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

Called just before the window might be closed (e.g., by the window manager). If #f is returned, the window is not closed, otherwise on-close is called and the window is closed (i.e., the window is hidden, like calling show with #f).

This method is not called by show .

• (send a-frame:register-group-mixin can-close? bool

  Calls the inner method, with a default of #t. If that returns #t, it checks for one of the these three conditions:

  • exit:exiting? returns #t

  • there is more than one frame in the group returned by group:get-the-frame-group, or

  • the procedure exit:user-oks-exit returns #t.

  If any of those conditions hold, the method returns #t.