;;; tabify.el --- tab conversion commands for Emacs
-;; Copyright (C) 1985, 1994 Free Software Foundation, Inc.
+;; Copyright (C) 1985, 1994, 2001-2016 Free Software Foundation, Inc.
-;; Maintainer: FSF
+;; Maintainer: emacs-devel@gnu.org
+;; Package: emacs
;; This file is part of GNU Emacs.
-;; GNU Emacs is free software; you can redistribute it and/or modify
+;; 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 2, or (at your option)
-;; any later version.
+;; 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
;; 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, 675 Mass Ave, Cambridge, MA 02139, USA.
+;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
;;; Commentary:
;;; Code:
;;;###autoload
-(defun untabify (start end)
+(defun untabify (start end &optional _arg)
"Convert all tabs in region to multiple spaces, preserving columns.
+If called interactively with prefix ARG, convert for the entire
+buffer.
+
Called non-interactively, the region is specified by arguments
START and END, rather than by the position of point and mark.
The variable `tab-width' controls the spacing of tab stops."
- (interactive "r")
- (save-excursion
- (save-restriction
- (narrow-to-region (point-min) end)
- (goto-char start)
- (while (search-forward "\t" nil t) ; faster than re-search
- (let ((tab-beg (point))
- (column (current-column))
- (indent-tabs-mode nil))
- (skip-chars-backward "\t" start)
- (delete-region tab-beg (point))
- (indent-to column))))))
+ (interactive (if current-prefix-arg
+ (list (point-min) (point-max) current-prefix-arg)
+ (list (region-beginning) (region-end) nil)))
+ (let ((c (current-column)))
+ (save-excursion
+ (save-restriction
+ (narrow-to-region (point-min) end)
+ (goto-char start)
+ (while (search-forward "\t" nil t) ; faster than re-search
+ (forward-char -1)
+ (let ((tab-beg (point))
+ (indent-tabs-mode nil)
+ column)
+ (skip-chars-forward "\t")
+ (setq column (current-column))
+ (delete-region tab-beg (point))
+ (indent-to column)))))
+ (move-to-column c)))
+
+(defvar tabify-regexp " [ \t]+"
+ "Regexp matching whitespace that tabify should consider.
+Usually this will be \" [ \\t]+\" to match a space followed by whitespace.
+\"^\\t* [ \\t]+\" is also useful, for tabifying only initial whitespace.")
;;;###autoload
-(defun tabify (start end)
+(defun tabify (start end &optional _arg)
"Convert multiple spaces in region to tabs when possible.
A group of spaces is partially replaced by tabs
when this can be done without changing the column they end at.
+If called interactively with prefix ARG, convert for the entire
+buffer.
+
Called non-interactively, the region is specified by arguments
START and END, rather than by the position of point and mark.
The variable `tab-width' controls the spacing of tab stops."
- (interactive "r")
+ (interactive (if current-prefix-arg
+ (list (point-min) (point-max) current-prefix-arg)
+ (list (region-beginning) (region-end) nil)))
(save-excursion
(save-restriction
- (narrow-to-region start end)
+ ;; Include the beginning of the line in the narrowing
+ ;; since otherwise it will throw off current-column.
+ (goto-char start)
+ (beginning-of-line)
+ (narrow-to-region (point) end)
(goto-char start)
- (while (re-search-forward "[ \t][ \t][ \t]*" nil t)
- (let ((column (current-column))
- (indent-tabs-mode t))
- (delete-region (match-beginning 0) (point))
- (indent-to column))))))
+ (let ((indent-tabs-mode t))
+ (while (re-search-forward tabify-regexp nil t)
+ ;; The region between (match-beginning 0) and (match-end 0) is just
+ ;; spacing which we want to adjust to use TABs where possible.
+ (let ((end-col (current-column))
+ (beg-col (save-excursion (goto-char (match-beginning 0))
+ (skip-chars-forward "\t")
+ (current-column))))
+ (if (= (/ end-col tab-width) (/ beg-col tab-width))
+ ;; The spacing (after some leading TABs which we wouldn't
+ ;; want to touch anyway) does not straddle a TAB boundary,
+ ;; so it neither contains a TAB, nor will we be able to use
+ ;; a TAB here anyway: there's nothing to do.
+ nil
+ (delete-region (match-beginning 0) (point))
+ (indent-to end-col))))))))
(provide 'tabify)