CR2 snapshot for TranReq.
authorAnssi Kostiainen <anssi.kostiainen@intel.com>
Fri, 14 Nov 2014 17:59:09 +0200
changeset 584 587f69a20dc6
parent 583 ad52df58c238
child 585 6cbf64c7dec0
CR2 snapshot for TranReq.
battery/CR2.html
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/battery/CR2.html	Fri Nov 14 17:59:09 2014 +0200
@@ -0,0 +1,1020 @@
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+</style><link rel="stylesheet" href="https://www.w3.org/StyleSheets/TR/W3C-CR"><!--[if lt IE 9]><script src='https://www.w3.org/2008/site/js/html5shiv.js'></script><![endif]--></head>
+  <body class="h-entry" role="document" id="respecDocument"><div class="head" role="contentinfo" id="respecHeader">
+  <p>
+      
+        
+            <a href="http://www.w3.org/"><img width="72" height="48" src="https://www.w3.org/Icons/w3c_home" alt="W3C"></a>
+        
+      
+  </p>
+  <h1 class="title p-name" id="title" property="dcterms:title">Battery Status API</h1>
+  
+  <h2 property="dcterms:issued" datatype="xsd:dateTime" content="2014-12-08T22:00:00.000Z" id="w3c-candidate-recommendation-09-december-2014"><abbr title="World Wide Web Consortium">W3C</abbr> Candidate Recommendation <time class="dt-published" datetime="2014-12-09">09 December 2014</time></h2>
+  <dl>
+    
+      <dt>This version:</dt>
+      <dd><a class="u-url" href="http://www.w3.org/TR/2014/CR-battery-status-20141209/">http://www.w3.org/TR/2014/CR-battery-status-20141209/</a></dd>
+      <dt>Latest published version:</dt>
+      <dd><a href="http://www.w3.org/TR/battery-status/">http://www.w3.org/TR/battery-status/</a></dd>
+    
+    
+      <dt>Latest editor's draft:</dt>
+      <dd><a href="http://dvcs.w3.org/hg/dap/raw-file/default/battery/Overview.html">http://dvcs.w3.org/hg/dap/raw-file/default/battery/Overview.html</a></dd>
+    
+    
+      <dt>Test suite:</dt>
+      <dd><a href="http://w3c-test.org/battery-status/">http://w3c-test.org/battery-status/</a></dd>
+    
+    
+      <dt>Implementation report:</dt>
+      <dd><a href="http://www.w3.org/2009/dap/wiki/ImplementationStatus">http://www.w3.org/2009/dap/wiki/ImplementationStatus</a></dd>
+    
+    
+    
+    
+      <dt>Previous version:</dt>
+      <dd><a rel="dcterms:replaces" href="http://www.w3.org/TR/2014/WD-battery-status-20140828/">http://www.w3.org/TR/2014/WD-battery-status-20140828/</a></dd>
+    
+    
+    <dt>Editors:</dt>
+    <dd class="p-author h-card vcard" rel="bibo:editor" inlist=""><span typeof="foaf:Person"><span property="foaf:name" class="p-name fn">Anssi Kostiainen</span>, <a rel="foaf:workplaceHomepage" class="p-org org h-org h-card" href="http://intel.com/">Intel</a></span>
+</dd>
+<dd class="p-author h-card vcard" rel="bibo:editor" inlist=""><span typeof="foaf:Person"><span property="foaf:name" class="p-name fn">Mounir Lamouri</span>, <a rel="foaf:workplaceHomepage" class="p-org org h-org h-card" href="http://google.com/">Google Inc.</a> (previously Mozilla)</span>
+</dd>
+
+    
+    
+  </dl>
+  
+  
+  
+  
+    
+      <p class="copyright">
+        <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> ©
+        2014
+        
+        <a href="http://www.w3.org/"><abbr title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup>
+        (<a href="http://www.csail.mit.edu/"><abbr title="Massachusetts Institute of Technology">MIT</abbr></a>,
+        <a href="http://www.ercim.eu/"><abbr title="European Research Consortium for Informatics and Mathematics">ERCIM</abbr></a>,
+        <a href="http://www.keio.ac.jp/">Keio</a>, <a href="http://ev.buaa.edu.cn/">Beihang</a>), 
+        
+        All Rights Reserved.
+        
+        <abbr title="World Wide Web Consortium">W3C</abbr> <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
+        <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a> and
+        
+          <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document use</a>
+        
+        rules apply.
+      </p>
+    
+  
+  <hr>
+</div>
+    <section id="abstract" class="introductory" property="dcterms:abstract" datatype="" typeof="bibo:Chapter" resource="#abstract" rel="bibo:Chapter"><h2 role="heading" id="h2_abstract">Abstract</h2><p>
+      This specification defines an API that provides information about the
+      battery status of the hosting device.
+    </p></section><section id="sotd" class="introductory" typeof="bibo:Chapter" resource="#sotd" rel="bibo:Chapter"><h2 role="heading" id="h2_sotd">Status of This Document</h2>
+  
+    
+      
+        <p>
+          <em>This section describes the status of this document at the time of its publication.
+          Other documents may supersede this document. A list of current <abbr title="World Wide Web Consortium">W3C</abbr> publications and the
+          latest revision of this technical report can be found in the <a href="http://www.w3.org/TR/"><abbr title="World Wide Web Consortium">W3C</abbr> technical reports index</a> at
+          http://www.w3.org/TR/.</em>
+        </p>
+        
+      <p>
+        The functionality described in this specification was initially
+        specified as part of the
+        <a href="http://www.w3.org/TR/system-info-api/">System Information
+        API</a> but has been extracted in order to be more readily available,
+        more straightforward to implement, and in order to produce a
+        specification that could be implemented on its own merits without
+        interference with other, often unrelated, features.
+      </p>
+      <p>
+        No substantial changes have been made since the
+        <a href="http://www.w3.org/TR/2014/WD-battery-status-20140828/">
+        <abbr title="World Wide Web Consortium">W3C</abbr> Last Call Working Draft 28 August 2014</a>
+        (<a href="CR2-diff.html">diff</a>).
+      </p>
+      <p>
+        The CR exit criterion is two interoperable deployed implementations of
+        each feature. No features are marked as 'at-risk'.
+      </p>
+    
+        <p>
+          This document was published by the <a href="http://www.w3.org/2009/dap/">Device APIs Working Group</a> as a Candidate Recommendation.
+          
+            This document is intended to become a <abbr title="World Wide Web Consortium">W3C</abbr> Recommendation.
+          
+          
+            If you wish to make comments regarding this document, please send them to 
+            <a href="mailto:public-device-apis@w3.org">public-device-apis@w3.org</a> 
+            (<a href="mailto:public-device-apis-request@w3.org?subject=subscribe">subscribe</a>,
+            <a href="http://lists.w3.org/Archives/Public/public-device-apis/">archives</a>).
+          
+          
+          
+            <abbr title="World Wide Web Consortium">W3C</abbr> publishes a Candidate Recommendation to indicate that the document is believed to be
+            stable and to encourage implementation by the developer community. This Candidate
+            Recommendation is expected to advance to Proposed Recommendation no earlier than
+            03 February 2015.
+          
+          
+            All comments are welcome.
+          
+        </p>
+        
+          <p>
+            Please see the Working Group's  <a href="http://www.w3.org/2009/dap/wiki/ImplementationStatus">implementation
+            report</a>.
+          </p>
+        
+        
+          <p>
+            Publication as a Candidate Recommendation does not imply endorsement by the <abbr title="World Wide Web Consortium">W3C</abbr>
+            Membership. This is a draft document and may be updated, replaced or obsoleted by other
+            documents at any time. It is inappropriate to cite this document as other than work in
+            progress.
+          </p>
+        
+        
+        
+        <p>
+          
+            This document was produced by a group operating under the 
+            <a id="sotd_patent" about="" rel="w3p:patentRules" href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February 2004 <abbr title="World Wide Web Consortium">W3C</abbr> Patent
+            Policy</a>.
+          
+          
+          
+            
+              <abbr title="World Wide Web Consortium">W3C</abbr> maintains a <a href="http://www.w3.org/2004/01/pp-impl/43696/status" rel="disclosure">public list of any patent
+              disclosures</a> 
+            
+            made in connection with the deliverables of the group; that page also includes
+            instructions for disclosing a patent. An individual who has actual knowledge of a patent
+            which the individual believes contains
+            <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential
+            Claim(s)</a> must disclose the information in accordance with
+            <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section
+            6 of the <abbr title="World Wide Web Consortium">W3C</abbr> Patent Policy</a>.
+          
+          
+        </p>
+        
+          <p>
+            This document is governed by the  <a id="w3c_process_revision" href="http://www.w3.org/2005/10/Process-20051014/">14 October 2005 <abbr title="World Wide Web Consortium">W3C</abbr> Process Document</a>.
+          </p>
+        
+        
+      
+    
+  
+</section><section id="toc"><h2 class="introductory" role="heading" id="h2_toc">Table of Contents</h2><ul class="toc" role="directory" id="respecContents"><li class="tocline"><a href="#introduction" class="tocxref"><span class="secno">1. </span>Introduction</a></li><li class="tocline"><a href="#conformance" class="tocxref"><span class="secno">2. </span>Conformance</a></li><li class="tocline"><a href="#terminology" class="tocxref"><span class="secno">3. </span>Terminology</a></li><li class="tocline"><a href="#security-and-privacy-considerations" class="tocxref"><span class="secno">4. </span>Security and privacy considerations</a></li><li class="tocline"><a href="#the-navigator-interface" class="tocxref"><span class="secno">5. </span>The <span class="formerLink"><code>Navigator</code></span> interface</a></li><li class="tocline"><a href="#the-batterymanager-interface" class="tocxref"><span class="secno">6. </span>The <span class="formerLink"><code>BatteryManager</code></span> interface</a><ul class="toc"><li class="tocline"><a href="#multiple-batteries" class="tocxref"><span class="secno">6.1 </span>Multiple batteries</a></li><li class="tocline"><a href="#event-handlers" class="tocxref"><span class="secno">6.2 </span>Event handlers</a></li></ul></li><li class="tocline"><a href="#examples" class="tocxref"><span class="secno">7. </span>Examples</a></li><li class="tocline"><a href="#acknowledgements" class="tocxref"><span class="secno">A. </span>Acknowledgements</a></li><li class="tocline"><a href="#references" class="tocxref"><span class="secno">B. </span>References</a><ul class="toc"><li class="tocline"><a href="#normative-references" class="tocxref"><span class="secno">B.1 </span>Normative references</a></li></ul></li></ul></section>
+
+    
+
+    <section class="informative" id="introduction">
+      <!--OddPage--><h2 role="heading" id="h2_introduction"><span class="secno">1. </span>Introduction</h2><p><em>This section is non-normative.</em></p>
+      <p>
+        The Battery Status API specification defines a means for web
+        developers to programmatically determine the battery status of the
+        hosting device. Without knowing the battery status of a device, a web
+        developer must design the web application with an assumption of
+        sufficient battery level for the task at hand. This means the battery
+        of a device may exhaust faster than desired because web developers are
+        unable to make decisions based on the battery status. Given knowledge
+        of the battery status, web developers are able to craft web content and
+        applications which are power-efficient, thereby leading to improved
+        user experience. Authors should be aware, however, that a naïve
+        implementation of this API can negatively affect the battery life.
+     </p>
+     <p>
+        The Battery Status API can be used to defer or scale back work when
+        the device is not charging in or is low on battery. An archetype of an
+        advanced web application, a web-based email client, may check the
+        server for new email every few seconds if the device is charging,
+        but do so less frequently if the device is not charging or is low on
+        battery. Another example is a web-based word processor which could
+        monitor the battery level and save changes before the battery runs
+        out to prevent data loss.
+      </p>
+    </section>
+
+    <section id="conformance" typeof="bibo:Chapter" resource="#conformance" rel="bibo:Chapter"><!--OddPage--><h2 role="heading" id="h2_conformance"><span class="secno">2. </span>Conformance</h2>
+<p>
+  As well as sections marked as non-normative, all authoring guidelines, diagrams, examples,
+  and notes in this specification are non-normative. Everything else in this specification is
+  normative.
+</p>
+<p id="respecRFC2119">The key words <em class="rfc2119" title="MUST">MUST</em>, <em class="rfc2119" title="MUST NOT">MUST NOT</em>, and <em class="rfc2119" title="SHOULD">SHOULD</em> are 
+  to be interpreted as described in [<cite><a class="bibref" href="#bib-RFC2119">RFC2119</a></cite>].
+</p>
+
+      <p>
+        This specification defines conformance criteria that apply to a single
+        product: the <dfn id="dfn-user-agent">user agent</dfn> that implements the
+        interfaces that it contains.
+      </p>
+      <p>
+        Implementations that use ECMAScript to implement the APIs defined in
+        this specification must implement them in a manner consistent with the
+        ECMAScript Bindings defined in the Web IDL specification [<cite><a class="bibref" href="#bib-WEBIDL">WEBIDL</a></cite>],
+        as this specification uses that specification and terminology.
+      </p>
+    </section>
+    <section id="terminology">
+      <!--OddPage--><h2 role="heading" id="h2_terminology"><span class="secno">3. </span>Terminology</h2>
+      <p>
+        The following concepts, terms and interfaces are defined in [<cite><a class="bibref" href="#bib-HTML5">HTML5</a></cite>]:
+      </p>
+      <ul>
+        <li><code><a href="http://www.w3.org/html/wg/drafts/html/master/webappapis.html#navigator">
+        Navigator</a></code></li>
+        <li><code><a href="http://dev.w3.org/html5/spec/webappapis.html#eventhandler">
+        EventHandler</a></code></li>
+        <li><dfn id="dfn-queue-a-task"><a href="http://dev.w3.org/html5/spec/webappapis.html#queue-a-task">
+        queue a task</a></dfn></li>
+        <li><dfn id="dfn-fires-a-simple-event"><a href="http://dev.w3.org/html5/spec/webappapis.html#fire-a-simple-event">
+        fires a simple event</a></dfn></li>
+        <li><dfn id="dfn-event-handlers"><a href="http://dev.w3.org/html5/spec/webappapis.html#event-handlers">
+        event handlers</a></dfn></li>
+        <li><dfn id="dfn-event-handler-event-types"><a href="http://dev.w3.org/html5/spec/webappapis.html#event-handler-event-type">
+        event handler event types</a></dfn></li>
+        <li><dfn id="dfn-browsing-context"><a href="http://dev.w3.org/html5/spec/browsers.html#browsing-context">
+        browsing context</a></dfn></li>
+      </ul>
+      <p>
+        <a href="http://people.mozilla.org/~jorendorff/es6-draft.html#sec-promise-objects">
+        <dfn id="dfn-promise">Promise</dfn></a> objects are defined in [<cite><a class="bibref" href="#bib-ECMASCRIPT">ECMASCRIPT</a></cite>].
+      </p>
+    </section>
+    <section class="informative" id="security-and-privacy-considerations">
+      <!--OddPage--><h2 role="heading" id="h2_security-and-privacy-considerations"><span class="secno">4. </span>Security and privacy considerations</h2><p><em>This section is non-normative.</em></p>
+      <p>
+        The API defined in this specification is used to determine the battery
+        status of the hosting device. The information disclosed has minimal
+        impact on privacy or fingerprinting, and therefore is exposed without
+        permission grants. For example, the user agent can obfuscate the
+        exposed value in a way that authors cannot directly know if a hosting
+        device has no battery, is charging or is exposing fake values.
+      </p>
+    </section>
+    <section id="the-navigator-interface">
+      <!--OddPage--><h2 role="heading" id="h2_the-navigator-interface"><span class="secno">5. </span>The <a href="#idl-def-Navigator" class="idlType"><code>Navigator</code></a> interface</h2>
+      <pre class="idl"><span class="idlInterface" id="idl-def-Navigator">partial interface <span class="idlInterfaceID">Navigator</span> {
+<span class="idlMethod">    <span class="idlMethType">Promise&lt;<a href="#idl-def-BatteryManager" class="idlType"><code>BatteryManager</code></a>&gt;</span> <span class="idlMethName"><a href="#widl-Navigator-getBattery-Promise-BatteryManager">getBattery</a></span> ();</span>
+};</span></pre>
+      <p>
+        For each <a href="#dfn-browsing-context" class="internalDFN">browsing context</a>, there is a <dfn id="dfn-battery-promise">battery promise</dfn>,
+        which is initially set to <code>null</code>. It is a <a href="#dfn-promise" class="internalDFN">Promise</a>
+        object which holds a <a href="#idl-def-BatteryManager" class="idlType"><code>BatteryManager</code></a>.
+      </p>
+      <p>
+        The <code id="widl-Navigator-getBattery-Promise-BatteryManager">getBattery()</code>
+        method, when invoked, <em class="rfc2119" title="MUST">MUST</em> run the following steps:
+      </p>
+      <ul>
+        <li>
+          If <a href="#dfn-battery-promise" class="internalDFN">battery promise</a> is not <code>null</code>, return <a href="#dfn-battery-promise" class="internalDFN">battery
+          promise</a> and abort these steps.
+        </li>
+        <li>
+          Otherwise, set <a href="#dfn-battery-promise" class="internalDFN">battery promise</a> to a newly created
+          <a href="#dfn-promise" class="internalDFN">Promise</a>.
+        </li>
+        <li>
+          Return <a href="#dfn-battery-promise" class="internalDFN">battery promise</a> and continue asynchronously.
+        </li>
+        <li>
+          <a href="#dfn-create-a-new-batterymanager-object" class="internalDFN">Create a new <code>BatteryManager</code> object</a>,
+          and let <var>battery</var> be that object.
+        </li>
+        <li>
+          <dfn id="dfn-resolve">Resolve</dfn> <a href="#dfn-battery-promise" class="internalDFN">battery promise</a> with <var>battery</var>.
+        </li>
+      </ul>
+      <p>
+        The <a href="#dfn-user-agent" class="internalDFN">user agent</a> <em class="rfc2119" title="MUST NOT">MUST NOT</em> reject the <a href="#dfn-battery-promise" class="internalDFN">battery promise</a>.
+      </p>
+    </section>
+
+    <section id="the-batterymanager-interface">
+      <!--OddPage--><h2 role="heading" id="h2_the-batterymanager-interface"><span class="secno">6. </span>The <a href="#idl-def-BatteryManager" class="idlType"><code>BatteryManager</code></a> interface</h2>
+      <p>
+        The <a href="#idl-def-BatteryManager" class="idlType"><code>BatteryManager</code></a> interface represents the <dfn id="dfn-current-battery-status-information">current battery
+        status information</dfn> of the hosting device. The <code>charging</code>
+        attribute represents the charging state of the system's battery.
+        The <code>chargingTime</code> attribute represents the time remaining
+        in seconds until the system's battery is fully charged. The
+        <code>dischargingTime</code> attribute represents the time remaining in
+        seconds until the system's battery is completely discharged and the
+        system is about to be suspended, and the <code>level</code> attribute
+        represents the level of the system's battery.
+      </p>
+      <pre class="idl"><span class="idlInterface" id="idl-def-BatteryManager">interface <span class="idlInterfaceID">BatteryManager</span> : <span class="idlSuperclass">EventTarget</span> {
+<span class="idlAttribute">    readonly    attribute <span class="idlAttrType">boolean</span>             <span class="idlAttrName"><a href="#widl-BatteryManager-charging">charging</a></span>;</span>
+<span class="idlAttribute">    readonly    attribute <span class="idlAttrType">unrestricted double</span> <span class="idlAttrName"><a href="#widl-BatteryManager-chargingTime">chargingTime</a></span>;</span>
+<span class="idlAttribute">    readonly    attribute <span class="idlAttrType">unrestricted double</span> <span class="idlAttrName"><a href="#widl-BatteryManager-dischargingTime">dischargingTime</a></span>;</span>
+<span class="idlAttribute">    readonly    attribute <span class="idlAttrType">double</span>              <span class="idlAttrName"><a href="#widl-BatteryManager-level">level</a></span>;</span>
+<span class="idlAttribute">                attribute <span class="idlAttrType">EventHandler</span>        <span class="idlAttrName"><a href="#widl-BatteryManager-onchargingchange">onchargingchange</a></span>;</span>
+<span class="idlAttribute">                attribute <span class="idlAttrType">EventHandler</span>        <span class="idlAttrName"><a href="#widl-BatteryManager-onchargingtimechange">onchargingtimechange</a></span>;</span>
+<span class="idlAttribute">                attribute <span class="idlAttrType">EventHandler</span>        <span class="idlAttrName"><a href="#widl-BatteryManager-ondischargingtimechange">ondischargingtimechange</a></span>;</span>
+<span class="idlAttribute">                attribute <span class="idlAttrType">EventHandler</span>        <span class="idlAttrName"><a href="#widl-BatteryManager-onlevelchange">onlevelchange</a></span>;</span>
+};</span></pre>
+      <p>
+        When the <a href="#dfn-user-agent" class="internalDFN">user agent</a> is to <dfn id="dfn-create-a-new-batterymanager-object">create a new
+        <code>BatteryManager</code> object</dfn>, it <em class="rfc2119" title="MUST">MUST</em> instantiate a new
+        <a href="#idl-def-BatteryManager" class="idlType"><code>BatteryManager</code></a> object and set its attributes' values to those
+        that represent the <a href="#dfn-current-battery-status-information" class="internalDFN">current battery status information</a>, unless
+        the <a href="#dfn-user-agent" class="internalDFN">user agent</a> is <a href="#dfn-unable-to-report-the-battery-status-information" class="internalDFN">unable to report the battery status
+        information</a>, in which case the values <em class="rfc2119" title="MUST">MUST</em> be set to <dfn id="dfn-default-values">default
+        values</dfn> as follows:
+        <code>charging</code> <em class="rfc2119" title="MUST">MUST</em> be set to true,
+        <code>chargingTime</code> <em class="rfc2119" title="MUST">MUST</em> be set to 0,
+        <code>dischargingTime</code> <em class="rfc2119" title="MUST">MUST</em> be set to positive Infinity, and
+        <code>level</code> <em class="rfc2119" title="MUST">MUST</em> be set to 1.0.
+      </p>
+      <p>
+        The <a href="#dfn-user-agent" class="internalDFN">user agent</a> is said to be <dfn id="dfn-unable-to-report-the-battery-status-information">unable to report the
+        battery status information</dfn>, if it is not able to report the
+        values for any of the attributes, for example, due to a user or system
+        preference, setting, or limitation.
+      </p>
+      <div class="note"><div class="note-title" aria-level="1" role="heading" id="h_note_1"><span>Note</span></div><p class="">
+        Implementations <a href="#dfn-unable-to-report-the-battery-status-information" class="internalDFN">unable to report the battery status information</a>
+        emulate a fully charged and plugged in battery to reduce the potential
+        for fingerprinting and prevent applications from degrading performance,
+        if the battery status information is not made available, for example.
+      </p></div>
+      <p>
+        The <code id="widl-BatteryManager-charging">charging</code>
+        attribute <em class="rfc2119" title="MUST">MUST</em> be set to false if the battery
+        is discharging, and set to true, if the battery is charging, the
+        implementation is unable to report the state, or there is no battery
+        attached to the system, or otherwise. When the battery charging state
+        is updated, the <a href="#dfn-user-agent" class="internalDFN">user agent</a> <em class="rfc2119" title="MUST">MUST</em> <a href="#dfn-queue-a-task" class="internalDFN">queue a task</a> which sets
+        the <code>charging</code> attribute's value and <a href="#dfn-fires-a-simple-event" class="internalDFN">fires a simple
+        event</a> named <code><a href="#dfn-chargingchange" class="internalDFN">chargingchange</a></code> at the
+        <a href="#idl-def-BatteryManager" class="idlType"><code>BatteryManager</code></a> object.
+      </p>
+      <p>
+        The <code id="widl-BatteryManager-chargingTime">chargingTime</code>
+        attribute <em class="rfc2119" title="MUST">MUST</em> be set to 0, if the
+        battery is full or there is no battery attached to the system, and to
+        the value positive Infinity if the battery is discharging, the
+        implementation is unable to report the remaining charging time, or
+        otherwise. When the battery charging time is updated, the <a href="#dfn-user-agent" class="internalDFN">user
+        agent</a> <em class="rfc2119" title="MUST">MUST</em> <a href="#dfn-queue-a-task" class="internalDFN">queue a task</a> which sets the
+        <code>chargingTime</code> attribute's value and <a href="#dfn-fires-a-simple-event" class="internalDFN">fires a simple
+        event</a> named <code><a href="#dfn-chargingtimechange" class="internalDFN">chargingtimechange</a></code> at the
+        <a href="#idl-def-BatteryManager" class="idlType"><code>BatteryManager</code></a> object.
+      </p>
+      <p>
+        The <code id="widl-BatteryManager-dischargingTime">dischargingTime</code>
+        attribute <em class="rfc2119" title="MUST">MUST</em> be set to the value
+        positive Infinity, if the battery is charging, the implementation is
+        unable to report the remaining discharging time, there is no battery
+        attached to the system, or otherwise. When the battery discharging time
+        is updated, the <a href="#dfn-user-agent" class="internalDFN">user agent</a> <em class="rfc2119" title="MUST">MUST</em> <a href="#dfn-queue-a-task" class="internalDFN">queue a task</a> which sets
+        the <code>dischargingTime</code> attribute's value and <a href="#dfn-fires-a-simple-event" class="internalDFN">fires a
+        simple event </a> named <code><a href="#dfn-dischargingtimechange" class="internalDFN">dischargingtimechange</a></code> at the
+        <a href="#idl-def-BatteryManager" class="idlType"><code>BatteryManager</code></a> object.
+      </p>
+      <p>
+        The <code id="widl-BatteryManager-level">level</code>
+        attribute <em class="rfc2119" title="MUST">MUST</em> be set to 0 if the system's
+        battery is depleted and the system is about to be suspended, and to
+        1.0 if the battery is full, the implementation is unable to report the
+        battery's level, or there is no battery attached to the system. When
+        the battery level is updated, the <a href="#dfn-user-agent" class="internalDFN">user agent</a> <em class="rfc2119" title="MUST">MUST</em> <a href="#dfn-queue-a-task" class="internalDFN">queue a
+        task</a> which sets the <code>level</code> attribute's value and
+        <a href="#dfn-fires-a-simple-event" class="internalDFN">fires a simple event</a> named <code><a href="#dfn-levelchange" class="internalDFN">levelchange</a></code> at
+        the <a href="#idl-def-BatteryManager" class="idlType"><code>BatteryManager</code></a> object.
+      </p>
+      <div class="note"><div class="note-title" aria-level="1" role="heading" id="h_note_2"><span>Note</span></div><p class="">
+        The definition of how often the <code><a href="#dfn-chargingtimechange" class="internalDFN">chargingtimechange</a></code>,
+        <code><a href="#dfn-dischargingtimechange" class="internalDFN">dischargingtimechange</a></code>, and <code><a href="#dfn-levelchange" class="internalDFN">levelchange</a>
+        </code> events are fired is left to the implementation.
+      </p></div>
+      <section id="multiple-batteries" typeof="bibo:Chapter" resource="#multiple-batteries" rel="bibo:Chapter">
+        <h3 role="heading" id="h3_multiple-batteries"><span class="secno">6.1 </span>Multiple batteries</h3>
+        <p>
+          If a hosting device contains more than one battery,
+          <a href="#idl-def-BatteryManager" class="idlType"><code>BatteryManager</code></a> <em class="rfc2119" title="SHOULD">SHOULD</em> expose an unified view of the batteries.
+        </p>
+        <p>
+          The <code>charging</code> attribute <em class="rfc2119" title="MUST">MUST</em> be set to true if at least
+          one battery's <code>charging</code> state as described above is true.
+          Otherwise, it <em class="rfc2119" title="MUST">MUST</em> be set to false.
+        </p>
+        <p>
+          The <code>chargingTime</code> attribute can be set to the maximum
+          charging time of the individual batteries if charging in parallel,
+          and to the sum of the individual charging times if charging serially.
+        </p>
+        <p>
+          The <code>dischargingTime</code> attribute can be set to the maximum
+          discharging time of the individual batteries if discharging in
+          parallel, and to the sum of individual discharging times if
+          discharging serially.
+        </p>
+        <p>
+          The <code>level</code> attribute can be set to the average of the
+          levels of batteries of same capacity, or the weighted average of the
+          battery level attributes for batteries of different capacities.
+        </p>
+      </section>
+      <section id="event-handlers">
+        <h3 role="heading" id="h3_event-handlers"><span class="secno">6.2 </span>Event handlers</h3>
+        <p>
+          The following are the <a href="#dfn-event-handlers" class="internalDFN">event handlers</a> (and their corresponding
+          <a href="#dfn-event-handler-event-types" class="internalDFN">event handler event types</a>) that <em class="rfc2119" title="MUST">MUST</em> be supported as
+          attributes by the <a href="#idl-def-BatteryManager" class="idlType"><code>BatteryManager</code></a> object:
+        </p>
+        <table class="simple">
+          <thead>
+            <tr>
+              <th>event handler</th>
+              <th>event handler event type</th>
+            </tr>
+          </thead>
+          <tbody>
+            <tr>
+              <td>
+                <strong><code id="widl-BatteryManager-onchargingchange">
+                  onchargingchange
+                </code></strong>
+              </td>
+              <td>
+                <code><dfn id="dfn-chargingchange">
+                  chargingchange
+                </dfn></code>
+              </td>
+            </tr>
+            <tr>
+              <td>
+                <strong><code id="widl-BatteryManager-onchargingtimechange">
+                  onchargingtimechange
+                </code></strong>
+              </td>
+              <td>
+                <code><dfn id="dfn-chargingtimechange">
+                  chargingtimechange
+                </dfn></code>
+              </td>
+            </tr>
+            <tr>
+              <td>
+                <strong><code id="widl-BatteryManager-ondischargingtimechange">
+                  ondischargingtimechange
+                </code></strong>
+              </td>
+              <td>
+                <code><dfn id="dfn-dischargingtimechange">
+                  dischargingtimechange
+                </dfn></code>
+              </td>
+            </tr>
+            <tr>
+              <td>
+                <strong><code id="widl-BatteryManager-onlevelchange">
+                  onlevelchange
+                </code></strong>
+              </td>
+              <td>
+                <code><dfn id="dfn-levelchange">
+                  levelchange
+                </dfn></code>
+              </td>
+            </tr>
+          </tbody>
+        </table>
+      </section>
+    </section>
+
+    <section class="informative" id="examples">
+      <!--OddPage--><h2 role="heading" id="h2_examples"><span class="secno">7. </span>Examples</h2><p><em>This section is non-normative.</em></p>
+      <p>
+        This trivial example writes the battery level to the console each time
+        the level changes:
+      </p>
+      <div class="example"><div class="example-title"><span>Example 1</span></div><pre class="example highlight prettyprint prettyprinted"><span class="com">// We get the initial value when the promise resolves ...</span><span class="pln">
+navigator</span><span class="pun">.</span><span class="pln">getBattery</span><span class="pun">().</span><span class="kwd">then</span><span class="pun">(</span><span class="kwd">function</span><span class="pun">(</span><span class="pln">battery</span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
+  console</span><span class="pun">.</span><span class="pln">log</span><span class="pun">(</span><span class="pln">battery</span><span class="pun">.</span><span class="pln">level</span><span class="pun">);</span><span class="pln">
+  </span><span class="com">// ... and any subsequent updates.</span><span class="pln">
+  battery</span><span class="pun">.</span><span class="pln">onlevelchange </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">function</span><span class="pun">()</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
+    console</span><span class="pun">.</span><span class="pln">log</span><span class="pun">(</span><span class="kwd">this</span><span class="pun">.</span><span class="pln">level</span><span class="pun">);</span><span class="pln">
+  </span><span class="pun">};</span><span class="pln">
+</span><span class="pun">});</span></pre></div>
+      <p>
+        Alternatively, the same using the <code>addEventListener()</code>
+        method:
+      </p>
+      <div class="example"><div class="example-title"><span>Example 2</span></div><pre class="example highlight prettyprint prettyprinted"><span class="pln">navigator</span><span class="pun">.</span><span class="pln">getBattery</span><span class="pun">().</span><span class="kwd">then</span><span class="pun">(</span><span class="kwd">function</span><span class="pun">(</span><span class="pln">battery</span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
+  console</span><span class="pun">.</span><span class="pln">log</span><span class="pun">(</span><span class="pln">battery</span><span class="pun">.</span><span class="pln">level</span><span class="pun">);</span><span class="pln">
+  battery</span><span class="pun">.</span><span class="pln">addEventListener</span><span class="pun">(</span><span class="str">'levelchange'</span><span class="pun">,</span><span class="pln"> </span><span class="kwd">function</span><span class="pun">()</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
+    console</span><span class="pun">.</span><span class="pln">log</span><span class="pun">(</span><span class="kwd">this</span><span class="pun">.</span><span class="pln">level</span><span class="pun">);</span><span class="pln">
+  </span><span class="pun">});</span><span class="pln">
+</span><span class="pun">});</span></pre></div>
+      <p>
+        The following example updates the indicators to show the charging
+        state, level and time remaining in minutes:
+      </p>
+      <div class="example"><div class="example-title"><span>Example 3</span></div><pre class="example highlight prettyprint prettyprinted"><span class="dec">&lt;!DOCTYPE html&gt;</span><span class="pln">
+</span><span class="tag">&lt;html&gt;</span><span class="pln">
+</span><span class="tag">&lt;head&gt;</span><span class="pln">
+  </span><span class="tag">&lt;title&gt;</span><span class="pln">Battery Status API Example</span><span class="tag">&lt;/title&gt;</span><span class="pln">
+  </span><span class="tag">&lt;script&gt;</span><span class="pln">
+    window</span><span class="pun">.</span><span class="pln">onload </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">function</span><span class="pln"> </span><span class="pun">()</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
+      </span><span class="kwd">function</span><span class="pln"> updateBatteryStatus</span><span class="pun">(</span><span class="pln">battery</span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
+        document</span><span class="pun">.</span><span class="pln">querySelector</span><span class="pun">(</span><span class="str">'#charging'</span><span class="pun">).</span><span class="pln">textContent </span><span class="pun">=</span><span class="pln"> battery</span><span class="pun">.</span><span class="pln">charging </span><span class="pun">?</span><span class="pln"> </span><span class="str">'charging'</span><span class="pln"> </span><span class="pun">:</span><span class="pln"> </span><span class="str">'not charging'</span><span class="pun">;</span><span class="pln">
+        document</span><span class="pun">.</span><span class="pln">querySelector</span><span class="pun">(</span><span class="str">'#level'</span><span class="pun">).</span><span class="pln">textContent </span><span class="pun">=</span><span class="pln"> battery</span><span class="pun">.</span><span class="pln">level</span><span class="pun">;</span><span class="pln">
+        document</span><span class="pun">.</span><span class="pln">querySelector</span><span class="pun">(</span><span class="str">'#dischargingTime'</span><span class="pun">).</span><span class="pln">textContent </span><span class="pun">=</span><span class="pln"> battery</span><span class="pun">.</span><span class="pln">dischargingTime </span><span class="pun">/</span><span class="pln"> </span><span class="lit">60</span><span class="pun">;</span><span class="pln">
+      </span><span class="pun">}</span><span class="pln">
+
+      navigator</span><span class="pun">.</span><span class="pln">getBattery</span><span class="pun">().</span><span class="pln">then</span><span class="pun">(</span><span class="kwd">function</span><span class="pun">(</span><span class="pln">battery</span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
+        </span><span class="com">// Update the battery status initially when the promise resolves ...</span><span class="pln">
+        updateBatteryStatus</span><span class="pun">(</span><span class="pln">battery</span><span class="pun">);</span><span class="pln">
+
+        </span><span class="com">// .. and for any subsequent updates.</span><span class="pln">
+        battery</span><span class="pun">.</span><span class="pln">onchargingchange </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">function</span><span class="pln"> </span><span class="pun">()</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
+          updateBatteryStatus</span><span class="pun">(</span><span class="pln">battery</span><span class="pun">);</span><span class="pln">
+        </span><span class="pun">};</span><span class="pln">
+
+        battery</span><span class="pun">.</span><span class="pln">onlevelchange </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">function</span><span class="pln"> </span><span class="pun">()</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
+          updateBatteryStatus</span><span class="pun">(</span><span class="pln">battery</span><span class="pun">);</span><span class="pln">
+        </span><span class="pun">};</span><span class="pln">
+
+        battery</span><span class="pun">.</span><span class="pln">ondischargingtimechange </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">function</span><span class="pln"> </span><span class="pun">()</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
+          updateBatteryStatus</span><span class="pun">(</span><span class="pln">battery</span><span class="pun">);</span><span class="pln">
+        </span><span class="pun">};</span><span class="pln">
+      </span><span class="pun">});</span><span class="pln">
+    </span><span class="pun">};</span><span class="pln">
+  </span><span class="tag">&lt;/script&gt;</span><span class="pln">
+</span><span class="tag">&lt;/head&gt;</span><span class="pln">
+</span><span class="tag">&lt;body&gt;</span><span class="pln">
+  </span><span class="tag">&lt;div</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class="atv">"charging"</span><span class="tag">&gt;</span><span class="pln">(charging state unknown)</span><span class="tag">&lt;/div&gt;</span><span class="pln">
+  </span><span class="tag">&lt;div</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class="atv">"level"</span><span class="tag">&gt;</span><span class="pln">(battery level unknown)</span><span class="tag">&lt;/div&gt;</span><span class="pln">
+  </span><span class="tag">&lt;div</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class="atv">"dischargingTime"</span><span class="tag">&gt;</span><span class="pln">(discharging time unknown)</span><span class="tag">&lt;/div&gt;</span><span class="pln">
+</span><span class="tag">&lt;/body&gt;</span><span class="pln">
+</span><span class="tag">&lt;/html&gt;</span></pre></div>
+    </section>
+    <section class="appendix" id="acknowledgements">
+      <!--OddPage--><h2 role="heading" id="h2_acknowledgements"><span class="secno">A. </span>Acknowledgements</h2>
+      <p>
+        The group is deeply indebted to Mounir Lamouri, Jonas Sicking, and
+        the Mozilla WebAPI team in general for their invaluable feedback
+        based on prototype implementations. Many thanks to the people behind
+        the System Information API and Device Orientation Event specification
+        for the initial inspiration. Also thanks to the nice folks bringing us
+        the Page Visibility specification, which motivated the editor of this
+        specification to write the introduction chapter discussing some
+        real-world high value use cases that apply equally to this
+        specification. Special thanks to all the participants of the Device
+        APIs Working Group and others who have sent in substantial feedback
+        and comments, and made the Web a better place for everyone by
+        doing so.
+      </p>
+    </section>
+  
+
+<section id="references" class="appendix" typeof="bibo:Chapter" resource="#references" rel="bibo:Chapter"><!--OddPage--><h2 role="heading" id="h2_references"><span class="secno">B. </span>References</h2><section id="normative-references" typeof="bibo:Chapter" resource="#normative-references" rel="bibo:Chapter"><h3 role="heading" id="h3_normative-references"><span class="secno">B.1 </span>Normative references</h3><dl class="bibliography" about=""><dt id="bib-ECMASCRIPT">[ECMASCRIPT]</dt><dd rel="dcterms:requires">Allen Wirfs-Brock. <a href="http://people.mozilla.org/~jorendorff/es6-draft.html"><cite>ECMA-262 ECMAScript Language Specification, Edition 6</cite></a>. Draft. URL: <a href="http://people.mozilla.org/~jorendorff/es6-draft.html">http://people.mozilla.org/~jorendorff/es6-draft.html</a>
+</dd><dt id="bib-HTML5">[HTML5]</dt><dd rel="dcterms:requires">Robin Berjon; Steve Faulkner; Travis Leithead; Erika Doyle Navara; Edward O'Connor; Silvia Pfeiffer. <a href="http://www.w3.org/TR/html5/"><cite>HTML5</cite></a>. 28 October 2014. W3C Recommendation. URL: <a href="http://www.w3.org/TR/html5/">http://www.w3.org/TR/html5/</a>
+</dd><dt id="bib-RFC2119">[RFC2119]</dt><dd rel="dcterms:requires">S. Bradner. <a href="https://tools.ietf.org/html/rfc2119"><cite>Key words for use in RFCs to Indicate Requirement Levels</cite></a>. March 1997. Best Current Practice. URL: <a href="https://tools.ietf.org/html/rfc2119">https://tools.ietf.org/html/rfc2119</a>
+</dd><dt id="bib-WEBIDL">[WEBIDL]</dt><dd rel="dcterms:requires">Cameron McCormack. <a href="http://www.w3.org/TR/WebIDL/"><cite>Web IDL</cite></a>. 19 April 2012. W3C Candidate Recommendation. URL: <a href="http://www.w3.org/TR/WebIDL/">http://www.w3.org/TR/WebIDL/</a>
+</dd></dl></section></section></body></html>
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