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<td >Qt 5.12</td><td ><a href="qtwebengine-index.html">Qt WebEngine</a></td><td ><a href="webengine-widgetexamples.html">Qt WebEngine Widgets Examples</a></td><td >WebEngine Widgets PrintMe Example</td></tr></table><table class="buildversion"><tr>
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<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="#simple-html-page">Simple HTML Page</a></li>
<li class="level1"><a href="#main-function">Main Function</a></li>
<li class="level1"><a href="#print-handler">Print Handler</a></li>
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<h1 class="title">WebEngine Widgets PrintMe Example</h1>
<span class="subtitle"></span>
<!-- $$$webenginewidgets/printme-brief -->
<p>Demonstrates how to print web pages using Qt <a href="qml-qtwebengine-webengine.html">WebEngine</a> Widgets.</p>
<!-- @@@webenginewidgets/printme -->
<!-- $$$webenginewidgets/printme-description -->
<div class="descr"> <a name="details"></a>
<p class="centerAlign"><img src="images/printme-example.png" alt="" /></p><p><i>PrintMe</i> demonstrates how to use the <a href="qwebenginepage.html">QWebEnginePage</a> and QPrintDialog classes to print a web page. Further, it shows how to implement print preview by using the QPrintPreviewDialog class. For completeness, it also illustrates how to trigger a printing request within JavaScript.</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="simple-html-page"></a>
<h2 id="simple-html-page">Simple HTML Page</h2>
<p>In this example, we create an internal HTML page that is added as a resource collection file (.qrc). The page shows only a small HTML message box that explains how to trigger printing by using keyboard shortcuts or clicking a button. The button has the JavaScript <code>onclick</code> event attribute that calls the JavaScript <code>window.print()</code> function.</p>
<pre class="cpp">
<html lang="en">
<head>
<meta charset="utf-8">
<title>PrintMe</title>
<link rel="stylesheet" type="text/css" href="style.css">
<script>
function printNow() {
window.print();
}
</script>
</head>
<body>
<form class="form">
<img class="logo" src="icon.svg" alt="qtwebengine">
<div class="header">
<h1>Hello Paper World!</h1>
<h2>Press Ctrl+p to print with print preview</h2>
<h2>Press Ctrl+Shift+p to print without print preview</h2>
<h2>Click the button to print using JavaScript</h2>
<p class="button" onclick="printNow()">Print Now</p>
</form>
</body>
</html>
</pre>
<a name="main-function"></a>
<h2 id="main-function">Main Function</h2>
<p>In the <code>main</code> function, we first instantiate a <a href="qwebengineview.html">QWebEngineView</a> and set the URL to our internal HTML page. Next, we create a <code>PrintHandler</code> instance and pass the requested page. For convenience, we also create keyboard shortcuts that can be used to call a print dialog or print preview dialog.</p>
<pre class="cpp">
<span class="type"><a href="qwebengineview.html">QWebEngineView</a></span> view;
view<span class="operator">.</span>setUrl(<span class="type">QUrl</span>(<span class="type">QStringLiteral</span>(<span class="string">"qrc:/index.html"</span>)));
view<span class="operator">.</span>resize(<span class="number">1024</span><span class="operator">,</span> <span class="number">750</span>);
view<span class="operator">.</span>show();
PrintHandler handler;
handler<span class="operator">.</span>setPage(view<span class="operator">.</span>page());
<span class="keyword">auto</span> printPreviewShortCut <span class="operator">=</span> <span class="keyword">new</span> <span class="type">QShortcut</span>(<span class="type">QKeySequence</span>(<span class="type">Qt</span><span class="operator">::</span>CTRL <span class="operator">+</span> <span class="type">Qt</span><span class="operator">::</span>Key_P)<span class="operator">,</span> <span class="operator">&</span>view);
<span class="keyword">auto</span> printShortCut <span class="operator">=</span> <span class="keyword">new</span> <span class="type">QShortcut</span>(<span class="type">QKeySequence</span>(<span class="type">Qt</span><span class="operator">::</span>CTRL <span class="operator">+</span> <span class="type">Qt</span><span class="operator">::</span>SHIFT <span class="operator">+</span> <span class="type">Qt</span><span class="operator">::</span>Key_P)<span class="operator">,</span> <span class="operator">&</span>view);
<span class="type">QObject</span><span class="operator">::</span>connect(printPreviewShortCut<span class="operator">,</span> <span class="operator">&</span><span class="type">QShortcut</span><span class="operator">::</span>activated<span class="operator">,</span> <span class="operator">&</span>handler<span class="operator">,</span> <span class="operator">&</span>PrintHandler<span class="operator">::</span>printPreview);
<span class="type">QObject</span><span class="operator">::</span>connect(printShortCut<span class="operator">,</span> <span class="operator">&</span><span class="type">QShortcut</span><span class="operator">::</span>activated<span class="operator">,</span> <span class="operator">&</span>handler<span class="operator">,</span> <span class="operator">&</span>PrintHandler<span class="operator">::</span>print);
</pre>
<a name="print-handler"></a>
<h2 id="print-handler">Print Handler</h2>
<p>In the <code>PrintHandler</code> function, we first implement <code>printPreview()</code>, where we instantiate QPrinter together with QPrintPreviewDialog. We need the QPrintPreviewDialog::paintRequested handle to generate a set of preview pages.</p>
<pre class="cpp">
<span class="type">void</span> PrintHandler<span class="operator">::</span>printPreview()
{
<span class="keyword">if</span> (<span class="operator">!</span>m_page)
<span class="keyword">return</span>;
<span class="keyword">if</span> (m_inPrintPreview)
<span class="keyword">return</span>;
m_inPrintPreview <span class="operator">=</span> <span class="keyword">true</span>;
<span class="type">QPrinter</span> printer;
<span class="type">QPrintPreviewDialog</span> preview(<span class="operator">&</span>printer<span class="operator">,</span> m_page<span class="operator">-</span><span class="operator">></span>view());
connect(<span class="operator">&</span>preview<span class="operator">,</span> <span class="operator">&</span><span class="type">QPrintPreviewDialog</span><span class="operator">::</span>paintRequested<span class="operator">,</span>
<span class="keyword">this</span><span class="operator">,</span> <span class="operator">&</span>PrintHandler<span class="operator">::</span>printDocument);
preview<span class="operator">.</span>exec();
m_inPrintPreview <span class="operator">=</span> <span class="keyword">false</span>;
}
</pre>
<p>Now we can implement the <code>PrintHandler::printDocument()</code> slot, which is called in response to the QPrintPreviewDialog::paintRequested signal.</p>
<pre class="cpp">
<span class="type">void</span> PrintHandler<span class="operator">::</span>printDocument(<span class="type">QPrinter</span> <span class="operator">*</span>printer)
{
<span class="type">QEventLoop</span> loop;
bool result;
<span class="keyword">auto</span> printPreview <span class="operator">=</span> <span class="operator">[</span><span class="operator">&</span><span class="operator">]</span>(bool success) { result <span class="operator">=</span> success; loop<span class="operator">.</span>quit(); };
m_page<span class="operator">-</span><span class="operator">></span>print(printer<span class="operator">,</span> std<span class="operator">::</span>move(printPreview));
loop<span class="operator">.</span>exec();
<span class="keyword">if</span> (<span class="operator">!</span>result) {
<span class="type">QPainter</span> painter;
<span class="keyword">if</span> (painter<span class="operator">.</span>begin(printer)) {
<span class="type">QFont</span> font <span class="operator">=</span> painter<span class="operator">.</span>font();
font<span class="operator">.</span>setPixelSize(<span class="number">20</span>);
painter<span class="operator">.</span>setFont(font);
painter<span class="operator">.</span>drawText(<span class="type">QPointF</span>(<span class="number">10</span><span class="operator">,</span><span class="number">25</span>)<span class="operator">,</span>
<span class="type">QStringLiteral</span>(<span class="string">"Could not generate print preview."</span>));
painter<span class="operator">.</span>end();
}
}
}
</pre>
<p>To do actual painting on a printer, we call the <a href="qwebenginepage.html#print">QWebEnginePage::print</a>() function. Because this call blocks the main event loop, we need to create a local one. We begin the local event loop by calling QEventLoop::exec(). When the local event loop terminates, we check for <code>result</code> and report any errors that occurred.</p>
<p>The last function we implement, <code>PrintHandler::print()</code>, is trivial, because it simply opens QPrintDialog and calls the previously implemented <code>PrintHandler::printDocument()</code>.</p>
<pre class="cpp">
<span class="type">void</span> PrintHandler<span class="operator">::</span>print()
{
<span class="type">QPrinter</span> printer(<span class="type">QPrinter</span><span class="operator">::</span>HighResolution);
<span class="type">QPrintDialog</span> dialog(<span class="operator">&</span>printer<span class="operator">,</span> m_page<span class="operator">-</span><span class="operator">></span>view());
<span class="keyword">if</span> (dialog<span class="operator">.</span>exec() <span class="operator">!</span><span class="operator">=</span> <span class="type">QDialog</span><span class="operator">::</span>Accepted)
<span class="keyword">return</span>;
printDocument(<span class="operator">&</span>printer);
}
</pre>
<p>Files:</p>
<ul>
<li><a href="qtwebengine-webenginewidgets-printme-data-data-qrc.html">webenginewidgets/printme/data/data.qrc</a></li>
<li><a href="qtwebengine-webenginewidgets-printme-data-icon-svg.html">webenginewidgets/printme/data/icon.svg</a></li>
<li><a href="qtwebengine-webenginewidgets-printme-data-index-html.html">webenginewidgets/printme/data/index.html</a></li>
<li><a href="qtwebengine-webenginewidgets-printme-data-style-css.html">webenginewidgets/printme/data/style.css</a></li>
<li><a href="qtwebengine-webenginewidgets-printme-main-cpp.html">webenginewidgets/printme/main.cpp</a></li>
<li><a href="qtwebengine-webenginewidgets-printme-printhandler-cpp.html">webenginewidgets/printme/printhandler.cpp</a></li>
<li><a href="qtwebengine-webenginewidgets-printme-printhandler-h.html">webenginewidgets/printme/printhandler.h</a></li>
<li><a href="qtwebengine-webenginewidgets-printme-printme-pro.html">webenginewidgets/printme/printme.pro</a></li>
</ul>
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<!-- @@@webenginewidgets/printme -->
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>
Mageia
>
7
>
armv7hl
>
media
>
core-updates
>
by-pkgid
>
433eb9daba9f45efee96fd578b74d021
>
files
>
389
