capi:apply-in-pane-process

Hello all,

I'm doing some work with OpenGL and Lispworks (on OS X).  I have a slot in my
opengl-pane called redraw-p  which is non-nil when the pane needs to be redrawn.
I've written a function, post-redisplay, which does the following:

(defun post-redisplay (pane rect)  ;; rect is the region to be redrawn.
  "Redisplays the pane, but only if the request has not already been made."
  (with-slots (redraw-p redraw-rect) pane
    (if redraw-p
      (setf redraw-rect (rectangle-union redraw-rect rect))  ;;
include rect in the area to be redrawn
      (progn
        (setf redraw-p    t
              redraw-rect  rect)
        (capi:apply-in-pane-process pane #'redraw-pane pane)))))

The idea, here, is that if I made two calls to post-redisplay before
the redraw-pane function was called, then rather than redrawing two
regions consecutively, I could combine the two regions into one and
draw them both at the same time.

The problem that I've run into, is that I had (perhaps incorrectly)
assumed that a call to capi:apply-in-pane-process would put the
draw-object call into some sort of queue of actions to perform so that
the following *could* have the desired behavior of not making
consecutive calls to redraw-pane

(progn
  (post-redisplay p 10 50 10 10)
  (post-redisplay p 100 100 10 10))

It seems, however, that appy-in-pane-process when called from the same
process that it will be applied into has the effect of executing
immediately.  Is this the correct behaviour?  And if so, might you
have any suggestions for achieving the desired results (without
creating a new process to watch for the redraw-p slot to change)

Thanks!
Andrew