flyspelling at undesirable/unneeded moments

[Sébastien Vauban]

Hello,

I've turned on (the great) `flyspell' in many major editing
modes with the following code:

--8<---------------cut here---------------start------------->8---
;; turn on `flyspell' for various major modes
(mapc (lambda (hook)
        (add-hook hook 'my-turn-on-flyspell-french))
      '(message-mode-hook
        text-mode-hook
        latex-mode-hook
        tex-mode-hook
        nuweb-mode-hook
        html-mode-hook)))
--8<---------------cut here---------------end--------------->8---

The problem is that, even in its fastest mode ...

--8<---------------cut here---------------start------------->8---
;; extra switches to pass to the `aspell' program
(setq ispell-extra-args '("--sug-mode=ultra"))
--8<---------------cut here---------------end--------------->8---

... it takes some amount of time - what's annoying for looooong
documents.

It is much more annoying when, in fact, the only thing you want
to do is to `ediff' it, just before committing it into
subversion: while you have worked on it, the fact it re-opens it
makes it go through it (for checking the ortograph) once more!

#1. How could we avoid that (i.e., not being called when open by
    ediff)?

More generally, it'd be normal to activate the minor mode only
once you begin editing the document, not when you're opening it
just for reading.

#2. Is it possible to hook it in such a way (that it's only
    enabled at the time we begin modifying the document)?  Does
    such hook concept exist?

Thank you very much for your helpful answers,
  Seb

-- 
Sébastien Vauban