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.

• (send a-frame:basic-mixin on-exit void

  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.