code: func (b *Box) SetInputCapture(capture func(event *tcell.EventKey) *tcell.EventKey) *Box {
  	b.inputCapture = capture
  	return b
  }
docs: // SetInputCapture installs a function which captures key events before they are
  // forwarded to the primitive's default key event handler. This function can
  // then choose to forward that key event (or a different one) to the default
  // handler by returning it. If nil is returned, the default handler will not
  // be called.
  //
  // Providing a nil handler will remove a previously existing handler.
  //
  // Note that this function will not have an effect on primitives composed of
  // other primitives, such as Form, Flex, or Grid. Key events are only captured
  // by the primitives that have focus (e.g. InputField) and only one primitive
  // can have focus at a time. Composing primitives such as Form pass the focus on
  // to their contained primitives and thus never receive any key events
  // themselves. Therefore, they cannot intercept key events.