int Tk_RestackWindow(tkwin, aboveBelow, other)
Tk_RestackWindow changes the stacking order of window relative to its siblings. If other is specified as NULL then window is repositioned at the top or bottom of its stacking order, depending on whether aboveBelow is Above or Below. If other has a non-NULL value then window is repositioned just above or below other.
The aboveBelow argument must have one of the symbolic values Above or Below. Both of these values are defined by the include file <X11/Xlib.h>.