[Bug 20246] Provide a system to observe nodes entering and leaving the viewport

https://www.w3.org/Bugs/Public/show_bug.cgi?id=20246

--- Comment #11 from Robert O'Callahan (Mozilla) <roc@ocallahan.org> ---
As Simon said, you don't necessarily want to know about the viewport. Instead,
browsers have "an area currently rendered" which is often larger than the
viewport to facilitate async scrolling. Exposing that to Web pages would be
useful.

An observer API for elements entering/exiting that could be useful. We've
already built something like that in Gecko for our own image decoding
optimizations, and we could probably leverage that.

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Received on Monday, 30 March 2015 23:11:44 UTC