[layout] Allow taking a back pointer to the Container

The LayoutManager implementation might opt to take a back pointer
to the Container that is using the layout instance; this allows
direct access to the container itself from within the implementation.

clutter/clutter-layout-manager.c

@@ -299,6 +299,34 @@ clutter_layout_manager_layout_changed (ClutterLayoutManager *manager)
   g_signal_emit (manager, manager_signals[LAYOUT_CHANGED], 0);
 }
 
+/**
+ * clutter_layout_manager_set_container:
+ * @manager: a #ClutterLayoutManager
+ * @container: (allow-none): a #ClutterContainer using @manager
+ *
+ * If the #ClutterLayoutManager sub-class allows it, allow
+ * adding a weak reference of the @container using @manager
+ * from within the layout manager
+ *
+ * The layout manager should not increase the reference
+ * count of the @container
+ *
+ * Since: 1.2
+ */
+void
+clutter_layout_manager_set_container (ClutterLayoutManager *manager,
+                                      ClutterContainer     *container)
+{
+  ClutterLayoutManagerClass *klass;
+
+  g_return_if_fail (CLUTTER_IS_LAYOUT_MANAGER (manager));
+  g_return_if_fail (container == NULL || CLUTTER_IS_CONTAINER (container));
+
+  klass = CLUTTER_LAYOUT_MANAGER_GET_CLASS (manager);
+  if (klass->set_container)
+    klass->set_container (manager, container);
+}
+
 static inline ClutterLayoutMeta *
 create_child_meta (ClutterLayoutManager *manager,
                    ClutterContainer     *container,

clutter/clutter-layout-manager.h

@@ -57,6 +57,9 @@ struct _ClutterLayoutManager
 {
   /*< private >*/
   GInitiallyUnowned parent_instance;
+
+  /* padding for future expansion */
+  gpointer dummy;
 };
 
 /**
@@ -70,6 +73,10 @@ struct _ClutterLayoutManager
  * @allocate: virtual function; override to allocate the children of the
  *   layout manager. See also the allocate() virtual function in
  *   #ClutterActor
+ * @set_container: virtual function; override to set a back pointer
+ *   on the #ClutterContainer using the layout manager. The implementation
+ *   should not take a reference on the container, but just take a weak
+ *   reference, to avoid potential leaks due to reference cycles
  * @create_child_meta: virtual function; override to create a
  *   #ClutterChildMeta instance associated to a #ClutterContainer and a
  *   child #ClutterActor, used to maintain layout manager specific properties
@@ -102,6 +109,9 @@ struct _ClutterLayoutManagerClass
                                                const ClutterActorBox  *allocation,
                                                ClutterAllocationFlags  flags);
 
+  void               (* set_container)        (ClutterLayoutManager   *manager,
+                                               ClutterContainer       *container);
+
   ClutterLayoutMeta *(* create_child_meta)    (ClutterLayoutManager   *manager,
                                                ClutterContainer       *container,
                                                ClutterActor           *actor);
@@ -137,6 +147,8 @@ void               clutter_layout_manager_allocate             (ClutterLayoutMan
                                                                 const ClutterActorBox  *allocation,
                                                                 ClutterAllocationFlags  flags);
 
+void               clutter_layout_manager_set_container        (ClutterLayoutManager   *manager,
+                                                                ClutterContainer       *container);
 void               clutter_layout_manager_layout_changed       (ClutterLayoutManager   *manager);
 
 ClutterLayoutMeta *clutter_layout_manager_get_child_meta       (ClutterLayoutManager   *manager,

doc/reference/clutter/clutter-sections.txt

@@ -1735,6 +1735,7 @@ clutter_layout_manager_get_preferred_width
 clutter_layout_manager_get_preferred_height
 clutter_layout_manager_allocate
 clutter_layout_manager_layout_changed
+clutter_layout_manager_set_container
 
 <SUBSECTION>
 clutter_layout_manager_add_child_meta