Intent to Implement: BroadcastChannel

[ian...@chromium.org]

Contact emails

ian...@chromium.org, jsb...@chromium.org

Spec

http://www.whatwg.org/specs/web-apps/current-work/multipage/web-messaging.html#broadcasting-to-other-browsing-contexts

Summary

BroadcastChannel allows scripts from the same origin but other browsing contexts to send each other messages. Channels are scoped to an origin and have a name, messages posted to a channel will be delivered to all listeners of that channel in all documents. There’s already a Chromium bug for this: http://crbug.com/161070

SharedWorker allows same-origin messaging but with extra process/thread overhead and script plumbing.

Motivation

Existing cross-document messaging relies documents having references to each other. Communication between two pages on the same origin is possible through less efficient and less expressive means such as cookies, local databases, server round-trips, SharedWorker or Flash’s LocalConnection. MessageChannel can be used, but only if the documents can bootstrap the channel somehow. Use cases include simply notifying other tabs when a user logs in or out so that they can refresh, coordinating multimedia playback so that background tabs can pause when a user requests playback in a foreground tab, and coordinating the use of storage resources.

Compatibility Risk

The compatibility risk is low. This exposes a new, extremely simple interface rather than modifying an existing one. Mozilla is currently implementing this (https://bugzilla.mozilla.org/show_bug.cgi?id=966439) and there are some spec clarifications (http://bit.ly/1vTCQLE) coming out of that process.

Internet Explorer: No signals

Safari: No signals

Ongoing technical constraints

None

Will this feature be supported on all five Blink platforms (Windows, Mac, Linux, Chrome OS and Android)?

Yes.

OWP launch tracking bug?

None yet.

Link to entry on the feature dashboard

http://www.chromestatus.com/features/4585496197988352

Requesting approval to ship?

No

[Marijn Kruisselbrink]

As an update to this intent (which didn't actually get implemented when originally send out two years ago), I'm planning to take over implementing this feature.

[PhistucK]

One thing to note is that Firefox shipped it.

☆PhistucK

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