Earlier quoted context omitted.
Actually there are lots of X11 window managers in many languages. If we look at Common Lisp, window managers are not new. https://common-lisp.net/project/eclipse/ https://common-lisp.net/project/clfswm/ Well known is Stumpwm: https://github.com/stumpwm/stumpwm/wiki It's easy to write a minimal WM in Common Lisp: http://paste.lisp.org/display/19072
I'm insecure and desperate for anything I can pass off as a "killer app" for Forth and pie menus, so here's an X10 window manager (yes, X10 not X11) with pie menus that's extensible in Forth: http://donhopkins.com/home/archive/piemenu/uwm/fuwm-main.f
Cool. Sure there was X10 in Lisp, too. ;-)
Robert Scheifler wrote an X10 server for the Lisp Machine.