Interact with SDL window live, per http://code.google.com/p/lispbuilder/wiki/PortableInteractiveDevelopment

gistfile1.lisp

(defun draw-frame ()
  (sdl:clear-display sdl:*black*)
  (sdl:draw-box-* 0 0 100 100)
  (sdl:update-display))

(sdl:with-init ()
  (sdl:window 1024 768)
  (sdl:with-events ()
    (:quit-event () t)
    (:idle ()
           (let ((connection
                  (or swank::*emacs-connection* (swank::default-connection))))
             (when (and connection (not (eql swank:*communication-style* :spawn)))
               (swank::handle-requests connection t)))
           (draw-frame))))