/**
Detaches all children from the sizer.
+
If @a delete_windows is @true then child windows will also be deleted.
+
+ Notice that child sizers are always deleted, as a general consequence
+ of the principle that sizers own their sizer children, but don't own
+ their window children (because they are already owned by their parent
+ windows).
*/
virtual void Clear(bool delete_windows = false);