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Re: postMessage is the new wtf

From: Rick Waldron <waldron.rick@gmail.com>
Date: Tue, 13 Dec 2011 14:59:13 -0500
Message-ID: <CAHfnhfqSkcQnK48+Q3NQXMACoS1JfHr_DFEUssVUDj5BdQRzLg@mail.gmail.com>
To: Dmitry Lomov <dslomov@chromium.org>
Cc: Webapps WG <public-webapps@w3.org>
On Tue, Dec 13, 2011 at 2:11 PM, Dmitry Lomov <dslomov@chromium.org> wrote:

> Hi Rick,
> here are some clarifications.
>
> There were many (long!) discussions on public-webapps about the new
> signature for postMessage:
> http://lists.w3.org/Archives/Public/public-webapps/2011AprJun/thread.html
> http://lists.w3.org/Archives/Public/public-webapps/2011AprJun/0304.html
> http://lists.w3.org/Archives/Public/public-webapps/2011AprJun/0805.html
> http://lists.w3.org/Archives/Public/public-webapps/2011AprJun/0985.html
>

I appreciate these links and to clarify, I wasn't subscribed to this last
in April of 2011, so my search started here:

https://www.google.com/search?gcx=c&sourceid=chrome&ie=UTF-8&q=postmessage+api+change

...Among several other similar searches. I promise this wasn't a case of
"just not looking", so again, thank you for providing the links



> window.webkitPostMessage(msg, transferables) does not really exist (it is
> an error in the blog post, and I am told the post will be amended). What
> exists is window.webkitPostMessage(msg, targetOrigin, transferables).
>

This supports the subject line "postMessage is the new wtf"



> Regarding second argument to worker.(webkit)postMessage, this is the new
> spec for it:
> http://www.whatwg.org/specs/web-apps/current-work/multipage/workers.html#dedicated-workers-and-the-dedicatedworkerglobalscope-interface
> .
>

Thank you, please see [2]



>
> The spec mandates 'void postMessage(any message, optional
> sequence<Transferable> transfer)'. Transferable includes both MessagePorts
> and ArrayBuffers, so in the new spec the transfer argument to postMessage
> may be a mix of both types, and a backwards-compat extension to what we had
> before (sequence<MessagePort> aka MessagePortArray). Note that message
> ports got an additional change in semantics, and can now be mentioned in
> the message as well - both
>
   worker.postMessage({p:port}, [port])
> and
>    worker.postMessage({p:port, ab:arrayBuffer}, [post, arrayBuffer])
> work. Therefore this extension to postMessage semantics is both
> backwards-compatible and consistent.
>

Can you provide a reference for this? I'm unable to locate anything that
covers these semantics.



> On the receiving side, the 'ports' property of event object will still
> contain only the message ports from the transfer list, so that behavior is
> preserved as well.
>

Great!


>
> I hope this helps,
> Thanks,
> Dmitry
>
>
>
> On Tue, Dec 13, 2011 at 8:24 AM, Rick Waldron <waldron.rick@gmail.com>wrote:
>
>> Following the recent blog post
>> http://updates.html5rocks.com/2011/12/Transferable-Objects-Lightning-Fastand subsequent Twitter discussion regarding changes to the parameter list
>> of:
>>
>> Worker.prototype.postMessage( message [, transfer ] ) [1]
>>
>> DedicatedWorkerGlobalScope void postMessage<http://dev.w3.org/html5/workers/#dom-dedicatedworkerglobalscope-postmessage>(any
>> message, optional sequence<Transferable> transfer) [2][3]
>>
>>
>> I'm unable to find documentation or discussion that would clarify the
>> rationale of over-using and over-loading the "postMessage" Identifier;
>> considering the the blog cited above shows this example:
>>
>> [window|worker].webkitPostMessage(uInt8Array.buffer, [uInt8Array.buffer
>> ]);
>>
>>  which conflicts with:
>>
>> window.postMessage(message, targetOrigin [, transfer ]) [4][5]
>>
>> and they both conflict with:
>>
>> DedicatedWorkerGlobalScope : WorkerGlobalScope ...
>>  void postMessage(in any message, in optional MessagePortArray ports); [6]
>>
>> Currently, passing a second arg to worker.postMessage(), that is not a
>> MessagePortArray raises
>> "Uncaught TypeError: MessagePortArray argument must contain only
>> MessagePorts" in Chrome and "Could not get domain" warning in Firefox.
>>
>>
>> Any reasonable clarification would be greatly appreciated.
>>
>> Thanks in advance
>>
>> Rick
>>
>>
>> [1]
>> http://www.whatwg.org/specs/web-apps/current-work/multipage/workers.html#dedicated-workers-and-the-worker-interface
>>
>> [2]
>> http://www.whatwg.org/specs/web-apps/current-work/multipage/workers.html#dedicated-workers-and-the-dedicatedworkerglobalscope-interface
>>
>> [3]
>> http://dev.w3.org/html5/workers/#dedicated-workers-and-the-dedicatedworkerglobalscope-interface
>>
>> [4]
>> http://www.whatwg.org/specs/web-apps/current-work/multipage/web-messaging.html#web-messaging
>>
>> [5]
>> http://www.whatwg.org/specs/web-apps/current-work/multipage/web-messaging.html#posting-messages
>>
>> [6] PREVIOUS SPECIFICATION STATE!!!
>> http://www.w3.org/TR/2011/WD-workers-20110208/#dedicated-workers-and-the-dedicatedworkerglobalscope-interface
>>
>
>
Received on Tuesday, 13 December 2011 20:07:01 GMT

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