[whatwg] Workers in HTML5 (was: postMessage apply(), pipe, etc.)

Aaron Boodman aa at google.com
Thu Feb 14 17:44:24 PST 2008

On Thu, Feb 14, 2008 at 3:05 PM, Geoffrey Garen <ggaren at apple.com> wrote:
> > Since postMessage API is looking more an more like the Gears worker
>  > messaging API (or better), can we go one step further and introduce
>  > workers into the HTML5, defined as invisible windows with limited
>  > capabilities:
>  Why call these "windows" at all? They seem to have no relationship
>  physical windows, or the JavaScript "window" object.

No relation. It might be easier for some developers to get it if
associated with the window. I think it's a bit of a rough metaphor
myself, and did not call the object Window in my proposal, but

>  > WorkerWindow openWorker(in DOMString url);
>  Can I supply a URL to an HTML file here? Does the file load and parse
>  as an HTML document? Is the document accessible to the worker?

No the content of the URL must be JavaScript. In fact it must be
JavaScript intended to be used in a worker to do anything useful.

>  Since the whole point of the worker is to do JavaScript work, should
>  this string be a script instead of a URL?

This is how Gears used to work and it was very inconvenient. Web apps
do not really have access to their source code as a string
conveniently. They could use XHR to request a script file and then
send it into the worker,but why make them do this?

>  How do I pass data to a worker?

Please see either Ian's or my proposal earlier in this thread for an
example of how this could work. Basically, like postMessage().

>  Is there an API contract regarding synchronization and/or order of
>  execution?

I think that the API should guarantee that the script is executed on
another thread. I don't think that the API should guarantee that
anything has happened when createWorker*() returns, as UA's will want
to load the script file asynchronously.

However, I think that developers should be able to start sending
messages to workers immediately, before the worker has loaded. These
messages should be queued and delivered when the worker loads.

- a

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