MousePressEvent called 3 times when double-clicking



  • I have created a class, GraphicPoint, that inherits both QObject and QGraphicsEllipseItem.

    .h file

    @#include <QtWidgets>

    class GraphicPoint : public QObject, public QGraphicsEllipseItem
    {
    Q_OBJECT

    public:
    GraphicPoint(qreal x, qreal y, qreal width, qreal height, QWidget *parent = nullptr);

    signals:
    void clicked();

    private:
    void mousePressEvent(QGraphicsSceneMouseEvent *event);
    };@

    .cpp file

    @#include "graphicpoint.h"

    GraphicPoint::GraphicPoint(qreal x, qreal y, qreal width, qreal height, QWidget *parent) :
    QObject(parent),
    QGraphicsEllipseItem(x, y, width, height, nullptr)
    {
    }

    void GraphicPoint::mousePressEvent(QGraphicsSceneMouseEvent *event){
    event->accept();
    emit clicked();
    }@

    In the main window, I have created a view and a scene and added the point to the scene. Quickly clicking the button twice calls the mousePressEvent 3 times, whereas doing the same a bit slower calls it just 2 times. Here is the main window .cpp file

    @#include "mainwindow.h"

    MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent)
    {
    n = 0;
    view = new QGraphicsView(this);
    scene = new QGraphicsScene(this);
    view->setScene(scene);
    testPoint = new GraphicPoint(0, 0, 10, 10, this);
    connect(testPoint, &GraphicPoint::clicked, this{
    n++;
    qDebug()<<n <<endl;
    });
    scene->addItem(testPoint);
    setCentralWidget(view);
    }@

    After 2 quick clicks, QDebug outputs 3 lines with the numbers 1, 2, 3.

    What can be the reason of this happening? Is there some default doubleclick event that calls the additional mousePressEvent?

    Additional info:

    The main.cpp file is as follows:

    @#include "mainwindow.h"
    #include <QApplication>

    int main(int argc, char *argv[])
    {
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
    }@

    and the mainwindow.h:

    @#include <QtWidgets>
    #include "graphicpoint.h"

    class MainWindow : public QMainWindow
    {
    Q_OBJECT

    public:
    MainWindow(QWidget *parent = 0);

    private:
    QGraphicsView *view;
    QGraphicsScene *scene;
    GraphicPoint *testPoint;
    qint32 n;
    };@


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