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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
#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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