[cairo] reference counting vs garbage collection

[Carl Worth]

On Mon, 03 Jan 2005 00:48:11 +0100 (CET), Olivier Andrieu wrote:
> The problem is that such surfaces use two kinds of resources: the
> memory (with reference counts) and the FILE*. Garbage collectors
> automatically manage memory but not other kind of resources.

Thanks for pointing out this distinction in resource classes.

> There could be two functions I think: _destroy (which should rather be
> named _unref) to manage the memory and _close to indicate that the
> file resource is not to be used anymore. That's more or less how GTK+
> work for instance and it works very well with language bindings. When
> _close() is called, cairo would flush file-based surfaces, and set a
> flag to indicate nothing should be done on this surface
> anymore. _unref() decreases the refcount and when it reaches zero, it
> calls _close() and then frees the memory.

The proposal of _unref()/_close() matches the resource classification
above. However, it doesn't capture the inherent dependency between the
two resources. Namely, after finalizing internal state such as FILE*
with _close() there's nothing useful for the user to do other than
_unref(). And it doesn't seem useful to expose this inert object state
to the user, (although the implementation may need it internally).

So, I propose an _unref() function as above, and a _destroy() function
which is equivalent to the pair of _close() and _unref() as described
above.

Does that seem workable? Or am I still totally missing some
GC-language binding issues?

-Carl