I just posted this one in comp.lang.lisp, but after thinking about it a bit, perhaps it is lisp implementation specific to sbcl, so I post it here also...

I'm a newcomer to lisp and I have a few questions I am running into 
during the course of my prototyping.. 

It would be extremely useful to be able to run a function from the 
repl that executes some even-driven user-interface in the background, 
while control is returned to the repl so that I can continue to issues 
more lisp function calls interactively (that affect the running user- 

To illustrate: 

Current Behavior 

* ( display-graphics-window )     ; this function blocks because the graphics window has it's own event loop. 

*                                 ; returns to  REPL only after user closes window and function returns 

Desired Behavior 

*  ("some-exec-function" (display-graphics-window))    ; function runs graphics window in background 
*                                                      ; function returns immediately with graphics window running 
*  (set-background .5 .5 .5)                           ;hypothetical function to set background color of window 

There may be some parameters missing (like a window id or name), but 
this is the idea.  I'm wondering if I need thread support in my lisp 
compiler (sbcl) to do this ?  - or perhaps there is an easier way. 
"set-background" needs to access all the data in the context created 
by (display-graphics-window). 

Thanks in advance...