X-Git-Url: https://code.delx.au/gnu-emacs/blobdiff_plain/f9f9507e1d3202408b73b0c32a6e504502a70d5e..b336bfcdf39f1e4d35bff4a7bd01d3b4bca8f516:/lisp/tabify.el

diff --git a/lisp/tabify.el b/lisp/tabify.el
index 492bd48ec7..c8cf877cb9 100644
--- a/lisp/tabify.el
+++ b/lisp/tabify.el
@@ -1,12 +1,16 @@
-;; Tab conversion commands for Emacs
-;; Copyright (C) 1985 Free Software Foundation, Inc.
+;;; tabify.el --- tab conversion commands for Emacs
+
+;; Copyright (C) 1985, 1994, 2001, 2002, 2003, 2004,
+;;   2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
+
+;; Maintainer: FSF
 
 ;; 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 1, 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
@@ -14,40 +18,76 @@
 ;; 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:
 
+;; Commands to optimize spaces to tabs or expand tabs to spaces in a region
+;; (`tabify' and `untabify').  The variable tab-width does the obvious.
+
+;;; Code:
 
 ;;;###autoload
 (defun untabify (start end)
   "Convert all tabs in region to multiple spaces, preserving columns.
-The variable tab-width controls the action."
+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 start end)
+      (narrow-to-region (point-min) end)
       (goto-char start)
       (while (search-forward "\t" nil t)	; faster than re-search
-	(let ((start (point))
-	      (column (current-column))
-	      (indent-tabs-mode nil))
-	  (skip-chars-backward "\t")
-	  (delete-region start (point))
+	(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))))))
 
+(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)
   "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.
-The variable tab-width controls the action."
+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 start end)
+      ;; Include the beginning of the line in the narrowing
+      ;; since otherwise it will throw off current-column.
       (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))))))
+      (beginning-of-line)
+      (narrow-to-region (point) end)
+      (goto-char start)
+      (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)
+
+;; arch-tag: c83893b1-e0cc-4e57-8a09-73fd03466416
+;;; tabify.el ends here