title: How to disable the close button of window using Qt?
body: <p>I want to disable the close button on the window (main application window) when an operation starts so user can't exit the application and enable it again when the operation is complete. How can I do that in Qt application? My platform is windows 7.</p>
  
  <p>Alternatively I could show a message if user press close button and exiting application that a process is running in the background and abort closing the application.</p>
  
  <p>How can I do either?</p>