Re: Feature request: permanent-local values in hooks buffer local values

[Lennart Borgman (gmail)]

Richard Stallman wrote:
>     For buffer local values of hooks you can perhaps use that, but it 
>     probably does not do what you want. Some functions in a hook should 
>     survive changing major mode (for the same reasons that variables should 
>     do it), but other should not.
>
>     Could somehow a feature be added to hooks that fulfills the need I have 
>     sketched above?
>
> Isn't change-major-mode-hook sufficient to take care of this need?

Perhaps you meant after-change-major-mode-hook? Yes, minor modes can add 
them selves to after-change-major-mode-hook to re-add their buffer local 
hook functions if that fits.

Perhaps that is better. It could look something like below where I have 
used flymake as an example. (flymake-mode is a minor mode that is buffer 
local, but that does not really care about major mode. It depends on the 
buffer file name instead.):

  (put 'flymake-mode 'permanent-local t)

  (defun flymake-add-to-local-hooks ()
    (when flymake-mode
      (add-hook 'after-change-functions 'flymake-after-change-function
                 nil t)
      (add-hook 'after-save-hook 'flymake-after-save-hook nil t)
      (add-hook 'kill-buffer-hook 'flymake-kill-buffer-hook nil t)))

  (add-hook 'after-change-major-mode-hook 'flymake-add-to-local-hooks)

What disturbs me about a solution like this is that the global value of 
after-change-major-mode-hook must be used. (Am I missing something 
there?) It does not mean any performance penalty, of course. It just 
that it feels a bit strange.

Is this the way to go for such minor modes as flymake-mode? I think we 
need some guidelines here for minor mode authors.

The reason I am asking this is mainly because it has to be solved in 
some way for mumamo-mode. (For those who do not know about it see 
http://www.emacswiki.org/cgi-bin/wiki/MuMaMo )