Commit cda26e64 authored by Samuel Freilich's avatar Samuel Freilich Committed by Noam Postavsky

Do not split line before width of fill-prefix

When auto-filling a paragraph, don't split a line before the width of the
fill-prefix, creating a subsequent line that is as long or longer (Bug#20774).
* lisp/simple.el (do-auto-fill): Only consider break-points that are later in
the line than the width of the fill-prefix.  This is a more general solution
than the previous logic, which only skipped over the exact fill-prefix.  The
fill-prefix doesn't necessarily match the prefix of the first line of a
paragraph in adaptive-fill-mode.
parent 16029586
......@@ -7151,18 +7151,18 @@ Returns t if it really did any work."
(setq fill-prefix prefix))))
(while (and (not give-up) (> (current-column) fc))
;; Determine where to split the line.
(let* (after-prefix
(fill-point
(save-excursion
(beginning-of-line)
(setq after-prefix (point))
(and fill-prefix
(looking-at (regexp-quote fill-prefix))
(setq after-prefix (match-end 0)))
(move-to-column (1+ fc))
(fill-move-to-break-point after-prefix)
(point))))
;; Determine where to split the line.
(let ((fill-point
(save-excursion
(beginning-of-line)
;; Don't split earlier in the line than the length of the
;; fill prefix, since the resulting line would be longer.
(when fill-prefix
(move-to-column (string-width fill-prefix)))
(let ((after-prefix (point)))
(move-to-column (1+ fc))
(fill-move-to-break-point after-prefix)
(point)))))
;; See whether the place we found is any good.
(if (save-excursion
......@@ -7170,9 +7170,6 @@ Returns t if it really did any work."
(or (bolp)
;; There is no use breaking at end of line.
(save-excursion (skip-chars-forward " ") (eolp))
;; It is futile to split at the end of the prefix
;; since we would just insert the prefix again.
(and after-prefix (<= (point) after-prefix))
;; Don't split right after a comment starter
;; since we would just make another comment starter.
(and comment-start-skip
......
......@@ -497,5 +497,19 @@ See Bug#21722."
(should (equal (line-number-at-pos 5) 3))
(should (equal (line-number-at-pos 7) 4)))))
;;; Auto fill.
(ert-deftest auto-fill-mode-no-break-before-length-of-fill-prefix ()
(with-temp-buffer
(setq-local fill-prefix " ")
(set-fill-column 5)
;; Shouldn't break after 'foo' (3 characters) when the next
;; line is indented >= to that, that woudln't result in shorter
;; lines.
(insert "foo bar")
(do-auto-fill)
(should (string-equal (buffer-string) "foo bar"))))
(provide 'simple-test)
;;; simple-test.el ends here
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