emacs mode for NetworkManager-style indentation

[Dan Winship <danw gnome org>]

Since Pavel just complained about this in a bug...

Attached is an emacs mode for getting indentation to work the way the
NetworkManager tree (mostly) does it, with tabs for indentation and
spaces for alignment. Put it somewhere in your emacs load path, then
from .emacs do:

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

and then you can use M-x smart-tabs-mode to turn it on/off. Or, for
extra cleverness, add a file called .dir-locals.el to the top level of
your NetworkManager (and network-manager-applet, etc) tree,  containing:

  ((c-mode . ((smart-tabs-mode . t))))

(and then add ".dir-locals.el" to .git/info/exclude). And then you don't
have to think about it again. (Unless you do "git clean -dfx". In
theory, you're supposed to be able to put the .dir-locals.el file in the
directory *above* your checkout, and specify that it's only supposed to
apply to the NetworkManager subdirectory, but that never worked for
me... I think the documentation gets the syntax wrong or something...)

(I originally found this mode on EmacsWiki, but had to hack it up a
bit... IIRC the original only let you enable it per-mode, not
per-buffer? I forget... anyway, there's a link to the upstream in the
source.)

-- Dan

;; Emacs smart tabs mode
;;   Intelligently indent with tabs, align with spaces!
;;
;; To use, save smart-tabs-mode.el to a a directory on your load-path
;; (e.g., ~/.emacs.d/elisp), then add the following to your .emacs file:
;;
;;  (require 'smart-tabs-mode)
;;
;; Then, for each language you want to use smart tabs, set up a hook
;; and advice like so:
;;
;;  (add-hook 'MODE-HOOK 'smart-tabs-mode-enable)
;;  (smart-tabs-advice INDENT-FUNC TAB-WIDTH-VAR)
;;
;; Here are some specific examples for a few popular languages:
;;
;;  ;; C/C++
;;  (add-hook 'c-mode-hook 'smart-tabs-mode-enable)
;;  (smart-tabs-advice c-indent-line c-basic-offset)
;;  (smart-tabs-advice c-indent-region c-basic-offset)
;;
;;  ;; JavaScript
;;  (add-hook 'js2-mode-hook 'smart-tabs-mode-enable)
;;  (smart-tabs-advice js2-indent-line js2-basic-offset)
;;
;;  ;; Perl (cperl-mode)
;;  (add-hook 'cperl-mode-hook 'smart-tabs-mode-enable)
;;  (smart-tabs-advice cperl-indent-line cperl-indent-level)
;;
;;  ;; Python
;;  (add-hook 'python-mode-hook 'smart-tabs-mode-enable)
;;  (smart-tabs-advice python-indent-line-1 python-indent)
;;
;;  ;; Ruby
;;  (add-hook 'ruby-mode-hook 'smart-tabs-mode-enable)
;;  (smart-tabs-advice ruby-indent-line ruby-indent-level)
;;
;;
;; smart-tabs-mode.el is licensed under the GPLv2.
;; It is derived from <http://www.emacswiki.org/emacs/SmartTabs>
;; as modified by John Croisant (jacius), along with Julien Fontanet and
;; Tomita Hiroshi (tomykaira).
;;
;; Modification history is at <https://github.com/jcsalomon/smarttabs>.

(require 'advice)

(defmacro smart-tabs-mode/no-tabs-mode-advice (function)
  `(unless (ad-find-advice ',function 'around 'smart-tabs)
     (defadvice ,function (around smart-tabs activate)
       (if smart-tabs-mode
           (let ((indent-tabs-mode nil)) ad-do-it)
         ad-do-it))))


(define-minor-mode smart-tabs-mode
  "Intelligently indent with tabs, align with spaces!"

  (progn
    (smart-tabs-mode/no-tabs-mode-advice align)
    (smart-tabs-mode/no-tabs-mode-advice align-regexp)
    (smart-tabs-mode/no-tabs-mode-advice indent-relative)

    (unless
        (ad-find-advice 'indent-according-to-mode 'around 'smart-tabs)
      (defadvice indent-according-to-mode (around smart-tabs activate)
        (if smart-tabs-mode
            (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)
          ad-do-it)))
    nil
    ))
(defvar smart-tabs-mode nil)

(defun smart-tabs-mode-enable ()
  "Enable smart-tabs-mode."
  (smart-tabs-mode t))


(defmacro smart-tabs-advice (function offset)
  `(progn
     (defadvice ,function (around smart-tabs activate)
       (cond
        (smart-tabs-mode
         (save-excursion
           (beginning-of-line)
           (while (looking-at "\t*\\( +\\)\t+")
             (replace-match "" nil nil nil 1)))
         (setq tab-width tab-width)
         (let ((indent-tabs-mode t)
               (tab-width fill-column)
               (,offset fill-column))
           (unwind-protect
               (progn ad-do-it))))
        (t
         ad-do-it)))))


(provide 'smart-tabs-mode)