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<?xml version="1.0" encoding="UTF-8"?>
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  <title>Zoom Line Example | Qt Charts 5.9</title>
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<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>
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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="#customizing-zooming-effects">Customizing Zooming Effects</a></li>
</ul>
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<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">&lt;</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">&lt;</span><span class="operator">&lt;</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">&gt;</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">&gt;</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">&gt;</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">&gt;</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">&lt;</span><span class="type">QGestureEvent</span> <span class="operator">*</span><span class="operator">&gt;</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">&gt;</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">&lt;</span><span class="type">QPanGesture</span> <span class="operator">*</span><span class="operator">&gt;</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">&gt;</span>delta()<span class="operator">.</span>x())<span class="operator">,</span> pan<span class="operator">-</span><span class="operator">&gt;</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">&gt;</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">&lt;</span><span class="type">QPinchGesture</span> <span class="operator">*</span><span class="operator">&gt;</span>(gesture);
          <span class="keyword">if</span> (pinch<span class="operator">-</span><span class="operator">&gt;</span>changeFlags() <span class="operator">&amp;</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">&gt;</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>
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