[tab][tab][tab]foo_function (arg1,
[tab][tab][tab]              arg2,
[tab][tab][tab]              arg3)

Unfortunately, if you use the default C indentation mode in emacs, what you get (when breaking like with C-j or RET TAB) is the following:

[tab][tab][tab]foo_function (arg1,
[tab][tab][tab][tab][tab]    arg2,
[tab][tab][tab][tab][tab]    arg3)

So you mean to tweak the code yourself to fix the tabs. Tedious, annoying. We know better!

I wrote a hook to fix this. The idea is to fix tabs when we’re in an argument list context. It can probably be further improved (please send patches!), but it’s quite useful already.

Just add the following to your .emacs file.

[code lang="lisp"]
(defun xmms2-c-mode ()
"C mode with adjusted defaults for use with the xmms2."
(interactive)
(c-mode)
(c-set-style "K&R")
(setq tab-width 4)
(setq indent-tabs-mode t)
(setq c-basic-offset 4)

; Align closing paren with opening paren
(c-set-offset 'arglist-close 'c-lineup-arglist-intro-after-paren)

(add-hook 'c-special-indent-hook 'smart-tab-indent-hook))

(defun get-nonempty-context ()
(let ((curr-context (car (c-guess-basic-syntax))))
(if (or (eq (car curr-context) 'arglist-intro)
(eq (car curr-context) 'arglist-cont)
(eq (car curr-context) 'arglist-cont-nonempty)
(eq (car curr-context) 'arglist-close))
curr-context
nil)))

(defun smart-tab-indent-hook ()
"Fixes indentation to pad with spaces in arglists."
(let ((nonempty-ctx (get-nonempty-context)))
(if nonempty-ctx
(let ((tabbed-columns (+ (point-at-bol)
(/ (c-langelem-col nonempty-ctx t)
tab-width)))
(orig-column (current-column)))
(tabify (point-at-bol) tabbed-columns)
(untabify tabbed-columns (point-at-eol))
; editing tabs screws the pointer position
(move-to-column orig-column)))))
[/code]

Note: don’t forget the c-set-offset bit, else it won’t work properly for the last argument before the closing parenthesis. And avoid using c-indent-new-comment-line to break lines, it can fail with this hook; use c-context-line-break instead, it’s smarter anyway!