on-exit in frame:basic-mixin
Called by the default application quit handler (as determined by the
application-quit-handler parameter) when the
operating system requests that the application shut down (e.g., when
the Quit menu item is selected in the main application
menu under Mac OS X). In that case, this method is called for the
most recently active top-level window in the initial eventspace, but
only if the window's
can-exit? method first returns true.
( -> voidsend a-frame:basic-mixin on-exit)
Together with
can-exit? this mimics the behavior of
exit:exit.
Calls
exit:on-exit and then queues a callback
to call MzScheme's exit
function. If that returns, it
calls
exit:set-exiting to reset that flag to
#f.