Re: AudioNode GC rules

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.

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!

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.

Rob
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