*** empty log message ***

1 files changed, 37 insertions, 4 deletions

diff --git a/lisp/textmodes/fill.el b/lisp/textmodes/fill.el
index bc6ae99bae8..ed46490174d 100644
--- a/lisp/textmodes/fill.el
+++ b/lisp/textmodes/fill.el
@@ -133,23 +133,56 @@ From program, pass args FROM, TO and JUSTIFY-FLAG."
       (insert "  ")
       (goto-char (point-min))
 
-      (let ((prefixcol 0))
+      ;; This is the actual filling loop.
+      (let ((prefixcol 0) linebeg)
         (while (not (eobp))
+          (setq linebeg (point))
           (move-to-column (1+ fill-column))
           (if (eobp)
               nil
-            (skip-chars-backward "^ \n")
+            ;; Move back to start of word.
+            (skip-chars-backward "^ \n" linebeg)
+            ;; Don't break after a period followed by just one space.
+            ;; Move back to the previous place to break.
+            ;; The reason is that if a period ends up at the end of a line,
+            ;; further fills will assume it ends a sentence.
+            ;; If we now know it does not end a sentence,
+            ;; avoid putting it at the end of the line.
+            (while (and (> (point) (+ linebeg 2))
+                        (eq (preceding-char) ?\ )
+                        (eq (char-after (- (point) 2)) ?\.))
+              (forward-char -2)
+              (skip-chars-backward "^ \n" linebeg))
             (if (if (zerop prefixcol) (bolp) (>= prefixcol (current-column)))
-                (skip-chars-forward "^ \n")
+                ;; Keep at least one word even if fill prefix exceeds margin.
+                ;; This handles all but the first line of the paragraph.
+                (progn
+                  (skip-chars-forward " ")
+                  (skip-chars-forward "^ \n"))
+              ;; Normally, move back over the single space between the words.
               (forward-char -1)))
-          ;; Inserting the newline first prevents losing track of point.
+            (if (and fill-prefix (zerop prefixcol)
+                     (< (- (point) (point-min)) (length fill-prefix))
+                     (string= (buffer-substring (point-min) (point))
+                              (substring fill-prefix 0 (- (point) (point-min)))))
+                ;; Keep at least one word even if fill prefix exceeds margin.
+                ;; This handles the first line of the paragraph.
+                (progn
+                  (skip-chars-forward " ")
+                  (skip-chars-forward "^ \n")))
+          ;; Replace all whitespace here with one newline.
+          ;; Insert before deleting, so we don't forget which side of
+          ;; the whitespace point or markers used to be on.
           (skip-chars-backward " ")
           (insert ?\n)
           (delete-horizontal-space)
+          ;; Insert the fill prefix at start of each line.
+          ;; Set prefixcol so whitespace in the prefix won't get lost.
           (and (not (eobp)) fill-prefix (not (equal fill-prefix ""))
                (progn
                  (insert fill-prefix)
                  (setq prefixcol (current-column))))
+          ;; Justify the line just ended, if desired.
           (and justify-flag (not (eobp))
                (progn
                  (forward-line -1)