Emacs smart tabs - indent with tabs, align with spaces!

smarttabs.el

;; 
;; Emacs smart tabs functionality
;;   Intelligently indent with tabs, align with spaces!
;; 
;; Note: Indenting only uses tabs when indent-tabs-mode is non-nil,
;; otherwise it uses spaces as usual.
;; 
;; To use: save as smarttabs.el in your .emacs.d directory, and add
;; "(require 'smarttabs)" to your .emacs file.
;; 
;; Code is GPLv2, derived from http://www.emacswiki.org/emacs/SmartTabs
;; 
;; Modifications by John Croisant:
;;  * Remembers and re-applies window start, so that indenting doesn't
;;    cause the window to visibly scroll. (2009-09-18)
;; 


(defadvice align (around smart-tabs activate)
  (let ((indent-tabs-mode nil)) ad-do-it))

(defadvice align-regexp (around smart-tabs activate)
  (let ((indent-tabs-mode nil)) ad-do-it))

(defadvice indent-relative (around smart-tabs activate)
  (let ((indent-tabs-mode nil)) ad-do-it))

(defadvice indent-according-to-mode (around smart-tabs activate)
  (let ((indent-tabs-mode indent-tabs-mode))
    (if (memq indent-line-function
              '(indent-relative
                indent-relative-maybe))
        (setq indent-tabs-mode nil))
    ad-do-it))

(defmacro smart-tabs-advice (function offset)
  `(progn
     (defvaralias ',offset 'tab-width)
     (defadvice ,function (around smart-tabs activate)
       (cond
        (indent-tabs-mode
         (save-excursion
           (beginning-of-line)
           (while (looking-at "\t*\\( +\\)\t+")
             (replace-match "" nil nil nil 1)))
         (setq tab-width tab-width)
         (let ((tab-width fill-column)
               (,offset fill-column)
               (wstart (window-start)))
           (unwind-protect
               (progn ad-do-it)
             (set-window-start (selected-window) wstart))))
        (t
         ad-do-it)))))

(smart-tabs-advice c-indent-line c-basic-offset)
(smart-tabs-advice c-indent-region c-basic-offset)


(provide 'smarttabs)