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+<!DOCTYPE html>
+<html>
+ <head>
+ <title>Atmospheric Pressure Events</title>
+ <meta charset="utf-8"/>
+ <script src='http://www.w3.org/Tools/respec/respec-w3c-common' class='remove'></script>
+ <!--script src='http://dev.w3.org/2009/dap/ReSpec.js/js/respec.js' class='remove'></script-->
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+ shortName: "atmpressure",
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+ edDraftURI: "http://dvcs.w3.org/hg/dap/raw-file/tip/pressure/Overview.html",
+ //lcEnd: "yyyy-mm-dd",
+ editors: [
+ { name: "Dzung D Tran", company: "Intel", companyURL: "http://intel.com/" }
+ ],
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+ </script>
+ </head>
+<body>
+ <section id="abstract">
+ This specification defines a means to receive events that correspond to changes in
+ atmospheric pressure.
+ </section>
+
+ <section id="sotd">
+
+ </section>
+
+ <section class="informative">
+ <h2>Introduction</h2>
+ <p>
+ The <a>AtmPressureEvent</a> interface provides web developers
+ information about the atmospheric pressure levels measured at the hosting device.
+ </p>
+ <p>
+ This is achieved by interrogating a barometer or similar detectors
+ of the hosting device. Not all devices contain a barometer, and when
+ there is no barometer, this API is still exposed to the
+ scripting environment but it does nothing.
+ </p>
+
+ <section>
+ <h3>Use Cases</h3>
+ <p>Altitude sensing applications which make use of the relationship between changes in pressure relative to the altitude.</p>
+ <p>Weather prediction applications which make use of barometric pressure to predict weather conditions such as rain is coming.</p>
+ </section>
+
+ </section>
+
+ <section id="conformance">
+ <p>
+ This specification defines conformance criteria that apply to a single
+ product: the <dfn>user agent</dfn> that implements the
+ interfaces that it contains.
+ </p>
+ </section>
+
+ <section>
+ <h2>Terminology</h2>
+ <p>
+ The <code><a href="http://dev.w3.org/html5/spec/webappapis.html#eventhandler">
+ EventHandler</a></code> interface represents a <a href="http://www.w3.org/TR/WebIDL/#idl-callback-functions">callback function</a> used for <a href="http://dev.w3.org/html5/spec/webappapis.html#event-handlers">event
+ handlers</a> as defined in [[!HTML5]]. </p>
+ <p>
+ The concepts <dfn><a href="http://dev.w3.org/html5/spec/webappapis.html#queue-a-task">
+ queue a task</a></dfn> and
+ <dfn><a href="http://dev.w3.org/html5/spec/webappapis.html#fire-a-simple-event">
+ fires a simple event</a></dfn> are defined in [[!HTML5]].
+ </p>
+ <p>
+ The terms <dfn><a href="http://dev.w3.org/html5/spec/webappapis.html#event-handlers">
+ event handlers</a></dfn> and
+ <dfn><a href="http://dev.w3.org/html5/spec/webappapis.html#event-handler-event-type">
+ event handler event types</a></dfn> are defined in [[!HTML5]].
+ </p>
+ <p>The concepts <dfn>
+ <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#constructing-events">
+ create an event</a></dfn> and <dfn>
+ <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#firing-events">
+ fire an event</a></dfn> are defined in [[!DOM4]].
+ <p>
+ The <dfn>current atmospheric pressure</dfn> is a value that represents the
+ force per unit area exerted onto the hosting device around the pressure sensor by the weight of air above that surface in the atmosphere of Earth in hPA (millibar).
+ </p>
+ </section>
+
+ <section>
+ <h2>Security and privacy considerations</h2>
+ <p>
+ </p>
+ </section>
+
+ <section>
+ <h2>Atmospheric Pressure</h2>
+ <p>
+ The HTML5 specification [[!HTML5]] defines a <a>Window</a> interface,
+ which this specification extends:
+ </p>
+ <dl title="partial interface Window" class="idl">
+ <dt>attribute EventHandler onatmpressure</dt>
+ <dd>
+ </dd>
+ </dl>
+ <p>
+ The <code>onatmpressure</code> event handler and its corresponding
+ event handler event type <code>atmpressure</code> MUST be supported
+ as an IDL attribute by all objects implementing the <a>Window</a>
+ interface.
+ </p>
+ <section>
+ <h2><a>AtmPressureEvent</a> Interface</h2>
+ <dl title="[Constructor (DOMString type, optional AtmPressureEventInit eventInitDict)]
+ interface AtmPressureEvent : Event"
+ class="idl" data-merge='AtmPressureEventInit'>
+ <dt>readonly attribute double value</dt>
+ <dd>
+ The <a>current atmospheric pressure</a>.
+ </dd>
+ </dl>
+ <dl title="dictionary AtmPressureEventInit : EventInit" class='idl'>
+ <dt>
+ double value
+ </dt>
+ <dd></dd>
+ </dl>
+ <p>
+ When a <dfn>user agent</dfn> is required to <dfn>fire an atmospheric pressure event</dfn>, the <dfn>user agent</dfn> MUST run the
+ following steps:
+ </p>
+ <ol class="rule">
+ <li>
+ <a>Create an event</a> that uses the <a>AtmPressureEvent</a>
+ interface, with the name <code>atmpressure</code>, which
+ bubbles, is not cancelable, and has no default action, that also
+ meets the following conditions:
+ <ol>
+ <li>
+ If the implementation is unable to report the <a>current
+ atmospheric pressure</a>, initialize the <code>value</code>
+ attribute to positive Infinity, otherwise initialize the
+ attribute to the <a>current atmospheric pressure</a>.
+ </li>
+ </ol>
+ </li>
+ <li>
+ <a>Queue a task</a> to dispatch the newly created event at the
+ <a>Window</a> object.
+ </li>
+ </ol>
+ <p>
+ When the <a>current atmospheric pressure</a> changes, the <a>user
+ agent</a> MUST <a>fire a atmospheric pressure event</a>.
+ </p>
+ <div class="note">
+ The definition of granularity i.e. how often the event is fired is
+ left to the implementation. Implementations may fire the event if
+ they have reason to believe that the page does not have sufficiently
+ fresh data.
+ </div>
+ <section>
+ <h2>Event handlers</h2>
+ <p>
+ The following are the <a>event handlers</a> (and their corresponding
+ <a>event handler event types</a>) that MUST be supported as
+ attributes by the <code>Window</code> object:
+ </p>
+ <table class="simple">
+ <thead>
+ <tr>
+ <th>event handler</th>
+ <th>event handler event type</th>
+ </tr>
+ </thead>
+ <tbody>
+ <tr>
+ <td><strong><code>onatmpressure</code></strong></td>
+ <td><code>atmpressure</code></td>
+ </tr>
+ </tbody>
+ </table>
+ </section>
+ </section>
+ </section>
+
+ <section class="appendix"></section>
+</body>
+</html>