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<title>Qt 4.6: Hello Script Example</title>
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<td width="1"> </td><td class="postheader" valign="center"><a href="index.html"><font color="#004faf">Home</font></a> · <a href="classes.html"><font color="#004faf">All Classes</font></a> · <a href="functions.html"><font color="#004faf">All Functions</font></a> · <a href="overviews.html"><font color="#004faf">Overviews</font></a></td></tr></table><h1 class="title">Hello Script Example<br /><span class="subtitle"></span>
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<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. The example also shows how to apply internationalization to scripts.</p>
<pre> int main(int argc, char *argv[])
{
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> QApplication app(argc, argv);
QScriptEngine engine;
QTranslator translator;
translator.load("helloscript_la");
app.installTranslator(&translator);
engine.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> QPushButton button;
QScriptValue scriptButton = engine.newQObject(&button);
engine.globalObject().setProperty("button", 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> QString fileName(":/helloscript.js");
QFile scriptFile(fileName);
scriptFile.open(QIODevice::ReadOnly);
QTextStream stream(&scriptFile);
QString contents = stream.readAll();
scriptFile.close();</pre>
<p>The contents of the script file are read.</p>
<pre> button.text = qsTr('Hello World!');
button.styleSheet = 'font-style: italic';
button.show();</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> QScriptValue result = engine.evaluate(contents, 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> if (result.isError()) {
QMessageBox::critical(0, "Hello Script",
QString::fromLatin1("%0:%1: %2")
.arg(fileName)
.arg(result.property("lineNumber").toInt32())
.arg(result.toString()));
return -1;
}</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> return app.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> lupdate helloscript.js -ts helloscript_la.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> linguist helloscript_la.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> <translation type='unfinished'></translation></pre>
<p>but instead will have</p>
<pre> <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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