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Re: [whatwg] Reviving ImageBitmap options: Intend to spec and implement

From: Kenneth Russell <kbr@google.com>
Date: Wed, 10 Feb 2016 16:26:10 -0800
Message-ID: <CAMYvS2f-J24MVL4dN0KAS+mVLBG70YCMj3z_Gcs4hcVaiFSs3g@mail.gmail.com>
To: Justin Novosad <junov@google.com>
Cc: whatwg <whatwg@lists.whatwg.org>, Boris Zbarsky <bzbarsky@mit.edu>
On Wed, Feb 10, 2016 at 12:06 PM, Justin Novosad <junov@google.com> wrote:

> On Wed, Feb 10, 2016 at 2:29 PM, Boris Zbarsky <bzbarsky@mit.edu> wrote:
>
> > On 2/10/16 1:25 PM, Domenic Denicola wrote:
> >
> >> In new JavaScript-only APIs we've made the decision to move away from
> the
> >> potentially-confusing HTML style crossOrigin enums in favor of the
> >> RequestCredentials enum used by Fetch:
> >> https://fetch.spec.whatwg.org/#requestcredentials. You can see this in
> >> e.g. https://github.com/whatwg/html/pull/608 where I chose the same
> >> initial crossOrigin design and Anne convinced me to move to
> credentials. I
> >> imagine we'll continue to use crossorigin="" and corresponding reflected
> >> crossOrigin IDL attributes for any HTML elements, but for JS-only APIs
> >> RequestCredentials is the way to go.
> >>
> >
> > That's not _quite_ the same thing.  The HTML setup basically lets you
> > specify one of:
> >
> > 1)  No CORS (attr not set).
> > 2)  CORS, RequestCredentials == "include" (crossrigin="use-credentials")
> > 3)  CORS, RequestCredentials == "same-origin" (any other attr value)
> >
> > Note that in the pull request you reference your default was not actually
> > any of those situations, as far as I can tell, so I agree that using
> > "crossOrigin" there was not a good fit.  But for the ImageBitmap case, we
> > do want to support case 1 above, at least assuming tainted ImageBitmap
> is a
> > thing.  If it's not, then I agree that just a RequestCredentials value is
> > probably sufficient and all the loads involved should use CORS.
> >
>
> Tainted ImageBitmaps is a thing: https://github.com/whatwg/html/pull/385
> That said, this is not one of the options we intend to move forward with in
> the near term (It is not in the highly desired list). It is not clear that
> the feature is even needed. I am no CORS expert, but I think you can get an
> untainted ImageBitmap from a cross-origin image by using: XHR (with
> credentials) -> blob -> createImageBitmap
>

Agreed -- I don't think the ImageBitmap constructor from URL, or the
crossOrigin ImageBitmap constructor argument, are needed any more. It would
be good to fully implement ImageBitmap (including asynchronous decoding),
plus some of the WebGL-related constructor arguments, and verify that the
texture uploads are much faster. At that point let's delete the crossOrigin
ImageBitmap constructor argument, and the proposal for creating
ImageBitmaps from URLs.

-Ken




>
>
> > That said, the actual phrasing around "crossOrigin" in
> > https://wiki.whatwg.org/wiki/ImageBitmap_Options doesn't make much sense
> > (e.g. it in fact is not a "CORS settings attribute" because it's not a
> > markup attribute at all).  But we can wordsmith it better once we agree
> on
> > what we actually want it to do.
> >
> > -Boris
> >
>
Received on Thursday, 11 February 2016 00:26:41 UTC

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