Couldn't figure out how to prompt to save on window exit (red X)

[ianstewart1]

We worked on trying to cancel the lambda function that assigns a handler for closing primaryStage, but were unable to figure out how to cancel the WindowEvent without throwing an exception that we couldn't track down.

[milloypr]

https://stackoverflow.com/questions/31540500/alert-box-for-when-user-attempts-to-close-application-using-setoncloserequest-in