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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Implement IntersectionObserver support"
href="https://bugs.webkit.org/show_bug.cgi?id=159475">159475</a>
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<th>Summary</th>
<td>Implement IntersectionObserver support
</td>
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<th>Classification</th>
<td>Unclassified
</td>
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<th>Product</th>
<td>WebKit
</td>
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<th>Version</th>
<td>Safari Technology Preview
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<th>Hardware</th>
<td>All
</td>
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>Enhancement
</td>
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<th>Priority</th>
<td>P2
</td>
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<th>Component</th>
<td>Frames
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<th>Assignee</th>
<td>webkit-unassigned@lists.webkit.org
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<th>Reporter</th>
<td>jeffreytgilbert@gmail.com
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<pre>Working draft for implementation:
<a href="https://wicg.github.io/IntersectionObserver/">https://wicg.github.io/IntersectionObserver/</a>
Intent to implement in Firefox by version 50
<a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1243846">https://bugzilla.mozilla.org/show_bug.cgi?id=1243846</a>
<a href="https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API">https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API</a>
Chrome adopted IntersectionObserver support in version 51
<a href="https://www.chromestatus.com/feature/5695342691483648">https://www.chromestatus.com/feature/5695342691483648</a>
<a href="https://chromium.googlesource.com/chromium/src/third_party/+/master/WebKit/Source/core/dom/IntersectionObserver.cpp">https://chromium.googlesource.com/chromium/src/third_party/+/master/WebKit/Source/core/dom/IntersectionObserver.cpp</a>
MS Edge has committed to adopting support, but have not implemented yet
<a href="https://developer.microsoft.com/en-us/microsoft-edge/platform/status/intersectionobserver">https://developer.microsoft.com/en-us/microsoft-edge/platform/status/intersectionobserver</a>
<a href="https://wpdev.uservoice.com/forums/257854-microsoft-edge-developer/suggestions/13407852-intersectionobserver">https://wpdev.uservoice.com/forums/257854-microsoft-edge-developer/suggestions/13407852-intersectionobserver</a>
Rationale:
Advertisements typically use Flash, frame per second counters, or costly geometry calculations within loops to determine if an ad is in view or not. The mechanisms are difficult to implement, non-standardized, and costly to web performance. The IAB, MRC, browser vendors, and web standards bodies have attempted to solve for this by introducing first the PageVisibility 2 API draft, and now splintered off from that, the IntersectionObserver API. This pattern allows for efficient event driven code to take advantage of indicators sent directly from the browser of the area of a page or more importantly sandboxed iframe which are viewable without requiring access to the parent documents information or leaking important security details.
Chrome has introduced this early as a way of hastening the elimination of the Flash browser plugin as a necessary evil, which they plan to throttle by default at the end of the year. Firefox's intention is to introduce this functionality as part of version 50, currently in nightlies. Microsoft has commented to the IAB that they intend to introduce the functionality, but have not committed to a build version or date for releasing it. That leaves only Safari/Webkit based browsers left. This solves an obvious problem for advertisers and consumers/end users who want transparency and performance, respectively.</pre>
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