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Breadcrumbs go here --> <li><a href="qdeclarativeelements.html">QML Elements</a></li> <li>QML WorkerScript Element</li> </ul> </div> <div class="toolbuttons toolblock"> <ul> <li id="smallA" class="t_button">A</li> <li id="medA" class="t_button active">A</li> <li id="bigA" class="t_button">A</li> <li id="print" class="t_button"><a href="javascript:this.print();"> <span>Print</span></a></li> </ul> </div> </div> <div class="content mainContent"> <div class="toc"> <h3><a name="toc">Contents</a></h3> <ul> <li class="level1"><a href="#properties">Properties</a></li> <li class="level1"><a href="#signal-handlers">Signal Handlers</a></li> <li class="level1"><a href="#methods">Methods</a></li> <li class="level1"><a href="#details">Detailed Description</a></li> <li class="level3"><a href="#restrictions">Restrictions</a></li> </ul> </div> <h1 class="title">QML WorkerScript Element</h1> <span class="subtitle"></span> <!-- $$$WorkerScript-brief --> <p>The WorkerScript element enables the use of threads in QML. <a href="#details">More...</a></p> <!-- @@@WorkerScript --> <ul> <li><a href="qml-workerscript-members.html">List of all members, including inherited members</a></li> </ul> <a name="properties"></a> <h2>Properties</h2> <ul> <li class="fn"><b><b><a href="qml-workerscript.html#source-prop">source</a></b></b> : url</li> </ul> <a name="signal-handlers"></a> <h2>Signal Handlers</h2> <ul> <li class="fn"><b><b><a href="qml-workerscript.html#onMessage-signal">onMessage</a></b></b></li> </ul> <a name="methods"></a> <h2>Methods</h2> <ul> <li class="fn"><b><b><a href="qml-workerscript.html#sendMessage-method">sendMessage</a></b></b></li> </ul> <!-- $$$WorkerScript-description --> <a name="details"></a> <h2>Detailed Description</h2> <p>Use WorkerScript to run operations in a new thread. This is useful for running operations in the background so that the main GUI thread is not blocked.</p> <p>Messages can be passed between the new thread and the parent thread using <a href="qml-workerscript.html#sendMessage-method">sendMessage()</a> and the <a href="qml-workerscript.html#onMessage-signal">onMessage()</a> handler.</p> <p>An example:</p> <pre class="qml"> import QtQuick 1.0 <span class="type"><a href="qml-rectangle.html">Rectangle</a></span> { <span class="name">width</span>: <span class="number">300</span>; <span class="name">height</span>: <span class="number">300</span> <span class="type"><a href="qml-text.html">Text</a></span> { <span class="name">id</span>: <span class="name">myText</span> <span class="name">text</span>: <span class="string">'Click anywhere'</span> } <span class="type">WorkerScript</span> { <span class="name">id</span>: <span class="name">myWorker</span> <span class="name">source</span>: <span class="string">"script.js"</span> <span class="name">onMessage</span>: <span class="name">myText</span>.<span class="name">text</span> <span class="operator">=</span> <span class="name">messageObject</span>.<span class="name">reply</span> } <span class="type"><a href="qml-mousearea.html">MouseArea</a></span> { <span class="name">anchors</span>.fill: <span class="name">parent</span> <span class="name">onClicked</span>: <span class="name">myWorker</span>.<span class="name">sendMessage</span>({ 'x': <span class="name">mouse</span>.<span class="name">x</span>, 'y': mouse.y }) } }</pre> <p>The above worker script specifies a JavaScript file, "script.js", that handles the operations to be performed in the new thread. Here is <tt>script.js</tt>:</p> <pre class="cpp"> <span class="name">WorkerScript</span>.<span class="name">onMessage</span> <span class="operator">=</span> <span class="keyword">function</span>(<span class="name">message</span>) { <span class="comment">// ... long-running operations and calculations are done here</span> <span class="name">WorkerScript</span>.<span class="name">sendMessage</span>({ 'reply': <span class="string">'Mouse is at '</span> <span class="operator">+</span> <span class="name">message</span>.<span class="name">x</span> <span class="operator">+</span> <span class="string">','</span> <span class="operator">+</span> <span class="name">message</span>.<span class="name">y</span> }) }</pre> <p>When the user clicks anywhere within the rectangle, <tt>sendMessage()</tt> is called, triggering the <tt>WorkerScript.onMessage()</tt> handler in <tt>script.js</tt>. This in turn sends a reply message that is then received by the <tt>onMessage()</tt> handler of <tt>myWorker</tt>.</p> <a name="restrictions"></a> <h4>Restrictions</h4> <p>Since the <tt>WorkerScript.onMessage()</tt> function is run in a separate thread, the JavaScript file is evaluated in a context separate from the main QML engine. This means that unlike an ordinary JavaScript file that is imported into QML, the <tt>script.js</tt> in the above example cannot access the properties, methods or other attributes of the QML item, nor can it access any context properties set on the QML object through <a href="qdeclarativecontext.html">QDeclarativeContext</a>.</p> <p>Additionally, there are restrictions on the types of values that can be passed to and from the worker script. See the <a href="qml-workerscript.html#sendMessage-method">sendMessage()</a> documentation for details.</p> <p><b>See also </b><a href="declarative-threading-workerscript.html">WorkerScript example</a> and <a href="declarative-threading-threadedlistmodel.html">Threaded ListModel example</a>.</p> <!-- @@@WorkerScript --> <h2>Property Documentation</h2> <!-- $$$source --> <div class="qmlitem"><div class="qmlproto"><table class="qmlname"><tr valign="top" class="odd"><td class="tblQmlPropNode"><p><a name="source-prop"></a><span class="name">source</span> : <span class="type"><a href="qml-url.html">url</a></span></p></td></tr></table></div><div class="qmldoc"><p>This holds the url of the JavaScript file that implements the <tt>WorkerScript.onMessage()</tt> handler for threaded operations.</p> </div></div><!-- @@@source --> <br/> <h2>Signal Handler Documentation</h2> <!-- $$$onMessage --> <div class="qmlitem"><div class="qmlproto"><table class="qmlname"><tr valign="top" class="odd"><td class="tblQmlFuncNode"><p><a name="onMessage-signal"></a>WorkerScript::<span class="name">onMessage</span> ( <span class="type">jsobject</span> <i>msg</i> )</p></td></tr></table></div><div class="qmldoc"><p>This handler is called when a message <i>msg</i> is received from a worker script in another thread through a call to <a href="qml-workerscript.html#sendMessage-method">sendMessage()</a>.</p> </div></div><!-- @@@onMessage --> <br/> <h2>Method Documentation</h2> <!-- $$$sendMessage --> <div class="qmlitem"><div class="qmlproto"><table class="qmlname"><tr valign="top" class="odd"><td class="tblQmlFuncNode"><p><a name="sendMessage-method"></a>WorkerScript::<span class="name">sendMessage</span> ( <span class="type">jsobject</span> <i>message</i> )</p></td></tr></table></div><div class="qmldoc"><p>Sends the given <i>message</i> to a worker script handler in another thread. The other worker script handler can receive this message through the onMessage() handler.</p> <p>The <tt>message</tt> object may only contain values of the following types:</p> <ul> <li>boolean, number, string</li> <li>JavaScript objects and arrays</li> <li><a href="qml-listmodel.html">ListModel</a> objects (any other type of <a href="qobject.html">QObject</a>* is not allowed)</li> </ul> <p>All objects and arrays are copied to the <tt>message</tt>. With the exception of <a href="qml-listmodel.html">ListModel</a> objects, any modifications by the other thread to an object passed in <tt>message</tt> will not be reflected in the original object.</p> </div></div><!-- @@@sendMessage --> <br/> </div> </div> </div> <div class="ft"> <span></span> </div> </div> <div class="footer"> <p> <acronym title="Copyright">©</acronym> 2015 The Qt Company Ltd. 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