The rootwin extension is a Tk extension (version 8.4 or later) that allows the creation of a Tk widget whose window is the X display's root window. This is useful for writing Tk-based window managers. It is available from Neil McKay's computer page: http://www.eecs.umich.edu/~mckay/computer/index.html . (The rootwin widget is derived from the code written for TkWM.)