[webkit-dev] Position on emerging standard: video.requestAnimationFrame()

[Philip Jägenstedt]

Hi Simon,

Naming is hard as usual and was discussed on
https://github.com/w3ctag/design-reviews/issues/429, where you've already
commented.

Is there a pair of names that you think would work better
here? onFrameAvailable() would IMHO be quite unidiomatic, the web platform
doesn't have any other onFoo() methods, and what would the "cancel" variant
be called?

Can you file an issue in https://github.com/WICG/video-raf/issues if you
see a good alternative?

Also curious if +Eric Carlson <eric.carlson at apple.com> has any feedback on
this?

On Wed, Jan 22, 2020 at 10:49 PM Simon Fraser <simon.fraser at apple.com>
wrote:

>
> On Jan 21, 2020, at 5:27 PM, Thomas Guilbert <tguilbert at google.com> wrote:
>
> The idea was to reuse an API name that developers are already
> familiar with, in a similar context. The name is also being used in
> XRSession (
> https://developer.mozilla.org/en-US/docs/Web/API/XRSession/requestAnimationFrame),
> and in OffscreenCanvas (or technically DedicatedWorkerGlobalScope). The AnimationFrameProvider
> mixin
> <https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#animationframeprovider> could
> also be updated so HTMLVideoElement can extend it.
>
> Yes, this isn't formally spec'ed out, but it will be. For now, they are
> added to the task queue and run like any other task. So, going off the spec
> you linked, I think this would be "5) Perform oldestTask's step"  and not
> "10) Rendering: [...] 11. Foreach document run animation frame callbacks
> for that Document".
>
>
> I would expect something that's called "requestAnimationFrame" to only
> fire in the "update the rendering" steps; requestAnimationFrame is a
> "before rendering" callback. So firing a callback with the same name at
> other times seems like it will lead to author confusion.
>
> The author's expectation should be that any content/style changes they
> make inside a requestAnimationFrame callback will appear on-screen in the
> same frame as other changes in the same event loop cycle, and that
> requestAnimationFrame won't be called more often than is necessary to
> update the screen at the appropriate frame rate.
>
> Simon
>
>
> On Tue, Jan 21, 2020 at 1:01 PM Simon Fraser <simon.fraser at apple.com>
> wrote:
>
>> On Jan 21, 2020, at 12:37 PM, Thomas Guilbert <tguilbert at google.com>
>> wrote:
>>
>> Hello,
>>
>> I'm reaching out to see if webkit would like to weigh in on the following proposal:https://discourse.wicg.io/t/proposal-video-requestanimationframe/3691
>>
>> The HTMLVideoElement.requestAnimationFrame() API allows web developers to be notified when a video frame has been presented for composition, and provides metadata for that frame.
>>
>> If you want to try it out, a prototype is available in Chromium Dev,
>> behind the enable-experimental-web-platform-features flag.
>>
>>
>> This is not official feedback, but I have some issues with the proposal.
>>
>> First, the name is confusing. It sounds like you're requesting a frame
>> from the video, but it's really a "frame available" callback. Why not call
>> it onFrameAvailable()?
>>
>> Second, its interaction with normal requestAnimationFrame() and the HTML
>> event loop needs to be better defined. Where in in the
>> https://html.spec.whatwg.org/multipage/webappapis.html#event-loop-processing-model do
>> these callbacks fire?
>>
>> Simon
>>
>>
>>
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