+(defun toggle-word-wrap (&optional arg)
+ "Toggle whether to use word-wrapping for continuation lines.
+With prefix argument ARG, wrap continuation lines at word boundaries
+if ARG is positive, otherwise wrap them at the right screen edge.
+This command toggles the value of `word-wrap'. It has no effect
+if long lines are truncated."
+ (interactive "P")
+ (setq word-wrap
+ (if (null arg)
+ (not word-wrap)
+ (> (prefix-numeric-value arg) 0)))
+ (force-mode-line-update)
+ (message "Word wrapping %s"
+ (if word-wrap "enabled" "disabled")))
+