;;; この設定を入れるとEmacsを終了してもfoldが持続する
;; (setq fold-this-persistent-folds t)
(defun fold-this--this-or-all (all)
  (interactive "P")
  (let ((x (bounds-of-thing-at-point 'sexp))
        (rap (region-active-p)))
    (funcall (if all 'fold-this-all 'fold-this)
             (if rap (region-beginning) (car x))
             (if rap (region-end) (cdr x))))
  (message (substitute-command-keys "To unfold all, try \\[fold-this-unfold-all]")))
(with-eval-after-load "view"
  (define-key view-mode-map (kbd "f") 'fold-this--this-or-all))