Annotation of html5/workers/Overview.html, revision 1.321
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">
1.82 ihickson 2: pre { margin-left: 2em; white-space: pre-wrap; }
3: h2 { margin: 3em 0 1em 0; }
4: h3 { margin: 2.5em 0 1em 0; }
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1.300 ihickson 20: i, em { font-style: italic; }
1.82 ihickson 21: dt dfn { font-style: italic; }
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1.89 ihickson 25: @media screen { code { color: orangered; } code :link, code :visited { color: inherit; } }
1.82 ihickson 26: var sub { vertical-align: bottom; font-size: smaller; position: relative; top: 0.1em; }
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1.180 ihickson 30: table tbody th { text-align: left; }
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33:
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1.305 ihickson 42: img.extra, p.overview { float: right; }
1.304 ihickson 43: pre.idl { border: solid thin; background: #EEEEEE; color: black; padding: 0.5em 1em; position: relative; }
1.82 ihickson 44: pre.idl :link, pre.idl :visited { color: inherit; background: transparent; }
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1.82 ihickson 46: pre.css { border: solid thin; background: #FFFFEE; color: black; padding: 0.5em 1em; }
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1.231 ihickson 48: dl.domintro { color: green; margin: 2em 0 2em 2em; padding: 0.5em 1em; border: none; background: #DDFFDD; }
1.82 ihickson 49: hr + dl.domintro, div.impl + dl.domintro { margin-top: 2.5em; margin-bottom: 1.5em; }
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1.310 ihickson 53: dl.domintro:before { display: table; margin: -1em -0.5em -0.5em auto; width: auto; content: 'This box is non-normative. Implementation requirements are given below this box.'; color: black; font-style: italic; border: solid 2px; background: white; padding: 0 0.25em; }
1.82 ihickson 54: dl.switch { padding-left: 2em; }
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1.121 ihickson 57: dl.triple { padding: 0 0 0 1em; }
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1.82 ihickson 61: .diff-old { text-decoration: line-through; color: silver; background: transparent; }
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64:
65: h2 { page-break-before: always; }
1.139 ihickson 66: h1, h2, h3, h4, h5, h6 { page-break-after: avoid; }
1.82 ihickson 67: h1 + h2, hr + h2.no-toc { page-break-before: auto; }
68:
1.267 ihickson 69: p > span:not([title=""]):not([class="XXX"]):not([class="impl"]):not([class="note"]),
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1.82 ihickson 71:
72: div.head { margin: 0 0 1em; padding: 1em 0 0 0; }
73: div.head p { margin: 0; }
74: div.head h1 { margin: 0; }
75: div.head .logo { float: right; margin: 0 1em; }
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77: div.head dl { margin: 1em 0; }
1.212 ihickson 78: div.head p.copyright, div.head p.alt { font-size: x-small; font-style: oblique; margin: 0; }
1.82 ihickson 79:
80: body > .toc > li { margin-top: 1em; margin-bottom: 1em; }
81: body > .toc.brief > li { margin-top: 0.35em; margin-bottom: 0.35em; }
82: body > .toc > li > * { margin-bottom: 0.5em; }
83: body > .toc > li > * > li > * { margin-bottom: 0.25em; }
84: .toc, .toc li { list-style: none; }
85:
86: .brief { margin-top: 1em; margin-bottom: 1em; line-height: 1.1; }
87: .brief li { margin: 0; padding: 0; }
88: .brief li p { margin: 0; padding: 0; }
89:
1.137 ihickson 90: .category-list { margin-top: -0.75em; margin-bottom: 1em; line-height: 1.5; }
91: .category-list::before { content: '\21D2\A0'; font-size: 1.2em; font-weight: 900; }
92: .category-list li { display: inline; }
93: .category-list li:not(:last-child)::after { content: ', '; }
94: .category-list li > span, .category-list li > a { text-transform: lowercase; }
95: .category-list li * { text-transform: none; } /* don't affect <code> nested in <a> */
96:
1.82 ihickson 97: .XXX { color: #E50000; background: white; border: solid red; padding: 0.5em; margin: 1em 0; }
98: .XXX > :first-child { margin-top: 0; }
99: p .XXX { line-height: 3em; }
1.158 ihickson 100: .annotation { border: solid thin black; background: #0C479D; color: white; position: relative; margin: 8px 0 20px 0; }
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1.82 ihickson 105: .note { color: green; background: transparent; font-family: sans-serif; }
106: .warning { color: red; background: transparent; }
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1.300 ihickson 108: .note em, .warning em, .note i, .warning i { font-style: normal; }
1.82 ihickson 109: p.note, div.note { padding: 0.5em 2em; }
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117: .bookkeeping:before { display: block; content: 'Bookkeeping details'; font-weight: bolder; font-style: italic; }
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119: .bookkeeping p { margin: 0.5em 2em; display: list-item; list-style: square; }
1.262 ihickson 120: .bookkeeping dt { margin: 0.5em 2em 0; }
121: .bookkeeping dd { margin: 0 3em 0.5em; }
1.82 ihickson 122:
123: h4 { position: relative; z-index: 3; }
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1.88 ihickson 126: background: #EEEEFF;
1.82 ihickson 127: color: black;
128: margin: 0 0 1em 0.15em;
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1.88 ihickson 130: border-left: solid #9999FF 0.25em;
1.82 ihickson 131: position: relative;
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1.88 ihickson 141: background: #EEEEFF;
1.82 ihickson 142: content: ' ';
143: border-style: none none solid solid;
1.88 ihickson 144: border-color: #9999FF;
1.82 ihickson 145: border-width: 0.25em;
146: }
147:
1.156 ihickson 148: .example { display: block; color: #222222; background: #FCFCFC; border-left: double; margin-left: 2em; padding-left: 1em; }
149: td > .example:only-child { margin: 0 0 0 0.1em; }
1.82 ihickson 150:
1.131 ihickson 151: ul.domTree, ul.domTree ul { padding: 0 0 0 1em; margin: 0; }
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163: ul.domTree .t10 code { color: teal; }
164:
1.225 ihickson 165: body.dfnEnabled dfn { cursor: pointer; }
166: .dfnPanel {
167: display: inline;
168: position: absolute;
169: z-index: 10;
170: height: auto;
171: width: auto;
172: padding: 0.5em 0.75em;
173: font: small sans-serif, Droid Sans Fallback;
174: background: #DDDDDD;
175: color: black;
176: border: outset 0.2em;
177: }
178: .dfnPanel * { margin: 0; padding: 0; font: inherit; text-indent: 0; }
179: .dfnPanel :link, .dfnPanel :visited { color: black; }
180: .dfnPanel p { font-weight: bolder; }
181: .dfnPanel * + p { margin-top: 0.25em; }
182: .dfnPanel li { list-style-position: inside; }
183:
1.207 ihickson 184: #configUI { position: absolute; z-index: 20; top: 10em; right: 1em; width: 11em; font-size: small; }
185: #configUI p { margin: 0.5em 0; padding: 0.3em; background: #EEEEEE; color: black; border: inset thin; }
186: #configUI p label { display: block; }
187: #configUI #updateUI, #configUI .loginUI { text-align: center; }
188: #configUI input[type=button] { display: block; margin: auto; }
1.260 ihickson 189:
1.268 ihickson 190: fieldset { margin: 1em; padding: 0.5em 1em; }
191: fieldset > legend + * { margin-top: 0; }
1.266 ihickson 192: fieldset > :last-child { margin-bottom: 0; }
1.268 ihickson 193: fieldset p { margin: 0.5em 0; }
1.266 ihickson 194:
1.271 ihickson 195: </style><link href="http://www.w3.org/StyleSheets/TR/W3C-ED" rel="stylesheet" type="text/css"><script type="text/javascript">
196: function getCookie(name) {
197: var params = location.search.substr(1).split("&");
198: for (var index = 0; index < params.length; index++) {
199: if (params[index] == name)
200: return "1";
201: var data = params[index].split("=");
202: if (data[0] == name)
203: return unescape(data[1]);
204: }
205: var cookies = document.cookie.split("; ");
206: for (var index = 0; index < cookies.length; index++) {
207: var data = cookies[index].split("=");
208: if (data[0] == name)
209: return unescape(data[1]);
210: }
211: return null;
212: }
1.283 ihickson 213: </script><div class="head" id="head">
1.115 ihickson 214: <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 215:
1.54 ihickson 216: <h1>Web Workers</h1>
1.281 ihickson 217:
1.321 ! ihickson 218: <h2 class="no-num no-toc" id="editor-s-draft-28-january-2012">Editor's Draft 28 January 2012</h2>
1.218 ihickson 219: <dl><dt>Latest Published Version:</dt>
1.115 ihickson 220: <dd><a href="http://www.w3.org/TR/workers/">http://www.w3.org/TR/workers/</a></dd>
1.109 ihickson 221: <dt>Latest Editor's Draft:</dt>
1.260 ihickson 222: <dd><a class="latest-link" href="http://dev.w3.org/html5/workers/">http://dev.w3.org/html5/workers/</a></dd>
1.284 ihickson 223:
1.318 ihickson 224:
1.2 ihickson 225: <dt>Previous Versions:</dt>
1.279 ihickson 226: <dd><a href="http://www.w3.org/TR/2011/WD-workers-20110310/">http://www.w3.org/TR/2011/WD-workers-20110310/</a></dd>
227: <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 228: <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 229: <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 230: <!-- :ZZZ -->
1.271 ihickson 231: <dt>Editor:</dt>
1.115 ihickson 232: <dd><a href="mailto:ian@hixie.ch">Ian Hickson</a>, Google, Inc.</dd>
1.155 ihickson 233: </dl><p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a>
1.285 ihickson 234: © 2011 <a href="http://www.w3.org/"><abbr title="World Wide
1.155 ihickson 235: Web Consortium">W3C</abbr></a><sup>®</sup> (<a href="http://www.csail.mit.edu/"><abbr title="Massachusetts
1.297 ihickson 236: Institute of Technology">MIT</abbr></a>, <a href="http://www.ercim.eu/"><abbr title="European Research
1.115 ihickson 237: Consortium for Informatics and Mathematics">ERCIM</abbr></a>, <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C
238: <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
239: <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
240: and <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document
1.81 ihickson 241: use</a> rules apply.</p>
1.201 ihickson 242:
1.254 ihickson 243:
1.252 ihickson 244: <!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
1.255 ihickson 245: <p class="alt">The bulk of the text of this specification is also
1.254 ihickson 246: 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
247: reuse of the specification text.</p>
1.252 ihickson 248: <!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
249:
1.254 ihickson 250:
1.155 ihickson 251: </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 252: authors to spawn background workers running scripts in parallel to
253: their main page. This allows for thread-like operation with
1.281 ihickson 254: 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 255: time of its publication. Other documents may supersede this
1.297 ihickson 256: document. A list of current W3C publications and the
257:
258: most recently formally published <!-- DO NOT CHANGE THIS BACK TO THE STANDARD BOILERPLATE, AS IT IS INACCURATE -->
259:
260: revision of this technical report can be found in the <a href="http://www.w3.org/TR/">W3C technical reports index</a> at
261: http://www.w3.org/TR/.</em></p><p>If you wish to make comments regarding this document in a manner
1.271 ihickson 262: 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
263: public bug database</a>. If you do not have an account then you can
264: enter feedback using this form:<form action="http://www.whatwg.org/specs/web-apps/current-work/file-spam.cgi" method="post">
265: <fieldset><legend>Feedback Comments</legend>
266: <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
267: indicating the title of the section for which you are submitting
268: feedback, quoting the text that's wrong today if appropriate. If
269: you're suggesting a new feature, it's really important to say
270: <em>what</em> the problem you're trying to solve is. That's more
271: important than the solution, in fact.</label></p>
272: <p><textarea cols="79" id="feedbackBox" name="text" rows="10"></textarea></p>
273: <p class="note">Please don't use section numbers as these tend to
274: change rapidly and make your feedback harder to understand.</p>
275: <script type="text/javascript">
1.287 ihickson 276: function checkFeedbackForm(form) {
277: if (form.elements.text.value.match(/^ *</)) {
278: alert('Please don\'t start your feedback with an angle bracket, instead explain what topic your feedback is about first.');
279: return true;
280: } else if (form.elements.text.value.match(/ [^ ]+ [^ ]+ [^ ]+ [^ ]+ /)) {
281: if (form.elements.text.value.match(/^Please enter your feedback, carefully/)) {
282: alert('Please enter your feedback, explaining what is wrong, and without repeating the instructions. Thanks!');
283: return true;
284: } else if (form.elements.text.value.match(/ [^ ]+ [^ ]+ [^ ]+ [^ ]+ /)) {
285: form.action = "http://www.whatwg.org/specs/web-apps/current-work/file-bug.cgi";
286: return true;
287: } else {
288: alert('Please include significantly more detail about exactly what problem you are trying to solve.');
289: return false;
290: }
291: }
292: }
1.271 ihickson 293: </script><p>
1.277 ihickson 294: <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 295: </p>
296: </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>,
297: <a href="http://lists.w3.org/Archives/Public/public-webapps/">archives</a>),
1.115 ihickson 298: or <a href="mailto:whatwg@whatwg.org">whatwg@whatwg.org</a> (<a href="http://lists.whatwg.org/listinfo.cgi/whatwg-whatwg.org">subscribe</a>,
299: <a href="http://lists.whatwg.org/pipermail/whatwg-whatwg.org/">archives</a>).
1.281 ihickson 300: All feedback is welcome.</p><p>Implementors should be aware that this specification is not
1.81 ihickson 301: stable. <strong>Implementors who are not taking part in the
302: discussions are likely to find the specification changing out from
303: under them in incompatible ways.</strong> Vendors interested in
304: implementing this specification before it eventually reaches the
305: Candidate Recommendation stage should join the aforementioned
1.271 ihickson 306: mailing lists and take part in the discussions.<div id="multipage-common">
1.281 ihickson 307: </div><p>The latest
1.271 ihickson 308: stable version of the editor's draft of this specification is always
309: available on <a href="http://dev.w3.org/html5/workers/">the W3C CVS server</a>
310: and in the <a href="http://svn.whatwg.org/webapps/">WHATWG
311: Subversion repository</a>. The <a href="http://www.whatwg.org/specs/web-apps/current-work/complete.html">latest
312: editor's working copy</a> (which may contain unfinished text in the
313: process of being prepared) contains the latest draft text of this
314: 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
315: FAQ</a>.<p>Notifications of changes to this specification are sent along
316: with notifications of changes to related specifications using the
317: following mechanisms:<dl><dt>E-mail notifications of changes</dt>
318: <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>
319: <dt>Browsable version-control record of all changes:</dt>
320: <dd>CVSWeb interface with side-by-side diffs: <a href="http://dev.w3.org/cvsweb/html5/">http://dev.w3.org/cvsweb/html5/</a></dd>
321: <dd>Annotated summary with unified diffs: <a href="http://html5.org/tools/web-apps-tracker">http://html5.org/tools/web-apps-tracker</a></dd>
322: <dd>Raw Subversion interface: <code>svn checkout http://svn.whatwg.org/webapps/</code></dd>
323: </dl><p>The W3C <a href="http://www.w3.org/2008/webapps/">Web Applications
1.81 ihickson 324: Working Group</a> is the W3C working group responsible for this
325: specification's progress along the W3C Recommendation track.
1.321 ! ihickson 326: This specification is the 28 January 2012 Editor's Draft.
1.281 ihickson 327: </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 328: 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 329: any patent disclosures</a> made in connection with the deliverables
330: of the group; that page also includes instructions for disclosing a
331: patent. An individual who has actual knowledge of a patent which the
1.115 ihickson 332: individual believes contains <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential
333: 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 334: 6 of the W3C Patent Policy</a>.<h2 class="no-num no-toc" id="contents">Table of Contents</h2>
1.318 ihickson 335:
1.115 ihickson 336: <ol class="toc">
337: <li><a href="#introduction"><span class="secno">1 </span>Introduction</a>
1.81 ihickson 338: <ol>
1.115 ihickson 339: <li><a href="#scope"><span class="secno">1.1 </span>Scope</a></li>
1.303 ihickson 340: <li><a href="#examples"><span class="secno">1.2 </span>Examples</a>
1.81 ihickson 341: <ol>
1.115 ihickson 342: <li><a href="#a-background-number-crunching-worker"><span class="secno">1.2.1 </span>A background number-crunching worker</a></li>
343: <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>
344: <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 345: <li><a href="#shared-workers-introduction"><span class="secno">1.2.4 </span>Shared workers introduction</a></li>
346: <li><a href="#shared-state-using-a-shared-worker"><span class="secno">1.2.5 </span>Shared state using a shared worker</a></li>
1.303 ihickson 347: <li><a href="#delegation"><span class="secno">1.2.6 </span>Delegation</a></ol></li>
348: <li><a href="#tutorials"><span class="secno">1.3 </span>Tutorials</a>
349: <ol>
350: <li><a href="#creating-a-dedicated-worker"><span class="secno">1.3.1 </span>Creating a dedicated worker</a></li>
351: <li><a href="#communicating-with-a-dedicated-worker"><span class="secno">1.3.2 </span>Communicating with a dedicated worker</a></li>
352: <li><a href="#shared-workers"><span class="secno">1.3.3 </span>Shared workers</a></ol></ol></li>
1.148 ihickson 353: <li><a href="#conformance-requirements"><span class="secno">2 </span>Conformance requirements</a>
1.82 ihickson 354: <ol>
1.148 ihickson 355: <li><a href="#dependencies"><span class="secno">2.1 </span>Dependencies</a></ol></li>
356: <li><a href="#terminology"><span class="secno">3 </span>Terminology</a></li>
357: <li><a href="#infrastructure"><span class="secno">4 </span>Infrastructure</a>
358: <ol>
1.301 ihickson 359: <li><a href="#dependencies-0"><span class="secno">4.1 </span>Dependencies</a></li>
360: <li><a href="#the-global-scope"><span class="secno">4.2 </span>The global scope</a>
1.81 ihickson 361: <ol>
1.316 ihickson 362: <li><a href="#the-workerglobalscope-common-interface"><span class="secno">4.2.1 </span>The <code>WorkerGlobalScope</code> common interface</a></li>
1.301 ihickson 363: <li><a href="#dedicated-workers-and-the-dedicatedworkerglobalscope-interface"><span class="secno">4.2.2 </span>Dedicated workers and the <code>DedicatedWorkerGlobalScope</code> interface</a></li>
364: <li><a href="#shared-workers-and-the-sharedworkerglobalscope-interface"><span class="secno">4.2.3 </span>Shared workers and the <code>SharedWorkerGlobalScope</code> interface</a></ol></li>
365: <li><a href="#origins-of-workers"><span class="secno">4.3 </span>Origins of workers</a></li>
366: <li><a href="#the-event-loop"><span class="secno">4.4 </span>The event loop</a></li>
367: <li><a href="#the-worker-s-lifetime"><span class="secno">4.5 </span>The worker's lifetime</a></li>
368: <li><a href="#processing-model"><span class="secno">4.6 </span>Processing model</a></li>
369: <li><a href="#runtime-script-errors"><span class="secno">4.7 </span>Runtime script errors</a></li>
370: <li><a href="#creating-workers"><span class="secno">4.8 </span>Creating workers</a>
1.81 ihickson 371: <ol>
1.301 ihickson 372: <li><a href="#the-abstractworker-abstract-interface"><span class="secno">4.8.1 </span>The <code>AbstractWorker</code> abstract interface</a></li>
373: <li><a href="#dedicated-workers-and-the-worker-interface"><span class="secno">4.8.2 </span>Dedicated workers and the <code>Worker</code> interface</a></li>
374: <li><a href="#shared-workers-and-the-sharedworker-interface"><span class="secno">4.8.3 </span>Shared workers and the <code>SharedWorker</code> interface</a></ol></ol></li>
1.148 ihickson 375: <li><a href="#apis-available-to-workers"><span class="secno">5 </span>APIs available to workers</a>
1.81 ihickson 376: <ol>
1.148 ihickson 377: <li><a href="#importing-scripts-and-libraries"><span class="secno">5.1 </span>Importing scripts and libraries</a></li>
1.210 ihickson 378: <li><a href="#the-workernavigator-object"><span class="secno">5.2 </span>The <code>WorkerNavigator</code> object</a></li>
1.272 ihickson 379: <li><a href="#interface-objects-and-constructors"><span class="secno">5.3 </span>Interface objects and constructors</a></li>
380: <li><a href="#worker-locations"><span class="secno">5.4 </span>Worker locations</a></ol></li>
1.115 ihickson 381: <li><a class="no-num" href="#references">References</a></li>
382: <li><a class="no-num" href="#acknowledgements">Acknowledgements</a></ol>
1.281 ihickson 383: <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 384: background independently of any user interface scripts.<p>This allows for long-running scripts that are not interrupted by
1.81 ihickson 385: scripts that respond to clicks or other user interactions, and
386: allows long tasks to be executed without yielding to keep the page
1.155 ihickson 387: responsive.<p>Workers (as these background scripts are called herein) are
1.81 ihickson 388: relatively heavy-weight, and are not intended to be used in large
389: numbers. For example, it would be inappropriate to launch one worker
390: for each pixel of a four megapixel image. The examples below show
1.155 ihickson 391: some appropriate uses of workers.<p>Generally, workers are expected to be long-lived, have a high
1.303 ihickson 392: start-up performance cost, and a high per-instance memory cost.<h3 id="examples"><span class="secno">1.2 </span>Examples</h3><p><i>This section is non-normative.</i><p>There are a variety of uses that workers can be put to. The
1.155 ihickson 393: 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
394: expensive task without interrupting the user interface.<p>In this example, the main document spawns a worker to
395: (naïvely) compute prime numbers, and progressively displays the
396: most recently found prime number.<p>The main page is as follows:<pre><!DOCTYPE HTML>
1.81 ihickson 397: <html>
398: <head>
399: <title>Worker example: One-core computation</title>
400: </head>
401: <body>
402: <p>The highest prime number discovered so far is: <output id="result"></output></p>
403: <script>
1.50 ihickson 404: var worker = new Worker('worker.js');
405: worker.onmessage = function (event) {
1.54 ihickson 406: document.getElementById('result').textContent = event.data;
1.29 ihickson 407: };
1.81 ihickson 408: </script>
409: </body>
1.155 ihickson 410: </html></pre><p>The <code title="dom-Worker"><a href="#dom-worker">Worker()</a></code> constructor call
1.115 ihickson 411: creates a worker and returns a <code><a href="#worker">Worker</a></code> object
1.81 ihickson 412: representing that worker, which is used to communicate with the
1.177 ihickson 413: 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 414: search: while (true) {
415: n += 1;
416: for (var i = 2; i <= Math.sqrt(n); i += 1)
417: if (n % i == 0)
418: continue search;
419: // found a prime!
1.50 ihickson 420: postMessage(n);
1.155 ihickson 421: }</pre><p>The bulk of this code is simply an unoptimized search for a prime
1.295 ihickson 422: number. The <code title="dom-DedicatedWorkerGlobalScope-postMessage"><a href="#dom-dedicatedworkerglobalscope-postmessage">postMessage()</a></code>
423: method is used to send a message back to the page when a prime is
424: 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 425: task is to listen for notifications from the server, and, when
426: appropriate, either add or remove data from the client-side
1.155 ihickson 427: database.<p>Since no communication occurs between the worker and the main
428: page, the main page can start the worker by just doing:<pre><script>
1.50 ihickson 429: new Worker('worker.js');
1.155 ihickson 430: </script></pre><p>The worker itself is as follows:<pre>var server = new WebSocket('ws://whatwg.org/database');
1.42 ihickson 431: var database = openDatabase('demobase', '1.0', 'Demo Database', 10240);
1.31 ihickson 432: server.onmessage = function (event) {
433: // data is in the format "command key value"
1.54 ihickson 434: var data = event.data.split(' ');
1.31 ihickson 435: switch (data[0]) {
436: case '+':
437: database.transaction(function(tx) {
438: tx.executeSql('INSERT INTO pairs (key, value) VALUES (?, ?)', data[1], data[2]);
439: });
440: case '-':
441: database.transaction(function(tx) {
442: tx.executeSql('DELETE FROM pairs WHERE key=? AND value=?', data[1], data[2]);
443: });
444: }
1.155 ihickson 445: };</pre><p>This connects to the server using the <code>WebSocket</code>
1.81 ihickson 446: mechanism and opens the local database (which, we presume, has been
447: created earlier). The worker then just listens for messages from the
448: server and acts on them as appropriate, forever (or until the main
1.155 ihickson 449: page is closed).<p><a href="http://www.whatwg.org/demos/workers/database-updater/page.html">View
1.81 ihickson 450: this example online</a>. (This example will not actually function,
451: since the server does not actually exist and the database is not
1.155 ihickson 452: 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 453: fetching stock updates for at regular intervals, and one for
1.155 ihickson 454: fetching performing search queries that the user requests.<p>The main page is as follows:<pre><!DOCTYPE HTML>
1.81 ihickson 455: <html>
456: <head>
457: <title>Worker example: Stock ticker</title>
458: <script>
1.33 ihickson 459: // TICKER
460: var symbol = 'GOOG'; // default symbol to watch
1.50 ihickson 461: var ticker = new Worker('ticker.js');
1.33 ihickson 462:
463: // SEARCHER
1.50 ihickson 464: var searcher = new Worker('searcher.js');
1.33 ihickson 465: function search(query) {
1.50 ihickson 466: searcher.postMessage(query);
1.33 ihickson 467: }
468:
469: // SYMBOL SELECTION UI
470: function select(newSymbol) {
471: symbol = newSymbol;
1.50 ihickson 472: ticker.postMessage(symbol);
1.33 ihickson 473: }
1.81 ihickson 474: </script>
475: </head>
1.122 ihickson 476: <body onload="search('')">
1.81 ihickson 477: <p><output id="symbol"></output> <output id="value"></output></p>
478: <script>
1.50 ihickson 479: ticker.onmessage = function (event) {
1.54 ihickson 480: var data = event.data.split(' ');
1.33 ihickson 481: document.getElementById('symbol').textContent = data[0];
482: document.getElementById('value').textContent = data[1];
483: };
1.50 ihickson 484: ticker.postMessage(symbol);
1.81 ihickson 485: </script>
1.122 ihickson 486: <p><label>Search: <input type="text" autofocus oninput="search(this.value)"></label></p>
1.81 ihickson 487: <ul id="results"></ul>
488: <script>
1.50 ihickson 489: searcher.onmessage = function (event) {
1.54 ihickson 490: var data = event.data.split(' ');
1.33 ihickson 491: var results = document.getElementById('results');
492: while (results.hasChildNodes()) // clear previous results
493: results.removeChild(results.firstChild);
494: for (var i = 0; i < data.length; i += 1) {
495: // add a list item with a button for each result
496: var li = document.createElement('li');
497: var button = document.createElement('button');
498: button.value = data[i];
499: button.type = 'button';
500: button.onclick = function () { select(this.value); };
501: button.textContent = data[i];
502: li.appendChild(button);
503: results.appendChild(li);
504: }
505: };
1.81 ihickson 506: </script>
507: <p>(The data in this example is not real. Try searching for "Google" or "Apple".)</p>
508: </body>
1.155 ihickson 509: </html></pre><p>The two workers use a common library for performing the actual
510: network calls. This library is as follows:<pre>function get(url) {
1.50 ihickson 511: try {
512: var xhr = new XMLHttpRequest();
513: xhr.open('GET', url, false);
514: xhr.send();
515: return xhr.responseText;
516: } catch (e) {
517: return ''; // turn all errors into empty results
518: }
1.155 ihickson 519: }</pre><p>The stock updater worker is as follows:<pre>importScripts('io.js');
1.33 ihickson 520: var timer;
521: var symbol;
522: function update() {
1.50 ihickson 523: postMessage(symbol + ' ' + get('stock.cgi?' + symbol));
1.33 ihickson 524: timer = setTimeout(update, 10000);
525: }
1.50 ihickson 526: onmessage = function (event) {
1.33 ihickson 527: if (timer)
528: clearTimeout(timer);
1.54 ihickson 529: symbol = event.data;
1.33 ihickson 530: update();
1.155 ihickson 531: };</pre><p>The search query worker is as follows:<pre>importScripts('io.js');
1.50 ihickson 532: onmessage = function (event) {
1.54 ihickson 533: postMessage(get('search.cgi?' + event.data));
1.238 ihickson 534: };</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
535: example. Shared workers use slightly different APIs, since each
536: worker can have multiple connections.<p>This first example shows how you connect to a worker and how a
537: worker can send a message back to the page when it connects to
1.239 ihickson 538: it. Received messages are displayed in a log.<p>Here is the HTML page:<pre><!DOCTYPE HTML>
539: <title>Shared workers: demo 1</title>
540: <pre id="log">Log:</pre>
541: <script>
542: var worker = new SharedWorker('test.js');
543: var log = document.getElementById('log');
544: worker.port.onmessage = function(e) { // note: not worker.onmessage!
545: log.textContent += '\n' + e.data;
546: }
547: </script>
548: </pre><p>Here is the JavaScript worker:<pre>onconnect = function(e) {
549: var port = e.ports[0];
550: port.postMessage('Hello World!');
551: }
1.259 ihickson 552: </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 553: first, messages are received using <code title="">addEventListener()</code> instead of an <span title="event
554: handler IDL attributes">event handler IDL attribute</span>, and
555: second, a message is sent <em>to</em> the worker, causing the worker
556: to send another message in return. Received messages are again
1.239 ihickson 557: displayed in a log.<p>Here is the HTML page:<pre><!DOCTYPE HTML>
1.240 ihickson 558: <title>Shared workers: demo 2</title>
1.239 ihickson 559: <pre id="log">Log:</pre>
560: <script>
561: var worker = new SharedWorker('test.js');
562: var log = document.getElementById('log');
1.240 ihickson 563: worker.port.addEventListener('message', function(e) {
1.239 ihickson 564: log.textContent += '\n' + e.data;
1.240 ihickson 565: }, false);
566: worker.port.start(); // note: need this when using addEventListener
567: worker.port.postMessage('ping');
1.239 ihickson 568: </script>
569: </pre><p>Here is the JavaScript worker:<pre>onconnect = function(e) {
570: var port = e.ports[0];
571: port.postMessage('Hello World!');
1.240 ihickson 572: port.onmessage = function(e) {
573: port.postMessage('pong'); // not e.ports[0].postMessage!
574: // e.target.postMessage('pong'); would work also
575: }
1.239 ihickson 576: }
1.259 ihickson 577: </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 578: connect to the same worker; in this case, the second page is merely
579: in an <code>iframe</code> on the first page, but the same principle
580: would apply to an entirely separate page in a separate
1.239 ihickson 581: <span>top-level browsing context</span>.<p>Here is the outer HTML page:<pre><!DOCTYPE HTML>
582: <title>Shared workers: demo 3</title>
583: <pre id="log">Log:</pre>
584: <script>
585: var worker = new SharedWorker('test.js');
586: var log = document.getElementById('log');
587: worker.port.addEventListener('message', function(e) {
588: log.textContent += '\n' + e.data;
589: }, false);
590: worker.port.start();
591: worker.port.postMessage('ping');
592: </script>
593: <iframe src="inner.html"></iframe>
594: </pre><p>Here is the inner HTML page:<pre><!DOCTYPE HTML>
595: <title>Shared workers: demo 3 inner frame</title>
596: <pre id=log>Inner log:</pre>
597: <script>
598: var worker = new SharedWorker('test.js');
599: var log = document.getElementById('log');
600: worker.port.onmessage = function(e) {
601: log.textContent += '\n' + e.data;
602: }
603: </script>
604: </pre><p>Here is the JavaScript worker:<pre>var count = 0;
605: onconnect = function(e) {
606: count += 1;
607: var port = e.ports[0];
608: port.postMessage('Hello World! You are connection #' + count);
609: port.onmessage = function(e) {
610: port.postMessage('pong');
611: }
612: }
1.259 ihickson 613: </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 614: are all viewing the same map. All the windows share the same map
615: information, with a single worker coordinating all the viewers. Each
616: viewer can move around independently, but if they set any data on
1.155 ihickson 617: the map, all the viewers are updated.<p>The main page isn't interesting, it merely provides a way to open
618: the viewers:<pre><!DOCTYPE HTML>
1.81 ihickson 619: <html>
620: <head>
621: <title>Workers example: Multiviewer</title>
622: <script>
1.36 ihickson 623: function openViewer() {
624: window.open('viewer.html');
625: }
1.81 ihickson 626: </script>
627: </head>
628: <body>
629: <p><button type=button onclick="openViewer()">Open a new
630: viewer</button></p>
631: <p>Each viewer opens in a new window. You can have as many viewers
632: as you like, they all view the same data.</p>
633: </body>
1.155 ihickson 634: </html></pre><p>The viewer is more involved:<pre><!DOCTYPE HTML>
1.81 ihickson 635: <html>
636: <head>
637: <title>Workers example: Multiviewer viewer</title>
638: <script>
1.50 ihickson 639: var worker = new SharedWorker('worker.js', 'core');
1.36 ihickson 640:
641: // CONFIGURATION
642: function configure(event) {
1.54 ihickson 643: if (event.data.substr(0, 4) != 'cfg ') return;
644: var name = event.data.substr(4).split(' ', 1);
1.36 ihickson 645: // update display to mention our name is name
646: document.getElementsByTagName('h1')[0].textContent += ' ' + name;
647: // no longer need this listener
1.43 ihickson 648: worker.port.removeEventListener('message', configure, false);
1.36 ihickson 649: }
1.53 ihickson 650: worker.port.addEventListener('message', configure, false);
1.36 ihickson 651:
652: // MAP
653: function paintMap(event) {
1.54 ihickson 654: if (event.data.substr(0, 4) != 'map ') return;
655: var data = event.data.substr(4).split(',');
1.36 ihickson 656: // display tiles data[0] .. data[8]
657: var canvas = document.getElementById('map');
658: var context = canvas.getContext('2d');
659: for (var y = 0; y < 3; y += 1) {
660: for (var x = 0; x < 3; x += 1) {
661: var tile = data[y * 3 + x];
662: if (tile == '0')
663: context.fillStyle = 'green';
664: else
665: context.fillStyle = 'maroon';
666: fillRect(x * 50, y * 50, 50, 50);
667: }
668: }
669: }
1.53 ihickson 670: worker.port.addEventListener('message', paintMap, false);
1.36 ihickson 671:
672: // PUBLIC CHAT
673: function updatePublicChat(event) {
1.54 ihickson 674: if (event.data.substr(0, 4) != 'txt ') return;
675: var name = event.data.substr(4).split(' ', 1);
676: var message = event.data.substr(4 + length(name) + 1);
1.81 ihickson 677: // display "<name> message" in public chat
1.36 ihickson 678: var dialog = document.getElementById('public');
679: var dt = document.createElement('dt');
680: dt.textContent = name;
681: dialog.appendChild(dt);
682: var dd = document.createElement('dd');
683: dd.textContent = message;
684: dialog.appendChild(dd);
685: }
1.53 ihickson 686: worker.port.addEventListener('message', updatePublicChat, false);
1.36 ihickson 687:
688: // PRIVATE CHAT
689: function startPrivateChat(event) {
1.54 ihickson 690: if (event.data.substr(0, 4) != 'msg ') return;
691: var name = event.data.substr(4).split(' ', 1);
1.84 ihickson 692: var port = event.ports[0];
1.36 ihickson 693: // display a private chat UI
694: var ul = document.getElementById('private');
695: var li = document.createElement('li');
696: var h3 = document.createElement('h3');
697: h3.textContent = 'Private chat with ' + name;
698: li.appendChild(h3);
699: var dialog = document.createElement('dialog');
700: var addMessage = function(name, message) {
701: var dt = document.createElement('dt');
702: dt.textContent = name;
703: dialog.appendChild(dt);
704: var dd = document.createElement('dd');
705: dd.textContent = message;
706: dialog.appendChild(dd);
707: };
708: port.onmessage = function (event) {
1.54 ihickson 709: addMessage(name, event.data);
1.36 ihickson 710: };
711: li.appendChild(dialog);
712: var form = document.createElement('form');
713: var p = document.createElement('p');
714: var input = document.createElement('input');
715: input.size = 50;
716: p.appendChild(input);
717: p.appendChild(document.createTextNode(' '));
718: var button = document.createElement('button');
719: button.textContent = 'Post';
720: p.appendChild(button);
721: form.onsubmit = function () {
722: port.postMessage(input.value);
723: addMessage('me', input.value);
724: input.value = '';
725: return false;
726: };
727: form.appendChild(p);
728: li.appendChild(form);
729: }
1.53 ihickson 730: worker.port.addEventListener('message', startPrivateChat, false);
1.188 ihickson 731:
732: worker.port.start();
1.81 ihickson 733: </script>
734: </head>
735: <body>
736: <h1>Viewer</h1>
737: <h2>Map</h2>
738: <p><canvas id="map" height=150 width=150></canvas></p>
739: <p>
740: <button type=button onclick="worker.port.postMessage('mov left')">Left</button>
741: <button type=button onclick="worker.port.postMessage('mov up')">Up</button>
742: <button type=button onclick="worker.port.postMessage('mov down')">Down</button>
743: <button type=button onclick="worker.port.postMessage('mov right')">Right</button>
744: <button type=button onclick="worker.port.postMessage('set 0')">Set 0</button>
745: <button type=button onclick="worker.port.postMessage('set 1')">Set 1</button>
746: </p>
747: <h2>Public Chat</h2>
748: <dialog id="public"></dialog>
749: <form onsubmit="worker.port.postMessage('txt ' + message.value); message.value = ''; return false;">
750: <p>
751: <input type="text" name="message" size="50">
752: <button>Post</button>
753: </p>
754: </form>
755: <h2>Private Chat</h2>
756: <ul id="private"></ul>
757: </body>
758: </html>
1.155 ihickson 759: </pre><p>There are several key things worth noting about the way the
760: viewer is written.<p><strong>Multiple listeners</strong>. Instead of a single message
1.81 ihickson 761: processing function, the code here attaches multiple event
762: listeners, each one performing a quick check to see if it is
763: relevant for the message. In this example it doesn't make much
764: difference, but if multiple authors wanted to collaborate using a
765: single port to communicate with a worker, it would allow for
766: independent code instead of changes having to all be made to a
1.155 ihickson 767: single event handling function.<p>Registering event listeners in this way also allows you to
1.81 ihickson 768: unregister specific listeners when you are done with them, as is
769: done with the <code title="">configure()</code> method in this
1.155 ihickson 770: example.<p>Finally, the worker:<pre>
771: var nextName = 0;
1.36 ihickson 772: function getNextName() {
773: // this could use more friendly names
774: // but for now just return a number
775: return nextName++;
776: }
777:
778: var map = [
779: [0, 0, 0, 0, 0, 0, 0],
780: [1, 1, 0, 1, 0, 1, 1],
781: [0, 1, 0, 1, 0, 0, 0],
782: [0, 1, 0, 1, 0, 1, 1],
783: [0, 0, 0, 1, 0, 0, 0],
784: [1, 0, 0, 1, 1, 1, 1],
785: [1, 1, 0, 1, 1, 0, 1],
786: ];
787:
788: function wrapX(x) {
789: if (x < 0) return wrapX(x + map[0].length);
1.81 ihickson 790: if (x >= map[0].length) return wrapX(x - map[0].length);
1.36 ihickson 791: return x;
792: }
793:
794: function wrapY(y) {
795: if (y < 0) return wrapY(y + map.length);
1.81 ihickson 796: if (y >= map[0].length) return wrapY(y - map.length);
1.36 ihickson 797: return y;
798: }
799:
1.50 ihickson 800: function sendMapData(callback) {
1.36 ihickson 801: var data = '';
802: for (var y = viewer.y-1; y <= viewer.y+1; y += 1) {
803: for (var x = viewer.x-1; x <= viewer.x+1; x += 1) {
804: if (data != '')
805: data += ',';
806: data += map[y][x];
807: }
808: }
1.50 ihickson 809: callback('map ' + data);
1.36 ihickson 810: }
811:
812: var viewers = {};
813: onconnect = function (event) {
1.84 ihickson 814: event.ports[0]._name = getNextName();
815: event.ports[0]._data = { port: event.port, x: 0, y: 0, };
816: viewers[event.ports[0]._name] = event.port._data;
817: event.ports[0].postMessage('cfg ' + name);
818: event.ports[0].onmessage = getMessage;
819: sendMapData(event.ports[0].postMessage);
1.36 ihickson 820: };
821:
822: function getMessage(event) {
1.54 ihickson 823: switch (event.data.substr(0, 4)) {
1.36 ihickson 824: case 'mov ':
1.54 ihickson 825: var direction = event.data.substr(4);
1.36 ihickson 826: var dx = 0;
827: var dy = 0;
828: switch (direction) {
829: case 'up': dy = -1; break;
830: case 'down': dy = 1; break;
831: case 'left': dx = -1; break;
832: case 'right': dx = 1; break;
833: }
834: event.target._data.x = wrapX(event.target._data.x + dx);
835: event.target._data.y = wrapY(event.target._data.y + dy);
1.50 ihickson 836: sendMapData(event.target.postMessage);
1.36 ihickson 837: break;
838: case 'set ':
1.54 ihickson 839: var value = event.data.substr(4);
1.36 ihickson 840: map[event.target._data.y][event.target._data.x] = value;
841: for (var viewer in viewers)
1.50 ihickson 842: sendMapData(viewers[viewer].port.postMessage);
1.36 ihickson 843: break;
844: case 'txt ':
845: var name = event.target._name;
1.54 ihickson 846: var message = event.data.substr(4);
1.36 ihickson 847: for (var viewer in viewers)
848: viewers[viewer].port.postMessage('txt ' + name + ' ' + message);
849: break;
850: case 'msg ':
851: var party1 = event._data;
1.54 ihickson 852: var party2 = viewers[event.data.substr(4).split(' ', 1)];
1.36 ihickson 853: if (party2) {
854: var channel = new MessageChannel();
1.84 ihickson 855: party1.port.postMessage('msg ' + party2.name, [channel.port1]);
856: party2.port.postMessage('msg ' + party1.name, [channel.port2]);
1.36 ihickson 857: }
858: break;
859: }
1.155 ihickson 860: }</pre><p><strong>Connecting to multiple pages</strong>. The script uses
1.115 ihickson 861: the <code title="handler-SharedWorkerGlobalScope-onconnect"><a href="#handler-sharedworkerglobalscope-onconnect">onconnect</a></code>
1.155 ihickson 862: event listener to listen for multiple connections.<p><strong>Direct channels</strong>. When the worker receives a
1.81 ihickson 863: "msg" message from one viewer naming another viewer, it sets up a
864: direct connection between the two, so that the two viewers can
865: communicate directly without the worker having to proxy all the
1.238 ihickson 866: 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 867: performance is to split computationally expensive tasks amongst
868: multiple workers. In this example, a computationally expensive task
869: that is to be performed for every number from 1 to 10,000,000 is
1.155 ihickson 870: farmed out to ten subworkers.<p>The main page is as follows, it just reports the result:<pre><!DOCTYPE HTML>
1.81 ihickson 871: <html>
872: <head>
1.203 ihickson 873: <title>Worker example: Multicore computation</title>
1.81 ihickson 874: </head>
875: <body>
1.203 ihickson 876: <p>Result: <output id="result"></output></p>
1.81 ihickson 877: <script>
1.50 ihickson 878: var worker = new Worker('worker.js');
879: worker.onmessage = function (event) {
1.54 ihickson 880: document.getElementById('result').textContent = event.data;
1.40 ihickson 881: };
1.81 ihickson 882: </script>
883: </body>
1.155 ihickson 884: </html></pre><p>The worker itself is as follows:<pre>// settings
1.40 ihickson 885: var num_workers = 10;
886: var items_per_worker = 1000000;
887:
888: // start the workers
889: var result = 0;
890: var pending_workers = num_workers;
891: for (var i = 0; i < num_workers; i += 1) {
1.50 ihickson 892: var worker = new Worker('core.js');
893: worker.postMessage(i * items_per_worker);
894: worker.postMessage((i+1) * items_per_worker);
895: worker.onmessage = storeResult;
1.40 ihickson 896: }
897:
898: // handle the results
899: function storeResult(event) {
1.54 ihickson 900: result += 1*event.data;
1.40 ihickson 901: pending_workers -= 1;
902: if (pending_workers <= 0)
1.50 ihickson 903: postMessage(result); // finished!
1.155 ihickson 904: }</pre><p>It consists of a loop to start the subworkers, and then a handler
905: that waits for all the subworkers to respond.<p>The subworkers are implemented as follows:<pre>var start;
1.41 ihickson 906: onmessage = getStart;
1.40 ihickson 907: function getStart(event) {
1.54 ihickson 908: start = 1*event.data;
1.40 ihickson 909: onmessage = getEnd;
910: }
911:
912: var end;
913: function getEnd(event) {
1.54 ihickson 914: end = 1*event.data;
1.40 ihickson 915: onmessage = null;
1.66 ihickson 916: work();
1.40 ihickson 917: }
918:
1.66 ihickson 919: function work() {
1.40 ihickson 920: var result = 0;
921: for (var i = start; i < end; i += 1) {
922: // perform some complex calculation here
923: result += 1;
924: }
1.50 ihickson 925: postMessage(result);
926: close();
1.155 ihickson 927: }</pre><p>They receive two numbers in two events, perform the computation
1.81 ihickson 928: for the range of numbers thus specified, and then report the result
1.303 ihickson 929: back to the parent.<p><a href="http://www.whatwg.org/demos/workers/multicore/page.html">View this example online</a>.</p><h3 id="tutorials"><span class="secno">1.3 </span>Tutorials</h3><h4 id="creating-a-dedicated-worker"><span class="secno">1.3.1 </span>Creating a dedicated worker</h4><p><i>This section is non-normative.</i><p>Creating a worker requires a URL to a JavaScript file. The <code title="dom-Worker"><a href="#dom-worker">Worker()</a></code> constructor is invoked with the
930: URL to that file as its only argument; a worker is then created and
931: returned:<pre>var worker = new Worker('helper.js');</pre><h4 id="communicating-with-a-dedicated-worker"><span class="secno">1.3.2 </span>Communicating with a dedicated worker</h4><p><i>This section is non-normative.</i><p>Dedicated workers use <code><a href="#messageport">MessagePort</a></code> objects behind the
932: scenes, and thus support all the same features, such as sending
933: structured data, transferring binary data, and transferring other
934: ports.<p>To receive messages from a dedicated worker, use the <code title="handler-worker-onmessage"><a href="#handler-worker-onmessage">onmessage</a></code> <span title="event
935: handler IDL attributes">event handler IDL attribute</span> on the
936: <code><a href="#worker">Worker</a></code> object:<pre>worker.onmessage = function (event) { ... };</pre><p>You can also use the <code title="dom-EventTarget-addEventListener">addEventListener()</code> method.<p class="note">The implicit <code><a href="#messageport">MessagePort</a></code> used by
937: dedicated workers has its <span>port message queue</span> implicitly
938: enabled when it is created, so there is no equivanet to the
939: <code><a href="#messageport">MessagePort</a></code> interface's <code title="dom-MessagePort-start">start()</code> method on the
940: <code><a href="#worker">Worker</a></code> interface.<p>To <em>send</em> data to a worker, use the <code title="dom-Worker-postMessage"><a href="#dom-worker-postmessage">postMessage()</a></code> method.
941: Structured data can be sent over this communication channel. To send
942: <code>ArrayBuffer</code> objects efficiently (by transferring them
943: rather than cloning them), list them in an array in the second
944: argument.<pre>worker.postMessage({
945: operation: 'find-edges',
946: input: buffer, // an ArrayBuffer object
947: threshold: 0.6,
948: }, [buffer]);</pre><p>To receive a message inside the worker, the <code title="handler-DedicatedWorkerGlobalScope-onmessage"><a href="#handler-dedicatedworkerglobalscope-onmessage">onmessage</a></code>
949: <span title="event handler IDL attributes">event handler IDL
950: attribute</span> is used.<pre>onmessage = function (event) { ... };</pre><p>You can again also use the <code title="dom-EventTarget-addEventListener">addEventListener()</code>
951: method.<p>In either case, the data is provided in the event object's <code title="dom-MessageEvent-data">data</code> attribute.<p>To send messages back, you again use <code title="dom-DedicatedWorkerGlobalScope-postMessage"><a href="#dom-dedicatedworkerglobalscope-postmessage">postMessage()</a></code>.
952: It supports the structured data in the same manner.<pre>postMessage(event.data.input, [event.data.input]); // transfer the buffer back</pre><h4 id="shared-workers"><span class="secno">1.3.3 </span>Shared workers</h4><p><i>This section is non-normative.</i><p>Shared workers are identified in one of two ways: either by the
953: URL of the script used to create it, or by explicit name. When
954: created by name, the URL used by the first page to create the worker
955: with that name is the URL of the script that will be used for that
956: worker. This allows multiple applications on a domain to all use a
957: single shared worker to provide a common service, without the
958: applications having to keep track of a common URL for the script
959: used to provide the service.<p class="note">In either case, shared workers are scoped by
960: <span>origin</span>. Two different sites using the same names will
961: not collide.<p>Creating shared workers is done using the <code title="dom-SharedWorker"><a href="#dom-sharedworker">SharedWorker()</a></code> constructor. This
962: constructor takes the URL to the script to use for its first
963: argument, and the name of the worker, if any, as the second
964: argument.<pre>var worker = new SharedWorker('service.js');</pre><p>Communicating with shared workers is done with explicit
965: <code><a href="#messageport">MessagePort</a></code> objects. The object returned by the <code title="dom-SharedWorker"><a href="#dom-sharedworker">SharedWorker()</a></code> constructor holds a
966: reference to the port on its <code title="dom-SharedWorker-port"><a href="#dom-sharedworker-port">port</a></code> attribute.<pre>worker.port.onmessage = function (event) { ... };
967: worker.port.postMessage('some message');
1.311 ihickson 968: worker.port.postMessage({ foo: 'structured', bar: ['data', 'also', 'possible']});</pre><p>Inside the shared worker, new clients of the worker are announced
1.303 ihickson 969: using the <code title="event-connect">connect</code> event. The port
970: for the new client is given by the event object's <code title="dom-messageevent-ports">ports</code> array as its first (and
971: only) value.<pre>onconnect = function (event) {
972: var newPort = event.ports[0];
973: // set up a listener
974: newPort.onmessage = function (event) { ... };
975: // send a message back to the port
976: newPort.postMessage('ready!'); // can also send structured data, of course
977: };</pre><h2 id="conformance-requirements"><span class="secno">2 </span>Conformance requirements</h2><p>All diagrams, examples, and notes in this specification are
1.81 ihickson 978: non-normative, as are all sections explicitly marked non-normative.
1.281 ihickson 979: Everything else in this specification is normative.<p>The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
1.81 ihickson 980: "OPTIONAL" in the normative parts of this document are to be
981: interpreted as described in RFC2119. For readability, these words do
1.155 ihickson 982: 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 983: (such as "strip any leading space characters" or "return false and
984: abort these steps") are to be interpreted with the meaning of the
985: key word ("must", "should", "may", etc) used in introducing the
1.155 ihickson 986: algorithm.<p>Some conformance requirements are phrased as requirements on
1.81 ihickson 987: attributes, methods or objects. Such requirements are to be
1.155 ihickson 988: interpreted as requirements on user agents.<p>Conformance requirements phrased as algorithms or specific steps
1.81 ihickson 989: may be implemented in any manner, so long as the end result is
990: equivalent. (In particular, the algorithms defined in this
991: specification are intended to be easy to follow, and not intended to
1.155 ihickson 992: be performant.)<p>The only conformance class defined by this specification is user
993: agents.<p>User agents may impose implementation-specific limits on
1.81 ihickson 994: otherwise unconstrained inputs, e.g. to prevent denial of service
995: attacks, to guard against running out of memory, or to work around
1.229 ihickson 996: platform-specific limitations.<p>When support for a feature is disabled (e.g. as an emergency
997: measure to mitigate a security problem, or to aid in development, or
998: for performance reasons), user agents must act as if they had no
999: support for the feature whatsoever, and as if the feature was not
1000: mentioned in this specification. For example, if a particular
1001: feature is accessed via an attribute in a Web IDL interface, the
1002: attribute itself would be omitted from the objects that implement
1003: that interface — leaving the attribute on the object but
1004: 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 1005: specifications.<dl><dt>HTML</dt>
1.49 ihickson 1006:
1.81 ihickson 1007: <dd>
1.49 ihickson 1008:
1.226 ihickson 1009: <p>Many fundamental concepts from HTML are used by this
1010: specification. <a href="#refsHTML">[HTML]</a></p>
1.49 ihickson 1011:
1.81 ihickson 1012: </dd>
1.1 ihickson 1013:
1.81 ihickson 1014: <dt>WebIDL</dt>
1.1 ihickson 1015:
1016: <dd>
1017:
1.81 ihickson 1018: <p>The IDL blocks in this specification use the semantics of the
1.153 ihickson 1019: WebIDL specification. <a href="#refsWEBIDL">[WEBIDL]</a></p>
1.1 ihickson 1020:
1.81 ihickson 1021: </dd>
1.1 ihickson 1022:
1.155 ihickson 1023: </dl><h2 id="terminology"><span class="secno">3 </span>Terminology</h2><p>The construction "a <code title="">Foo</code> object", where
1.81 ihickson 1024: <code title="">Foo</code> is actually an interface, is sometimes
1025: used instead of the more accurate "an object implementing the
1.155 ihickson 1026: interface <code title="">Foo</code>".<p>The term DOM is used to refer to the API set made available to
1.81 ihickson 1027: scripts in Web applications, and does not necessarily imply the
1028: existence of an actual <code>Document</code> object or of any other
1029: <code>Node</code> objects as defined in the DOM Core
1.171 ihickson 1030: specifications. <a href="#refsDOMCORE">[DOMCORE]</a><p>An IDL attribute is said to be <em>getting</em> when its value is
1.81 ihickson 1031: being retrieved (e.g. by author script), and is said to be
1.155 ihickson 1032: <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 1033: the official term ECMAScript, since the term JavaScript is more
1.155 ihickson 1034: 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 1035: workers. Dedicated workers, once created, and are linked to their
1036: creator; but message ports can be used to communicate from a
1037: dedicated worker to multiple other browsing contexts or
1038: workers. Shared workers, on the other hand, are named, and once
1039: created any script running in the same <span>origin</span> can
1.301 ihickson 1040: obtain a reference to that worker and communicate with it.<h3 id="dependencies-0"><span class="secno">4.1 </span>Dependencies</h3><p>The <dfn id="messageport"><code>MessagePort</code></dfn> interface is defined in
1.316 ihickson 1041: the HTML specification. <a href="#refsHTML">[HTML]</a><h3 id="the-global-scope"><span class="secno">4.2 </span>The global scope</h3><p>The global scope is the "inside" of a worker.<h4 id="the-workerglobalscope-common-interface"><span class="secno">4.2.1 </span>The <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> common interface</h4><pre class="idl">[NoInterfaceObject]
1042: interface <dfn id="workerglobalscope">WorkerGlobalScope</dfn> : <span>EventTarget</span> {
1.115 ihickson 1043: readonly attribute <a href="#workerglobalscope">WorkerGlobalScope</a> <a href="#dom-workerglobalscope-self" title="dom-WorkerGlobalScope-self">self</a>;
1044: readonly attribute <a href="#workerlocation">WorkerLocation</a> <a href="#dom-workerglobalscope-location" title="dom-WorkerGlobalScope-location">location</a>;
1045:
1046: void <a href="#dom-workerglobalscope-close" title="dom-WorkerGlobalScope-close">close</a>();
1.308 ihickson 1047: [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-workerglobalscope-onerror" title="handler-WorkerGlobalScope-onerror">onerror</a>;
1048: [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-workerglobalscope-onoffline" title="handler-WorkerGlobalScope-onoffline">onoffline</a>;
1049: [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-workerglobalscope-ononline" title="handler-WorkerGlobalScope-ononline">ononline</a>;
1.150 ihickson 1050: };
1.302 ihickson 1051: <a href="#workerglobalscope">WorkerGlobalScope</a> implements <a href="#workerutils">WorkerUtils</a>;</pre><p>The <dfn id="dom-workerglobalscope-self" title="dom-WorkerGlobalScope-self"><code>self</code></dfn> attribute
1.155 ihickson 1052: 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 1053: attribute must return the <code><a href="#workerlocation">WorkerLocation</a></code> object created
1054: for the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object when the worker was
1.81 ihickson 1055: created. It represents the <span>absolute URL</span> of the script
1.155 ihickson 1056: 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 1057: method on a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, the user agent
1.155 ihickson 1058: must run the following steps (atomically):<ol><li><p>Discard any <span title="concept-task">tasks</span> that
1.123 ihickson 1059: have been added to the <span>event loop</span>'s <span title="task
1060: queue">task queues</span>.</p>
1061:
1.81 ihickson 1062:
1.318 ihickson 1063:
1.115 ihickson 1064: <li><p>Set the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's
1065: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.123 ihickson 1066: true. (This prevents any further tasks from being queued.)</li>
1.81 ihickson 1067:
1.177 ihickson 1068: </ol><p>The following are the <span>event handlers</span> (and their
1069: corresponding <span title="event handler event type">event handler
1070: event types</span>) that must be supported, as IDL attributes, by
1071: objects implementing the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1072: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.281 ihickson 1073: <tbody><tr><td><dfn id="handler-workerglobalscope-onerror" title="handler-WorkerGlobalScope-onerror"><code>onerror</code></dfn> <td> <code title="event-error">error</code>
1.289 ihickson 1074: <tr><td><dfn id="handler-workerglobalscope-onoffline" title="handler-WorkerGlobalScope-onoffline"><code>onoffline</code></dfn> <td> <code title="event-offline">offline</code>
1075: <tr><td><dfn id="handler-workerglobalscope-ononline" title="handler-WorkerGlobalScope-ononline"><code>ononline</code></dfn> <td> <code title="event-online">online</code>
1.316 ihickson 1076: </table><h4 id="dedicated-workers-and-the-dedicatedworkerglobalscope-interface"><span class="secno">4.2.2 </span>Dedicated workers and the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> interface</h4><pre class="idl">interface <dfn id="dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</dfn> {
1.318 ihickson 1077: void <a href="#dom-dedicatedworkerglobalscope-postmessage" title="dom-DedicatedWorkerGlobalScope-postMessage">postMessage</a>(any message, optional sequence<<span>Transferable</span>> transfer);
1078: [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-dedicatedworkerglobalscope-onmessage" title="handler-DedicatedWorkerGlobalScope-onmessage">onmessage</a>;
1.316 ihickson 1079: };
1080: <a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a> implements <a href="#workerglobalscope">WorkerGlobalScope</a>;</pre><p>The <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> interface must not
1081: exist if the interface's <span>relevant namespace object</span> is
1082: not a <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object. <a href="#refsWEBIDL">[WEBIDL]</a><p><code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> objects act as if they
1.301 ihickson 1083: had an implicit <code><a href="#messageport">MessagePort</a></code> associated with them. This
1.81 ihickson 1084: port is part of a channel that is set up when the worker is created,
1085: but it is not exposed. This object must never be garbage collected
1.155 ihickson 1086: before the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object.<p>All messages received by that port must immediately be retargeted
1.318 ihickson 1087: 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>
1088: method on
1.115 ihickson 1089: <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> objects must act as if, when
1.281 ihickson 1090: invoked, it immediately invoked the
1.81 ihickson 1091: method of the same name on the port, with the same arguments, and
1.177 ihickson 1092: returned the same return value.<p>The following are the <span>event handlers</span> (and their
1093: corresponding <span title="event handler event type">event handler
1094: event types</span>) that must be supported, as IDL attributes, by
1095: objects implementing the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
1096: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1097: <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 1098: </table><p>For the purposes of the <span>application cache</span> networking
1099: model, a dedicated worker is an extension of the <span>cache
1.316 ihickson 1100: host</span> from which it was created.<h4 id="shared-workers-and-the-sharedworkerglobalscope-interface"><span class="secno">4.2.3 </span>Shared workers and the <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> interface</h4><pre class="idl">interface <dfn id="sharedworkerglobalscope">SharedWorkerGlobalScope</dfn> : <a href="#workerglobalscope">WorkerGlobalScope</a> {
1.115 ihickson 1101: readonly attribute DOMString <a href="#dom-sharedworkerglobalscope-name" title="dom-SharedWorkerGlobalScope-name">name</a>;
1.181 ihickson 1102: readonly attribute <span>ApplicationCache</span> <span title="dom-SharedWorkerGlobalScope-applicationCache">applicationCache</span>;
1.308 ihickson 1103: [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-sharedworkerglobalscope-onconnect" title="handler-SharedWorkerGlobalScope-onconnect">onconnect</a>;
1.316 ihickson 1104: };
1.321 ! ihickson 1105: <a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a> implements <a href="#workerglobalscope">WorkerGlobalScope</a>;</pre><p>The <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> interface must not
1.316 ihickson 1106: exist if the interface's <span>relevant namespace object</span> is
1.321 ! ihickson 1107: not a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object. <a href="#refsWEBIDL">[WEBIDL]</a><p>Shared workers receive message ports through <code title="event-WorkerGlobalScope-connect">connect</code> events on
1.155 ihickson 1108: their global object for each connection.<p>The <dfn id="dom-sharedworkerglobalscope-name" title="dom-SharedWorkerGlobalScope-name"><code>name</code></dfn>
1.81 ihickson 1109: attribute must return the value it was assigned when the
1.115 ihickson 1110: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object was created by the
1111: "<a href="#run-a-worker">run a worker</a>" algorithm. Its value represents the name
1.81 ihickson 1112: that can be used to obtain a reference to the worker using the
1.177 ihickson 1113: <code><a href="#sharedworker">SharedWorker</a></code> constructor.<p>The following are the <span>event handlers</span> (and their
1114: corresponding <span title="event handler event type">event handler
1115: event types</span>) that must be supported, as IDL attributes, by
1116: objects implementing the <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1117: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1118: <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 1119: </table><p>For the purposes of the <span>application cache</span> networking
1120: model, a shared worker is its own <span>cache host</span>. The
1121: <a href="#run-a-worker">run a worker</a> algorithm takes care of associating the
1122: worker with an <span>application cache</span>.<p class="note">The <code title="dom-SharedWorkerGlobalScope-applicationCache">applicationCache</code>
1.123 ihickson 1123: attribute returns the <code>ApplicationCache</code> object for the
1.301 ihickson 1124: worker.</p><h3 id="origins-of-workers"><span class="secno">4.3 </span>Origins of workers</h3><p>Both the <span>origin</span> and <span>effective script
1.81 ihickson 1125: origin</span> of scripts running in workers are the
1126: <span>origin</span> of the <span>absolute URL</span> given in that
1.115 ihickson 1127: the worker's <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1.301 ihickson 1128: represents.<h3 id="the-event-loop"><span class="secno">4.4 </span>The event loop</h3><p>Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object has an <span>event
1.128 ihickson 1129: loop</span> distinct from those defined for <span title="unit of
1130: related similar-origin browsing contexts">units of related
1131: similar-origin browsing contexts</span>. This <span>event
1132: loop</span> has no associated <span>browsing context</span>, and its
1133: <span title="task queue">task queues</span> only have events,
1134: callbacks, and networking activity as <span title="concept-task">tasks</span>. The processing model of these
1135: <span title="event loop">event loops</span> is defined below in the
1.155 ihickson 1136: <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 1137: initially be false, but which can get set to true by the algorithms
1.155 ihickson 1138: 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 1139: true, the <span>event loop</span>'s <span title="task queue">task
1.115 ihickson 1140: queues</span> must discard any further <span title="concept-task">tasks</span> that would be added to them (tasks
1.175 ihickson 1141: already on the queue are unaffected except where otherwise
1.115 ihickson 1142: specified). Effectively, once the <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is true,
1.81 ihickson 1143: timers stop firing, notifications for all pending asynchronous
1.301 ihickson 1144: operations are dropped, etc.<h3 id="the-worker-s-lifetime"><span class="secno">4.5 </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
1145: <code><a href="#messageport">MessagePort</a></code> objects.<p>Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> <var title="">worker global
1.124 ihickson 1146: scope</var> has a list of <dfn id="the-worker-s-ports">the worker's ports</dfn>, which
1.301 ihickson 1147: consists of all the <code><a href="#messageport">MessagePort</a></code> objects that are
1.81 ihickson 1148: entangled with another port and that have one (but only one) port
1149: owned by <var title="">worker global scope</var>. This list includes
1.281 ihickson 1150: the implicit
1.301 ihickson 1151: <code><a href="#messageport">MessagePort</a></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 1152: worker's workers</dfn>. Initially this list is empty; it is
1.155 ihickson 1153: 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 1154: <dfn id="the-worker-s-documents">the worker's <code>Document</code>s</dfn>. Initially this list
1.155 ihickson 1155: 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 1156: worker's <code>Document</code>s</dfn>, the user agent must, for each
1.124 ihickson 1157: worker in the list of <a href="#the-worker-s-workers">the worker's workers</a> whose list
1158: of <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> does not contain
1159: <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 1160: documents">add <var title="">d</var> to <var title="">q</var>'s
1161: <code>WorkerGlobalScope</code> owner's list of <span>the worker's
1.281 ihickson 1162: <code>Document</code>s</span></a>.</p><p>Whenever a <code>Document</code> object is <span title="discard a
1.123 ihickson 1163: Document">discarded</span>, it must be removed from the list of
1164: <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> of each worker
1.192 ihickson 1165: whose list contains that <code>Document</code>.<p>Given a <span>script's global object</span> <var title="">o</var>
1.123 ihickson 1166: when creating or obtaining a worker, the <dfn id="list-of-relevant-document-objects-to-add">list of relevant
1167: <code>Document</code> objects to add</dfn> depends on the type of
1168: <var title="">o</var>. If <var title="">o</var> is a
1169: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object (i.e. if we are creating a
1170: nested worker), then the relevant <code>Document</code>s are the
1171: <code>Document</code>s that are in <var title="">o</var>'s own list
1172: 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
1173: <code>Document</code> is just the <code>Document</code> that is the
1.155 ihickson 1174: <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 1175: list of <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> is not
1.155 ihickson 1176: empty.<p>A worker is said to be a <dfn id="protected-worker">protected worker</dfn> if it is a
1.123 ihickson 1177: <a href="#permissible-worker">permissible worker</a> and either it has outstanding
1178: timers, database transactions, or network connections, or its list
1.124 ihickson 1179: of <a href="#the-worker-s-ports">the worker's ports</a> is not empty, or its
1.123 ihickson 1180: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> is actually a
1181: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object (i.e. the worker is a
1.155 ihickson 1182: shared worker).<p>A worker is said to be an <dfn id="active-needed-worker">active needed worker</dfn> if any
1.123 ihickson 1183: of the <code>Document</code> objects in <a href="#the-worker-s-documents">the worker's
1.155 ihickson 1184: <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 1185: not an <a href="#active-needed-worker">active needed worker</a> but it is a
1.301 ihickson 1186: <a href="#permissible-worker">permissible worker</a>.<h3 id="processing-model"><span class="secno">4.6 </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 1187: <span>URL</span> <var title="">url</var>, a <span>browsing
1188: context</span> <var title="">owner browsing context</var>, a
1189: <code>Document</code> <var title="">owner document</var>, an
1190: <span>origin</span> <var title="">owner origin</var>, and with
1191: global scope <var title="">worker global scope</var>, it must run
1192: the following steps:<ol><li>
1.81 ihickson 1193:
1.274 ihickson 1194: <p>Create a separate parallel execution environment (i.e. a
1195: separate thread or process or equivalent construct), and run the
1196: rest of these steps asynchronously in that context.</p>
1.81 ihickson 1197:
1198: </li>
1.4 ihickson 1199:
1.101 ihickson 1200: <li><p>If <var title="">worker global scope</var> is actually a
1.115 ihickson 1201: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object (i.e. the worker is a
1.101 ihickson 1202: shared worker), and there are any <span title="relevant application
1203: cache">relevant application caches</span> that are identified by a
1204: manifest URL with the <span>same origin</span> as <var title="">url</var> and that have <var title="">url</var> as one of
1.115 ihickson 1205: their entries, <em>not</em> excluding entries marked as <span title="concept-appcache-foreign">foreign</span>, then associate the
1206: <var title="">worker global scope</var> with the <span title="concept-appcache-selection">most appropriate application
1.101 ihickson 1207: cache</span> of those that match.</li>
1208:
1.4 ihickson 1209: <li>
1.52 ihickson 1210:
1.256 ihickson 1211: <p>Attempt to <span>fetch</span> the resource identified by <var title="">url</var>, from the <var title="">owner origin</var>,
1212: with the <i>synchronous flag</i> set and the <i>force same-origin
1.281 ihickson 1213: flag</i> set.</p>
1.318 ihickson 1214:
1.256 ihickson 1215: <p>If the attempt fails, then for each <code><a href="#worker">Worker</a></code> or
1216: <code><a href="#sharedworker">SharedWorker</a></code> object associated with <var title="">worker global scope</var>, <span>queue a task</span> to
1217: <span>fire a simple event</span> named <code title="event-error">error</code> at that object. Abort these
1218: steps.</p>
1.7 ihickson 1219:
1.264 ihickson 1220: <p>If the attempt succeeds, then let <var title="">source</var> be
1221: the script resource <span>decoded as UTF-8, with error
1222: handling</span>.
1223:
1224: <a href="#refsHTML">[HTML]</a>
1225:
1226: </p>
1.81 ihickson 1227:
1.68 ihickson 1228: <p>Let <var title="">language</var> be JavaScript.</p>
1.7 ihickson 1229:
1.115 ihickson 1230: <p class="note">As with <code>script</code> elements, the MIME
1.81 ihickson 1231: type of the script is ignored. Unlike with <code>script</code>
1232: elements, there is no way to override the type. It's always
1.170 ihickson 1233: assumed to be JavaScript.</p>
1.81 ihickson 1234:
1235: </li>
1.7 ihickson 1236:
1237: <li>
1.68 ihickson 1238:
1.115 ihickson 1239: <p>A new <span title="concept-script">script</span> is now
1.81 ihickson 1240: created, as follows.</p>
1241:
1242: <p>Create a new <span>script execution environment</span>
1243: set up as appropriate for the scripting language <var title="">language</var>.</p>
1.34 ihickson 1244:
1.68 ihickson 1245: <p>Parse/compile/initialize <var title="">source</var> using that
1.81 ihickson 1246: <span>script execution environment</span>, as appropriate for <var title="">language</var>, and thus obtain a <span>list of code
1247: entry-points</span>; set the <i>initial code entry-point</i> to
1248: the entry-point for any executable code to be immediately run.</p>
1249:
1250: <p>Set the <span>script's global object</span> to <var title="">worker global scope</var>.</p>
1251:
1252: <p>Set the <span>script's browsing context</span> to <var title="">owner browsing context</var>.</p>
1253:
1.232 ihickson 1254: <p>Set the <span>script's document</span> to <var title="">owner
1255: document</var>.</p>
1256:
1.83 ihickson 1257: <p>Set the <span>script's URL character encoding</span> to
1.81 ihickson 1258: UTF-8. (This is just used for encoding non-ASCII characters in the
1259: query component of URLs.)</p>
1.68 ihickson 1260:
1261: <p>Set the <span>script's base URL</span> to <var title="">url</var>.</p>
1.4 ihickson 1262:
1.81 ihickson 1263: </li>
1.4 ihickson 1264:
1265: <li>
1.81 ihickson 1266:
1267: <p><strong>Closing orphan workers</strong>: Start monitoring the
1.125 ihickson 1268: worker such that no sooner than it stops being either a
1269: <a href="#protected-worker">protected worker</a> or a <a href="#suspendable-worker">suspendable
1.123 ihickson 1270: worker</a>, and no later than it stops being a
1271: <a href="#permissible-worker">permissible worker</a>, <var title="">worker global
1272: scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is set
1.281 ihickson 1273: to true.</p>
1.81 ihickson 1274:
1275: </li>
1.9 ihickson 1276:
1277: <li>
1.7 ihickson 1278:
1.81 ihickson 1279: <p><strong>Suspending workers</strong>: Start monitoring the
1280: worker, such that whenever <var title="">worker global
1.115 ihickson 1281: scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is false
1282: and the worker is a <a href="#suspendable-worker">suspendable worker</a>, the user
1.81 ihickson 1283: agent suspends execution of script in that worker until such time
1.115 ihickson 1284: as either the <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag switches
1285: to true or the worker stops being a <a href="#suspendable-worker">suspendable
1.81 ihickson 1286: worker</a>.</p>
1.4 ihickson 1287:
1.81 ihickson 1288: </li>
1.68 ihickson 1289:
1290: <li>
1.4 ihickson 1291:
1.81 ihickson 1292: <p><span title="jump to a code entry-point">Jump</span> to the
1.115 ihickson 1293: <span title="concept-script">script</span>'s <i>initial code
1.81 ihickson 1294: entry-point</i>, and let that run until it either returns, fails
1295: to catch an exception, or gets prematurely aborted by the
1.115 ihickson 1296: "<a href="#kill-a-worker">kill a worker</a>" or "<a href="#terminate-a-worker">terminate a worker</a>"
1.81 ihickson 1297: algorithms defined below.</p>
1298:
1.4 ihickson 1299:
1.318 ihickson 1300:
1.81 ihickson 1301: </li>
1.4 ihickson 1302:
1.95 ihickson 1303: <li><p>If <var title="">worker global scope</var> is actually a
1.115 ihickson 1304: <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object (i.e. the worker is
1.126 ihickson 1305: a dedicated worker), then enable the <span>port message
1306: queue</span> of the worker's implicit port.</li>
1.95 ihickson 1307:
1.4 ihickson 1308: <li>
1.68 ihickson 1309:
1.115 ihickson 1310: <p><i title="">Event loop</i>: Wait until either there is a <span title="concept-task">task</span> in one of the <span>event
1311: 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 1312: to true.</p>
1.43 ihickson 1313:
1.81 ihickson 1314: </li>
1.4 ihickson 1315:
1316: <li>
1317:
1.81 ihickson 1318: <p>Run the oldest task on one of the <span>event loop</span>'s
1319: <span title="task queue">task queues</span>, if any. The user
1320: agent may pick any <span>task queue</span>.</p>
1321:
1.115 ihickson 1322: <p class="note">The handling of events or the execution of
1323: callbacks might get prematurely aborted by the "<a href="#kill-a-worker">kill a
1324: worker</a>" or "<a href="#terminate-a-worker">terminate a worker</a>" algorithms
1.81 ihickson 1325: defined below.</p>
1.8 ihickson 1326:
1.81 ihickson 1327: </li>
1.4 ihickson 1328:
1329: <li>
1330:
1.248 ihickson 1331: <p>If the <span>storage mutex</span> is now owned by the worker's
1332: <span>event loop</span>, release it so that it is once again
1333: free.</p>
1334:
1335: </li>
1336:
1337: <li>
1338:
1339: <p>Remove the task just run in the earlier step, if any, from its
1.81 ihickson 1340: <span>task queue</span>.</p>
1.4 ihickson 1341:
1.81 ihickson 1342: </li>
1.4 ihickson 1343:
1344: <li>
1.8 ihickson 1345:
1.81 ihickson 1346: <p>If there are any more events in the <span>event loop</span>'s
1.115 ihickson 1347: <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 1348: to false, then jump back to the step above labeled <i>event
1349: loop</i>.</p>
1.8 ihickson 1350:
1.81 ihickson 1351: </li>
1.8 ihickson 1352:
1353: <li>
1.71 ihickson 1354:
1.123 ihickson 1355: <p>Empty the <var title="">worker global scope</var>'s <span>list
1356: of active timeouts</span> and its <span>list of active
1357: intervals</span>.</p>
1.50 ihickson 1358:
1.81 ihickson 1359: </li>
1.50 ihickson 1360:
1.247 ihickson 1361: <li>
1362:
1363: <p>Disentangle all the ports in the list of <a href="#the-worker-s-ports">the worker's
1364: ports</a>.</p>
1365:
1366: </li>
1367:
1.318 ihickson 1368:
1.155 ihickson 1369: </ol><hr><p>When a user agent is to <dfn id="kill-a-worker">kill a worker</dfn> it must
1.81 ihickson 1370: run the following steps in parallel with the worker's main loop (the
1.281 ihickson 1371: "<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 1372: true.</li>
1373:
1374:
1.318 ihickson 1375:
1.115 ihickson 1376: <li><p>If there are any <span title="concept-task">tasks</span>
1.81 ihickson 1377: queued in the <span>event loop</span>'s <span title="task
1.281 ihickson 1378: queue">task queues</span>, discard them without processing them.</li>
1379:
1.81 ihickson 1380:
1.318 ihickson 1381:
1.81 ihickson 1382: <li><p>Wait a user-agent-defined amount of time.</li>
1383:
1.281 ihickson 1384: <li><p>Abort the script currently running in the worker.</li>
1.81 ihickson 1385:
1.155 ihickson 1386: </ol><p>User agents may invoke the "<a href="#kill-a-worker">kill a worker</a>"
1.81 ihickson 1387: processing model on a worker at any time, e.g. in response to user
1388: requests, in response to CPU quota management, or when a worker
1.115 ihickson 1389: stops being an <a href="#active-needed-worker">active needed worker</a> if the worker
1390: continues executing even after its <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag was
1.155 ihickson 1391: 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 1392: the following steps in parallel with the worker's main loop (the
1.155 ihickson 1393: "<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 1394: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.81 ihickson 1395: true.</li>
1396:
1.115 ihickson 1397: <li><p>If there are any <span title="concept-task">tasks</span>
1.81 ihickson 1398: queued in the <span>event loop</span>'s <span title="task
1399: queue">task queues</span>, discard them without processing
1400: them.</li>
1401:
1402: <li><p>Abort the script currently running in the worker.</li>
1403:
1.115 ihickson 1404: <li><p>If the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object is
1405: actually a <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object (i.e. the
1.81 ihickson 1406: worker is a dedicated worker), then empty the <span>port message
1407: queue</span> of the port that the worker's implicit port is
1408: entangled with.</li>
1409:
1.155 ihickson 1410: </ol><hr><p>The <span>task source</span> for the tasks mentioned above is the
1.301 ihickson 1411: <span>DOM manipulation task source</span>.<h3 id="runtime-script-errors"><span class="secno">4.7 </span>Runtime script errors</h3><p>Whenever an uncaught runtime script error occurs in one of the
1.143 ihickson 1412: worker's scripts, if the error did not occur while handling a
1413: previous script error, the user agent must <span>report the
1.314 ihickson 1414: error</span> at the <span>URL</span> of the resource that contained
1415: the script, with the line number where the error occurred, in the
1416: <span>origin</span> of the scripts running in the worker, using the
1417: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's <code title="handler-WorkerGlobalScope-onerror"><a href="#handler-workerglobalscope-onerror">onerror</a></code> attribute.
1.205 ihickson 1418:
1.226 ihickson 1419: <a href="#refsHTML">[HTML]</a>
1.205 ihickson 1420:
1421: <p>For shared workers, if the error is still <i title="concept-error-nothandled">not handled</i> afterwards, or if
1.132 ihickson 1422: the error occurred while handling a previous script error, the error
1.215 ihickson 1423: may be reported to the user.
1.205 ihickson 1424:
1.226 ihickson 1425: <a href="#refsHTML">[HTML]</a>
1.205 ihickson 1426:
1427: <p>For dedicated workers, if the error is still <i title="concept-error-nothandled">not handled</i> afterwards, or if
1.132 ihickson 1428: the error occurred while handling a previous script error, the user
1.292 ihickson 1429: agent must <span>queue a task</span> to fire an event that uses the
1430: <code><a href="#errorevent">ErrorEvent</a></code> interface, with the name <code title="event-error">error</code>, that doesn't bubble and is
1.307 ihickson 1431: 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 initialized
1.292 ihickson 1432: appropriately, at the <code><a href="#worker">Worker</a></code> object associated with the
1.307 ihickson 1433: worker. If the event is not canceled, the user agent must act as if
1434: the uncaught runtime script error had occurred in the global scope
1435: that the <code><a href="#worker">Worker</a></code> object is in, thus repeating the entire
1.292 ihickson 1436: runtime script error reporting process one level up.<p>If the implicit port connecting the worker to its
1437: <code><a href="#worker">Worker</a></code> object has been disentangled (i.e. if the parent
1438: worker has been terminated), then the user agent must act as if the
1439: <code><a href="#worker">Worker</a></code> object had no <code title="event-error">error</code> event handler and as if that
1440: worker's <code title="handler-WorkerGlobalScope-onerror"><a href="#handler-workerglobalscope-onerror">onerror</a></code> attribute
1441: was null, but must otherwise act as described above.<p class="note">Thus, error reports proagate up to the chain of
1442: dedicated workers up to the original <code>Document</code>, even if
1443: some of the workers along this chain have been terminated and
1444: garbage collected.<p>The <span>task source</span> for the task mentioned above is the
1.307 ihickson 1445: <span>DOM manipulation task source</span>.<hr><pre class="idl">[Constructor(DOMString type, optional <a href="#erroreventinit">ErrorEventInit</a> eventInitDict)]
1446: interface <dfn id="errorevent">ErrorEvent</dfn> : <span>Event</span> {
1.147 ihickson 1447: readonly attribute DOMString <a href="#dom-errorevent-message" title="dom-ErrorEvent-message">message</a>;
1448: readonly attribute DOMString <a href="#dom-errorevent-filename" title="dom-ErrorEvent-filename">filename</a>;
1.115 ihickson 1449: readonly attribute unsigned long <a href="#dom-errorevent-lineno" title="dom-ErrorEvent-lineno">lineno</a>;
1.307 ihickson 1450: };
1451:
1452: dictionary <dfn id="erroreventinit">ErrorEventInit</dfn> : <span>EventInit</span> {
1453: DOMString message;
1454: DOMString filename;
1455: unsigned long lineno;
1456: };</pre><p>The <dfn id="dom-errorevent-message" title="dom-ErrorEvent-message"><code>message</code></dfn> attribute
1457: must return the value it was initialized to. When the object is
1458: created, this attribute must be initialized to the empty string. It
1459: represents the error message.<p>The <dfn id="dom-errorevent-filename" title="dom-ErrorEvent-filename"><code>filename</code></dfn>
1460: attribute must return the value it was initialized to. When the
1461: object is created, this attribute must be initialized to the empty
1462: string. It represents the <span>absolute URL</span> of the script in
1.155 ihickson 1463: which the error originally occurred.<p>The <dfn id="dom-errorevent-lineno" title="dom-ErrorEvent-lineno"><code>lineno</code></dfn>
1.307 ihickson 1464: attribute must return the value it was initialized to. When the
1465: object is created, this attribute must be initialized to zero. It
1466: represents the line number where the error occurred in the
1.317 ihickson 1467: script.<h3 id="creating-workers"><span class="secno">4.8 </span>Creating workers</h3><h4 id="the-abstractworker-abstract-interface"><span class="secno">4.8.1 </span>The <code><a href="#abstractworker">AbstractWorker</a></code> abstract interface</h4><pre class="idl">[NoInterfaceObject]
1468: interface <dfn id="abstractworker">AbstractWorker</dfn> {
1.308 ihickson 1469: [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-abstractworker-onerror" title="handler-AbstractWorker-onerror">onerror</a>;
1.318 ihickson 1470:
1.302 ihickson 1471: };</pre><p>The following are the <span>event handlers</span> (and their
1.177 ihickson 1472: corresponding <span title="event handler event type">event handler
1473: event types</span>) that must be supported, as IDL attributes, by
1474: 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 1475: <tbody><tr><td><dfn id="handler-abstractworker-onerror" title="handler-AbstractWorker-onerror"><code>onerror</code></dfn> <td> <code title="event-error">error</code>
1.318 ihickson 1476:
1.306 ihickson 1477: </table><h4 id="dedicated-workers-and-the-worker-interface"><span class="secno">4.8.2 </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>(DOMString scriptURL)]
1.317 ihickson 1478: interface <dfn id="worker">Worker</dfn> : <span>EventTarget</span> {
1.115 ihickson 1479: void <a href="#dom-worker-terminate" title="dom-Worker-terminate">terminate</a>();
1.50 ihickson 1480:
1.318 ihickson 1481: void <a href="#dom-worker-postmessage" title="dom-Worker-postMessage">postMessage</a>(any message, optional sequence<<span>Transferable</span>> transfer);
1482: [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-worker-onmessage" title="handler-Worker-onmessage">onmessage</a>;
1.317 ihickson 1483: };
1484: <a href="#worker">Worker</a> implements <a href="#abstractworker">AbstractWorker</a>;</pre><p>The <dfn id="dom-worker-terminate" title="dom-Worker-terminate"><code>terminate()</code></dfn> method,
1.115 ihickson 1485: when invoked, must cause the "<a href="#terminate-a-worker">terminate a worker</a>"
1.81 ihickson 1486: algorithm to be run on the worker with with the object is
1.155 ihickson 1487: associated.<p><code><a href="#worker">Worker</a></code> objects act as if they had an implicit
1.301 ihickson 1488: <code><a href="#messageport">MessagePort</a></code> associated with them. This port is part of
1.81 ihickson 1489: a channel that is set up when the worker is created, but it is not
1490: exposed. This object must never be garbage collected before the
1.155 ihickson 1491: <code><a href="#worker">Worker</a></code> object.<p>All messages received by that port must immediately be retargeted
1.318 ihickson 1492: 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>
1493: method on <code><a href="#worker">Worker</a></code> objects
1.281 ihickson 1494: must act as if, when invoked, it
1.81 ihickson 1495: immediately invoked the method of the same name on the port, with
1.319 ihickson 1496: the same arguments, and returned the same return value.<div class="example">
1497:
1498: <p>The <code title="dom-Worker-postMessage"><a href="#dom-worker-postmessage">postMessage()</a></code>
1499: method's first argument can be structured data:</p>
1500:
1501: <pre>worker.postMessage({opcode: 'activate', device: 1938, parameters: [23, 102]});</pre>
1502:
1503: </div><p>The following are the <span>event handlers</span> (and their
1.177 ihickson 1504: corresponding <span title="event handler event type">event handler
1505: event types</span>) that must be supported, as IDL attributes, by
1506: 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 1507: <tbody><tr><td><dfn id="handler-worker-onmessage" title="handler-Worker-onmessage"><code>onmessage</code></dfn> <td> <code title="event-message">message</code>
1508: </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 1509: 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 1510: script</span>'s <span title="script's base URL">base URL</span>,
1511: when the method is invoked.</li>
1.9 ihickson 1512:
1.309 ihickson 1513: <li><p>If this fails, throw a <code>SyntaxError</code>
1.81 ihickson 1514: exception.</li>
1.9 ihickson 1515:
1.167 ihickson 1516: <li>
1517:
1518: <p>If the <span>origin</span> of the resulting <span>absolute
1519: URL</span> is not the <span title="same origin">same</span> as the
1.216 ihickson 1520: origin of the <span>entry script</span>, then throw a
1.309 ihickson 1521: <code>SecurityError</code> exception.</p>
1.167 ihickson 1522:
1523: <p class="note">Thus, scripts must be external files with the same
1.269 ihickson 1524: scheme as the original page: you can't load a script from a <span title="data protocol"><code title="">data:</code> URL</span> or
1525: <span title="javascript protocol"><code title="">javascript:</code> URL</span>, and an <code>http:</code>
1526: page couldn't start workers using scripts with <code>http:</code>
1527: URLs.</p>
1.167 ihickson 1528:
1529: </li>
1.9 ihickson 1530:
1.185 ihickson 1531: <li><p>Create a new <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
1532: object. Let <var title="">worker global scope</var> be this new
1533: object.</li>
1.9 ihickson 1534:
1.115 ihickson 1535: <li><p>Create a new <code><a href="#worker">Worker</a></code> object, associated with
1.81 ihickson 1536: <var title="">worker global scope</var>. Let <var title="">worker</var> be this new object.</li>
1.50 ihickson 1537:
1.301 ihickson 1538: <li><p><span>Create a new <code><a href="#messageport">MessagePort</a></code> object</span>
1.192 ihickson 1539: owned by the <span title="script's global object">global
1540: object</span> of the <span title="concept-script">script</span> that
1.185 ihickson 1541: invoked the constructor. Let this be the <var title="">outside
1.81 ihickson 1542: port</var>.</li>
1.9 ihickson 1543:
1.81 ihickson 1544: <li><p>Associate the <var title="">outside port</var> with <var title="">worker</var>.</li>
1.50 ihickson 1545:
1.301 ihickson 1546: <li><p><span>Create a new <code><a href="#messageport">MessagePort</a></code> object</span>
1.185 ihickson 1547: owned by <var title="">worker global scope</var>. Let <var title="">inside port</var> be this new object.</li>
1.50 ihickson 1548:
1.81 ihickson 1549: <li><p>Associate <var title="">inside port</var> with <var title="">worker global scope</var>.</li>
1.50 ihickson 1550:
1.81 ihickson 1551: <li><p><span>Entangle</span> <var title="">outside port</var> and
1552: <var title="">inside port</var>.</li>
1.50 ihickson 1553:
1.81 ihickson 1554: <li><p>Return <var title="">worker</var>, and run the following
1555: steps asynchronously.</li>
1.50 ihickson 1556:
1557:
1.318 ihickson 1558:
1.126 ihickson 1559: <li><p>Enable <var title="">outside port</var>'s <span>port message
1.81 ihickson 1560: queue</span>.</li>
1.50 ihickson 1561:
1562: <li>
1.51 ihickson 1563:
1.123 ihickson 1564: <p>Let <var title="">docs</var> be the <a href="#list-of-relevant-document-objects-to-add">list of relevant
1.192 ihickson 1565: <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 1566: constructor.</p>
1567:
1568: </li>
1569:
1570: <li>
1571:
1572: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1573: <var title="">worker global scope</var>'s list of <span>the
1574: worker's <code>Document</code>s</span></a> the
1575: <code>Document</code> objects in <var title="">docs</var>.</p>
1576:
1577: </li>
1578:
1579: <li>
1580:
1.192 ihickson 1581: <p>If the <span title="script's global object">global object</span>
1.124 ihickson 1582: of the <span title="concept-script">script</span> that invoked the
1583: constructor is a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object (i.e. we
1584: are creating a nested worker), add <var title="">worker global
1585: scope</var> to the list of <a href="#the-worker-s-workers">the worker's workers</a> of the
1.192 ihickson 1586: <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 1587: constructor.</p>
1588:
1589: </li>
1590:
1591: <li>
1592:
1.115 ihickson 1593: <p><a href="#run-a-worker">Run a worker</a> for the resulting <span>absolute
1.193 ihickson 1594: URL</span>, with the <span>script's browsing context</span> of the
1.81 ihickson 1595: script that invoked the method as the <var title="">owner browsing
1.232 ihickson 1596: context</var>, with the <span>script's document</span> of the
1597: script that invoked the method as the <var title="">owner
1598: document</var>, with the <span>origin</span> of the <span>entry
1.176 ihickson 1599: script</span> as the <var title="">owner origin</var>, and with
1600: <var title="">worker global scope</var> as the global scope.</p>
1.9 ihickson 1601:
1.81 ihickson 1602: </li>
1.4 ihickson 1603:
1.155 ihickson 1604: </ol><p>This constructor must be visible when the <span>script's global
1.192 ihickson 1605: object</span> is either a <code>Window</code> object or an object
1.306 ihickson 1606: implementing the <code><a href="#workerutils">WorkerUtils</a></code> interface.<h4 id="shared-workers-and-the-sharedworker-interface"><span class="secno">4.8.3 </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>(DOMString scriptURL, optional DOMString name)]
1.317 ihickson 1607: interface <dfn id="sharedworker">SharedWorker</dfn> : <span>EventTarget</span> {
1.301 ihickson 1608: readonly attribute <a href="#messageport">MessagePort</a> <a href="#dom-sharedworker-port" title="dom-SharedWorker-port">port</a>;
1.317 ihickson 1609: };
1610: <a href="#sharedworker">SharedWorker</a> implements <a href="#abstractworker">AbstractWorker</a>;</pre><p>The <dfn id="dom-sharedworker-port" title="dom-SharedWorker-port"><code>port</code></dfn>
1.81 ihickson 1611: attribute must return the value it was assigned by the object's
1.301 ihickson 1612: constructor. It represents the <code><a href="#messageport">MessagePort</a></code> for
1.155 ihickson 1613: 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 1614: constructor is invoked, the user agent must run the following
1.155 ihickson 1615: steps:<ol><li><p><span title="resolve a url">Resolve</span> the <var title="">scriptURL</var> argument.</li>
1.81 ihickson 1616:
1.309 ihickson 1617: <li><p>If this fails, throw a <code>SyntaxError</code>
1.81 ihickson 1618: exception.</li>
1619:
1.159 ihickson 1620: <li><p>Otherwise, let <var title="">scriptURL</var> be the
1621: resulting <span>absolute URL</span>.</li>
1622:
1623: <li><p>Let <var title="">name</var> be the value of the second
1.164 ihickson 1624: argument, or the empty string if the second argument was
1625: omitted.</li>
1.159 ihickson 1626:
1.167 ihickson 1627: <li>
1628:
1629: <p>If the <span>origin</span> of <var title="">scriptURL</var> is
1630: not the <span title="same origin">same</span> as the origin of the
1.309 ihickson 1631: <span>entry script</span>, then throw a <code>SecurityError</code>
1.182 ihickson 1632: exception.</p>
1.167 ihickson 1633:
1634: <p class="note">Thus, scripts must be external files with the same
1.269 ihickson 1635: scheme as the original page: you can't load a script from a <span title="data protocol"><code title="">data:</code> URL</span> or
1.313 ihickson 1636: <span title="javascript protocol"><code title="">javascript:</code> URL</span>, and an <code>http:</code>
1.269 ihickson 1637: page couldn't start workers using scripts with <code>http:</code>
1638: URLs.</p>
1.167 ihickson 1639:
1640: </li>
1.9 ihickson 1641:
1642: <li>
1643:
1.123 ihickson 1644: <p>Let <var title="">docs</var> be the <a href="#list-of-relevant-document-objects-to-add">list of relevant
1.192 ihickson 1645: <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 1646: constructor.</p>
1647:
1648: </li>
1649:
1650: <li>
1651:
1.50 ihickson 1652: <p>Execute the following substeps atomically:</p>
1.9 ihickson 1653:
1.155 ihickson 1654: <ol><li><p>Create a new <code><a href="#sharedworker">SharedWorker</a></code> object, which will
1.115 ihickson 1655: shortly be associated with a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1656: object. Let this <code><a href="#sharedworker">SharedWorker</a></code> object be <var title="">worker</var>.</li>
1.81 ihickson 1657:
1.301 ihickson 1658: <li><p><span>Create a new <code><a href="#messageport">MessagePort</a></code> object</span>
1.192 ihickson 1659: owned by the <span title="script's global object">global
1660: object</span> of the script that invoked the method. Let this be
1.123 ihickson 1661: the <var title="">outside port</var>.</li>
1.81 ihickson 1662:
1.115 ihickson 1663: <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 1664:
1.164 ihickson 1665: <li><p>Let <var title="">worker global scope</var> be
1666: null.</li>
1667:
1.312 ihickson 1668: <li>
1669:
1670: <p>If <var title="">name</var> is not the empty string and there
1671: exists a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object whose <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is
1672: false, whose <code title="dom-WorkerGlobalScope-name">name</code> attribute is
1673: exactly equal to <var title="">name</var>, and whose <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1674: represents an <span>absolute URL</span> with the <span>same
1675: origin</span> as <var title="">scriptURL</var>, then let <var title="">worker global scope</var> be that
1676: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object.</p>
1677:
1678: <p>Otherwise, if <var title="">name</var> is the empty string
1679: and there exists a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object
1680: whose <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a>
1681: flag is false, whose <code title="dom-WorkerGlobalScope-name">name</code> attribute is the
1682: empty string, and whose <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1683: represents an <span>absolute URL</span> that is exactly equal to
1684: <var title="">scriptURL</var>, then let <var title="">worker
1685: global scope</var> be that <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1686: object.</p>
1687:
1688: </li>
1689:
1690: <li>
1691:
1692: <p>If <var title="">worker global scope</var> is not null, but
1693: the user agent has been configured to disallow communication
1694: between the <span title="concept-script">script</span> that
1695: invoked the constructor and the worker represented by the <var title="">worker global scope</var>, then set <var title="">worker global scope</var> to null.</p>
1696:
1697: <p class="note">For example, a user agent could have a
1698: development mode that isolates a particular <span>top-level
1699: browsing context</span> from all other pages, and scripts in
1700: that development mode could be blocked from connecting to shared
1701: workers running in the normal browser mode.</p>
1702:
1703: </li>
1.164 ihickson 1704:
1.9 ihickson 1705: <li>
1706:
1.164 ihickson 1707: <p>If <var title="">worker global scope</var> is not null, then
1708: run these steps:</p>
1.81 ihickson 1709:
1.164 ihickson 1710: <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 1711: attribute represents an <span>absolute URL</span> that is not
1.159 ihickson 1712: exactly equal to <var title="">scriptURL</var>, then throw a
1.309 ihickson 1713: <code>URLMismatchError</code> exception and abort all these
1.159 ihickson 1714: steps.</li>
1.81 ihickson 1715:
1716: <li><p>Associate <var title="">worker</var> with <var title="">worker global scope</var>.</li>
1717:
1.301 ihickson 1718: <li><p><span>Create a new <code><a href="#messageport">MessagePort</a></code>
1.185 ihickson 1719: object</span> owned by <var title="">worker global
1720: scope</var>. Let this be the <var title="">inside
1721: port</var>.</li>
1.81 ihickson 1722:
1723: <li><p><span>Entangle</span> <var title="">outside port</var>
1724: and <var title="">inside port</var>.</li>
1725:
1726: <li><p>Return <var title="">worker</var> and perform the next
1727: step asynchronously.</li>
1.9 ihickson 1728:
1.81 ihickson 1729: <li><p>Create an event that uses the <code>MessageEvent</code>
1.115 ihickson 1730: interface, with the name <code title="event-connect">connect</code>, which does not bubble, is
1.118 ihickson 1731: not cancelable, has no default action, has a <code title="dom-MessageEvent-data">data</code> attribute whose value
1.307 ihickson 1732: is initialized to the empty string and has a <code title="dom-MessageEvent-ports">ports</code> attribute whose
1733: value is initialized to a <span title="dfn-read-only-array">read only</span> array containing
1734: only the newly created port, and <span>queue a task</span> to
1735: dispatch the event at <var title="">worker global
1736: scope</var>.</li>
1.43 ihickson 1737:
1.123 ihickson 1738: <li>
1739:
1740: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1741: <var title="">worker global scope</var>'s list of <span>the
1742: worker's <code>Document</code>s</span></a> the
1743: <code>Document</code> objects in <var title="">docs</var>.</p>
1744:
1745: </li>
1746:
1.124 ihickson 1747: <li>
1748:
1.192 ihickson 1749: <p>If the <span title="script's global object">global
1750: object</span> of the <span title="concept-script">script</span>
1.124 ihickson 1751: that invoked the constructor is a
1752: <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
1753: worker's workers</a> of the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1.192 ihickson 1754: object that is the <span title="script's global object">global
1755: object</span> of the <span title="concept-script">script</span>
1.124 ihickson 1756: that invoked the constructor.</p>
1757:
1758: </li>
1759:
1.81 ihickson 1760: <li><p>Abort all these steps.</li>
1.9 ihickson 1761:
1.155 ihickson 1762: </ol></li>
1.9 ihickson 1763:
1.185 ihickson 1764: <li><p>Create a new <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1765: object. Let <var title="">worker global scope</var> be this new
1766: object.</li>
1.9 ihickson 1767:
1.81 ihickson 1768: <li><p>Associate <var title="">worker</var> with <var title="">worker global scope</var>.</li>
1.9 ihickson 1769:
1.115 ihickson 1770: <li><p>Set the <code title="dom-SharedWorkerGlobalScope-name"><a href="#dom-sharedworkerglobalscope-name">name</a></code> attribute of
1.81 ihickson 1771: <var title="">worker global scope</var> to <var title="">name</var>.</li>
1.9 ihickson 1772:
1.301 ihickson 1773: <li><p><span>Create a new <code><a href="#messageport">MessagePort</a></code> object</span>
1.81 ihickson 1774: owned by <var title="">worker global scope</var>. Let <var title="">inside port</var> be this new object.</li>
1.9 ihickson 1775:
1.81 ihickson 1776: <li><p><span>Entangle</span> <var title="">outside port</var> and
1777: <var title="">inside port</var>.</li>
1.9 ihickson 1778:
1.155 ihickson 1779: </ol></li>
1.28 ihickson 1780:
1.123 ihickson 1781: <li><p>Return <var title="">worker</var> and perform the remaining
1782: steps asynchronously.</li>
1.18 ihickson 1783:
1.81 ihickson 1784: <li><p>Create an event that uses the <code>MessageEvent</code>
1.118 ihickson 1785: interface, with the name <code title="event-connect">connect</code>, which does not bubble, is not
1.115 ihickson 1786: cancelable, has no default action, has a <code title="dom-MessageEvent-data">data</code> attribute whose value is
1.307 ihickson 1787: initialized to the empty string and has a <code title="dom-MessageEvent-ports">ports</code> attribute whose value
1788: is initialized to a <span title="dfn-read-only-array">read
1789: only</span> array containing only the newly created port, and
1790: <span>queue a task</span> to dispatch the event at <var title="">worker global scope</var>.</li>
1.26 ihickson 1791:
1792: <li>
1.46 ihickson 1793:
1.123 ihickson 1794: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1795: <var title="">worker global scope</var>'s list of <span>the
1796: worker's <code>Document</code>s</span></a> the
1797: <code>Document</code> objects in <var title="">docs</var>.</p>
1798:
1799: </li>
1800:
1801: <li>
1802:
1.192 ihickson 1803: <p>If the <span title="script's global object">global object</span>
1.124 ihickson 1804: of the <span title="concept-script">script</span> that invoked the
1805: 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
1806: worker's workers</a> of the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1.192 ihickson 1807: object that is the <span title="script's global object">global
1808: object</span> of the <span title="concept-script">script</span>
1.124 ihickson 1809: that invoked the constructor.</p>
1810:
1811: </li>
1812:
1813: <li>
1814:
1.159 ihickson 1815: <p><a href="#run-a-worker">Run a worker</a> for <var title="">scriptURL</var>,
1.193 ihickson 1816: with the <span>script's browsing context</span> of the script that
1.159 ihickson 1817: invoked the method as the <var title="">owner browsing
1.232 ihickson 1818: context</var>, with the <span>script's document</span> of the
1819: script that invoked the method as the <var title="">owner
1820: document</var>, with the <span>origin</span> of the <span>entry
1.176 ihickson 1821: script</span> as the <var title="">owner origin</var>, and with
1822: <var title="">worker global scope</var> as the global scope.</p>
1.26 ihickson 1823:
1.60 ihickson 1824: </li>
1.81 ihickson 1825:
1.155 ihickson 1826: </ol><p>This constructor must be visible when the <span>script's global
1.192 ihickson 1827: object</span> is either a <code>Window</code> object or an object
1.155 ihickson 1828: implementing the <code><a href="#workerutils">WorkerUtils</a></code> interface.<p>The <span>task source</span> for the tasks mentioned above is the
1.299 ihickson 1829: <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">[NoInterfaceObject]
1.150 ihickson 1830: interface <dfn id="workerutils">WorkerUtils</dfn> {
1.306 ihickson 1831: void <a href="#dom-workerglobalscope-importscripts" title="dom-WorkerGlobalScope-importScripts">importScripts</a>(DOMString... urls);
1.210 ihickson 1832: readonly attribute <a href="#workernavigator">WorkerNavigator</a> <a href="#dom-worker-navigator" title="dom-worker-navigator">navigator</a>;
1.150 ihickson 1833: };
1.290 ihickson 1834: <a href="#workerutils">WorkerUtils</a> implements <span>WindowTimers</span>;
1.301 ihickson 1835: <a href="#workerutils">WorkerUtils</a> implements <span>WindowBase64</span>;</pre><p>The <code>WindowTimers</code> and <code>WindowBase64</code>
1836: interfaces are defined in the HTML specification. <a href="#refsHTML">[HTML]</a><p>The DOM APIs (<code>Node</code> objects, <code>Document</code>
1.81 ihickson 1837: objects, etc) are not available to workers in this version of this
1.155 ihickson 1838: 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 1839: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, the user agent must run the
1.155 ihickson 1840: following steps:<ol><li><p>If there are no arguments, return without doing
1.81 ihickson 1841: anything. Abort these steps.</li>
1842:
1843: <li><p><span title="resolve a url">Resolve</span> each
1844: argument.</li>
1845:
1.309 ihickson 1846: <li><p>If any fail, throw a <code>SyntaxError</code>
1.81 ihickson 1847: exception.</li>
1848:
1.26 ihickson 1849:
1.318 ihickson 1850:
1.26 ihickson 1851: <li>
1.81 ihickson 1852:
1.45 ihickson 1853: <p>Attempt to <span>fetch</span> each resource identified by the
1.194 ihickson 1854: resulting <span title="absolute URL">absolute URLs</span>, from
1.256 ihickson 1855: the <span>entry script</span>'s <span>origin</span>, with the
1.281 ihickson 1856: <i>synchronous flag</i> set.</p>
1.318 ihickson 1857:
1.81 ihickson 1858: </li>
1.26 ihickson 1859:
1860: <li>
1861:
1.81 ihickson 1862: <p>For each argument in turn, in the order given, starting with
1863: the first one, run these substeps:</p>
1.26 ihickson 1864:
1.155 ihickson 1865: <ol><li>
1.26 ihickson 1866:
1.81 ihickson 1867: <p>Wait for the fetching attempt for the corresponding resource
1868: to complete.</p>
1.60 ihickson 1869:
1.81 ihickson 1870: <p>If the fetching attempt failed, throw a
1.309 ihickson 1871: <code>NetworkError</code> exception and abort all these
1.81 ihickson 1872: steps.</p>
1.45 ihickson 1873:
1.264 ihickson 1874: <p>If the attempt succeeds, then let <var title="">source</var> be
1875: the script resource <span>decoded as UTF-8, with error
1876: handling</span>.
1877:
1878: <a href="#refsHTML">[HTML]</a>
1879:
1880: </p>
1.85 ihickson 1881:
1882: <p>Let <var title="">language</var> be JavaScript.</p>
1.61 ihickson 1883:
1.115 ihickson 1884: <p class="note">As with the worker's script, the script here is
1.81 ihickson 1885: always assumed to be JavaScript, regardless of the MIME
1.170 ihickson 1886: type.</p>
1.61 ihickson 1887:
1.81 ihickson 1888: </li>
1.26 ihickson 1889:
1.81 ihickson 1890: <li>
1.26 ihickson 1891:
1.314 ihickson 1892: <p><span>Create a script</span>, using <var title="">source</var> as the script source, the <span>URL</span>
1893: from which <var title="">source</var> was obtained, and <var title="">language</var> as the scripting language, using the
1.189 ihickson 1894: same global object, browsing context, URL character encoding,
1895: base URL, and script group as the <span title="concept-script">script</span> that was created by the
1.115 ihickson 1896: worker's <a href="#run-a-worker">run a worker</a> algorithm.</p>
1.81 ihickson 1897:
1.115 ihickson 1898: <p>Let the newly created <span title="concept-script">script</span> run until it either
1.81 ihickson 1899: returns, fails to parse, fails to catch an exception, or gets
1.115 ihickson 1900: prematurely aborted by the "<a href="#kill-a-worker">kill a worker</a>" or
1901: "<a href="#terminate-a-worker">terminate a worker</a>" algorithms defined above.</p>
1.26 ihickson 1902:
1.199 ihickson 1903: <p>If it failed to parse, then throw an ECMAScript
1904: <code>SyntaxError</code> exception and abort all these
1905: steps. <a href="#refsECMA262">[ECMA262]</a></p>
1.63 ihickson 1906:
1.320 ihickson 1907: <p>If an exception was thrown or if the script was prematurely
1.81 ihickson 1908: aborted, then abort all these steps, letting the exception or
1909: aborting continue to be processed by the script that called the
1.115 ihickson 1910: <code title="dom-WorkerGlobalScope-importScripts"><a href="#dom-workerglobalscope-importscripts">importScripts()</a></code>
1.81 ihickson 1911: method.</p>
1912:
1.115 ihickson 1913: <p>If the "<a href="#kill-a-worker">kill a worker</a>" or "<a href="#terminate-a-worker">terminate a
1.81 ihickson 1914: worker</a>" algorithms abort the script then abort all these
1915: steps.</p>
1916:
1917: </li>
1918:
1.155 ihickson 1919: </ol></li>
1.152 ihickson 1920:
1.210 ihickson 1921: </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 1922: of the <code><a href="#workerutils">WorkerUtils</a></code> interface must return an instance of
1.210 ihickson 1923: the <code><a href="#workernavigator">WorkerNavigator</a></code> interface, which represents the
1924: identity and state of the user agent (the client):<pre class="idl">interface <dfn id="workernavigator">WorkerNavigator</dfn> {};
1925: <a href="#workernavigator">WorkerNavigator</a> implements <span>NavigatorID</span>;
1926: <a href="#workernavigator">WorkerNavigator</a> implements <span>NavigatorOnLine</span>;</pre><p>Objects implementing the <code><a href="#workernavigator">WorkerNavigator</a></code> interface
1927: also implement the <code>NavigatorID</code> and
1928: <code>NavigatorOnLine</code> interfaces.
1.205 ihickson 1929:
1.226 ihickson 1930: <a href="#refsHTML">[HTML]</a>
1.205 ihickson 1931:
1.210 ihickson 1932: <p>This <code><a href="#workernavigator">WorkerNavigator</a></code> interface must not exist if the
1933: interface's <span>relevant namespace object</span> is a
1.272 ihickson 1934: <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 1935: the global scope of scripts whose <span>script's global
1936: object</span> is a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object except for
1.155 ihickson 1937: the following:<ul><li><p><code>XMLHttpRequest</code> and all interface objects and
1.81 ihickson 1938: constructors defined by the XMLHttpRequest specifications, except
1939: that the <span>document response entity body</span> must always be
1.160 ihickson 1940: null. The <span><code>XMLHttpRequest</code> base URL</span> is the
1941: <span>script's base URL</span>; the
1942: <span><code>XMLHttpRequest</code> origin</span> is the script's
1943: <span>origin</span>. <a href="#refsXHR">[XHR]</a></li>
1.81 ihickson 1944:
1.205 ihickson 1945: <li><p>The interface objects and constructors defined by this
1946: specification.</li>
1.119 ihickson 1947:
1.205 ihickson 1948: <li><p>Constructors defined by specifications that explicitly say
1949: that they should be visible when the <span>script's global
1950: object</span> is a <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>, a
1951: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>, or an object implementing the
1952: <code><a href="#workerutils">WorkerUtils</a></code> interface; the interfaces of any objects
1953: with such constructors; and the interfaces of any objects made
1954: accessible through APIs exposed by those constructors or made
1955: accessible through interfaces to be implemented by any objects that
1956: are themselves accessible to scripts whose <span>script's global
1957: object</span> implements the <code><a href="#workerutils">WorkerUtils</a></code>
1958: interface.</li>
1959:
1960: </ul><p class="note">These requirements do not override the requirements
1961: defined by the Web IDL specification, in particular concerning the
1.272 ihickson 1962: 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 1963: // <span>URL decomposition IDL attributes</span>
1.294 ihickson 1964: stringifier readonly attribute DOMString <a href="#dom-workerlocation-href" title="dom-WorkerLocation-href">href</a>;
1.115 ihickson 1965: readonly attribute DOMString <a href="#dom-workerlocation-protocol" title="dom-WorkerLocation-protocol">protocol</a>;
1966: readonly attribute DOMString <a href="#dom-workerlocation-host" title="dom-WorkerLocation-host">host</a>;
1967: readonly attribute DOMString <a href="#dom-workerlocation-hostname" title="dom-WorkerLocation-hostname">hostname</a>;
1968: readonly attribute DOMString <a href="#dom-workerlocation-port" title="dom-WorkerLocation-port">port</a>;
1969: readonly attribute DOMString <a href="#dom-workerlocation-pathname" title="dom-WorkerLocation-pathname">pathname</a>;
1970: readonly attribute DOMString <a href="#dom-workerlocation-search" title="dom-WorkerLocation-search">search</a>;
1971: readonly attribute DOMString <a href="#dom-workerlocation-hash" title="dom-WorkerLocation-hash">hash</a>;
1.155 ihickson 1972: };</pre><p>A <code><a href="#workerlocation">WorkerLocation</a></code> object represents an <span>absolute
1973: URL</span> set at its creation.<p>The <dfn id="dom-workerlocation-href" title="dom-WorkerLocation-href"><code>href</code></dfn>
1.81 ihickson 1974: attribute must return the <span>absolute URL</span> that the object
1.155 ihickson 1975: represents.<p>The <code><a href="#workerlocation">WorkerLocation</a></code> interface also has the complement
1.163 ihickson 1976: of <span>URL decomposition IDL attributes</span>, <dfn id="dom-workerlocation-protocol" title="dom-WorkerLocation-protocol"><code>protocol</code></dfn>,
1.115 ihickson 1977: <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>,
1978: <dfn id="dom-workerlocation-pathname" title="dom-WorkerLocation-pathname"><code>pathname</code></dfn>,
1979: <dfn id="dom-workerlocation-search" title="dom-WorkerLocation-search"><code>search</code></dfn>,
1.263 ihickson 1980: and <dfn id="dom-workerlocation-hash" title="dom-WorkerLocation-hash"><code>hash</code></dfn>.
1981: These must follow the rules given for <span>URL decomposition IDL
1982: attributes</span>, with the <span title="concept-uda-input">input</span> being the <span>absolute
1983: 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
1984: <span title="concept-uda-setter">common setter action</span> being a
1985: no-op, since the attributes are defined to be readonly.
1.205 ihickson 1986:
1.226 ihickson 1987: <a href="#refsHTML">[HTML]</a>
1.205 ihickson 1988:
1.209 ihickson 1989: <p>The <code><a href="#workerlocation">WorkerLocation</a></code> interface must not exist if the
1990: interface's <span>relevant namespace object</span> is a
1.281 ihickson 1991: <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 1992: <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 1993:
1.152 ihickson 1994: <dt id="refsECMA262">[ECMA262]</dt>
1995: <dd><cite><a href="http://www.ecma-international.org/publications/standards/Ecma-262.htm">ECMAScript
1.226 ihickson 1996: Language Specification</a></cite>. ECMA.</dd>
1.152 ihickson 1997:
1.226 ihickson 1998: <dt id="refsHTML">[HTML]</dt>
1999: <dd><cite><a href="http://www.whatwg.org/specs/web-apps/current-work/">HTML</a></cite>,
2000: I. Hickson. WHATWG.</dd>
1.152 ihickson 2001:
1.315 ihickson 2002:
1.154 ihickson 2003: <dt id="refsRFC2119">[RFC2119]</dt>
1.265 ihickson 2004: <dd><cite><a href="http://tools.ietf.org/html/rfc2119">Key words for use in
1.226 ihickson 2005: RFCs to Indicate Requirement Levels</a></cite>, S. Bradner. IETF.</dd>
1.154 ihickson 2006:
2007: <dt id="refsWEBIDL">[WEBIDL]</dt>
1.318 ihickson 2008:
2009: <dd><cite><a href="http://dev.w3.org/2006/webapi/WebIDL/">Web
1.226 ihickson 2010: IDL</a></cite>, C. McCormack. W3C.</dd>
1.154 ihickson 2011:
1.152 ihickson 2012: <dt id="refsXHR">[XHR]</dt>
1.318 ihickson 2013:
2014: <dd><cite><a href="http://dev.w3.org/2006/webapi/XMLHttpRequest-2/"><code>XMLHttpRequest</code></a></cite>,
1.226 ihickson 2015: A. van Kesteren. W3C.</dd>
1.152 ihickson 2016:
1.221 ihickson 2017: </dl><h2 class="no-num" id="acknowledgements">Acknowledgements</h2><!-- ACKS --><p>Thanks to
1.81 ihickson 2018:
2019: Aaron Boodman,
1.155 ihickson 2020: Алексей Проскуряков (Alexey Proskuryakov),
1.81 ihickson 2021: Anne van Kesteren,
2022: Ben Turner,
2023: Dmitry Titov,
1.96 ihickson 2024: Drew Wilson,
1.97 ihickson 2025: Jeremy Orlow,
1.81 ihickson 2026: Jonas Sicking,
2027: Justin James,
2028: Kevin Hakanson,
2029: Maciej Stachowiak,
2030: Michael Nordman,
2031: Mike Smith,
2032:
2033: and
2034:
2035: Philip Taylor
2036:
1.155 ihickson 2037: for their useful and substantial comments.<p>Huge thanks to the whole Gears team, who pioneered this
1.81 ihickson 2038: technology and whose experience has been a huge influence on this
1.155 ihickson 2039: specification.
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