code: func (w *Window) StackSibling(sibling xproto.Window, mode byte) {
  	xproto.ConfigureWindow(w.X.Conn(), w.Id,
  		xproto.ConfigWindowSibling|xproto.ConfigWindowStackMode,
  		[]uint32{uint32(sibling), uint32(mode)})
  }
docs: // StackSibling issues a configure request to change the sibling and stack mode
  // of Window.
  // If you're using a window manager that supports EWMH, you may want to try
  // and use ewmh.RestackWindowExtra instead. Although this should still work.
  // 'mode' values can be found as constants in xgb/xproto with the prefix
  // StackMode.
  // 'sibling' refers to the sibling window in the stacking order through which
  // 'mode' is interpreted. Note that 'sibling' should be taken literally. A
  // window can only be stacked with respect to a *sibling* in the window tree.
  // This means that a client window that has been wrapped in decorations cannot
  // be stacked with respect to another client window. (This is why you should
  // use ewmh.RestackWindowExtra instead.)