on-close (augments, and augmentable only) in frame:register-group-mixin

Called just before the window is closed (e.g., by the window manager). This method is not called by show .

See also can-close?.

• (send a-frame:register-group-mixin on-close void

  First calls the inner method. Next, calls the remove-frame method of the result of group:get-the-frame-group with this as an argument. Finally, unless exit:exiting? returns #t, and if there are no more frames open, it calls exit:exit.