emacs/lisp/international/kinsoku.el

;;; kinsoku.el --- `Kinsoku' processing funcs  -*- lexical-binding: t; -*-

;; Copyright (C) 1997, 2001-2024 Free Software Foundation, Inc.
;; Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
;;   2005, 2006, 2007, 2008, 2009, 2010, 2011
;;   National Institute of Advanced Industrial Science and Technology (AIST)
;;   Registration Number H14PRO021

;; Keywords: mule, kinsoku

;; This file is part of GNU Emacs.

;; GNU Emacs 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.

;; GNU Emacs 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 GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;; `Kinsoku' processing is to prohibit specific characters to be
;; placed at beginning of line or at end of line.  Characters not to
;; be placed at beginning and end of line have character category `>'
;; and `<' respectively.   This restriction is dissolved by making a
;; line longer or shorter.
;;
;; `Kinsoku' is a Japanese word which originally means ordering to
;; stay in one place, and is used for the text processing described
;; above in the context of text formatting.

;;; Code:

(defvar kinsoku-limit 4
  "How many more columns we can make lines longer by `kinsoku' processing.
The value 0 means there's no limitation.")

;; Setting character category `>' for characters which should not be
;; placed at beginning of line.
(let* ((kinsoku-bol
	(concat
	 ;; ASCII
	 "!)-_~}]:;',.?"
	 ;; Latin JISX0201
	 ;; Instead of putting Latin JISX0201 string directly, we
	 ;; generate the string as below to avoid character
	 ;; unification problem.
	 (let* ((str1 "!)-_~}]:;',.?")
		(len (length str1))
		(idx 0)
		(str2 "")
		ch)
	   (while (< idx len)
	     (setq ch (make-char 'latin-jisx0201 (aref str1 idx))
		   str2 (concat str2 (char-to-string ch))
		   idx (1+ idx)))
	   str2)
	 ;; Katakana JISX0201
	 "｡｣ｧｨｩｪｫｬｭｮｯｰﾞﾟ"
	 ;; Japanese JISX0208
	 "、。，．・：；？！゛゜´｀¨＾￣＿ヽヾゝゞ〃仝々〆〇ー—‐\
／＼〜‖｜…‥’”）〕］｝〉》」』】°′″℃\
ぁぃぅぇぉっゃゅょゎァィゥェォッャュョヮヵヶ"
	 ;; Chinese GB2312
	 "、。．，・ˉˇ¨〃々―～‖…’”）〕〉》」』〗\
】；：？！±×÷∶°′″℃／＼＂＿￣｜ㄥ"
	 ;; Chinese BIG5
	 "，、。．‧；：？！︰…‥﹐﹑﹒·﹔\
﹕﹖﹗｜–︱—︳╴︴﹏）︶｝︸〕︺】\
︼》︾〉﹀」﹂』﹄﹚﹜﹞’”〞′〃\
¯￣＿ˍ﹉﹊﹍﹎﹋﹌×÷±℃℉﹩°ㄥ"))
       (len (length kinsoku-bol))
       (idx 0)
       ch)
  (while (< idx len)
    (setq ch (aref kinsoku-bol idx)
	  idx (1+ idx))
    (modify-category-entry ch ?>)))

;; Setting character category `<' for characters which should not be
;; placed at end of line.
(let* ((kinsoku-eol
	(concat
	 ;; ASCII
	 "({[`"
	 ;; Latin JISX0201
	 ;; See the comment above.
	 (let* ((str1 "({[`")
		(len (length str1))
		(idx 0)
		(str2 "")
		ch)
	   (while (< idx len)
	     (setq ch (make-char 'latin-jisx0201 (aref str1 idx))
		   str2 (concat str2 (char-to-string ch))
		   idx (1+ idx)))
	   str2)
	 ;; JISX0201 Katakana
	 "｢"
	 ;; Japanese JISX0208
	 "‘“（〔［｛〈《「『【°′″℃＠§"
	 ;; Chinese GB2312
         "‘“＂（〔〈《「『〖【°′″＠℃§\
ㄅㄆㄇㄈㄉㄊㄋㄌㄍㄎㄏㄐㄑㄒㄓㄔㄕㄖㄗㄘㄙㄨ\
\（︵｛︷〔︹【︻《︽〈︿「﹁『﹃﹙﹛﹝"
	 ;; Chinese BIG5
	 "‘“〝‵′〃§＠℃℉﹫°ㄅㄆㄇㄈㄉㄊㄋ\
ㄌㄍㄎㄏㄐㄑㄒㄓㄔㄕㄖㄗㄘㄙㄨ"))
       (len (length kinsoku-eol))
       (idx 0)
       ch)
  (while (< idx len)
    (setq ch (aref kinsoku-eol idx)
	  idx (1+ idx))
    (modify-category-entry ch ?<)))

;; Try to resolve `kinsoku' restriction by making the current line longer.
(defun kinsoku-longer ()
  (let ((pos-and-column
	 (save-excursion
	   (forward-char 1)
	   (while (and (not (eolp))
		       (or (aref (char-category-set (following-char)) ?>)
			   ;; protect non-kinsoku words
			   (not (or (eq (preceding-char) ? )
				    (aref (char-category-set (preceding-char))
					  ?|)))))
	     (forward-char 1))
	   (cons (point) (current-column)))))
    (if (or (<= kinsoku-limit 0)
	    (< (cdr pos-and-column) (+ (current-fill-column) kinsoku-limit)))
	(goto-char (car pos-and-column)))))

;; Try to resolve `kinsoku' restriction by making the current line shorter.
;; The line can't be broken before the buffer position LINEBEG.
(defun kinsoku-shorter (linebeg)
  (let ((pos (save-excursion
	       (forward-char -1)
	       (while (and
		       (< linebeg (point))
		       (or (aref (char-category-set (preceding-char)) ?<)
			   (aref (char-category-set (following-char)) ?>)
			   ;; protect non-kinsoku words
			   (not (or (eq (preceding-char) ? )
				    (aref (char-category-set (preceding-char))
					  ?|)))))
		 (forward-char -1))
	       (point))))
    (if (< linebeg pos)
	(goto-char pos))))

;;;###autoload
(defun kinsoku (linebeg)
  "Go to a line breaking position near point by doing `kinsoku' processing.
LINEBEG is a buffer position we can't break a line before.

`Kinsoku' processing is to prohibit specific characters to be placed
at beginning of line or at end of line.  Characters not to be placed
at beginning and end of line have character category `>' and `<'
respectively.  This restriction is dissolved by making a line longer or
shorter.

`Kinsoku' is a Japanese word which originally means ordering to stay
in one place, and is used for the text processing described above in
the context of text formatting."
  (if enable-kinsoku
      (if (or (and
	       ;; The character after point can't be placed at beginning
	       ;; of line.
	       (aref (char-category-set (following-char)) ?>)
	       ;; We at first try to dissolve this situation by making a
	       ;; line longer.  If it fails, then try making a line
	       ;; shorter.
	       (not (kinsoku-longer)))
	      ;; The character before point can't be placed at end of line.
	      (aref (char-category-set (preceding-char)) ?<))
	  (kinsoku-shorter linebeg))))

(provide 'kinsoku)

;;; kinsoku.el ends here