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Emacs: linum extension to highlight the current line number.
;; Copyright (C) 2014 Emanuele Tomasi <targzeta@gmail.com>
;; This program is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;;
;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;;
;; You should have received a copy of the GNU General Public License
;; along with this program. If not, see <http://www.gnu.org/licenses/>.
;; This file is NOT part of GNU Emacs.
;; Author: Emanuele Tomasi <targzeta@gmail.com>
;; Version: 0.1
;; Maintainer: Emanuele Tomasi <targzeta@gmail.com>
;; Keywords: convenience
;;; Commentary:
;; A function for the `linum-format' variable to highlight the current line
;; number with a custom face.
;;; Changelog:
;; 2015/08/25
;; bugfix: too slow. linum-highlight-current-line is called for every line to
;; display, linum-update on the other way is called only on update. So
;; we moved all the expansive operations to the latter function.
(require 'linum)
(defvar linum-current-line 1 "Current line number.")
(defvar linum-border-width 1 "Border width for linum.")
(defface linum-current-line
`((t :inherit linum
:foreground "goldenrod"
:weight bold
))
"Face for displaying the current line number."
:group 'linum)
(defadvice linum-update (before advice-linum-update activate)
"Set the current line."
(setq linum-current-line (line-number-at-pos)
;; It's the same algorithm that linum dynamic. I only had added one
;; space in front of the first digit.
linum-border-width (number-to-string
(+ 1 (length
(number-to-string
(count-lines (point-min) (point-max))))))))
(defun linum-highlight-current-line (line-number)
"Highlight the current line number using `linum-current-line' face."
(let ((face (if (= line-number linum-current-line)
'linum-current-line
'linum)))
(propertize (format (concat "%" linum-border-width "d") line-number)
'face face)))
(setq linum-format 'linum-highlight-current-line)

sshaw commented Oct 18, 2015

👍

There's also hlinum-mode.

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