[StBoxLayout] Add st_box_layout_remove_all, st_box_layout_destroy_children

In a variety of places we're using boxes as data-modeling displays,
and in doing so we often want to either remove the children or
explictly destroy them.

Now ideally Gjs would support callbacks, and this would make using
the for_each functions possible, but even then these functions
are more efficient and shorter to type, at least.

https://bugzilla.gnome.org/show_bug.cgi?id=600734

src/st/st-box-layout.c

@@ -1338,3 +1338,50 @@ st_box_layout_get_pack_start (StBoxLayout *box)
 
   return box->priv->is_pack_start;
 }
+
+static void
+st_box_layout_internal_remove_all (StBoxLayout *self,
+                                   gboolean     destroy)
+{
+  StBoxLayoutPrivate *priv = ST_BOX_LAYOUT (self)->priv;
+  ClutterActor *child;
+
+  while (priv->children)
+    {
+      child = priv->children->data;
+
+      g_object_ref (child);
+      priv->children = g_list_delete_link (priv->children, priv->children);
+      clutter_actor_unparent (child);
+      g_signal_emit_by_name (self, "actor-removed", child);
+      if (destroy)
+        clutter_actor_destroy (child);
+      g_object_unref (child);
+    }
+
+  clutter_actor_queue_relayout ((ClutterActor*) self);
+}
+
+/**
+ * st_box_layout_remove_all:
+ * @self:
+ *
+ * Efficiently unparent all children currently in this box.
+ */
+void
+st_box_layout_remove_all (StBoxLayout *self)
+{
+  st_box_layout_internal_remove_all (self, FALSE);
+}
+
+/**
+ * st_box_layout_destroy_children:
+ * @self:
+ *
+ * Efficiently unparent and destroy all children currently in this box.
+ */
+void
+st_box_layout_destroy_children (StBoxLayout *self)
+{
+  st_box_layout_internal_remove_all (self, TRUE);
+}

src/st/st-box-layout.h

@@ -89,6 +89,10 @@ void     st_box_layout_set_pack_start (StBoxLayout *box,
                                        gboolean     pack_start);
 gboolean st_box_layout_get_pack_start (StBoxLayout *box);
 
+void     st_box_layout_remove_all     (StBoxLayout *box);
+
+void     st_box_layout_destroy_children (StBoxLayout *box);
+
 G_END_DECLS
 
 #endif /* _ST_BOX_LAYOUT_H */