Re: Canvas Visibility API

Thanks for bringing this up. I've also seen other requests e.g. this one
for iframe:
https://www.w3.org/Bugs/Public/show_bug.cgi?id=22931

We'll discuss this in our next call.

Arvind


On Tue, Aug 13, 2013 at 8:39 AM, Yury Delendik <ydelendik@mozilla.com>wrote:

> Hello,
>
> We have the following use case. The animation is performed at the specific
> frame rate and requires some computations be executed each frame. The frame
> painting is performed at requestAnimationFrame on the canvas and might take
> some time to do it, and it will be useful to not perform any painting at
> all to avoid unnecessary operations.
>
> Is there an interest to add an API similar to Page Visibility [1] to the
> DOM elements (at least for canvas elements)? Basically to allow scripts to
> query visibility state of the particular DOM element and receive event
> notifications when the element is about to be visible/hidden (or even, if
> possible, "near-the-view"). Also, in the past I met multiple cases where
> event notifications about elements visibility could help illuminate bulky
> JavaScript solutions using resize/scroll event handlers that use offsetLeft/
> **getBoundingClientRect/scrollX-**style checks (e.g. pdf.js [2] or
> floating headers).
>
> This proposal is somewhat similar to "support an element parameter to
> requestAnimationFrame()" issue [3]. However this solution doesn't let us to
> detect if the element is about to be hidden.
>
> Thank you,
> Yury Delendik
>
>   [1] https://dvcs.w3.org/hg/**webperf/raw-file/tip/specs/**
> PageVisibility/Overview.html<https://dvcs.w3.org/hg/webperf/raw-file/tip/specs/PageVisibility/Overview.html>
>   [2] http://mozilla.github.io/pdf.**js/web/viewer.html<http://mozilla.github.io/pdf.js/web/viewer.html>
>   [3] http://www.w3.org/2010/**webperf/track/issues/4<http://www.w3.org/2010/webperf/track/issues/4>
>   [4] https://bugzilla.mozilla.org/**show_bug.cgi?id=903575<https://bugzilla.mozilla.org/show_bug.cgi?id=903575>
>
>
>
>