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Re: What changes to Web Messaging spec are proposed? [Was: Re: Using ArrayBuffer as payload for binary data to/from Web Workers]

From: David Levin <levin@chromium.org>
Date: Wed, 8 Jun 2011 16:31:37 -0700
Message-ID: <BANLkTikhyS-Penz8ick6b10yopzr+UkYpQ@mail.gmail.com>
To: Kenneth Russell <kbr@google.com>
Cc: Arthur Barstow <art.barstow@nokia.com>, Andrew Wilson <atwilson@google.com>, Glenn Maynard <glenn@zewt.org>, Jonas Sicking <jonas@sicking.cc>, Dmitry Lomov <dslomov@google.com>, ben turner <bent.mozilla@gmail.com>, "public-webapps@w3.org" <public-webapps@w3.org>, Ian Hickson <ian@hixie.ch>, Travis Leithead <Travis.Leithead@microsoft.com>
ok.

On Wed, Jun 8, 2011 at 4:27 PM, Kenneth Russell <kbr@google.com> wrote:

> On Wed, Jun 8, 2011 at 2:39 PM, David Levin <levin@chromium.org> wrote:
> >
> >
> > On Wed, Jun 8, 2011 at 2:33 PM, Kenneth Russell <kbr@google.com> wrote:
> >>
> >> I prefer continuing to use an array for several reasons: simpler
> >> syntax, better type checking at the Web IDL level, and fewer
> >> ECMAScript-specific semantics.
> >
> > An array makes it harder to do future modifications.
>
> Possibly, but it makes the design of this modification cleaner.
>
> > Also with the array, how does "Enhance the ability to pass MessagePorts,
> so
> > that the object graph can refer to them as well" work? Specifically,
> > consider an array that contains [arrayBuffer1, port1]. Is port1 something
> in
> > the object graph or a port to be transfer as before?
>
> In order to maintain backward compatibility, the clone of port1 would
> show up in the "ports" attribute of the MessageEvent on the other
> side. Additionally, during the structured clone of the object graph,
> any references to port1 would be updated to point to the clone of
> port1. (The latter is new behavior, and brings MessagePorts in line
> with the desired transfer-of-ownership semantics.)
>
> All other objects in the array (which, as Ian originally proposed,
> would implement some interface like "Transferable" for better Web IDL
> type checking) would simply indicate objects in the graph to be
> transferred rather than copied.
>
> Note: it would still be possible to evolve the API to transfer all
> objects of a certain type. We would just need to change the type of
> the "ports" or "transfer" array from Transferable[] to any[] and spec
> what happens when a constructor function is placed in the array.
>
> -Ken
>
> > dave
> >
> >>
> >> -Ken
> >>
> >> On Wed, Jun 8, 2011 at 2:29 PM, David Levin <levin@chromium.org> wrote:
> >> >
> >> >
> >> > On Wed, Jun 8, 2011 at 2:24 PM, Kenneth Russell <kbr@google.com>
> wrote:
> >> >>
> >> >> My understanding is that we have reached a proposal which respecifies
> >> >> the "ports" argument to postMessage as an array of objects to
> >> >> transfer, in such a way that we:
> >> >
> >> > Array or object? (by object I mean: {transfer: [arrayBuffer1], ports:
> >> > [port]})
> >> >
> >> >>
> >> >>  - Maintain 100% backward compatibility
> >> >>  - Enhance the ability to pass MessagePorts, so that the object graph
> >> >> can refer to them as well
> >> >>  - Allow more object types to participate in transfer of ownership in
> >> >> the
> >> >> future
> >> >>
> >> >> To the best of my knowledge there are no active points of
> >> >> disagreement. I think we are only waiting for general consensus from
> >> >> all interested parties that this is the desired step to take.
> >> >>
> >> >> If it is, I would be happy to draft proposed edits to the associated
> >> >> specs; there are several, and the edits may be somewhat involved. I'd
> >> >> also be happy to share the work with Ian or anyone else.
> >> >>
> >> >> I don't know the various processes for web specs, but the Web
> >> >> Messaging spec will definitely need to be updated if we decide to
> move
> >> >> in this direction.
> >> >>
> >> >> -Ken
> >> >>
> >> >> On Wed, Jun 8, 2011 at 4:30 AM, Arthur Barstow <
> art.barstow@nokia.com>
> >> >> wrote:
> >> >> > Now that the responses on this thread have slowed, I would
> appreciate
> >> >> > if
> >> >> > the
> >> >> > participants would please summarize where they think we are on this
> >> >> > issue,
> >> >> > e.g. the points of agreement and disagreement, how to move forward,
> >> >> > etc.
> >> >> >
> >> >> > Also, coming back to the question in the subject (and I apologize
> if
> >> >> > my
> >> >> > premature subject change caused any confusion or problems), since
> we
> >> >> > have an
> >> >> > open CfC (ends June 9 [1]) to publish a Candidate Recommendation of
> >> >> > Web
> >> >> > Messaging, is the Messaging spec going to need to change to address
> >> >> > the
> >> >> > issues raised in this thread?
> >> >> >
> >> >> > -Art Barstow
> >> >> >
> >> >> > [1]
> >> >> >
> >> >> >
> http://lists.w3.org/Archives/Public/public-webapps/2011AprJun/0797.html
> >> >> >
> >> >
> >
> >
>
Received on Wednesday, 8 June 2011 23:32:23 GMT

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