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<h1 class="title">graphicsview.cpp Example File</h1>
<span class="subtitle">touch/pinchzoom/graphicsview.cpp</span>
<!-- $$$touch/pinchzoom/graphicsview.cpp-description -->
<div class="descr"> <a name="details"></a>
<pre class="cpp">

  <span class="comment">/****************************************************************************
  **
  ** Copyright (C) 2016 The Qt Company Ltd.
  ** Contact: https://www.qt.io/licensing/
  **
  ** This file is part of the examples of the Qt Toolkit.
  **
  ** $QT_BEGIN_LICENSE:BSD$
  ** Commercial License Usage
  ** Licensees holding valid commercial Qt licenses may use this file in
  ** accordance with the commercial license agreement provided with the
  ** Software or, alternatively, in accordance with the terms contained in
  ** a written agreement between you and The Qt Company. For licensing terms
  ** and conditions see https://www.qt.io/terms-conditions. For further
  ** information use the contact form at https://www.qt.io/contact-us.
  **
  ** BSD License Usage
  ** Alternatively, you may use this file under the terms of the BSD license
  ** as follows:
  **
  ** &quot;Redistribution and use in source and binary forms, with or without
  ** modification, are permitted provided that the following conditions are
  ** met:
  **   * Redistributions of source code must retain the above copyright
  **     notice, this list of conditions and the following disclaimer.
  **   * Redistributions in binary form must reproduce the above copyright
  **     notice, this list of conditions and the following disclaimer in
  **     the documentation and/or other materials provided with the
  **     distribution.
  **   * Neither the name of The Qt Company Ltd nor the names of its
  **     contributors may be used to endorse or promote products derived
  **     from this software without specific prior written permission.
  **
  **
  ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  ** &quot;AS IS&quot; AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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  ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.&quot;
  **
  ** $QT_END_LICENSE$
  **
  ****************************************************************************/</span>

  <span class="preprocessor">#include &quot;graphicsview.h&quot;</span>

  <span class="preprocessor">#include &lt;QScrollBar&gt;</span>
  <span class="preprocessor">#include &lt;QTouchEvent&gt;</span>

  GraphicsView<span class="operator">::</span>GraphicsView(<span class="type"><a href="qgraphicsscene.html">QGraphicsScene</a></span> <span class="operator">*</span>scene<span class="operator">,</span> <span class="type"><a href="qwidget.html">QWidget</a></span> <span class="operator">*</span>parent)
      : <span class="type"><a href="qgraphicsview.html">QGraphicsView</a></span>(scene<span class="operator">,</span> parent)<span class="operator">,</span> totalScaleFactor(<span class="number">1</span>)
  {
      viewport()<span class="operator">-</span><span class="operator">&gt;</span>setAttribute(<span class="type"><a href="../qtcore/qt.html">Qt</a></span><span class="operator">::</span>WA_AcceptTouchEvents);
      setDragMode(ScrollHandDrag);
  }

  bool GraphicsView<span class="operator">::</span>viewportEvent(<span class="type"><a href="../qtcore/qevent.html">QEvent</a></span> <span class="operator">*</span>event)
  {
      <span class="keyword">switch</span> (event<span class="operator">-</span><span class="operator">&gt;</span>type()) {
      <span class="keyword">case</span> <span class="type"><a href="../qtcore/qevent.html">QEvent</a></span><span class="operator">::</span>TouchBegin:
      <span class="keyword">case</span> <span class="type"><a href="../qtcore/qevent.html">QEvent</a></span><span class="operator">::</span>TouchUpdate:
      <span class="keyword">case</span> <span class="type"><a href="../qtcore/qevent.html">QEvent</a></span><span class="operator">::</span>TouchEnd:
      {
          <span class="type"><a href="../qtgui/qtouchevent.html">QTouchEvent</a></span> <span class="operator">*</span>touchEvent <span class="operator">=</span> <span class="keyword">static_cast</span><span class="operator">&lt;</span><span class="type"><a href="../qtgui/qtouchevent.html">QTouchEvent</a></span> <span class="operator">*</span><span class="operator">&gt;</span>(event);
          <span class="type"><a href="../qtcore/qlist.html">QList</a></span><span class="operator">&lt;</span><span class="type"><a href="../qtgui/qtouchevent.html">QTouchEvent</a></span><span class="operator">::</span>TouchPoint<span class="operator">&gt;</span> touchPoints <span class="operator">=</span> touchEvent<span class="operator">-</span><span class="operator">&gt;</span>touchPoints();
          <span class="keyword">if</span> (touchPoints<span class="operator">.</span>count() <span class="operator">=</span><span class="operator">=</span> <span class="number">2</span>) {
              <span class="comment">// determine scale factor</span>
              <span class="keyword">const</span> <span class="type"><a href="../qtgui/qtouchevent.html">QTouchEvent</a></span><span class="operator">::</span>TouchPoint <span class="operator">&amp;</span>touchPoint0 <span class="operator">=</span> touchPoints<span class="operator">.</span>first();
              <span class="keyword">const</span> <span class="type"><a href="../qtgui/qtouchevent.html">QTouchEvent</a></span><span class="operator">::</span>TouchPoint <span class="operator">&amp;</span>touchPoint1 <span class="operator">=</span> touchPoints<span class="operator">.</span>last();
              <span class="type"><a href="../qtcore/qtglobal.html#qreal-typedef">qreal</a></span> currentScaleFactor <span class="operator">=</span>
                      <span class="type"><a href="../qtcore/qlinef.html">QLineF</a></span>(touchPoint0<span class="operator">.</span>pos()<span class="operator">,</span> touchPoint1<span class="operator">.</span>pos())<span class="operator">.</span>length()
                      <span class="operator">/</span> <span class="type"><a href="../qtcore/qlinef.html">QLineF</a></span>(touchPoint0<span class="operator">.</span>startPos()<span class="operator">,</span> touchPoint1<span class="operator">.</span>startPos())<span class="operator">.</span>length();
              <span class="keyword">if</span> (touchEvent<span class="operator">-</span><span class="operator">&gt;</span>touchPointStates() <span class="operator">&amp;</span> <span class="type"><a href="../qtcore/qt.html">Qt</a></span><span class="operator">::</span>TouchPointReleased) {
                  <span class="comment">// if one of the fingers is released, remember the current scale</span>
                  <span class="comment">// factor so that adding another finger later will continue zooming</span>
                  <span class="comment">// by adding new scale factor to the existing remembered value.</span>
                  totalScaleFactor <span class="operator">*</span><span class="operator">=</span> currentScaleFactor;
                  currentScaleFactor <span class="operator">=</span> <span class="number">1</span>;
              }
              setTransform(<span class="type"><a href="../qtgui/qtransform.html">QTransform</a></span>()<span class="operator">.</span>scale(totalScaleFactor <span class="operator">*</span> currentScaleFactor<span class="operator">,</span>
                                              totalScaleFactor <span class="operator">*</span> currentScaleFactor));
          }
          <span class="keyword">return</span> <span class="keyword">true</span>;
      }
      <span class="keyword">default</span>:
          <span class="keyword">break</span>;
      }
      <span class="keyword">return</span> <span class="type"><a href="qgraphicsview.html">QGraphicsView</a></span><span class="operator">::</span>viewportEvent(event);
  }

</pre>
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<!-- @@@touch/pinchzoom/graphicsview.cpp -->
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