highlight-80+.el

;;; highlight-80+.el --- highlight characters beyond column 80

;;

;; Copyright (C) 2008 Nikolaj Schumacher

;;

;; Author: Nikolaj Schumacher

;; Version: 1.0

;; Keywords: faces

;; URL: http://nschum.de/src/emacs/highlight-tabs/

;; Compatibility: GNU Emacs 22.x

;;

;; This file is NOT part of GNU Emacs.

;;

;; 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 2

;; 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 .

;;

;;; Commentary:

;;

;; This mode highlights all characters that cross the 80 character line limit.

;;

;;; Change Log:

;;

;; 2008-08-11 (1.0)

;; Initial release.

;;

;;; Code:

;;Add the following to your .emacs:

;; (add-to-list 'load-path "~/.emacs.d")

;; (require 'highlight-80+)

;;(add-hook 'f90-mode-hook 'highlight-80+-mode)

(defgroup highlight-80+ nil

"Highlight characters beyond column 80."

:group 'faces)

(defcustom highlight-80+-columns 132 ;;132 is the number for .f90

"*Number of columns to allow in lines."

:group 'highlight-80+

:type 'integer)

(defface highlight-80+-line

nil

"*Face for showing lines with over `highlight-80+-columns'."

:group 'highlight-80+-line)

(defface highlight-80+

'((((background dark)) (:background "blue"))

(((background light)) (:background "dark gray")))

"*Face for showing characters beyond column `highlight-80+-columns'."

:group 'highlight-80+-line)

(defface highlight-80+-first

nil

"*Face for showing the first character beyond `highlight-80+-columns'."

:group 'highlight-80+-line)

(defconst highlight-80+-keywords

`((highlight-80+-matcher (0 'highlight-80+-line prepend)

(1 'highlight-80+ prepend)

(2 'highlight-80+-first prepend))))

(defsubst highlight-80+-format ()

(if (<>

"^\\(\\)\\([^\n]\\)\\{80,\\}$"

(concat (format "^\\(?:[^\t\n]\\{%d\\}\\|[^\t\n]\\{,%d\\}\t\\)\\{%d\\}"

tab-width (- tab-width 1)

(/ highlight-80+-columns tab-width))

(let ((remainder (mod highlight-80+-columns tab-width)))

(when remainder

(format "\\(?:[^\t\n]\\{%d\\}\\|\t\\)" remainder)))

"\\(\\(.\\).*\\)$")))

(defvar highlight-80+-last-width 0)

(make-variable-buffer-local 'highlight-80+-last-width)

(defvar highlight-80+-last-keywords "")

(make-variable-buffer-local 'highlight-80+-last-keywords)

(defun highlight-80+-matcher (limit)

;; Update search when `tab-width' has changed.

(unless (equal highlight-80+-last-width tab-width)

(setq highlight-80+-last-keywords (highlight-80+-format)

highlight-80+-last-width tab-width)

;; The rest of the buffer can't be right, either.

(let ((font-lock-keywords))

(font-lock-fontify-buffer)))

;; re-search-forward is C and much faster checking columns ourselves

(re-search-forward highlight-80+-last-keywords nil t))

;;;###autoload

(define-minor-mode highlight-80+-mode

"Highlight the portions of lines longer than 80 characters."

nil " 80+" nil

(if highlight-80+-mode

(font-lock-add-keywords nil highlight-80+-keywords t)

(font-lock-remove-keywords nil highlight-80+-keywords)

(kill-local-variable 'highlight-80+-last-keywords)

(kill-local-variable 'highlight-80+-last-width))

(font-lock-fontify-buffer))

(provide 'highlight-80+)

;;; highlight-80+.el ends here