[whatwg] Canvas in workers

Kenneth Russell kbr at google.com
Wed Oct 16 13:23:52 PDT 2013

On Wed, Oct 16, 2013 at 1:13 PM, Justin Novosad <junov at google.com> wrote:
> On Wed, Oct 16, 2013 at 3:53 PM, Robert O'Callahan <robert at ocallahan.org>
> wrote:
>> On Thu, Oct 17, 2013 at 6:35 AM, Kenneth Russell <kbr at google.com> wrote:
>>> Yes, right. That factory method is already spec'ed on the
>>> WorkerGlobalScope [1]. It actually returns a Promise, so presumably
>>> transferToImageBitmap would have to as well.
>> The whole point of transferToImageBitmap is that it's really fast, so I
>> don't see why it has to be async.
> True. I also wonder why all of the currently spec'ed ImageBitmap creation
> methods are async. I think asynchrony makes sense when creating ImageBitmaps
> from blobs, image elements and video elements, which may not be in an
> immediately accessible state, but creating an ImageBitmap from a Canvas or
> canvas context (or a WorkerCanvas) could be immediate.

It would be fine in my opinion for transferToImageBitmap to simply
return an ImageBitmap. The suggestion to return a Promise was merely
for symmetry with createImageBitmap.

While the Promise returned from createImageBitmap(HTMLCanvasElement)
can be fulfilled immediately, is it worth introducing a special
overload with a different return type?


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