Annotation of html5/workers/Overview.html, revision 1.310
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; }
5: h4 { margin: 2.5em 0 0.75em 0; }
6: h5, h6 { margin: 2.5em 0 1em; }
7: h1 + h2, h1 + h2 + h2 { margin: 0.75em 0 0.75em; }
8: h2 + h3, h3 + h4, h4 + h5, h5 + h6 { margin-top: 0.5em; }
9: p { margin: 1em 0; }
10: hr:not(.top) { display: block; background: none; border: none; padding: 0; margin: 2em 0; height: auto; }
11: dl, dd { margin-top: 0; margin-bottom: 0; }
12: dt { margin-top: 0.75em; margin-bottom: 0.25em; clear: left; }
13: dt + dt { margin-top: 0; }
14: dd dt { margin-top: 0.25em; margin-bottom: 0; }
15: dd p { margin-top: 0; }
16: dd dl + p { margin-top: 1em; }
17: dd table + p { margin-top: 1em; }
18: p + * > li, dd li { margin: 1em 0; }
19: dt, dfn { font-weight: bold; font-style: normal; }
1.300 ihickson 20: i, em { font-style: italic; }
1.82 ihickson 21: dt dfn { font-style: italic; }
22: pre, code { font-size: inherit; font-family: monospace; font-variant: normal; }
23: pre strong { color: black; font: inherit; font-weight: bold; background: yellow; }
24: pre em { font-weight: bolder; font-style: normal; }
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; }
27: table { border-collapse: collapse; border-style: hidden hidden none hidden; }
1.249 ihickson 28: table thead, table tbody { border-bottom: solid; }
1.82 ihickson 29: table tbody th:first-child { border-left: solid; }
1.180 ihickson 30: table tbody th { text-align: left; }
1.82 ihickson 31: table td, table th { border-left: solid; border-right: solid; border-bottom: solid thin; vertical-align: top; padding: 0.2em; }
32: blockquote { margin: 0 0 0 2em; border: 0; padding: 0; font-style: italic; }
33:
34: .bad, .bad *:not(.XXX) { color: gray; border-color: gray; background: transparent; }
35: .matrix, .matrix td { border: none; text-align: right; }
36: .matrix { margin-left: 2em; }
37: .dice-example { border-collapse: collapse; border-style: hidden solid solid hidden; border-width: thin; margin-left: 3em; }
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39: .dice-example td, .dice-example th { border: solid thin; width: 1.35em; height: 1.05em; text-align: center; padding: 0; }
40:
41: .toc dfn, h1 dfn, h2 dfn, h3 dfn, h4 dfn, h5 dfn, h6 dfn { font: inherit; }
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; }
1.304 ihickson 45: pre.idl::before { content: "IDL"; font: bold small sans-serif; padding: 0.5em; background: white; position: absolute; top: 0; margin: -1px 0 0 -4em; width: 1.5em; border: thin solid; border-radius: 0 0 0 0.5em }
1.82 ihickson 46: pre.css { border: solid thin; background: #FFFFEE; color: black; padding: 0.5em 1em; }
47: pre.css:first-line { color: #AAAA50; }
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; }
50: dl.domintro dt, dl.domintro dt * { color: black; text-decoration: none; }
51: dl.domintro dd { margin: 0.5em 0 1em 2em; padding: 0; }
52: dl.domintro dd p { margin: 0.5em 0; }
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; }
55: dl.switch > dt { text-indent: -1.5em; }
56: dl.switch > dt:before { content: '\21AA'; padding: 0 0.5em 0 0; display: inline-block; width: 1em; text-align: right; line-height: 0.5em; }
1.121 ihickson 57: dl.triple { padding: 0 0 0 1em; }
58: dl.triple dt, dl.triple dd { margin: 0; display: inline }
59: dl.triple dt:after { content: ':'; }
60: dl.triple dd:after { content: '\A'; white-space: pre; }
1.82 ihickson 61: .diff-old { text-decoration: line-through; color: silver; background: transparent; }
62: .diff-chg, .diff-new { text-decoration: underline; color: green; background: transparent; }
63: a .diff-new { border-bottom: 1px blue solid; }
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"]),
70: li > span:not([title=""]):not([class="XXX"]):not([class="impl"]):not([class="note"]), { border-bottom: solid #9999CC; }
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; }
76: div.head .logo img { border: none } /* remove border from top image */
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; }
101: .annotation:before { position: absolute; left: 0; top: 0; width: 100%; height: 100%; margin: 6px -6px -6px 6px; background: #333333; z-index: -1; content: ''; }
102: .annotation :link, .annotation :visited { color: inherit; }
103: .annotation :link:hover, .annotation :visited:hover { background: transparent; }
104: .annotation span { border: none ! important; }
1.82 ihickson 105: .note { color: green; background: transparent; font-family: sans-serif; }
106: .warning { color: red; background: transparent; }
107: .note, .warning { font-weight: bolder; font-style: italic; }
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; }
110: span.note { padding: 0 2em; }
111: .note p:first-child, .warning p:first-child { margin-top: 0; }
112: .note p:last-child, .warning p:last-child { margin-bottom: 0; }
113: .warning:before { font-style: normal; }
114: p.note:before { content: 'Note: '; }
115: p.warning:before { content: '\26A0 Warning! '; }
116:
117: .bookkeeping:before { display: block; content: 'Bookkeeping details'; font-weight: bolder; font-style: italic; }
118: .bookkeeping { font-size: 0.8em; margin: 2em 0; }
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; }
124: h4 + .element, h4 + div + .element { margin-top: -2.5em; padding-top: 2em; }
125: .element {
1.88 ihickson 126: background: #EEEEFF;
1.82 ihickson 127: color: black;
128: margin: 0 0 1em 0.15em;
129: padding: 0 1em 0.25em 0.75em;
1.88 ihickson 130: border-left: solid #9999FF 0.25em;
1.82 ihickson 131: position: relative;
132: z-index: 1;
133: }
134: .element:before {
135: position: absolute;
136: z-index: 2;
137: top: 0;
138: left: -1.15em;
139: height: 2em;
140: width: 0.9em;
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; }
152: ul.domTree li { padding: 0; margin: 0; list-style: none; position: relative; }
153: ul.domTree li li { list-style: none; }
154: ul.domTree li:first-child::before { position: absolute; top: 0; height: 0.6em; left: -0.75em; width: 0.5em; border-style: none none solid solid; content: ''; border-width: 0.1em; }
155: ul.domTree li:not(:last-child)::after { position: absolute; top: 0; bottom: -0.6em; left: -0.75em; width: 0.5em; border-style: none none solid solid; content: ''; border-width: 0.1em; }
156: ul.domTree span { font-style: italic; font-family: serif; }
157: ul.domTree .t1 code { color: purple; font-weight: bold; }
158: ul.domTree .t2 { font-style: normal; font-family: monospace; }
159: ul.domTree .t2 .name { color: black; font-weight: bold; }
160: ul.domTree .t2 .value { color: blue; font-weight: normal; }
161: ul.domTree .t3 code, .domTree .t4 code, .domTree .t5 code { color: gray; }
162: ul.domTree .t7 code, .domTree .t8 code { color: green; }
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:
1.310 ! ihickson 218: <h2 class="no-num no-toc" id="editor-s-draft-4-october-2011">Editor's Draft 4 October 2011</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:
1.2 ihickson 224: <dt>Previous Versions:</dt>
1.279 ihickson 225: <dd><a href="http://www.w3.org/TR/2011/WD-workers-20110310/">http://www.w3.org/TR/2011/WD-workers-20110310/</a></dd>
226: <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 227: <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 228: <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 229: <!-- :ZZZ -->
1.271 ihickson 230: <dt>Editor:</dt>
1.115 ihickson 231: <dd><a href="mailto:ian@hixie.ch">Ian Hickson</a>, Google, Inc.</dd>
1.155 ihickson 232: </dl><p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a>
1.285 ihickson 233: © 2011 <a href="http://www.w3.org/"><abbr title="World Wide
1.155 ihickson 234: Web Consortium">W3C</abbr></a><sup>®</sup> (<a href="http://www.csail.mit.edu/"><abbr title="Massachusetts
1.297 ihickson 235: Institute of Technology">MIT</abbr></a>, <a href="http://www.ercim.eu/"><abbr title="European Research
1.115 ihickson 236: Consortium for Informatics and Mathematics">ERCIM</abbr></a>, <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C
237: <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
238: <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
239: and <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document
1.81 ihickson 240: use</a> rules apply.</p>
1.201 ihickson 241:
1.254 ihickson 242:
1.252 ihickson 243: <!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
1.255 ihickson 244: <p class="alt">The bulk of the text of this specification is also
1.254 ihickson 245: 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
246: reuse of the specification text.</p>
1.252 ihickson 247: <!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
248:
1.254 ihickson 249:
1.155 ihickson 250: </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 251: authors to spawn background workers running scripts in parallel to
252: their main page. This allows for thread-like operation with
1.281 ihickson 253: 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 254: time of its publication. Other documents may supersede this
1.297 ihickson 255: document. A list of current W3C publications and the
256:
257: most recently formally published <!-- DO NOT CHANGE THIS BACK TO THE STANDARD BOILERPLATE, AS IT IS INACCURATE -->
258:
259: revision of this technical report can be found in the <a href="http://www.w3.org/TR/">W3C technical reports index</a> at
260: http://www.w3.org/TR/.</em></p><p>If you wish to make comments regarding this document in a manner
1.271 ihickson 261: 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
262: public bug database</a>. If you do not have an account then you can
263: enter feedback using this form:<form action="http://www.whatwg.org/specs/web-apps/current-work/file-spam.cgi" method="post">
264: <fieldset><legend>Feedback Comments</legend>
265: <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
266: indicating the title of the section for which you are submitting
267: feedback, quoting the text that's wrong today if appropriate. If
268: you're suggesting a new feature, it's really important to say
269: <em>what</em> the problem you're trying to solve is. That's more
270: important than the solution, in fact.</label></p>
271: <p><textarea cols="79" id="feedbackBox" name="text" rows="10"></textarea></p>
272: <p class="note">Please don't use section numbers as these tend to
273: change rapidly and make your feedback harder to understand.</p>
274: <script type="text/javascript">
1.287 ihickson 275: function checkFeedbackForm(form) {
276: if (form.elements.text.value.match(/^ *</)) {
277: alert('Please don\'t start your feedback with an angle bracket, instead explain what topic your feedback is about first.');
278: return true;
279: } else if (form.elements.text.value.match(/ [^ ]+ [^ ]+ [^ ]+ [^ ]+ /)) {
280: if (form.elements.text.value.match(/^Please enter your feedback, carefully/)) {
281: alert('Please enter your feedback, explaining what is wrong, and without repeating the instructions. Thanks!');
282: return true;
283: } else if (form.elements.text.value.match(/ [^ ]+ [^ ]+ [^ ]+ [^ ]+ /)) {
284: form.action = "http://www.whatwg.org/specs/web-apps/current-work/file-bug.cgi";
285: return true;
286: } else {
287: alert('Please include significantly more detail about exactly what problem you are trying to solve.');
288: return false;
289: }
290: }
291: }
1.271 ihickson 292: </script><p>
1.277 ihickson 293: <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 294: </p>
295: </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>,
296: <a href="http://lists.w3.org/Archives/Public/public-webapps/">archives</a>),
1.115 ihickson 297: or <a href="mailto:whatwg@whatwg.org">whatwg@whatwg.org</a> (<a href="http://lists.whatwg.org/listinfo.cgi/whatwg-whatwg.org">subscribe</a>,
298: <a href="http://lists.whatwg.org/pipermail/whatwg-whatwg.org/">archives</a>).
1.281 ihickson 299: All feedback is welcome.</p><p>Implementors should be aware that this specification is not
1.81 ihickson 300: stable. <strong>Implementors who are not taking part in the
301: discussions are likely to find the specification changing out from
302: under them in incompatible ways.</strong> Vendors interested in
303: implementing this specification before it eventually reaches the
304: Candidate Recommendation stage should join the aforementioned
1.271 ihickson 305: mailing lists and take part in the discussions.<div id="multipage-common">
1.281 ihickson 306: </div><p>The latest
1.271 ihickson 307: stable version of the editor's draft of this specification is always
308: available on <a href="http://dev.w3.org/html5/workers/">the W3C CVS server</a>
309: and in the <a href="http://svn.whatwg.org/webapps/">WHATWG
310: Subversion repository</a>. The <a href="http://www.whatwg.org/specs/web-apps/current-work/complete.html">latest
311: editor's working copy</a> (which may contain unfinished text in the
312: process of being prepared) contains the latest draft text of this
313: 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
314: FAQ</a>.<p>Notifications of changes to this specification are sent along
315: with notifications of changes to related specifications using the
316: following mechanisms:<dl><dt>E-mail notifications of changes</dt>
317: <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>
318: <dt>Browsable version-control record of all changes:</dt>
319: <dd>CVSWeb interface with side-by-side diffs: <a href="http://dev.w3.org/cvsweb/html5/">http://dev.w3.org/cvsweb/html5/</a></dd>
320: <dd>Annotated summary with unified diffs: <a href="http://html5.org/tools/web-apps-tracker">http://html5.org/tools/web-apps-tracker</a></dd>
321: <dd>Raw Subversion interface: <code>svn checkout http://svn.whatwg.org/webapps/</code></dd>
322: </dl><p>The W3C <a href="http://www.w3.org/2008/webapps/">Web Applications
1.81 ihickson 323: Working Group</a> is the W3C working group responsible for this
324: specification's progress along the W3C Recommendation track.
1.310 ! ihickson 325: This specification is the 4 October 2011 Editor's Draft.
1.281 ihickson 326: </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 327: 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 328: any patent disclosures</a> made in connection with the deliverables
329: of the group; that page also includes instructions for disclosing a
330: patent. An individual who has actual knowledge of a patent which the
1.115 ihickson 331: individual believes contains <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential
332: 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 333: 6 of the W3C Patent Policy</a>.<h2 class="no-num no-toc" id="contents">Table of Contents</h2>
1.115 ihickson 334: <ol class="toc">
335: <li><a href="#introduction"><span class="secno">1 </span>Introduction</a>
1.81 ihickson 336: <ol>
1.115 ihickson 337: <li><a href="#scope"><span class="secno">1.1 </span>Scope</a></li>
1.303 ihickson 338: <li><a href="#examples"><span class="secno">1.2 </span>Examples</a>
1.81 ihickson 339: <ol>
1.115 ihickson 340: <li><a href="#a-background-number-crunching-worker"><span class="secno">1.2.1 </span>A background number-crunching worker</a></li>
341: <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>
342: <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 343: <li><a href="#shared-workers-introduction"><span class="secno">1.2.4 </span>Shared workers introduction</a></li>
344: <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 345: <li><a href="#delegation"><span class="secno">1.2.6 </span>Delegation</a></ol></li>
346: <li><a href="#tutorials"><span class="secno">1.3 </span>Tutorials</a>
347: <ol>
348: <li><a href="#creating-a-dedicated-worker"><span class="secno">1.3.1 </span>Creating a dedicated worker</a></li>
349: <li><a href="#communicating-with-a-dedicated-worker"><span class="secno">1.3.2 </span>Communicating with a dedicated worker</a></li>
350: <li><a href="#shared-workers"><span class="secno">1.3.3 </span>Shared workers</a></ol></ol></li>
1.148 ihickson 351: <li><a href="#conformance-requirements"><span class="secno">2 </span>Conformance requirements</a>
1.82 ihickson 352: <ol>
1.148 ihickson 353: <li><a href="#dependencies"><span class="secno">2.1 </span>Dependencies</a></ol></li>
354: <li><a href="#terminology"><span class="secno">3 </span>Terminology</a></li>
355: <li><a href="#infrastructure"><span class="secno">4 </span>Infrastructure</a>
356: <ol>
1.301 ihickson 357: <li><a href="#dependencies-0"><span class="secno">4.1 </span>Dependencies</a></li>
358: <li><a href="#the-global-scope"><span class="secno">4.2 </span>The global scope</a>
1.81 ihickson 359: <ol>
1.301 ihickson 360: <li><a href="#the-workerglobalscope-abstract-interface"><span class="secno">4.2.1 </span>The <code>WorkerGlobalScope</code> abstract interface</a></li>
361: <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>
362: <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>
363: <li><a href="#origins-of-workers"><span class="secno">4.3 </span>Origins of workers</a></li>
364: <li><a href="#the-event-loop"><span class="secno">4.4 </span>The event loop</a></li>
365: <li><a href="#the-worker-s-lifetime"><span class="secno">4.5 </span>The worker's lifetime</a></li>
366: <li><a href="#processing-model"><span class="secno">4.6 </span>Processing model</a></li>
367: <li><a href="#runtime-script-errors"><span class="secno">4.7 </span>Runtime script errors</a></li>
368: <li><a href="#creating-workers"><span class="secno">4.8 </span>Creating workers</a>
1.81 ihickson 369: <ol>
1.301 ihickson 370: <li><a href="#the-abstractworker-abstract-interface"><span class="secno">4.8.1 </span>The <code>AbstractWorker</code> abstract interface</a></li>
371: <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>
372: <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 373: <li><a href="#apis-available-to-workers"><span class="secno">5 </span>APIs available to workers</a>
1.81 ihickson 374: <ol>
1.148 ihickson 375: <li><a href="#importing-scripts-and-libraries"><span class="secno">5.1 </span>Importing scripts and libraries</a></li>
1.210 ihickson 376: <li><a href="#the-workernavigator-object"><span class="secno">5.2 </span>The <code>WorkerNavigator</code> object</a></li>
1.272 ihickson 377: <li><a href="#interface-objects-and-constructors"><span class="secno">5.3 </span>Interface objects and constructors</a></li>
378: <li><a href="#worker-locations"><span class="secno">5.4 </span>Worker locations</a></ol></li>
1.115 ihickson 379: <li><a class="no-num" href="#references">References</a></li>
380: <li><a class="no-num" href="#acknowledgements">Acknowledgements</a></ol>
1.281 ihickson 381: <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 382: background independently of any user interface scripts.<p>This allows for long-running scripts that are not interrupted by
1.81 ihickson 383: scripts that respond to clicks or other user interactions, and
384: allows long tasks to be executed without yielding to keep the page
1.155 ihickson 385: responsive.<p>Workers (as these background scripts are called herein) are
1.81 ihickson 386: relatively heavy-weight, and are not intended to be used in large
387: numbers. For example, it would be inappropriate to launch one worker
388: for each pixel of a four megapixel image. The examples below show
1.155 ihickson 389: some appropriate uses of workers.<p>Generally, workers are expected to be long-lived, have a high
1.303 ihickson 390: 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 391: 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
392: expensive task without interrupting the user interface.<p>In this example, the main document spawns a worker to
393: (naïvely) compute prime numbers, and progressively displays the
394: most recently found prime number.<p>The main page is as follows:<pre><!DOCTYPE HTML>
1.81 ihickson 395: <html>
396: <head>
397: <title>Worker example: One-core computation</title>
398: </head>
399: <body>
400: <p>The highest prime number discovered so far is: <output id="result"></output></p>
401: <script>
1.50 ihickson 402: var worker = new Worker('worker.js');
403: worker.onmessage = function (event) {
1.54 ihickson 404: document.getElementById('result').textContent = event.data;
1.29 ihickson 405: };
1.81 ihickson 406: </script>
407: </body>
1.155 ihickson 408: </html></pre><p>The <code title="dom-Worker"><a href="#dom-worker">Worker()</a></code> constructor call
1.115 ihickson 409: creates a worker and returns a <code><a href="#worker">Worker</a></code> object
1.81 ihickson 410: representing that worker, which is used to communicate with the
1.177 ihickson 411: 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 412: search: while (true) {
413: n += 1;
414: for (var i = 2; i <= Math.sqrt(n); i += 1)
415: if (n % i == 0)
416: continue search;
417: // found a prime!
1.50 ihickson 418: postMessage(n);
1.155 ihickson 419: }</pre><p>The bulk of this code is simply an unoptimized search for a prime
1.295 ihickson 420: number. The <code title="dom-DedicatedWorkerGlobalScope-postMessage"><a href="#dom-dedicatedworkerglobalscope-postmessage">postMessage()</a></code>
421: method is used to send a message back to the page when a prime is
422: 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 423: task is to listen for notifications from the server, and, when
424: appropriate, either add or remove data from the client-side
1.155 ihickson 425: database.<p>Since no communication occurs between the worker and the main
426: page, the main page can start the worker by just doing:<pre><script>
1.50 ihickson 427: new Worker('worker.js');
1.155 ihickson 428: </script></pre><p>The worker itself is as follows:<pre>var server = new WebSocket('ws://whatwg.org/database');
1.42 ihickson 429: var database = openDatabase('demobase', '1.0', 'Demo Database', 10240);
1.31 ihickson 430: server.onmessage = function (event) {
431: // data is in the format "command key value"
1.54 ihickson 432: var data = event.data.split(' ');
1.31 ihickson 433: switch (data[0]) {
434: case '+':
435: database.transaction(function(tx) {
436: tx.executeSql('INSERT INTO pairs (key, value) VALUES (?, ?)', data[1], data[2]);
437: });
438: case '-':
439: database.transaction(function(tx) {
440: tx.executeSql('DELETE FROM pairs WHERE key=? AND value=?', data[1], data[2]);
441: });
442: }
1.155 ihickson 443: };</pre><p>This connects to the server using the <code>WebSocket</code>
1.81 ihickson 444: mechanism and opens the local database (which, we presume, has been
445: created earlier). The worker then just listens for messages from the
446: server and acts on them as appropriate, forever (or until the main
1.155 ihickson 447: page is closed).<p><a href="http://www.whatwg.org/demos/workers/database-updater/page.html">View
1.81 ihickson 448: this example online</a>. (This example will not actually function,
449: since the server does not actually exist and the database is not
1.155 ihickson 450: 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 451: fetching stock updates for at regular intervals, and one for
1.155 ihickson 452: fetching performing search queries that the user requests.<p>The main page is as follows:<pre><!DOCTYPE HTML>
1.81 ihickson 453: <html>
454: <head>
455: <title>Worker example: Stock ticker</title>
456: <script>
1.33 ihickson 457: // TICKER
458: var symbol = 'GOOG'; // default symbol to watch
1.50 ihickson 459: var ticker = new Worker('ticker.js');
1.33 ihickson 460:
461: // SEARCHER
1.50 ihickson 462: var searcher = new Worker('searcher.js');
1.33 ihickson 463: function search(query) {
1.50 ihickson 464: searcher.postMessage(query);
1.33 ihickson 465: }
466:
467: // SYMBOL SELECTION UI
468: function select(newSymbol) {
469: symbol = newSymbol;
1.50 ihickson 470: ticker.postMessage(symbol);
1.33 ihickson 471: }
1.81 ihickson 472: </script>
473: </head>
1.122 ihickson 474: <body onload="search('')">
1.81 ihickson 475: <p><output id="symbol"></output> <output id="value"></output></p>
476: <script>
1.50 ihickson 477: ticker.onmessage = function (event) {
1.54 ihickson 478: var data = event.data.split(' ');
1.33 ihickson 479: document.getElementById('symbol').textContent = data[0];
480: document.getElementById('value').textContent = data[1];
481: };
1.50 ihickson 482: ticker.postMessage(symbol);
1.81 ihickson 483: </script>
1.122 ihickson 484: <p><label>Search: <input type="text" autofocus oninput="search(this.value)"></label></p>
1.81 ihickson 485: <ul id="results"></ul>
486: <script>
1.50 ihickson 487: searcher.onmessage = function (event) {
1.54 ihickson 488: var data = event.data.split(' ');
1.33 ihickson 489: var results = document.getElementById('results');
490: while (results.hasChildNodes()) // clear previous results
491: results.removeChild(results.firstChild);
492: for (var i = 0; i < data.length; i += 1) {
493: // add a list item with a button for each result
494: var li = document.createElement('li');
495: var button = document.createElement('button');
496: button.value = data[i];
497: button.type = 'button';
498: button.onclick = function () { select(this.value); };
499: button.textContent = data[i];
500: li.appendChild(button);
501: results.appendChild(li);
502: }
503: };
1.81 ihickson 504: </script>
505: <p>(The data in this example is not real. Try searching for "Google" or "Apple".)</p>
506: </body>
1.155 ihickson 507: </html></pre><p>The two workers use a common library for performing the actual
508: network calls. This library is as follows:<pre>function get(url) {
1.50 ihickson 509: try {
510: var xhr = new XMLHttpRequest();
511: xhr.open('GET', url, false);
512: xhr.send();
513: return xhr.responseText;
514: } catch (e) {
515: return ''; // turn all errors into empty results
516: }
1.155 ihickson 517: }</pre><p>The stock updater worker is as follows:<pre>importScripts('io.js');
1.33 ihickson 518: var timer;
519: var symbol;
520: function update() {
1.50 ihickson 521: postMessage(symbol + ' ' + get('stock.cgi?' + symbol));
1.33 ihickson 522: timer = setTimeout(update, 10000);
523: }
1.50 ihickson 524: onmessage = function (event) {
1.33 ihickson 525: if (timer)
526: clearTimeout(timer);
1.54 ihickson 527: symbol = event.data;
1.33 ihickson 528: update();
1.155 ihickson 529: };</pre><p>The search query worker is as follows:<pre>importScripts('io.js');
1.50 ihickson 530: onmessage = function (event) {
1.54 ihickson 531: postMessage(get('search.cgi?' + event.data));
1.238 ihickson 532: };</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
533: example. Shared workers use slightly different APIs, since each
534: worker can have multiple connections.<p>This first example shows how you connect to a worker and how a
535: worker can send a message back to the page when it connects to
1.239 ihickson 536: it. Received messages are displayed in a log.<p>Here is the HTML page:<pre><!DOCTYPE HTML>
537: <title>Shared workers: demo 1</title>
538: <pre id="log">Log:</pre>
539: <script>
540: var worker = new SharedWorker('test.js');
541: var log = document.getElementById('log');
542: worker.port.onmessage = function(e) { // note: not worker.onmessage!
543: log.textContent += '\n' + e.data;
544: }
545: </script>
546: </pre><p>Here is the JavaScript worker:<pre>onconnect = function(e) {
547: var port = e.ports[0];
548: port.postMessage('Hello World!');
549: }
1.259 ihickson 550: </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 551: first, messages are received using <code title="">addEventListener()</code> instead of an <span title="event
552: handler IDL attributes">event handler IDL attribute</span>, and
553: second, a message is sent <em>to</em> the worker, causing the worker
554: to send another message in return. Received messages are again
1.239 ihickson 555: displayed in a log.<p>Here is the HTML page:<pre><!DOCTYPE HTML>
1.240 ihickson 556: <title>Shared workers: demo 2</title>
1.239 ihickson 557: <pre id="log">Log:</pre>
558: <script>
559: var worker = new SharedWorker('test.js');
560: var log = document.getElementById('log');
1.240 ihickson 561: worker.port.addEventListener('message', function(e) {
1.239 ihickson 562: log.textContent += '\n' + e.data;
1.240 ihickson 563: }, false);
564: worker.port.start(); // note: need this when using addEventListener
565: worker.port.postMessage('ping');
1.239 ihickson 566: </script>
567: </pre><p>Here is the JavaScript worker:<pre>onconnect = function(e) {
568: var port = e.ports[0];
569: port.postMessage('Hello World!');
1.240 ihickson 570: port.onmessage = function(e) {
571: port.postMessage('pong'); // not e.ports[0].postMessage!
572: // e.target.postMessage('pong'); would work also
573: }
1.239 ihickson 574: }
1.259 ihickson 575: </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 576: connect to the same worker; in this case, the second page is merely
577: in an <code>iframe</code> on the first page, but the same principle
578: would apply to an entirely separate page in a separate
1.239 ihickson 579: <span>top-level browsing context</span>.<p>Here is the outer HTML page:<pre><!DOCTYPE HTML>
580: <title>Shared workers: demo 3</title>
581: <pre id="log">Log:</pre>
582: <script>
583: var worker = new SharedWorker('test.js');
584: var log = document.getElementById('log');
585: worker.port.addEventListener('message', function(e) {
586: log.textContent += '\n' + e.data;
587: }, false);
588: worker.port.start();
589: worker.port.postMessage('ping');
590: </script>
591: <iframe src="inner.html"></iframe>
592: </pre><p>Here is the inner HTML page:<pre><!DOCTYPE HTML>
593: <title>Shared workers: demo 3 inner frame</title>
594: <pre id=log>Inner log:</pre>
595: <script>
596: var worker = new SharedWorker('test.js');
597: var log = document.getElementById('log');
598: worker.port.onmessage = function(e) {
599: log.textContent += '\n' + e.data;
600: }
601: </script>
602: </pre><p>Here is the JavaScript worker:<pre>var count = 0;
603: onconnect = function(e) {
604: count += 1;
605: var port = e.ports[0];
606: port.postMessage('Hello World! You are connection #' + count);
607: port.onmessage = function(e) {
608: port.postMessage('pong');
609: }
610: }
1.259 ihickson 611: </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 612: are all viewing the same map. All the windows share the same map
613: information, with a single worker coordinating all the viewers. Each
614: viewer can move around independently, but if they set any data on
1.155 ihickson 615: the map, all the viewers are updated.<p>The main page isn't interesting, it merely provides a way to open
616: the viewers:<pre><!DOCTYPE HTML>
1.81 ihickson 617: <html>
618: <head>
619: <title>Workers example: Multiviewer</title>
620: <script>
1.36 ihickson 621: function openViewer() {
622: window.open('viewer.html');
623: }
1.81 ihickson 624: </script>
625: </head>
626: <body>
627: <p><button type=button onclick="openViewer()">Open a new
628: viewer</button></p>
629: <p>Each viewer opens in a new window. You can have as many viewers
630: as you like, they all view the same data.</p>
631: </body>
1.155 ihickson 632: </html></pre><p>The viewer is more involved:<pre><!DOCTYPE HTML>
1.81 ihickson 633: <html>
634: <head>
635: <title>Workers example: Multiviewer viewer</title>
636: <script>
1.50 ihickson 637: var worker = new SharedWorker('worker.js', 'core');
1.36 ihickson 638:
639: // CONFIGURATION
640: function configure(event) {
1.54 ihickson 641: if (event.data.substr(0, 4) != 'cfg ') return;
642: var name = event.data.substr(4).split(' ', 1);
1.36 ihickson 643: // update display to mention our name is name
644: document.getElementsByTagName('h1')[0].textContent += ' ' + name;
645: // no longer need this listener
1.43 ihickson 646: worker.port.removeEventListener('message', configure, false);
1.36 ihickson 647: }
1.53 ihickson 648: worker.port.addEventListener('message', configure, false);
1.36 ihickson 649:
650: // MAP
651: function paintMap(event) {
1.54 ihickson 652: if (event.data.substr(0, 4) != 'map ') return;
653: var data = event.data.substr(4).split(',');
1.36 ihickson 654: // display tiles data[0] .. data[8]
655: var canvas = document.getElementById('map');
656: var context = canvas.getContext('2d');
657: for (var y = 0; y < 3; y += 1) {
658: for (var x = 0; x < 3; x += 1) {
659: var tile = data[y * 3 + x];
660: if (tile == '0')
661: context.fillStyle = 'green';
662: else
663: context.fillStyle = 'maroon';
664: fillRect(x * 50, y * 50, 50, 50);
665: }
666: }
667: }
1.53 ihickson 668: worker.port.addEventListener('message', paintMap, false);
1.36 ihickson 669:
670: // PUBLIC CHAT
671: function updatePublicChat(event) {
1.54 ihickson 672: if (event.data.substr(0, 4) != 'txt ') return;
673: var name = event.data.substr(4).split(' ', 1);
674: var message = event.data.substr(4 + length(name) + 1);
1.81 ihickson 675: // display "<name> message" in public chat
1.36 ihickson 676: var dialog = document.getElementById('public');
677: var dt = document.createElement('dt');
678: dt.textContent = name;
679: dialog.appendChild(dt);
680: var dd = document.createElement('dd');
681: dd.textContent = message;
682: dialog.appendChild(dd);
683: }
1.53 ihickson 684: worker.port.addEventListener('message', updatePublicChat, false);
1.36 ihickson 685:
686: // PRIVATE CHAT
687: function startPrivateChat(event) {
1.54 ihickson 688: if (event.data.substr(0, 4) != 'msg ') return;
689: var name = event.data.substr(4).split(' ', 1);
1.84 ihickson 690: var port = event.ports[0];
1.36 ihickson 691: // display a private chat UI
692: var ul = document.getElementById('private');
693: var li = document.createElement('li');
694: var h3 = document.createElement('h3');
695: h3.textContent = 'Private chat with ' + name;
696: li.appendChild(h3);
697: var dialog = document.createElement('dialog');
698: var addMessage = function(name, message) {
699: var dt = document.createElement('dt');
700: dt.textContent = name;
701: dialog.appendChild(dt);
702: var dd = document.createElement('dd');
703: dd.textContent = message;
704: dialog.appendChild(dd);
705: };
706: port.onmessage = function (event) {
1.54 ihickson 707: addMessage(name, event.data);
1.36 ihickson 708: };
709: li.appendChild(dialog);
710: var form = document.createElement('form');
711: var p = document.createElement('p');
712: var input = document.createElement('input');
713: input.size = 50;
714: p.appendChild(input);
715: p.appendChild(document.createTextNode(' '));
716: var button = document.createElement('button');
717: button.textContent = 'Post';
718: p.appendChild(button);
719: form.onsubmit = function () {
720: port.postMessage(input.value);
721: addMessage('me', input.value);
722: input.value = '';
723: return false;
724: };
725: form.appendChild(p);
726: li.appendChild(form);
727: }
1.53 ihickson 728: worker.port.addEventListener('message', startPrivateChat, false);
1.188 ihickson 729:
730: worker.port.start();
1.81 ihickson 731: </script>
732: </head>
733: <body>
734: <h1>Viewer</h1>
735: <h2>Map</h2>
736: <p><canvas id="map" height=150 width=150></canvas></p>
737: <p>
738: <button type=button onclick="worker.port.postMessage('mov left')">Left</button>
739: <button type=button onclick="worker.port.postMessage('mov up')">Up</button>
740: <button type=button onclick="worker.port.postMessage('mov down')">Down</button>
741: <button type=button onclick="worker.port.postMessage('mov right')">Right</button>
742: <button type=button onclick="worker.port.postMessage('set 0')">Set 0</button>
743: <button type=button onclick="worker.port.postMessage('set 1')">Set 1</button>
744: </p>
745: <h2>Public Chat</h2>
746: <dialog id="public"></dialog>
747: <form onsubmit="worker.port.postMessage('txt ' + message.value); message.value = ''; return false;">
748: <p>
749: <input type="text" name="message" size="50">
750: <button>Post</button>
751: </p>
752: </form>
753: <h2>Private Chat</h2>
754: <ul id="private"></ul>
755: </body>
756: </html>
1.155 ihickson 757: </pre><p>There are several key things worth noting about the way the
758: viewer is written.<p><strong>Multiple listeners</strong>. Instead of a single message
1.81 ihickson 759: processing function, the code here attaches multiple event
760: listeners, each one performing a quick check to see if it is
761: relevant for the message. In this example it doesn't make much
762: difference, but if multiple authors wanted to collaborate using a
763: single port to communicate with a worker, it would allow for
764: independent code instead of changes having to all be made to a
1.155 ihickson 765: single event handling function.<p>Registering event listeners in this way also allows you to
1.81 ihickson 766: unregister specific listeners when you are done with them, as is
767: done with the <code title="">configure()</code> method in this
1.155 ihickson 768: example.<p>Finally, the worker:<pre>
769: var nextName = 0;
1.36 ihickson 770: function getNextName() {
771: // this could use more friendly names
772: // but for now just return a number
773: return nextName++;
774: }
775:
776: var map = [
777: [0, 0, 0, 0, 0, 0, 0],
778: [1, 1, 0, 1, 0, 1, 1],
779: [0, 1, 0, 1, 0, 0, 0],
780: [0, 1, 0, 1, 0, 1, 1],
781: [0, 0, 0, 1, 0, 0, 0],
782: [1, 0, 0, 1, 1, 1, 1],
783: [1, 1, 0, 1, 1, 0, 1],
784: ];
785:
786: function wrapX(x) {
787: if (x < 0) return wrapX(x + map[0].length);
1.81 ihickson 788: if (x >= map[0].length) return wrapX(x - map[0].length);
1.36 ihickson 789: return x;
790: }
791:
792: function wrapY(y) {
793: if (y < 0) return wrapY(y + map.length);
1.81 ihickson 794: if (y >= map[0].length) return wrapY(y - map.length);
1.36 ihickson 795: return y;
796: }
797:
1.50 ihickson 798: function sendMapData(callback) {
1.36 ihickson 799: var data = '';
800: for (var y = viewer.y-1; y <= viewer.y+1; y += 1) {
801: for (var x = viewer.x-1; x <= viewer.x+1; x += 1) {
802: if (data != '')
803: data += ',';
804: data += map[y][x];
805: }
806: }
1.50 ihickson 807: callback('map ' + data);
1.36 ihickson 808: }
809:
810: var viewers = {};
811: onconnect = function (event) {
1.84 ihickson 812: event.ports[0]._name = getNextName();
813: event.ports[0]._data = { port: event.port, x: 0, y: 0, };
814: viewers[event.ports[0]._name] = event.port._data;
815: event.ports[0].postMessage('cfg ' + name);
816: event.ports[0].onmessage = getMessage;
817: sendMapData(event.ports[0].postMessage);
1.36 ihickson 818: };
819:
820: function getMessage(event) {
1.54 ihickson 821: switch (event.data.substr(0, 4)) {
1.36 ihickson 822: case 'mov ':
1.54 ihickson 823: var direction = event.data.substr(4);
1.36 ihickson 824: var dx = 0;
825: var dy = 0;
826: switch (direction) {
827: case 'up': dy = -1; break;
828: case 'down': dy = 1; break;
829: case 'left': dx = -1; break;
830: case 'right': dx = 1; break;
831: }
832: event.target._data.x = wrapX(event.target._data.x + dx);
833: event.target._data.y = wrapY(event.target._data.y + dy);
1.50 ihickson 834: sendMapData(event.target.postMessage);
1.36 ihickson 835: break;
836: case 'set ':
1.54 ihickson 837: var value = event.data.substr(4);
1.36 ihickson 838: map[event.target._data.y][event.target._data.x] = value;
839: for (var viewer in viewers)
1.50 ihickson 840: sendMapData(viewers[viewer].port.postMessage);
1.36 ihickson 841: break;
842: case 'txt ':
843: var name = event.target._name;
1.54 ihickson 844: var message = event.data.substr(4);
1.36 ihickson 845: for (var viewer in viewers)
846: viewers[viewer].port.postMessage('txt ' + name + ' ' + message);
847: break;
848: case 'msg ':
849: var party1 = event._data;
1.54 ihickson 850: var party2 = viewers[event.data.substr(4).split(' ', 1)];
1.36 ihickson 851: if (party2) {
852: var channel = new MessageChannel();
1.84 ihickson 853: party1.port.postMessage('msg ' + party2.name, [channel.port1]);
854: party2.port.postMessage('msg ' + party1.name, [channel.port2]);
1.36 ihickson 855: }
856: break;
857: }
1.155 ihickson 858: }</pre><p><strong>Connecting to multiple pages</strong>. The script uses
1.115 ihickson 859: the <code title="handler-SharedWorkerGlobalScope-onconnect"><a href="#handler-sharedworkerglobalscope-onconnect">onconnect</a></code>
1.155 ihickson 860: event listener to listen for multiple connections.<p><strong>Direct channels</strong>. When the worker receives a
1.81 ihickson 861: "msg" message from one viewer naming another viewer, it sets up a
862: direct connection between the two, so that the two viewers can
863: communicate directly without the worker having to proxy all the
1.238 ihickson 864: 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 865: performance is to split computationally expensive tasks amongst
866: multiple workers. In this example, a computationally expensive task
867: that is to be performed for every number from 1 to 10,000,000 is
1.155 ihickson 868: farmed out to ten subworkers.<p>The main page is as follows, it just reports the result:<pre><!DOCTYPE HTML>
1.81 ihickson 869: <html>
870: <head>
1.203 ihickson 871: <title>Worker example: Multicore computation</title>
1.81 ihickson 872: </head>
873: <body>
1.203 ihickson 874: <p>Result: <output id="result"></output></p>
1.81 ihickson 875: <script>
1.50 ihickson 876: var worker = new Worker('worker.js');
877: worker.onmessage = function (event) {
1.54 ihickson 878: document.getElementById('result').textContent = event.data;
1.40 ihickson 879: };
1.81 ihickson 880: </script>
881: </body>
1.155 ihickson 882: </html></pre><p>The worker itself is as follows:<pre>// settings
1.40 ihickson 883: var num_workers = 10;
884: var items_per_worker = 1000000;
885:
886: // start the workers
887: var result = 0;
888: var pending_workers = num_workers;
889: for (var i = 0; i < num_workers; i += 1) {
1.50 ihickson 890: var worker = new Worker('core.js');
891: worker.postMessage(i * items_per_worker);
892: worker.postMessage((i+1) * items_per_worker);
893: worker.onmessage = storeResult;
1.40 ihickson 894: }
895:
896: // handle the results
897: function storeResult(event) {
1.54 ihickson 898: result += 1*event.data;
1.40 ihickson 899: pending_workers -= 1;
900: if (pending_workers <= 0)
1.50 ihickson 901: postMessage(result); // finished!
1.155 ihickson 902: }</pre><p>It consists of a loop to start the subworkers, and then a handler
903: that waits for all the subworkers to respond.<p>The subworkers are implemented as follows:<pre>var start;
1.41 ihickson 904: onmessage = getStart;
1.40 ihickson 905: function getStart(event) {
1.54 ihickson 906: start = 1*event.data;
1.40 ihickson 907: onmessage = getEnd;
908: }
909:
910: var end;
911: function getEnd(event) {
1.54 ihickson 912: end = 1*event.data;
1.40 ihickson 913: onmessage = null;
1.66 ihickson 914: work();
1.40 ihickson 915: }
916:
1.66 ihickson 917: function work() {
1.40 ihickson 918: var result = 0;
919: for (var i = start; i < end; i += 1) {
920: // perform some complex calculation here
921: result += 1;
922: }
1.50 ihickson 923: postMessage(result);
924: close();
1.155 ihickson 925: }</pre><p>They receive two numbers in two events, perform the computation
1.81 ihickson 926: for the range of numbers thus specified, and then report the result
1.303 ihickson 927: 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
928: URL to that file as its only argument; a worker is then created and
929: 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
930: scenes, and thus support all the same features, such as sending
931: structured data, transferring binary data, and transferring other
932: 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
933: handler IDL attributes">event handler IDL attribute</span> on the
934: <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
935: dedicated workers has its <span>port message queue</span> implicitly
936: enabled when it is created, so there is no equivanet to the
937: <code><a href="#messageport">MessagePort</a></code> interface's <code title="dom-MessagePort-start">start()</code> method on the
938: <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.
939: Structured data can be sent over this communication channel. To send
940: <code>ArrayBuffer</code> objects efficiently (by transferring them
941: rather than cloning them), list them in an array in the second
942: argument.<pre>worker.postMessage({
943: operation: 'find-edges',
944: input: buffer, // an ArrayBuffer object
945: threshold: 0.6,
946: }, [buffer]);</pre><p>To receive a message inside the worker, the <code title="handler-DedicatedWorkerGlobalScope-onmessage"><a href="#handler-dedicatedworkerglobalscope-onmessage">onmessage</a></code>
947: <span title="event handler IDL attributes">event handler IDL
948: attribute</span> is used.<pre>onmessage = function (event) { ... };</pre><p>You can again also use the <code title="dom-EventTarget-addEventListener">addEventListener()</code>
949: 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>.
950: 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
951: URL of the script used to create it, or by explicit name. When
952: created by name, the URL used by the first page to create the worker
953: with that name is the URL of the script that will be used for that
954: worker. This allows multiple applications on a domain to all use a
955: single shared worker to provide a common service, without the
956: applications having to keep track of a common URL for the script
957: used to provide the service.<p class="note">In either case, shared workers are scoped by
958: <span>origin</span>. Two different sites using the same names will
959: not collide.<p>Creating shared workers is done using the <code title="dom-SharedWorker"><a href="#dom-sharedworker">SharedWorker()</a></code> constructor. This
960: constructor takes the URL to the script to use for its first
961: argument, and the name of the worker, if any, as the second
962: argument.<pre>var worker = new SharedWorker('service.js');</pre><p>Communicating with shared workers is done with explicit
963: <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
964: 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) { ... };
965: worker.port.postMessage('some message');
966: worker.port.postMessage({ foo: 'structured'; bar: ['data', 'also', 'possible']});</pre><p>Inside the shared worker, new clients of the worker are announced
967: using the <code title="event-connect">connect</code> event. The port
968: for the new client is given by the event object's <code title="dom-messageevent-ports">ports</code> array as its first (and
969: only) value.<pre>onconnect = function (event) {
970: var newPort = event.ports[0];
971: // set up a listener
972: newPort.onmessage = function (event) { ... };
973: // send a message back to the port
974: newPort.postMessage('ready!'); // can also send structured data, of course
975: };</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 976: non-normative, as are all sections explicitly marked non-normative.
1.281 ihickson 977: Everything else in this specification is normative.<p>The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
1.81 ihickson 978: "OPTIONAL" in the normative parts of this document are to be
979: interpreted as described in RFC2119. For readability, these words do
1.155 ihickson 980: 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 981: (such as "strip any leading space characters" or "return false and
982: abort these steps") are to be interpreted with the meaning of the
983: key word ("must", "should", "may", etc) used in introducing the
1.155 ihickson 984: algorithm.<p>Some conformance requirements are phrased as requirements on
1.81 ihickson 985: attributes, methods or objects. Such requirements are to be
1.155 ihickson 986: interpreted as requirements on user agents.<p>Conformance requirements phrased as algorithms or specific steps
1.81 ihickson 987: may be implemented in any manner, so long as the end result is
988: equivalent. (In particular, the algorithms defined in this
989: specification are intended to be easy to follow, and not intended to
1.155 ihickson 990: be performant.)<p>The only conformance class defined by this specification is user
991: agents.<p>User agents may impose implementation-specific limits on
1.81 ihickson 992: otherwise unconstrained inputs, e.g. to prevent denial of service
993: attacks, to guard against running out of memory, or to work around
1.229 ihickson 994: platform-specific limitations.<p>When support for a feature is disabled (e.g. as an emergency
995: measure to mitigate a security problem, or to aid in development, or
996: for performance reasons), user agents must act as if they had no
997: support for the feature whatsoever, and as if the feature was not
998: mentioned in this specification. For example, if a particular
999: feature is accessed via an attribute in a Web IDL interface, the
1000: attribute itself would be omitted from the objects that implement
1001: that interface — leaving the attribute on the object but
1002: 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 1003: specifications.<dl><dt>HTML</dt>
1.49 ihickson 1004:
1.81 ihickson 1005: <dd>
1.49 ihickson 1006:
1.226 ihickson 1007: <p>Many fundamental concepts from HTML are used by this
1008: specification. <a href="#refsHTML">[HTML]</a></p>
1.49 ihickson 1009:
1.81 ihickson 1010: </dd>
1.1 ihickson 1011:
1.81 ihickson 1012: <dt>WebIDL</dt>
1.1 ihickson 1013:
1014: <dd>
1015:
1.81 ihickson 1016: <p>The IDL blocks in this specification use the semantics of the
1.153 ihickson 1017: WebIDL specification. <a href="#refsWEBIDL">[WEBIDL]</a></p>
1.1 ihickson 1018:
1.81 ihickson 1019: </dd>
1.1 ihickson 1020:
1.155 ihickson 1021: </dl><h2 id="terminology"><span class="secno">3 </span>Terminology</h2><p>The construction "a <code title="">Foo</code> object", where
1.81 ihickson 1022: <code title="">Foo</code> is actually an interface, is sometimes
1023: used instead of the more accurate "an object implementing the
1.155 ihickson 1024: interface <code title="">Foo</code>".<p>The term DOM is used to refer to the API set made available to
1.81 ihickson 1025: scripts in Web applications, and does not necessarily imply the
1026: existence of an actual <code>Document</code> object or of any other
1027: <code>Node</code> objects as defined in the DOM Core
1.171 ihickson 1028: specifications. <a href="#refsDOMCORE">[DOMCORE]</a><p>An IDL attribute is said to be <em>getting</em> when its value is
1.81 ihickson 1029: being retrieved (e.g. by author script), and is said to be
1.155 ihickson 1030: <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 1031: the official term ECMAScript, since the term JavaScript is more
1.155 ihickson 1032: 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 1033: workers. Dedicated workers, once created, and are linked to their
1034: creator; but message ports can be used to communicate from a
1035: dedicated worker to multiple other browsing contexts or
1036: workers. Shared workers, on the other hand, are named, and once
1037: created any script running in the same <span>origin</span> can
1.301 ihickson 1038: 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
1.302 ihickson 1039: 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-abstract-interface"><span class="secno">4.2.1 </span>The <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> abstract interface</h4><pre class="idl">interface <dfn id="workerglobalscope">WorkerGlobalScope</dfn> : <span>EventTarget</span> {
1.115 ihickson 1040: readonly attribute <a href="#workerglobalscope">WorkerGlobalScope</a> <a href="#dom-workerglobalscope-self" title="dom-WorkerGlobalScope-self">self</a>;
1041: readonly attribute <a href="#workerlocation">WorkerLocation</a> <a href="#dom-workerglobalscope-location" title="dom-WorkerGlobalScope-location">location</a>;
1042:
1043: void <a href="#dom-workerglobalscope-close" title="dom-WorkerGlobalScope-close">close</a>();
1.308 ihickson 1044: [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-workerglobalscope-onerror" title="handler-WorkerGlobalScope-onerror">onerror</a>;
1045: [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-workerglobalscope-onoffline" title="handler-WorkerGlobalScope-onoffline">onoffline</a>;
1046: [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-workerglobalscope-ononline" title="handler-WorkerGlobalScope-ononline">ononline</a>;
1.150 ihickson 1047: };
1.302 ihickson 1048: <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 1049: 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 1050: attribute must return the <code><a href="#workerlocation">WorkerLocation</a></code> object created
1051: for the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object when the worker was
1.81 ihickson 1052: created. It represents the <span>absolute URL</span> of the script
1.155 ihickson 1053: 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 1054: method on a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, the user agent
1.155 ihickson 1055: must run the following steps (atomically):<ol><li><p>Discard any <span title="concept-task">tasks</span> that
1.123 ihickson 1056: have been added to the <span>event loop</span>'s <span title="task
1057: queue">task queues</span>.</p>
1058:
1.81 ihickson 1059:
1.115 ihickson 1060: <li><p>Set the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's
1061: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.123 ihickson 1062: true. (This prevents any further tasks from being queued.)</li>
1.81 ihickson 1063:
1.177 ihickson 1064: </ol><p>The following are the <span>event handlers</span> (and their
1065: corresponding <span title="event handler event type">event handler
1066: event types</span>) that must be supported, as IDL attributes, by
1067: objects implementing the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1068: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.281 ihickson 1069: <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 1070: <tr><td><dfn id="handler-workerglobalscope-onoffline" title="handler-WorkerGlobalScope-onoffline"><code>onoffline</code></dfn> <td> <code title="event-offline">offline</code>
1071: <tr><td><dfn id="handler-workerglobalscope-ononline" title="handler-WorkerGlobalScope-ononline"><code>ononline</code></dfn> <td> <code title="event-online">online</code>
1.209 ihickson 1072: </table><hr><p>The <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> interface must not exist if
1073: the interface's <span>relevant namespace object</span> is a
1.301 ihickson 1074: <code>Window</code> object. <a href="#refsWEBIDL">[WEBIDL]</a><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">[Supplemental, NoInterfaceObject]
1.150 ihickson 1075: interface <dfn id="dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</dfn> : <a href="#workerglobalscope">WorkerGlobalScope</a> {
1.308 ihickson 1076: void <a href="#dom-dedicatedworkerglobalscope-postmessage" title="dom-DedicatedWorkerGlobalScope-postMessage">postMessage</a>(any message, optional sequence<<span>Transferable</span>> transfer); [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-dedicatedworkerglobalscope-onmessage" title="handler-DedicatedWorkerGlobalScope-onmessage">onmessage</a>;
1.155 ihickson 1077: };</pre><p><code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> objects act as if they
1.301 ihickson 1078: had an implicit <code><a href="#messageport">MessagePort</a></code> associated with them. This
1.81 ihickson 1079: port is part of a channel that is set up when the worker is created,
1080: but it is not exposed. This object must never be garbage collected
1.155 ihickson 1081: before the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object.<p>All messages received by that port must immediately be retargeted
1.281 ihickson 1082: at the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object.<p>The <dfn id="dom-dedicatedworkerglobalscope-postmessage" title="dom-DedicatedWorkerGlobalScope-postMessage"><code>postMessage()</code></dfn> method on
1.115 ihickson 1083: <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> objects must act as if, when
1.281 ihickson 1084: invoked, it immediately invoked the
1.81 ihickson 1085: method of the same name on the port, with the same arguments, and
1.177 ihickson 1086: returned the same return value.<p>The following are the <span>event handlers</span> (and their
1087: corresponding <span title="event handler event type">event handler
1088: event types</span>) that must be supported, as IDL attributes, by
1089: objects implementing the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
1090: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1091: <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 1092: </table><p>For the purposes of the <span>application cache</span> networking
1093: model, a dedicated worker is an extension of the <span>cache
1.301 ihickson 1094: 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">[Supplemental, NoInterfaceObject]
1.150 ihickson 1095: interface <dfn id="sharedworkerglobalscope">SharedWorkerGlobalScope</dfn> : <a href="#workerglobalscope">WorkerGlobalScope</a> {
1.115 ihickson 1096: readonly attribute DOMString <a href="#dom-sharedworkerglobalscope-name" title="dom-SharedWorkerGlobalScope-name">name</a>;
1.181 ihickson 1097: readonly attribute <span>ApplicationCache</span> <span title="dom-SharedWorkerGlobalScope-applicationCache">applicationCache</span>;
1.308 ihickson 1098: [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-sharedworkerglobalscope-onconnect" title="handler-SharedWorkerGlobalScope-onconnect">onconnect</a>;
1.155 ihickson 1099: };</pre><p>Shared workers receive message ports through <code title="event-WorkerGlobalScope-connect">connect</code> events on
1100: their global object for each connection.<p>The <dfn id="dom-sharedworkerglobalscope-name" title="dom-SharedWorkerGlobalScope-name"><code>name</code></dfn>
1.81 ihickson 1101: attribute must return the value it was assigned when the
1.115 ihickson 1102: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object was created by the
1103: "<a href="#run-a-worker">run a worker</a>" algorithm. Its value represents the name
1.81 ihickson 1104: that can be used to obtain a reference to the worker using the
1.177 ihickson 1105: <code><a href="#sharedworker">SharedWorker</a></code> constructor.<p>The following are the <span>event handlers</span> (and their
1106: corresponding <span title="event handler event type">event handler
1107: event types</span>) that must be supported, as IDL attributes, by
1108: objects implementing the <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1109: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1110: <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 1111: </table><p>For the purposes of the <span>application cache</span> networking
1112: model, a shared worker is its own <span>cache host</span>. The
1113: <a href="#run-a-worker">run a worker</a> algorithm takes care of associating the
1114: worker with an <span>application cache</span>.<p class="note">The <code title="dom-SharedWorkerGlobalScope-applicationCache">applicationCache</code>
1.123 ihickson 1115: attribute returns the <code>ApplicationCache</code> object for the
1.301 ihickson 1116: 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 1117: origin</span> of scripts running in workers are the
1118: <span>origin</span> of the <span>absolute URL</span> given in that
1.115 ihickson 1119: the worker's <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1.301 ihickson 1120: 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 1121: loop</span> distinct from those defined for <span title="unit of
1122: related similar-origin browsing contexts">units of related
1123: similar-origin browsing contexts</span>. This <span>event
1124: loop</span> has no associated <span>browsing context</span>, and its
1125: <span title="task queue">task queues</span> only have events,
1126: callbacks, and networking activity as <span title="concept-task">tasks</span>. The processing model of these
1127: <span title="event loop">event loops</span> is defined below in the
1.155 ihickson 1128: <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 1129: initially be false, but which can get set to true by the algorithms
1.155 ihickson 1130: 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 1131: true, the <span>event loop</span>'s <span title="task queue">task
1.115 ihickson 1132: queues</span> must discard any further <span title="concept-task">tasks</span> that would be added to them (tasks
1.175 ihickson 1133: already on the queue are unaffected except where otherwise
1.115 ihickson 1134: specified). Effectively, once the <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is true,
1.81 ihickson 1135: timers stop firing, notifications for all pending asynchronous
1.301 ihickson 1136: 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
1137: <code><a href="#messageport">MessagePort</a></code> objects.<p>Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> <var title="">worker global
1.124 ihickson 1138: scope</var> has a list of <dfn id="the-worker-s-ports">the worker's ports</dfn>, which
1.301 ihickson 1139: consists of all the <code><a href="#messageport">MessagePort</a></code> objects that are
1.81 ihickson 1140: entangled with another port and that have one (but only one) port
1141: owned by <var title="">worker global scope</var>. This list includes
1.281 ihickson 1142: the implicit
1.301 ihickson 1143: <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 1144: worker's workers</dfn>. Initially this list is empty; it is
1.155 ihickson 1145: 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 1146: <dfn id="the-worker-s-documents">the worker's <code>Document</code>s</dfn>. Initially this list
1.155 ihickson 1147: 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 1148: worker's <code>Document</code>s</dfn>, the user agent must, for each
1.124 ihickson 1149: worker in the list of <a href="#the-worker-s-workers">the worker's workers</a> whose list
1150: of <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> does not contain
1151: <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 1152: documents">add <var title="">d</var> to <var title="">q</var>'s
1153: <code>WorkerGlobalScope</code> owner's list of <span>the worker's
1.281 ihickson 1154: <code>Document</code>s</span></a>.</p><p>Whenever a <code>Document</code> object is <span title="discard a
1.123 ihickson 1155: Document">discarded</span>, it must be removed from the list of
1156: <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> of each worker
1.192 ihickson 1157: whose list contains that <code>Document</code>.<p>Given a <span>script's global object</span> <var title="">o</var>
1.123 ihickson 1158: when creating or obtaining a worker, the <dfn id="list-of-relevant-document-objects-to-add">list of relevant
1159: <code>Document</code> objects to add</dfn> depends on the type of
1160: <var title="">o</var>. If <var title="">o</var> is a
1161: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object (i.e. if we are creating a
1162: nested worker), then the relevant <code>Document</code>s are the
1163: <code>Document</code>s that are in <var title="">o</var>'s own list
1164: 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
1165: <code>Document</code> is just the <code>Document</code> that is the
1.155 ihickson 1166: <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 1167: list of <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> is not
1.155 ihickson 1168: empty.<p>A worker is said to be a <dfn id="protected-worker">protected worker</dfn> if it is a
1.123 ihickson 1169: <a href="#permissible-worker">permissible worker</a> and either it has outstanding
1170: timers, database transactions, or network connections, or its list
1.124 ihickson 1171: of <a href="#the-worker-s-ports">the worker's ports</a> is not empty, or its
1.123 ihickson 1172: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> is actually a
1173: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object (i.e. the worker is a
1.155 ihickson 1174: shared worker).<p>A worker is said to be an <dfn id="active-needed-worker">active needed worker</dfn> if any
1.123 ihickson 1175: of the <code>Document</code> objects in <a href="#the-worker-s-documents">the worker's
1.155 ihickson 1176: <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 1177: not an <a href="#active-needed-worker">active needed worker</a> but it is a
1.301 ihickson 1178: <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 1179: <span>URL</span> <var title="">url</var>, a <span>browsing
1180: context</span> <var title="">owner browsing context</var>, a
1181: <code>Document</code> <var title="">owner document</var>, an
1182: <span>origin</span> <var title="">owner origin</var>, and with
1183: global scope <var title="">worker global scope</var>, it must run
1184: the following steps:<ol><li>
1.81 ihickson 1185:
1.274 ihickson 1186: <p>Create a separate parallel execution environment (i.e. a
1187: separate thread or process or equivalent construct), and run the
1188: rest of these steps asynchronously in that context.</p>
1.81 ihickson 1189:
1190: </li>
1.4 ihickson 1191:
1.101 ihickson 1192: <li><p>If <var title="">worker global scope</var> is actually a
1.115 ihickson 1193: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object (i.e. the worker is a
1.101 ihickson 1194: shared worker), and there are any <span title="relevant application
1195: cache">relevant application caches</span> that are identified by a
1196: 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 1197: their entries, <em>not</em> excluding entries marked as <span title="concept-appcache-foreign">foreign</span>, then associate the
1198: <var title="">worker global scope</var> with the <span title="concept-appcache-selection">most appropriate application
1.101 ihickson 1199: cache</span> of those that match.</li>
1200:
1.4 ihickson 1201: <li>
1.52 ihickson 1202:
1.256 ihickson 1203: <p>Attempt to <span>fetch</span> the resource identified by <var title="">url</var>, from the <var title="">owner origin</var>,
1204: with the <i>synchronous flag</i> set and the <i>force same-origin
1.281 ihickson 1205: flag</i> set.</p>
1.256 ihickson 1206: <p>If the attempt fails, then for each <code><a href="#worker">Worker</a></code> or
1207: <code><a href="#sharedworker">SharedWorker</a></code> object associated with <var title="">worker global scope</var>, <span>queue a task</span> to
1208: <span>fire a simple event</span> named <code title="event-error">error</code> at that object. Abort these
1209: steps.</p>
1.7 ihickson 1210:
1.264 ihickson 1211: <p>If the attempt succeeds, then let <var title="">source</var> be
1212: the script resource <span>decoded as UTF-8, with error
1213: handling</span>.
1214:
1215: <a href="#refsHTML">[HTML]</a>
1216:
1217: </p>
1.81 ihickson 1218:
1.68 ihickson 1219: <p>Let <var title="">language</var> be JavaScript.</p>
1.7 ihickson 1220:
1.115 ihickson 1221: <p class="note">As with <code>script</code> elements, the MIME
1.81 ihickson 1222: type of the script is ignored. Unlike with <code>script</code>
1223: elements, there is no way to override the type. It's always
1.170 ihickson 1224: assumed to be JavaScript.</p>
1.81 ihickson 1225:
1226: </li>
1.7 ihickson 1227:
1228: <li>
1.68 ihickson 1229:
1.115 ihickson 1230: <p>A new <span title="concept-script">script</span> is now
1.81 ihickson 1231: created, as follows.</p>
1232:
1233: <p>Create a new <span>script execution environment</span>
1234: set up as appropriate for the scripting language <var title="">language</var>.</p>
1.34 ihickson 1235:
1.68 ihickson 1236: <p>Parse/compile/initialize <var title="">source</var> using that
1.81 ihickson 1237: <span>script execution environment</span>, as appropriate for <var title="">language</var>, and thus obtain a <span>list of code
1238: entry-points</span>; set the <i>initial code entry-point</i> to
1239: the entry-point for any executable code to be immediately run.</p>
1240:
1241: <p>Set the <span>script's global object</span> to <var title="">worker global scope</var>.</p>
1242:
1243: <p>Set the <span>script's browsing context</span> to <var title="">owner browsing context</var>.</p>
1244:
1.232 ihickson 1245: <p>Set the <span>script's document</span> to <var title="">owner
1246: document</var>.</p>
1247:
1.83 ihickson 1248: <p>Set the <span>script's URL character encoding</span> to
1.81 ihickson 1249: UTF-8. (This is just used for encoding non-ASCII characters in the
1250: query component of URLs.)</p>
1.68 ihickson 1251:
1252: <p>Set the <span>script's base URL</span> to <var title="">url</var>.</p>
1.4 ihickson 1253:
1.81 ihickson 1254: </li>
1.4 ihickson 1255:
1256: <li>
1.81 ihickson 1257:
1258: <p><strong>Closing orphan workers</strong>: Start monitoring the
1.125 ihickson 1259: worker such that no sooner than it stops being either a
1260: <a href="#protected-worker">protected worker</a> or a <a href="#suspendable-worker">suspendable
1.123 ihickson 1261: worker</a>, and no later than it stops being a
1262: <a href="#permissible-worker">permissible worker</a>, <var title="">worker global
1263: scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is set
1.281 ihickson 1264: to true.</p>
1.81 ihickson 1265:
1266: </li>
1.9 ihickson 1267:
1268: <li>
1.7 ihickson 1269:
1.81 ihickson 1270: <p><strong>Suspending workers</strong>: Start monitoring the
1271: worker, such that whenever <var title="">worker global
1.115 ihickson 1272: scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is false
1273: and the worker is a <a href="#suspendable-worker">suspendable worker</a>, the user
1.81 ihickson 1274: agent suspends execution of script in that worker until such time
1.115 ihickson 1275: as either the <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag switches
1276: to true or the worker stops being a <a href="#suspendable-worker">suspendable
1.81 ihickson 1277: worker</a>.</p>
1.4 ihickson 1278:
1.81 ihickson 1279: </li>
1.68 ihickson 1280:
1281: <li>
1.4 ihickson 1282:
1.81 ihickson 1283: <p><span title="jump to a code entry-point">Jump</span> to the
1.115 ihickson 1284: <span title="concept-script">script</span>'s <i>initial code
1.81 ihickson 1285: entry-point</i>, and let that run until it either returns, fails
1286: to catch an exception, or gets prematurely aborted by the
1.115 ihickson 1287: "<a href="#kill-a-worker">kill a worker</a>" or "<a href="#terminate-a-worker">terminate a worker</a>"
1.81 ihickson 1288: algorithms defined below.</p>
1289:
1.4 ihickson 1290:
1.81 ihickson 1291: </li>
1.4 ihickson 1292:
1.95 ihickson 1293: <li><p>If <var title="">worker global scope</var> is actually a
1.115 ihickson 1294: <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object (i.e. the worker is
1.126 ihickson 1295: a dedicated worker), then enable the <span>port message
1296: queue</span> of the worker's implicit port.</li>
1.95 ihickson 1297:
1.4 ihickson 1298: <li>
1.68 ihickson 1299:
1.115 ihickson 1300: <p><i title="">Event loop</i>: Wait until either there is a <span title="concept-task">task</span> in one of the <span>event
1301: 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 1302: to true.</p>
1.43 ihickson 1303:
1.81 ihickson 1304: </li>
1.4 ihickson 1305:
1306: <li>
1307:
1.81 ihickson 1308: <p>Run the oldest task on one of the <span>event loop</span>'s
1309: <span title="task queue">task queues</span>, if any. The user
1310: agent may pick any <span>task queue</span>.</p>
1311:
1.115 ihickson 1312: <p class="note">The handling of events or the execution of
1313: callbacks might get prematurely aborted by the "<a href="#kill-a-worker">kill a
1314: worker</a>" or "<a href="#terminate-a-worker">terminate a worker</a>" algorithms
1.81 ihickson 1315: defined below.</p>
1.8 ihickson 1316:
1.81 ihickson 1317: </li>
1.4 ihickson 1318:
1319: <li>
1320:
1.248 ihickson 1321: <p>If the <span>storage mutex</span> is now owned by the worker's
1322: <span>event loop</span>, release it so that it is once again
1323: free.</p>
1324:
1325: </li>
1326:
1327: <li>
1328:
1329: <p>Remove the task just run in the earlier step, if any, from its
1.81 ihickson 1330: <span>task queue</span>.</p>
1.4 ihickson 1331:
1.81 ihickson 1332: </li>
1.4 ihickson 1333:
1334: <li>
1.8 ihickson 1335:
1.81 ihickson 1336: <p>If there are any more events in the <span>event loop</span>'s
1.115 ihickson 1337: <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 1338: to false, then jump back to the step above labeled <i>event
1339: loop</i>.</p>
1.8 ihickson 1340:
1.81 ihickson 1341: </li>
1.8 ihickson 1342:
1343: <li>
1.71 ihickson 1344:
1.123 ihickson 1345: <p>Empty the <var title="">worker global scope</var>'s <span>list
1346: of active timeouts</span> and its <span>list of active
1347: intervals</span>.</p>
1.50 ihickson 1348:
1.81 ihickson 1349: </li>
1.50 ihickson 1350:
1.247 ihickson 1351: <li>
1352:
1353: <p>Disentangle all the ports in the list of <a href="#the-worker-s-ports">the worker's
1354: ports</a>.</p>
1355:
1356: </li>
1357:
1.155 ihickson 1358: </ol><hr><p>When a user agent is to <dfn id="kill-a-worker">kill a worker</dfn> it must
1.81 ihickson 1359: run the following steps in parallel with the worker's main loop (the
1.281 ihickson 1360: "<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 1361: true.</li>
1362:
1363:
1.115 ihickson 1364: <li><p>If there are any <span title="concept-task">tasks</span>
1.81 ihickson 1365: queued in the <span>event loop</span>'s <span title="task
1.281 ihickson 1366: queue">task queues</span>, discard them without processing them.</li>
1367:
1.81 ihickson 1368:
1369: <li><p>Wait a user-agent-defined amount of time.</li>
1370:
1.281 ihickson 1371: <li><p>Abort the script currently running in the worker.</li>
1.81 ihickson 1372:
1.155 ihickson 1373: </ol><p>User agents may invoke the "<a href="#kill-a-worker">kill a worker</a>"
1.81 ihickson 1374: processing model on a worker at any time, e.g. in response to user
1375: requests, in response to CPU quota management, or when a worker
1.115 ihickson 1376: stops being an <a href="#active-needed-worker">active needed worker</a> if the worker
1377: continues executing even after its <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag was
1.155 ihickson 1378: 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 1379: the following steps in parallel with the worker's main loop (the
1.155 ihickson 1380: "<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 1381: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.81 ihickson 1382: true.</li>
1383:
1.115 ihickson 1384: <li><p>If there are any <span title="concept-task">tasks</span>
1.81 ihickson 1385: queued in the <span>event loop</span>'s <span title="task
1386: queue">task queues</span>, discard them without processing
1387: them.</li>
1388:
1389: <li><p>Abort the script currently running in the worker.</li>
1390:
1.115 ihickson 1391: <li><p>If the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object is
1392: actually a <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object (i.e. the
1.81 ihickson 1393: worker is a dedicated worker), then empty the <span>port message
1394: queue</span> of the port that the worker's implicit port is
1395: entangled with.</li>
1396:
1.155 ihickson 1397: </ol><hr><p>The <span>task source</span> for the tasks mentioned above is the
1.301 ihickson 1398: <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 1399: worker's scripts, if the error did not occur while handling a
1400: previous script error, the user agent must <span>report the
1401: error</span> using the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's <code title="handler-WorkerGlobalScope-onerror"><a href="#handler-workerglobalscope-onerror">onerror</a></code>
1.205 ihickson 1402: attribute.
1403:
1.226 ihickson 1404: <a href="#refsHTML">[HTML]</a>
1.205 ihickson 1405:
1406: <p>For shared workers, if the error is still <i title="concept-error-nothandled">not handled</i> afterwards, or if
1.132 ihickson 1407: the error occurred while handling a previous script error, the error
1.215 ihickson 1408: may be reported to the user.
1.205 ihickson 1409:
1.226 ihickson 1410: <a href="#refsHTML">[HTML]</a>
1.205 ihickson 1411:
1412: <p>For dedicated workers, if the error is still <i title="concept-error-nothandled">not handled</i> afterwards, or if
1.132 ihickson 1413: the error occurred while handling a previous script error, the user
1.292 ihickson 1414: agent must <span>queue a task</span> to fire an event that uses the
1415: <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 1416: 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 1417: appropriately, at the <code><a href="#worker">Worker</a></code> object associated with the
1.307 ihickson 1418: worker. If the event is not canceled, the user agent must act as if
1419: the uncaught runtime script error had occurred in the global scope
1420: that the <code><a href="#worker">Worker</a></code> object is in, thus repeating the entire
1.292 ihickson 1421: runtime script error reporting process one level up.<p>If the implicit port connecting the worker to its
1422: <code><a href="#worker">Worker</a></code> object has been disentangled (i.e. if the parent
1423: worker has been terminated), then the user agent must act as if the
1424: <code><a href="#worker">Worker</a></code> object had no <code title="event-error">error</code> event handler and as if that
1425: worker's <code title="handler-WorkerGlobalScope-onerror"><a href="#handler-workerglobalscope-onerror">onerror</a></code> attribute
1426: was null, but must otherwise act as described above.<p class="note">Thus, error reports proagate up to the chain of
1427: dedicated workers up to the original <code>Document</code>, even if
1428: some of the workers along this chain have been terminated and
1429: garbage collected.<p>The <span>task source</span> for the task mentioned above is the
1.307 ihickson 1430: <span>DOM manipulation task source</span>.<hr><pre class="idl">[Constructor(DOMString type, optional <a href="#erroreventinit">ErrorEventInit</a> eventInitDict)]
1431: interface <dfn id="errorevent">ErrorEvent</dfn> : <span>Event</span> {
1.147 ihickson 1432: readonly attribute DOMString <a href="#dom-errorevent-message" title="dom-ErrorEvent-message">message</a>;
1433: readonly attribute DOMString <a href="#dom-errorevent-filename" title="dom-ErrorEvent-filename">filename</a>;
1.115 ihickson 1434: readonly attribute unsigned long <a href="#dom-errorevent-lineno" title="dom-ErrorEvent-lineno">lineno</a>;
1.307 ihickson 1435: };
1436:
1437: dictionary <dfn id="erroreventinit">ErrorEventInit</dfn> : <span>EventInit</span> {
1438: DOMString message;
1439: DOMString filename;
1440: unsigned long lineno;
1441: };</pre><p>The <dfn id="dom-errorevent-message" title="dom-ErrorEvent-message"><code>message</code></dfn> attribute
1442: must return the value it was initialized to. When the object is
1443: created, this attribute must be initialized to the empty string. It
1444: represents the error message.<p>The <dfn id="dom-errorevent-filename" title="dom-ErrorEvent-filename"><code>filename</code></dfn>
1445: attribute must return the value it was initialized to. When the
1446: object is created, this attribute must be initialized to the empty
1447: string. It represents the <span>absolute URL</span> of the script in
1.155 ihickson 1448: which the error originally occurred.<p>The <dfn id="dom-errorevent-lineno" title="dom-ErrorEvent-lineno"><code>lineno</code></dfn>
1.307 ihickson 1449: attribute must return the value it was initialized to. When the
1450: object is created, this attribute must be initialized to zero. It
1451: represents the line number where the error occurred in the
1.301 ihickson 1452: 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">[Supplemental, NoInterfaceObject]
1.302 ihickson 1453: interface <dfn id="abstractworker">AbstractWorker</dfn> : <span>EventTarget</span> {
1.308 ihickson 1454: [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-abstractworker-onerror" title="handler-AbstractWorker-onerror">onerror</a>;
1.302 ihickson 1455: };</pre><p>The following are the <span>event handlers</span> (and their
1.177 ihickson 1456: corresponding <span title="event handler event type">event handler
1457: event types</span>) that must be supported, as IDL attributes, by
1458: 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 1459: <tbody><tr><td><dfn id="handler-abstractworker-onerror" title="handler-AbstractWorker-onerror"><code>onerror</code></dfn> <td> <code title="event-error">error</code>
1.306 ihickson 1460: </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)]
1.115 ihickson 1461: interface <dfn id="worker">Worker</dfn> : <a href="#abstractworker">AbstractWorker</a> {
1462: void <a href="#dom-worker-terminate" title="dom-Worker-terminate">terminate</a>();
1.50 ihickson 1463:
1.308 ihickson 1464: void <a href="#dom-worker-postmessage" title="dom-Worker-postMessage">postMessage</a>(any message, optional sequence<<span>Transferable</span>> transfer); [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-worker-onmessage" title="handler-Worker-onmessage">onmessage</a>;
1.155 ihickson 1465: };</pre><p>The <dfn id="dom-worker-terminate" title="dom-Worker-terminate"><code>terminate()</code></dfn> method,
1.115 ihickson 1466: when invoked, must cause the "<a href="#terminate-a-worker">terminate a worker</a>"
1.81 ihickson 1467: algorithm to be run on the worker with with the object is
1.155 ihickson 1468: associated.<p><code><a href="#worker">Worker</a></code> objects act as if they had an implicit
1.301 ihickson 1469: <code><a href="#messageport">MessagePort</a></code> associated with them. This port is part of
1.81 ihickson 1470: a channel that is set up when the worker is created, but it is not
1471: exposed. This object must never be garbage collected before the
1.155 ihickson 1472: <code><a href="#worker">Worker</a></code> object.<p>All messages received by that port must immediately be retargeted
1.281 ihickson 1473: at the <code><a href="#worker">Worker</a></code> object.<p>The <dfn id="dom-worker-postmessage" title="dom-Worker-postMessage"><code>postMessage()</code></dfn> method on <code><a href="#worker">Worker</a></code> objects
1474: must act as if, when invoked, it
1.81 ihickson 1475: immediately invoked the method of the same name on the port, with
1.177 ihickson 1476: the same arguments, and returned the same return value.<p>The following are the <span>event handlers</span> (and their
1477: corresponding <span title="event handler event type">event handler
1478: event types</span>) that must be supported, as IDL attributes, by
1479: 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 1480: <tbody><tr><td><dfn id="handler-worker-onmessage" title="handler-Worker-onmessage"><code>onmessage</code></dfn> <td> <code title="event-message">message</code>
1481: </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 1482: 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 1483: script</span>'s <span title="script's base URL">base URL</span>,
1484: when the method is invoked.</li>
1.9 ihickson 1485:
1.309 ihickson 1486: <li><p>If this fails, throw a <code>SyntaxError</code>
1.81 ihickson 1487: exception.</li>
1.9 ihickson 1488:
1.167 ihickson 1489: <li>
1490:
1491: <p>If the <span>origin</span> of the resulting <span>absolute
1492: URL</span> is not the <span title="same origin">same</span> as the
1.216 ihickson 1493: origin of the <span>entry script</span>, then throw a
1.309 ihickson 1494: <code>SecurityError</code> exception.</p>
1.167 ihickson 1495:
1496: <p class="note">Thus, scripts must be external files with the same
1.269 ihickson 1497: scheme as the original page: you can't load a script from a <span title="data protocol"><code title="">data:</code> URL</span> or
1498: <span title="javascript protocol"><code title="">javascript:</code> URL</span>, and an <code>http:</code>
1499: page couldn't start workers using scripts with <code>http:</code>
1500: URLs.</p>
1.167 ihickson 1501:
1502: </li>
1.9 ihickson 1503:
1.185 ihickson 1504: <li><p>Create a new <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
1505: object. Let <var title="">worker global scope</var> be this new
1506: object.</li>
1.9 ihickson 1507:
1.115 ihickson 1508: <li><p>Create a new <code><a href="#worker">Worker</a></code> object, associated with
1.81 ihickson 1509: <var title="">worker global scope</var>. Let <var title="">worker</var> be this new object.</li>
1.50 ihickson 1510:
1.301 ihickson 1511: <li><p><span>Create a new <code><a href="#messageport">MessagePort</a></code> object</span>
1.192 ihickson 1512: owned by the <span title="script's global object">global
1513: object</span> of the <span title="concept-script">script</span> that
1.185 ihickson 1514: invoked the constructor. Let this be the <var title="">outside
1.81 ihickson 1515: port</var>.</li>
1.9 ihickson 1516:
1.81 ihickson 1517: <li><p>Associate the <var title="">outside port</var> with <var title="">worker</var>.</li>
1.50 ihickson 1518:
1.301 ihickson 1519: <li><p><span>Create a new <code><a href="#messageport">MessagePort</a></code> object</span>
1.185 ihickson 1520: owned by <var title="">worker global scope</var>. Let <var title="">inside port</var> be this new object.</li>
1.50 ihickson 1521:
1.81 ihickson 1522: <li><p>Associate <var title="">inside port</var> with <var title="">worker global scope</var>.</li>
1.50 ihickson 1523:
1.81 ihickson 1524: <li><p><span>Entangle</span> <var title="">outside port</var> and
1525: <var title="">inside port</var>.</li>
1.50 ihickson 1526:
1.81 ihickson 1527: <li><p>Return <var title="">worker</var>, and run the following
1528: steps asynchronously.</li>
1.50 ihickson 1529:
1530:
1.126 ihickson 1531: <li><p>Enable <var title="">outside port</var>'s <span>port message
1.81 ihickson 1532: queue</span>.</li>
1.50 ihickson 1533:
1534: <li>
1.51 ihickson 1535:
1.123 ihickson 1536: <p>Let <var title="">docs</var> be the <a href="#list-of-relevant-document-objects-to-add">list of relevant
1.192 ihickson 1537: <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 1538: constructor.</p>
1539:
1540: </li>
1541:
1542: <li>
1543:
1544: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1545: <var title="">worker global scope</var>'s list of <span>the
1546: worker's <code>Document</code>s</span></a> the
1547: <code>Document</code> objects in <var title="">docs</var>.</p>
1548:
1549: </li>
1550:
1551: <li>
1552:
1.192 ihickson 1553: <p>If the <span title="script's global object">global object</span>
1.124 ihickson 1554: of the <span title="concept-script">script</span> that invoked the
1555: constructor is a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object (i.e. we
1556: are creating a nested worker), add <var title="">worker global
1557: scope</var> to the list of <a href="#the-worker-s-workers">the worker's workers</a> of the
1.192 ihickson 1558: <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 1559: constructor.</p>
1560:
1561: </li>
1562:
1563: <li>
1564:
1.115 ihickson 1565: <p><a href="#run-a-worker">Run a worker</a> for the resulting <span>absolute
1.193 ihickson 1566: URL</span>, with the <span>script's browsing context</span> of the
1.81 ihickson 1567: script that invoked the method as the <var title="">owner browsing
1.232 ihickson 1568: context</var>, with the <span>script's document</span> of the
1569: script that invoked the method as the <var title="">owner
1570: document</var>, with the <span>origin</span> of the <span>entry
1.176 ihickson 1571: script</span> as the <var title="">owner origin</var>, and with
1572: <var title="">worker global scope</var> as the global scope.</p>
1.9 ihickson 1573:
1.81 ihickson 1574: </li>
1.4 ihickson 1575:
1.155 ihickson 1576: </ol><p>This constructor must be visible when the <span>script's global
1.192 ihickson 1577: object</span> is either a <code>Window</code> object or an object
1.306 ihickson 1578: 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)]
1.115 ihickson 1579: interface <dfn id="sharedworker">SharedWorker</dfn> : <a href="#abstractworker">AbstractWorker</a> {
1.301 ihickson 1580: readonly attribute <a href="#messageport">MessagePort</a> <a href="#dom-sharedworker-port" title="dom-SharedWorker-port">port</a>;
1.155 ihickson 1581: };</pre><p>The <dfn id="dom-sharedworker-port" title="dom-SharedWorker-port"><code>port</code></dfn>
1.81 ihickson 1582: attribute must return the value it was assigned by the object's
1.301 ihickson 1583: constructor. It represents the <code><a href="#messageport">MessagePort</a></code> for
1.155 ihickson 1584: 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 1585: constructor is invoked, the user agent must run the following
1.155 ihickson 1586: steps:<ol><li><p><span title="resolve a url">Resolve</span> the <var title="">scriptURL</var> argument.</li>
1.81 ihickson 1587:
1.309 ihickson 1588: <li><p>If this fails, throw a <code>SyntaxError</code>
1.81 ihickson 1589: exception.</li>
1590:
1.159 ihickson 1591: <li><p>Otherwise, let <var title="">scriptURL</var> be the
1592: resulting <span>absolute URL</span>.</li>
1593:
1594: <li><p>Let <var title="">name</var> be the value of the second
1.164 ihickson 1595: argument, or the empty string if the second argument was
1596: omitted.</li>
1.159 ihickson 1597:
1.167 ihickson 1598: <li>
1599:
1600: <p>If the <span>origin</span> of <var title="">scriptURL</var> is
1601: not the <span title="same origin">same</span> as the origin of the
1.309 ihickson 1602: <span>entry script</span>, then throw a <code>SecurityError</code>
1.182 ihickson 1603: exception.</p>
1.167 ihickson 1604:
1605: <p class="note">Thus, scripts must be external files with the same
1.269 ihickson 1606: scheme as the original page: you can't load a script from a <span title="data protocol"><code title="">data:</code> URL</span> or
1607: <span title="javascript protocol"><code title="">javascript:</code> URL</span>, and a <code>http:</code>
1608: page couldn't start workers using scripts with <code>http:</code>
1609: URLs.</p>
1.167 ihickson 1610:
1611: </li>
1.9 ihickson 1612:
1613: <li>
1614:
1.123 ihickson 1615: <p>Let <var title="">docs</var> be the <a href="#list-of-relevant-document-objects-to-add">list of relevant
1.192 ihickson 1616: <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 1617: constructor.</p>
1618:
1619: </li>
1620:
1621: <li>
1622:
1.50 ihickson 1623: <p>Execute the following substeps atomically:</p>
1.9 ihickson 1624:
1.155 ihickson 1625: <ol><li><p>Create a new <code><a href="#sharedworker">SharedWorker</a></code> object, which will
1.115 ihickson 1626: shortly be associated with a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1627: object. Let this <code><a href="#sharedworker">SharedWorker</a></code> object be <var title="">worker</var>.</li>
1.81 ihickson 1628:
1.301 ihickson 1629: <li><p><span>Create a new <code><a href="#messageport">MessagePort</a></code> object</span>
1.192 ihickson 1630: owned by the <span title="script's global object">global
1631: object</span> of the script that invoked the method. Let this be
1.123 ihickson 1632: the <var title="">outside port</var>.</li>
1.81 ihickson 1633:
1.115 ihickson 1634: <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 1635:
1.164 ihickson 1636: <li><p>Let <var title="">worker global scope</var> be
1637: null.</li>
1638:
1639: <li><p>If <var title="">name</var> is not the empty string and
1640: there exists a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object whose
1641: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag
1642: is false, whose <code title="dom-WorkerGlobalScope-name">name</code> attribute is
1643: exactly equal to <var title="">name</var>, and whose <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1644: represents an <span>absolute URL</span> with the <span>same
1645: origin</span> as <var title="">scriptURL</var>, then let <var title="">worker global scope</var> be that
1646: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object.</li>
1647:
1648: <li><p>Otherwise, if <var title="">name</var> is the empty string
1649: and there exists a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object
1650: whose <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a>
1.293 ihickson 1651: flag is false, whose <code title="dom-WorkerGlobalScope-name">name</code> attribute is the
1652: empty string, and whose <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1.237 ihickson 1653: represents an <span>absolute URL</span> that is exactly equal to
1654: <var title="">scriptURL</var>, then let <var title="">worker
1655: global scope</var> be that <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1656: object.</li>
1.164 ihickson 1657:
1.9 ihickson 1658: <li>
1659:
1.164 ihickson 1660: <p>If <var title="">worker global scope</var> is not null, then
1661: run these steps:</p>
1.81 ihickson 1662:
1.164 ihickson 1663: <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 1664: attribute represents an <span>absolute URL</span> that is not
1.159 ihickson 1665: exactly equal to <var title="">scriptURL</var>, then throw a
1.309 ihickson 1666: <code>URLMismatchError</code> exception and abort all these
1.159 ihickson 1667: steps.</li>
1.81 ihickson 1668:
1669: <li><p>Associate <var title="">worker</var> with <var title="">worker global scope</var>.</li>
1670:
1.301 ihickson 1671: <li><p><span>Create a new <code><a href="#messageport">MessagePort</a></code>
1.185 ihickson 1672: object</span> owned by <var title="">worker global
1673: scope</var>. Let this be the <var title="">inside
1674: port</var>.</li>
1.81 ihickson 1675:
1676: <li><p><span>Entangle</span> <var title="">outside port</var>
1677: and <var title="">inside port</var>.</li>
1678:
1679: <li><p>Return <var title="">worker</var> and perform the next
1680: step asynchronously.</li>
1.9 ihickson 1681:
1.81 ihickson 1682: <li><p>Create an event that uses the <code>MessageEvent</code>
1.115 ihickson 1683: interface, with the name <code title="event-connect">connect</code>, which does not bubble, is
1.118 ihickson 1684: not cancelable, has no default action, has a <code title="dom-MessageEvent-data">data</code> attribute whose value
1.307 ihickson 1685: is initialized to the empty string and has a <code title="dom-MessageEvent-ports">ports</code> attribute whose
1686: value is initialized to a <span title="dfn-read-only-array">read only</span> array containing
1687: only the newly created port, and <span>queue a task</span> to
1688: dispatch the event at <var title="">worker global
1689: scope</var>.</li>
1.43 ihickson 1690:
1.123 ihickson 1691: <li>
1692:
1693: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1694: <var title="">worker global scope</var>'s list of <span>the
1695: worker's <code>Document</code>s</span></a> the
1696: <code>Document</code> objects in <var title="">docs</var>.</p>
1697:
1698: </li>
1699:
1.124 ihickson 1700: <li>
1701:
1.192 ihickson 1702: <p>If the <span title="script's global object">global
1703: object</span> of the <span title="concept-script">script</span>
1.124 ihickson 1704: that invoked the constructor is a
1705: <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
1706: worker's workers</a> of the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1.192 ihickson 1707: object that is the <span title="script's global object">global
1708: object</span> of the <span title="concept-script">script</span>
1.124 ihickson 1709: that invoked the constructor.</p>
1710:
1711: </li>
1712:
1.81 ihickson 1713: <li><p>Abort all these steps.</li>
1.9 ihickson 1714:
1.155 ihickson 1715: </ol></li>
1.9 ihickson 1716:
1.185 ihickson 1717: <li><p>Create a new <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1718: object. Let <var title="">worker global scope</var> be this new
1719: object.</li>
1.9 ihickson 1720:
1.81 ihickson 1721: <li><p>Associate <var title="">worker</var> with <var title="">worker global scope</var>.</li>
1.9 ihickson 1722:
1.115 ihickson 1723: <li><p>Set the <code title="dom-SharedWorkerGlobalScope-name"><a href="#dom-sharedworkerglobalscope-name">name</a></code> attribute of
1.81 ihickson 1724: <var title="">worker global scope</var> to <var title="">name</var>.</li>
1.9 ihickson 1725:
1.301 ihickson 1726: <li><p><span>Create a new <code><a href="#messageport">MessagePort</a></code> object</span>
1.81 ihickson 1727: owned by <var title="">worker global scope</var>. Let <var title="">inside port</var> be this new object.</li>
1.9 ihickson 1728:
1.81 ihickson 1729: <li><p><span>Entangle</span> <var title="">outside port</var> and
1730: <var title="">inside port</var>.</li>
1.9 ihickson 1731:
1.155 ihickson 1732: </ol></li>
1.28 ihickson 1733:
1.123 ihickson 1734: <li><p>Return <var title="">worker</var> and perform the remaining
1735: steps asynchronously.</li>
1.18 ihickson 1736:
1.81 ihickson 1737: <li><p>Create an event that uses the <code>MessageEvent</code>
1.118 ihickson 1738: interface, with the name <code title="event-connect">connect</code>, which does not bubble, is not
1.115 ihickson 1739: cancelable, has no default action, has a <code title="dom-MessageEvent-data">data</code> attribute whose value is
1.307 ihickson 1740: initialized to the empty string and has a <code title="dom-MessageEvent-ports">ports</code> attribute whose value
1741: is initialized to a <span title="dfn-read-only-array">read
1742: only</span> array containing only the newly created port, and
1743: <span>queue a task</span> to dispatch the event at <var title="">worker global scope</var>.</li>
1.26 ihickson 1744:
1745: <li>
1.46 ihickson 1746:
1.123 ihickson 1747: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1748: <var title="">worker global scope</var>'s list of <span>the
1749: worker's <code>Document</code>s</span></a> the
1750: <code>Document</code> objects in <var title="">docs</var>.</p>
1751:
1752: </li>
1753:
1754: <li>
1755:
1.192 ihickson 1756: <p>If the <span title="script's global object">global object</span>
1.124 ihickson 1757: of the <span title="concept-script">script</span> that invoked the
1758: 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
1759: worker's workers</a> of the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1.192 ihickson 1760: object that is the <span title="script's global object">global
1761: object</span> of the <span title="concept-script">script</span>
1.124 ihickson 1762: that invoked the constructor.</p>
1763:
1764: </li>
1765:
1766: <li>
1767:
1.159 ihickson 1768: <p><a href="#run-a-worker">Run a worker</a> for <var title="">scriptURL</var>,
1.193 ihickson 1769: with the <span>script's browsing context</span> of the script that
1.159 ihickson 1770: invoked the method as the <var title="">owner browsing
1.232 ihickson 1771: context</var>, with the <span>script's document</span> of the
1772: script that invoked the method as the <var title="">owner
1773: document</var>, with the <span>origin</span> of the <span>entry
1.176 ihickson 1774: script</span> as the <var title="">owner origin</var>, and with
1775: <var title="">worker global scope</var> as the global scope.</p>
1.26 ihickson 1776:
1.60 ihickson 1777: </li>
1.81 ihickson 1778:
1.155 ihickson 1779: </ol><p>This constructor must be visible when the <span>script's global
1.192 ihickson 1780: object</span> is either a <code>Window</code> object or an object
1.155 ihickson 1781: 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 1782: <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 1783: interface <dfn id="workerutils">WorkerUtils</dfn> {
1.306 ihickson 1784: void <a href="#dom-workerglobalscope-importscripts" title="dom-WorkerGlobalScope-importScripts">importScripts</a>(DOMString... urls);
1.210 ihickson 1785: readonly attribute <a href="#workernavigator">WorkerNavigator</a> <a href="#dom-worker-navigator" title="dom-worker-navigator">navigator</a>;
1.150 ihickson 1786: };
1.290 ihickson 1787: <a href="#workerutils">WorkerUtils</a> implements <span>WindowTimers</span>;
1.301 ihickson 1788: <a href="#workerutils">WorkerUtils</a> implements <span>WindowBase64</span>;</pre><p>The <code>WindowTimers</code> and <code>WindowBase64</code>
1789: 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 1790: objects, etc) are not available to workers in this version of this
1.155 ihickson 1791: 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 1792: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, the user agent must run the
1.155 ihickson 1793: following steps:<ol><li><p>If there are no arguments, return without doing
1.81 ihickson 1794: anything. Abort these steps.</li>
1795:
1796: <li><p><span title="resolve a url">Resolve</span> each
1797: argument.</li>
1798:
1.309 ihickson 1799: <li><p>If any fail, throw a <code>SyntaxError</code>
1.81 ihickson 1800: exception.</li>
1801:
1.26 ihickson 1802:
1803: <li>
1.81 ihickson 1804:
1.45 ihickson 1805: <p>Attempt to <span>fetch</span> each resource identified by the
1.194 ihickson 1806: resulting <span title="absolute URL">absolute URLs</span>, from
1.256 ihickson 1807: the <span>entry script</span>'s <span>origin</span>, with the
1.281 ihickson 1808: <i>synchronous flag</i> set.</p>
1.81 ihickson 1809: </li>
1.26 ihickson 1810:
1811: <li>
1812:
1.81 ihickson 1813: <p>For each argument in turn, in the order given, starting with
1814: the first one, run these substeps:</p>
1.26 ihickson 1815:
1.155 ihickson 1816: <ol><li>
1.26 ihickson 1817:
1.81 ihickson 1818: <p>Wait for the fetching attempt for the corresponding resource
1819: to complete.</p>
1.60 ihickson 1820:
1.81 ihickson 1821: <p>If the fetching attempt failed, throw a
1.309 ihickson 1822: <code>NetworkError</code> exception and abort all these
1.81 ihickson 1823: steps.</p>
1.45 ihickson 1824:
1.264 ihickson 1825: <p>If the attempt succeeds, then let <var title="">source</var> be
1826: the script resource <span>decoded as UTF-8, with error
1827: handling</span>.
1828:
1829: <a href="#refsHTML">[HTML]</a>
1830:
1831: </p>
1.85 ihickson 1832:
1833: <p>Let <var title="">language</var> be JavaScript.</p>
1.61 ihickson 1834:
1.115 ihickson 1835: <p class="note">As with the worker's script, the script here is
1.81 ihickson 1836: always assumed to be JavaScript, regardless of the MIME
1.170 ihickson 1837: type.</p>
1.61 ihickson 1838:
1.81 ihickson 1839: </li>
1.26 ihickson 1840:
1.81 ihickson 1841: <li>
1.26 ihickson 1842:
1.81 ihickson 1843: <p><span>Create a script</span>, using <var title="">source</var> as the script source and <var title="">language</var> as the scripting language, using the
1.189 ihickson 1844: same global object, browsing context, URL character encoding,
1845: base URL, and script group as the <span title="concept-script">script</span> that was created by the
1.115 ihickson 1846: worker's <a href="#run-a-worker">run a worker</a> algorithm.</p>
1.81 ihickson 1847:
1.115 ihickson 1848: <p>Let the newly created <span title="concept-script">script</span> run until it either
1.81 ihickson 1849: returns, fails to parse, fails to catch an exception, or gets
1.115 ihickson 1850: prematurely aborted by the "<a href="#kill-a-worker">kill a worker</a>" or
1851: "<a href="#terminate-a-worker">terminate a worker</a>" algorithms defined above.</p>
1.26 ihickson 1852:
1.199 ihickson 1853: <p>If it failed to parse, then throw an ECMAScript
1854: <code>SyntaxError</code> exception and abort all these
1855: steps. <a href="#refsECMA262">[ECMA262]</a></p>
1.63 ihickson 1856:
1.81 ihickson 1857: <p>If an exception was raised or if the script was prematurely
1858: aborted, then abort all these steps, letting the exception or
1859: aborting continue to be processed by the script that called the
1.115 ihickson 1860: <code title="dom-WorkerGlobalScope-importScripts"><a href="#dom-workerglobalscope-importscripts">importScripts()</a></code>
1.81 ihickson 1861: method.</p>
1862:
1.115 ihickson 1863: <p>If the "<a href="#kill-a-worker">kill a worker</a>" or "<a href="#terminate-a-worker">terminate a
1.81 ihickson 1864: worker</a>" algorithms abort the script then abort all these
1865: steps.</p>
1866:
1867: </li>
1868:
1.155 ihickson 1869: </ol></li>
1.152 ihickson 1870:
1.210 ihickson 1871: </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 1872: of the <code><a href="#workerutils">WorkerUtils</a></code> interface must return an instance of
1.210 ihickson 1873: the <code><a href="#workernavigator">WorkerNavigator</a></code> interface, which represents the
1874: identity and state of the user agent (the client):<pre class="idl">interface <dfn id="workernavigator">WorkerNavigator</dfn> {};
1875: <a href="#workernavigator">WorkerNavigator</a> implements <span>NavigatorID</span>;
1876: <a href="#workernavigator">WorkerNavigator</a> implements <span>NavigatorOnLine</span>;</pre><p>Objects implementing the <code><a href="#workernavigator">WorkerNavigator</a></code> interface
1877: also implement the <code>NavigatorID</code> and
1878: <code>NavigatorOnLine</code> interfaces.
1.205 ihickson 1879:
1.226 ihickson 1880: <a href="#refsHTML">[HTML]</a>
1.205 ihickson 1881:
1.210 ihickson 1882: <p>This <code><a href="#workernavigator">WorkerNavigator</a></code> interface must not exist if the
1883: interface's <span>relevant namespace object</span> is a
1.272 ihickson 1884: <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 1885: the global scope of scripts whose <span>script's global
1886: object</span> is a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object except for
1.155 ihickson 1887: the following:<ul><li><p><code>XMLHttpRequest</code> and all interface objects and
1.81 ihickson 1888: constructors defined by the XMLHttpRequest specifications, except
1889: that the <span>document response entity body</span> must always be
1.160 ihickson 1890: null. The <span><code>XMLHttpRequest</code> base URL</span> is the
1891: <span>script's base URL</span>; the
1892: <span><code>XMLHttpRequest</code> origin</span> is the script's
1893: <span>origin</span>. <a href="#refsXHR">[XHR]</a></li>
1.81 ihickson 1894:
1.205 ihickson 1895: <li><p>The interface objects and constructors defined by this
1896: specification.</li>
1.119 ihickson 1897:
1.205 ihickson 1898: <li><p>Constructors defined by specifications that explicitly say
1899: that they should be visible when the <span>script's global
1900: object</span> is a <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>, a
1901: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>, or an object implementing the
1902: <code><a href="#workerutils">WorkerUtils</a></code> interface; the interfaces of any objects
1903: with such constructors; and the interfaces of any objects made
1904: accessible through APIs exposed by those constructors or made
1905: accessible through interfaces to be implemented by any objects that
1906: are themselves accessible to scripts whose <span>script's global
1907: object</span> implements the <code><a href="#workerutils">WorkerUtils</a></code>
1908: interface.</li>
1909:
1910: </ul><p class="note">These requirements do not override the requirements
1911: defined by the Web IDL specification, in particular concerning the
1.272 ihickson 1912: 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 1913: // <span>URL decomposition IDL attributes</span>
1.294 ihickson 1914: stringifier readonly attribute DOMString <a href="#dom-workerlocation-href" title="dom-WorkerLocation-href">href</a>;
1.115 ihickson 1915: readonly attribute DOMString <a href="#dom-workerlocation-protocol" title="dom-WorkerLocation-protocol">protocol</a>;
1916: readonly attribute DOMString <a href="#dom-workerlocation-host" title="dom-WorkerLocation-host">host</a>;
1917: readonly attribute DOMString <a href="#dom-workerlocation-hostname" title="dom-WorkerLocation-hostname">hostname</a>;
1918: readonly attribute DOMString <a href="#dom-workerlocation-port" title="dom-WorkerLocation-port">port</a>;
1919: readonly attribute DOMString <a href="#dom-workerlocation-pathname" title="dom-WorkerLocation-pathname">pathname</a>;
1920: readonly attribute DOMString <a href="#dom-workerlocation-search" title="dom-WorkerLocation-search">search</a>;
1921: readonly attribute DOMString <a href="#dom-workerlocation-hash" title="dom-WorkerLocation-hash">hash</a>;
1.155 ihickson 1922: };</pre><p>A <code><a href="#workerlocation">WorkerLocation</a></code> object represents an <span>absolute
1923: URL</span> set at its creation.<p>The <dfn id="dom-workerlocation-href" title="dom-WorkerLocation-href"><code>href</code></dfn>
1.81 ihickson 1924: attribute must return the <span>absolute URL</span> that the object
1.155 ihickson 1925: represents.<p>The <code><a href="#workerlocation">WorkerLocation</a></code> interface also has the complement
1.163 ihickson 1926: of <span>URL decomposition IDL attributes</span>, <dfn id="dom-workerlocation-protocol" title="dom-WorkerLocation-protocol"><code>protocol</code></dfn>,
1.115 ihickson 1927: <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>,
1928: <dfn id="dom-workerlocation-pathname" title="dom-WorkerLocation-pathname"><code>pathname</code></dfn>,
1929: <dfn id="dom-workerlocation-search" title="dom-WorkerLocation-search"><code>search</code></dfn>,
1.263 ihickson 1930: and <dfn id="dom-workerlocation-hash" title="dom-WorkerLocation-hash"><code>hash</code></dfn>.
1931: These must follow the rules given for <span>URL decomposition IDL
1932: attributes</span>, with the <span title="concept-uda-input">input</span> being the <span>absolute
1933: 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
1934: <span title="concept-uda-setter">common setter action</span> being a
1935: no-op, since the attributes are defined to be readonly.
1.205 ihickson 1936:
1.226 ihickson 1937: <a href="#refsHTML">[HTML]</a>
1.205 ihickson 1938:
1.209 ihickson 1939: <p>The <code><a href="#workerlocation">WorkerLocation</a></code> interface must not exist if the
1940: interface's <span>relevant namespace object</span> is a
1.281 ihickson 1941: <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 1942: <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 1943:
1.152 ihickson 1944: <dt id="refsECMA262">[ECMA262]</dt>
1945: <dd><cite><a href="http://www.ecma-international.org/publications/standards/Ecma-262.htm">ECMAScript
1.226 ihickson 1946: Language Specification</a></cite>. ECMA.</dd>
1.152 ihickson 1947:
1.226 ihickson 1948: <dt id="refsHTML">[HTML]</dt>
1949: <dd><cite><a href="http://www.whatwg.org/specs/web-apps/current-work/">HTML</a></cite>,
1950: I. Hickson. WHATWG.</dd>
1.152 ihickson 1951:
1.154 ihickson 1952: <dt id="refsRFC2119">[RFC2119]</dt>
1.265 ihickson 1953: <dd><cite><a href="http://tools.ietf.org/html/rfc2119">Key words for use in
1.226 ihickson 1954: RFCs to Indicate Requirement Levels</a></cite>, S. Bradner. IETF.</dd>
1.154 ihickson 1955:
1956: <dt id="refsWEBIDL">[WEBIDL]</dt>
1.281 ihickson 1957: <dd><cite><a href="http://dev.w3.org/2006/webapi/WebIDL/">Web
1.226 ihickson 1958: IDL</a></cite>, C. McCormack. W3C.</dd>
1.154 ihickson 1959:
1.152 ihickson 1960: <dt id="refsXHR">[XHR]</dt>
1.281 ihickson 1961: <dd><cite><a href="http://dev.w3.org/2006/webapi/XMLHttpRequest-2/"><code>XMLHttpRequest</code></a></cite>,
1.226 ihickson 1962: A. van Kesteren. W3C.</dd>
1.152 ihickson 1963:
1.221 ihickson 1964: </dl><h2 class="no-num" id="acknowledgements">Acknowledgements</h2><!-- ACKS --><p>Thanks to
1.81 ihickson 1965:
1966: Aaron Boodman,
1.155 ihickson 1967: Алексей Проскуряков (Alexey Proskuryakov),
1.81 ihickson 1968: Anne van Kesteren,
1969: Ben Turner,
1970: Dmitry Titov,
1.96 ihickson 1971: Drew Wilson,
1.97 ihickson 1972: Jeremy Orlow,
1.81 ihickson 1973: Jonas Sicking,
1974: Justin James,
1975: Kevin Hakanson,
1976: Maciej Stachowiak,
1977: Michael Nordman,
1978: Mike Smith,
1979:
1980: and
1981:
1982: Philip Taylor
1983:
1.155 ihickson 1984: for their useful and substantial comments.<p>Huge thanks to the whole Gears team, who pioneered this
1.81 ihickson 1985: technology and whose experience has been a huge influence on this
1.155 ihickson 1986: specification.
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