SDK: LR Plugin - How to notify before closing a window in lua?

[P.Nutthakan]

I would like when the user presses one of these three buttons to notify you that you want to close this window, how to code this? I am currently using lua to write plugins.

[johnrellis]

If you want to ask the user if they really want to close the window and give them an option to cancel the closing, you can't do that with a modal dialog (LrDialogs.presentModalDialog).  You'll know after the fact that the user has closed the window, when presentModalDialog() returns.

You could use a floating dialog (LrDialogs.presentFloatingDialog), which doesn't provide any built-in buttons, and you'd implement your own OK and Cancel buttons.  But there's no way to intervene when the user clicks the "x" in the corner -- you'll just get notified after the dialog closes.