Taming Emacs' text mode wrapping and indenting (Shallow Thoughts)

Akkana's Musings on Open Source Computing and Technology, Science, and Nature.

Wed, 13 Jan 2010

Taming Emacs' text mode wrapping and indenting

To wrap long lines, or not to wrap? It's always a dilemma. Automatic wrapping is great when you're hammering away typing lots of text. But it's infuriating when you're trying to format something yourself and the editor decides it wants to line-wrap a little too early.

Although of course you can set the wrapping width, Emacs has a tendency to wrap early -- especially when you hit return. All too often, I'll be typing away at a long line, get to the end of the sentence and paragraph with the last word on the same line with the rest -- then realize that as soon as I hit return, Emacs is going to move that last word to a line by itself. Drives me nuts!

And the solution turns out to be so simple. The Return key, "\C-m". was bound to the (newline) function (you can find out by typing M-x, then describe-key, then hitting Return). Apparently (newline) re-wraps the current line before inserting a line break. But I just wanted it to insert a line break.

No problem -- just bind "C-m" to (insert "\n").

But there's a second way, too, if you don't want to rebind: there's a magic internal emacs table you can change.

(set-char-table-range auto-fill-chars 10 nil)

But wait -- there's one other thing I want to fix in text mode.

Automatic indent is another one of those features that's very convenient ... except when it's not.

If I have some text like:

First point:
  - subpoint a
  - subpoint b
then it's handy if, when I hit Return after subpoint a, emacs indents to the right level for subpoint b. But what happens when I get to the end of that list?
First point:
  - subpoint a
  - subpoint b

Second point:
  - subpoint c

When I hit Return after subpoint b, Emacs quite reasonably indents two spaces. If I immediately type another Return, Emacs sensibly deletes the two spaces it just inserted, opens a new line -- but then it indents that new line another two spaces.

After a blank line, I always want to start at the beginning, not indented at all.

Here's how to fix that. Define a function that will be called whenever you hit return in text mode. That function tests whether the caret comes immediately after a blank line, or at the beginning of the file. It indents except in those two cases; and in neither case does it re-wrap the current line.

;; In text mode, I don't want it auto-indenting for the first
;; line in the file, or lines following blank lines.
;; Everywhere else is okay.
(defun newline-and-text-indent ()
  "Insert a newline, then indent the next line sensibly for text"
   ;; Beginning of buffer, or beginning of an existing line, don't indent:
   ((or (bobp) (bolp)) (newline))

   ;; If we're on a whitespace-only line,
   ((and (eolp)
         (save-excursion (re-search-backward "^\\(\\s \\)*$"
                                             (line-beginning-position) t)))
    ;; ... delete the whitespace, then add another newline:
    (kill-line 0)

   ;; Else (not on whitespace-only) insert a newline,
   ;; then add the appropriate indent:
   (t (insert "\n")

Then tell emacs to call that function when it sees the Return key in text mode:

(defun text-indent-hook ()
  (local-set-key "\C-m" 'newline-and-text-indent)
(setq text-mode-hook 'text-indent-hook)

Finally, this is great for HTML mode too, if you get irritated at not being able to put an <a href="longurl"> all on one line:

(defun html-hook ()
  (local-set-key "\C-m" (lambda () (interactive) (insert "\n")))
(setq sgml-mode-hook 'html-hook)

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[ 11:29 Jan 13, 2010    More linux/editors | permalink to this entry | comments ]
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