Re: AudioNode GC rules

On Wed, Mar 20, 2013 at 7:48 AM, Robert O'Callahan <robert@ocallahan.org>wrote:

> On Wed, Mar 20, 2013 at 6:21 PM, Jussi Kalliokoski <
> jussi.kalliokoski@gmail.com> wrote:
>
>> Shouldn't we say that ("UAs can and should automatically prune out nodes
>> that can't contribute to future output"), at least? To make sure nodes that
>> can contribute don't get dropped out?
>
>
> There's an implicit frame axiom in all Web specs that the UA doesn't
> modify state unless some spec says it should. For example a
> standards-compliant UA should not randomly replace a Web page's DOM with a
> smiley-face image, even though no spec explicitly says it shouldn't.
>
> Thus, a UA that randomly removes nodes in a way affects output is just
> buggy and non-compliant with the Web Audio spec.
>

That's true, good point.

>
> Now for example WebKit's "bug" doesn't really seem to be a bug by the
>> spec, which has proven to be counter-intuitive for web developers that are
>> used to creating locally scoped DOM elements (nodes) that are added
>> (connected) to the tree (context), assigning listeners to them and assuming
>> they stay where you put them, even though you don't have a direct reference
>> to them.
>
>
> Per my above comments, if Webkit removes a node from the graph when the
> spec did not explicitly say it should, then it's buggy.
>
> Of course, unlike DOM, we don't have introspection that would let you find
>> the node you had earlier, but I don't think that's a very good thing either.
>
>
> It's actually really important that we never add that introspection. If we
> do, then the optimizations that remove nodes that can't produce output will
> become changes in observable behavior and we'll have to stop doing them!
>

Again a very good point, and I agree. As discussed much on the list and
calls, the best option is probably to let the javascript layer handle the
introspection if it's necessary.


> If we take all GC language out of the spec, then ScriptProcessorNodes
> which have event listeners attached and which are directly or indirectly
> connected to the destination will have to stay alive as long as they're
> connected. I think that's fine.
>

Agreed. Thanks for clearing this out for me.

Cheers,
Jussi


> Rob
> --
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>