<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <!-- examples-zoomlinechart.qdoc --> <title>Zoom Line Example | Qt Charts 5.9</title> <link rel="stylesheet" type="text/css" href="style/offline-simple.css" /> <script type="text/javascript"> document.getElementsByTagName("link").item(0).setAttribute("href", "style/offline.css"); // loading style sheet breaks anchors that were jumped to before // so force jumping to anchor again setTimeout(function() { var anchor = location.hash; // need to jump to different anchor first (e.g. none) location.hash = "#"; setTimeout(function() { location.hash = anchor; }, 0); }, 0); </script> </head> <body> <div class="header" id="qtdocheader"> <div class="main"> <div class="main-rounded"> <div class="navigationbar"> <table><tr> <td >Qt 5.9</td><td ><a href="qtcharts-index.html">Qt Charts</a></td><td ><a href="qtcharts-examples.html">Qt Charts Examples</a></td><td >Zoom Line Example</td></tr></table><table class="buildversion"><tr> <td id="buildversion" width="100%" align="right">Qt 5.9.4 Reference Documentation</td> </tr></table> </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="#customizing-zooming-effects">Customizing Zooming Effects</a></li> </ul> </div> <div class="sidebar-content" id="sidebar-content"></div></div> <h1 class="title">Zoom Line Example</h1> <span class="subtitle"></span> <!-- $$$zoomlinechart-description --> <div class="descr"> <a name="details"></a> <p>The example shows how to create your own custom zooming effect with QRubberBand by using a mouse and how to use touch gestures for paning and zooming.</p> <p class="centerAlign"><img src="images/examples_zoomlinechart1.png" alt="" /></p><p class="centerAlign"><img src="images/examples_zoomlinechart2.png" alt="" /></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="customizing-zooming-effects"></a> <h2 id="customizing-zooming-effects">Customizing Zooming Effects</h2> <p>Let's first create a line series with some example data.</p> <pre class="cpp"> <span class="type"><a href="qlineseries.html">QLineSeries</a></span> <span class="operator">*</span>series <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qlineseries.html">QLineSeries</a></span>(); <span class="keyword">for</span> (<span class="type">int</span> i <span class="operator">=</span> <span class="number">0</span>; i <span class="operator"><</span> <span class="number">500</span>; i<span class="operator">+</span><span class="operator">+</span>) { <span class="type">QPointF</span> p((<span class="type">qreal</span>) i<span class="operator">,</span> qSin(M_PI <span class="operator">/</span> <span class="number">50</span> <span class="operator">*</span> i) <span class="operator">*</span> <span class="number">100</span>); p<span class="operator">.</span>ry() <span class="operator">+</span><span class="operator">=</span> qrand() <span class="operator">%</span> <span class="number">20</span>; <span class="operator">*</span>series <span class="operator"><</span><span class="operator"><</span> p; } </pre> <p>Then we create a custom chart view by deriving from <a href="qchartview.html">QChartView</a>:</p> <pre class="cpp"> <span class="keyword">class</span> ChartView : <span class="keyword">public</span> <span class="type"><a href="qchartview.html">QChartView</a></span> </pre> <p>We override mouse and key event handling</p> <pre class="cpp"> <span class="keyword">protected</span>: bool viewportEvent(<span class="type">QEvent</span> <span class="operator">*</span>event); <span class="type">void</span> mousePressEvent(<span class="type">QMouseEvent</span> <span class="operator">*</span>event); <span class="type">void</span> mouseMoveEvent(<span class="type">QMouseEvent</span> <span class="operator">*</span>event); <span class="type">void</span> mouseReleaseEvent(<span class="type">QMouseEvent</span> <span class="operator">*</span>event); <span class="type">void</span> keyPressEvent(<span class="type">QKeyEvent</span> <span class="operator">*</span>event); </pre> <p>Then we implement a custom logic for mouse and key events. For example pressing the '+' key will zoom in and pressing the '-' key will zoom out.</p> <pre class="cpp"> <span class="type">void</span> ChartView<span class="operator">::</span>keyPressEvent(<span class="type">QKeyEvent</span> <span class="operator">*</span>event) { <span class="keyword">switch</span> (event<span class="operator">-</span><span class="operator">></span>key()) { <span class="keyword">case</span> <span class="type">Qt</span><span class="operator">::</span>Key_Plus: chart()<span class="operator">-</span><span class="operator">></span>zoomIn(); <span class="keyword">break</span>; <span class="keyword">case</span> <span class="type">Qt</span><span class="operator">::</span>Key_Minus: chart()<span class="operator">-</span><span class="operator">></span>zoomOut(); <span class="keyword">break</span>; </pre> <p>We also create our own <a href="qchart.html">QChart</a>:</p> <pre class="cpp"> <span class="keyword">class</span> Chart : <span class="keyword">public</span> <span class="type"><a href="qchart.html">QChart</a></span> </pre> <p>Where we can handle the gestures:</p> <pre class="cpp"> bool Chart<span class="operator">::</span>sceneEvent(<span class="type">QEvent</span> <span class="operator">*</span>event) { <span class="keyword">if</span> (event<span class="operator">-</span><span class="operator">></span>type() <span class="operator">=</span><span class="operator">=</span> <span class="type">QEvent</span><span class="operator">::</span>Gesture) <span class="keyword">return</span> gestureEvent(<span class="keyword">static_cast</span><span class="operator"><</span><span class="type">QGestureEvent</span> <span class="operator">*</span><span class="operator">></span>(event)); <span class="keyword">return</span> <span class="type"><a href="qchart.html">QChart</a></span><span class="operator">::</span>event(event); } bool Chart<span class="operator">::</span>gestureEvent(<span class="type">QGestureEvent</span> <span class="operator">*</span>event) { <span class="keyword">if</span> (<span class="type">QGesture</span> <span class="operator">*</span>gesture <span class="operator">=</span> event<span class="operator">-</span><span class="operator">></span>gesture(<span class="type">Qt</span><span class="operator">::</span>PanGesture)) { <span class="type">QPanGesture</span> <span class="operator">*</span>pan <span class="operator">=</span> <span class="keyword">static_cast</span><span class="operator"><</span><span class="type">QPanGesture</span> <span class="operator">*</span><span class="operator">></span>(gesture); <span class="type"><a href="qchart.html">QChart</a></span><span class="operator">::</span>scroll(<span class="operator">-</span>(pan<span class="operator">-</span><span class="operator">></span>delta()<span class="operator">.</span>x())<span class="operator">,</span> pan<span class="operator">-</span><span class="operator">></span>delta()<span class="operator">.</span>y()); } <span class="keyword">if</span> (<span class="type">QGesture</span> <span class="operator">*</span>gesture <span class="operator">=</span> event<span class="operator">-</span><span class="operator">></span>gesture(<span class="type">Qt</span><span class="operator">::</span>PinchGesture)) { <span class="type">QPinchGesture</span> <span class="operator">*</span>pinch <span class="operator">=</span> <span class="keyword">static_cast</span><span class="operator"><</span><span class="type">QPinchGesture</span> <span class="operator">*</span><span class="operator">></span>(gesture); <span class="keyword">if</span> (pinch<span class="operator">-</span><span class="operator">></span>changeFlags() <span class="operator">&</span> <span class="type">QPinchGesture</span><span class="operator">::</span>ScaleFactorChanged) <span class="type"><a href="qchart.html">QChart</a></span><span class="operator">::</span>zoom(pinch<span class="operator">-</span><span class="operator">></span>scaleFactor()); } <span class="keyword">return</span> <span class="keyword">true</span>; } </pre> <p>Note that you will need to call grabGesture() to both QMainWindow and <a href="qchart.html">QChart</a>.</p> <p>Files:</p> <ul> <li><a href="qtcharts-zoomlinechart-chart-cpp.html">zoomlinechart/chart.cpp</a></li> <li><a href="qtcharts-zoomlinechart-chart-h.html">zoomlinechart/chart.h</a></li> <li><a href="qtcharts-zoomlinechart-chartview-cpp.html">zoomlinechart/chartview.cpp</a></li> <li><a href="qtcharts-zoomlinechart-chartview-h.html">zoomlinechart/chartview.h</a></li> <li><a href="qtcharts-zoomlinechart-main-cpp.html">zoomlinechart/main.cpp</a></li> <li><a href="qtcharts-zoomlinechart-zoomlinechart-pro.html">zoomlinechart/zoomlinechart.pro</a></li> </ul> </div> <!-- @@@zoomlinechart --> </div> </div> </div> </div> </div> <div class="footer"> <p> <acronym title="Copyright">©</acronym> 2017 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>