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I can't find mouse wheel scroll events for zoom graphics in QChartView

I have QChartView on the program window. There are arrays of data that correctly shown on chart as QLineSeries (curves of temperature vs time). I can't find mousewheel events for 'mousewheelup zoom-in' and 'mousewheeldown zoom-out' on QChartView? Need ability to zoom by only vertical direction, like a setRubberBand(QChartView::VerticalRubberBand) but only by mousewheel scroll. Need help

setRubberBand(QChartView::VerticalRubberBand)

2 Answers
2

QChartView is a QWidget so you could implement that logic using the wheelEvent() method:

QChartView

QWidget

wheelEvent()

#include <QApplication>
#include <QChartView>
#include <QLineSeries>
#include <random>

QT_CHARTS_USE_NAMESPACE

class ChartView : public QChartView

public:
using QChartView::QChartView;
enum DirectionZoom
NotZoom,
VerticalZoom,
HorizontalZoom,
BothDirectionZoom = VerticalZoom ;
DirectionZoom directionZoom() const
return mDirectionZoom;

void setDirectionZoom(const DirectionZoom &directionZoom)
mDirectionZoom = directionZoom;


protected:
void wheelEvent(QWheelEvent *event)

if(chart() && mDirectionZoom != NotZoom)
const qreal factor = 1.001;
QRectF r = chart()->plotArea();
QPointF c = r.center();
qreal val = std::pow(factor, event->delta());
if(mDirectionZoom & VerticalZoom)
r.setHeight(r.height()*val);
if (mDirectionZoom & HorizontalZoom)
r.setWidth(r.width()*val);

r.moveCenter(c);
chart()->zoomIn(r);

QChartView::wheelEvent(event);

private:
DirectionZoom mDirectionZoom = NotZoom;
;

int main(int argc, char *argv)

QApplication a(argc, argv);
QChart *chart = new QChart();
chart->legend()->hide();
chart->setTitle("Simple line chart example");
std::random_device rd;
std::mt19937 rng(rd());
std::uniform_int_distribution<int> uni(0, 10);

for(size_t i=0; i< 5; i++)
QLineSeries *series = new QLineSeries();
for(size_t j=0; j < 10; j++)
*series << QPointF(j, uni(rng));

chart->addSeries(series);

chart->createDefaultAxes();

ChartView chartView(chart);
chartView.setDirectionZoom(ChartView::VerticalZoom);
chartView.setRenderHint(QPainter::Antialiasing);
chartView.resize(640, 480);
chartView.show();

return a.exec();



const qreal factor = 1/1.001;

QChartView inherits from QGraphicsView which offers QGraphicsSceneWheelEvent

QChartView

QGraphicsView

QGraphicsSceneWheelEvent

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