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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<title>Qt 4.8: Hello Script Example</title>
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<a href="index.html" class="qtref"><span>Qt Reference Documentation</span></a>
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<li class="first"><a href="index.html">Home</a></li>
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<li><a href="all-examples.html">Examples</a></li>
<li>Hello Script Example</li>
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<h3><a name="toc">Contents</a></h3>
<ul>
<li class="level1"><a href="#translating-the-application">Translating the Application</a></li>
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<h1 class="title">Hello Script Example</h1>
<span class="subtitle"></span>
<!-- $$$script/helloscript-description -->
<div class="descr"> <a name="details"></a>
<p>Files:</p>
<ul>
<li><a href="script-helloscript-helloscript-js.html">script/helloscript/helloscript.js</a></li>
<li><a href="script-helloscript-main-cpp.html">script/helloscript/main.cpp</a></li>
<li><a href="script-helloscript-helloscript-pro.html">script/helloscript/helloscript.pro</a></li>
<li><a href="script-helloscript-helloscript-qrc.html">script/helloscript/helloscript.qrc</a></li>
</ul>
<p>The Hello Script example shows the basic use of Qt Script: How to embed a script engine into the application, how to evaluate a script, and how to process the result of the evaluation.<p>The example also shows how to apply internationalization to scripts.</p>
<pre class="cpp"> <span class="type">int</span> main(<span class="type">int</span> argc<span class="operator">,</span> <span class="type">char</span> <span class="operator">*</span>argv<span class="operator">[</span><span class="operator">]</span>)
{
Q_INIT_RESOURCE(helloscript);</pre>
<p>The application will load the script file to evaluate from a resource, so we first make sure that the resource is initialized.</p>
<pre class="cpp"> <span class="type"><a href="qapplication.html">QApplication</a></span> app(argc<span class="operator">,</span> argv);
<span class="type"><a href="qscriptengine.html">QScriptEngine</a></span> engine;
<span class="type"><a href="qtranslator.html">QTranslator</a></span> translator;
translator<span class="operator">.</span>load(<span class="string">"helloscript_la"</span>);
app<span class="operator">.</span>installTranslator(<span class="operator">&</span>translator);
engine<span class="operator">.</span>installTranslatorFunctions();</pre>
<p>We attempt to load a translation, and install translation functions in the script engine. How to produce a translation is explained later.</p>
<pre class="cpp"> <span class="type"><a href="qpushbutton.html">QPushButton</a></span> button;
<span class="type"><a href="qscriptvalue.html">QScriptValue</a></span> scriptButton <span class="operator">=</span> engine<span class="operator">.</span>newQObject(<span class="operator">&</span>button);
engine<span class="operator">.</span>globalObject()<span class="operator">.</span>setProperty(<span class="string">"button"</span><span class="operator">,</span> scriptButton);</pre>
<p>A push button is created and exported to the script environment as a global variable, <tt>button</tt>. Scripts will be able to access properties, signals and slots of the button as properties of the <tt>button</tt> script object; the script object acts as a proxy to the C++ button object.</p>
<pre class="cpp"> <span class="type"><a href="qstring.html">QString</a></span> fileName(<span class="string">":/helloscript.js"</span>);
<span class="type"><a href="qfile.html">QFile</a></span> scriptFile(fileName);
scriptFile<span class="operator">.</span>open(<span class="type"><a href="qiodevice.html">QIODevice</a></span><span class="operator">::</span>ReadOnly);
<span class="type"><a href="qtextstream.html">QTextStream</a></span> stream(<span class="operator">&</span>scriptFile);
<span class="type"><a href="qstring.html">QString</a></span> contents <span class="operator">=</span> stream<span class="operator">.</span>readAll();
scriptFile<span class="operator">.</span>close();</pre>
<p>The contents of the script file are read.</p>
<pre class="js"> <span class="name">button</span>.<span class="name">text</span> <span class="operator">=</span> <span class="name">qsTr</span>(<span class="string">'Hello World!'</span>);
<span class="name">button</span>.<span class="name">styleSheet</span> <span class="operator">=</span> <span class="string">'font-style: italic'</span>;
<span class="name">button</span>.<span class="name">show</span>();</pre>
<p>The script sets the <tt>text</tt> (note that the qTr() function is used to allow for translation) and <tt>styleSheet</tt> properties of the button, and calls the button's <tt>show()</tt> slot.</p>
<pre class="cpp"> <span class="type"><a href="qscriptvalue.html">QScriptValue</a></span> result <span class="operator">=</span> engine<span class="operator">.</span>evaluate(contents<span class="operator">,</span> fileName);</pre>
<p>The script is evaluated. Note that the file name is passed as the (optional) second parameter; this makes it possible for the script engine to produce a meaningful backtrace if something goes wrong, and makes the qTr() function be able to resolve the translations that are associated with this script.</p>
<pre class="cpp"> <span class="keyword">if</span> (result<span class="operator">.</span>isError()) {
<span class="type"><a href="qmessagebox.html">QMessageBox</a></span><span class="operator">::</span>critical(<span class="number">0</span><span class="operator">,</span> <span class="string">"Hello Script"</span><span class="operator">,</span>
<span class="type"><a href="qstring.html">QString</a></span><span class="operator">::</span>fromLatin1(<span class="string">"%0:%1: %2"</span>)
<span class="operator">.</span>arg(fileName)
<span class="operator">.</span>arg(result<span class="operator">.</span>property(<span class="string">"lineNumber"</span>)<span class="operator">.</span>toInt32())
<span class="operator">.</span>arg(result<span class="operator">.</span>toString()));
<span class="keyword">return</span> <span class="operator">-</span><span class="number">1</span>;
}</pre>
<p>If the result is an Error object (e.g. the script contained a syntax error, or tried to call a function that doesn't exist), we obtain the line number and string representation of the error and display it in a message box.</p>
<pre class="cpp"> <span class="keyword">return</span> app<span class="operator">.</span>exec();
}</pre>
<p>If the evaluation went well, the application event loop is entered.</p>
<a name="translating-the-application"></a>
<h2>Translating the Application</h2>
<p>The Qt Script internalization support builds on what Qt already provides for C++; see the <a href="linguist-hellotr.html">Hello tr</a>() Example for an introduction.</p>
<p>Since we haven't made the translation file <tt>helloscript_la.qm</tt>, the source text is shown when we run the application ("Hello world!").</p>
<p>To generate the translation file, run <tt>lupdate</tt> as follows:</p>
<pre class="cpp"> lupdate helloscript<span class="operator">.</span>js <span class="operator">-</span>ts helloscript_la<span class="operator">.</span>ts</pre>
<p>You should now have a file <tt>helloscript_la.ts</tt> in the current directory. Run <tt>linguist</tt> to edit the translation:</p>
<pre class="cpp"> linguist helloscript_la<span class="operator">.</span>ts</pre>
<p>You should now see the text "helloscript.js" in the top left pane. Double-click it, then click on "Hello world!" and enter "Orbis, te saluto!" in the <b>Translation</b> pane (the middle right of the window). Don't forget the exclamation mark!</p>
<p>Click the <b>Done</b> checkbox and choose <b>File|Save</b> from the menu bar. The TS file will no longer contain</p>
<pre class="cpp"> <translation type='unfinished'></translation></pre>
<p>but instead will have</p>
<pre class="cpp"> <translation>Orbis, te saluto!</translation></pre>
<p>To see the application running in Latin, we have to generate a QM file from the TS file. Generating a QM file can be achieved either from within <i>Qt Linguist</i> (for a single TS file), or by using the command line program <tt>lrelease</tt> which will produce one QM file for each of the TS files listed in the project file. Generate <tt>hellotr_la.qm</tt> from <tt>hellotr_la.ts</tt> by choosing <b>File|Release</b> from <i>Qt Linguist</i>'s menu bar and pressing <b>Save</b> in the file save dialog that pops up. Now run the <tt>helloscript</tt> program again. This time the button will be labelled "Orbis, te saluto!".</p>
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