code: func (b *Button) InputHandler() func(event *tcell.EventKey, setFocus func(p Primitive)) {
  	return b.WrapInputHandler(func(event *tcell.EventKey, setFocus func(p Primitive)) {
  		// Process key event.
  		switch key := event.Key(); key {
  		case tcell.KeyEnter: // Selected.
  			if b.selected != nil {
  				b.selected()
  			}
  		case tcell.KeyBacktab, tcell.KeyTab, tcell.KeyEscape: // Leave. No action.
  			if b.blur != nil {
  				b.blur(key)
  			}
  		}
  	})
  }
docs: // InputHandler returns the handler for this primitive.