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Re: [whatwg] Proposal: createImageBitmap should return a "Promise" instead of using a callback

From: Justin Novosad <junov@google.com>
Date: Wed, 17 Jul 2013 19:21:53 -0400
Message-ID: <CABpaAqR1O4CqvD7peUU=A9OaocsSj1kqV_dSboZoZw+gg1rd=g@mail.gmail.com>
To: Ian Hickson <ian@hixie.ch>
Cc: Silvia Pfeiffer <silviapfeiffer1@gmail.com>, WHAT Working Group <whatwg@whatwg.org>
On Wed, Jul 17, 2013 at 6:54 PM, Ian Hickson <ian@hixie.ch> wrote:

> On Thu, 18 Jul 2013, Silvia Pfeiffer wrote:
> > At the same time, I think we should follow a clear pattern for
> > introducing a Promise based API, which the .create() approach would
> > provide.
>
> I don't understand what that means.
>

I think the concern is about the case where we end up with legacy callback
Factory methods that co-exist new with Promise-based flavors of the factory
methods. There's no technical obstacle to having the two co-exist with the
same name, it's just an overload.  I guess the concern is more about code
readability.  Is that it?

> I guess I'm asking for JS dev input here...
>
> Promises are just regular callbacks, with the synchronisation done by the
> browser (or shim library) rather than by author code. I don't really
> understand the problem here.
>

Yes. In the case of createImageBitmap the resolver would be built-in to the
promise by the browser, so there is nothing to set-up. Devs who are not
ready to fully embrace Promises can use this API the same way they would a
callback API, but with a slightly different syntax:

Not too scary IMHO


> --
> Ian Hickson               U+1047E                )\._.,--....,'``.    fL
> http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
> Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
>
Received on Wednesday, 17 July 2013 23:22:20 UTC

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