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longlines.el 2.2.7 -- automatically wrap long lines

From: Chong Yidong
Subject: longlines.el 2.2.7 -- automatically wrap long lines
Date: 07 Feb 2005 23:14:19 -0800
User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.2

Added the autoload cookie, and deal with major mode changes correctly.

;;; longlines.el --- automatically wrap long lines -*- coding: iso-8859-1; -*-

;; Copyright (C) 2000, 2001 by Free Software Foundation, Inc.
;; Copyright (C) 2004 by Chong Yidong.

;; Authors:    Kai Grossjohann <address@hidden>
;;             Alex Schroeder <address@hidden>
;;             Chong Yidong <address@hidden>
;; Maintainer: Chong Yidong <address@hidden>
;; Version: 2.2.7
;; Keywords: convenience

;; This file 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, or (at your option)
;; any later version.

;; This file is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to
;; the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Commentary:

;; Some text editors save text files with long lines, and they
;; automatically break these lines at whitespace, without actually
;; inserting any newline characters. When doing `M-q' in Emacs, you
;; are inserting newline characters. This file provides a file format
;; which wraps the long lines when reading a file and unwraps the
;; lines when saving the file. It can also wrap and unwrap
;; automatically as editing takes place.

;;; Installation:

;; Save longlines.el in a convenient directory, preferably in
;; your `load-path'. Add the following to your `user-init-file':
;;   (autoload 'longlines-mode
;;     "longlines.el"
;;     "Minor mode for automatically wrapping long lines." t)

;;; Todo:

;; Investigate ^M characters showing up in relation to auto-save-file,
;; at least for NTEmacs.

;;; Code:

(require 'easy-mmode)
(when (not (fboundp 'overlays-in)) (require 'overlay)) ; for XEmacs

;; Customization

(defgroup longlines nil
  "Automatic wrapping of long lines when loading files."
  :group 'fill)

(defcustom longlines-auto-wrap t
  "*Non-nil means long lines are automatically wrapped after each command."
  :group 'longlines
  :type 'boolean)

(defcustom longlines-wrap-follows-window-size nil
  "*Non-nil means wrapping and filling happen at the edge of the window.
Otherwise, `fill-column' is used, regardless of the window size. This
does not work well when the buffer is displayed in multiple windows
with different widths."
  :group 'wrap
  :type 'boolean)

(defcustom longlines-show-hard-newlines nil
  "*Non-nil means the location of each hard newline is marked with a symbol."
  :group 'longlines
  :type 'boolean)

(defcustom longlines-show-effect '(before-string . "¶")
  "Determines how hard newlines are made visible."
  :group 'longlines
  :type '(choice
          (const :tag "Pi" (before-string . "¶"))
          (const :tag "Default Face" (face . longlines-visible-face))
          (cons :tag "Custom Face"
                :value (face . longlines-visible-face)
                (const :tag "Property" face) face)
          (cons :tag "Property" 
                :value (face . longlines-visible-face)
                (symbol :tag "Property") (sexp :tag "Value"))))

;; Internal variables

(defvar longlines-wrap-beg nil)
(defvar longlines-wrap-end nil)
(defvar longlines-wrap-point nil)
(defvar longlines-showing nil)

(make-variable-buffer-local 'longlines-wrap-beg)
(make-variable-buffer-local 'longlines-wrap-end)
(make-variable-buffer-local 'longlines-wrap-point)
(make-variable-buffer-local 'longlines-showing)

;; Showing the effect of hard newlines in the buffer

(defface longlines-visible-face
  '((t (:background "red")))
  "Face used to make hard newlines visible in `longlines-mode'.")

(defun longlines-show-hard-newlines (&optional arg)
  "Make hard newlines visible by adding a face.
With optional argument ARG, make the hard newlines invisible again
by calling `longlines-unshow-hard-newlines'."
  (interactive "P")
  (if arg
      (setq longlines-showing t)
      ;; We want to show every single newline.  Therefore every single
      ;; newline must get its own overlay.  No spanning of multiple
      ;; newlines with one overlay.
      (let ((pos (text-property-any (point-min) (point-max) 'hard t)))
        (while pos
          (longlines-show-region pos (1+ pos))
          (setq pos (text-property-any (1+ pos) (point-max) 'hard t)))))))

(defun longlines-show-region (start end)
  "Make region between START and END visible."
  (unless (let ((os (overlays-in start end))
                o exists)
            (while (and os (not exists))
              (setq o (car os)
                    os (cdr os))
              (when (overlay-get o 'longlines)
                (setq exists t)))
    (let ((o (make-overlay start end nil t)))
      (overlay-put o (car longlines-show-effect) (cdr longlines-show-effect))
      (overlay-put o 'longlines t)
      (overlay-put o 'evaporate t))))

(defun longlines-unshow-hard-newlines ()
  "Make hard newlines invisible again."
  (setq longlines-showing nil)
  (let ((os (overlays-in (point-min) (point-max)))
    (while os
      (setq o (car os)
            os (cdr os))
      (when (overlay-get o 'longlines)
        (delete-overlay o)))))

;; Wrapping the paragraphs.

(defun longlines-wrap-region (start end)
  "Wrap each successive line, starting with the line before START.
Stop when we reach lines after END that don't need wrapping, or the
end of the buffer."
  (setq longlines-wrap-point (point))
  (goto-char start)
  (forward-line -1)
  ;; Two successful longlines-wrap-line's in a row mean successive
  ;; lines don't need wrapping.
  (while (null (and (longlines-wrap-line)
                    (or (eobp)
                        (and (>= (point) end)
  (goto-char longlines-wrap-point))

(defun longlines-wrap-line ()
  "If the current line needs to be wrapped, wrap it and return nil.
If wrapping is performed, point remains on the line. If the line does
not need to be wrapped, move point to the next line and return t."
  (if (longlines-set-breakpoint)
      (progn (backward-delete-char 1)
             (insert-char ?\n 1)
    (if (longlines-merge-lines-p)
        (progn (end-of-line)
               (delete-char 1)
     ;; After certain commands (e.g. kill-line), there may be two
     ;; successive soft newlines in the buffer. In this case, we
     ;; replace these two newlines by a single space. Unfortunately,
     ;; this breaks the conservation of (spaces + newlines), so we
     ;; have to fiddle with longlines-wrap-point.
               (if (or (bolp) (eolp))
                   (if (> longlines-wrap-point (point))
                       (setq longlines-wrap-point
                             (1- longlines-wrap-point)))
                 (insert-char ?  1))
      (forward-line 1)

(defun longlines-set-breakpoint ()
  "Place point where we should break the current line, and return t.
If the line should not be broken, return nil; point remains on the
  (move-to-column fill-column)
  (if (and (re-search-forward "[^ ]" (line-end-position) 1)
           (> (current-column) fill-column))
      ;; This line is too long. Can we break it?
      (or (longlines-find-break-backward)
          (progn (move-to-column fill-column)

(defun longlines-find-break-backward ()
  "Move point backward to the first available breakpoint and return t.
If no breakpoint is found, return nil."
  (and (search-backward " " (line-beginning-position) 1)
         (skip-chars-backward " " (line-beginning-position))
         (null (bolp)))
       (progn (forward-char 1)
              (if (and fill-nobreak-predicate
                  (progn (skip-chars-backward " " (line-beginning-position))

(defun longlines-find-break-forward ()
  "Move point forward to the first available breakpoint and return t.
If no break point is found, return nil."
  (and (search-forward " " (line-end-position) 1)
       (progn (skip-chars-forward " " (line-end-position))
              (null (eolp)))
       (if (and fill-nobreak-predicate

(defun longlines-merge-lines-p ()
  "Return t if part of the next line can fit onto the current line.
Otherwise, return nil. Text cannot be moved across hard newlines."
    (and (null (eobp))
         (null (get-text-property (point) 'hard))
         (let ((space (- fill-column (current-column))))
           (forward-line 1)
           (if (eq (char-after) ? )
               t ; We can always merge some spaces
             (<= (if (search-forward " " (line-end-position) 1)
                   (1+ (current-column)))

(defun longlines-decode-region (beg end)
  "Turn all newlines between BEG and END into hard newlines."
  (use-hard-newlines 1 'never)
    (let ((reg-min (min beg end))
          (reg-max (max beg end)))
      (goto-char reg-min)
      (while (search-forward "\n" reg-max t)
        (set-hard-newline-properties (match-beginning 0) (match-end 0))))))

(defun longlines-encode-region (beg end &optional buffer)
  "Replace each soft newline between BEG and END with exactly one space.
Hard newlines are left intact. The optional argument BUFFER exists for
compatibility with `format-alist', and is ignored."
    (let ((reg-min (min beg end))
          (reg-max (max beg end)))
      (goto-char reg-min)
      (while (search-forward "\n" reg-max t)
        (unless (get-text-property (match-beginning 0) 'hard)
          (replace-match " ")))

;; Auto wrap

(defun longlines-auto-wrap (&optional arg)
  "Turn on automatic line wrapping, and wrap the entire buffer.
With optional argument ARG, turn off line wrapping."
  (interactive "P")
  (remove-hook 'after-change-functions 'longlines-after-change-function t)
  (remove-hook 'post-command-hook 'longlines-post-command-function t)
  (if arg
      (progn (setq longlines-auto-wrap nil)
             (message "Auto wrap disabled."))
    (setq longlines-auto-wrap t)
    (add-hook 'after-change-functions
              'longlines-after-change-function nil t)
    (add-hook 'post-command-hook
              'longlines-post-command-function nil t)
    (longlines-wrap-region (point-min) (point-max))
    (message "Auto wrap enabled.")))

(defun longlines-after-change-function (beg end len)
  "Update `longlines-wrap-beg' and `longlines-wrap-end'.
This is called by `after-change-functions' to keep track of the region
that has changed."
  (unless undo-in-progress
    (setq longlines-wrap-beg
          (if longlines-wrap-beg (min longlines-wrap-beg beg) beg))
    (setq longlines-wrap-end
          (if longlines-wrap-end (max longlines-wrap-end end) end))))

(defun longlines-post-command-function ()
  "Perform line wrapping on the parts of the buffer that have changed.
This is called by `post-command-hook' after each command."
  (when longlines-wrap-beg ; there was a change
    (unless (or (eq this-command 'fill-paragraph)
                (eq this-command 'fill-region))
      (longlines-wrap-region longlines-wrap-beg longlines-wrap-end))
    (setq longlines-wrap-beg nil)
    (setq longlines-wrap-end nil)))

(defun longlines-window-change-function ()
  "Re-wrap the buffer if the window width has changed.
This is called by `window-size-change-functions'."
  (when (/= fill-column (- (window-width) window-min-width))
    (setq fill-column (- (window-width) window-min-width))
    (let ((mod (buffer-modified-p)))
      (longlines-wrap-region (point-min) (point-max))
      (set-buffer-modified-p mod))))

;; Advice for editing functions

(defadvice newline (after newline-shows-hard-ones activate)
  "When a hard newline is inserted, it will also be highlighted.
This happens only if `longlines-showing' is non-nil."
    (when (and longlines-showing
               (search-backward "\n" nil t))
      (longlines-show-region (match-beginning 0) (match-end 0)))))

(defadvice kill-region (before longlines-encode-kill activate)
  "If the buffer is in `longlines-mode', remove all soft newlines."
  (when longlines-mode
    (longlines-encode-region beg end)))

(defadvice copy-region-as-kill (around longlines-encode-kill activate)
  "If the buffer is in `longlines-mode', remove all soft newlines."
  (if longlines-mode
      (let ((string (buffer-substring beg end)))
          (insert string)
          (longlines-encode-region (point-min) (point-max))
          (setq beg (point-min))
          (setq end (point-max))

(defadvice yank (after longlines-decode-kill activate)
  "If the buffer is in `longlines-mode', mark all newlines as hard."
  (when longlines-mode
    (longlines-decode-region (point) (mark t))
    (if longlines-showing

(defadvice yank-pop (after longlines-decode-kill activate)
  "If the buffer is in `longlines-mode', mark all newlines as hard."
  (when longlines-mode
    (longlines-decode-region (point) (mark t))
    (if longlines-showing

;; Loading and saving

(add-to-list 'format-alist
             (list 'longlines               ;name
                   "Automatically wrap long lines." ;doc
                   nil                      ;regexp
                   'longlines-decode-region ;decode
                   'longlines-encode-region ;encode
                   t                        ;modify
                   nil))                    ;mode function

;; Mode

(define-minor-mode longlines-mode
  "Toggle Long Lines mode.
In Long Lines mode, long lines will be wrapped if they extend beyond
`fill-column'. The newlines used for line wrapping will not show up
when the file is saved or the text is yanked.

If `longlines-auto-wrap' is non-nil, lines are automatically wrapped
whenever the buffer is changed. You can always call `fill-paragraph'
to fill individual paragraphs.

If `longlines-show-hard-newlines' is non-nil, hard newlines will be
marked by a symbol."
  nil " ll" nil
  (if longlines-mode
      ;; Turn on longlines mode
        (add-to-list 'buffer-file-format 'longlines)
        (when longlines-wrap-follows-window-size
          (set (make-local-variable 'fill-column)
               (- (window-width) window-min-width))
          (add-hook 'window-configuration-change-hook
                    'longlines-window-change-function nil t))
        (let ((mod (buffer-modified-p))
              (buffer-undo-list t))
          ;; Turning off undo is OK since (spaces + newlines) is
          ;; conserved, except for a corner case in
          ;; longlines-wrap-lines that we'll never encounter from here
          ;; (I think).
          (longlines-decode-region (point-min) (point-max))
          (longlines-wrap-region (point-min) (point-max))
          (set-buffer-modified-p mod))
        (add-hook 'change-major-mode-hook 'longlines-mode-off nil t)
        (when (and longlines-show-hard-newlines
                   (not longlines-showing))
        (when longlines-auto-wrap
          (auto-fill-mode 0)
          (add-hook 'after-change-functions
                    'longlines-after-change-function nil t)
          (add-hook 'post-command-hook
                    'longlines-post-command-function nil t)))
    ;; Turn off longlines mode
    (setq buffer-file-format (delete 'longlines buffer-file-format))
    (let ((mod (buffer-modified-p))
          (buffer-undo-list t))
      (longlines-encode-region (point-min) (point-max))
      (set-buffer-modified-p mod))
    (remove-hook 'change-major-mode-hook 'longlines-mode-off t)
    (remove-hook 'after-change-functions 'longlines-after-change-function t)
    (remove-hook 'post-command-hook 'longlines-post-command-function t)
    (remove-hook 'window-configuration-change-hook
                 'longlines-window-change-function t)
    (kill-local-variable 'fill-column)))

(defun longlines-mode-off ()
  "Turn off longlines mode.
This function exists to be called by `change-major-mode-hook' when the
major mode changes."
  (longlines-mode 0))

(provide 'longlines)

;;; longlines.el ends here

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