* lisp/ruler-mode.el (ruler-mode-ruler): Document problem.

1 files changed, 4 insertions, 0 deletions

diff --git a/lisp/ruler-mode.el b/lisp/ruler-mode.el
index 7b0588dfead..fdfd5c61be9 100644
--- a/lisp/ruler-mode.el
+++ b/lisp/ruler-mode.el
@@ -696,6 +696,10 @@ Optional argument PROPS specifies other text properties to apply."
          ;; Create an "clean" ruler.
          (ruler
           (propertize
+           ;; FIXME: `make-string' returns a unibyte string if it's ASCII-only,
+           ;; which prevents further `aset' from inserting non-ASCII chars,
+           ;; hence the need for `string-to-multibyte'.
+           ;; http://lists.gnu.org/archive/html/emacs-devel/2017-05/msg00841.html
            (string-to-multibyte
             (make-string w ruler-mode-basic-graduation-char))
            'face 'ruler-mode-default