10 Exit

(exit:exiting?) → boolean?

Returns #t to indicate that an exit operation is taking place. Does not indicate that the app will actually exit, since the user may cancel the exit.

See also exit:insert-on-callback and exit:insert-can?-callback.

(exit:set-exiting exiting?) → void?

exiting? : boolean?

Sets a flag that affects the result of exit:exiting?.

(exit:insert-on-callback callback) → (-> void?)

callback : (-> void?)

Adds a callback to be called when exiting. This callback must not fail. If a callback should stop an exit from happening, use exit:insert-can?-callback.

(exit:insert-can?-callback callback) → (-> void?)

callback : (-> boolean?)

Use this function to add a callback that determines if an attempted exit can proceed. This callback should not clean up any state, since another callback may veto the exit. Use exit:insert-on-callback for callbacks that clean up state.

(exit:can-exit?) → boolean?

Calls the “can-callbacks” and returns their results. See exit:insert-can?-callback for more information.

(exit:on-exit) → void?

Calls the “on-callbacks”. See exit:insert-on-callback for more information.

(exit:exit) → any

exit:exit performs four actions:

• sets the result of the exit:exiting? function to #t.

• invokes the exit-callbacks, with exit:can-exit? if none of the “can?” callbacks return #f,

• invokes exit:on-exit and then

• queues a callback that calls exit (a mzscheme procedure) and (if exit returns) sets the result of exit:exiting? back to #t.

(exit:user-oks-exit) → boolean?

Opens a dialog that queries the user about exiting. Returns the user’s decision.