GNU bug report logs - #5042
23.1; linum-mode gives incorrect line numbers with narrowed buffers

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Message #20 received at 5042 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Juanma Barranquero <lekktu <at> gmail.com>
To: mark.lillibridge <at> hp.com
Cc: 5042 <at> debbugs.gnu.org
Subject: Re: bug#5042: 23.1; linum-mode gives incorrect line numbers with 
	narrowed buffers
Date: Thu, 10 Dec 2009 12:41:21 +0100

On Thu, Dec 10, 2009 at 06:34, Mark Lillibridge <mark.lillibridge <at> hp.com> wrote:

>    The entire point of having line numbers is that they correspond to
> something useful. Either an external program's line number (e.g., a gcc
> error number) or an internal Emacs notion such as that provided by
> goto-line.  The current behavior does neither.

Well, there are many definitions of useful. I find the current
behavior useful, because my main use of linum is knowing at a glance
how many lines there are in the file (or in the region, if narrowing
is in effect).

>    Note that other line numbering modes like wb-line-number implement
> the behavior that I describe as correct.

Yes. But linum allows you to use line numbers in a quite more flexible
way. You could do

(defvar num-of-lines nil)
(defvar num-format nil)
(make-variable-buffer-local 'num-of-lines)
(make-variable-buffer-local 'num-format)

(add-hook 'linum-before-numbering-hook
          (lambda ()
            (save-restriction
              (widen)
              (let ((lines (count-lines (point-min) (point-max))))
                (setq num-format (format "%%%dd" (length
(int-to-string lines))))
                (setq num-of-lines (1+ lines))))))

(setq linum-format
      (lambda (line)
        (format num-format (- num-of-lines line))))

if you fancied numbering lines in reverse, for example.

    Juanma

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