Introduce UnityMenuModel and UnityQmlMenuModel

UnityMenuModel serves the same purpose as QMenuModel, but it is based on
GtkMenuTracker and has a different API.

GtkMenuTracker is maintained in gtk, but meant to be copy-and-pasted into other
consumers of menu models. It does not introduce new dependencies. It does give
us access to all the features that GMenuModel has.

1 files changed, 788 insertions, 0 deletions

diff --git a/libqmenumodel/src/gtk/gtkmenutrackeritem.c b/libqmenumodel/src/gtk/gtkmenutrackeritem.c
new file mode 100644
index 0000000..2d712a1
--- /dev/null
+++ b/libqmenumodel/src/gtk/gtkmenutrackeritem.c
@@ -0,0 +1,788 @@
+/*
+ * 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"
+
+/**
+ * SECTION:gtkmenutrackeritem
+ * @Title: GtkMenuTrackerItem
+ * @Short_description: Small helper for model menu items
+ *
+ * A #GtkMenuTrackerItem is a small helper class used by #GtkMenuTracker to
+ * represent menu items. It has one of three classes: normal item, separator,
+ * or submenu.
+ *
+ * If an item is one of the non-normal classes (submenu, separator), only the
+ * label of the item needs to be respected. Otherwise, all the properties
+ * of the item contribute to the item's appearance and state.
+ *
+ * Implementing the appearance of the menu item is up to toolkits, and certain
+ * toolkits may choose to ignore certain properties, like icon or accel. The
+ * role of the item determines its accessibility role, along with its
+ * decoration if the GtkMenuTrackerItem::toggled property is true. As an
+ * example, if the item has the role %GTK_MENU_TRACKER_ITEM_ROLE_CHECK and
+ * GtkMenuTrackerItem::toggled is %FALSE, its accessible role should be that of
+ * a check menu item, and no decoration should be drawn. But if
+ * GtkMenuTrackerItem::toggled is %TRUE, a checkmark should be drawn.
+ *
+ * All properties except for the two class-determining properties,
+ * GtkMenuTrackerItem::is-separator and GtkMenuTrackerItem::has-submenu are
+ * allowed to change, so listen to the notify signals to update your item's
+ * appearance. When using a GObject library, this can conveniently be done
+ * with g_object_bind_property() and #GBinding, and this is how this is
+ * implemented in GTK+; the appearance side is implemented in #GtkModelMenuItem.
+ *
+ * When an item is clicked, simply call gtk_menu_tracker_item_activated() in
+ * response. The #GtkMenuTrackerItem will take care of everything related to
+ * activating the item and will itself update the state of all items in
+ * response.
+ *
+ * Submenus are a special case of menu item. When an item is a submenu, you
+ * should create a submenu for it with gtk_menu_tracker_new_item_for_submenu(),
+ * and apply the same menu tracking logic you would for a toplevel menu.
+ * Applications using submenus may want to lazily build their submenus in
+ * response to the user clicking on it, as building a submenu may be expensive.
+ *
+ * Thus, the submenu has two special controls -- the submenu's visibility
+ * should be controlled by the GtkMenuTrackerItem::submenu-shown property,
+ * and if a user clicks on the submenu, do not immediately show the menu,
+ * but call gtk_menu_tracker_item_request_submenu_shown() and wait for the
+ * GtkMenuTrackerItem::submenu-shown property to update. If the user navigates,
+ * the application may want to be notified so it can cancel the expensive
+ * operation that it was using to build the submenu. Thus,
+ * gtk_menu_tracker_item_request_submenu_shown() takes a boolean parameter.
+ * Use %TRUE when the user wants to open the submenu, and %FALSE when the
+ * user wants to close the submenu.
+ */
+
+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;
+}
+
+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 has_submenu_action;
+
+  if (shown == self->submenu_requested)
+    return;
+
+  has_submenu_action = g_menu_item_get_attribute (self->item, "submenu-action", "&s", &submenu_action);
+
+  self->submenu_requested = shown;
+
+  /* If we have a submenu action, start a submenu opener and wait
+   * for the reply from the client. Otherwise, simply open the
+   * submenu immediately.
+   */
+  if (has_submenu_action)
+    {
+      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);
+    }
+  else
+    gtk_menu_tracker_item_set_submenu_shown (self, shown);
+}