onCloseAttempt  
  fun onCloseAttempt(connectFlags: <Error class: unknown class> = ConnectFlags(0u), handler: () -> Unit): <Error class: unknown class>(source)
Emitted when the close button or shortcut is used, or method@Dialog.close is called while property@Dialog:can-close is set to FALSE.
Since
1.5
Parameters
connectFlags 
a combination of ConnectFlags
handler
the Callback to connect