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Difference between revisions of "RemoteDocumentMessaging"

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<pre>
 
<pre>
partial interface Window {
+
[Constructor(DOMString name)]
     MessagePort connectTo(DOMString target);
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interface BroadcastChannel : EventTarget {
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     void postMessage(any message);
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    void close();
 +
 
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    attribute EventHandler onmessage;
 
};
 
};
 
</pre>
 
</pre>
 
The <code>connectTo</code> method opens a message port to a browsing context with name <code>target</code> within the caller's origin (although not necessarily within the caller's unit of related browsing contexts).
 
 
# Create a new MessagePort object owned by the global object of the incumbent script. Let this be the initiator's port.
 
# Return the initiator's port and perform the remaining steps asynchronously.
 
# Spin the event loop until a browsing context with name <code>target</code> has the same effective script origin as the incumbent script has an active document whose ready state has reached "interactive".  Let this document be the responder's document.
 
# Create a new MessagePort object owned by the global object of the responder's document. Let this be the responder's port.
 
# Entangle the initiator's port and the responder's port.
 
# Create a trusted event that uses the MessageEvent interface, with the name connect, which does not bubble, is not cancelable, has no default action, has a data attribute whose value is initialized to the empty string, has a ports attribute whose value is initialized to a read only array containing only the responder's port, and has a source attribute whose value is initialized to the responder's port, and queue a task to dispatch the event at global object of the responder's document.
 
  
 
==Examples==
 
==Examples==
  
 
<pre>
 
<pre>
var channel = new BroadcastChannel("channel-name");
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// The channel name, "deep-thoughts", is scoped to the current origin.
 +
var channel = new BroadcastChannel("deep-thoughts");
  
 
channel.addEventListener("message", function(message) {
 
channel.addEventListener("message", function(message) {
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channel.postMessage("I think, therefore I am.");
 
channel.postMessage("I think, therefore I am.");
 
</pre>
 
</pre>
 +
 +
==Notes==
 +
 +
You can already accomplish this through localStorage as that broadcasts storage events: http://bens.me.uk/2013/localstorage-inter-window-messaging Something that does not involve synchronous IO would probably be better though.
  
 
[[Category:Proposals]]
 
[[Category:Proposals]]

Latest revision as of 03:20, 23 June 2013

Overview

This document describes a proposal for discovering and communicating with "remote" documents. In particular, this proposal lets a web page communicate with another document even if the web page does not have a direct script connection to that document.

Use Cases

The user opens the same word processing document hosted by a document editing web site in two different browser windows. The document editing web site wants to ensure that edits in one window a reflected in the other window without needing to round-trip through the server (e.g., because the user is offline). Unfortunately, the documents are in different units of related browsing contexts, which means the two documents cannot form a direct script connection. Using remote document messaging, the two documents can discover each other and update each other about edits performed by the user.

Specification

[Constructor(DOMString name)]
interface BroadcastChannel : EventTarget {
    void postMessage(any message);
    void close();

    attribute EventHandler onmessage;
};

Examples

// The channel name, "deep-thoughts", is scoped to the current origin.
var channel = new BroadcastChannel("deep-thoughts");

channel.addEventListener("message", function(message) {
  // Do something interesting with |message|, which is a MessageEvent.
}, false);

// Send a message to each other BroadcastChannel instance with the same channel
// name in the same origin.
channel.postMessage("I think, therefore I am.");

Notes

You can already accomplish this through localStorage as that broadcasts storage events: http://bens.me.uk/2013/localstorage-inter-window-messaging Something that does not involve synchronous IO would probably be better though.