Ref-Countable Non-Item Objects

• Ref-countable non-item objects (e.g. a function closure) are avoided where possible (at least in terms of being exposed to the user). If they are still required in places, one of two things should be done about them.

• Ref-countable non-item objects are "attached" to items, in a manner similar to the parent->child relationship, so there's always only a single point of dangling references, i.e. the top-level canvas.

• Ref-countable non-item objects are fully hidden from the user, so the user only deals with copyable value objects which wrap the actual ref-counted object. An example is std::string or the FooPtr/FooVar wrapper types provided by many IDL implementations.