The generic function
updates the state of an interface, such as enabling and disabling menus, buttons, and so forth, that might have changed since the last call. When using this as a callback, you can use
instead of the symbol, and then it will get passed the correct arguments regardless of the callback type.
Note: This method is called by popup-confirmer to update its button's enabled state, and so it should be called when state changes in a dialog.