Question

I have an application in Qt5.0 in which I have installed an event filter to listen for single mouse clicks that looks like this:

bool MainView::eventFilter(QObject *obj, QEvent *event)
{
if (event->type() == QEvent::MouseButtonPress)
  {
    QMouseEvent *mouseEvent = static_cast<QMouseEvent*>(event);
    int mx=mouseEvent->pos().x(),my=mouseEvent->pos().y();

    qDebug() << QString::number(mx)<<" "<<QString::number(my);
...
}
}

Everytime I click, the function gets called multiple times and it returns a number of values in a wide range, often in range of around +/-50 from the actual value. Could anyone please explain as to why this might be happening or if anyone has faced a similar problem. The event filter has been installed in the constructor as qApp->installEventFilter(this);

Answer 1

If the event has not been handled by an object, it’s propagated to the object’s parent and so on. That’s why you catch several mouse events.

And you can always get what kind of object is being watched by the event filter:

bool MainView::eventFilter(QObject *obj, QEvent *event)
{
    ...
    qDebug() << obj->metaObject()->className();
    ...
}