relative line number

extensions/linum-relativenumber.el

@@ -0,0 +1,22 @@
+(defvar my-linum-format-string "%3d")
+(add-hook 'linum-before-numbering-hook 'my-linum-get-format-string)
+(defun my-linum-get-format-string ()
+  (let* ((width (1+ (length (number-to-string
+                             (count-lines (point-min) (point-max))))))
+         (format (concat "%" (number-to-string width) "d")))
+    (setq my-linum-format-string format)))
+
+(defvar my-linum-current-line-number 0)
+
+(setq linum-format 'my-linum-relative-line-numbers)
+
+(defun my-linum-relative-line-numbers (line-number)
+  (let ((offset (- line-number my-linum-current-line-number)))
+    (propertize (format my-linum-format-string offset) 'face 'linum)))
+
+(defadvice linum-update (around my-linum-update)
+  (let ((my-linum-current-line-number (line-number-at-pos)))
+    ad-do-it))
+(ad-activate 'linum-update)
+(custom-set-faces
+ '(linum ((t (:inherit (shadow) :height 0.8)))))

pre/editing.el

@@ -10,4 +10,5 @@
 ;; highlight current line
 (global-hl-line-mode t)
 (set-face-background 'hl-line "#073642")
-
+;; relative line number
+(load-file (concat user-extensions-directory "linum-relativenumber.el"))