How to capture PyQt5 QMainWindow losing focus

Question

What I want to achieve: if a user clicks outside of the QMainWindow the window should hide.

How I tried to to tackle this problem: find a way to determine if the QMainWindow lost focus, and if so, hide the window using a followup function.

Unfortunately I can not totally grasp how to achieve this.

It can be done using the flag Qt::Popup but than I am not able to give any keyboard input to the widget my QMainWindow contains.

Answer 1

void QApplication::focusChanged(QWidget *old, QWidget *now)

This signal is emitted when the widget that has keyboard focus changed from old to now, i.e., because the user pressed the tab-key, clicked into a widget or changed the active window. Both old and now can be the null-pointer.

import sys
from PyQt5 import QtCore, QtGui, QtWidgets


class MyWin(QtWidgets.QMainWindow):
    def __init__(self):
        super().__init__()
        
        self.setFocus()
        QtWidgets.qApp.focusChanged.connect(self.on_focusChanged)       

    @QtCore.pyqtSlot("QWidget*", "QWidget*")
    def on_focusChanged(self, old, now):

        if now == None:
            print(f"\nwindow is the active window: {self.isActiveWindow()}")
            
            # window lost focus
            # do what you want
            
            self.setWindowState(QtCore.Qt.WindowMinimized)
            
        else: print(f"window is the active window: {self.isActiveWindow()}")
        

if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = MyWin() 
    MainWindow.show()
    sys.exit(app.exec_())