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[RequestAnimationFrame] Processing model does not permit handling animation callbacks for multiple documents at once

From: Boris Zbarsky <bzbarsky@MIT.EDU>
Date: Tue, 06 Dec 2011 23:18:05 -0500
Message-ID: <4EDEE8FD.9010405@mit.edu>
To: public-web-perf@w3.org
In at least Gecko's implementation, all documents in a given tab are 
treated in an atomic manner for purposes of animation callbacks, in the 
sense that all the callbacks from all those lists are placed into a 
single list, then all the document-level lists are cleared, and then the 
callbacks are processed.

This is generally desirable (just like compositing them all at once is 
desirable) because otherwise you can get tearing when translucent 
iframes update animations at a different time from the main document.

Unfortunately, the processing model does not seem to allow this.  It's 
not even clear to me whether it allows calling animation callbacks for 
multiple documents one after the other from the same task (which is 
something we could do in Gecko that would still prevent the tearing 
issue but be closer to the processing model as the spec defines it now, 
in that one document's callback list would not be cleared until 
another's were done processing).

Thoughts?

-Boris
Received on Wednesday, 7 December 2011 04:18:43 UTC

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