How to detect when a window has lost focus?

Vadi2

How to detect when a window has lost focus? I can only find a way to detect when the cursor has left the contents of the window, which is not what I need.

dheerendra

Look for QEvent::FocusIn and QEvent::FocusOut events.

Vadi2

No, that's not it. When I alt+tab out of the window, no FocusOut event is fired. I'm testing with http://doc.qt.io/qt-5/qwindow.html#focusOutEvent.

J.Hilk

QObject::connect(qApp, &QGuiApplication::applicationStateChanged, this, [=](Qt::ApplicationState state){
    qDebug() << state;
});