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/****************************************************************************
**
** 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:
**
** "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
** "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)
{
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);
const auto touchPoints = touchEvent->points();
if (touchPoints.count() == 2) {
// determine scale factor
const QEventPoint &touchPoint0 = touchPoints.first();
const QEventPoint &touchPoint1 = touchPoints.last();
qreal currentScaleFactor =
QLineF(touchPoint0.position(), touchPoint1.position()).length()
/ QLineF(touchPoint0.pressPosition(), touchPoint1.pressPosition()).length();
if (touchEvent->touchPointStates() & QEventPoint::Released) {
// 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::fromScale(totalScaleFactor * currentScaleFactor,
totalScaleFactor * currentScaleFactor));
}
return true;
}
default:
break;
}
return QGraphicsView::viewportEvent(event);
}
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