GtkWidget: Add gtk_widget_insert_action_group()

This allows adding a GActionGroup with a given name at an arbitrary
point in the widget tree.

This patch also adds an internal _get_action_muxer() API.  Calling this
will create a GActionMuxer associated with the widget.  The parent of
the muxer will be the muxer of the widget's conceptual parent.  For
non-menus, that is the normal parent.  For menus, it is the attach
widget.

In this way, we end up with a hierarchy of GActionMuxer that largely
reflects the hierarchy of GtkWidget, but only in places that the action
context has been requested.  These muxers are the ones on which the
inserted actions groups are installed.

A following patch will add a user of this API.

docs/reference/gtk/gtk3-sections.txt

@@ -5291,6 +5291,7 @@ gtk_widget_get_mapped
 gtk_widget_get_requisition
 gtk_widget_device_is_shadowed
 gtk_widget_get_modifier_mask
+gtk_widget_insert_action_group
 
 <SUBSECTION>
 gtk_widget_get_path

gtk/gtk.symbols

@@ -3828,6 +3828,7 @@ gtk_widget_unmap
 gtk_widget_unparent
 gtk_widget_unrealize
 gtk_widget_unset_state_flags
+gtk_widget_insert_action_group
 #ifdef GDK_WINDOWING_WIN32
 gtk_win32_embed_widget_get_type
 #endif

gtk/gtkmenu.c

@@ -1220,6 +1220,8 @@ gtk_menu_attach_to_widget (GtkMenu           *menu,
   /* Attach the widget to the toplevel window. */
   gtk_window_set_attached_to (GTK_WINDOW (menu->priv->toplevel), attach_widget);
 
+  _gtk_widget_update_parent_muxer (GTK_WIDGET (menu));
+
   /* Fallback title for menu comes from attach widget */
   gtk_menu_update_title (menu);
 
@@ -1294,6 +1296,8 @@ gtk_menu_detach (GtkMenu *menu)
 
   g_slice_free (GtkMenuAttachData, data);
 
+  _gtk_widget_update_parent_muxer (GTK_WIDGET (menu));
+
   /* Fallback title for menu comes from attach widget */
   gtk_menu_update_title (menu);
 

gtk/gtkwidget.c

@@ -390,6 +390,9 @@ struct _GtkWidgetPrivate
   /* The widget's requested sizes */
   SizeRequestCache requests;
 
+  /* actions attached to this or any parent widget */
+  GActionMuxer *muxer;
+
   /* The widget's window or its parent window if it does
    * not have a window. (Which will be indicated by the
    * GTK_NO_WINDOW flag being set).
@@ -3899,6 +3902,8 @@ gtk_widget_unparent (GtkWidget *widget)
   if (priv->context)
     gtk_style_context_set_parent (priv->context, NULL);
 
+  _gtk_widget_update_parent_muxer (widget);
+
   g_signal_emit (widget, widget_signals[PARENT_SET], 0, old_parent);
   if (toplevel)
     {
@@ -7968,6 +7973,8 @@ gtk_widget_set_parent (GtkWidget *widget,
     gtk_style_context_set_parent (priv->context,
                                   gtk_widget_get_style_context (parent));
 
+  _gtk_widget_update_parent_muxer (widget);
+
   g_signal_emit (widget, widget_signals[PARENT_SET], 0, NULL);
   if (priv->parent->priv->anchored)
     _gtk_widget_propagate_hierarchy_changed (widget, NULL);
@@ -10268,6 +10275,8 @@ gtk_widget_dispose (GObject *object)
       priv->in_destruction = FALSE;
     }
 
+  g_clear_object (&priv->muxer);
+
   G_OBJECT_CLASS (gtk_widget_parent_class)->dispose (object);
 }
 
@@ -14072,3 +14081,61 @@ _gtk_widget_set_style (GtkWidget *widget,
 {
   widget->priv->style = style;
 }
+
+void
+_gtk_widget_update_parent_muxer (GtkWidget *widget)
+{
+  GtkWidget *parent;
+  GActionMuxer *parent_muxer;
+
+  if (widget->priv->muxer == NULL)
+    return;
+
+  if (GTK_IS_MENU (widget))
+    parent = gtk_menu_get_attach_widget (GTK_MENU (widget));
+  else
+    parent = gtk_widget_get_parent (widget);
+
+  parent_muxer = parent ? _gtk_widget_get_action_muxer (parent) : NULL;
+
+  g_action_muxer_set_parent (widget->priv->muxer, parent_muxer);
+}
+
+GActionMuxer *
+_gtk_widget_get_action_muxer (GtkWidget *widget)
+{
+  if (widget->priv->muxer == NULL)
+    {
+      widget->priv->muxer = g_action_muxer_new ();
+      _gtk_widget_update_parent_muxer (widget);
+    }
+
+  return widget->priv->muxer;
+}
+
+/**
+ * gtk_widget_insert_action_group:
+ * @widget: a #GtkWidget
+ * @name: the prefix for actions in @group
+ * @group: a #GActionGroup
+ *
+ * Inserts @group into @widget. Children of @widget that implement
+ * #GtkActionable can then be associated with actions in @group by
+ * setting their 'action-name' to @prefix.<action-name>.
+ *
+ * Since: 3.6
+ */
+void
+gtk_widget_insert_action_group (GtkWidget    *widget,
+                                const gchar  *name,
+                                GActionGroup *group)
+{
+  GActionMuxer *muxer;
+
+  g_return_if_fail (GTK_IS_WIDGET (widget));
+  g_return_if_fail (name != NULL);
+
+  muxer = _gtk_widget_get_action_muxer (widget);
+
+  g_action_muxer_insert (muxer, name, group);
+}

gtk/gtkwidget.h

@@ -886,6 +886,10 @@ GDK_AVAILABLE_IN_3_4
 GdkModifierType   gtk_widget_get_modifier_mask (GtkWidget         *widget,
                                                 GdkModifierIntent  intent);
 
+GDK_AVAILABLE_IN_3_6
+void                    gtk_widget_insert_action_group                  (GtkWidget    *widget,
+                                                                         const gchar  *name,
+                                                                         GActionGroup *group);
 
 G_END_DECLS
 

gtk/gtkwidgetprivate.h

@@ -27,6 +27,7 @@
 
 #include "gtkcsstypesprivate.h"
 #include "gtkwidget.h"
+#include "gactionmuxer.h"
 
 G_BEGIN_DECLS
 
@@ -178,6 +179,9 @@ void              _gtk_widget_invalidate_style_context     (GtkWidget    *widget
                                                             GtkCssChange  change);
 void              _gtk_widget_style_context_invalidated    (GtkWidget    *widget);
 
+void              _gtk_widget_update_parent_muxer          (GtkWidget    *widget);
+GActionMuxer *    _gtk_widget_get_action_muxer             (GtkWidget    *widget);
+
 G_END_DECLS
 
 #endif /* __GTK_WIDGET_PRIVATE_H__ */