
+
+/**
+ * gtk_menu_tracker_item_get_has_submenu:
+ * @self: A #GtkMenuTrackerItem instance
+ *
+ * Returns whether the menu item has a submenu. If so, only
+ * certain properties may need to be obeyed. See the documentation
+ * for #GtkMenuTrackerItem.
+ */
+gboolean
+gtk_menu_tracker_item_get_has_submenu (GtkMenuTrackerItem *self)
+{
+  GMenuModel *link;
+
+  link = g_menu_item_get_link (self->item, G_MENU_LINK_SUBMENU);
+
+  if (link)
+    {
+      g_object_unref (link);
+      return TRUE;
+    }
+  else
+    return FALSE;
+}
+
+const gchar *
+gtk_menu_tracker_item_get_label (GtkMenuTrackerItem *self)
+{
+  const gchar *label = NULL;
+
+  g_menu_item_get_attribute (self->item, G_MENU_ATTRIBUTE_LABEL, "&s", &label);
+
+  return label;
+}
+
+/**
+ * gtk_menu_tracker_item_get_icon:
+ *
+ * Returns: (transfer full):
+ */
+GIcon *
+gtk_menu_tracker_item_get_icon (GtkMenuTrackerItem *self)
+{
+  GVariant *icon_data;
+  GIcon *icon;
+
+  icon_data = g_menu_item_get_attribute_value (self->item, "icon", NULL);
+
+  if (icon_data == NULL)
+    return NULL;
+
+  icon = g_icon_deserialize (icon_data);
+  g_variant_unref (icon_data);
+
+  return icon;
+}
+
+gboolean
+gtk_menu_tracker_item_get_sensitive (GtkMenuTrackerItem *self)
+{
+  return self->sensitive;
+}
+
+gboolean
+gtk_menu_tracker_item_get_visible (GtkMenuTrackerItem *self)
+{
+  return TRUE;
+}
+
+GtkMenuTrackerItemRole
+gtk_menu_tracker_item_get_role (GtkMenuTrackerItem *self)
+{
+  return self->role;
+}
+
+gboolean
+gtk_menu_tracker_item_get_toggled (GtkMenuTrackerItem *self)
+{
+  return self->toggled;
+}
+
+const gchar *
+gtk_menu_tracker_item_get_accel (GtkMenuTrackerItem *self)
+{
+  const gchar *accel = NULL;
+
+  g_menu_item_get_attribute (self->item, "accel", "&s", &accel);
+
+  return accel;
+}
+
+GMenuModel *
+_gtk_menu_tracker_item_get_submenu (GtkMenuTrackerItem *self)
+{
+  return g_menu_item_get_link (self->item, "submenu");
+}
+
+gchar *
+_gtk_menu_tracker_item_get_submenu_namespace (GtkMenuTrackerItem *self)
+{
+  const gchar *namespace;
+
+  if (g_menu_item_get_attribute (self->item, "action-namespace", "&s", &namespace))
+    {
+      if (self->action_namespace)
+        return g_strjoin (".", self->action_namespace, namespace, NULL);
+      else
+        return g_strdup (namespace);
+    }
+  else
+    return g_strdup (self->action_namespace);
+}
+
+gboolean
+gtk_menu_tracker_item_get_should_request_show (GtkMenuTrackerItem *self)
+{
+  return g_menu_item_get_attribute (self->item, "submenu-action", "&s", NULL);
+}
+
+gboolean
+gtk_menu_tracker_item_get_submenu_shown (GtkMenuTrackerItem *self)
+{
+  return self->submenu_shown;
+}
+
+/* only called from the opener, internally */
+static void
+gtk_menu_tracker_item_set_submenu_shown (GtkMenuTrackerItem *self,
+                                         gboolean            submenu_shown)
+{
+  if (submenu_shown == self->submenu_shown)
+    return;
+
+  self->submenu_shown = submenu_shown;
+  g_object_notify_by_pspec (G_OBJECT (self), gtk_menu_tracker_item_pspecs[PROP_SUBMENU_SHOWN]);
+}
+
+void
+gtk_menu_tracker_item_activated (GtkMenuTrackerItem *self)
+{
+  const gchar *action_name;
+  GVariant *action_target;
+
+  g_return_if_fail (GTK_IS_MENU_TRACKER_ITEM (self));
+
+  if (!self->can_activate)
+    return;
+
+  g_menu_item_get_attribute (self->item, G_MENU_ATTRIBUTE_ACTION, "&s", &action_name);
+  action_target = g_menu_item_get_attribute_value (self->item, G_MENU_ATTRIBUTE_TARGET, NULL);
+
+  if (self->action_namespace)
+    {
+      gchar *full_action;
+
+      full_action = g_strjoin (".", self->action_namespace, action_name, NULL);
+      g_action_group_activate_action (G_ACTION_GROUP (self->observable), full_action, action_target);
+      g_free (full_action);
+    }
+  else
+    g_action_group_activate_action (G_ACTION_GROUP (self->observable), action_name, action_target);
+
+  if (action_target)
+    g_variant_unref (action_target);
+}
+
+typedef struct
+{
+  GtkMenuTrackerItem *item;
+  gchar              *submenu_action;
+  gboolean            first_time;
+} GtkMenuTrackerOpener;
+
+static void
+gtk_menu_tracker_opener_update (GtkMenuTrackerOpener *opener)
+{
+  GActionGroup *group = G_ACTION_GROUP (opener->item->observable);
+  gboolean is_open = TRUE;
+
+  /* We consider the menu as being "open" if the action does not exist
+   * or if there is another problem (no state, wrong state type, etc.).
+   * If the action exists, with the correct state then we consider it
+   * open if we have ever seen this state equal to TRUE.
+   *
+   * In the event that we see the state equal to FALSE, we force it back
+   * to TRUE.  We do not signal that the menu was closed because this is
+   * likely to create UI thrashing.
+   *
+   * The only way the menu can have a true-to-false submenu-shown
+   * transition is if the user calls _request_submenu_shown (FALSE).
+   * That is handled in _free() below.
+   */
+
+  if (g_action_group_has_action (group, opener->submenu_action))
+    {
+      GVariant *state = g_action_group_get_action_state (group, opener->submenu_action);
+
+      if (state)
+        {
+          if (g_variant_is_of_type (state, G_VARIANT_TYPE_BOOLEAN))
+            is_open = g_variant_get_boolean (state);
+          g_variant_unref (state);
+        }
+    }
+
+  /* If it is already open, signal that.
+   *
+   * If it is not open, ask it to open.
+   */
+  if (is_open)
+    gtk_menu_tracker_item_set_submenu_shown (opener->item, TRUE);
+
+  if (!is_open || opener->first_time)
+    {
+      g_action_group_change_action_state (group, opener->submenu_action, g_variant_new_boolean (TRUE));
+      opener->first_time = FALSE;
+    }
+}
+
+static void
+gtk_menu_tracker_opener_added (GActionGroup *group,
+                               const gchar  *action_name,
+                               gpointer      user_data)
+{
+  GtkMenuTrackerOpener *opener = user_data;
+
+  if (g_str_equal (action_name, opener->submenu_action))
+    gtk_menu_tracker_opener_update (opener);
+}
+
+static void
+gtk_menu_tracker_opener_removed (GActionGroup *action_group,
+                                 const gchar  *action_name,
+                                 gpointer      user_data)
+{
+  GtkMenuTrackerOpener *opener = user_data;
+
+  if (g_str_equal (action_name, opener->submenu_action))
+    gtk_menu_tracker_opener_update (opener);
+}
+
+static void
+gtk_menu_tracker_opener_changed (GActionGroup *action_group,
+                                 const gchar  *action_name,
+                                 GVariant     *new_state,
+                                 gpointer      user_data)
+{
+  GtkMenuTrackerOpener *opener = user_data;
+
+  if (g_str_equal (action_name, opener->submenu_action))
+    gtk_menu_tracker_opener_update (opener);
+}
+
+static void
+gtk_menu_tracker_opener_free (gpointer data)
+{
+  GtkMenuTrackerOpener *opener = data;
+
+  g_signal_handlers_disconnect_by_func (opener->item->observable, gtk_menu_tracker_opener_added, opener);
+  g_signal_handlers_disconnect_by_func (opener->item->observable, gtk_menu_tracker_opener_removed, opener);
+  g_signal_handlers_disconnect_by_func (opener->item->observable, gtk_menu_tracker_opener_changed, opener);
+
+  g_action_group_change_action_state (G_ACTION_GROUP (opener->item->observable),
+                                      opener->submenu_action,
+                                      g_variant_new_boolean (FALSE));
+
+  gtk_menu_tracker_item_set_submenu_shown (opener->item, FALSE);
+
+  g_free (opener->submenu_action);
+
+  g_slice_free (GtkMenuTrackerOpener, opener);
+}
+
+static GtkMenuTrackerOpener *
+gtk_menu_tracker_opener_new (GtkMenuTrackerItem *item,
+                             const gchar        *submenu_action)
+{
+  GtkMenuTrackerOpener *opener;
+
+  opener = g_slice_new (GtkMenuTrackerOpener);
+  opener->first_time = TRUE;
+  opener->item = item;
+
+  if (item->action_namespace)
+    opener->submenu_action = g_strjoin (".", item->action_namespace, submenu_action, NULL);
+  else
+    opener->submenu_action = g_strdup (submenu_action);
+
+  g_signal_connect (item->observable, "action-added", G_CALLBACK (gtk_menu_tracker_opener_added), opener);
+  g_signal_connect (item->observable, "action-removed", G_CALLBACK (gtk_menu_tracker_opener_removed), opener);
+  g_signal_connect (item->observable, "action-state-changed", G_CALLBACK (gtk_menu_tracker_opener_changed), opener);
+
+  gtk_menu_tracker_opener_update (opener);
+
+  return opener;
+}
+
+void
+gtk_menu_tracker_item_request_submenu_shown (GtkMenuTrackerItem *self,
+                                             gboolean            shown)
+{
+  const gchar *submenu_action;
+  gboolean okay;
+
+  if (shown == self->submenu_requested)
+    return;
+
+  /* Should not be getting called unless we have submenu-action.
+   */
+  okay = g_menu_item_get_attribute (self->item, "submenu-action", "&s", &submenu_action);
+  g_assert (okay);
+
+  self->submenu_requested = shown;
+
+  if (shown)
+    g_object_set_data_full (G_OBJECT (self), "submenu-opener",
+                            gtk_menu_tracker_opener_new (self, submenu_action),
+                            gtk_menu_tracker_opener_free);
+  else
+    g_object_set_data (G_OBJECT (self), "submenu-opener", NULL);
+}