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Re: requestAnimationFrame

From: Doug Schepers <schepers@w3.org>
Date: Sun, 28 Nov 2010 18:29:40 -0500
Message-ID: <4CF2E5E4.4010204@w3.org>
To: "public-webapps@w3.org" <public-webapps@w3.org>
CC: "Gregg Tavares (wrk)" <gman@google.com>
Hi, folks-

This is just a quick note to let you all know that the topic of APIs for 
animation, both scripted and declarative, is one of the things that the 
FX Task Force [1] (a joint task force between the CSS and SVG WGs) is 
looking at, so we are following this thread with interest.

 From a Recommendation-track spec perspective, animation (and by 
extension, animation APIs and timing stuff) are already in scope for 
those groups, so we would like to standardize things there; obviously, 
we would want the continued participation of the WebApps WG participants 
as well.  (I prefer to avoid more painful chartering discussions.)

I'm not trying to cut off conversation here, I just wanted to make sure 
people were aware.

[1] http://www.w3.org/Graphics/fx/

Regards-
-Doug Schepers
W3C Team Contact, SVG, WebApps, and Web Events WGs


Gregg Tavares (wrk) wrote (on 11/15/10 6:03 PM):
> following in the footsteps of a previous thread
> http://lists.w3.org/Archives/Public/public-webapps/2009OctDec/0223.html
>
> I'd like to see if there is some consensus on this issue. Various people
> are anxious to see this happen in more browsers.
>
> A couple of questions came up for requestAnimationFrame
> (see
> http://weblogs.mozillazine.org/roc/archives/2010/08/mozrequestanima.html)
>
> One is, how should this api be used if I want an app to update at 10hz.
>   It seems to be designed to assume I want the maximum frame rate. If I
> want to run slower would I just use
>
> setInterval(function() {
>     window.requestAnimationFrame();
>    }, 100); // request frames at 10hz?
>
> That's fine if that's the answer
>
> But that brings up the next question. I'm in some alternate world where
> there is no Flash, instead all ads are implemented in Canvas. Therefore
> a site like cnn.com <http://cnn.com> or msnbc.com <http://msnbc.com> has
> 5 canvases running ads in each one.  I don't really want all 5 canvases
> redrawn if they are not on the screen but the current design has
> requestAnimationFrame and beforePaint to be window level apis.
>
> That seems to have 2 issues.
>
> 1) All of them will get a beforePaint event even if most or all of them
> are scrolled off the visible area since there is only 1 beforePaint
> event attached to the window.
>
> 2) All of them will get beforePaint events at the speed of the fastest
> one. If one ad only needs to update at 5hz and other updates at 60hz
> both will update at 60hz.
>
> Do those issues matter? If they do matter would making both
> requestAnimationFrame and beforePaint be element level APIs solve it?
>
>
Received on Sunday, 28 November 2010 23:29:43 GMT

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