QZoomChart.cpp

#include "QZoomChart.h"
#include <QtCharts/QChart>
#include <QtWidgets/QGesture>
#include <QtWidgets/QGraphicsScene>
#include <QtWidgets/QGraphicsView>

QZoomChart::QZoomChart(QGraphicsItem* parent, Qt::WindowFlags wFlags) : QChart(QChart::ChartTypeCartesian, parent, wFlags) {

    // Seems that QGraphicsView (QChartView) does not grab gestures.
    // They can only be grabbed here in the QGraphicsWidget (QChart).
    grabGesture(Qt::PanGesture);
    grabGesture(Qt::PinchGesture);
}

QZoomChart::~QZoomChart() {
}

bool QZoomChart::sceneEvent(QEvent* event) {

    if (event->type() == QEvent::Gesture) {
        return gestureEvent(static_cast<QGestureEvent*>(event));
    }

    return QChart::event(event);
}

bool QZoomChart::gestureEvent(QGestureEvent* event) {

    if (QGesture* gesture = event->gesture(Qt::PanGesture)) {
        QPanGesture* pan = static_cast<QPanGesture*>(gesture);
        QChart::scroll(-(pan->delta().x()), pan->delta().y());
    }

    if (QGesture* gesture = event->gesture(Qt::PinchGesture)) {

        QPinchGesture* pinch = static_cast<QPinchGesture*>(gesture);

        if (pinch->changeFlags() & QPinchGesture::ScaleFactorChanged) {
            QChart::zoom(pinch->scaleFactor());
        }
    }

    return true;
}