linum-update-window.el

(defun linum-update-window (win)
  "Update line numbers for the portion visible in window WIN."
  (goto-char (window-start win))
  (let ((line (line-number-at-pos))
        (limit (window-end win t))
        (fmt (cond ((stringp linum-format) linum-format)
                   ((eq linum-format 'dynamic)
                    (let ((w (length (number-to-string
                                      (count-lines (point-min) (point-max))))))
                      (concat "%" (number-to-string w) "d")))))
        (width 0))
    (run-hooks 'linum-before-numbering-hook)
    ;; Create an overlay (or reuse an existing one) for each
    ;; line visible in this window, if necessary.
    (while (and (not (eobp)) (<= (point) limit))
      (let* ((str (if fmt
                      (propertize (format fmt line) 'face 'linum)
                    (funcall linum-format line)))
             (visited (catch 'visited
                        (dolist (o (overlays-in (point) (point)))
                          (when (equal-including-properties
                                 (overlay-get o 'linum-str) str)
                            (unless (memq o linum-overlays)
                              (push o linum-overlays))
                            (setq linum-available (delq o linum-available))
                            (throw 'visited t))))))
        ;; (setq width (max width (length str)))
        (setq width (max width (linum-my-margin-width str)))
        (unless visited
          (let ((ov (if (null linum-available)
                        (make-overlay (point) (point))
                      (move-overlay (pop linum-available) (point) (point)))))
            (push ov linum-overlays)
            (overlay-put ov 'before-string
                         (propertize " " 'display `((margin left-margin) ,str)))
            (overlay-put ov 'linum-str str))))
      ;; Text may contain those nasty intangible properties, but that
      ;; shouldn't prevent us from counting those lines.
      (let ((inhibit-point-motion-hooks t))
        (forward-line))
      (setq line (1+ line)))
    (set-window-margins win width (cdr (window-margins win)))))
(defun linum-my-margin-width (string)
  (let ((width (length string)))
    (if (and (display-graphic-p)
             (or (featurep 'face-remap) (require 'face-remap nil t)))
        (ceiling (* width (expt text-scale-mode-step text-scale-mode-amount)))
      width)))