[cairo] reference counting vs garbage collection

[Keith Packard]

Around 12 o'clock on Jan 5, Olivier Andrieu wrote:

> ah but why do an _unref in _destroy ? This way the binding has to keep
> track of wether _destroy was called, so that it knows wether to _unref
> or not when the object is collected.

We're trying to preserve the symmetry for non-GC'd languages as well. We 
want:

	x = _create 
	...
	_destroy (x)

to "just work".  Assymmetry in a non-GC'd language invariably leads to 
even more memory allocation bugs.

For your case, where you just want _destroy to close the object and not 
dereference it, you can use

	_ref (x)
	_destroy (x)

and then in the finalizer, you can do

	_unref (x)

which will have precisely the desired effect.

For my own part, as I want to know when I can finalize both the surface 
and any associated FILE object, I will use _destroy from the surface finalizer 
right before a call to fclose.

-keith


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