ways to exit appl.

Hi!
I am stuck. I want the program to save certain data and clear some files at exit. I know how to do that using a PushButton (save data, delete files, exit). But I have no idea how to do that if a user presses X button in the top right corner of the window (Windows, but I think other OS have similar GUI).
Can somebody please at least point me in the right direction?

TNX,
Luka

Implement closeEvent() in your main widget. Check out this too.