code: func (w *Window) Closed() bool {
  	var closed bool
  	mainthread.Call(func() {
  		closed = w.window.ShouldClose()
  	})
  	return closed
  }
docs: // Closed returns the closed flag of the Window, which reports whether the Window should be closed.
  //
  // The closed flag is automatically set when a user attempts to close the Window.