Question

I’d like to do something like fill-region, except that I want to select a rectangle region and wrap only the text inside it, and have it stay within the rectangle bounds. Is there a way to do this?

Answer 1

Edit: Ah, I knew I’d encountered this ability before.

The rectangle editing abilities in cua provide this feature.

So first enable cua-selection-mode. That’s the good stuff in CUA without the copy/cut/paste key changes, so you might want it on permanently:

(cua-selection-mode 1)

And then C-RET to mark a corner, move point to the opposite corner, and C-q as normal to fill. C-RET again to exit the rectangle mode.

CUA’s rectangle editing is pretty awesome. Read about it in the commentary of M-x find-library RET cua-base RET. Look for the “CUA rectangle support” heading.

Original answer:

(defun my-fill-rectangle (start end)
  "`fill-region' within the confines of a rectangle."
  (interactive "*r")
  (let* ((indent-tabs-mode nil)
         (content (delete-extract-rectangle start end)))
    (goto-char start)
    (insert-rectangle
     (with-temp-buffer
       (setq indent-tabs-mode nil
             fill-column (length (car content)))
       (insert-rectangle content)
       (fill-region (point-min) (point-max))
       (goto-char (point-max))
       (move-to-column fill-column t)
       (extract-rectangle (point-min) (point))))))