Re: wdired.el 1.7 --- Rename files editing their names in dired buffers

[Richard Stallman]

    (defun replace-match-non-writable-p()
      "Check that the chars of the last match do not have read-only properties."
      (or buffer-read-only
          (let ((pos-beg (- (match-beginning 0) 1))
                (pos-end (- (match-end 0) 1)))
            (setq pos-beg (max pos-beg 1))
            (while (and (< pos-beg pos-end)
                        (not (get-text-property pos-beg 'read-only)))
              (setq pos-beg (1+ pos-beg)))
            (get-text-property pos-beg 'read-only))))

That loop by characters is slow.  Instead, use text-property-not-all
to see if any character has a non-nil `read-only' property.