Add event to intercept and prevent window closing

[gadamsgh]

The window class emits an event when the window is already closed. I'd like to have the ability to intercept the attempted close and cancel it if desired. The primary use case would be to allow certain types of cleanup/saving code on the launched website to finish execution before terminating the window/process.

Could this be added as an enhancement?

[pavelfeldman]

Would onbeforeunload-alike behavior work for you? You can call a binding / rpc method from within the handler synchronously, it should work.