Path: utzoo!mnetor!uunet!husc6!bu-cs!bucsb!jbw
From: jbw@bucsb.UUCP (Joe Wells)
Newsgroups: comp.emacs
Subject: Re: Changing major mode in server mode
Message-ID: <1519@bucsb.UUCP>
Date: 19 Mar 88 03:31:45 GMT
References: <480@sol.warwick.ac.uk>
Reply-To: jbw@bucsb.bu.edu (Joe Wells)
Followup-To: comp.emacs
Organization: Boston Univ Comp. Sci.
Lines: 57
Keywords: GNU emacs kill-all-local-variables major-modes
Summary: kill-all-local-variables sucks

In article <480@sol.warwick.ac.uk> cudcv@cu.warwick.ac.uk (Rob McMahon) writes:
>The second problem is if I change major mode in the buffer created in
>the server emacs, it calls kill-all-local-variables, which includes
>server-buffer-clients, which means C-x# doesn't work any more.
>
>Is there any way round this ?  Can I protect server-buffer-clients for a
>while, or can I 'push' a mode and then exit it leaving all my variables
>the way they were before ?  Or do I have to write my own alternatives to
>c-mode and text-mode (and tex-mode, and ...) that don't call
>kill-all-local-variables ?
>
>UUCP:   ...!mcvax!ukc!warwick!cudcv	PHONE:  +44 203 523037
>JANET:  cudcv@uk.ac.warwick.cu          ARPA:   cudcv@cu.warwick.ac.uk
>Rob McMahon, Computing Services, Warwick University, Coventry CV4 7AL, England

I have run into this same problem in the past.  My solution was to
rewrite kill-all-local-variables so that it left my variables alone.
This is not straightforward, since there is no function to kill a
single local variable.  kill-all-local-variables is one of the C
functions, so my function had to use the original
kill-all-local-variables, and then restore the variables that I wanted
to keep.  My version of kill-all-local-variables follows.

----
Joe Wells can be reached at:
UUCP:  ..!harvard!bu-cs!bucsb!jbw    _   /|
ARPANET: jbw@bucsb.bu.edu            \`o_O'
CSNET: jbw%bucsb@bu-cs                 ( )   "Ack! Phft!"
BITNET:  clxj9lc@bostonu                U

;;; save the original kill-all-local-variables
;;; must check if we have already changed it
(if (not (fboundp 'old-kill-all-local-variables))
    (fset 'old-kill-all-local-variables
	  (symbol-function 'kill-all-local-variables)))

(defun kill-all-local-variables ()
  "Eliminate all the buffer-local variable values of the current buffer.
This buffer will then see the default values of all variables.

NOTE: This function has been modified to ignore buffer-local variables
which match the regexp in save-local-variables."
  (let ((oldvars (buffer-local-variables)))
    (old-kill-all-local-variables)
    (while oldvars
      (let* ((elem (car oldvars))
	     (var (car elem))
	     (value (cdr elem)))
	(cond ((string-match save-local-variables (symbol-name var))
	       (make-local-variable var)
	       (set var value))))
      (setq oldvars (cdr oldvars)))))

(defvar save-local-variables ""
  "This is a regexp which is used each time kill-local-variables is
called to determine which variables not to kill.  The variable name is
matched against the regexp.")