Checking values returned by window-scroll-bars

[Heime <heimeborgia@protonmail.com>]

I want to indicate whether a WINDOW uses the frame's corresponding value.
It is not as simple as just checking (window-scroll-bars).  How can I do
it ?  

(defun window-scroll-bar-info ()

  ;; Value is a list of the form (WIDTH COLUMNS VERTICAL-TYPE
  ;; HEIGHT LINES HORIZONTAL-TYPE PERSISTENT)

  ;; If WIDTH or HEIGHT is nil, or alternatively, when VERTICAL-TYPE
  ;; or HORIZONTAL-TYPE is t, the WINDOW uses the frame's
  ;; corresponding value."

  (interactive)

  (if (window-scroll-bars)
      (message "This window has its own scroll bars enabled.")
    (message "No custom scroll bars are enabled for this window."))

    (prin1 (window-scroll-bars)))