[racket] Notification when window is closed

On Sun, Aug 5, 2012 at 1:33 PM, Robby Findler
<robby at eecs.northwestern.edu> wrote:
> No, this second call to Run does the equivalent of 'force quit' on the
> previous program, which is what closes the old windows. Technically,
> it is calling custodian-shutdown-all on a custodian that controls all
> things the previous run created.
>
> Is there some external state that isn't getting cleaned up?

Yes. I'm using a DLL and I need  to call a (kind of) shutdown
function when the window is closed, either because the user
clicked the close button or because he clicked the Run button
again.