Fwd: Intent to Implement: Intersection Observer

Hey all, fyi... Still in early stages, but this is *highly* relevant to the
many use cases we've discussed on this list around deferred loading,
element visibility, etc. For a more hands-on overview, check out the
explainer:
https://github.com/slightlyoff/IntersectionObserver/blob/master/explainer.md

Feedback & issues:
https://github.com/slightlyoff/IntersectionObserver/issues

ig

---------- Forwarded message ----------
From: Michael Blain <mpb@chromium.org>
Date: Tue, Oct 6, 2015 at 9:10 PM
Subject: Intent to Implement: Intersection Observer
To: blink-dev@chromium.org


*Contact emails*
mpb@chromium.org, ojan@chromium.org

*Spec*
https://rawgit.com/slightlyoff/IntersectionObserver/master/index.html

*Summary*
This specification describes an API that can be used to understand the
visibility and position of DOM elements relative to a viewport. The
position is delivered asynchronously and is useful for understanding the
visibility of elements and implementing pre-loading and deferred loading of
DOM content.
https://github.com/slightlyoff/IntersectionObserver/blob/master/explainer.md


*Motivation*
Accurately measuring viewability is important for several use cases;
deferred-loading or lazy-loading of content, infinite-scroll lists and
advertising. Because there is no standard way to get viewable information
across browsers, developers have built and rely on a series of
browser-specific hacks and workarounds. Sites rely on scroll handlers and
plugins in situations where they really aren't necessary, impacting
performance. Intersection Observer addresses this need by introducing a new
API to asynchronously report on the relative positions of elements without
interrupting the critical paths of rendering or processing.

*Compatibility Risk*
Low. The rough API and use cases were received positively when meeting with
other browser vendors in Paris in August. Some of the decisions around
behaviors of edge cases need a fresh review though. Notes from Paris:
http://www.w3.org/2015/08/27-positionobserver-irc

*Ongoing technical constraints*
None.

*Will this feature be supported on all six Blink platforms (Windows, Mac,
Linux, Chrome OS, Android, and Android WebView)? Yes or no. *
Yes

*OWP launch tracking bug*
http://crbug.com/540528

*Link to entry on the Chrome Platform Status*
https://www.chromestatus.com/features/5695342691483648
<https://www.chromestatus.com/features/5695342691483648>

*Requesting approval to ship?*
No.