Emacs: Toggle Line Wrap

By Xah Lee. Date: . Last updated: .

Emacs has a command fill-paragraphAlt+q】 that does hard-wrap of current paragraph (it inserts a newline char at every ~70 chars.) Emacs also has fill-region, which acts on a text selection. However, there are some usability problems with these commands. This page discuss the problems and fixes.

One frequently asked question is how to “unfill” — do inverse of fill-paragraph. Technically, this means replacing newline char by space. Emacs does not have a built-in command for this. The typical answer to this question, is to set the cut-width to a huge number (For example, set fill-column to 10001000), then Alt+x fill-paragraph, then set fill-column back to previous value. This is inconvenient.

If you need to reformat several paragraphs, Alt+x fill-region. There is no keyboard shortcut.

Auto Toggle Fill / Unfill / Region

In the following, we suggest a command to automatically toggle “fill” or “unfill” on the current paragraph. If there is a text selection, then the command automatically works on the region.

Here is a implementation:

(defun xah-fill-or-unfill ()
  "Reformat current paragraph or region to `fill-column', like `fill-paragraph' or “unfill”.
When there is a text selection, act on the selection, else, act on a text block separated by blank lines.
URL `http://ergoemacs.org/emacs/modernization_fill-paragraph.html'
Version 2017-01-08"
  (interactive)
  ;; This command symbol has a property “'compact-p”, the possible values are t and nil. This property is used to easily determine whether to compact or uncompact, when this command is called again
  (let ( ($compact-p
          (if (eq last-command this-command)
              (get this-command 'compact-p)
            (> (- (line-end-position) (line-beginning-position)) fill-column)))
         (deactivate-mark nil)
         ($blanks-regex "\n[ \t]*\n")
         $p1 $p2
         )
    (if (use-region-p)
        (progn (setq $p1 (region-beginning))
               (setq $p2 (region-end)))
      (save-excursion
        (if (re-search-backward $blanks-regex nil "NOERROR")
            (progn (re-search-forward $blanks-regex)
                   (setq $p1 (point)))
          (setq $p1 (point)))
        (if (re-search-forward $blanks-regex nil "NOERROR")
            (progn (re-search-backward $blanks-regex)
                   (setq $p2 (point)))
          (setq $p2 (point)))))
    (if $compact-p
        (fill-region $p1 $p2)
      (let ((fill-column most-positive-fixnum ))
        (fill-region $p1 $p2)))
    (put this-command 'compact-p (not $compact-p))))

Note: an early implementation is named “compact-uncompact-block”.

This command is part of ErgoEmacs Keybinding and Emacs: Xah Fly Keys.

Reformat Lines for Source Code

Here's a different implementation that does use fill-region commands.

Emacs: Reformat Lines for Source Code

Line Wrap Topic

  1. Hard Wrap Lines
  2. Toggle Line Wrap
  3. Reformat Lines for Source Code
  4. Visual Line Mode, Wrap Lines
  5. Novel Reading Mode
  6. toggle-word-wrap
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