spell-check buffer in background, display buffer only if user interaction is needed

[Ernest Adrogué]

Hello,

Suppose that a function creates a temporary buffer for editing parts a
file and switches to it.  For the purpose of testing, I'm using the
following function instead of the real one

(defun create-test-buffer-and-go (text)
  (pop-to-buffer "*test-buffer*")
  (erase-buffer)
  (insert text)
  (goto-char (point-min)))

I'm trying to write a function that will spell-check the temporary
buffer in the background and will only display the buffer if user
interaction is required, that is, if the buffer contains misspelled
words and the user has to choose among a list of corrections.

One possibility is to use save-window-excursion and add a hook to
ispell-update-post-hook which is run by ispell before creating the
*Choices* buffer.

(defun ispell-test-buffer ()
  (set-buffer "*test-buffer*")
  (add-hook 'ispell-update-post-hook
            (lambda () (pop-to-buffer "*test-buffer*"))
            t t)
  (ispell-buffer))

So, using an English dictionary

(save-window-excursion (create-test-buffer-and-go "hello"))
(ispell-test-buffer)

shouldn't display the buffer at all, but passing the string "helloz"
should, which it does.  The problem is the window is not left open, not
sure why.  In order to fix this the only thing that occurs to me is have
the hook function set a flag, and afterwards display the buffer if the
flag is set

(defun ispell-test-buffer ()
  (let (required-interaction)
    (set-buffer "*test-buffer*")
    (add-hook 'ispell-update-post-hook
              (lambda ()
                (pop-to-buffer "*test-buffer*")
                (setq required-interaction t))
              t t)
    (ispell-buffer)
    (when required-interaction
      (pop-to-buffer "*test-buffer*"))))

but I'm not sure that this approach is right, so I'd like to hear
suggestions if somebody has any.

Cheers.