(hexl-mode): Fix typo in docstring.

[gnu-emacs] / lisp / tabify.el

diff --git a/lisp/tabify.el b/lisp/tabify.el
index c5d76fcc2110496a54a112010648fdb577f845c7..de37f281eda051d7f3282055a408d46bca0f7d11 100644 (file)
--- a/lisp/tabify.el
+++ b/lisp/tabify.el
@@ -1,6 +1,7 @@
 ;;; tabify.el --- tab conversion commands for Emacs
 
-;; Copyright (C) 1985, 1994 Free Software Foundation, Inc.
+;; Copyright (C) 1985, 1994, 2002, 2003, 2004,
+;;   2005, 2006 Free Software Foundation, Inc.
 
 ;; Maintainer: FSF
 
@@ -18,8 +19,8 @@
 
 ;; 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.
+;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+;; Boston, MA 02110-1301, USA.
 
 ;;; Commentary:
 
@@ -40,13 +41,20 @@ The variable `tab-width' controls the spacing of tab stops."
       (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))
-             (column (current-column))
-             (indent-tabs-mode nil))
-         (skip-chars-backward "\t" start)
+             (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 two or more spaces or tabs.
+\"^\\t* [ \\t]+\" is also useful, for tabifying only initial whitespace.")
+
 ;;;###autoload
 (defun tabify (start end)
   "Convert multiple spaces in region to tabs when possible.
@@ -64,12 +72,24 @@ The variable `tab-width' controls the spacing of tab stops."
       (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)
 
+;; arch-tag: c83893b1-e0cc-4e57-8a09-73fd03466416
 ;;; tabify.el ends here