qt5base-lts/examples/touch/pinchzoom/graphicsview.cpp

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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.
**
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**
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** notice, this list of conditions and the following disclaimer.
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** the documentation and/or other materials provided with the
** distribution.
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#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);
}