/usr/share/qt5/doc/qtquick/qtquick-threading-example.html is in qtdeclarative5-doc-html 5.5.1-2ubuntu6.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 | <?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<!-- threading.qdoc -->
<title>Qt Quick Examples - Threading | Qt Quick 5.5</title>
<link rel="stylesheet" type="text/css" href="style/offline.css" />
</head>
<body>
<div class="header" id="qtdocheader">
<div class="main">
<div class="main-rounded">
<div class="navigationbar">
<ul>
<li>Qt 5.5</li>
<li><a href="qtquick-index.html">Qt Quick</a></li>
<li>Qt Quick Examples - Threading</li>
<li id="buildversion">Qt 5.5.1 Reference Documentation</li>
</ul>
</div>
</div>
<div class="content">
<div class="line">
<div class="content mainContent">
<div class="sidebar">
<div class="toc">
<h3><a name="toc">Contents</a></h3>
<ul>
<li class="level1"><a href="#running-the-example">Running the Example</a></li>
<li class="level1"><a href="#threaded-listmodel">Threaded ListModel</a></li>
<li class="level1"><a href="#workerscript">WorkerScript</a></li>
</ul>
</div>
<div class="sidebar-content" id="sidebar-content"></div></div>
<h1 class="title">Qt Quick Examples - Threading</h1>
<span class="subtitle"></span>
<!-- $$$threading-description -->
<div class="descr"> <a name="details"></a>
<p class="centerAlign"><img src="images/qml-threading-example.png" alt="" /></p><p><i>Threading</i> is a collection of QML multithreading examples.</p>
<a name="running-the-example"></a>
<h2 id="running-the-example">Running the Example</h2>
<p>To run the example from Qt Creator, open the <b>Welcome</b> mode and select the example from <b>Examples</b>. For more information, visit Building and Running an Example.</p>
<a name="threaded-listmodel"></a>
<h2 id="threaded-listmodel">Threaded ListModel</h2>
<p><i>Threaded <a href="qtquick-modelviewsdata-modelview.html#listmodel">ListModel</a></i> contains a <a href="qml-qtquick-listview.html">ListView</a> and a <a href="qtquick-modelviewsdata-modelview.html#listmodel">ListModel</a>. The <a href="qtquick-modelviewsdata-modelview.html#listmodel">ListModel</a> object is updated asynchronously in another thread, and the results propagate back to the main thread. A timer requests updates from the worker thread periodically:</p>
<pre class="qml"> <span class="type">Timer</span> {
<span class="name">id</span>: <span class="name">timer</span>
<span class="name">interval</span>: <span class="number">2000</span>; <span class="name">repeat</span>: <span class="number">true</span>
<span class="name">running</span>: <span class="number">true</span>
<span class="name">triggeredOnStart</span>: <span class="number">true</span>
<span class="name">onTriggered</span>: {
var <span class="name">msg</span> = {'action': <span class="string">'appendCurrentTime'</span>, 'model': <span class="name">listModel</span>};
<span class="name">worker</span>.<span class="name">sendMessage</span>(<span class="name">msg</span>);
}
}</pre>
<p>Inside the worker thread, the <a href="qtquick-modelviewsdata-modelview.html#listmodel">ListModel</a> is synchronized once the data is finished loading:</p>
<pre class="js"><span class="name">WorkerScript</span>.<span class="name">onMessage</span> <span class="operator">=</span> <span class="keyword">function</span>(<span class="name">msg</span>) {
<span class="keyword">if</span> (<span class="name">msg</span>.<span class="name">action</span> <span class="operator">==</span> <span class="string">'appendCurrentTime'</span>) {
var <span class="name">data</span> = {'time': new <span class="name">Date</span>().<span class="name">toTimeString</span>()};
<span class="name">msg</span>.<span class="name">model</span>.<span class="name">append</span>(<span class="name">data</span>);
<span class="name">msg</span>.<span class="name">model</span>.<span class="name">sync</span>(); <span class="comment">// updates the changes to the list</span>
}
}</pre>
<a name="workerscript"></a>
<h2 id="workerscript">WorkerScript</h2>
<p><i>WorkerScript</i> contains an example of using a <a href="qtquick-threading-example.html#workerscript">WorkerScript</a> to offload expensive calculations into another thread. This keeps the UI from being blocked. This example calculates numbers in Pascal's Triangle, and not in a very optimal way, so it will often take several seconds to complete the calculation. By doing this in a <a href="qtquick-threading-example.html#workerscript">WorkerScript</a> in another thread, the UI is not blocked during this time.</p>
<p>When the UI needs another value, a request is sent to the <a href="qtquick-threading-example.html#workerscript">WorkerScript</a>:</p>
<pre class="qml"> <span class="type">Spinner</span> {
<span class="name">id</span>: <span class="name">rowSpinner</span>
<span class="name">label</span>: <span class="string">"Row"</span>
<span class="name">onValueChanged</span>: {
<span class="name">resultText</span>.<span class="name">text</span> <span class="operator">=</span> <span class="string">"Loading..."</span>;
<span class="name">myWorker</span>.<span class="name">sendMessage</span>( { row: <span class="name">rowSpinner</span>.<span class="name">value</span>, column: <span class="name">columnSpinner</span>.<span class="name">value</span> } );
}
}</pre>
<p>The workerscript then is free to take a really long time to calculate it:</p>
<pre class="js"><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">//Calculate result (may take a while, using a naive algorithm)</span>
var <span class="name">calculatedResult</span> = <span class="name">triangle</span>(<span class="name">message</span>.<span class="name">row</span>, <span class="name">message</span>.<span class="name">column</span>);
<span class="comment">//Send result back to main thread</span>
<span class="name">WorkerScript</span>.<span class="name">sendMessage</span>( { row: <span class="name">message</span>.<span class="name">row</span>,
column: <span class="name">message</span>.<span class="name">column</span>,
result: <span class="name">calculatedResult</span>} );
}</pre>
<p>When it's done, the result returns to the main scene via the <a href="qtquick-threading-example.html#workerscript">WorkerScript</a> type:</p>
<pre class="qml"> <span class="type">WorkerScript</span> {
<span class="name">id</span>: <span class="name">myWorker</span>
<span class="name">source</span>: <span class="string">"workerscript.js"</span>
<span class="name">onMessage</span>: {
<span class="keyword">if</span> (<span class="name">messageObject</span>.<span class="name">row</span> <span class="operator">==</span> <span class="name">rowSpinner</span>.<span class="name">value</span> <span class="operator">&&</span> <span class="name">messageObject</span>.<span class="name">column</span> <span class="operator">==</span> <span class="name">columnSpinner</span>.<span class="name">value</span>){ <span class="comment">//Not an old result</span>
<span class="keyword">if</span> (<span class="name">messageObject</span>.<span class="name">result</span> <span class="operator">==</span> -<span class="number">1</span>)
<span class="name">resultText</span>.<span class="name">text</span> <span class="operator">=</span> <span class="string">"Column must be <= Row"</span>;
<span class="keyword">else</span>
<span class="name">resultText</span>.<span class="name">text</span> <span class="operator">=</span> <span class="name">messageObject</span>.<span class="name">result</span>;
}
}
}</pre>
<p>Files:</p>
<ul>
<li><a href="qtquick-threading-threading-qml.html">threading/threading.qml</a></li>
<li><a href="qtquick-threading-threadedlistmodel-dataloader-js.html">threading/threadedlistmodel/dataloader.js</a></li>
<li><a href="qtquick-threading-threadedlistmodel-timedisplay-qml.html">threading/threadedlistmodel/timedisplay.qml</a></li>
<li><a href="qtquick-threading-workerscript-spinner-qml.html">threading/workerscript/Spinner.qml</a></li>
<li><a href="qtquick-threading-workerscript-workerscript-js.html">threading/workerscript/workerscript.js</a></li>
<li><a href="qtquick-threading-workerscript-workerscript-qml.html">threading/workerscript/workerscript.qml</a></li>
<li><a href="qtquick-threading-main-cpp.html">threading/main.cpp</a></li>
<li><a href="qtquick-threading-threading-pro.html">threading/threading.pro</a></li>
<li><a href="qtquick-threading-threading-qmlproject.html">threading/threading.qmlproject</a></li>
<li><a href="qtquick-threading-threading-qrc.html">threading/threading.qrc</a></li>
<li><a href="qtquick-threading-threadedlistmodel-threadedlistmodel-qmlproject.html">threading/threadedlistmodel/threadedlistmodel.qmlproject</a></li>
<li><a href="qtquick-threading-workerscript-workerscript-qmlproject.html">threading/workerscript/workerscript.qmlproject</a></li>
</ul>
</div>
<!-- @@@threading -->
</div>
</div>
</div>
</div>
</div>
<div class="footer">
<p>
<acronym title="Copyright">©</acronym> 2015 The Qt Company Ltd.
Documentation contributions included herein are the copyrights of
their respective owners.<br> The documentation provided herein is licensed under the terms of the <a href="http://www.gnu.org/licenses/fdl.html">GNU Free Documentation License version 1.3</a> as published by the Free Software Foundation.<br> Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property
of their respective owners. </p>
</div>
</body>
</html>
|