[plt-scheme] mred -z weirdness

I guess I will submit a bug report for this, but in case anyone is
interested in a follow-up: it turns out if you call yield, the GUI
displays like normal, but then doesn't respond to events until you
yield again...   looks like the repl is blocking the process instead of
just the thread?

Doug Orleans writes:
 > When I put these lines from the MrEd manual into a file:
 > 
 >   ;; Make a frame by instantiating the frame% class
 >   (define frame (instantiate frame% ("Example")))
 > 
 >   ;; Make a static text message in the frame
 >   (define msg (instantiate message% ("No events so far..." frame)))
 > 
 >   ;; Make a button in the frame (using keyword-based arguments, for demonstration)
 >   (instantiate button% () (label "Click Me") (parent frame)
 > 	       ;; Callback procedure for a button click
 > 	       (callback (lambda (button event) (send msg set-label "Button click"))))
 > 
 >   ;; Show the frame by calling its show method
 >   (send frame show #t)
 > 
 > and run "mred" and load it with the "File->Load file" menu item, it
 > works fine.  (It works fine with "drscheme" also.)  However, when I
 > run "mred -z" and use the "load" function, I get a blank (empty)
 > window.  This happens in both Linux/X and Windows.