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+/****************************************************************************
+**
+** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the examples of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** You may use this file under the terms of the BSD license as follows:
+**
+** "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 Nokia Corporation and its Subsidiary(-ies) 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
+** "AS IS" 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,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "graphicsview.h"
+
+#include <QScrollBar>
+#include <QTouchEvent>
+
+GraphicsView::GraphicsView(QGraphicsScene *scene, QWidget *parent)
+ : QGraphicsView(scene, parent), totalScaleFactor(1)
+{
+ viewport()->setAttribute(Qt::WA_AcceptTouchEvents);
+ setDragMode(ScrollHandDrag);
+}
+
+bool GraphicsView::viewportEvent(QEvent *event)
+{
+ switch (event->type()) {
+ case QEvent::TouchBegin:
+ case QEvent::TouchUpdate:
+ case QEvent::TouchEnd:
+ {
+ QTouchEvent *touchEvent = static_cast<QTouchEvent *>(event);
+ QList<QTouchEvent::TouchPoint> touchPoints = touchEvent->touchPoints();
+ if (touchPoints.count() == 2) {
+ // determine scale factor
+ const QTouchEvent::TouchPoint &touchPoint0 = touchPoints.first();
+ const QTouchEvent::TouchPoint &touchPoint1 = touchPoints.last();
+ qreal currentScaleFactor =
+ QLineF(touchPoint0.pos(), touchPoint1.pos()).length()
+ / QLineF(touchPoint0.startPos(), touchPoint1.startPos()).length();
+ if (touchEvent->touchPointStates() & Qt::TouchPointReleased) {
+ // if one of the fingers is released, remember the current scale
+ // factor so that adding another finger later will continue zooming
+ // by adding new scale factor to the existing remembered value.
+ totalScaleFactor *= currentScaleFactor;
+ currentScaleFactor = 1;
+ }
+ setTransform(QTransform().scale(totalScaleFactor * currentScaleFactor,
+ totalScaleFactor * currentScaleFactor));
+ }
+ return true;
+ }
+ default:
+ break;
+ }
+ return QGraphicsView::viewportEvent(event);
+}