Click on 'X' of the MainWindow doesn't call cleanClose

[egolus]

the function gets called, when the window is closed by the menu-entry Exit application or the Hotkey Ctrl+Q but not by the X Button on the top-right of the window

I didn't even know that you save the window position until I found the call to QtCore.QSettings in your code, because I allways closed the window by clicking the X

[baudren]

Indeed, the closeEvent function was not overwritten. Fixed now!