Annotation of html5/workers/Overview.html, revision 1.287
1.281 ihickson 1: <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"><html lang="en-US-x-Hixie"><title>Web Workers</title><style type="text/css">
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1.82 ihickson 68:
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1.82 ihickson 76:
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1.82 ihickson 118:
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1.82 ihickson 146:
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1.225 ihickson 161: body.dfnEnabled dfn { cursor: pointer; }
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1.207 ihickson 180: #configUI { position: absolute; z-index: 20; top: 10em; right: 1em; width: 11em; font-size: small; }
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183: #configUI #updateUI, #configUI .loginUI { text-align: center; }
184: #configUI input[type=button] { display: block; margin: auto; }
1.260 ihickson 185:
1.268 ihickson 186: fieldset { margin: 1em; padding: 0.5em 1em; }
187: fieldset > legend + * { margin-top: 0; }
1.266 ihickson 188: fieldset > :last-child { margin-bottom: 0; }
1.268 ihickson 189: fieldset p { margin: 0.5em 0; }
1.266 ihickson 190:
1.271 ihickson 191: </style><link href="http://www.w3.org/StyleSheets/TR/W3C-ED" rel="stylesheet" type="text/css"><script type="text/javascript">
192: function getCookie(name) {
193: var params = location.search.substr(1).split("&");
194: for (var index = 0; index < params.length; index++) {
195: if (params[index] == name)
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204: if (data[0] == name)
205: return unescape(data[1]);
206: }
207: return null;
208: }
1.283 ihickson 209: </script><div class="head" id="head">
1.115 ihickson 210: <p><a href="http://www.w3.org/"><img alt="W3C" height="48" src="http://www.w3.org/Icons/w3c_home" width="72"></a></p>
1.271 ihickson 211:
1.54 ihickson 212: <h1>Web Workers</h1>
1.281 ihickson 213:
1.287 ! ihickson 214: <h2 class="no-num no-toc" id="editor-s-draft-1-june-2011">Editor's Draft 1 June 2011</h2>
1.218 ihickson 215: <dl><dt>Latest Published Version:</dt>
1.115 ihickson 216: <dd><a href="http://www.w3.org/TR/workers/">http://www.w3.org/TR/workers/</a></dd>
1.109 ihickson 217: <dt>Latest Editor's Draft:</dt>
1.260 ihickson 218: <dd><a class="latest-link" href="http://dev.w3.org/html5/workers/">http://dev.w3.org/html5/workers/</a></dd>
1.284 ihickson 219:
1.2 ihickson 220: <dt>Previous Versions:</dt>
1.279 ihickson 221: <dd><a href="http://www.w3.org/TR/2011/WD-workers-20110310/">http://www.w3.org/TR/2011/WD-workers-20110310/</a></dd>
222: <dd><a href="http://www.w3.org/TR/2011/WD-workers-20110208/">http://www.w3.org/TR/2011/WD-workers-20110208/</a></dd>
1.198 ihickson 223: <dd><a href="http://www.w3.org/TR/2009/WD-workers-20091029/">http://www.w3.org/TR/2009/WD-workers-20091029/</a></dd>
1.279 ihickson 224: <dd><a href="http://www.w3.org/TR/2009/WD-workers-20090423/">http://www.w3.org/TR/2009/WD-workers-20090423/</a></dd>
1.117 ihickson 225: <!-- :ZZZ -->
1.271 ihickson 226: <dt>Editor:</dt>
1.115 ihickson 227: <dd><a href="mailto:ian@hixie.ch">Ian Hickson</a>, Google, Inc.</dd>
1.155 ihickson 228: </dl><p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a>
1.285 ihickson 229: © 2011 <a href="http://www.w3.org/"><abbr title="World Wide
1.155 ihickson 230: Web Consortium">W3C</abbr></a><sup>®</sup> (<a href="http://www.csail.mit.edu/"><abbr title="Massachusetts
1.115 ihickson 231: Institute of Technology">MIT</abbr></a>, <a href="http://www.ercim.org/"><abbr title="European Research
232: Consortium for Informatics and Mathematics">ERCIM</abbr></a>, <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C
233: <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
234: <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
235: and <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document
1.81 ihickson 236: use</a> rules apply.</p>
1.201 ihickson 237:
1.254 ihickson 238:
1.252 ihickson 239: <!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
1.255 ihickson 240: <p class="alt">The bulk of the text of this specification is also
1.254 ihickson 241: available in the WHATWG <a href="http://www.whatwg.org/specs/web-apps/current-work/complete.html#workers">Web Applications 1.0</a> specification, under a license that permits
242: reuse of the specification text.</p>
1.252 ihickson 243: <!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
244:
1.254 ihickson 245:
1.155 ihickson 246: </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 247: authors to spawn background workers running scripts in parallel to
248: their main page. This allows for thread-like operation with
1.281 ihickson 249: message-passing as the coordination mechanism.<h2 class="no-num no-toc" id="status-of-this-document">Status of This document</h2><p><em>This section describes the status of this document at the
1.81 ihickson 250: time of its publication. Other documents may supersede this
251: document. A list of current W3C publications and the most recently
252: formally published revision of this technical report can be found in
1.115 ihickson 253: the <a href="http://www.w3.org/TR/">W3C technical reports index</a>
1.281 ihickson 254: at http://www.w3.org/TR/.</em></p><p>If you wish to make comments regarding this document in a manner
1.271 ihickson 255: that is tracked by the W3C, please submit them via using <a href="http://www.w3.org/Bugs/Public/enter_bug.cgi?product=HTML%20WG">our
256: public bug database</a>. If you do not have an account then you can
257: enter feedback using this form:<form action="http://www.whatwg.org/specs/web-apps/current-work/file-spam.cgi" method="post">
258: <fieldset><legend>Feedback Comments</legend>
259: <input name="id" type="hidden" value="top"><input name="component" type="hidden" value="Web Workers (editor: Ian Hickson)"><input name="response" type="hidden" value="html"><p><label for="feedbackBox">Please enter your feedback, carefully
260: indicating the title of the section for which you are submitting
261: feedback, quoting the text that's wrong today if appropriate. If
262: you're suggesting a new feature, it's really important to say
263: <em>what</em> the problem you're trying to solve is. That's more
264: important than the solution, in fact.</label></p>
265: <p><textarea cols="79" id="feedbackBox" name="text" rows="10"></textarea></p>
266: <p class="note">Please don't use section numbers as these tend to
267: change rapidly and make your feedback harder to understand.</p>
268: <script type="text/javascript">
1.287 ! ihickson 269: function checkFeedbackForm(form) {
! 270: if (form.elements.text.value.match(/^ *</)) {
! 271: alert('Please don\'t start your feedback with an angle bracket, instead explain what topic your feedback is about first.');
! 272: return true;
! 273: } else if (form.elements.text.value.match(/ [^ ]+ [^ ]+ [^ ]+ [^ ]+ /)) {
! 274: if (form.elements.text.value.match(/^Please enter your feedback, carefully/)) {
! 275: alert('Please enter your feedback, explaining what is wrong, and without repeating the instructions. Thanks!');
! 276: return true;
! 277: } else if (form.elements.text.value.match(/ [^ ]+ [^ ]+ [^ ]+ [^ ]+ /)) {
! 278: form.action = "http://www.whatwg.org/specs/web-apps/current-work/file-bug.cgi";
! 279: return true;
! 280: } else {
! 281: alert('Please include significantly more detail about exactly what problem you are trying to solve.');
! 282: return false;
! 283: }
! 284: }
! 285: }
1.271 ihickson 286: </script><p>
1.277 ihickson 287: <input onclick="return checkFeedbackForm(form)" type="submit" value="Submit feedback"><small>(Note: Your IP address and user agent will be publicly recorded for spam prevention purposes.)</small>
1.271 ihickson 288: </p>
289: </fieldset></form><p>You can also e-mail feedback to <a href="mailto:public-webapps@w3.org">public-webapps@w3.org</a> (<a href="mailto:public-webapps-request@w3.org?subject=subscribe">subscribe</a>,
290: <a href="http://lists.w3.org/Archives/Public/public-webapps/">archives</a>),
1.115 ihickson 291: or <a href="mailto:whatwg@whatwg.org">whatwg@whatwg.org</a> (<a href="http://lists.whatwg.org/listinfo.cgi/whatwg-whatwg.org">subscribe</a>,
292: <a href="http://lists.whatwg.org/pipermail/whatwg-whatwg.org/">archives</a>).
1.281 ihickson 293: All feedback is welcome.</p><p>Implementors should be aware that this specification is not
1.81 ihickson 294: stable. <strong>Implementors who are not taking part in the
295: discussions are likely to find the specification changing out from
296: under them in incompatible ways.</strong> Vendors interested in
297: implementing this specification before it eventually reaches the
298: Candidate Recommendation stage should join the aforementioned
1.271 ihickson 299: mailing lists and take part in the discussions.<div id="multipage-common">
1.281 ihickson 300: </div><p>The latest
1.271 ihickson 301: stable version of the editor's draft of this specification is always
302: available on <a href="http://dev.w3.org/html5/workers/">the W3C CVS server</a>
303: and in the <a href="http://svn.whatwg.org/webapps/">WHATWG
304: Subversion repository</a>. The <a href="http://www.whatwg.org/specs/web-apps/current-work/complete.html">latest
305: editor's working copy</a> (which may contain unfinished text in the
306: process of being prepared) contains the latest draft text of this
307: specification (amongst others). For more details, please see the <a href="http://wiki.whatwg.org/wiki/FAQ#What_are_the_various_versions_of_the_spec.3F">WHATWG
308: FAQ</a>.<p>Notifications of changes to this specification are sent along
309: with notifications of changes to related specifications using the
310: following mechanisms:<dl><dt>E-mail notifications of changes</dt>
311: <dd>Commit-Watchers mailing list (complete source diffs): <a href="http://lists.whatwg.org/listinfo.cgi/commit-watchers-whatwg.org">http://lists.whatwg.org/listinfo.cgi/commit-watchers-whatwg.org</a></dd>
312: <dt>Browsable version-control record of all changes:</dt>
313: <dd>CVSWeb interface with side-by-side diffs: <a href="http://dev.w3.org/cvsweb/html5/">http://dev.w3.org/cvsweb/html5/</a></dd>
314: <dd>Annotated summary with unified diffs: <a href="http://html5.org/tools/web-apps-tracker">http://html5.org/tools/web-apps-tracker</a></dd>
315: <dd>Raw Subversion interface: <code>svn checkout http://svn.whatwg.org/webapps/</code></dd>
316: </dl><p>The W3C <a href="http://www.w3.org/2008/webapps/">Web Applications
1.81 ihickson 317: Working Group</a> is the W3C working group responsible for this
318: specification's progress along the W3C Recommendation track.
1.287 ! ihickson 319: This specification is the 1 June 2011 Editor's Draft.
1.281 ihickson 320: </p><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 321: 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 322: any patent disclosures</a> made in connection with the deliverables
323: of the group; that page also includes instructions for disclosing a
324: patent. An individual who has actual knowledge of a patent which the
1.115 ihickson 325: individual believes contains <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential
326: Claim(s)</a> must disclose the information in accordance with <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section
1.252 ihickson 327: 6 of the W3C Patent Policy</a>.<h2 class="no-num no-toc" id="contents">Table of Contents</h2>
1.115 ihickson 328: <ol class="toc">
329: <li><a href="#introduction"><span class="secno">1 </span>Introduction</a>
1.81 ihickson 330: <ol>
1.115 ihickson 331: <li><a href="#scope"><span class="secno">1.1 </span>Scope</a></li>
332: <li><a href="#tutorial"><span class="secno">1.2 </span>Tutorial</a>
1.81 ihickson 333: <ol>
1.115 ihickson 334: <li><a href="#a-background-number-crunching-worker"><span class="secno">1.2.1 </span>A background number-crunching worker</a></li>
335: <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>
336: <li><a href="#worker-used-for-background-i-o"><span class="secno">1.2.3 </span>Worker used for background I/O</a></li>
1.238 ihickson 337: <li><a href="#shared-workers-introduction"><span class="secno">1.2.4 </span>Shared workers introduction</a></li>
338: <li><a href="#shared-state-using-a-shared-worker"><span class="secno">1.2.5 </span>Shared state using a shared worker</a></li>
1.275 ihickson 339: <li><a href="#delegation"><span class="secno">1.2.6 </span>Delegation</a></ol></ol></li>
1.148 ihickson 340: <li><a href="#conformance-requirements"><span class="secno">2 </span>Conformance requirements</a>
1.82 ihickson 341: <ol>
1.148 ihickson 342: <li><a href="#dependencies"><span class="secno">2.1 </span>Dependencies</a></ol></li>
343: <li><a href="#terminology"><span class="secno">3 </span>Terminology</a></li>
344: <li><a href="#infrastructure"><span class="secno">4 </span>Infrastructure</a>
345: <ol>
346: <li><a href="#the-global-scope"><span class="secno">4.1 </span>The global scope</a>
1.81 ihickson 347: <ol>
1.148 ihickson 348: <li><a href="#the-workerglobalscope-abstract-interface"><span class="secno">4.1.1 </span>The <code>WorkerGlobalScope</code> abstract interface</a></li>
349: <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>
1.270 ihickson 350: <li><a href="#shared-workers-and-the-sharedworkerglobalscope-interface"><span class="secno">4.1.3 </span>Shared workers and the <code>SharedWorkerGlobalScope</code> interface</a></ol></li>
1.160 ihickson 351: <li><a href="#origins-of-workers"><span class="secno">4.2 </span>Origins of workers</a></li>
1.186 ihickson 352: <li><a href="#the-event-loop"><span class="secno">4.3 </span>The event loop</a></li>
353: <li><a href="#the-worker-s-lifetime"><span class="secno">4.4 </span>The worker's lifetime</a></li>
354: <li><a href="#processing-model"><span class="secno">4.5 </span>Processing model</a></li>
355: <li><a href="#runtime-script-errors"><span class="secno">4.6 </span>Runtime script errors</a></li>
356: <li><a href="#creating-workers"><span class="secno">4.7 </span>Creating workers</a>
1.81 ihickson 357: <ol>
1.186 ihickson 358: <li><a href="#the-abstractworker-abstract-interface"><span class="secno">4.7.1 </span>The <code>AbstractWorker</code> abstract interface</a></li>
359: <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>
360: <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 361: <li><a href="#apis-available-to-workers"><span class="secno">5 </span>APIs available to workers</a>
1.81 ihickson 362: <ol>
1.148 ihickson 363: <li><a href="#importing-scripts-and-libraries"><span class="secno">5.1 </span>Importing scripts and libraries</a></li>
1.210 ihickson 364: <li><a href="#the-workernavigator-object"><span class="secno">5.2 </span>The <code>WorkerNavigator</code> object</a></li>
1.272 ihickson 365: <li><a href="#interface-objects-and-constructors"><span class="secno">5.3 </span>Interface objects and constructors</a></li>
366: <li><a href="#worker-locations"><span class="secno">5.4 </span>Worker locations</a></ol></li>
1.115 ihickson 367: <li><a class="no-num" href="#references">References</a></li>
368: <li><a class="no-num" href="#acknowledgements">Acknowledgements</a></ol>
1.281 ihickson 369: <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
1.155 ihickson 370: background independently of any user interface scripts.<p>This allows for long-running scripts that are not interrupted by
1.81 ihickson 371: scripts that respond to clicks or other user interactions, and
372: allows long tasks to be executed without yielding to keep the page
1.155 ihickson 373: responsive.<p>Workers (as these background scripts are called herein) are
1.81 ihickson 374: relatively heavy-weight, and are not intended to be used in large
375: numbers. For example, it would be inappropriate to launch one worker
376: for each pixel of a four megapixel image. The examples below show
1.155 ihickson 377: some appropriate uses of workers.<p>Generally, workers are expected to be long-lived, have a high
378: 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
379: 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
380: expensive task without interrupting the user interface.<p>In this example, the main document spawns a worker to
381: (naïvely) compute prime numbers, and progressively displays the
382: most recently found prime number.<p>The main page is as follows:<pre><!DOCTYPE HTML>
1.81 ihickson 383: <html>
384: <head>
385: <title>Worker example: One-core computation</title>
386: </head>
387: <body>
388: <p>The highest prime number discovered so far is: <output id="result"></output></p>
389: <script>
1.50 ihickson 390: var worker = new Worker('worker.js');
391: worker.onmessage = function (event) {
1.54 ihickson 392: document.getElementById('result').textContent = event.data;
1.29 ihickson 393: };
1.81 ihickson 394: </script>
395: </body>
1.155 ihickson 396: </html></pre><p>The <code title="dom-Worker"><a href="#dom-worker">Worker()</a></code> constructor call
1.115 ihickson 397: creates a worker and returns a <code><a href="#worker">Worker</a></code> object
1.81 ihickson 398: representing that worker, which is used to communicate with the
1.177 ihickson 399: 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 400: search: while (true) {
401: n += 1;
402: for (var i = 2; i <= Math.sqrt(n); i += 1)
403: if (n % i == 0)
404: continue search;
405: // found a prime!
1.50 ihickson 406: postMessage(n);
1.155 ihickson 407: }</pre><p>The bulk of this code is simply an unoptimized search for a prime
1.278 ihickson 408: number. To send a message back to the page, the <code title="dom-DedicatedWorkerGlobalScope-send">send()</code>
1.155 ihickson 409: 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 410: task is to listen for notifications from the server, and, when
411: appropriate, either add or remove data from the client-side
1.155 ihickson 412: database.<p>Since no communication occurs between the worker and the main
413: page, the main page can start the worker by just doing:<pre><script>
1.50 ihickson 414: new Worker('worker.js');
1.155 ihickson 415: </script></pre><p>The worker itself is as follows:<pre>var server = new WebSocket('ws://whatwg.org/database');
1.42 ihickson 416: var database = openDatabase('demobase', '1.0', 'Demo Database', 10240);
1.31 ihickson 417: server.onmessage = function (event) {
418: // data is in the format "command key value"
1.54 ihickson 419: var data = event.data.split(' ');
1.31 ihickson 420: switch (data[0]) {
421: case '+':
422: database.transaction(function(tx) {
423: tx.executeSql('INSERT INTO pairs (key, value) VALUES (?, ?)', data[1], data[2]);
424: });
425: case '-':
426: database.transaction(function(tx) {
427: tx.executeSql('DELETE FROM pairs WHERE key=? AND value=?', data[1], data[2]);
428: });
429: }
1.155 ihickson 430: };</pre><p>This connects to the server using the <code>WebSocket</code>
1.81 ihickson 431: mechanism and opens the local database (which, we presume, has been
432: created earlier). The worker then just listens for messages from the
433: server and acts on them as appropriate, forever (or until the main
1.155 ihickson 434: page is closed).<p><a href="http://www.whatwg.org/demos/workers/database-updater/page.html">View
1.81 ihickson 435: this example online</a>. (This example will not actually function,
436: since the server does not actually exist and the database is not
1.155 ihickson 437: 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 438: fetching stock updates for at regular intervals, and one for
1.155 ihickson 439: fetching performing search queries that the user requests.<p>The main page is as follows:<pre><!DOCTYPE HTML>
1.81 ihickson 440: <html>
441: <head>
442: <title>Worker example: Stock ticker</title>
443: <script>
1.33 ihickson 444: // TICKER
445: var symbol = 'GOOG'; // default symbol to watch
1.50 ihickson 446: var ticker = new Worker('ticker.js');
1.33 ihickson 447:
448: // SEARCHER
1.50 ihickson 449: var searcher = new Worker('searcher.js');
1.33 ihickson 450: function search(query) {
1.50 ihickson 451: searcher.postMessage(query);
1.33 ihickson 452: }
453:
454: // SYMBOL SELECTION UI
455: function select(newSymbol) {
456: symbol = newSymbol;
1.50 ihickson 457: ticker.postMessage(symbol);
1.33 ihickson 458: }
1.81 ihickson 459: </script>
460: </head>
1.122 ihickson 461: <body onload="search('')">
1.81 ihickson 462: <p><output id="symbol"></output> <output id="value"></output></p>
463: <script>
1.50 ihickson 464: ticker.onmessage = function (event) {
1.54 ihickson 465: var data = event.data.split(' ');
1.33 ihickson 466: document.getElementById('symbol').textContent = data[0];
467: document.getElementById('value').textContent = data[1];
468: };
1.50 ihickson 469: ticker.postMessage(symbol);
1.81 ihickson 470: </script>
1.122 ihickson 471: <p><label>Search: <input type="text" autofocus oninput="search(this.value)"></label></p>
1.81 ihickson 472: <ul id="results"></ul>
473: <script>
1.50 ihickson 474: searcher.onmessage = function (event) {
1.54 ihickson 475: var data = event.data.split(' ');
1.33 ihickson 476: var results = document.getElementById('results');
477: while (results.hasChildNodes()) // clear previous results
478: results.removeChild(results.firstChild);
479: for (var i = 0; i < data.length; i += 1) {
480: // add a list item with a button for each result
481: var li = document.createElement('li');
482: var button = document.createElement('button');
483: button.value = data[i];
484: button.type = 'button';
485: button.onclick = function () { select(this.value); };
486: button.textContent = data[i];
487: li.appendChild(button);
488: results.appendChild(li);
489: }
490: };
1.81 ihickson 491: </script>
492: <p>(The data in this example is not real. Try searching for "Google" or "Apple".)</p>
493: </body>
1.155 ihickson 494: </html></pre><p>The two workers use a common library for performing the actual
495: network calls. This library is as follows:<pre>function get(url) {
1.50 ihickson 496: try {
497: var xhr = new XMLHttpRequest();
498: xhr.open('GET', url, false);
499: xhr.send();
500: return xhr.responseText;
501: } catch (e) {
502: return ''; // turn all errors into empty results
503: }
1.155 ihickson 504: }</pre><p>The stock updater worker is as follows:<pre>importScripts('io.js');
1.33 ihickson 505: var timer;
506: var symbol;
507: function update() {
1.50 ihickson 508: postMessage(symbol + ' ' + get('stock.cgi?' + symbol));
1.33 ihickson 509: timer = setTimeout(update, 10000);
510: }
1.50 ihickson 511: onmessage = function (event) {
1.33 ihickson 512: if (timer)
513: clearTimeout(timer);
1.54 ihickson 514: symbol = event.data;
1.33 ihickson 515: update();
1.155 ihickson 516: };</pre><p>The search query worker is as follows:<pre>importScripts('io.js');
1.50 ihickson 517: onmessage = function (event) {
1.54 ihickson 518: postMessage(get('search.cgi?' + event.data));
1.238 ihickson 519: };</pre><p><a href="http://www.whatwg.org/demos/workers/stocks/page.html">View this example online</a>.<h4 id="shared-workers-introduction"><span class="secno">1.2.4 </span>Shared workers introduction</h4><p><i>This section is non-normative.</i><p>This section introduces shared workers using a Hello World
520: example. Shared workers use slightly different APIs, since each
521: worker can have multiple connections.<p>This first example shows how you connect to a worker and how a
522: worker can send a message back to the page when it connects to
1.239 ihickson 523: it. Received messages are displayed in a log.<p>Here is the HTML page:<pre><!DOCTYPE HTML>
524: <title>Shared workers: demo 1</title>
525: <pre id="log">Log:</pre>
526: <script>
527: var worker = new SharedWorker('test.js');
528: var log = document.getElementById('log');
529: worker.port.onmessage = function(e) { // note: not worker.onmessage!
530: log.textContent += '\n' + e.data;
531: }
532: </script>
533: </pre><p>Here is the JavaScript worker:<pre>onconnect = function(e) {
534: var port = e.ports[0];
535: port.postMessage('Hello World!');
536: }
1.259 ihickson 537: </pre><p><a href="http://www.whatwg.org/demos/workers/shared/001/test.html">View this example online</a>.<hr><p>This second example extends the first one by changing two things:
1.238 ihickson 538: first, messages are received using <code title="">addEventListener()</code> instead of an <span title="event
539: handler IDL attributes">event handler IDL attribute</span>, and
540: second, a message is sent <em>to</em> the worker, causing the worker
541: to send another message in return. Received messages are again
1.239 ihickson 542: displayed in a log.<p>Here is the HTML page:<pre><!DOCTYPE HTML>
1.240 ihickson 543: <title>Shared workers: demo 2</title>
1.239 ihickson 544: <pre id="log">Log:</pre>
545: <script>
546: var worker = new SharedWorker('test.js');
547: var log = document.getElementById('log');
1.240 ihickson 548: worker.port.addEventListener('message', function(e) {
1.239 ihickson 549: log.textContent += '\n' + e.data;
1.240 ihickson 550: }, false);
551: worker.port.start(); // note: need this when using addEventListener
552: worker.port.postMessage('ping');
1.239 ihickson 553: </script>
554: </pre><p>Here is the JavaScript worker:<pre>onconnect = function(e) {
555: var port = e.ports[0];
556: port.postMessage('Hello World!');
1.240 ihickson 557: port.onmessage = function(e) {
558: port.postMessage('pong'); // not e.ports[0].postMessage!
559: // e.target.postMessage('pong'); would work also
560: }
1.239 ihickson 561: }
1.259 ihickson 562: </pre><p><a href="http://www.whatwg.org/demos/workers/shared/002/test.html">View this example online</a>.<hr><p>Finally, the example is extended to show how two pages can
1.238 ihickson 563: connect to the same worker; in this case, the second page is merely
564: in an <code>iframe</code> on the first page, but the same principle
565: would apply to an entirely separate page in a separate
1.239 ihickson 566: <span>top-level browsing context</span>.<p>Here is the outer HTML page:<pre><!DOCTYPE HTML>
567: <title>Shared workers: demo 3</title>
568: <pre id="log">Log:</pre>
569: <script>
570: var worker = new SharedWorker('test.js');
571: var log = document.getElementById('log');
572: worker.port.addEventListener('message', function(e) {
573: log.textContent += '\n' + e.data;
574: }, false);
575: worker.port.start();
576: worker.port.postMessage('ping');
577: </script>
578: <iframe src="inner.html"></iframe>
579: </pre><p>Here is the inner HTML page:<pre><!DOCTYPE HTML>
580: <title>Shared workers: demo 3 inner frame</title>
581: <pre id=log>Inner log:</pre>
582: <script>
583: var worker = new SharedWorker('test.js');
584: var log = document.getElementById('log');
585: worker.port.onmessage = function(e) {
586: log.textContent += '\n' + e.data;
587: }
588: </script>
589: </pre><p>Here is the JavaScript worker:<pre>var count = 0;
590: onconnect = function(e) {
591: count += 1;
592: var port = e.ports[0];
593: port.postMessage('Hello World! You are connection #' + count);
594: port.onmessage = function(e) {
595: port.postMessage('pong');
596: }
597: }
1.259 ihickson 598: </pre><p><a href="http://www.whatwg.org/demos/workers/shared/003/test.html">View this example online</a>.<h4 id="shared-state-using-a-shared-worker"><span class="secno">1.2.5 </span>Shared state using a shared worker</h4><p><i>This section is non-normative.</i><p>In this example, multiple windows (viewers) can be opened that
1.81 ihickson 599: are all viewing the same map. All the windows share the same map
600: information, with a single worker coordinating all the viewers. Each
601: viewer can move around independently, but if they set any data on
1.155 ihickson 602: the map, all the viewers are updated.<p>The main page isn't interesting, it merely provides a way to open
603: the viewers:<pre><!DOCTYPE HTML>
1.81 ihickson 604: <html>
605: <head>
606: <title>Workers example: Multiviewer</title>
607: <script>
1.36 ihickson 608: function openViewer() {
609: window.open('viewer.html');
610: }
1.81 ihickson 611: </script>
612: </head>
613: <body>
614: <p><button type=button onclick="openViewer()">Open a new
615: viewer</button></p>
616: <p>Each viewer opens in a new window. You can have as many viewers
617: as you like, they all view the same data.</p>
618: </body>
1.155 ihickson 619: </html></pre><p>The viewer is more involved:<pre><!DOCTYPE HTML>
1.81 ihickson 620: <html>
621: <head>
622: <title>Workers example: Multiviewer viewer</title>
623: <script>
1.50 ihickson 624: var worker = new SharedWorker('worker.js', 'core');
1.36 ihickson 625:
626: // CONFIGURATION
627: function configure(event) {
1.54 ihickson 628: if (event.data.substr(0, 4) != 'cfg ') return;
629: var name = event.data.substr(4).split(' ', 1);
1.36 ihickson 630: // update display to mention our name is name
631: document.getElementsByTagName('h1')[0].textContent += ' ' + name;
632: // no longer need this listener
1.43 ihickson 633: worker.port.removeEventListener('message', configure, false);
1.36 ihickson 634: }
1.53 ihickson 635: worker.port.addEventListener('message', configure, false);
1.36 ihickson 636:
637: // MAP
638: function paintMap(event) {
1.54 ihickson 639: if (event.data.substr(0, 4) != 'map ') return;
640: var data = event.data.substr(4).split(',');
1.36 ihickson 641: // display tiles data[0] .. data[8]
642: var canvas = document.getElementById('map');
643: var context = canvas.getContext('2d');
644: for (var y = 0; y < 3; y += 1) {
645: for (var x = 0; x < 3; x += 1) {
646: var tile = data[y * 3 + x];
647: if (tile == '0')
648: context.fillStyle = 'green';
649: else
650: context.fillStyle = 'maroon';
651: fillRect(x * 50, y * 50, 50, 50);
652: }
653: }
654: }
1.53 ihickson 655: worker.port.addEventListener('message', paintMap, false);
1.36 ihickson 656:
657: // PUBLIC CHAT
658: function updatePublicChat(event) {
1.54 ihickson 659: if (event.data.substr(0, 4) != 'txt ') return;
660: var name = event.data.substr(4).split(' ', 1);
661: var message = event.data.substr(4 + length(name) + 1);
1.81 ihickson 662: // display "<name> message" in public chat
1.36 ihickson 663: var dialog = document.getElementById('public');
664: var dt = document.createElement('dt');
665: dt.textContent = name;
666: dialog.appendChild(dt);
667: var dd = document.createElement('dd');
668: dd.textContent = message;
669: dialog.appendChild(dd);
670: }
1.53 ihickson 671: worker.port.addEventListener('message', updatePublicChat, false);
1.36 ihickson 672:
673: // PRIVATE CHAT
674: function startPrivateChat(event) {
1.54 ihickson 675: if (event.data.substr(0, 4) != 'msg ') return;
676: var name = event.data.substr(4).split(' ', 1);
1.84 ihickson 677: var port = event.ports[0];
1.36 ihickson 678: // display a private chat UI
679: var ul = document.getElementById('private');
680: var li = document.createElement('li');
681: var h3 = document.createElement('h3');
682: h3.textContent = 'Private chat with ' + name;
683: li.appendChild(h3);
684: var dialog = document.createElement('dialog');
685: var addMessage = function(name, message) {
686: var dt = document.createElement('dt');
687: dt.textContent = name;
688: dialog.appendChild(dt);
689: var dd = document.createElement('dd');
690: dd.textContent = message;
691: dialog.appendChild(dd);
692: };
693: port.onmessage = function (event) {
1.54 ihickson 694: addMessage(name, event.data);
1.36 ihickson 695: };
696: li.appendChild(dialog);
697: var form = document.createElement('form');
698: var p = document.createElement('p');
699: var input = document.createElement('input');
700: input.size = 50;
701: p.appendChild(input);
702: p.appendChild(document.createTextNode(' '));
703: var button = document.createElement('button');
704: button.textContent = 'Post';
705: p.appendChild(button);
706: form.onsubmit = function () {
707: port.postMessage(input.value);
708: addMessage('me', input.value);
709: input.value = '';
710: return false;
711: };
712: form.appendChild(p);
713: li.appendChild(form);
714: }
1.53 ihickson 715: worker.port.addEventListener('message', startPrivateChat, false);
1.188 ihickson 716:
717: worker.port.start();
1.81 ihickson 718: </script>
719: </head>
720: <body>
721: <h1>Viewer</h1>
722: <h2>Map</h2>
723: <p><canvas id="map" height=150 width=150></canvas></p>
724: <p>
725: <button type=button onclick="worker.port.postMessage('mov left')">Left</button>
726: <button type=button onclick="worker.port.postMessage('mov up')">Up</button>
727: <button type=button onclick="worker.port.postMessage('mov down')">Down</button>
728: <button type=button onclick="worker.port.postMessage('mov right')">Right</button>
729: <button type=button onclick="worker.port.postMessage('set 0')">Set 0</button>
730: <button type=button onclick="worker.port.postMessage('set 1')">Set 1</button>
731: </p>
732: <h2>Public Chat</h2>
733: <dialog id="public"></dialog>
734: <form onsubmit="worker.port.postMessage('txt ' + message.value); message.value = ''; return false;">
735: <p>
736: <input type="text" name="message" size="50">
737: <button>Post</button>
738: </p>
739: </form>
740: <h2>Private Chat</h2>
741: <ul id="private"></ul>
742: </body>
743: </html>
1.155 ihickson 744: </pre><p>There are several key things worth noting about the way the
745: viewer is written.<p><strong>Multiple listeners</strong>. Instead of a single message
1.81 ihickson 746: processing function, the code here attaches multiple event
747: listeners, each one performing a quick check to see if it is
748: relevant for the message. In this example it doesn't make much
749: difference, but if multiple authors wanted to collaborate using a
750: single port to communicate with a worker, it would allow for
751: independent code instead of changes having to all be made to a
1.155 ihickson 752: single event handling function.<p>Registering event listeners in this way also allows you to
1.81 ihickson 753: unregister specific listeners when you are done with them, as is
754: done with the <code title="">configure()</code> method in this
1.155 ihickson 755: example.<p>Finally, the worker:<pre>
756: var nextName = 0;
1.36 ihickson 757: function getNextName() {
758: // this could use more friendly names
759: // but for now just return a number
760: return nextName++;
761: }
762:
763: var map = [
764: [0, 0, 0, 0, 0, 0, 0],
765: [1, 1, 0, 1, 0, 1, 1],
766: [0, 1, 0, 1, 0, 0, 0],
767: [0, 1, 0, 1, 0, 1, 1],
768: [0, 0, 0, 1, 0, 0, 0],
769: [1, 0, 0, 1, 1, 1, 1],
770: [1, 1, 0, 1, 1, 0, 1],
771: ];
772:
773: function wrapX(x) {
774: if (x < 0) return wrapX(x + map[0].length);
1.81 ihickson 775: if (x >= map[0].length) return wrapX(x - map[0].length);
1.36 ihickson 776: return x;
777: }
778:
779: function wrapY(y) {
780: if (y < 0) return wrapY(y + map.length);
1.81 ihickson 781: if (y >= map[0].length) return wrapY(y - map.length);
1.36 ihickson 782: return y;
783: }
784:
1.50 ihickson 785: function sendMapData(callback) {
1.36 ihickson 786: var data = '';
787: for (var y = viewer.y-1; y <= viewer.y+1; y += 1) {
788: for (var x = viewer.x-1; x <= viewer.x+1; x += 1) {
789: if (data != '')
790: data += ',';
791: data += map[y][x];
792: }
793: }
1.50 ihickson 794: callback('map ' + data);
1.36 ihickson 795: }
796:
797: var viewers = {};
798: onconnect = function (event) {
1.84 ihickson 799: event.ports[0]._name = getNextName();
800: event.ports[0]._data = { port: event.port, x: 0, y: 0, };
801: viewers[event.ports[0]._name] = event.port._data;
802: event.ports[0].postMessage('cfg ' + name);
803: event.ports[0].onmessage = getMessage;
804: sendMapData(event.ports[0].postMessage);
1.36 ihickson 805: };
806:
807: function getMessage(event) {
1.54 ihickson 808: switch (event.data.substr(0, 4)) {
1.36 ihickson 809: case 'mov ':
1.54 ihickson 810: var direction = event.data.substr(4);
1.36 ihickson 811: var dx = 0;
812: var dy = 0;
813: switch (direction) {
814: case 'up': dy = -1; break;
815: case 'down': dy = 1; break;
816: case 'left': dx = -1; break;
817: case 'right': dx = 1; break;
818: }
819: event.target._data.x = wrapX(event.target._data.x + dx);
820: event.target._data.y = wrapY(event.target._data.y + dy);
1.50 ihickson 821: sendMapData(event.target.postMessage);
1.36 ihickson 822: break;
823: case 'set ':
1.54 ihickson 824: var value = event.data.substr(4);
1.36 ihickson 825: map[event.target._data.y][event.target._data.x] = value;
826: for (var viewer in viewers)
1.50 ihickson 827: sendMapData(viewers[viewer].port.postMessage);
1.36 ihickson 828: break;
829: case 'txt ':
830: var name = event.target._name;
1.54 ihickson 831: var message = event.data.substr(4);
1.36 ihickson 832: for (var viewer in viewers)
833: viewers[viewer].port.postMessage('txt ' + name + ' ' + message);
834: break;
835: case 'msg ':
836: var party1 = event._data;
1.54 ihickson 837: var party2 = viewers[event.data.substr(4).split(' ', 1)];
1.36 ihickson 838: if (party2) {
839: var channel = new MessageChannel();
1.84 ihickson 840: party1.port.postMessage('msg ' + party2.name, [channel.port1]);
841: party2.port.postMessage('msg ' + party1.name, [channel.port2]);
1.36 ihickson 842: }
843: break;
844: }
1.155 ihickson 845: }</pre><p><strong>Connecting to multiple pages</strong>. The script uses
1.115 ihickson 846: the <code title="handler-SharedWorkerGlobalScope-onconnect"><a href="#handler-sharedworkerglobalscope-onconnect">onconnect</a></code>
1.155 ihickson 847: event listener to listen for multiple connections.<p><strong>Direct channels</strong>. When the worker receives a
1.81 ihickson 848: "msg" message from one viewer naming another viewer, it sets up a
849: direct connection between the two, so that the two viewers can
850: communicate directly without the worker having to proxy all the
1.238 ihickson 851: messages.<p><a href="http://www.whatwg.org/demos/workers/multiviewer/page.html">View this example online</a>.<h4 id="delegation"><span class="secno">1.2.6 </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 852: performance is to split computationally expensive tasks amongst
853: multiple workers. In this example, a computationally expensive task
854: that is to be performed for every number from 1 to 10,000,000 is
1.155 ihickson 855: farmed out to ten subworkers.<p>The main page is as follows, it just reports the result:<pre><!DOCTYPE HTML>
1.81 ihickson 856: <html>
857: <head>
1.203 ihickson 858: <title>Worker example: Multicore computation</title>
1.81 ihickson 859: </head>
860: <body>
1.203 ihickson 861: <p>Result: <output id="result"></output></p>
1.81 ihickson 862: <script>
1.50 ihickson 863: var worker = new Worker('worker.js');
864: worker.onmessage = function (event) {
1.54 ihickson 865: document.getElementById('result').textContent = event.data;
1.40 ihickson 866: };
1.81 ihickson 867: </script>
868: </body>
1.155 ihickson 869: </html></pre><p>The worker itself is as follows:<pre>// settings
1.40 ihickson 870: var num_workers = 10;
871: var items_per_worker = 1000000;
872:
873: // start the workers
874: var result = 0;
875: var pending_workers = num_workers;
876: for (var i = 0; i < num_workers; i += 1) {
1.50 ihickson 877: var worker = new Worker('core.js');
878: worker.postMessage(i * items_per_worker);
879: worker.postMessage((i+1) * items_per_worker);
880: worker.onmessage = storeResult;
1.40 ihickson 881: }
882:
883: // handle the results
884: function storeResult(event) {
1.54 ihickson 885: result += 1*event.data;
1.40 ihickson 886: pending_workers -= 1;
887: if (pending_workers <= 0)
1.50 ihickson 888: postMessage(result); // finished!
1.155 ihickson 889: }</pre><p>It consists of a loop to start the subworkers, and then a handler
890: that waits for all the subworkers to respond.<p>The subworkers are implemented as follows:<pre>var start;
1.41 ihickson 891: onmessage = getStart;
1.40 ihickson 892: function getStart(event) {
1.54 ihickson 893: start = 1*event.data;
1.40 ihickson 894: onmessage = getEnd;
895: }
896:
897: var end;
898: function getEnd(event) {
1.54 ihickson 899: end = 1*event.data;
1.40 ihickson 900: onmessage = null;
1.66 ihickson 901: work();
1.40 ihickson 902: }
903:
1.66 ihickson 904: function work() {
1.40 ihickson 905: var result = 0;
906: for (var i = start; i < end; i += 1) {
907: // perform some complex calculation here
908: result += 1;
909: }
1.50 ihickson 910: postMessage(result);
911: close();
1.155 ihickson 912: }</pre><p>They receive two numbers in two events, perform the computation
1.81 ihickson 913: for the range of numbers thus specified, and then report the result
1.281 ihickson 914: back to the parent.<p><a href="http://www.whatwg.org/demos/workers/multicore/page.html">View this example online</a>.</p><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 915: non-normative, as are all sections explicitly marked non-normative.
1.281 ihickson 916: Everything else in this specification is normative.<p>The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
1.81 ihickson 917: "OPTIONAL" in the normative parts of this document are to be
918: interpreted as described in RFC2119. For readability, these words do
1.155 ihickson 919: 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 920: (such as "strip any leading space characters" or "return false and
921: abort these steps") are to be interpreted with the meaning of the
922: key word ("must", "should", "may", etc) used in introducing the
1.155 ihickson 923: algorithm.<p>Some conformance requirements are phrased as requirements on
1.81 ihickson 924: attributes, methods or objects. Such requirements are to be
1.155 ihickson 925: interpreted as requirements on user agents.<p>Conformance requirements phrased as algorithms or specific steps
1.81 ihickson 926: may be implemented in any manner, so long as the end result is
927: equivalent. (In particular, the algorithms defined in this
928: specification are intended to be easy to follow, and not intended to
1.155 ihickson 929: be performant.)<p>The only conformance class defined by this specification is user
930: agents.<p>User agents may impose implementation-specific limits on
1.81 ihickson 931: otherwise unconstrained inputs, e.g. to prevent denial of service
932: attacks, to guard against running out of memory, or to work around
1.229 ihickson 933: platform-specific limitations.<p>When support for a feature is disabled (e.g. as an emergency
934: measure to mitigate a security problem, or to aid in development, or
935: for performance reasons), user agents must act as if they had no
936: support for the feature whatsoever, and as if the feature was not
937: mentioned in this specification. For example, if a particular
938: feature is accessed via an attribute in a Web IDL interface, the
939: attribute itself would be omitted from the objects that implement
940: that interface — leaving the attribute on the object but
941: making it return null or throw an exception is insufficient.<h3 id="dependencies"><span class="secno">2.1 </span>Dependencies</h3><p>This specification relies on several other underlying
1.226 ihickson 942: specifications.<dl><dt>HTML</dt>
1.49 ihickson 943:
1.81 ihickson 944: <dd>
1.49 ihickson 945:
1.226 ihickson 946: <p>Many fundamental concepts from HTML are used by this
947: specification. <a href="#refsHTML">[HTML]</a></p>
1.49 ihickson 948:
1.81 ihickson 949: </dd>
1.1 ihickson 950:
1.81 ihickson 951: <dt>WebIDL</dt>
1.1 ihickson 952:
953: <dd>
954:
1.81 ihickson 955: <p>The IDL blocks in this specification use the semantics of the
1.153 ihickson 956: WebIDL specification. <a href="#refsWEBIDL">[WEBIDL]</a></p>
1.1 ihickson 957:
1.81 ihickson 958: </dd>
1.1 ihickson 959:
1.155 ihickson 960: </dl><h2 id="terminology"><span class="secno">3 </span>Terminology</h2><p>The construction "a <code title="">Foo</code> object", where
1.81 ihickson 961: <code title="">Foo</code> is actually an interface, is sometimes
962: used instead of the more accurate "an object implementing the
1.155 ihickson 963: interface <code title="">Foo</code>".<p>The term DOM is used to refer to the API set made available to
1.81 ihickson 964: scripts in Web applications, and does not necessarily imply the
965: existence of an actual <code>Document</code> object or of any other
966: <code>Node</code> objects as defined in the DOM Core
1.171 ihickson 967: specifications. <a href="#refsDOMCORE">[DOMCORE]</a><p>An IDL attribute is said to be <em>getting</em> when its value is
1.81 ihickson 968: being retrieved (e.g. by author script), and is said to be
1.155 ihickson 969: <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 970: the official term ECMAScript, since the term JavaScript is more
1.155 ihickson 971: 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 972: workers. Dedicated workers, once created, and are linked to their
973: creator; but message ports can be used to communicate from a
974: dedicated worker to multiple other browsing contexts or
975: workers. Shared workers, on the other hand, are named, and once
976: created any script running in the same <span>origin</span> can
1.155 ihickson 977: 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 978: readonly attribute <a href="#workerglobalscope">WorkerGlobalScope</a> <a href="#dom-workerglobalscope-self" title="dom-WorkerGlobalScope-self">self</a>;
979: readonly attribute <a href="#workerlocation">WorkerLocation</a> <a href="#dom-workerglobalscope-location" title="dom-WorkerGlobalScope-location">location</a>;
980:
981: void <a href="#dom-workerglobalscope-close" title="dom-WorkerGlobalScope-close">close</a>();
1.281 ihickson 982: attribute <span>Function</span> <a href="#handler-workerglobalscope-onerror" title="handler-WorkerGlobalScope-onerror">onerror</a>;
1.150 ihickson 983: };
1.172 ihickson 984: <a href="#workerglobalscope">WorkerGlobalScope</a> implements <a href="#workerutils">WorkerUtils</a>;
985: <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 986: 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 987: attribute must return the <code><a href="#workerlocation">WorkerLocation</a></code> object created
988: for the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object when the worker was
1.81 ihickson 989: created. It represents the <span>absolute URL</span> of the script
1.155 ihickson 990: 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 991: method on a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, the user agent
1.155 ihickson 992: must run the following steps (atomically):<ol><li><p>Discard any <span title="concept-task">tasks</span> that
1.123 ihickson 993: have been added to the <span>event loop</span>'s <span title="task
994: queue">task queues</span>.</p>
995:
1.81 ihickson 996:
1.115 ihickson 997: <li><p>Set the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's
998: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.123 ihickson 999: true. (This prevents any further tasks from being queued.)</li>
1.81 ihickson 1000:
1.177 ihickson 1001: </ol><p>The following are the <span>event handlers</span> (and their
1002: corresponding <span title="event handler event type">event handler
1003: event types</span>) that must be supported, as IDL attributes, by
1004: objects implementing the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1005: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.281 ihickson 1006: <tbody><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 1007: </table><hr><p>The <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> interface must not exist if
1008: the interface's <span>relevant namespace object</span> is a
1009: <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 1010: interface <dfn id="dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</dfn> : <a href="#workerglobalscope">WorkerGlobalScope</a> {
1.286 ihickson 1011: void <a href="#dom-dedicatedworkerglobalscope-postmessage" title="dom-DedicatedWorkerGlobalScope-postMessage">postMessage</a>(in any message, in optional sequence<<span>MessagePort</span>> ports); attribute <span>Function</span> <a href="#handler-dedicatedworkerglobalscope-onmessage" title="handler-DedicatedWorkerGlobalScope-onmessage">onmessage</a>;
1.155 ihickson 1012: };</pre><p><code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> objects act as if they
1.81 ihickson 1013: had an implicit <code>MessagePort</code> associated with them. This
1014: port is part of a channel that is set up when the worker is created,
1015: but it is not exposed. This object must never be garbage collected
1.155 ihickson 1016: before the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object.<p>All messages received by that port must immediately be retargeted
1.281 ihickson 1017: 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> method on
1.115 ihickson 1018: <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> objects must act as if, when
1.281 ihickson 1019: invoked, it immediately invoked the
1.81 ihickson 1020: method of the same name on the port, with the same arguments, and
1.177 ihickson 1021: returned the same return value.<p>The following are the <span>event handlers</span> (and their
1022: corresponding <span title="event handler event type">event handler
1023: event types</span>) that must be supported, as IDL attributes, by
1024: objects implementing the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
1025: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1026: <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 1027: </table><p>For the purposes of the <span>application cache</span> networking
1028: model, a dedicated worker is an extension of the <span>cache
1.270 ihickson 1029: host</span> from which it was created.<h4 id="shared-workers-and-the-sharedworkerglobalscope-interface"><span class="secno">4.1.3 </span>Shared workers and the <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> interface</h4><pre class="idl">[Supplemental, NoInterfaceObject]
1.150 ihickson 1030: interface <dfn id="sharedworkerglobalscope">SharedWorkerGlobalScope</dfn> : <a href="#workerglobalscope">WorkerGlobalScope</a> {
1.115 ihickson 1031: readonly attribute DOMString <a href="#dom-sharedworkerglobalscope-name" title="dom-SharedWorkerGlobalScope-name">name</a>;
1.181 ihickson 1032: readonly attribute <span>ApplicationCache</span> <span title="dom-SharedWorkerGlobalScope-applicationCache">applicationCache</span>;
1.144 ihickson 1033: attribute <span>Function</span> <a href="#handler-sharedworkerglobalscope-onconnect" title="handler-SharedWorkerGlobalScope-onconnect">onconnect</a>;
1.155 ihickson 1034: };</pre><p>Shared workers receive message ports through <code title="event-WorkerGlobalScope-connect">connect</code> events on
1035: their global object for each connection.<p>The <dfn id="dom-sharedworkerglobalscope-name" title="dom-SharedWorkerGlobalScope-name"><code>name</code></dfn>
1.81 ihickson 1036: attribute must return the value it was assigned when the
1.115 ihickson 1037: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object was created by the
1038: "<a href="#run-a-worker">run a worker</a>" algorithm. Its value represents the name
1.81 ihickson 1039: that can be used to obtain a reference to the worker using the
1.177 ihickson 1040: <code><a href="#sharedworker">SharedWorker</a></code> constructor.<p>The following are the <span>event handlers</span> (and their
1041: corresponding <span title="event handler event type">event handler
1042: event types</span>) that must be supported, as IDL attributes, by
1043: objects implementing the <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1044: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1045: <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 1046: </table><p>For the purposes of the <span>application cache</span> networking
1047: model, a shared worker is its own <span>cache host</span>. The
1048: <a href="#run-a-worker">run a worker</a> algorithm takes care of associating the
1049: worker with an <span>application cache</span>.<p class="note">The <code title="dom-SharedWorkerGlobalScope-applicationCache">applicationCache</code>
1.123 ihickson 1050: attribute returns the <code>ApplicationCache</code> object for the
1.281 ihickson 1051: worker.</p><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 1052: origin</span> of scripts running in workers are the
1053: <span>origin</span> of the <span>absolute URL</span> given in that
1.115 ihickson 1054: the worker's <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1.186 ihickson 1055: 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 1056: loop</span> distinct from those defined for <span title="unit of
1057: related similar-origin browsing contexts">units of related
1058: similar-origin browsing contexts</span>. This <span>event
1059: loop</span> has no associated <span>browsing context</span>, and its
1060: <span title="task queue">task queues</span> only have events,
1061: callbacks, and networking activity as <span title="concept-task">tasks</span>. The processing model of these
1062: <span title="event loop">event loops</span> is defined below in the
1.155 ihickson 1063: <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 1064: initially be false, but which can get set to true by the algorithms
1.155 ihickson 1065: 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 1066: true, the <span>event loop</span>'s <span title="task queue">task
1.115 ihickson 1067: queues</span> must discard any further <span title="concept-task">tasks</span> that would be added to them (tasks
1.175 ihickson 1068: already on the queue are unaffected except where otherwise
1.115 ihickson 1069: specified). Effectively, once the <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is true,
1.81 ihickson 1070: timers stop firing, notifications for all pending asynchronous
1.186 ihickson 1071: 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 1072: <code>MessagePort</code> objects.<p>Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> <var title="">worker global
1.124 ihickson 1073: scope</var> has a list of <dfn id="the-worker-s-ports">the worker's ports</dfn>, which
1.81 ihickson 1074: consists of all the <code>MessagePort</code> objects that are
1075: entangled with another port and that have one (but only one) port
1076: owned by <var title="">worker global scope</var>. This list includes
1.281 ihickson 1077: the implicit
1.155 ihickson 1078: <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 1079: worker's workers</dfn>. Initially this list is empty; it is
1.155 ihickson 1080: 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 1081: <dfn id="the-worker-s-documents">the worker's <code>Document</code>s</dfn>. Initially this list
1.155 ihickson 1082: 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 1083: worker's <code>Document</code>s</dfn>, the user agent must, for each
1.124 ihickson 1084: worker in the list of <a href="#the-worker-s-workers">the worker's workers</a> whose list
1085: of <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> does not contain
1086: <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 1087: documents">add <var title="">d</var> to <var title="">q</var>'s
1088: <code>WorkerGlobalScope</code> owner's list of <span>the worker's
1.281 ihickson 1089: <code>Document</code>s</span></a>.</p><p>Whenever a <code>Document</code> object is <span title="discard a
1.123 ihickson 1090: Document">discarded</span>, it must be removed from the list of
1091: <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> of each worker
1.192 ihickson 1092: whose list contains that <code>Document</code>.<p>Given a <span>script's global object</span> <var title="">o</var>
1.123 ihickson 1093: when creating or obtaining a worker, the <dfn id="list-of-relevant-document-objects-to-add">list of relevant
1094: <code>Document</code> objects to add</dfn> depends on the type of
1095: <var title="">o</var>. If <var title="">o</var> is a
1096: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object (i.e. if we are creating a
1097: nested worker), then the relevant <code>Document</code>s are the
1098: <code>Document</code>s that are in <var title="">o</var>'s own list
1099: 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
1100: <code>Document</code> is just the <code>Document</code> that is the
1.155 ihickson 1101: <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 1102: list of <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> is not
1.155 ihickson 1103: empty.<p>A worker is said to be a <dfn id="protected-worker">protected worker</dfn> if it is a
1.123 ihickson 1104: <a href="#permissible-worker">permissible worker</a> and either it has outstanding
1105: timers, database transactions, or network connections, or its list
1.124 ihickson 1106: of <a href="#the-worker-s-ports">the worker's ports</a> is not empty, or its
1.123 ihickson 1107: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> is actually a
1108: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object (i.e. the worker is a
1.155 ihickson 1109: shared worker).<p>A worker is said to be an <dfn id="active-needed-worker">active needed worker</dfn> if any
1.123 ihickson 1110: of the <code>Document</code> objects in <a href="#the-worker-s-documents">the worker's
1.155 ihickson 1111: <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 1112: not an <a href="#active-needed-worker">active needed worker</a> but it is a
1.186 ihickson 1113: <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
1.232 ihickson 1114: <span>URL</span> <var title="">url</var>, a <span>browsing
1115: context</span> <var title="">owner browsing context</var>, a
1116: <code>Document</code> <var title="">owner document</var>, an
1117: <span>origin</span> <var title="">owner origin</var>, and with
1118: global scope <var title="">worker global scope</var>, it must run
1119: the following steps:<ol><li>
1.81 ihickson 1120:
1.274 ihickson 1121: <p>Create a separate parallel execution environment (i.e. a
1122: separate thread or process or equivalent construct), and run the
1123: rest of these steps asynchronously in that context.</p>
1.81 ihickson 1124:
1125: </li>
1.4 ihickson 1126:
1.101 ihickson 1127: <li><p>If <var title="">worker global scope</var> is actually a
1.115 ihickson 1128: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object (i.e. the worker is a
1.101 ihickson 1129: shared worker), and there are any <span title="relevant application
1130: cache">relevant application caches</span> that are identified by a
1131: 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 1132: their entries, <em>not</em> excluding entries marked as <span title="concept-appcache-foreign">foreign</span>, then associate the
1133: <var title="">worker global scope</var> with the <span title="concept-appcache-selection">most appropriate application
1.101 ihickson 1134: cache</span> of those that match.</li>
1135:
1.4 ihickson 1136: <li>
1.52 ihickson 1137:
1.256 ihickson 1138: <p>Attempt to <span>fetch</span> the resource identified by <var title="">url</var>, from the <var title="">owner origin</var>,
1139: with the <i>synchronous flag</i> set and the <i>force same-origin
1.281 ihickson 1140: flag</i> set.</p>
1.256 ihickson 1141: <p>If the attempt fails, then for each <code><a href="#worker">Worker</a></code> or
1142: <code><a href="#sharedworker">SharedWorker</a></code> object associated with <var title="">worker global scope</var>, <span>queue a task</span> to
1143: <span>fire a simple event</span> named <code title="event-error">error</code> at that object. Abort these
1144: steps.</p>
1.7 ihickson 1145:
1.264 ihickson 1146: <p>If the attempt succeeds, then let <var title="">source</var> be
1147: the script resource <span>decoded as UTF-8, with error
1148: handling</span>.
1149:
1150: <a href="#refsHTML">[HTML]</a>
1151:
1152: </p>
1.81 ihickson 1153:
1.68 ihickson 1154: <p>Let <var title="">language</var> be JavaScript.</p>
1.7 ihickson 1155:
1.115 ihickson 1156: <p class="note">As with <code>script</code> elements, the MIME
1.81 ihickson 1157: type of the script is ignored. Unlike with <code>script</code>
1158: elements, there is no way to override the type. It's always
1.170 ihickson 1159: assumed to be JavaScript.</p>
1.81 ihickson 1160:
1161: </li>
1.7 ihickson 1162:
1163: <li>
1.68 ihickson 1164:
1.115 ihickson 1165: <p>A new <span title="concept-script">script</span> is now
1.81 ihickson 1166: created, as follows.</p>
1167:
1168: <p>Create a new <span>script execution environment</span>
1169: set up as appropriate for the scripting language <var title="">language</var>.</p>
1.34 ihickson 1170:
1.68 ihickson 1171: <p>Parse/compile/initialize <var title="">source</var> using that
1.81 ihickson 1172: <span>script execution environment</span>, as appropriate for <var title="">language</var>, and thus obtain a <span>list of code
1173: entry-points</span>; set the <i>initial code entry-point</i> to
1174: the entry-point for any executable code to be immediately run.</p>
1175:
1176: <p>Set the <span>script's global object</span> to <var title="">worker global scope</var>.</p>
1177:
1178: <p>Set the <span>script's browsing context</span> to <var title="">owner browsing context</var>.</p>
1179:
1.232 ihickson 1180: <p>Set the <span>script's document</span> to <var title="">owner
1181: document</var>.</p>
1182:
1.83 ihickson 1183: <p>Set the <span>script's URL character encoding</span> to
1.81 ihickson 1184: UTF-8. (This is just used for encoding non-ASCII characters in the
1185: query component of URLs.)</p>
1.68 ihickson 1186:
1187: <p>Set the <span>script's base URL</span> to <var title="">url</var>.</p>
1.4 ihickson 1188:
1.81 ihickson 1189: </li>
1.4 ihickson 1190:
1191: <li>
1.81 ihickson 1192:
1193: <p><strong>Closing orphan workers</strong>: Start monitoring the
1.125 ihickson 1194: worker such that no sooner than it stops being either a
1195: <a href="#protected-worker">protected worker</a> or a <a href="#suspendable-worker">suspendable
1.123 ihickson 1196: worker</a>, and no later than it stops being a
1197: <a href="#permissible-worker">permissible worker</a>, <var title="">worker global
1198: scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is set
1.281 ihickson 1199: to true.</p>
1.81 ihickson 1200:
1201: </li>
1.9 ihickson 1202:
1203: <li>
1.7 ihickson 1204:
1.81 ihickson 1205: <p><strong>Suspending workers</strong>: Start monitoring the
1206: worker, such that whenever <var title="">worker global
1.115 ihickson 1207: scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is false
1208: and the worker is a <a href="#suspendable-worker">suspendable worker</a>, the user
1.81 ihickson 1209: agent suspends execution of script in that worker until such time
1.115 ihickson 1210: as either the <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag switches
1211: to true or the worker stops being a <a href="#suspendable-worker">suspendable
1.81 ihickson 1212: worker</a>.</p>
1.4 ihickson 1213:
1.81 ihickson 1214: </li>
1.68 ihickson 1215:
1216: <li>
1.4 ihickson 1217:
1.81 ihickson 1218: <p><span title="jump to a code entry-point">Jump</span> to the
1.115 ihickson 1219: <span title="concept-script">script</span>'s <i>initial code
1.81 ihickson 1220: entry-point</i>, and let that run until it either returns, fails
1221: to catch an exception, or gets prematurely aborted by the
1.115 ihickson 1222: "<a href="#kill-a-worker">kill a worker</a>" or "<a href="#terminate-a-worker">terminate a worker</a>"
1.81 ihickson 1223: algorithms defined below.</p>
1224:
1.4 ihickson 1225:
1.81 ihickson 1226: </li>
1.4 ihickson 1227:
1.95 ihickson 1228: <li><p>If <var title="">worker global scope</var> is actually a
1.115 ihickson 1229: <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object (i.e. the worker is
1.126 ihickson 1230: a dedicated worker), then enable the <span>port message
1231: queue</span> of the worker's implicit port.</li>
1.95 ihickson 1232:
1.4 ihickson 1233: <li>
1.68 ihickson 1234:
1.115 ihickson 1235: <p><i title="">Event loop</i>: Wait until either there is a <span title="concept-task">task</span> in one of the <span>event
1236: 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 1237: to true.</p>
1.43 ihickson 1238:
1.81 ihickson 1239: </li>
1.4 ihickson 1240:
1241: <li>
1242:
1.81 ihickson 1243: <p>Run the oldest task on one of the <span>event loop</span>'s
1244: <span title="task queue">task queues</span>, if any. The user
1245: agent may pick any <span>task queue</span>.</p>
1246:
1.115 ihickson 1247: <p class="note">The handling of events or the execution of
1248: callbacks might get prematurely aborted by the "<a href="#kill-a-worker">kill a
1249: worker</a>" or "<a href="#terminate-a-worker">terminate a worker</a>" algorithms
1.81 ihickson 1250: defined below.</p>
1.8 ihickson 1251:
1.81 ihickson 1252: </li>
1.4 ihickson 1253:
1254: <li>
1255:
1.248 ihickson 1256: <p>If the <span>storage mutex</span> is now owned by the worker's
1257: <span>event loop</span>, release it so that it is once again
1258: free.</p>
1259:
1260: </li>
1261:
1262: <li>
1263:
1264: <p>Remove the task just run in the earlier step, if any, from its
1.81 ihickson 1265: <span>task queue</span>.</p>
1.4 ihickson 1266:
1.81 ihickson 1267: </li>
1.4 ihickson 1268:
1269: <li>
1.8 ihickson 1270:
1.81 ihickson 1271: <p>If there are any more events in the <span>event loop</span>'s
1.115 ihickson 1272: <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 1273: to false, then jump back to the step above labeled <i>event
1274: loop</i>.</p>
1.8 ihickson 1275:
1.81 ihickson 1276: </li>
1.8 ihickson 1277:
1278: <li>
1.71 ihickson 1279:
1.123 ihickson 1280: <p>Empty the <var title="">worker global scope</var>'s <span>list
1281: of active timeouts</span> and its <span>list of active
1282: intervals</span>.</p>
1.50 ihickson 1283:
1.81 ihickson 1284: </li>
1.50 ihickson 1285:
1.247 ihickson 1286: <li>
1287:
1288: <p>Disentangle all the ports in the list of <a href="#the-worker-s-ports">the worker's
1289: ports</a>.</p>
1290:
1291: </li>
1292:
1.155 ihickson 1293: </ol><hr><p>When a user agent is to <dfn id="kill-a-worker">kill a worker</dfn> it must
1.81 ihickson 1294: run the following steps in parallel with the worker's main loop (the
1.281 ihickson 1295: "<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 <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.81 ihickson 1296: true.</li>
1297:
1298:
1.115 ihickson 1299: <li><p>If there are any <span title="concept-task">tasks</span>
1.81 ihickson 1300: queued in the <span>event loop</span>'s <span title="task
1.281 ihickson 1301: queue">task queues</span>, discard them without processing them.</li>
1302:
1.81 ihickson 1303:
1304: <li><p>Wait a user-agent-defined amount of time.</li>
1305:
1.281 ihickson 1306: <li><p>Abort the script currently running in the worker.</li>
1.81 ihickson 1307:
1.155 ihickson 1308: </ol><p>User agents may invoke the "<a href="#kill-a-worker">kill a worker</a>"
1.81 ihickson 1309: processing model on a worker at any time, e.g. in response to user
1310: requests, in response to CPU quota management, or when a worker
1.115 ihickson 1311: stops being an <a href="#active-needed-worker">active needed worker</a> if the worker
1312: continues executing even after its <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag was
1.155 ihickson 1313: 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 1314: the following steps in parallel with the worker's main loop (the
1.155 ihickson 1315: "<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 1316: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.81 ihickson 1317: true.</li>
1318:
1.115 ihickson 1319: <li><p>If there are any <span title="concept-task">tasks</span>
1.81 ihickson 1320: queued in the <span>event loop</span>'s <span title="task
1321: queue">task queues</span>, discard them without processing
1322: them.</li>
1323:
1324: <li><p>Abort the script currently running in the worker.</li>
1325:
1.115 ihickson 1326: <li><p>If the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object is
1327: actually a <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object (i.e. the
1.81 ihickson 1328: worker is a dedicated worker), then empty the <span>port message
1329: queue</span> of the port that the worker's implicit port is
1330: entangled with.</li>
1331:
1.155 ihickson 1332: </ol><hr><p>The <span>task source</span> for the tasks mentioned above is the
1.186 ihickson 1333: <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 1334: worker's scripts, if the error did not occur while handling a
1335: previous script error, the user agent must <span>report the
1336: 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 1337: attribute.
1338:
1.226 ihickson 1339: <a href="#refsHTML">[HTML]</a>
1.205 ihickson 1340:
1341: <p>For shared workers, if the error is still <i title="concept-error-nothandled">not handled</i> afterwards, or if
1.132 ihickson 1342: the error occurred while handling a previous script error, the error
1.215 ihickson 1343: may be reported to the user.
1.205 ihickson 1344:
1.226 ihickson 1345: <a href="#refsHTML">[HTML]</a>
1.205 ihickson 1346:
1347: <p>For dedicated workers, if the error is still <i title="concept-error-nothandled">not handled</i> afterwards, or if
1.132 ihickson 1348: the error occurred while handling a previous script error, the user
1.123 ihickson 1349: agent must <span>queue a task</span> to <a href="#fire-a-worker-error-event">fire a worker error
1350: event</a> at the <code><a href="#worker">Worker</a></code> object associated with the
1.155 ihickson 1351: 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 1352: a <code><a href="#worker">Worker</a></code> object, it must dispatch an event that uses
1353: 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 1354: 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 1355: appropriately. The default action of this event depends on whether
1.115 ihickson 1356: the <code><a href="#worker">Worker</a></code> object is itself in a worker. If it is, and
1.81 ihickson 1357: that worker is also a dedicated worker, then the user agent must
1.118 ihickson 1358: again <span>queue a task</span> to <a href="#fire-a-worker-error-event">fire a worker error
1359: event</a> at the <code><a href="#worker">Worker</a></code> object associated with
1.215 ihickson 1360: <em>that</em> worker. Otherwise, then the error may be reported
1.155 ihickson 1361: to the user.<p>The <span>task source</span> for the tasks mentioned above is the
1.233 ihickson 1362: <span>DOM manipulation task source</span>.<hr><pre class="idl">interface <dfn id="errorevent">ErrorEvent</dfn> : <span>Event</span> {
1.147 ihickson 1363: readonly attribute DOMString <a href="#dom-errorevent-message" title="dom-ErrorEvent-message">message</a>;
1364: readonly attribute DOMString <a href="#dom-errorevent-filename" title="dom-ErrorEvent-filename">filename</a>;
1.115 ihickson 1365: readonly attribute unsigned long <a href="#dom-errorevent-lineno" title="dom-ErrorEvent-lineno">lineno</a>;
1.147 ihickson 1366: 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 1367: };</pre><p>The <dfn id="dom-errorevent-initerrorevent" title="dom-ErrorEvent-initErrorEvent"><code>initErrorEvent()</code></dfn>
1.190 ihickson 1368: method must initialize the event in a manner analogous to the
1369: 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 1370: attribute represents the error message.<p>The <dfn id="dom-errorevent-filename" title="dom-ErrorEvent-filename"><code>filename</code></dfn>
1.81 ihickson 1371: attribute represents the <span>absolute URL</span> of the script in
1.155 ihickson 1372: which the error originally occurred.<p>The <dfn id="dom-errorevent-lineno" title="dom-ErrorEvent-lineno"><code>lineno</code></dfn>
1.132 ihickson 1373: attribute represents the line number where the error occurred in the
1.208 ihickson 1374: 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]
1375: interface <dfn id="abstractworker">AbstractWorker</dfn> {
1.144 ihickson 1376: attribute <span>Function</span> <a href="#handler-abstractworker-onerror" title="handler-AbstractWorker-onerror">onerror</a>;
1.172 ihickson 1377: };
1.177 ihickson 1378: <a href="#abstractworker">AbstractWorker</a> implements <span>EventTarget</span>;</pre><p>The following are the <span>event handlers</span> (and their
1379: corresponding <span title="event handler event type">event handler
1380: event types</span>) that must be supported, as IDL attributes, by
1381: 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 1382: <tbody><tr><td><dfn id="handler-abstractworker-onerror" title="handler-AbstractWorker-onerror"><code>onerror</code></dfn> <td> <code title="event-error">error</code>
1.186 ihickson 1383: </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 1384: interface <dfn id="worker">Worker</dfn> : <a href="#abstractworker">AbstractWorker</a> {
1385: void <a href="#dom-worker-terminate" title="dom-Worker-terminate">terminate</a>();
1.50 ihickson 1386:
1.286 ihickson 1387: void <a href="#dom-worker-postmessage" title="dom-Worker-postMessage">postMessage</a>(in any message, in optional sequence<<span>MessagePort</span>> ports); attribute <span>Function</span> <a href="#handler-worker-onmessage" title="handler-Worker-onmessage">onmessage</a>;
1.155 ihickson 1388: };</pre><p>The <dfn id="dom-worker-terminate" title="dom-Worker-terminate"><code>terminate()</code></dfn> method,
1.115 ihickson 1389: when invoked, must cause the "<a href="#terminate-a-worker">terminate a worker</a>"
1.81 ihickson 1390: algorithm to be run on the worker with with the object is
1.155 ihickson 1391: associated.<p><code><a href="#worker">Worker</a></code> objects act as if they had an implicit
1.81 ihickson 1392: <code>MessagePort</code> associated with them. This port is part of
1393: a channel that is set up when the worker is created, but it is not
1394: exposed. This object must never be garbage collected before the
1.155 ihickson 1395: <code><a href="#worker">Worker</a></code> object.<p>All messages received by that port must immediately be retargeted
1.281 ihickson 1396: 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> method on <code><a href="#worker">Worker</a></code> objects
1397: must act as if, when invoked, it
1.81 ihickson 1398: immediately invoked the method of the same name on the port, with
1.177 ihickson 1399: the same arguments, and returned the same return value.<p>The following are the <span>event handlers</span> (and their
1400: corresponding <span title="event handler event type">event handler
1401: event types</span>) that must be supported, as IDL attributes, by
1402: 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 1403: <tbody><tr><td><dfn id="handler-worker-onmessage" title="handler-Worker-onmessage"><code>onmessage</code></dfn> <td> <code title="event-message">message</code>
1404: </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 1405: 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 1406: script</span>'s <span title="script's base URL">base URL</span>,
1407: when the method is invoked.</li>
1.9 ihickson 1408:
1.81 ihickson 1409: <li><p>If this fails, throw a <code>SYNTAX_ERR</code>
1410: exception.</li>
1.9 ihickson 1411:
1.167 ihickson 1412: <li>
1413:
1414: <p>If the <span>origin</span> of the resulting <span>absolute
1415: URL</span> is not the <span title="same origin">same</span> as the
1.216 ihickson 1416: origin of the <span>entry script</span>, then throw a
1.182 ihickson 1417: <code>SECURITY_ERR</code> exception.</p>
1.167 ihickson 1418:
1419: <p class="note">Thus, scripts must be external files with the same
1.269 ihickson 1420: scheme as the original page: you can't load a script from a <span title="data protocol"><code title="">data:</code> URL</span> or
1421: <span title="javascript protocol"><code title="">javascript:</code> URL</span>, and an <code>http:</code>
1422: page couldn't start workers using scripts with <code>http:</code>
1423: URLs.</p>
1.167 ihickson 1424:
1425: </li>
1.9 ihickson 1426:
1.185 ihickson 1427: <li><p>Create a new <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
1428: object. Let <var title="">worker global scope</var> be this new
1429: object.</li>
1.9 ihickson 1430:
1.115 ihickson 1431: <li><p>Create a new <code><a href="#worker">Worker</a></code> object, associated with
1.81 ihickson 1432: <var title="">worker global scope</var>. Let <var title="">worker</var> be this new object.</li>
1.50 ihickson 1433:
1.185 ihickson 1434: <li><p><span>Create a new <code>MessagePort</code> object</span>
1.192 ihickson 1435: owned by the <span title="script's global object">global
1436: object</span> of the <span title="concept-script">script</span> that
1.185 ihickson 1437: invoked the constructor. Let this be the <var title="">outside
1.81 ihickson 1438: port</var>.</li>
1.9 ihickson 1439:
1.81 ihickson 1440: <li><p>Associate the <var title="">outside port</var> with <var title="">worker</var>.</li>
1.50 ihickson 1441:
1.185 ihickson 1442: <li><p><span>Create a new <code>MessagePort</code> object</span>
1443: owned by <var title="">worker global scope</var>. Let <var title="">inside port</var> be this new object.</li>
1.50 ihickson 1444:
1.81 ihickson 1445: <li><p>Associate <var title="">inside port</var> with <var title="">worker global scope</var>.</li>
1.50 ihickson 1446:
1.81 ihickson 1447: <li><p><span>Entangle</span> <var title="">outside port</var> and
1448: <var title="">inside port</var>.</li>
1.50 ihickson 1449:
1.81 ihickson 1450: <li><p>Return <var title="">worker</var>, and run the following
1451: steps asynchronously.</li>
1.50 ihickson 1452:
1453:
1.126 ihickson 1454: <li><p>Enable <var title="">outside port</var>'s <span>port message
1.81 ihickson 1455: queue</span>.</li>
1.50 ihickson 1456:
1457: <li>
1.51 ihickson 1458:
1.123 ihickson 1459: <p>Let <var title="">docs</var> be the <a href="#list-of-relevant-document-objects-to-add">list of relevant
1.192 ihickson 1460: <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 1461: constructor.</p>
1462:
1463: </li>
1464:
1465: <li>
1466:
1467: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1468: <var title="">worker global scope</var>'s list of <span>the
1469: worker's <code>Document</code>s</span></a> the
1470: <code>Document</code> objects in <var title="">docs</var>.</p>
1471:
1472: </li>
1473:
1474: <li>
1475:
1.192 ihickson 1476: <p>If the <span title="script's global object">global object</span>
1.124 ihickson 1477: of the <span title="concept-script">script</span> that invoked the
1478: constructor is a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object (i.e. we
1479: are creating a nested worker), add <var title="">worker global
1480: scope</var> to the list of <a href="#the-worker-s-workers">the worker's workers</a> of the
1.192 ihickson 1481: <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 1482: constructor.</p>
1483:
1484: </li>
1485:
1486: <li>
1487:
1.115 ihickson 1488: <p><a href="#run-a-worker">Run a worker</a> for the resulting <span>absolute
1.193 ihickson 1489: URL</span>, with the <span>script's browsing context</span> of the
1.81 ihickson 1490: script that invoked the method as the <var title="">owner browsing
1.232 ihickson 1491: context</var>, with the <span>script's document</span> of the
1492: script that invoked the method as the <var title="">owner
1493: document</var>, with the <span>origin</span> of the <span>entry
1.176 ihickson 1494: script</span> as the <var title="">owner origin</var>, and with
1495: <var title="">worker global scope</var> as the global scope.</p>
1.9 ihickson 1496:
1.81 ihickson 1497: </li>
1.4 ihickson 1498:
1.155 ihickson 1499: </ol><p>This constructor must be visible when the <span>script's global
1.192 ihickson 1500: object</span> is either a <code>Window</code> object or an object
1.186 ihickson 1501: 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 1502: interface <dfn id="sharedworker">SharedWorker</dfn> : <a href="#abstractworker">AbstractWorker</a> {
1503: readonly attribute <span>MessagePort</span> <a href="#dom-sharedworker-port" title="dom-SharedWorker-port">port</a>;
1.155 ihickson 1504: };</pre><p>The <dfn id="dom-sharedworker-port" title="dom-SharedWorker-port"><code>port</code></dfn>
1.81 ihickson 1505: attribute must return the value it was assigned by the object's
1506: constructor. It represents the <code>MessagePort</code> for
1.155 ihickson 1507: 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 1508: constructor is invoked, the user agent must run the following
1.155 ihickson 1509: steps:<ol><li><p><span title="resolve a url">Resolve</span> the <var title="">scriptURL</var> argument.</li>
1.81 ihickson 1510:
1511: <li><p>If this fails, throw a <code>SYNTAX_ERR</code>
1512: exception.</li>
1513:
1.159 ihickson 1514: <li><p>Otherwise, let <var title="">scriptURL</var> be the
1515: resulting <span>absolute URL</span>.</li>
1516:
1517: <li><p>Let <var title="">name</var> be the value of the second
1.164 ihickson 1518: argument, or the empty string if the second argument was
1519: omitted.</li>
1.159 ihickson 1520:
1.167 ihickson 1521: <li>
1522:
1523: <p>If the <span>origin</span> of <var title="">scriptURL</var> is
1524: not the <span title="same origin">same</span> as the origin of the
1.216 ihickson 1525: <span>entry script</span>, then throw a <code>SECURITY_ERR</code>
1.182 ihickson 1526: exception.</p>
1.167 ihickson 1527:
1528: <p class="note">Thus, scripts must be external files with the same
1.269 ihickson 1529: scheme as the original page: you can't load a script from a <span title="data protocol"><code title="">data:</code> URL</span> or
1530: <span title="javascript protocol"><code title="">javascript:</code> URL</span>, and a <code>http:</code>
1531: page couldn't start workers using scripts with <code>http:</code>
1532: URLs.</p>
1.167 ihickson 1533:
1534: </li>
1.9 ihickson 1535:
1536: <li>
1537:
1.123 ihickson 1538: <p>Let <var title="">docs</var> be the <a href="#list-of-relevant-document-objects-to-add">list of relevant
1.192 ihickson 1539: <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 1540: constructor.</p>
1541:
1542: </li>
1543:
1544: <li>
1545:
1.50 ihickson 1546: <p>Execute the following substeps atomically:</p>
1.9 ihickson 1547:
1.155 ihickson 1548: <ol><li><p>Create a new <code><a href="#sharedworker">SharedWorker</a></code> object, which will
1.115 ihickson 1549: shortly be associated with a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1550: object. Let this <code><a href="#sharedworker">SharedWorker</a></code> object be <var title="">worker</var>.</li>
1.81 ihickson 1551:
1.185 ihickson 1552: <li><p><span>Create a new <code>MessagePort</code> object</span>
1.192 ihickson 1553: owned by the <span title="script's global object">global
1554: object</span> of the script that invoked the method. Let this be
1.123 ihickson 1555: the <var title="">outside port</var>.</li>
1.81 ihickson 1556:
1.115 ihickson 1557: <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 1558:
1.164 ihickson 1559: <li><p>Let <var title="">worker global scope</var> be
1560: null.</li>
1561:
1562: <li><p>If <var title="">name</var> is not the empty string and
1563: there exists a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object whose
1564: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag
1565: is false, whose <code title="dom-WorkerGlobalScope-name">name</code> attribute is
1566: exactly equal to <var title="">name</var>, and whose <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1567: represents an <span>absolute URL</span> with the <span>same
1568: origin</span> as <var title="">scriptURL</var>, then let <var title="">worker global scope</var> be that
1569: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object.</li>
1570:
1571: <li><p>Otherwise, if <var title="">name</var> is the empty string
1572: and there exists a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object
1573: whose <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a>
1574: flag is false, and whose <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1.237 ihickson 1575: represents an <span>absolute URL</span> that is exactly equal to
1576: <var title="">scriptURL</var>, then let <var title="">worker
1577: global scope</var> be that <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1578: object.</li>
1.164 ihickson 1579:
1.9 ihickson 1580: <li>
1581:
1.164 ihickson 1582: <p>If <var title="">worker global scope</var> is not null, then
1583: run these steps:</p>
1.81 ihickson 1584:
1.164 ihickson 1585: <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 1586: attribute represents an <span>absolute URL</span> that is not
1.159 ihickson 1587: exactly equal to <var title="">scriptURL</var>, then throw a
1588: <code>URL_MISMATCH_ERR</code> exception and abort all these
1589: steps.</li>
1.81 ihickson 1590:
1591: <li><p>Associate <var title="">worker</var> with <var title="">worker global scope</var>.</li>
1592:
1.185 ihickson 1593: <li><p><span>Create a new <code>MessagePort</code>
1594: object</span> owned by <var title="">worker global
1595: scope</var>. Let this be the <var title="">inside
1596: port</var>.</li>
1.81 ihickson 1597:
1598: <li><p><span>Entangle</span> <var title="">outside port</var>
1599: and <var title="">inside port</var>.</li>
1600:
1601: <li><p>Return <var title="">worker</var> and perform the next
1602: step asynchronously.</li>
1.9 ihickson 1603:
1.81 ihickson 1604: <li><p>Create an event that uses the <code>MessageEvent</code>
1.115 ihickson 1605: interface, with the name <code title="event-connect">connect</code>, which does not bubble, is
1.118 ihickson 1606: not cancelable, has no default action, has a <code title="dom-MessageEvent-data">data</code> attribute whose value
1607: is the empty string and has a <code title="dom-MessageEvent-ports">ports</code> attribute whose
1.286 ihickson 1608: value is a <span title="dfn-read-only-array">read only</span>
1609: array containing only the newly created port, and <span>queue a
1610: task</span> to dispatch the event at <var title="">worker
1611: global scope</var>.</li>
1.43 ihickson 1612:
1.123 ihickson 1613: <li>
1614:
1615: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1616: <var title="">worker global scope</var>'s list of <span>the
1617: worker's <code>Document</code>s</span></a> the
1618: <code>Document</code> objects in <var title="">docs</var>.</p>
1619:
1620: </li>
1621:
1.124 ihickson 1622: <li>
1623:
1.192 ihickson 1624: <p>If the <span title="script's global object">global
1625: object</span> of the <span title="concept-script">script</span>
1.124 ihickson 1626: that invoked the constructor is a
1627: <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
1628: worker's workers</a> of the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1.192 ihickson 1629: object that is the <span title="script's global object">global
1630: object</span> of the <span title="concept-script">script</span>
1.124 ihickson 1631: that invoked the constructor.</p>
1632:
1633: </li>
1634:
1.81 ihickson 1635: <li><p>Abort all these steps.</li>
1.9 ihickson 1636:
1.155 ihickson 1637: </ol></li>
1.9 ihickson 1638:
1.185 ihickson 1639: <li><p>Create a new <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1640: object. Let <var title="">worker global scope</var> be this new
1641: object.</li>
1.9 ihickson 1642:
1.81 ihickson 1643: <li><p>Associate <var title="">worker</var> with <var title="">worker global scope</var>.</li>
1.9 ihickson 1644:
1.115 ihickson 1645: <li><p>Set the <code title="dom-SharedWorkerGlobalScope-name"><a href="#dom-sharedworkerglobalscope-name">name</a></code> attribute of
1.81 ihickson 1646: <var title="">worker global scope</var> to <var title="">name</var>.</li>
1.9 ihickson 1647:
1.185 ihickson 1648: <li><p><span>Create a new <code>MessagePort</code> object</span>
1.81 ihickson 1649: owned by <var title="">worker global scope</var>. Let <var title="">inside port</var> be this new object.</li>
1.9 ihickson 1650:
1.81 ihickson 1651: <li><p><span>Entangle</span> <var title="">outside port</var> and
1652: <var title="">inside port</var>.</li>
1.9 ihickson 1653:
1.155 ihickson 1654: </ol></li>
1.28 ihickson 1655:
1.123 ihickson 1656: <li><p>Return <var title="">worker</var> and perform the remaining
1657: steps asynchronously.</li>
1.18 ihickson 1658:
1.81 ihickson 1659: <li><p>Create an event that uses the <code>MessageEvent</code>
1.118 ihickson 1660: interface, with the name <code title="event-connect">connect</code>, which does not bubble, is not
1.115 ihickson 1661: cancelable, has no default action, has a <code title="dom-MessageEvent-data">data</code> attribute whose value is
1.118 ihickson 1662: the empty string and has a <code title="dom-MessageEvent-ports">ports</code> attribute whose value
1.286 ihickson 1663: is a <span title="dfn-read-only-array">read only</span> array
1664: containing only the newly created port, and <span>queue a
1665: task</span> to dispatch the event at <var title="">worker global
1.118 ihickson 1666: scope</var>.</li>
1.26 ihickson 1667:
1668: <li>
1.46 ihickson 1669:
1.123 ihickson 1670: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1671: <var title="">worker global scope</var>'s list of <span>the
1672: worker's <code>Document</code>s</span></a> the
1673: <code>Document</code> objects in <var title="">docs</var>.</p>
1674:
1675: </li>
1676:
1677: <li>
1678:
1.192 ihickson 1679: <p>If the <span title="script's global object">global object</span>
1.124 ihickson 1680: of the <span title="concept-script">script</span> that invoked the
1681: 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
1682: worker's workers</a> of the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1.192 ihickson 1683: object that is the <span title="script's global object">global
1684: object</span> of the <span title="concept-script">script</span>
1.124 ihickson 1685: that invoked the constructor.</p>
1686:
1687: </li>
1688:
1689: <li>
1690:
1.159 ihickson 1691: <p><a href="#run-a-worker">Run a worker</a> for <var title="">scriptURL</var>,
1.193 ihickson 1692: with the <span>script's browsing context</span> of the script that
1.159 ihickson 1693: invoked the method as the <var title="">owner browsing
1.232 ihickson 1694: context</var>, with the <span>script's document</span> of the
1695: script that invoked the method as the <var title="">owner
1696: document</var>, with the <span>origin</span> of the <span>entry
1.176 ihickson 1697: script</span> as the <var title="">owner origin</var>, and with
1698: <var title="">worker global scope</var> as the global scope.</p>
1.26 ihickson 1699:
1.60 ihickson 1700: </li>
1.81 ihickson 1701:
1.155 ihickson 1702: </ol><p>This constructor must be visible when the <span>script's global
1.192 ihickson 1703: object</span> is either a <code>Window</code> object or an object
1.155 ihickson 1704: implementing the <code><a href="#workerutils">WorkerUtils</a></code> interface.<p>The <span>task source</span> for the tasks mentioned above is the
1705: <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 1706: interface <dfn id="workerutils">WorkerUtils</dfn> {
1707: void <a href="#dom-workerglobalscope-importscripts" title="dom-WorkerGlobalScope-importScripts">importScripts</a>(in DOMString... urls);
1.210 ihickson 1708: readonly attribute <a href="#workernavigator">WorkerNavigator</a> <a href="#dom-worker-navigator" title="dom-worker-navigator">navigator</a>;
1.150 ihickson 1709: };
1.184 ihickson 1710: <a href="#workerutils">WorkerUtils</a> implements <span>WindowTimers</span>;</pre><p>The DOM APIs (<code>Node</code> objects, <code>Document</code>
1.81 ihickson 1711: objects, etc) are not available to workers in this version of this
1.155 ihickson 1712: 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 1713: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, the user agent must run the
1.155 ihickson 1714: following steps:<ol><li><p>If there are no arguments, return without doing
1.81 ihickson 1715: anything. Abort these steps.</li>
1716:
1717: <li><p><span title="resolve a url">Resolve</span> each
1718: argument.</li>
1719:
1720: <li><p>If any fail, throw a <code>SYNTAX_ERR</code>
1721: exception.</li>
1722:
1.26 ihickson 1723:
1724: <li>
1.81 ihickson 1725:
1.45 ihickson 1726: <p>Attempt to <span>fetch</span> each resource identified by the
1.194 ihickson 1727: resulting <span title="absolute URL">absolute URLs</span>, from
1.256 ihickson 1728: the <span>entry script</span>'s <span>origin</span>, with the
1.281 ihickson 1729: <i>synchronous flag</i> set.</p>
1.81 ihickson 1730: </li>
1.26 ihickson 1731:
1732: <li>
1733:
1.81 ihickson 1734: <p>For each argument in turn, in the order given, starting with
1735: the first one, run these substeps:</p>
1.26 ihickson 1736:
1.155 ihickson 1737: <ol><li>
1.26 ihickson 1738:
1.81 ihickson 1739: <p>Wait for the fetching attempt for the corresponding resource
1740: to complete.</p>
1.60 ihickson 1741:
1.81 ihickson 1742: <p>If the fetching attempt failed, throw a
1743: <code>NETWORK_ERR</code> exception and abort all these
1744: steps.</p>
1.45 ihickson 1745:
1.264 ihickson 1746: <p>If the attempt succeeds, then let <var title="">source</var> be
1747: the script resource <span>decoded as UTF-8, with error
1748: handling</span>.
1749:
1750: <a href="#refsHTML">[HTML]</a>
1751:
1752: </p>
1.85 ihickson 1753:
1754: <p>Let <var title="">language</var> be JavaScript.</p>
1.61 ihickson 1755:
1.115 ihickson 1756: <p class="note">As with the worker's script, the script here is
1.81 ihickson 1757: always assumed to be JavaScript, regardless of the MIME
1.170 ihickson 1758: type.</p>
1.61 ihickson 1759:
1.81 ihickson 1760: </li>
1.26 ihickson 1761:
1.81 ihickson 1762: <li>
1.26 ihickson 1763:
1.81 ihickson 1764: <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 1765: same global object, browsing context, URL character encoding,
1766: base URL, and script group as the <span title="concept-script">script</span> that was created by the
1.115 ihickson 1767: worker's <a href="#run-a-worker">run a worker</a> algorithm.</p>
1.81 ihickson 1768:
1.115 ihickson 1769: <p>Let the newly created <span title="concept-script">script</span> run until it either
1.81 ihickson 1770: returns, fails to parse, fails to catch an exception, or gets
1.115 ihickson 1771: prematurely aborted by the "<a href="#kill-a-worker">kill a worker</a>" or
1772: "<a href="#terminate-a-worker">terminate a worker</a>" algorithms defined above.</p>
1.26 ihickson 1773:
1.199 ihickson 1774: <p>If it failed to parse, then throw an ECMAScript
1775: <code>SyntaxError</code> exception and abort all these
1776: steps. <a href="#refsECMA262">[ECMA262]</a></p>
1.63 ihickson 1777:
1.81 ihickson 1778: <p>If an exception was raised or if the script was prematurely
1779: aborted, then abort all these steps, letting the exception or
1780: aborting continue to be processed by the script that called the
1.115 ihickson 1781: <code title="dom-WorkerGlobalScope-importScripts"><a href="#dom-workerglobalscope-importscripts">importScripts()</a></code>
1.81 ihickson 1782: method.</p>
1783:
1.115 ihickson 1784: <p>If the "<a href="#kill-a-worker">kill a worker</a>" or "<a href="#terminate-a-worker">terminate a
1.81 ihickson 1785: worker</a>" algorithms abort the script then abort all these
1786: steps.</p>
1787:
1788: </li>
1789:
1.155 ihickson 1790: </ol></li>
1.152 ihickson 1791:
1.210 ihickson 1792: </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 1793: of the <code><a href="#workerutils">WorkerUtils</a></code> interface must return an instance of
1.210 ihickson 1794: the <code><a href="#workernavigator">WorkerNavigator</a></code> interface, which represents the
1795: identity and state of the user agent (the client):<pre class="idl">interface <dfn id="workernavigator">WorkerNavigator</dfn> {};
1796: <a href="#workernavigator">WorkerNavigator</a> implements <span>NavigatorID</span>;
1797: <a href="#workernavigator">WorkerNavigator</a> implements <span>NavigatorOnLine</span>;</pre><p>Objects implementing the <code><a href="#workernavigator">WorkerNavigator</a></code> interface
1798: also implement the <code>NavigatorID</code> and
1799: <code>NavigatorOnLine</code> interfaces.
1.205 ihickson 1800:
1.226 ihickson 1801: <a href="#refsHTML">[HTML]</a>
1.205 ihickson 1802:
1.210 ihickson 1803: <p>This <code><a href="#workernavigator">WorkerNavigator</a></code> interface must not exist if the
1804: interface's <span>relevant namespace object</span> is a
1.272 ihickson 1805: <code>Window</code> object. <a href="#refsWEBIDL">[WEBIDL]</a><h3 id="interface-objects-and-constructors"><span class="secno">5.3 </span>Interface objects and constructors</h3><p>There must be no interface objects and constructors available in
1.192 ihickson 1806: the global scope of scripts whose <span>script's global
1807: object</span> is a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object except for
1.155 ihickson 1808: the following:<ul><li><p><code>XMLHttpRequest</code> and all interface objects and
1.81 ihickson 1809: constructors defined by the XMLHttpRequest specifications, except
1810: that the <span>document response entity body</span> must always be
1.160 ihickson 1811: null. The <span><code>XMLHttpRequest</code> base URL</span> is the
1812: <span>script's base URL</span>; the
1813: <span><code>XMLHttpRequest</code> origin</span> is the script's
1814: <span>origin</span>. <a href="#refsXHR">[XHR]</a></li>
1.81 ihickson 1815:
1.205 ihickson 1816: <li><p>The interface objects and constructors defined by this
1817: specification.</li>
1.119 ihickson 1818:
1.205 ihickson 1819: <li><p>Constructors defined by specifications that explicitly say
1820: that they should be visible when the <span>script's global
1821: object</span> is a <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>, a
1822: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>, or an object implementing the
1823: <code><a href="#workerutils">WorkerUtils</a></code> interface; the interfaces of any objects
1824: with such constructors; and the interfaces of any objects made
1825: accessible through APIs exposed by those constructors or made
1826: accessible through interfaces to be implemented by any objects that
1827: are themselves accessible to scripts whose <span>script's global
1828: object</span> implements the <code><a href="#workerutils">WorkerUtils</a></code>
1829: interface.</li>
1830:
1831: </ul><p class="note">These requirements do not override the requirements
1832: defined by the Web IDL specification, in particular concerning the
1.272 ihickson 1833: visibility of interfaces annotated with the <code title="">[NoInterfaceObject]</code> extended attribute.<h3 id="worker-locations"><span class="secno">5.4 </span>Worker locations</h3><pre class="idl">interface <dfn id="workerlocation">WorkerLocation</dfn> {
1.263 ihickson 1834: // <span>URL decomposition IDL attributes</span>
1.115 ihickson 1835: readonly attribute DOMString <a href="#dom-workerlocation-href" title="dom-WorkerLocation-href">href</a>;
1836: readonly attribute DOMString <a href="#dom-workerlocation-protocol" title="dom-WorkerLocation-protocol">protocol</a>;
1837: readonly attribute DOMString <a href="#dom-workerlocation-host" title="dom-WorkerLocation-host">host</a>;
1838: readonly attribute DOMString <a href="#dom-workerlocation-hostname" title="dom-WorkerLocation-hostname">hostname</a>;
1839: readonly attribute DOMString <a href="#dom-workerlocation-port" title="dom-WorkerLocation-port">port</a>;
1840: readonly attribute DOMString <a href="#dom-workerlocation-pathname" title="dom-WorkerLocation-pathname">pathname</a>;
1841: readonly attribute DOMString <a href="#dom-workerlocation-search" title="dom-WorkerLocation-search">search</a>;
1842: readonly attribute DOMString <a href="#dom-workerlocation-hash" title="dom-WorkerLocation-hash">hash</a>;
1.155 ihickson 1843: };</pre><p>A <code><a href="#workerlocation">WorkerLocation</a></code> object represents an <span>absolute
1844: URL</span> set at its creation.<p>The <dfn id="dom-workerlocation-href" title="dom-WorkerLocation-href"><code>href</code></dfn>
1.81 ihickson 1845: attribute must return the <span>absolute URL</span> that the object
1.155 ihickson 1846: represents.<p>The <code><a href="#workerlocation">WorkerLocation</a></code> interface also has the complement
1.163 ihickson 1847: of <span>URL decomposition IDL attributes</span>, <dfn id="dom-workerlocation-protocol" title="dom-WorkerLocation-protocol"><code>protocol</code></dfn>,
1.115 ihickson 1848: <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>,
1849: <dfn id="dom-workerlocation-pathname" title="dom-WorkerLocation-pathname"><code>pathname</code></dfn>,
1850: <dfn id="dom-workerlocation-search" title="dom-WorkerLocation-search"><code>search</code></dfn>,
1.263 ihickson 1851: and <dfn id="dom-workerlocation-hash" title="dom-WorkerLocation-hash"><code>hash</code></dfn>.
1852: These must follow the rules given for <span>URL decomposition IDL
1853: attributes</span>, with the <span title="concept-uda-input">input</span> being the <span>absolute
1854: URL</span> that the object represents (same as the <code title="dom-WorkerLocation-href"><a href="#dom-workerlocation-href">href</a></code> attribute), and the
1855: <span title="concept-uda-setter">common setter action</span> being a
1856: no-op, since the attributes are defined to be readonly.
1.205 ihickson 1857:
1.226 ihickson 1858: <a href="#refsHTML">[HTML]</a>
1.205 ihickson 1859:
1.209 ihickson 1860: <p>The <code><a href="#workerlocation">WorkerLocation</a></code> interface must not exist if the
1861: interface's <span>relevant namespace object</span> is a
1.281 ihickson 1862: <code>Window</code> object. <a href="#refsWEBIDL">[WEBIDL]</a><h2 class="no-num" id="references">References</h2><p>All references are normative unless marked "Non-normative".</p><dl><dt id="refsDOMCORE">[DOMCORE]</dt>
1.276 ihickson 1863: <dd><cite><a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html">Web DOM Core</a></cite>, A. van Kesteren. W3C.</dd>
1.153 ihickson 1864:
1.152 ihickson 1865: <dt id="refsDOMEVENTS">[DOMEVENTS]</dt>
1.281 ihickson 1866: <dd><cite><a href="http://dev.w3.org/2006/webapi/DOM-Level-3-Events/html/DOM3-Events.html">Document
1.152 ihickson 1867: Object Model (DOM) Level 3 Events Specification</a></cite>,
1.226 ihickson 1868: D. Schepers. W3C.</dd>
1.152 ihickson 1869:
1870: <dt id="refsECMA262">[ECMA262]</dt>
1871: <dd><cite><a href="http://www.ecma-international.org/publications/standards/Ecma-262.htm">ECMAScript
1.226 ihickson 1872: Language Specification</a></cite>. ECMA.</dd>
1.152 ihickson 1873:
1.226 ihickson 1874: <dt id="refsHTML">[HTML]</dt>
1875: <dd><cite><a href="http://www.whatwg.org/specs/web-apps/current-work/">HTML</a></cite>,
1876: I. Hickson. WHATWG.</dd>
1.152 ihickson 1877:
1.154 ihickson 1878: <dt id="refsRFC2119">[RFC2119]</dt>
1.265 ihickson 1879: <dd><cite><a href="http://tools.ietf.org/html/rfc2119">Key words for use in
1.226 ihickson 1880: RFCs to Indicate Requirement Levels</a></cite>, S. Bradner. IETF.</dd>
1.154 ihickson 1881:
1882: <dt id="refsWEBIDL">[WEBIDL]</dt>
1.281 ihickson 1883: <dd><cite><a href="http://dev.w3.org/2006/webapi/WebIDL/">Web
1.226 ihickson 1884: IDL</a></cite>, C. McCormack. W3C.</dd>
1.154 ihickson 1885:
1.152 ihickson 1886: <dt id="refsXHR">[XHR]</dt>
1.281 ihickson 1887: <dd><cite><a href="http://dev.w3.org/2006/webapi/XMLHttpRequest-2/"><code>XMLHttpRequest</code></a></cite>,
1.226 ihickson 1888: A. van Kesteren. W3C.</dd>
1.152 ihickson 1889:
1.221 ihickson 1890: </dl><h2 class="no-num" id="acknowledgements">Acknowledgements</h2><!-- ACKS --><p>Thanks to
1.81 ihickson 1891:
1892: Aaron Boodman,
1.155 ihickson 1893: Алексей Проскуряков (Alexey Proskuryakov),
1.81 ihickson 1894: Anne van Kesteren,
1895: Ben Turner,
1896: Dmitry Titov,
1.96 ihickson 1897: Drew Wilson,
1.97 ihickson 1898: Jeremy Orlow,
1.81 ihickson 1899: Jonas Sicking,
1900: Justin James,
1901: Kevin Hakanson,
1902: Maciej Stachowiak,
1903: Michael Nordman,
1904: Mike Smith,
1905:
1906: and
1907:
1908: Philip Taylor
1909:
1.155 ihickson 1910: for their useful and substantial comments.<p>Huge thanks to the whole Gears team, who pioneered this
1.81 ihickson 1911: technology and whose experience has been a huge influence on this
1.155 ihickson 1912: specification.
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