12 Exit

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On this page:

exit: exiting?
exit: set-exiting
exit: insert-on-callback
exit: insert-can?-callback
exit: can-exit?
exit: on-exit
exit: exit
exit: user-oks-exit

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### 12`` Exit

> procedure (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.

> procedure (exit:set-exiting exiting?) → void?
> exiting? : boolean?

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

> procedure (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.

> procedure (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.

> procedure (exit:can-exit?) → boolean?

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

> procedure (exit:on-exit) → void?

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

> procedure (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 racket procedure) and (if exit returns) sets the result of exit:exiting? back to #t.

> procedure (exit:user-oks-exit) → boolean?

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