Annotation of html5/workers/Overview.html, revision 1.228
1.155 ihickson 1: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><!-- when publishing, change bits marked ZZZ --><html lang="en-US-x-Hixie"><title>Web Workers</title><style type="text/css">
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1.82 ihickson 67:
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1.82 ihickson 75:
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1.218 ihickson 192: </style><link href="http://www.w3.org/StyleSheets/TR/W3C-ED" rel="stylesheet" type="text/css"><div class="head">
1.115 ihickson 193: <p><a href="http://www.w3.org/"><img alt="W3C" height="48" src="http://www.w3.org/Icons/w3c_home" width="72"></a></p>
1.54 ihickson 194: <h1>Web Workers</h1>
1.196 ihickson 195:
1.228 ! ihickson 196: <h2 class="no-num no-toc" id="editor-s-draft-11-february-2010">Editor's Draft 11 February 2010</h2>
1.218 ihickson 197: <dl><dt>Latest Published Version:</dt>
1.115 ihickson 198: <dd><a href="http://www.w3.org/TR/workers/">http://www.w3.org/TR/workers/</a></dd>
1.109 ihickson 199: <dt>Latest Editor's Draft:</dt>
1.115 ihickson 200: <dd><a href="http://dev.w3.org/html5/workers/">http://dev.w3.org/html5/workers/</a></dd>
1.117 ihickson 201: <!-- ZZZ: add the new version after it has shipped-->
1.2 ihickson 202: <dt>Previous Versions:</dt>
1.113 ihickson 203: <dd><a href="http://www.w3.org/TR/2009/WD-workers-20090423/">http://www.w3.org/TR/2009/WD-workers-20090423/</a>
1.198 ihickson 204: <dd><a href="http://www.w3.org/TR/2009/WD-workers-20091029/">http://www.w3.org/TR/2009/WD-workers-20091029/</a></dd>
1.117 ihickson 205: <!-- :ZZZ -->
1.81 ihickson 206: <dt>Editors:</dt>
1.115 ihickson 207: <dd><a href="mailto:ian@hixie.ch">Ian Hickson</a>, Google, Inc.</dd>
1.155 ihickson 208: </dl><p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a>
209: © 2009 <a href="http://www.w3.org/"><abbr title="World Wide
210: Web Consortium">W3C</abbr></a><sup>®</sup> (<a href="http://www.csail.mit.edu/"><abbr title="Massachusetts
1.115 ihickson 211: Institute of Technology">MIT</abbr></a>, <a href="http://www.ercim.org/"><abbr title="European Research
212: Consortium for Informatics and Mathematics">ERCIM</abbr></a>, <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C
213: <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
214: <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
215: and <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document
1.81 ihickson 216: use</a> rules apply.</p>
1.201 ihickson 217:
1.155 ihickson 218: </div><hr class="top"><h2 class="no-num no-toc" id="abstract">Abstract</h2><p>This specification defines an API that allows Web application
1.81 ihickson 219: authors to spawn background workers running scripts in parallel to
220: their main page. This allows for thread-like operation with
1.212 ihickson 221: message-passing as the coordination mechanism.<h2 class="no-num no-toc" id="status-of-this-document">Status of This document</h2><!-- intro boilerplate (required) --><p><em>This section describes the status of this document at the
1.81 ihickson 222: time of its publication. Other documents may supersede this
223: document. A list of current W3C publications and the most recently
224: formally published revision of this technical report can be found in
1.115 ihickson 225: the <a href="http://www.w3.org/TR/">W3C technical reports index</a>
1.201 ihickson 226: at http://www.w3.org/TR/.</em></p><!-- where to send feedback (required) --><p>If you wish to make comments regarding this document, please send
1.115 ihickson 227: them to <a href="mailto:public-webapps@w3.org">public-webapps@w3.org</a>
1.90 ihickson 228: (<a href="mailto:public-webapps-request@w3.org?subject=subscribe">subscribe</a>,
1.115 ihickson 229: <a href="http://lists.w3.org/Archives/Public/public-webapps/">archives</a>)
1.81 ihickson 230:
231: <!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING SENTENCE TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
1.115 ihickson 232: or <a href="mailto:whatwg@whatwg.org">whatwg@whatwg.org</a> (<a href="http://lists.whatwg.org/listinfo.cgi/whatwg-whatwg.org">subscribe</a>,
233: <a href="http://lists.whatwg.org/pipermail/whatwg-whatwg.org/">archives</a>).
1.110 ihickson 234: <!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING SENTENCE TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
1.1 ihickson 235:
1.155 ihickson 236: All feedback is welcome.</p><!-- stability (required) --><p>Implementors should be aware that this specification is not
1.81 ihickson 237: stable. <strong>Implementors who are not taking part in the
238: discussions are likely to find the specification changing out from
239: under them in incompatible ways.</strong> Vendors interested in
240: implementing this specification before it eventually reaches the
241: Candidate Recommendation stage should join the aforementioned
1.155 ihickson 242: mailing lists and take part in the discussions.</p><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- version history or list of changes (required) --><p>The latest stable version of the editor's draft of this
1.115 ihickson 243: specification is always available on <a href="http://dev.w3.org/html5/workers/Overview.html">the W3C CVS
244: server</a> and in the <a href="http://svn.whatwg.org/webworkers/">WHATWG Subversion
1.81 ihickson 245: repository</a>. The latest editor's working copy (which may contain
1.115 ihickson 246: unfinished text in the process of being prepared) is available <a href="http://www.whatwg.org/specs/web-workers/current-work/">on the
1.81 ihickson 247: WHATWG site</a>. Detailed change history can be obtained from the
1.155 ihickson 248: following locations:</p><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING LIST TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><ul><li>Twitter messages (non-editorial changes only): <a href="http://twitter.com/WHATWG">http://twitter.com/WHATWG</a></li>
1.115 ihickson 249: <li>Interactive Web interface: <a href="http://html5.org/tools/web-workers-tracker">http://html5.org/tools/web-workers-tracker</a></li>
250: <li>Commit-Watchers mailing list: <a href="http://lists.whatwg.org/listinfo.cgi/commit-watchers-whatwg.org">http://lists.whatwg.org/listinfo.cgi/commit-watchers-whatwg.org</a></li>
251: <li>Subversion interface: <a href="http://svn.whatwg.org/webworkers/">http://svn.whatwg.org/webworkers/</a></li>
252: <li>CVS log: <a href="http://dev.w3.org/cvsweb/html5/workers/Overview.html">http://dev.w3.org/cvsweb/html5/workers/Overview.html</a></li>
1.155 ihickson 253: </ul><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING LIST TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- status of document, group responsible (required) --><p>The W3C <a href="http://www.w3.org/2008/webapps/">Web Apps
1.81 ihickson 254: Working Group</a> is the W3C working group responsible for this
255: specification's progress along the W3C Recommendation track.
1.196 ihickson 256:
1.228 ! ihickson 257: This specification is the 11 February 2010 Editor's Draft.
1.155 ihickson 258: </p><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- relationship to other work (required) --><p>This specification is also being produced by the <a href="http://www.whatwg.org/">WHATWG</a>. The two specifications are
259: identical from the table of contents onwards.</p><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- context and rationale (required) --><p>This specification is intended to specify a part of the Web
1.81 ihickson 260: platform closely related to HTML5. It is defined in a separate
1.155 ihickson 261: document primarily to ease the cognitive load on reviewers.</p><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- required patent boilerplate --><p>This document was produced by a group operating under the <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5
1.115 ihickson 262: February 2004 W3C Patent Policy</a>. W3C maintains a <a href="http://www.w3.org/2004/01/pp-impl/42538/status" rel="disclosure">public list of
1.81 ihickson 263: any patent disclosures</a> made in connection with the deliverables
264: of the group; that page also includes instructions for disclosing a
265: patent. An individual who has actual knowledge of a patent which the
1.115 ihickson 266: individual believes contains <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential
267: Claim(s)</a> must disclose the information in accordance with <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section
1.214 ihickson 268: 6 of the W3C Patent Policy</a>.</p><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- This text will be moved back to under the copyright in the header if this is not resolved by April 2010 --><p class="alt">The <a href="http://www.whatwg.org/specs/web-workers/current-work/">WHATWG
269: version</a> of this specification is available under a license that
270: permits reuse of the specification text.</p><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><h2 class="no-num no-toc" id="contents">Table of Contents</h2>
1.81 ihickson 271: <!--begin-toc-->
1.115 ihickson 272: <ol class="toc">
273: <li><a href="#introduction"><span class="secno">1 </span>Introduction</a>
1.81 ihickson 274: <ol>
1.115 ihickson 275: <li><a href="#scope"><span class="secno">1.1 </span>Scope</a></li>
276: <li><a href="#tutorial"><span class="secno">1.2 </span>Tutorial</a>
1.81 ihickson 277: <ol>
1.115 ihickson 278: <li><a href="#a-background-number-crunching-worker"><span class="secno">1.2.1 </span>A background number-crunching worker</a></li>
279: <li><a href="#a-worker-for-updating-a-client-side-database"><span class="secno">1.2.2 </span>A worker for updating a client-side database</a></li>
280: <li><a href="#worker-used-for-background-i-o"><span class="secno">1.2.3 </span>Worker used for background I/O</a></li>
281: <li><a href="#shared-workers"><span class="secno">1.2.4 </span>Shared workers</a></li>
282: <li><a href="#delegation"><span class="secno">1.2.5 </span>Delegation</a></li>
283: <li><a href="#providing-libraries"><span class="secno">1.2.6 </span>Providing libraries</a></ol></ol></li>
1.148 ihickson 284: <li><a href="#conformance-requirements"><span class="secno">2 </span>Conformance requirements</a>
1.82 ihickson 285: <ol>
1.148 ihickson 286: <li><a href="#dependencies"><span class="secno">2.1 </span>Dependencies</a></ol></li>
287: <li><a href="#terminology"><span class="secno">3 </span>Terminology</a></li>
288: <li><a href="#infrastructure"><span class="secno">4 </span>Infrastructure</a>
289: <ol>
290: <li><a href="#the-global-scope"><span class="secno">4.1 </span>The global scope</a>
1.81 ihickson 291: <ol>
1.148 ihickson 292: <li><a href="#the-workerglobalscope-abstract-interface"><span class="secno">4.1.1 </span>The <code>WorkerGlobalScope</code> abstract interface</a></li>
293: <li><a href="#dedicated-workers-and-the-dedicatedworkerglobalscope-interface"><span class="secno">4.1.2 </span>Dedicated workers and the <code>DedicatedWorkerGlobalScope</code> interface</a></li>
294: <li><a href="#shared-workers-and-the-sharedworkerglobalscope-inteface"><span class="secno">4.1.3 </span>Shared workers and the <code>SharedWorkerGlobalScope</code> inteface</a></ol></li>
1.160 ihickson 295: <li><a href="#origins-of-workers"><span class="secno">4.2 </span>Origins of workers</a></li>
1.186 ihickson 296: <li><a href="#the-event-loop"><span class="secno">4.3 </span>The event loop</a></li>
297: <li><a href="#the-worker-s-lifetime"><span class="secno">4.4 </span>The worker's lifetime</a></li>
298: <li><a href="#processing-model"><span class="secno">4.5 </span>Processing model</a></li>
299: <li><a href="#runtime-script-errors"><span class="secno">4.6 </span>Runtime script errors</a></li>
300: <li><a href="#creating-workers"><span class="secno">4.7 </span>Creating workers</a>
1.81 ihickson 301: <ol>
1.186 ihickson 302: <li><a href="#the-abstractworker-abstract-interface"><span class="secno">4.7.1 </span>The <code>AbstractWorker</code> abstract interface</a></li>
303: <li><a href="#dedicated-workers-and-the-worker-interface"><span class="secno">4.7.2 </span>Dedicated workers and the <code>Worker</code> interface</a></li>
304: <li><a href="#shared-workers-and-the-sharedworker-interface"><span class="secno">4.7.3 </span>Shared workers and the <code>SharedWorker</code> interface</a></ol></ol></li>
1.148 ihickson 305: <li><a href="#apis-available-to-workers"><span class="secno">5 </span>APIs available to workers</a>
1.81 ihickson 306: <ol>
1.148 ihickson 307: <li><a href="#importing-scripts-and-libraries"><span class="secno">5.1 </span>Importing scripts and libraries</a></li>
1.210 ihickson 308: <li><a href="#the-workernavigator-object"><span class="secno">5.2 </span>The <code>WorkerNavigator</code> object</a></li>
1.148 ihickson 309: <li><a href="#apis-defined-in-other-specifications"><span class="secno">5.3 </span>APIs defined in other specifications</a></li>
310: <li><a href="#interface-objects-and-constructors"><span class="secno">5.4 </span>Interface objects and constructors</a></li>
311: <li><a href="#worker-locations"><span class="secno">5.5 </span>Worker locations</a></ol></li>
1.115 ihickson 312: <li><a class="no-num" href="#references">References</a></li>
313: <li><a class="no-num" href="#acknowledgements">Acknowledgements</a></ol>
1.155 ihickson 314: <!--end-toc--><hr><h2 id="introduction"><span class="secno">1 </span>Introduction</h2><h3 id="scope"><span class="secno">1.1 </span>Scope</h3><p><i>This section is non-normative.</i><p>This specification defines an API for running scripts in the
315: background independently of any user interface scripts.<p>This allows for long-running scripts that are not interrupted by
1.81 ihickson 316: scripts that respond to clicks or other user interactions, and
317: allows long tasks to be executed without yielding to keep the page
1.155 ihickson 318: responsive.<p>Workers (as these background scripts are called herein) are
1.81 ihickson 319: relatively heavy-weight, and are not intended to be used in large
320: numbers. For example, it would be inappropriate to launch one worker
321: for each pixel of a four megapixel image. The examples below show
1.155 ihickson 322: some appropriate uses of workers.<p>Generally, workers are expected to be long-lived, have a high
323: start-up performance cost, and a high per-instance memory cost.<h3 id="tutorial"><span class="secno">1.2 </span>Tutorial</h3><p><i>This section is non-normative.</i><p>There are a variety of uses that workers can be put to. The
324: following subsections show various examples of this use.<h4 id="a-background-number-crunching-worker"><span class="secno">1.2.1 </span>A background number-crunching worker</h4><p><i>This section is non-normative.</i><p>The simplest use of workers is for performing a computationally
325: expensive task without interrupting the user interface.<p>In this example, the main document spawns a worker to
326: (naïvely) compute prime numbers, and progressively displays the
327: most recently found prime number.<p>The main page is as follows:<pre><!DOCTYPE HTML>
1.81 ihickson 328: <html>
329: <head>
330: <title>Worker example: One-core computation</title>
331: </head>
332: <body>
333: <p>The highest prime number discovered so far is: <output id="result"></output></p>
334: <script>
1.50 ihickson 335: var worker = new Worker('worker.js');
336: worker.onmessage = function (event) {
1.54 ihickson 337: document.getElementById('result').textContent = event.data;
1.29 ihickson 338: };
1.81 ihickson 339: </script>
340: </body>
1.155 ihickson 341: </html></pre><p>The <code title="dom-Worker"><a href="#dom-worker">Worker()</a></code> constructor call
1.115 ihickson 342: creates a worker and returns a <code><a href="#worker">Worker</a></code> object
1.81 ihickson 343: representing that worker, which is used to communicate with the
1.177 ihickson 344: worker. That object's <code title="handler-Worker-onmessage"><a href="#handler-worker-onmessage">onmessage</a></code> event handler allows the code to receive messages from the worker.<p>The worker itself is as follows:<pre>var n = 1;
1.29 ihickson 345: search: while (true) {
346: n += 1;
347: for (var i = 2; i <= Math.sqrt(n); i += 1)
348: if (n % i == 0)
349: continue search;
350: // found a prime!
1.50 ihickson 351: postMessage(n);
1.155 ihickson 352: }</pre><p>The bulk of this code is simply an unoptimized search for a prime
1.115 ihickson 353: number. To send a message back to the page, the <code title="dom-DedicatedWorkerGlobalScope-postMessage"><a href="#dom-dedicatedworkerglobalscope-postmessage">postMessage()</a></code>
1.155 ihickson 354: method is used to post a message when a prime is found.<p><a href="http://www.whatwg.org/demos/workers/primes/page.html">View this example online</a>.<h4 id="a-worker-for-updating-a-client-side-database"><span class="secno">1.2.2 </span>A worker for updating a client-side database</h4><p><i>This section is non-normative.</i><p>In this example, the main document spawns a worker whose only
1.81 ihickson 355: task is to listen for notifications from the server, and, when
356: appropriate, either add or remove data from the client-side
1.155 ihickson 357: database.<p>Since no communication occurs between the worker and the main
358: page, the main page can start the worker by just doing:<pre><script>
1.50 ihickson 359: new Worker('worker.js');
1.155 ihickson 360: </script></pre><p>The worker itself is as follows:<pre>var server = new WebSocket('ws://whatwg.org/database');
1.42 ihickson 361: var database = openDatabase('demobase', '1.0', 'Demo Database', 10240);
1.31 ihickson 362: server.onmessage = function (event) {
363: // data is in the format "command key value"
1.54 ihickson 364: var data = event.data.split(' ');
1.31 ihickson 365: switch (data[0]) {
366: case '+':
367: database.transaction(function(tx) {
368: tx.executeSql('INSERT INTO pairs (key, value) VALUES (?, ?)', data[1], data[2]);
369: });
370: case '-':
371: database.transaction(function(tx) {
372: tx.executeSql('DELETE FROM pairs WHERE key=? AND value=?', data[1], data[2]);
373: });
374: }
1.155 ihickson 375: };</pre><p>This connects to the server using the <code>WebSocket</code>
1.81 ihickson 376: mechanism and opens the local database (which, we presume, has been
377: created earlier). The worker then just listens for messages from the
378: server and acts on them as appropriate, forever (or until the main
1.155 ihickson 379: page is closed).<p><a href="http://www.whatwg.org/demos/workers/database-updater/page.html">View
1.81 ihickson 380: this example online</a>. (This example will not actually function,
381: since the server does not actually exist and the database is not
1.155 ihickson 382: created by this sample code.)<h4 id="worker-used-for-background-i-o"><span class="secno">1.2.3 </span>Worker used for background I/O</h4><p><i>This section is non-normative.</i><p>In this example, the main document uses two workers, one for
1.81 ihickson 383: fetching stock updates for at regular intervals, and one for
1.155 ihickson 384: fetching performing search queries that the user requests.<p>The main page is as follows:<pre><!DOCTYPE HTML>
1.81 ihickson 385: <html>
386: <head>
387: <title>Worker example: Stock ticker</title>
388: <script>
1.33 ihickson 389: // TICKER
390: var symbol = 'GOOG'; // default symbol to watch
1.50 ihickson 391: var ticker = new Worker('ticker.js');
1.33 ihickson 392:
393: // SEARCHER
1.50 ihickson 394: var searcher = new Worker('searcher.js');
1.33 ihickson 395: function search(query) {
1.50 ihickson 396: searcher.postMessage(query);
1.33 ihickson 397: }
398:
399: // SYMBOL SELECTION UI
400: function select(newSymbol) {
401: symbol = newSymbol;
1.50 ihickson 402: ticker.postMessage(symbol);
1.33 ihickson 403: }
1.81 ihickson 404: </script>
405: </head>
1.122 ihickson 406: <body onload="search('')">
1.81 ihickson 407: <p><output id="symbol"></output> <output id="value"></output></p>
408: <script>
1.50 ihickson 409: ticker.onmessage = function (event) {
1.54 ihickson 410: var data = event.data.split(' ');
1.33 ihickson 411: document.getElementById('symbol').textContent = data[0];
412: document.getElementById('value').textContent = data[1];
413: };
1.50 ihickson 414: ticker.postMessage(symbol);
1.81 ihickson 415: </script>
1.122 ihickson 416: <p><label>Search: <input type="text" autofocus oninput="search(this.value)"></label></p>
1.81 ihickson 417: <ul id="results"></ul>
418: <script>
1.50 ihickson 419: searcher.onmessage = function (event) {
1.54 ihickson 420: var data = event.data.split(' ');
1.33 ihickson 421: var results = document.getElementById('results');
422: while (results.hasChildNodes()) // clear previous results
423: results.removeChild(results.firstChild);
424: for (var i = 0; i < data.length; i += 1) {
425: // add a list item with a button for each result
426: var li = document.createElement('li');
427: var button = document.createElement('button');
428: button.value = data[i];
429: button.type = 'button';
430: button.onclick = function () { select(this.value); };
431: button.textContent = data[i];
432: li.appendChild(button);
433: results.appendChild(li);
434: }
435: };
1.81 ihickson 436: </script>
437: <p>(The data in this example is not real. Try searching for "Google" or "Apple".)</p>
438: </body>
1.155 ihickson 439: </html></pre><p>The two workers use a common library for performing the actual
440: network calls. This library is as follows:<pre>function get(url) {
1.50 ihickson 441: try {
442: var xhr = new XMLHttpRequest();
443: xhr.open('GET', url, false);
444: xhr.send();
445: return xhr.responseText;
446: } catch (e) {
447: return ''; // turn all errors into empty results
448: }
1.155 ihickson 449: }</pre><p>The stock updater worker is as follows:<pre>importScripts('io.js');
1.33 ihickson 450: var timer;
451: var symbol;
452: function update() {
1.50 ihickson 453: postMessage(symbol + ' ' + get('stock.cgi?' + symbol));
1.33 ihickson 454: timer = setTimeout(update, 10000);
455: }
1.50 ihickson 456: onmessage = function (event) {
1.33 ihickson 457: if (timer)
458: clearTimeout(timer);
1.54 ihickson 459: symbol = event.data;
1.33 ihickson 460: update();
1.155 ihickson 461: };</pre><p>The search query worker is as follows:<pre>importScripts('io.js');
1.50 ihickson 462: onmessage = function (event) {
1.54 ihickson 463: postMessage(get('search.cgi?' + event.data));
1.155 ihickson 464: };</pre><p><a href="http://www.whatwg.org/demos/workers/stocks/page.html">View this example online</a>.<h4 id="shared-workers"><span class="secno">1.2.4 </span>Shared workers</h4><p><i>This section is non-normative.</i><p>In this example, multiple windows (viewers) can be opened that
1.81 ihickson 465: are all viewing the same map. All the windows share the same map
466: information, with a single worker coordinating all the viewers. Each
467: viewer can move around independently, but if they set any data on
1.155 ihickson 468: the map, all the viewers are updated.<p>The main page isn't interesting, it merely provides a way to open
469: the viewers:<pre><!DOCTYPE HTML>
1.81 ihickson 470: <html>
471: <head>
472: <title>Workers example: Multiviewer</title>
473: <script>
1.36 ihickson 474: function openViewer() {
475: window.open('viewer.html');
476: }
1.81 ihickson 477: </script>
478: </head>
479: <body>
480: <p><button type=button onclick="openViewer()">Open a new
481: viewer</button></p>
482: <p>Each viewer opens in a new window. You can have as many viewers
483: as you like, they all view the same data.</p>
484: </body>
1.155 ihickson 485: </html></pre><p>The viewer is more involved:<pre><!DOCTYPE HTML>
1.81 ihickson 486: <html>
487: <head>
488: <title>Workers example: Multiviewer viewer</title>
489: <script>
1.50 ihickson 490: var worker = new SharedWorker('worker.js', 'core');
1.36 ihickson 491:
492: // CONFIGURATION
493: function configure(event) {
1.54 ihickson 494: if (event.data.substr(0, 4) != 'cfg ') return;
495: var name = event.data.substr(4).split(' ', 1);
1.36 ihickson 496: // update display to mention our name is name
497: document.getElementsByTagName('h1')[0].textContent += ' ' + name;
498: // no longer need this listener
1.43 ihickson 499: worker.port.removeEventListener('message', configure, false);
1.36 ihickson 500: }
1.53 ihickson 501: worker.port.addEventListener('message', configure, false);
1.36 ihickson 502:
503: // MAP
504: function paintMap(event) {
1.54 ihickson 505: if (event.data.substr(0, 4) != 'map ') return;
506: var data = event.data.substr(4).split(',');
1.36 ihickson 507: // display tiles data[0] .. data[8]
508: var canvas = document.getElementById('map');
509: var context = canvas.getContext('2d');
510: for (var y = 0; y < 3; y += 1) {
511: for (var x = 0; x < 3; x += 1) {
512: var tile = data[y * 3 + x];
513: if (tile == '0')
514: context.fillStyle = 'green';
515: else
516: context.fillStyle = 'maroon';
517: fillRect(x * 50, y * 50, 50, 50);
518: }
519: }
520: }
1.53 ihickson 521: worker.port.addEventListener('message', paintMap, false);
1.36 ihickson 522:
523: // PUBLIC CHAT
524: function updatePublicChat(event) {
1.54 ihickson 525: if (event.data.substr(0, 4) != 'txt ') return;
526: var name = event.data.substr(4).split(' ', 1);
527: var message = event.data.substr(4 + length(name) + 1);
1.81 ihickson 528: // display "<name> message" in public chat
1.36 ihickson 529: var dialog = document.getElementById('public');
530: var dt = document.createElement('dt');
531: dt.textContent = name;
532: dialog.appendChild(dt);
533: var dd = document.createElement('dd');
534: dd.textContent = message;
535: dialog.appendChild(dd);
536: }
1.53 ihickson 537: worker.port.addEventListener('message', updatePublicChat, false);
1.36 ihickson 538:
539: // PRIVATE CHAT
540: function startPrivateChat(event) {
1.54 ihickson 541: if (event.data.substr(0, 4) != 'msg ') return;
542: var name = event.data.substr(4).split(' ', 1);
1.84 ihickson 543: var port = event.ports[0];
1.36 ihickson 544: // display a private chat UI
545: var ul = document.getElementById('private');
546: var li = document.createElement('li');
547: var h3 = document.createElement('h3');
548: h3.textContent = 'Private chat with ' + name;
549: li.appendChild(h3);
550: var dialog = document.createElement('dialog');
551: var addMessage = function(name, message) {
552: var dt = document.createElement('dt');
553: dt.textContent = name;
554: dialog.appendChild(dt);
555: var dd = document.createElement('dd');
556: dd.textContent = message;
557: dialog.appendChild(dd);
558: };
559: port.onmessage = function (event) {
1.54 ihickson 560: addMessage(name, event.data);
1.36 ihickson 561: };
562: li.appendChild(dialog);
563: var form = document.createElement('form');
564: var p = document.createElement('p');
565: var input = document.createElement('input');
566: input.size = 50;
567: p.appendChild(input);
568: p.appendChild(document.createTextNode(' '));
569: var button = document.createElement('button');
570: button.textContent = 'Post';
571: p.appendChild(button);
572: form.onsubmit = function () {
573: port.postMessage(input.value);
574: addMessage('me', input.value);
575: input.value = '';
576: return false;
577: };
578: form.appendChild(p);
579: li.appendChild(form);
580: }
1.53 ihickson 581: worker.port.addEventListener('message', startPrivateChat, false);
1.188 ihickson 582:
583: worker.port.start();
1.81 ihickson 584: </script>
585: </head>
586: <body>
587: <h1>Viewer</h1>
588: <h2>Map</h2>
589: <p><canvas id="map" height=150 width=150></canvas></p>
590: <p>
591: <button type=button onclick="worker.port.postMessage('mov left')">Left</button>
592: <button type=button onclick="worker.port.postMessage('mov up')">Up</button>
593: <button type=button onclick="worker.port.postMessage('mov down')">Down</button>
594: <button type=button onclick="worker.port.postMessage('mov right')">Right</button>
595: <button type=button onclick="worker.port.postMessage('set 0')">Set 0</button>
596: <button type=button onclick="worker.port.postMessage('set 1')">Set 1</button>
597: </p>
598: <h2>Public Chat</h2>
599: <dialog id="public"></dialog>
600: <form onsubmit="worker.port.postMessage('txt ' + message.value); message.value = ''; return false;">
601: <p>
602: <input type="text" name="message" size="50">
603: <button>Post</button>
604: </p>
605: </form>
606: <h2>Private Chat</h2>
607: <ul id="private"></ul>
608: </body>
609: </html>
1.155 ihickson 610: </pre><p>There are several key things worth noting about the way the
611: viewer is written.<p><strong>Multiple listeners</strong>. Instead of a single message
1.81 ihickson 612: processing function, the code here attaches multiple event
613: listeners, each one performing a quick check to see if it is
614: relevant for the message. In this example it doesn't make much
615: difference, but if multiple authors wanted to collaborate using a
616: single port to communicate with a worker, it would allow for
617: independent code instead of changes having to all be made to a
1.155 ihickson 618: single event handling function.<p>Registering event listeners in this way also allows you to
1.81 ihickson 619: unregister specific listeners when you are done with them, as is
620: done with the <code title="">configure()</code> method in this
1.155 ihickson 621: example.<p>Finally, the worker:<pre>
622: var nextName = 0;
1.36 ihickson 623: function getNextName() {
624: // this could use more friendly names
625: // but for now just return a number
626: return nextName++;
627: }
628:
629: var map = [
630: [0, 0, 0, 0, 0, 0, 0],
631: [1, 1, 0, 1, 0, 1, 1],
632: [0, 1, 0, 1, 0, 0, 0],
633: [0, 1, 0, 1, 0, 1, 1],
634: [0, 0, 0, 1, 0, 0, 0],
635: [1, 0, 0, 1, 1, 1, 1],
636: [1, 1, 0, 1, 1, 0, 1],
637: ];
638:
639: function wrapX(x) {
640: if (x < 0) return wrapX(x + map[0].length);
1.81 ihickson 641: if (x >= map[0].length) return wrapX(x - map[0].length);
1.36 ihickson 642: return x;
643: }
644:
645: function wrapY(y) {
646: if (y < 0) return wrapY(y + map.length);
1.81 ihickson 647: if (y >= map[0].length) return wrapY(y - map.length);
1.36 ihickson 648: return y;
649: }
650:
1.50 ihickson 651: function sendMapData(callback) {
1.36 ihickson 652: var data = '';
653: for (var y = viewer.y-1; y <= viewer.y+1; y += 1) {
654: for (var x = viewer.x-1; x <= viewer.x+1; x += 1) {
655: if (data != '')
656: data += ',';
657: data += map[y][x];
658: }
659: }
1.50 ihickson 660: callback('map ' + data);
1.36 ihickson 661: }
662:
663: var viewers = {};
664: onconnect = function (event) {
1.84 ihickson 665: event.ports[0]._name = getNextName();
666: event.ports[0]._data = { port: event.port, x: 0, y: 0, };
667: viewers[event.ports[0]._name] = event.port._data;
668: event.ports[0].postMessage('cfg ' + name);
669: event.ports[0].onmessage = getMessage;
670: sendMapData(event.ports[0].postMessage);
1.36 ihickson 671: };
672:
673: function getMessage(event) {
1.54 ihickson 674: switch (event.data.substr(0, 4)) {
1.36 ihickson 675: case 'mov ':
1.54 ihickson 676: var direction = event.data.substr(4);
1.36 ihickson 677: var dx = 0;
678: var dy = 0;
679: switch (direction) {
680: case 'up': dy = -1; break;
681: case 'down': dy = 1; break;
682: case 'left': dx = -1; break;
683: case 'right': dx = 1; break;
684: }
685: event.target._data.x = wrapX(event.target._data.x + dx);
686: event.target._data.y = wrapY(event.target._data.y + dy);
1.50 ihickson 687: sendMapData(event.target.postMessage);
1.36 ihickson 688: break;
689: case 'set ':
1.54 ihickson 690: var value = event.data.substr(4);
1.36 ihickson 691: map[event.target._data.y][event.target._data.x] = value;
692: for (var viewer in viewers)
1.50 ihickson 693: sendMapData(viewers[viewer].port.postMessage);
1.36 ihickson 694: break;
695: case 'txt ':
696: var name = event.target._name;
1.54 ihickson 697: var message = event.data.substr(4);
1.36 ihickson 698: for (var viewer in viewers)
699: viewers[viewer].port.postMessage('txt ' + name + ' ' + message);
700: break;
701: case 'msg ':
702: var party1 = event._data;
1.54 ihickson 703: var party2 = viewers[event.data.substr(4).split(' ', 1)];
1.36 ihickson 704: if (party2) {
705: var channel = new MessageChannel();
1.84 ihickson 706: party1.port.postMessage('msg ' + party2.name, [channel.port1]);
707: party2.port.postMessage('msg ' + party1.name, [channel.port2]);
1.36 ihickson 708: }
709: break;
710: }
1.155 ihickson 711: }</pre><p><strong>Connecting to multiple pages</strong>. The script uses
1.115 ihickson 712: the <code title="handler-SharedWorkerGlobalScope-onconnect"><a href="#handler-sharedworkerglobalscope-onconnect">onconnect</a></code>
1.155 ihickson 713: event listener to listen for multiple connections.<p><strong>Direct channels</strong>. When the worker receives a
1.81 ihickson 714: "msg" message from one viewer naming another viewer, it sets up a
715: direct connection between the two, so that the two viewers can
716: communicate directly without the worker having to proxy all the
1.155 ihickson 717: messages.<p><a href="http://www.whatwg.org/demos/workers/multiviewer/page.html">View this example online</a>.<h4 id="delegation"><span class="secno">1.2.5 </span>Delegation</h4><p><i>This section is non-normative.</i><p>With multicore CPUs becoming prevalent, one way to obtain better
1.81 ihickson 718: performance is to split computationally expensive tasks amongst
719: multiple workers. In this example, a computationally expensive task
720: that is to be performed for every number from 1 to 10,000,000 is
1.155 ihickson 721: farmed out to ten subworkers.<p>The main page is as follows, it just reports the result:<pre><!DOCTYPE HTML>
1.81 ihickson 722: <html>
723: <head>
1.203 ihickson 724: <title>Worker example: Multicore computation</title>
1.81 ihickson 725: </head>
726: <body>
1.203 ihickson 727: <p>Result: <output id="result"></output></p>
1.81 ihickson 728: <script>
1.50 ihickson 729: var worker = new Worker('worker.js');
730: worker.onmessage = function (event) {
1.54 ihickson 731: document.getElementById('result').textContent = event.data;
1.40 ihickson 732: };
1.81 ihickson 733: </script>
734: </body>
1.155 ihickson 735: </html></pre><p>The worker itself is as follows:<pre>// settings
1.40 ihickson 736: var num_workers = 10;
737: var items_per_worker = 1000000;
738:
739: // start the workers
740: var result = 0;
741: var pending_workers = num_workers;
742: for (var i = 0; i < num_workers; i += 1) {
1.50 ihickson 743: var worker = new Worker('core.js');
744: worker.postMessage(i * items_per_worker);
745: worker.postMessage((i+1) * items_per_worker);
746: worker.onmessage = storeResult;
1.40 ihickson 747: }
748:
749: // handle the results
750: function storeResult(event) {
1.54 ihickson 751: result += 1*event.data;
1.40 ihickson 752: pending_workers -= 1;
753: if (pending_workers <= 0)
1.50 ihickson 754: postMessage(result); // finished!
1.155 ihickson 755: }</pre><p>It consists of a loop to start the subworkers, and then a handler
756: that waits for all the subworkers to respond.<p>The subworkers are implemented as follows:<pre>var start;
1.41 ihickson 757: onmessage = getStart;
1.40 ihickson 758: function getStart(event) {
1.54 ihickson 759: start = 1*event.data;
1.40 ihickson 760: onmessage = getEnd;
761: }
762:
763: var end;
764: function getEnd(event) {
1.54 ihickson 765: end = 1*event.data;
1.40 ihickson 766: onmessage = null;
1.66 ihickson 767: work();
1.40 ihickson 768: }
769:
1.66 ihickson 770: function work() {
1.40 ihickson 771: var result = 0;
772: for (var i = start; i < end; i += 1) {
773: // perform some complex calculation here
774: result += 1;
775: }
1.50 ihickson 776: postMessage(result);
777: close();
1.155 ihickson 778: }</pre><p>They receive two numbers in two events, perform the computation
1.81 ihickson 779: for the range of numbers thus specified, and then report the result
1.155 ihickson 780: back to the parent.<p><a href="http://www.whatwg.org/demos/workers/multicore/page.html">View this example online</a>.<h4 id="providing-libraries"><span class="secno">1.2.6 </span>Providing libraries</h4><p><i>This section is non-normative.</i><p>Suppose that a cryptography library is made available that
781: provides three tasks:<dl><dt>Generate a public/private key pair</dt>
1.81 ihickson 782:
783: <dd>Takes a port, on which it will send two messages, first the
784: public key and then the private key.</dd>
785:
786: <dt>Given a plaintext and a public key, return the corresponding cyphertext</dt>
787:
788: <dd>Takes a port, to which any number of messages can be sent, the
789: first giving the public key, and the remainder giving the
790: plaintext, each of which is encrypted and then sent on that same
791: channel as the cyphertext. The user can close the port when it is
792: done encrypting content.</dd>
793:
794: <dt>Given a cyphertext and a private key, return the corresponding plaintext</dt>
795:
796: <dd>Takes a port, to which any number of messages can be sent, the
797: first giving the private key, and the remainder giving the
798: cyphertext, each of which is decrypted and then sent on that same
799: channel as the plaintext. The user can close the port when it is
800: done decrypting content.</dd>
1.49 ihickson 801:
1.155 ihickson 802: </dl><p>The library itself is as follows:<pre>function handleMessage(e) {
1.54 ihickson 803: if (e.data == "genkeys")
1.84 ihickson 804: genkeys(e.ports[0]);
1.54 ihickson 805: else if (e.data == "encrypt")
1.84 ihickson 806: encrypt(e.ports[0]);
1.54 ihickson 807: else if (e.data == "decrypt")
1.84 ihickson 808: decrypt(e.ports[0]);
1.49 ihickson 809: }
810:
811: function genkeys(p) {
812: var keys = _generateKeyPair();
813: p.postMessage(keys[0]);
814: p.postMessage(keys[1]);
815: }
816:
817: function encrypt(p) {
818: var key, state = 0;
819: p.onmessage = function (e) {
820: if (state == 0) {
1.54 ihickson 821: key = e.data;
1.49 ihickson 822: state = 1;
823: } else {
1.54 ihickson 824: p.postMessage(_encrypt(key, e.data));
1.49 ihickson 825: }
826: };
827: }
828:
829: function decrypt(p) {
830: var key, state = 0;
831: p.onmessage = function (e) {
832: if (state == 0) {
1.54 ihickson 833: key = e.data;
1.49 ihickson 834: state = 1;
835: } else {
1.54 ihickson 836: p.postMessage(_decrypt(key, e.data));
1.49 ihickson 837: }
838: };
839: }
840:
1.50 ihickson 841: // support being used as a shared worker as well as a dedicated worker
1.195 ihickson 842: if ('onmessage' in this) // dedicated worker
1.50 ihickson 843: onmessage = handleMessage;
844: else // shared worker
845: onconnect = function (e) { e.port.onmessage = handleMessage; }
1.49 ihickson 846:
847:
848: // the "crypto" functions:
849:
850: function _generateKeyPair() {
851: return [Math.random(), Math.random()];
852: }
853:
854: function _encrypt(k, s) {
855: return 'encrypted-' + k + ' ' + s;
856: }
857:
858: function _decrypt(k, s) {
859: return s.substr(s.indexOf(' ')+1);
1.155 ihickson 860: }</pre><p>Note that the crypto functions here are just stubs and don't do
861: real cryptography.<p>This library could be used as follows:<pre><!DOCTYPE HTML>
1.81 ihickson 862: <html>
863: <head>
864: <title>Worker example: Crypto library</title>
865: <script>
1.50 ihickson 866: var crytoLib = new Worker('libcrypto-v1.js'); // or could use 'libcrypto-v2.js'
1.49 ihickson 867: function getKeys() {
868: var state = 0;
1.50 ihickson 869: cryptoLib.startConversation("genkeys").onmessage = function (e) {
1.49 ihickson 870: if (state == 0)
1.54 ihickson 871: document.getElementById('public').value = e.data;
1.49 ihickson 872: else if (state == 1)
1.54 ihickson 873: document.getElementById('private').value = e.data;
1.49 ihickson 874: state += 1;
875: };
876: }
877: function enc() {
1.50 ihickson 878: var port = cryptoLib.startConversation("encrypt");
879: port.postMessage(document.getElementById('public').value);
880: port.postMessage(document.getElementById('input').value);
881: port.onmessage = function (e) {
1.54 ihickson 882: document.getElementById('input').value = e.data;
1.50 ihickson 883: port.close();
1.49 ihickson 884: };
885: }
886: function dec() {
1.50 ihickson 887: var port = cryptoLib.startConversation("decrypt");
888: port.postMessage(document.getElementById('private').value);
889: port.postMessage(document.getElementById('input').value);
890: port.onmessage = function (e) {
1.54 ihickson 891: document.getElementById('input').value = e.data;
1.50 ihickson 892: port.close();
1.49 ihickson 893: };
894: }
1.81 ihickson 895: </script>
896: <style>
1.49 ihickson 897: textarea { display: block; }
1.81 ihickson 898: </style>
899: </head>
900: <body onload="getKeys()">
901: <fieldset>
902: <legend>Keys</legend>
903: <p><label>Public Key: <textarea id="public"></textarea></label></p>
904: <p><label>Private Key: <textarea id="private"></textarea></label></p>
905: </fieldset>
906: <p><label>Input: <textarea id="input"></textarea></label></p>
907: <p><button onclick="enc()">Encrypt</button> <button onclick="dec()">Decrypt</button></p>
908: </body>
1.155 ihickson 909: </html></pre><p>A later version of the API, though, might want to offload all the
910: crypto work onto subworkers. This could be done as follows:<pre>function handleMessage(e) {
1.54 ihickson 911: if (e.data == "genkeys")
1.84 ihickson 912: genkeys(e.ports[0]);
1.54 ihickson 913: else if (e.data == "encrypt")
1.84 ihickson 914: encrypt(e.ports[0]);
1.54 ihickson 915: else if (e.data == "decrypt")
1.84 ihickson 916: decrypt(e.ports[0]);
1.49 ihickson 917: }
918:
919: function genkeys(p) {
1.50 ihickson 920: var generator = new Worker('libcrypto-v2-generator.js');
1.84 ihickson 921: generator.postMessage('', [p]);
1.49 ihickson 922: }
923:
924: function encrypt(p) {
925: p.onmessage = function (e) {
1.54 ihickson 926: var key = e.data;
1.50 ihickson 927: var encryptor = new Worker('libcrypto-v2-encryptor.js');
1.84 ihickson 928: encryptor.postMessage(key, [p]);
1.49 ihickson 929: };
930: }
931:
932: function encrypt(p) {
933: p.onmessage = function (e) {
1.54 ihickson 934: var key = e.data;
1.50 ihickson 935: var decryptor = new Worker('libcrypto-v2-decryptor.js');
1.84 ihickson 936: decryptor.postMessage(key, [p]);
1.49 ihickson 937: };
938: }
939:
1.50 ihickson 940: // support being used as a shared worker as well as a dedicated worker
1.195 ihickson 941: if ('onmessage' in this) // dedicated worker
1.50 ihickson 942: onmessage = handleMessage;
943: else // shared worker
1.84 ihickson 944: onconnect = function (e) { e.ports[0].onmessage = handleMessage };
1.155 ihickson 945: </pre><p>The little subworkers would then be as follows.<p>For generating key pairs:<pre>onmessage = function (e) {
1.50 ihickson 946: var k = _generateKeyPair();
1.84 ihickson 947: e.ports[0].postMessage(k[0]);
948: e.ports[0].postMessage(k[1]);
1.49 ihickson 949: close();
950: }
1.50 ihickson 951:
952: function _generateKeyPair() {
953: return [Math.random(), Math.random()];
1.155 ihickson 954: }</pre><p>For encrypting:<pre>onmessage = function (e) {
1.54 ihickson 955: var key = e.data;
1.84 ihickson 956: e.ports[0].onmessage = function (e) {
1.54 ihickson 957: var s = e.data;
1.50 ihickson 958: postMessage(_encrypt(key, s));
1.49 ihickson 959: }
1.50 ihickson 960: }
961:
962: function _encrypt(k, s) {
963: return 'encrypted-' + k + ' ' + s;
1.155 ihickson 964: }</pre><p>For decrypting:<pre>onmessage = function (e) {
1.54 ihickson 965: var key = e.data;
1.84 ihickson 966: e.ports[0].onmessage = function (e) {
1.54 ihickson 967: var s = e.data;
1.50 ihickson 968: postMessage(_decrypt(key, s));
1.49 ihickson 969: }
1.50 ihickson 970: }
971:
972: function _decrypt(k, s) {
973: return s.substr(s.indexOf(' ')+1);
1.155 ihickson 974: }</pre><p>Notice how the users of the API don't have to even know that this
975: is happening — the API hasn't changed; the library can
1.81 ihickson 976: delegate to subworkers without changing its API, even though it is
1.155 ihickson 977: accepting data using message channels.<p><a href="http://www.whatwg.org/demos/workers/crypto/page.html">View this example online</a>.<h2 id="conformance-requirements"><span class="secno">2 </span>Conformance requirements</h2><p>All diagrams, examples, and notes in this specification are
1.81 ihickson 978: non-normative, as are all sections explicitly marked non-normative.
1.155 ihickson 979: Everything else in this specification is normative.<p>The key words "MUST", "MUST NOT", "REQUIRED", <!--"SHALL", "SHALL
1.81 ihickson 980: NOT",--> "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
981: "OPTIONAL" in the normative parts of this document are to be
982: interpreted as described in RFC2119. For readability, these words do
1.155 ihickson 983: not appear in all uppercase letters in this specification. <a href="#refsRFC2119">[RFC2119]</a><p>Requirements phrased in the imperative as part of algorithms
1.81 ihickson 984: (such as "strip any leading space characters" or "return false and
985: abort these steps") are to be interpreted with the meaning of the
986: key word ("must", "should", "may", etc) used in introducing the
1.155 ihickson 987: algorithm.<p>Some conformance requirements are phrased as requirements on
1.81 ihickson 988: attributes, methods or objects. Such requirements are to be
1.155 ihickson 989: interpreted as requirements on user agents.<p>Conformance requirements phrased as algorithms or specific steps
1.81 ihickson 990: may be implemented in any manner, so long as the end result is
991: equivalent. (In particular, the algorithms defined in this
992: specification are intended to be easy to follow, and not intended to
1.155 ihickson 993: be performant.)<p>The only conformance class defined by this specification is user
994: agents.<p>User agents may impose implementation-specific limits on
1.81 ihickson 995: otherwise unconstrained inputs, e.g. to prevent denial of service
996: attacks, to guard against running out of memory, or to work around
1.155 ihickson 997: platform-specific limitations.<h3 id="dependencies"><span class="secno">2.1 </span>Dependencies</h3><p>This specification relies on several other underlying
1.226 ihickson 998: specifications.<dl><dt>HTML</dt>
1.49 ihickson 999:
1.81 ihickson 1000: <dd>
1.49 ihickson 1001:
1.226 ihickson 1002: <p>Many fundamental concepts from HTML are used by this
1003: specification. <a href="#refsHTML">[HTML]</a></p>
1.49 ihickson 1004:
1.81 ihickson 1005: </dd>
1.1 ihickson 1006:
1.81 ihickson 1007: <dt>WebIDL</dt>
1.1 ihickson 1008:
1009: <dd>
1010:
1.81 ihickson 1011: <p>The IDL blocks in this specification use the semantics of the
1.153 ihickson 1012: WebIDL specification. <a href="#refsWEBIDL">[WEBIDL]</a></p>
1.1 ihickson 1013:
1.81 ihickson 1014: </dd>
1.1 ihickson 1015:
1.155 ihickson 1016: </dl><h2 id="terminology"><span class="secno">3 </span>Terminology</h2><p>The construction "a <code title="">Foo</code> object", where
1.81 ihickson 1017: <code title="">Foo</code> is actually an interface, is sometimes
1018: used instead of the more accurate "an object implementing the
1.155 ihickson 1019: interface <code title="">Foo</code>".<p>The term DOM is used to refer to the API set made available to
1.81 ihickson 1020: scripts in Web applications, and does not necessarily imply the
1021: existence of an actual <code>Document</code> object or of any other
1022: <code>Node</code> objects as defined in the DOM Core
1.171 ihickson 1023: specifications. <a href="#refsDOMCORE">[DOMCORE]</a><p>An IDL attribute is said to be <em>getting</em> when its value is
1.81 ihickson 1024: being retrieved (e.g. by author script), and is said to be
1.155 ihickson 1025: <em>setting</em> when a new value is assigned to it.<p>The term "JavaScript" is used to refer to ECMA262, rather than
1.103 ihickson 1026: the official term ECMAScript, since the term JavaScript is more
1.155 ihickson 1027: widely known. <a href="#refsECMA262">[ECMA262]</a><h2 id="infrastructure"><span class="secno">4 </span>Infrastructure</h2><p>There are two kinds of workers; dedicated workers, and shared
1.81 ihickson 1028: workers. Dedicated workers, once created, and are linked to their
1029: creator; but message ports can be used to communicate from a
1030: dedicated worker to multiple other browsing contexts or
1031: workers. Shared workers, on the other hand, are named, and once
1032: created any script running in the same <span>origin</span> can
1.155 ihickson 1033: obtain a reference to that worker and communicate with it.<h3 id="the-global-scope"><span class="secno">4.1 </span>The global scope</h3><p>The global scope is the "inside" of a worker.<h4 id="the-workerglobalscope-abstract-interface"><span class="secno">4.1.1 </span>The <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> abstract interface</h4><pre class="idl">interface <dfn id="workerglobalscope">WorkerGlobalScope</dfn> {
1.115 ihickson 1034: readonly attribute <a href="#workerglobalscope">WorkerGlobalScope</a> <a href="#dom-workerglobalscope-self" title="dom-WorkerGlobalScope-self">self</a>;
1035: readonly attribute <a href="#workerlocation">WorkerLocation</a> <a href="#dom-workerglobalscope-location" title="dom-WorkerGlobalScope-location">location</a>;
1036:
1037: void <a href="#dom-workerglobalscope-close" title="dom-WorkerGlobalScope-close">close</a>();
1.144 ihickson 1038: <!-- v2-onclose attribute <span>Function</span> <span title="handler-WorkerGlobalScope-onclose">onclose</span>;
1039: --> attribute <span>Function</span> <a href="#handler-workerglobalscope-onerror" title="handler-WorkerGlobalScope-onerror">onerror</a>;
1.150 ihickson 1040: };
1.172 ihickson 1041: <a href="#workerglobalscope">WorkerGlobalScope</a> implements <a href="#workerutils">WorkerUtils</a>;
1042: <a href="#workerglobalscope">WorkerGlobalScope</a> implements <span>EventTarget</span>;</pre><p>The <dfn id="dom-workerglobalscope-self" title="dom-WorkerGlobalScope-self"><code>self</code></dfn> attribute
1.155 ihickson 1043: must return the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object itself.<p>The <dfn id="dom-workerglobalscope-location" title="dom-WorkerGlobalScope-location"><code>location</code></dfn>
1.115 ihickson 1044: attribute must return the <code><a href="#workerlocation">WorkerLocation</a></code> object created
1045: for the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object when the worker was
1.81 ihickson 1046: created. It represents the <span>absolute URL</span> of the script
1.155 ihickson 1047: that was used to initialize the worker, after any redirects.<hr><p>When a script invokes the <dfn id="dom-workerglobalscope-close" title="dom-WorkerGlobalScope-close"><code>close()</code></dfn>
1.123 ihickson 1048: method on a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, the user agent
1.155 ihickson 1049: must run the following steps (atomically):<ol><li><p>Discard any <span title="concept-task">tasks</span> that
1.123 ihickson 1050: have been added to the <span>event loop</span>'s <span title="task
1051: queue">task queues</span>.</p>
1052:
1053: <!-- v2-onclose
1054: <li><p><span>Queue a task</span> to <span>fire a simple
1.179 ihickson 1055: event</span> named <code title="event-close">close</code> at the
1.123 ihickson 1056: <code>WorkerGlobalScope</code> object.</p></li>
1057: -->
1.81 ihickson 1058:
1.115 ihickson 1059: <li><p>Set the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's
1060: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.123 ihickson 1061: true. (This prevents any further tasks from being queued.)</li>
1.81 ihickson 1062:
1.124 ihickson 1063: <li><p>Disentangle all the ports in the list of <a href="#the-worker-s-ports">the worker's
1.123 ihickson 1064: ports</a>.</li>
1.81 ihickson 1065:
1.177 ihickson 1066: </ol><p>The following are the <span>event handlers</span> (and their
1067: corresponding <span title="event handler event type">event handler
1068: event types</span>) that must be supported, as IDL attributes, by
1069: objects implementing the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1070: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1071: <tbody><!-- v2-onclose <tr><td><dfn title="handler-WorkerGlobalScope-onclose"><code>onclose</code></dfn> <td> <code title="event-close">close</code> --><tr><td><dfn id="handler-workerglobalscope-onerror" title="handler-WorkerGlobalScope-onerror"><code>onerror</code></dfn> <td> <code title="event-error">error</code>
1.209 ihickson 1072: </table><hr><p>The <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> interface must not exist if
1073: the interface's <span>relevant namespace object</span> is a
1074: <code>Window</code> object. <a href="#refsWEBIDL">[WEBIDL]</a><h4 id="dedicated-workers-and-the-dedicatedworkerglobalscope-interface"><span class="secno">4.1.2 </span>Dedicated workers and the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> interface</h4><pre class="idl">[Supplemental, NoInterfaceObject]
1.150 ihickson 1075: interface <dfn id="dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</dfn> : <a href="#workerglobalscope">WorkerGlobalScope</a> {
1.174 ihickson 1076: void <a href="#dom-dedicatedworkerglobalscope-postmessage" title="dom-DedicatedWorkerGlobalScope-postMessage">postMessage</a>(in any message, in optional <span>MessagePortArray</span> ports);<!--
1.77 ihickson 1077: <span>MessagePort</span> <span title="dom-DedicatedWorkerGlobalScope-startConversation">startConversation</span>(in any message);-->
1.144 ihickson 1078: attribute <span>Function</span> <a href="#handler-dedicatedworkerglobalscope-onmessage" title="handler-DedicatedWorkerGlobalScope-onmessage">onmessage</a>;
1.155 ihickson 1079: };</pre><p><code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> objects act as if they
1.81 ihickson 1080: had an implicit <code>MessagePort</code> associated with them. This
1081: port is part of a channel that is set up when the worker is created,
1082: but it is not exposed. This object must never be garbage collected
1.155 ihickson 1083: before the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object.<p>All messages received by that port must immediately be retargeted
1084: at the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object.<p>The <dfn id="dom-dedicatedworkerglobalscope-postmessage" title="dom-DedicatedWorkerGlobalScope-postMessage"><code>postMessage()</code></dfn><!--
1.64 ihickson 1085: and <dfn
1086: title="dom-DedicatedWorkerGlobalScope-startConversation"><code>startConversation()</code></dfn>-->
1.81 ihickson 1087: method<!--s (startConversation)--> on
1.115 ihickson 1088: <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> objects must act as if, when
1.81 ihickson 1089: invoked, it<!--/they (startConversation)--> immediately invoked the
1090: method of the same name on the port, with the same arguments, and
1.177 ihickson 1091: returned the same return value.<p>The following are the <span>event handlers</span> (and their
1092: corresponding <span title="event handler event type">event handler
1093: event types</span>) that must be supported, as IDL attributes, by
1094: objects implementing the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
1095: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1096: <tbody><tr><td><dfn id="handler-dedicatedworkerglobalscope-onmessage" title="handler-DedicatedWorkerGlobalScope-onmessage"><code>onmessage</code></dfn> <td> <code title="event-message">message</code>
1.191 ihickson 1097: </table><p>For the purposes of the <span>application cache</span> networking
1098: model, a dedicated worker is an extension of the <span>cache
1099: host</span> from which it was created.<h4 id="shared-workers-and-the-sharedworkerglobalscope-inteface"><span class="secno">4.1.3 </span>Shared workers and the <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> inteface</h4><pre class="idl">[Supplemental, NoInterfaceObject]
1.150 ihickson 1100: interface <dfn id="sharedworkerglobalscope">SharedWorkerGlobalScope</dfn> : <a href="#workerglobalscope">WorkerGlobalScope</a> {
1.115 ihickson 1101: readonly attribute DOMString <a href="#dom-sharedworkerglobalscope-name" title="dom-SharedWorkerGlobalScope-name">name</a>;
1.181 ihickson 1102: readonly attribute <span>ApplicationCache</span> <span title="dom-SharedWorkerGlobalScope-applicationCache">applicationCache</span>;
1.144 ihickson 1103: attribute <span>Function</span> <a href="#handler-sharedworkerglobalscope-onconnect" title="handler-SharedWorkerGlobalScope-onconnect">onconnect</a>;
1.155 ihickson 1104: };</pre><p>Shared workers receive message ports through <code title="event-WorkerGlobalScope-connect">connect</code> events on
1105: their global object for each connection.<p>The <dfn id="dom-sharedworkerglobalscope-name" title="dom-SharedWorkerGlobalScope-name"><code>name</code></dfn>
1.81 ihickson 1106: attribute must return the value it was assigned when the
1.115 ihickson 1107: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object was created by the
1108: "<a href="#run-a-worker">run a worker</a>" algorithm. Its value represents the name
1.81 ihickson 1109: that can be used to obtain a reference to the worker using the
1.177 ihickson 1110: <code><a href="#sharedworker">SharedWorker</a></code> constructor.<p>The following are the <span>event handlers</span> (and their
1111: corresponding <span title="event handler event type">event handler
1112: event types</span>) that must be supported, as IDL attributes, by
1113: objects implementing the <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1114: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1115: <tbody><tr><td><dfn id="handler-sharedworkerglobalscope-onconnect" title="handler-SharedWorkerGlobalScope-onconnect"><code>onconnect</code></dfn> <td> <code title="event-connect">connect</code>
1.191 ihickson 1116: </table><p>For the purposes of the <span>application cache</span> networking
1117: model, a shared worker is its own <span>cache host</span>. The
1118: <a href="#run-a-worker">run a worker</a> algorithm takes care of associating the
1119: worker with an <span>application cache</span>.<p class="note">The <code title="dom-SharedWorkerGlobalScope-applicationCache">applicationCache</code>
1.123 ihickson 1120: attribute returns the <code>ApplicationCache</code> object for the
1.101 ihickson 1121: worker.</p><!-- normative conf criteria is in the appcache section
1.160 ihickson 1122: --><h3 id="origins-of-workers"><span class="secno">4.2 </span>Origins of workers</h3><p>Both the <span>origin</span> and <span>effective script
1.81 ihickson 1123: origin</span> of scripts running in workers are the
1124: <span>origin</span> of the <span>absolute URL</span> given in that
1.115 ihickson 1125: the worker's <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1.186 ihickson 1126: represents.<h3 id="the-event-loop"><span class="secno">4.3 </span>The event loop</h3><p>Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object has an <span>event
1.128 ihickson 1127: loop</span> distinct from those defined for <span title="unit of
1128: related similar-origin browsing contexts">units of related
1129: similar-origin browsing contexts</span>. This <span>event
1130: loop</span> has no associated <span>browsing context</span>, and its
1131: <span title="task queue">task queues</span> only have events,
1132: callbacks, and networking activity as <span title="concept-task">tasks</span>. The processing model of these
1133: <span title="event loop">event loops</span> is defined below in the
1.155 ihickson 1134: <a href="#run-a-worker">run a worker</a> algorithm.<p>Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object also has a <dfn id="dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</dfn> flag, which must
1.81 ihickson 1135: initially be false, but which can get set to true by the algorithms
1.155 ihickson 1136: in the processing model section below.<p>Once the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is set to
1.81 ihickson 1137: true, the <span>event loop</span>'s <span title="task queue">task
1.115 ihickson 1138: queues</span> must discard any further <span title="concept-task">tasks</span> that would be added to them (tasks
1.175 ihickson 1139: already on the queue are unaffected except where otherwise
1.115 ihickson 1140: specified). Effectively, once the <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is true,
1.81 ihickson 1141: timers stop firing, notifications for all pending asynchronous
1.186 ihickson 1142: operations are dropped, etc.<h3 id="the-worker-s-lifetime"><span class="secno">4.4 </span>The worker's lifetime</h3><p>Workers communicate with other workers and with <span title="browsing context">browsing contexts</span> through <span title="channel messaging">message channels</span> and their
1.155 ihickson 1143: <code>MessagePort</code> objects.<p>Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> <var title="">worker global
1.124 ihickson 1144: scope</var> has a list of <dfn id="the-worker-s-ports">the worker's ports</dfn>, which
1.81 ihickson 1145: consists of all the <code>MessagePort</code> objects that are
1146: entangled with another port and that have one (but only one) port
1147: owned by <var title="">worker global scope</var>. This list includes
1148: <!--all the <code>MessagePort</code> objects that are in events
1.68 ihickson 1149: pending in the <span>event loop</span>, as well as (commented out
1150: because in practice it makes no difference either way as far as I
1151: can tell, and it would be hard to strictly implement since these
1.81 ihickson 1152: ports might not yet be across the thread boundary)--> the implicit
1.155 ihickson 1153: <code>MessagePort</code> in the case of <a href="#dedicatedworkerglobalscope" title="DedicatedWorkerGlobalScope">dedicated workers</a>.<p>Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> also has a list of <dfn id="the-worker-s-workers">the
1.124 ihickson 1154: worker's workers</dfn>. Initially this list is empty; it is
1.155 ihickson 1155: populated when the worker creates or obtains further workers.<p>Finally, each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> also has a list of
1.124 ihickson 1156: <dfn id="the-worker-s-documents">the worker's <code>Document</code>s</dfn>. Initially this list
1.155 ihickson 1157: is empty; it is populated when the worker is created.<p>Whenever a <code>Document</code> <var title="">d</var> is <dfn id="add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">added to the
1.123 ihickson 1158: worker's <code>Document</code>s</dfn>, the user agent must, for each
1.124 ihickson 1159: worker in the list of <a href="#the-worker-s-workers">the worker's workers</a> whose list
1160: of <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> does not contain
1161: <var title="">d</var>, <a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's
1.123 ihickson 1162: documents">add <var title="">d</var> to <var title="">q</var>'s
1163: <code>WorkerGlobalScope</code> owner's list of <span>the worker's
1.155 ihickson 1164: <code>Document</code>s</span></a>.</p><!-- suggestions welcome
1165: on making this sentence into understandable English --><p>Whenever a <code>Document</code> object is <span title="discard a
1.123 ihickson 1166: Document">discarded</span>, it must be removed from the list of
1167: <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> of each worker
1.192 ihickson 1168: whose list contains that <code>Document</code>.<p>Given a <span>script's global object</span> <var title="">o</var>
1.123 ihickson 1169: when creating or obtaining a worker, the <dfn id="list-of-relevant-document-objects-to-add">list of relevant
1170: <code>Document</code> objects to add</dfn> depends on the type of
1171: <var title="">o</var>. If <var title="">o</var> is a
1172: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object (i.e. if we are creating a
1173: nested worker), then the relevant <code>Document</code>s are the
1174: <code>Document</code>s that are in <var title="">o</var>'s own list
1175: of <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a>. Otherwise, <var title="">o</var> is a <code>Window</code> object, and the relevant
1176: <code>Document</code> is just the <code>Document</code> that is the
1.155 ihickson 1177: <span>active document</span> of the <code>Window</code> object <var title="">o</var>.<hr><p>A worker is said to be a <dfn id="permissible-worker">permissible worker</dfn> if its
1.123 ihickson 1178: list of <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> is not
1.155 ihickson 1179: empty.<p>A worker is said to be a <dfn id="protected-worker">protected worker</dfn> if it is a
1.123 ihickson 1180: <a href="#permissible-worker">permissible worker</a> and either it has outstanding
1181: timers, database transactions, or network connections, or its list
1.124 ihickson 1182: of <a href="#the-worker-s-ports">the worker's ports</a> is not empty, or its
1.123 ihickson 1183: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> is actually a
1184: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object (i.e. the worker is a
1.155 ihickson 1185: shared worker).<p>A worker is said to be an <dfn id="active-needed-worker">active needed worker</dfn> if any
1.123 ihickson 1186: of the <code>Document</code> objects in <a href="#the-worker-s-documents">the worker's
1.155 ihickson 1187: <code>Document</code>s</a> are <span>fully active</span>.<p>A worker is said to be a <dfn id="suspendable-worker">suspendable worker</dfn> if it is
1.123 ihickson 1188: not an <a href="#active-needed-worker">active needed worker</a> but it is a
1.186 ihickson 1189: <a href="#permissible-worker">permissible worker</a>.<h3 id="processing-model"><span class="secno">4.5 </span>Processing model</h3><p>When a user agent is to <dfn id="run-a-worker">run a worker</dfn> for a script with
1.176 ihickson 1190: <span>URL</span> <var title="">url</var>, a browsing context <var title="">owner browsing context</var>, an origin <var title="">owner
1191: origin</var>, and with global scope <var title="">worker global
1192: scope</var>, it must run the following steps:<ol><li>
1.81 ihickson 1193:
1194: <p>Create a completely separate and parallel execution environment
1195: (i.e. a separate thread or process or equivalent construct), and
1.106 ihickson 1196: run the rest of these steps asynchronously in that context.</p>
1.81 ihickson 1197:
1198: </li>
1.4 ihickson 1199:
1.101 ihickson 1200: <li><p>If <var title="">worker global scope</var> is actually a
1.115 ihickson 1201: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object (i.e. the worker is a
1.101 ihickson 1202: shared worker), and there are any <span title="relevant application
1203: cache">relevant application caches</span> that are identified by a
1204: manifest URL with the <span>same origin</span> as <var title="">url</var> and that have <var title="">url</var> as one of
1.115 ihickson 1205: their entries, <em>not</em> excluding entries marked as <span title="concept-appcache-foreign">foreign</span>, then associate the
1206: <var title="">worker global scope</var> with the <span title="concept-appcache-selection">most appropriate application
1.101 ihickson 1207: cache</span> of those that match.</li>
1208:
1.4 ihickson 1209: <li>
1.52 ihickson 1210:
1.176 ihickson 1211: <p>Attempt to <span>fetch</span> the resource identified by <var title="">url</var>, from the <var title="">owner origin</var>.</p>
1212: <!-- not http-origin privacy sensitive -->
1.81 ihickson 1213:
1.129 ihickson 1214: <p>If the attempt fails, or if the attempt involves any redirects
1215: to URIs that do not have the <span>same origin</span> as <var title="">url</var> (even if the final URI is at the <span>same
1216: origin</span> as the original <var title="">url</var>), then for
1217: each <code><a href="#worker">Worker</a></code> or <code><a href="#sharedworker">SharedWorker</a></code> object
1218: associated with <var title="">worker global scope</var>,
1219: <span>queue a task</span> to <span>fire a simple event</span>
1.179 ihickson 1220: named <code title="event-error">error</code> at that
1.129 ihickson 1221: object. Abort these steps.</p>
1.7 ihickson 1222:
1.186 ihickson 1223: <p>If the attempt succeeds, then convert the script resource to
1224: Unicode by assuming it was encoded as UTF-8, to obtain its <var title="">source</var>.</p>
1.81 ihickson 1225:
1.68 ihickson 1226: <p>Let <var title="">language</var> be JavaScript.</p>
1.7 ihickson 1227:
1.115 ihickson 1228: <p class="note">As with <code>script</code> elements, the MIME
1.81 ihickson 1229: type of the script is ignored. Unlike with <code>script</code>
1230: elements, there is no way to override the type. It's always
1.170 ihickson 1231: assumed to be JavaScript.</p>
1.81 ihickson 1232:
1233: </li>
1.7 ihickson 1234:
1235: <li>
1.68 ihickson 1236:
1.115 ihickson 1237: <p>A new <span title="concept-script">script</span> is now
1.81 ihickson 1238: created, as follows.</p>
1239:
1240: <p>Create a new <span>script execution environment</span>
1241: set up as appropriate for the scripting language <var title="">language</var>.</p>
1.34 ihickson 1242:
1.68 ihickson 1243: <p>Parse/compile/initialize <var title="">source</var> using that
1.81 ihickson 1244: <span>script execution environment</span>, as appropriate for <var title="">language</var>, and thus obtain a <span>list of code
1245: entry-points</span>; set the <i>initial code entry-point</i> to
1246: the entry-point for any executable code to be immediately run.</p>
1247:
1248: <p>Set the <span>script's global object</span> to <var title="">worker global scope</var>.</p>
1249:
1250: <p>Set the <span>script's browsing context</span> to <var title="">owner browsing context</var>.</p>
1251:
1.83 ihickson 1252: <p>Set the <span>script's URL character encoding</span> to
1.81 ihickson 1253: UTF-8. (This is just used for encoding non-ASCII characters in the
1254: query component of URLs.)</p>
1.68 ihickson 1255:
1256: <p>Set the <span>script's base URL</span> to <var title="">url</var>.</p>
1.4 ihickson 1257:
1.81 ihickson 1258: </li>
1.4 ihickson 1259:
1260: <li>
1.81 ihickson 1261:
1262: <p><strong>Closing orphan workers</strong>: Start monitoring the
1.125 ihickson 1263: worker such that no sooner than it stops being either a
1264: <a href="#protected-worker">protected worker</a> or a <a href="#suspendable-worker">suspendable
1.123 ihickson 1265: worker</a>, and no later than it stops being a
1266: <a href="#permissible-worker">permissible worker</a>, <var title="">worker global
1267: scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is set
1268: to true<!-- v2-onclose and <span title="queue a task">a task is
1.179 ihickson 1269: queued</span> to <span>fire a simple event</span> named <code
1.123 ihickson 1270: title="event-close">close</code> at <var title="">worker global
1271: scope</var>-->.</p>
1.81 ihickson 1272:
1273: </li>
1.9 ihickson 1274:
1275: <li>
1.7 ihickson 1276:
1.81 ihickson 1277: <p><strong>Suspending workers</strong>: Start monitoring the
1278: worker, such that whenever <var title="">worker global
1.115 ihickson 1279: scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is false
1280: and the worker is a <a href="#suspendable-worker">suspendable worker</a>, the user
1.81 ihickson 1281: agent suspends execution of script in that worker until such time
1.115 ihickson 1282: as either the <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag switches
1283: to true or the worker stops being a <a href="#suspendable-worker">suspendable
1.81 ihickson 1284: worker</a>.</p>
1.4 ihickson 1285:
1.81 ihickson 1286: </li>
1.68 ihickson 1287:
1288: <li>
1.4 ihickson 1289:
1.81 ihickson 1290: <p><span title="jump to a code entry-point">Jump</span> to the
1.115 ihickson 1291: <span title="concept-script">script</span>'s <i>initial code
1.81 ihickson 1292: entry-point</i>, and let that run until it either returns, fails
1293: to catch an exception, or gets prematurely aborted by the
1.115 ihickson 1294: "<a href="#kill-a-worker">kill a worker</a>" or "<a href="#terminate-a-worker">terminate a worker</a>"
1.81 ihickson 1295: algorithms defined below.</p>
1296:
1.149 ihickson 1297: <!-- v2-onclose
1298: <p class="note">If the script gets aborted by the "<span>kill a
1299: worker</span>" algorithm, then that same algorithm will cause
1.115 ihickson 1300: there to only be a single <span title="concept-task">task</span>
1.81 ihickson 1301: in the <span>event loop</span> at the next step, namely the task
1.115 ihickson 1302: for the <code title="message-close">close</code> event. The
1.149 ihickson 1303: "<span>terminate a worker</span>" algorithm removes all the
1.81 ihickson 1304: events.</p>
1.149 ihickson 1305: -->
1.4 ihickson 1306:
1.81 ihickson 1307: </li>
1.4 ihickson 1308:
1.95 ihickson 1309: <li><p>If <var title="">worker global scope</var> is actually a
1.115 ihickson 1310: <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object (i.e. the worker is
1.126 ihickson 1311: a dedicated worker), then enable the <span>port message
1312: queue</span> of the worker's implicit port.</li>
1.95 ihickson 1313:
1.4 ihickson 1314: <li>
1.68 ihickson 1315:
1.115 ihickson 1316: <p><i title="">Event loop</i>: Wait until either there is a <span title="concept-task">task</span> in one of the <span>event
1317: loop</span>'s <span title="task queue">task queues</span> or <var title="">worker global scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is set
1.81 ihickson 1318: to true.</p>
1.43 ihickson 1319:
1.81 ihickson 1320: </li>
1.4 ihickson 1321:
1322: <li>
1323:
1.81 ihickson 1324: <p>Run the oldest task on one of the <span>event loop</span>'s
1325: <span title="task queue">task queues</span>, if any. The user
1326: agent may pick any <span>task queue</span>.</p>
1327:
1.115 ihickson 1328: <p class="note">The handling of events or the execution of
1329: callbacks might get prematurely aborted by the "<a href="#kill-a-worker">kill a
1330: worker</a>" or "<a href="#terminate-a-worker">terminate a worker</a>" algorithms
1.81 ihickson 1331: defined below.</p>
1.8 ihickson 1332:
1.81 ihickson 1333: </li>
1.4 ihickson 1334:
1335: <li>
1336:
1.81 ihickson 1337: <p>Remove the task run in the previous step, if any, from its
1338: <span>task queue</span>.</p>
1.4 ihickson 1339:
1.81 ihickson 1340: </li>
1.4 ihickson 1341:
1342: <li>
1.8 ihickson 1343:
1.81 ihickson 1344: <p>If there are any more events in the <span>event loop</span>'s
1.115 ihickson 1345: <span title="task queue">task queues</span> or if <var title="">worker global scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is set
1.81 ihickson 1346: to false, then jump back to the step above labeled <i>event
1347: loop</i>.</p>
1.8 ihickson 1348:
1.81 ihickson 1349: </li>
1.8 ihickson 1350:
1351: <li>
1.71 ihickson 1352:
1.123 ihickson 1353: <p>If there are any outstanding transactions that have callbacks
1354: that involve <span title="concept-script">scripts</span> whose
1355: <span title="script's global object">global object</span> is the
1356: <var title="">worker global scope</var>, roll them back (without
1357: invoking any of the callbacks).</p>
1.50 ihickson 1358:
1.123 ihickson 1359: </li>
1360:
1361: <li>
1362:
1363: <p>Empty the <var title="">worker global scope</var>'s <span>list
1364: of active timeouts</span> and its <span>list of active
1365: intervals</span>.</p>
1.50 ihickson 1366:
1.81 ihickson 1367: </li>
1.50 ihickson 1368:
1.123 ihickson 1369: <!-- v2-onclose
1.81 ihickson 1370: <li>
1.50 ihickson 1371:
1.123 ihickson 1372: <p>For each <code>Worker</code> or <code>SharedWorker</code>
1.81 ihickson 1373: object associated with <var title="">worker global scope</var>,
1374: <span>queue a task</span> to <span>fire a simple event</span>
1.179 ihickson 1375: named <code title="event-close">close</code> at that object.</p>
1.5 ihickson 1376:
1.81 ihickson 1377: </li>
1.123 ihickson 1378: -->
1.155 ihickson 1379: </ol><hr><p>When a user agent is to <dfn id="kill-a-worker">kill a worker</dfn> it must
1.81 ihickson 1380: run the following steps in parallel with the worker's main loop (the
1.155 ihickson 1381: "<a href="#run-a-worker">run a worker</a>" processing model defined above):<ol><!-- v2-onclose
1.123 ihickson 1382: <li><p>If the worker's <code>WorkerGlobalScope</code> object's
1383: <span title="dom-WorkerGlobalScope-closing">closing</span> flag is
1.81 ihickson 1384: false, <span>queue a task</span> to <span>fire a simple
1.179 ihickson 1385: event</span> named <code title="event-close">close</code> at the
1.123 ihickson 1386: worker's <code>WorkerGlobalScope</code> object.</p></li>
1.155 ihickson 1387: --><li><p>Set the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.81 ihickson 1388: true.</li>
1389:
1.123 ihickson 1390: <!-- v2-onclose
1391: <li><p>Wait a user-agent-defined amount of time. If the "<span>run
1392: a worker</span>" processing model defined above immediately starts
1393: running event listeners registered for the <code
1394: title="event-close">close</code> event, this time should not be
1395: zero — the idea is that the <code
1396: title="event-close">close</code> event can be used to clean up
1397: when shutting down unexpectedly.</p></li>
1398: -->
1.81 ihickson 1399:
1.115 ihickson 1400: <li><p>If there are any <span title="concept-task">tasks</span>
1.81 ihickson 1401: queued in the <span>event loop</span>'s <span title="task
1.123 ihickson 1402: queue">task queues</span><!-- v2-onclose other than the <code
1403: title="event-close">close</code> event that this algorithm just
1404: added-->, discard them without processing them.</li>
1.81 ihickson 1405:
1.123 ihickson 1406: <!-- v2-onclose
1.115 ihickson 1407: <li><p>If the <code title="event-close">close</code> event that
1.81 ihickson 1408: this algorithm just queued hasn't yet been dispatched, then abort
1.123 ihickson 1409: the script currently running in the worker.</p></li>
1410: -->
1.81 ihickson 1411:
1412: <li><p>Wait a user-agent-defined amount of time.</li>
1413:
1.123 ihickson 1414: <li><p>Abort the script currently running in the worker<!--
1415: v2-onclose (if any script is running, then it will be a handler for
1416: the <code title="event-close">close</code> event)-->.</li>
1.81 ihickson 1417:
1.155 ihickson 1418: </ol><p>User agents may invoke the "<a href="#kill-a-worker">kill a worker</a>"
1.81 ihickson 1419: processing model on a worker at any time, e.g. in response to user
1420: requests, in response to CPU quota management, or when a worker
1.115 ihickson 1421: stops being an <a href="#active-needed-worker">active needed worker</a> if the worker
1422: continues executing even after its <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag was
1.155 ihickson 1423: set to true.<hr><p>When a user agent is to <dfn id="terminate-a-worker">terminate a worker</dfn> it must run
1.81 ihickson 1424: the following steps in parallel with the worker's main loop (the
1.155 ihickson 1425: "<a href="#run-a-worker">run a worker</a>" processing model defined above):<ol><li><p>Set the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's
1.115 ihickson 1426: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.81 ihickson 1427: true.</li>
1428:
1.115 ihickson 1429: <li><p>If there are any <span title="concept-task">tasks</span>
1.81 ihickson 1430: queued in the <span>event loop</span>'s <span title="task
1431: queue">task queues</span>, discard them without processing
1432: them.</li>
1433:
1434: <li><p>Abort the script currently running in the worker.</li>
1435:
1.115 ihickson 1436: <li><p>If the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object is
1437: actually a <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object (i.e. the
1.81 ihickson 1438: worker is a dedicated worker), then empty the <span>port message
1439: queue</span> of the port that the worker's implicit port is
1440: entangled with.</li>
1441:
1.155 ihickson 1442: </ol><hr><p>The <span>task source</span> for the tasks mentioned above is the
1.186 ihickson 1443: <span>DOM manipulation task source</span>.<h3 id="runtime-script-errors"><span class="secno">4.6 </span>Runtime script errors</h3><p>Whenever an uncaught runtime script error occurs in one of the
1.143 ihickson 1444: worker's scripts, if the error did not occur while handling a
1445: previous script error, the user agent must <span>report the
1446: error</span> using the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's <code title="handler-WorkerGlobalScope-onerror"><a href="#handler-workerglobalscope-onerror">onerror</a></code>
1.205 ihickson 1447: attribute.
1448:
1.226 ihickson 1449: <a href="#refsHTML">[HTML]</a>
1.205 ihickson 1450:
1451: <p>For shared workers, if the error is still <i title="concept-error-nothandled">not handled</i> afterwards, or if
1.132 ihickson 1452: the error occurred while handling a previous script error, the error
1.215 ihickson 1453: may be reported to the user.
1.205 ihickson 1454:
1.226 ihickson 1455: <a href="#refsHTML">[HTML]</a>
1.205 ihickson 1456:
1457: <p>For dedicated workers, if the error is still <i title="concept-error-nothandled">not handled</i> afterwards, or if
1.132 ihickson 1458: the error occurred while handling a previous script error, the user
1.123 ihickson 1459: agent must <span>queue a task</span> to <a href="#fire-a-worker-error-event">fire a worker error
1460: event</a> at the <code><a href="#worker">Worker</a></code> object associated with the
1.155 ihickson 1461: worker.<p>When the user agent is to <dfn id="fire-a-worker-error-event">fire a worker error event</dfn> at
1.118 ihickson 1462: a <code><a href="#worker">Worker</a></code> object, it must dispatch an event that uses
1463: the <code><a href="#errorevent">ErrorEvent</a></code> interface, with the name <code title="event-error">error</code>, that doesn't bubble and is
1.115 ihickson 1464: cancelable, with its <code title="dom-ErrorEvent-message"><a href="#dom-errorevent-message">message</a></code>, <code title="dom-ErrorEvent-filename"><a href="#dom-errorevent-filename">filename</a></code>, and <code title="dom-ErrorEvent-lineno"><a href="#dom-errorevent-lineno">lineno</a></code> attributes set
1.81 ihickson 1465: appropriately. The default action of this event depends on whether
1.115 ihickson 1466: the <code><a href="#worker">Worker</a></code> object is itself in a worker. If it is, and
1.81 ihickson 1467: that worker is also a dedicated worker, then the user agent must
1.118 ihickson 1468: again <span>queue a task</span> to <a href="#fire-a-worker-error-event">fire a worker error
1469: event</a> at the <code><a href="#worker">Worker</a></code> object associated with
1.215 ihickson 1470: <em>that</em> worker. Otherwise, then the error may be reported
1.155 ihickson 1471: to the user.<p>The <span>task source</span> for the tasks mentioned above is the
1472: <span>DOM manipulation task source</span>.<hr><pre class="idl">interface <dfn id="errorevent">ErrorEvent</dfn> : Event {
1.147 ihickson 1473: readonly attribute DOMString <a href="#dom-errorevent-message" title="dom-ErrorEvent-message">message</a>;
1474: readonly attribute DOMString <a href="#dom-errorevent-filename" title="dom-ErrorEvent-filename">filename</a>;
1.115 ihickson 1475: readonly attribute unsigned long <a href="#dom-errorevent-lineno" title="dom-ErrorEvent-lineno">lineno</a>;
1.147 ihickson 1476: void <a href="#dom-errorevent-initerrorevent" title="dom-ErrorEvent-initErrorEvent">initErrorEvent</a>(in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in DOMString messageArg, in DOMString filenameArg, in unsigned long linenoArg);
1.155 ihickson 1477: };</pre><p>The <dfn id="dom-errorevent-initerrorevent" title="dom-ErrorEvent-initErrorEvent"><code>initErrorEvent()</code></dfn>
1.190 ihickson 1478: method must initialize the event in a manner analogous to the
1479: similarly-named method in the DOM Events interfaces. <a href="#refsDOMEVENTS">[DOMEVENTS]</a><p>The <dfn id="dom-errorevent-message" title="dom-ErrorEvent-message"><code>message</code></dfn>
1.155 ihickson 1480: attribute represents the error message.<p>The <dfn id="dom-errorevent-filename" title="dom-ErrorEvent-filename"><code>filename</code></dfn>
1.81 ihickson 1481: attribute represents the <span>absolute URL</span> of the script in
1.155 ihickson 1482: which the error originally occurred.<p>The <dfn id="dom-errorevent-lineno" title="dom-ErrorEvent-lineno"><code>lineno</code></dfn>
1.132 ihickson 1483: attribute represents the line number where the error occurred in the
1.208 ihickson 1484: script.<h3 id="creating-workers"><span class="secno">4.7 </span>Creating workers</h3><h4 id="the-abstractworker-abstract-interface"><span class="secno">4.7.1 </span>The <code><a href="#abstractworker">AbstractWorker</a></code> abstract interface</h4><pre class="idl">[Supplemental, NoInterfaceObject]
1485: interface <dfn id="abstractworker">AbstractWorker</dfn> {
1.144 ihickson 1486: attribute <span>Function</span> <a href="#handler-abstractworker-onerror" title="handler-AbstractWorker-onerror">onerror</a>;
1487: <!-- v2-onclose attribute <span>Function</span> <span title="handler-AbstractWorker-onclose">onclose</span>; -->
1.172 ihickson 1488: };
1.177 ihickson 1489: <a href="#abstractworker">AbstractWorker</a> implements <span>EventTarget</span>;</pre><p>The following are the <span>event handlers</span> (and their
1490: corresponding <span title="event handler event type">event handler
1491: event types</span>) that must be supported, as IDL attributes, by
1492: objects implementing the <code><a href="#abstractworker">AbstractWorker</a></code> interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1493: <tbody><tr><td><dfn id="handler-abstractworker-onerror" title="handler-AbstractWorker-onerror"><code>onerror</code></dfn> <td> <code title="event-error">error</code>
1.123 ihickson 1494: <!-- v2-onclose <tr><td><dfn title="handler-AbstractWorker-onclose"><code>onclose</code></dfn> <td> <code title="event-close">close</code> -->
1.186 ihickson 1495: </table><h4 id="dedicated-workers-and-the-worker-interface"><span class="secno">4.7.2 </span>Dedicated workers and the <code><a href="#worker">Worker</a></code> interface</h4><pre class="idl">[<a href="#dom-worker" title="dom-Worker">Constructor</a>(in DOMString scriptURL)]
1.115 ihickson 1496: interface <dfn id="worker">Worker</dfn> : <a href="#abstractworker">AbstractWorker</a> {
1497: void <a href="#dom-worker-terminate" title="dom-Worker-terminate">terminate</a>();
1.50 ihickson 1498:
1.174 ihickson 1499: void <a href="#dom-worker-postmessage" title="dom-Worker-postMessage">postMessage</a>(in any message, in optional <span>MessagePortArray</span> ports);<!--
1.81 ihickson 1500: <span>MessagePort</span> <span title="dom-Worker-startConversation">startConversation</span>(in any message);-->
1.144 ihickson 1501: attribute <span>Function</span> <a href="#handler-worker-onmessage" title="handler-Worker-onmessage">onmessage</a>;
1.155 ihickson 1502: };</pre><p>The <dfn id="dom-worker-terminate" title="dom-Worker-terminate"><code>terminate()</code></dfn> method,
1.115 ihickson 1503: when invoked, must cause the "<a href="#terminate-a-worker">terminate a worker</a>"
1.81 ihickson 1504: algorithm to be run on the worker with with the object is
1.155 ihickson 1505: associated.<p><code><a href="#worker">Worker</a></code> objects act as if they had an implicit
1.81 ihickson 1506: <code>MessagePort</code> associated with them. This port is part of
1507: a channel that is set up when the worker is created, but it is not
1508: exposed. This object must never be garbage collected before the
1.155 ihickson 1509: <code><a href="#worker">Worker</a></code> object.<p>All messages received by that port must immediately be retargeted
1510: at the <code><a href="#worker">Worker</a></code> object.<p>The <dfn id="dom-worker-postmessage" title="dom-Worker-postMessage"><code>postMessage()</code></dfn><!--
1.64 ihickson 1511: and <dfn
1512: title="dom-Worker-startConversation"><code>startConversation()</code></dfn>-->
1.115 ihickson 1513: method<!--s (startConversation)--> on <code><a href="#worker">Worker</a></code> objects
1.81 ihickson 1514: must act as if, when invoked, it<!--/they (startConversation)-->
1515: immediately invoked the method of the same name on the port, with
1.177 ihickson 1516: the same arguments, and returned the same return value.<p>The following are the <span>event handlers</span> (and their
1517: corresponding <span title="event handler event type">event handler
1518: event types</span>) that must be supported, as IDL attributes, by
1519: objects implementing the <code><a href="#worker">Worker</a></code> interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1520: <tbody><tr><td><dfn id="handler-worker-onmessage" title="handler-Worker-onmessage"><code>onmessage</code></dfn> <td> <code title="event-message">message</code>
1521: </table><hr><p>When the <dfn id="dom-worker" title="dom-Worker"><code>Worker(<var title="">scriptURL</var>)</code></dfn> constructor is invoked, the
1.216 ihickson 1522: user agent must run the following steps:<ol><li><p><span title="resolve a url">Resolve</span> the <var title="">scriptURL</var> argument relative to the <span>entry
1.133 ihickson 1523: script</span>'s <span title="script's base URL">base URL</span>,
1524: when the method is invoked.</li>
1.9 ihickson 1525:
1.81 ihickson 1526: <li><p>If this fails, throw a <code>SYNTAX_ERR</code>
1527: exception.</li>
1.9 ihickson 1528:
1.167 ihickson 1529: <li>
1530:
1531: <p>If the <span>origin</span> of the resulting <span>absolute
1532: URL</span> is not the <span title="same origin">same</span> as the
1.216 ihickson 1533: origin of the <span>entry script</span>, then throw a
1.182 ihickson 1534: <code>SECURITY_ERR</code> exception.</p>
1.167 ihickson 1535:
1536: <p class="note">Thus, scripts must be external files with the same
1537: scheme as the original page: you can't load a script from a <code title="">data:</code> URL or <code title="">javascript:</code>
1538: URL, and a <code>http:</code> page couldn't start workers using
1539: scripts with <code>http:</code> URLs.</p>
1540:
1541: </li>
1.9 ihickson 1542:
1.185 ihickson 1543: <li><p>Create a new <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
1544: object. Let <var title="">worker global scope</var> be this new
1545: object.</li>
1.9 ihickson 1546:
1.115 ihickson 1547: <li><p>Create a new <code><a href="#worker">Worker</a></code> object, associated with
1.81 ihickson 1548: <var title="">worker global scope</var>. Let <var title="">worker</var> be this new object.</li>
1.50 ihickson 1549:
1.185 ihickson 1550: <li><p><span>Create a new <code>MessagePort</code> object</span>
1.192 ihickson 1551: owned by the <span title="script's global object">global
1552: object</span> of the <span title="concept-script">script</span> that
1.185 ihickson 1553: invoked the constructor. Let this be the <var title="">outside
1.81 ihickson 1554: port</var>.</li>
1.9 ihickson 1555:
1.81 ihickson 1556: <li><p>Associate the <var title="">outside port</var> with <var title="">worker</var>.</li>
1.50 ihickson 1557:
1.185 ihickson 1558: <li><p><span>Create a new <code>MessagePort</code> object</span>
1559: owned by <var title="">worker global scope</var>. Let <var title="">inside port</var> be this new object.</li>
1.50 ihickson 1560:
1.81 ihickson 1561: <li><p>Associate <var title="">inside port</var> with <var title="">worker global scope</var>.</li>
1.50 ihickson 1562:
1.81 ihickson 1563: <li><p><span>Entangle</span> <var title="">outside port</var> and
1564: <var title="">inside port</var>.</li>
1.50 ihickson 1565:
1.81 ihickson 1566: <li><p>Return <var title="">worker</var>, and run the following
1567: steps asynchronously.</li>
1.50 ihickson 1568:
1.204 ihickson 1569: <!-- (this is done by the "run a worker" algorithm)
1.126 ihickson 1570: <li><p>Enable <var title="">inside port</var>'s <span>port message
1.204 ihickson 1571: queue</span>.</p></li>
1572: -->
1.50 ihickson 1573:
1.126 ihickson 1574: <li><p>Enable <var title="">outside port</var>'s <span>port message
1.81 ihickson 1575: queue</span>.</li>
1.50 ihickson 1576:
1577: <li>
1.51 ihickson 1578:
1.123 ihickson 1579: <p>Let <var title="">docs</var> be the <a href="#list-of-relevant-document-objects-to-add">list of relevant
1.192 ihickson 1580: <code>Document</code> objects to add</a> given the <span title="script's global object">global object</span> of the <span title="concept-script">script</span> that invoked the
1.123 ihickson 1581: constructor.</p>
1582:
1583: </li>
1584:
1585: <li>
1586:
1587: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1588: <var title="">worker global scope</var>'s list of <span>the
1589: worker's <code>Document</code>s</span></a> the
1590: <code>Document</code> objects in <var title="">docs</var>.</p>
1591:
1592: </li>
1593:
1594: <li>
1595:
1.192 ihickson 1596: <p>If the <span title="script's global object">global object</span>
1.124 ihickson 1597: of the <span title="concept-script">script</span> that invoked the
1598: constructor is a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object (i.e. we
1599: are creating a nested worker), add <var title="">worker global
1600: scope</var> to the list of <a href="#the-worker-s-workers">the worker's workers</a> of the
1.192 ihickson 1601: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object that is the <span title="script's global object">global object</span> of the <span title="concept-script">script</span> that invoked the
1.124 ihickson 1602: constructor.</p>
1603:
1604: </li>
1605:
1606: <li>
1607:
1.115 ihickson 1608: <p><a href="#run-a-worker">Run a worker</a> for the resulting <span>absolute
1.193 ihickson 1609: URL</span>, with the <span>script's browsing context</span> of the
1.81 ihickson 1610: script that invoked the method as the <var title="">owner browsing
1.216 ihickson 1611: context</var>, with the <span>origin</span> of the <span>entry
1.176 ihickson 1612: script</span> as the <var title="">owner origin</var>, and with
1613: <var title="">worker global scope</var> as the global scope.</p>
1.9 ihickson 1614:
1.81 ihickson 1615: </li>
1.4 ihickson 1616:
1.155 ihickson 1617: </ol><p>This constructor must be visible when the <span>script's global
1.192 ihickson 1618: object</span> is either a <code>Window</code> object or an object
1.186 ihickson 1619: implementing the <code><a href="#workerutils">WorkerUtils</a></code> interface.<h4 id="shared-workers-and-the-sharedworker-interface"><span class="secno">4.7.3 </span>Shared workers and the <code><a href="#sharedworker">SharedWorker</a></code> interface</h4><pre class="idl">[<a href="#dom-sharedworker" title="dom-SharedWorker">Constructor</a>(in DOMString scriptURL, in optional DOMString name)]
1.115 ihickson 1620: interface <dfn id="sharedworker">SharedWorker</dfn> : <a href="#abstractworker">AbstractWorker</a> {
1621: readonly attribute <span>MessagePort</span> <a href="#dom-sharedworker-port" title="dom-SharedWorker-port">port</a>;
1.155 ihickson 1622: };</pre><p>The <dfn id="dom-sharedworker-port" title="dom-SharedWorker-port"><code>port</code></dfn>
1.81 ihickson 1623: attribute must return the value it was assigned by the object's
1624: constructor. It represents the <code>MessagePort</code> for
1.155 ihickson 1625: communicating with the shared worker.<p>When the <dfn id="dom-sharedworker" title="dom-SharedWorker"><code>SharedWorker(<var title="">scriptURL</var>, <var title="">name</var>)</code></dfn>
1.81 ihickson 1626: constructor is invoked, the user agent must run the following
1.155 ihickson 1627: steps:<ol><li><p><span title="resolve a url">Resolve</span> the <var title="">scriptURL</var> argument.</li>
1.81 ihickson 1628:
1629: <li><p>If this fails, throw a <code>SYNTAX_ERR</code>
1630: exception.</li>
1631:
1.159 ihickson 1632: <li><p>Otherwise, let <var title="">scriptURL</var> be the
1633: resulting <span>absolute URL</span>.</li>
1634:
1635: <li><p>Let <var title="">name</var> be the value of the second
1.164 ihickson 1636: argument, or the empty string if the second argument was
1637: omitted.</li>
1.159 ihickson 1638:
1.167 ihickson 1639: <li>
1640:
1641: <p>If the <span>origin</span> of <var title="">scriptURL</var> is
1642: not the <span title="same origin">same</span> as the origin of the
1.216 ihickson 1643: <span>entry script</span>, then throw a <code>SECURITY_ERR</code>
1.182 ihickson 1644: exception.</p>
1.167 ihickson 1645:
1646: <p class="note">Thus, scripts must be external files with the same
1647: scheme as the original page: you can't load a script from a <code title="">data:</code> URL or <code title="">javascript:</code>
1648: URL, and a <code>http:</code> page couldn't start workers using
1649: scripts with <code>http:</code> URLs.</p>
1650:
1651: </li>
1.9 ihickson 1652:
1653: <li>
1654:
1.123 ihickson 1655: <p>Let <var title="">docs</var> be the <a href="#list-of-relevant-document-objects-to-add">list of relevant
1.192 ihickson 1656: <code>Document</code> objects to add</a> given the <span title="script's global object">global object</span> of the <span title="concept-script">script</span> that invoked the
1.123 ihickson 1657: constructor.</p>
1658:
1659: </li>
1660:
1661: <li>
1662:
1.50 ihickson 1663: <p>Execute the following substeps atomically:</p>
1.9 ihickson 1664:
1.155 ihickson 1665: <ol><li><p>Create a new <code><a href="#sharedworker">SharedWorker</a></code> object, which will
1.115 ihickson 1666: shortly be associated with a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1667: object. Let this <code><a href="#sharedworker">SharedWorker</a></code> object be <var title="">worker</var>.</li>
1.81 ihickson 1668:
1.185 ihickson 1669: <li><p><span>Create a new <code>MessagePort</code> object</span>
1.192 ihickson 1670: owned by the <span title="script's global object">global
1671: object</span> of the script that invoked the method. Let this be
1.123 ihickson 1672: the <var title="">outside port</var>.</li>
1.81 ihickson 1673:
1.115 ihickson 1674: <li><p>Assign <var title="">outside port</var> to the <code title="dom-SharedWorker-port"><a href="#dom-sharedworker-port">port</a></code> attribute of <var title="">worker</var>.</li>
1.81 ihickson 1675:
1.164 ihickson 1676: <li><p>Let <var title="">worker global scope</var> be
1677: null.</li>
1678:
1679: <li><p>If <var title="">name</var> is not the empty string and
1680: there exists a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object whose
1681: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag
1682: is false, whose <code title="dom-WorkerGlobalScope-name">name</code> attribute is
1683: exactly equal to <var title="">name</var>, and whose <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1684: represents an <span>absolute URL</span> with the <span>same
1685: origin</span> as <var title="">scriptURL</var>, then let <var title="">worker global scope</var> be that
1686: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object.</li>
1687:
1688: <li><p>Otherwise, if <var title="">name</var> is the empty string
1689: and there exists a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object
1690: whose <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a>
1691: flag is false, and whose <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1692: is exactly equal to <var title="">scriptURL</var>, then let <var title="">worker global scope</var> be that
1693: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object.</li>
1694:
1.9 ihickson 1695: <li>
1696:
1.164 ihickson 1697: <p>If <var title="">worker global scope</var> is not null, then
1698: run these steps:</p>
1.81 ihickson 1699:
1.164 ihickson 1700: <ol><li><p>If <var title="">worker global scope</var>'s <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code>
1.81 ihickson 1701: attribute represents an <span>absolute URL</span> that is not
1.159 ihickson 1702: exactly equal to <var title="">scriptURL</var>, then throw a
1703: <code>URL_MISMATCH_ERR</code> exception and abort all these
1704: steps.</li>
1.81 ihickson 1705:
1706: <li><p>Associate <var title="">worker</var> with <var title="">worker global scope</var>.</li>
1707:
1.185 ihickson 1708: <li><p><span>Create a new <code>MessagePort</code>
1709: object</span> owned by <var title="">worker global
1710: scope</var>. Let this be the <var title="">inside
1711: port</var>.</li>
1.81 ihickson 1712:
1713: <li><p><span>Entangle</span> <var title="">outside port</var>
1714: and <var title="">inside port</var>.</li>
1715:
1716: <li><p>Return <var title="">worker</var> and perform the next
1717: step asynchronously.</li>
1.9 ihickson 1718:
1.81 ihickson 1719: <li><p>Create an event that uses the <code>MessageEvent</code>
1.115 ihickson 1720: interface, with the name <code title="event-connect">connect</code>, which does not bubble, is
1.118 ihickson 1721: not cancelable, has no default action, has a <code title="dom-MessageEvent-data">data</code> attribute whose value
1722: is the empty string and has a <code title="dom-MessageEvent-ports">ports</code> attribute whose
1723: value is an array containing only the newly created port, and
1724: <span>queue a task</span> to dispatch the event at <var title="">worker global scope</var>.</li>
1.43 ihickson 1725:
1.123 ihickson 1726: <li>
1727:
1728: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1729: <var title="">worker global scope</var>'s list of <span>the
1730: worker's <code>Document</code>s</span></a> the
1731: <code>Document</code> objects in <var title="">docs</var>.</p>
1732:
1733: </li>
1734:
1.124 ihickson 1735: <li>
1736:
1.192 ihickson 1737: <p>If the <span title="script's global object">global
1738: object</span> of the <span title="concept-script">script</span>
1.124 ihickson 1739: that invoked the constructor is a
1740: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, add <var title="">worker global scope</var> to the list of <a href="#the-worker-s-workers">the
1741: worker's workers</a> of the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1.192 ihickson 1742: object that is the <span title="script's global object">global
1743: object</span> of the <span title="concept-script">script</span>
1.124 ihickson 1744: that invoked the constructor.</p>
1745:
1746: </li>
1747:
1.81 ihickson 1748: <li><p>Abort all these steps.</li>
1.9 ihickson 1749:
1.155 ihickson 1750: </ol></li>
1.9 ihickson 1751:
1.185 ihickson 1752: <li><p>Create a new <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1753: object. Let <var title="">worker global scope</var> be this new
1754: object.</li>
1.9 ihickson 1755:
1.81 ihickson 1756: <li><p>Associate <var title="">worker</var> with <var title="">worker global scope</var>.</li>
1.9 ihickson 1757:
1.115 ihickson 1758: <li><p>Set the <code title="dom-SharedWorkerGlobalScope-name"><a href="#dom-sharedworkerglobalscope-name">name</a></code> attribute of
1.81 ihickson 1759: <var title="">worker global scope</var> to <var title="">name</var>.</li>
1.9 ihickson 1760:
1.185 ihickson 1761: <li><p><span>Create a new <code>MessagePort</code> object</span>
1.81 ihickson 1762: owned by <var title="">worker global scope</var>. Let <var title="">inside port</var> be this new object.</li>
1.9 ihickson 1763:
1.81 ihickson 1764: <li><p><span>Entangle</span> <var title="">outside port</var> and
1765: <var title="">inside port</var>.</li>
1.9 ihickson 1766:
1.155 ihickson 1767: </ol></li>
1.28 ihickson 1768:
1.123 ihickson 1769: <li><p>Return <var title="">worker</var> and perform the remaining
1770: steps asynchronously.</li>
1.18 ihickson 1771:
1.81 ihickson 1772: <li><p>Create an event that uses the <code>MessageEvent</code>
1.118 ihickson 1773: interface, with the name <code title="event-connect">connect</code>, which does not bubble, is not
1.115 ihickson 1774: cancelable, has no default action, has a <code title="dom-MessageEvent-data">data</code> attribute whose value is
1.118 ihickson 1775: the empty string and has a <code title="dom-MessageEvent-ports">ports</code> attribute whose value
1776: is an array containing only the newly created port, and <span>queue
1777: a task</span> to dispatch the event at <var title="">worker global
1778: scope</var>.</li>
1.26 ihickson 1779:
1780: <li>
1.46 ihickson 1781:
1.123 ihickson 1782: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1783: <var title="">worker global scope</var>'s list of <span>the
1784: worker's <code>Document</code>s</span></a> the
1785: <code>Document</code> objects in <var title="">docs</var>.</p>
1786:
1787: </li>
1788:
1789: <li>
1790:
1.192 ihickson 1791: <p>If the <span title="script's global object">global object</span>
1.124 ihickson 1792: of the <span title="concept-script">script</span> that invoked the
1793: constructor is a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, add <var title="">worker global scope</var> to the list of <a href="#the-worker-s-workers">the
1794: worker's workers</a> of the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1.192 ihickson 1795: object that is the <span title="script's global object">global
1796: object</span> of the <span title="concept-script">script</span>
1.124 ihickson 1797: that invoked the constructor.</p>
1798:
1799: </li>
1800:
1801: <li>
1802:
1.159 ihickson 1803: <p><a href="#run-a-worker">Run a worker</a> for <var title="">scriptURL</var>,
1.193 ihickson 1804: with the <span>script's browsing context</span> of the script that
1.159 ihickson 1805: invoked the method as the <var title="">owner browsing
1.216 ihickson 1806: context</var>, with the <span>origin</span> of the <span>entry
1.176 ihickson 1807: script</span> as the <var title="">owner origin</var>, and with
1808: <var title="">worker global scope</var> as the global scope.</p>
1.26 ihickson 1809:
1.60 ihickson 1810: </li>
1.81 ihickson 1811:
1.155 ihickson 1812: </ol><p>This constructor must be visible when the <span>script's global
1.192 ihickson 1813: object</span> is either a <code>Window</code> object or an object
1.155 ihickson 1814: implementing the <code><a href="#workerutils">WorkerUtils</a></code> interface.<p>The <span>task source</span> for the tasks mentioned above is the
1815: <span>DOM manipulation task source</span>.<h2 id="apis-available-to-workers"><span class="secno">5 </span>APIs available to workers</h2><pre class="idl">[Supplemental, NoInterfaceObject]
1.150 ihickson 1816: interface <dfn id="workerutils">WorkerUtils</dfn> {
1817: void <a href="#dom-workerglobalscope-importscripts" title="dom-WorkerGlobalScope-importScripts">importScripts</a>(in DOMString... urls);
1.210 ihickson 1818: readonly attribute <a href="#workernavigator">WorkerNavigator</a> <a href="#dom-worker-navigator" title="dom-worker-navigator">navigator</a>;
1.150 ihickson 1819: };
1.184 ihickson 1820: <a href="#workerutils">WorkerUtils</a> implements <span>WindowTimers</span>;</pre><p>The DOM APIs (<code>Node</code> objects, <code>Document</code>
1.81 ihickson 1821: objects, etc) are not available to workers in this version of this
1.155 ihickson 1822: specification.<h3 id="importing-scripts-and-libraries"><span class="secno">5.1 </span>Importing scripts and libraries</h3><p>When a script invokes the <dfn id="dom-workerglobalscope-importscripts" title="dom-WorkerGlobalScope-importScripts"><code>importScripts(<var title="">urls</var>)</code></dfn> method on a
1.115 ihickson 1823: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, the user agent must run the
1.155 ihickson 1824: following steps:<ol><li><p>If there are no arguments, return without doing
1.81 ihickson 1825: anything. Abort these steps.</li>
1826:
1827: <li><p><span title="resolve a url">Resolve</span> each
1828: argument.</li>
1829:
1830: <li><p>If any fail, throw a <code>SYNTAX_ERR</code>
1831: exception.</li>
1832:
1833: <!--
1.67 ihickson 1834: <li><p>If any of the resulting <span title="absolute URL">absolute
1835: URLs</span> have an <span>origin</span> that is not the <span
1836: title="same origin">same</span> as the origin of the script that
1.182 ihickson 1837: invoked the method, then throw a <code>SECURITY_ERR</code>
1838: exception.</p></li>
1.67 ihickson 1839: -->
1.26 ihickson 1840:
1841: <li>
1.81 ihickson 1842:
1.45 ihickson 1843: <p>Attempt to <span>fetch</span> each resource identified by the
1.194 ihickson 1844: resulting <span title="absolute URL">absolute URLs</span>, from
1.216 ihickson 1845: the <span>entry script</span>'s <span>origin</span>.</p> <!-- not
1.176 ihickson 1846: http-origin privacy sensitive -->
1.81 ihickson 1847:
1848: </li>
1.26 ihickson 1849:
1850: <li>
1851:
1.81 ihickson 1852: <p>For each argument in turn, in the order given, starting with
1853: the first one, run these substeps:</p>
1.26 ihickson 1854:
1.155 ihickson 1855: <ol><li>
1.26 ihickson 1856:
1.81 ihickson 1857: <p>Wait for the fetching attempt for the corresponding resource
1858: to complete.</p>
1.60 ihickson 1859:
1.81 ihickson 1860: <p>If the fetching attempt failed, throw a
1861: <code>NETWORK_ERR</code> exception and abort all these
1862: steps.</p>
1.45 ihickson 1863:
1.186 ihickson 1864: <p>If the attempt succeeds, then convert the script resource to
1865: Unicode by assuming it was encoded as UTF-8, to obtain its <var title="">source</var>.</p>
1.85 ihickson 1866:
1867: <p>Let <var title="">language</var> be JavaScript.</p>
1.61 ihickson 1868:
1.115 ihickson 1869: <p class="note">As with the worker's script, the script here is
1.81 ihickson 1870: always assumed to be JavaScript, regardless of the MIME
1.170 ihickson 1871: type.</p>
1.61 ihickson 1872:
1.81 ihickson 1873: </li>
1.26 ihickson 1874:
1.81 ihickson 1875: <li>
1.26 ihickson 1876:
1.81 ihickson 1877: <p><span>Create a script</span>, using <var title="">source</var> as the script source and <var title="">language</var> as the scripting language, using the
1.189 ihickson 1878: same global object, browsing context, URL character encoding,
1879: base URL, and script group as the <span title="concept-script">script</span> that was created by the
1.115 ihickson 1880: worker's <a href="#run-a-worker">run a worker</a> algorithm.</p>
1.81 ihickson 1881:
1.115 ihickson 1882: <p>Let the newly created <span title="concept-script">script</span> run until it either
1.81 ihickson 1883: returns, fails to parse, fails to catch an exception, or gets
1.115 ihickson 1884: prematurely aborted by the "<a href="#kill-a-worker">kill a worker</a>" or
1885: "<a href="#terminate-a-worker">terminate a worker</a>" algorithms defined above.</p>
1.26 ihickson 1886:
1.199 ihickson 1887: <p>If it failed to parse, then throw an ECMAScript
1888: <code>SyntaxError</code> exception and abort all these
1889: steps. <a href="#refsECMA262">[ECMA262]</a></p>
1.63 ihickson 1890:
1.81 ihickson 1891: <p>If an exception was raised or if the script was prematurely
1892: aborted, then abort all these steps, letting the exception or
1893: aborting continue to be processed by the script that called the
1.115 ihickson 1894: <code title="dom-WorkerGlobalScope-importScripts"><a href="#dom-workerglobalscope-importscripts">importScripts()</a></code>
1.81 ihickson 1895: method.</p>
1896:
1.115 ihickson 1897: <p>If the "<a href="#kill-a-worker">kill a worker</a>" or "<a href="#terminate-a-worker">terminate a
1.81 ihickson 1898: worker</a>" algorithms abort the script then abort all these
1899: steps.</p>
1900:
1901: </li>
1902:
1.155 ihickson 1903: </ol></li>
1.152 ihickson 1904:
1.210 ihickson 1905: </ol><h3 id="the-workernavigator-object"><span class="secno">5.2 </span>The <code><a href="#workernavigator">WorkerNavigator</a></code> object</h3><p>The <dfn id="dom-worker-navigator" title="dom-worker-navigator"><code>navigator</code></dfn> attribute
1.115 ihickson 1906: of the <code><a href="#workerutils">WorkerUtils</a></code> interface must return an instance of
1.210 ihickson 1907: the <code><a href="#workernavigator">WorkerNavigator</a></code> interface, which represents the
1908: identity and state of the user agent (the client):<pre class="idl">interface <dfn id="workernavigator">WorkerNavigator</dfn> {};
1909: <a href="#workernavigator">WorkerNavigator</a> implements <span>NavigatorID</span>;
1910: <a href="#workernavigator">WorkerNavigator</a> implements <span>NavigatorOnLine</span>;</pre><p>Objects implementing the <code><a href="#workernavigator">WorkerNavigator</a></code> interface
1911: also implement the <code>NavigatorID</code> and
1912: <code>NavigatorOnLine</code> interfaces.
1.205 ihickson 1913:
1.226 ihickson 1914: <a href="#refsHTML">[HTML]</a>
1.205 ihickson 1915:
1.210 ihickson 1916: <p>This <code><a href="#workernavigator">WorkerNavigator</a></code> interface must not exist if the
1917: interface's <span>relevant namespace object</span> is a
1918: <code>Window</code> object. <a href="#refsWEBIDL">[WEBIDL]</a><h3 id="apis-defined-in-other-specifications"><span class="secno">5.3 </span>APIs defined in other specifications</h3><p>The <code title="dom-opendatabase">openDatabase()</code> and
1.115 ihickson 1919: <code title="dom-opendatabase-sync">openDatabaseSync()</code>
1.200 ihickson 1920: methods are defined in the Web SQL Database specification. <a href="#refsWEBSQL">[WEBSQL]</a><h3 id="interface-objects-and-constructors"><span class="secno">5.4 </span>Interface objects and constructors</h3><p>There must be no interface objects and constructors available in
1.192 ihickson 1921: the global scope of scripts whose <span>script's global
1922: object</span> is a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object except for
1.155 ihickson 1923: the following:<ul><li><p><code>XMLHttpRequest</code> and all interface objects and
1.81 ihickson 1924: constructors defined by the XMLHttpRequest specifications, except
1925: that the <span>document response entity body</span> must always be
1.160 ihickson 1926: null. The <span><code>XMLHttpRequest</code> base URL</span> is the
1927: <span>script's base URL</span>; the
1928: <span><code>XMLHttpRequest</code> origin</span> is the script's
1929: <span>origin</span>. <a href="#refsXHR">[XHR]</a></li>
1.81 ihickson 1930:
1.205 ihickson 1931: <li><p>The interface objects and constructors defined by this
1932: specification.</li>
1.119 ihickson 1933:
1.205 ihickson 1934: <li><p>Constructors defined by specifications that explicitly say
1935: that they should be visible when the <span>script's global
1936: object</span> is a <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>, a
1937: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>, or an object implementing the
1938: <code><a href="#workerutils">WorkerUtils</a></code> interface; the interfaces of any objects
1939: with such constructors; and the interfaces of any objects made
1940: accessible through APIs exposed by those constructors or made
1941: accessible through interfaces to be implemented by any objects that
1942: are themselves accessible to scripts whose <span>script's global
1943: object</span> implements the <code><a href="#workerutils">WorkerUtils</a></code>
1944: interface.</li>
1945:
1946: </ul><p class="note">These requirements do not override the requirements
1947: defined by the Web IDL specification, in particular concerning the
1948: visibility of interfaces annotated with the <code title="">[NoInterfaceObject]</code> extended attribute.<h3 id="worker-locations"><span class="secno">5.5 </span>Worker locations</h3><pre class="idl">interface <dfn id="workerlocation">WorkerLocation</dfn> {
1.115 ihickson 1949: readonly attribute DOMString <a href="#dom-workerlocation-href" title="dom-WorkerLocation-href">href</a>;
1950: readonly attribute DOMString <a href="#dom-workerlocation-protocol" title="dom-WorkerLocation-protocol">protocol</a>;
1951: readonly attribute DOMString <a href="#dom-workerlocation-host" title="dom-WorkerLocation-host">host</a>;
1952: readonly attribute DOMString <a href="#dom-workerlocation-hostname" title="dom-WorkerLocation-hostname">hostname</a>;
1953: readonly attribute DOMString <a href="#dom-workerlocation-port" title="dom-WorkerLocation-port">port</a>;
1954: readonly attribute DOMString <a href="#dom-workerlocation-pathname" title="dom-WorkerLocation-pathname">pathname</a>;
1955: readonly attribute DOMString <a href="#dom-workerlocation-search" title="dom-WorkerLocation-search">search</a>;
1956: readonly attribute DOMString <a href="#dom-workerlocation-hash" title="dom-WorkerLocation-hash">hash</a>;
1.155 ihickson 1957: };</pre><p>A <code><a href="#workerlocation">WorkerLocation</a></code> object represents an <span>absolute
1958: URL</span> set at its creation.<p>The <dfn id="dom-workerlocation-href" title="dom-WorkerLocation-href"><code>href</code></dfn>
1.81 ihickson 1959: attribute must return the <span>absolute URL</span> that the object
1.155 ihickson 1960: represents.<p>The <code><a href="#workerlocation">WorkerLocation</a></code> interface also has the complement
1.163 ihickson 1961: of <span>URL decomposition IDL attributes</span>, <dfn id="dom-workerlocation-protocol" title="dom-WorkerLocation-protocol"><code>protocol</code></dfn>,
1.115 ihickson 1962: <dfn id="dom-workerlocation-host" title="dom-WorkerLocation-host"><code>host</code></dfn>, <dfn id="dom-workerlocation-port" title="dom-WorkerLocation-port"><code>port</code></dfn>, <dfn id="dom-workerlocation-hostname" title="dom-WorkerLocation-hostname"><code>hostname</code></dfn>,
1963: <dfn id="dom-workerlocation-pathname" title="dom-WorkerLocation-pathname"><code>pathname</code></dfn>,
1964: <dfn id="dom-workerlocation-search" title="dom-WorkerLocation-search"><code>search</code></dfn>,
1965: and <dfn id="dom-workerlocation-hash" title="dom-WorkerLocation-hash"><code>hash</code></dfn>. These must
1.163 ihickson 1966: follow the rules given for URL decomposition IDL attributes, with the
1.115 ihickson 1967: <span title="concept-uda-input">input</span> being the
1.81 ihickson 1968: <span>absolute URL</span> that the object represents (same as the
1.115 ihickson 1969: <code title="dom-WorkerLocation-href"><a href="#dom-workerlocation-href">href</a></code> attribute), and
1970: the <span title="concept-uda-setter">common setter action</span>
1.205 ihickson 1971: being a no-op, since the attributes are defined to be readonly.
1972:
1.226 ihickson 1973: <a href="#refsHTML">[HTML]</a>
1.205 ihickson 1974:
1.209 ihickson 1975: <p>The <code><a href="#workerlocation">WorkerLocation</a></code> interface must not exist if the
1976: interface's <span>relevant namespace object</span> is a
1.226 ihickson 1977: <code>Window</code> object. <a href="#refsWEBIDL">[WEBIDL]</a><h2 class="no-num" id="references">References</h2><!--REFS--><p>All references are normative unless marked "Non-normative".</p><!-- Dates are only included for standards older than the Web,
1978: because the newer ones keep changing. --><dl><dt id="refsDOMCORE">[DOMCORE]</dt>
1.153 ihickson 1979: <dd><cite><a href="http://www.w3.org/TR/DOM-Level-3-Core/">Document
1980: Object Model (DOM) Level 3 Core Specification</a></cite>, A. Le
1981: Hors, P. Le Hegaret, L. Wood, G. Nicol, J. Robie, M. Champion,
1.226 ihickson 1982: S. Byrnes. W3C.</dd>
1.153 ihickson 1983: <!--
1984: <dd><cite><a href="http://simon.html5.org/specs/web-dom-core">Web
1.226 ihickson 1985: DOM Core</a></cite>, S. Pieters. W3C.</dd>
1.153 ihickson 1986: -->
1987:
1.152 ihickson 1988: <dt id="refsDOMEVENTS">[DOMEVENTS]</dt>
1989: <!--
1990: <dd><cite><a
1991: href="http://www.w3.org/TR/DOM-Level-3-Events/">Document Object
1992: Model (DOM) Level 3 Events Specification</a></cite>,
1.226 ihickson 1993: B. Höhrmann, P. Le Hegaret, T. Pixley. W3C.</dd>
1.152 ihickson 1994: -->
1995: <dd><cite><a href="http://dev.w3.org/2006/webapi/DOM-Level-3-Events/html/DOM3-Events.html">Document
1996: Object Model (DOM) Level 3 Events Specification</a></cite>,
1.226 ihickson 1997: D. Schepers. W3C.</dd>
1.152 ihickson 1998:
1999: <dt id="refsECMA262">[ECMA262]</dt>
2000: <dd><cite><a href="http://www.ecma-international.org/publications/standards/Ecma-262.htm">ECMAScript
1.226 ihickson 2001: Language Specification</a></cite>. ECMA.</dd>
1.152 ihickson 2002:
1.226 ihickson 2003: <dt id="refsHTML">[HTML]</dt>
2004: <dd><cite><a href="http://www.whatwg.org/specs/web-apps/current-work/">HTML</a></cite>,
2005: I. Hickson. WHATWG.</dd>
1.152 ihickson 2006:
1.154 ihickson 2007: <dt id="refsRFC2119">[RFC2119]</dt>
2008: <dd><cite><a href="http://www.ietf.org/rfc/rfc2119.txt">Key words for use in
1.226 ihickson 2009: RFCs to Indicate Requirement Levels</a></cite>, S. Bradner. IETF.</dd>
1.154 ihickson 2010:
1.200 ihickson 2011: <dt id="refsWEBSQL">[WEBSQL]</dt>
2012: <dd><cite><a href="http://dev.w3.org/html5/webdatabase/">Web SQL
1.226 ihickson 2013: Database</a></cite>, I. Hickson. W3C.</dd>
1.152 ihickson 2014:
1.154 ihickson 2015: <dt id="refsWEBIDL">[WEBIDL]</dt>
2016: <!--
2017: <dd><cite><a href="http://www.w3.org/TR/WebIDL/">Web
1.226 ihickson 2018: IDL</a></cite>, C. McCormack. W3C.</dd>
1.154 ihickson 2019: -->
2020: <dd><cite><a href="http://dev.w3.org/2006/webapi/WebIDL/">Web
1.226 ihickson 2021: IDL</a></cite>, C. McCormack. W3C.</dd>
1.154 ihickson 2022:
1.152 ihickson 2023: <dt id="refsXHR">[XHR]</dt>
2024: <!--
2025: <dd><cite><a href="http://www.w3.org/TR/XMLHttpRequest/">The XMLHttpRequest
1.226 ihickson 2026: Object</a></cite>, A. van Kesteren. W3C.</dd>
1.152 ihickson 2027: -->
1.160 ihickson 2028: <dd><cite><a href="http://dev.w3.org/2006/webapi/XMLHttpRequest-2/"><code>XMLHttpRequest</code></a></cite>,
1.226 ihickson 2029: A. van Kesteren. W3C.</dd>
1.152 ihickson 2030:
1.221 ihickson 2031: </dl><h2 class="no-num" id="acknowledgements">Acknowledgements</h2><!-- ACKS --><p>Thanks to
1.81 ihickson 2032:
2033: Aaron Boodman,
1.155 ihickson 2034: Алексей Проскуряков (Alexey Proskuryakov),
1.81 ihickson 2035: Anne van Kesteren,
2036: Ben Turner,
2037: Dmitry Titov,
1.96 ihickson 2038: Drew Wilson,
1.97 ihickson 2039: Jeremy Orlow,
1.81 ihickson 2040: Jonas Sicking,
2041: Justin James,
2042: Kevin Hakanson,
2043: Maciej Stachowiak,
2044: Michael Nordman,
2045: Mike Smith,
2046:
2047: and
2048:
2049: Philip Taylor
2050:
1.155 ihickson 2051: for their useful and substantial comments.<p>Huge thanks to the whole Gears team, who pioneered this
1.81 ihickson 2052: technology and whose experience has been a huge influence on this
1.155 ihickson 2053: specification.
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