Re: use of symbolic display elements in ruler-mode

[Stefan Monnier]

>  (defvar ruler-mode-ruler-function nil
> -  "If non-nil, function to call to return ruler string.
> +  "If non-nil, function to call to return ruler header line format.
>  This variable is expected to be made buffer-local by modes.")
>  (defconst ruler-mode-header-line-format
> -  '(:eval (funcall (if ruler-mode-ruler-function
> -                    ruler-mode-ruler-function
> -                  'ruler-mode-ruler)))
> +  '(:eval (funcall (or ruler-mode-ruler-function 'ruler-mode-ruler)))
>    "`header-line-format' used in ruler mode.
> -If the non-nil value for ruler-mode-ruler-function is given, use it.
> -Else use `ruler-mode-ruler' is used as default value.")
> +If `ruler-mode-ruler-function' is non-nil, call it to compute the
> +ruler value, else use `ruler-mode-ruler'.")

Why not just:

(defvar ruler-mode-ruler-function 'ruler-mode-ruler
  "Function to call to return ruler string.")
(defconst ruler-mode-header-line-format
  '(:eval (funcall ruler-mode-ruler-function))
   "`header-line-format' used in ruler mode.")


-- Stefan