setClosable
fun setClosable(closable: Boolean): ERROR CLASS: Symbol not found for js.promise.Promise<ERROR CLASS: Symbol not found for js.core.Void>(source)
Sets whether the window's native close button is enabled or not.
Platform-specific
Linux: GTK+ will do its best to convince the window manager not to show a close button. Depending on the system, this function may not have any effect when called on a window that is already visible
iOS / Android: Unsupported.