mood-line-segment-scroll-bar.el

;; Following is inspired by MLScroll (https://github.com/jdtsmith/mlscroll), intended
;; to replace mood-line-segment-scroll in mood-line (https://git.tty.dog/hpet_dog/mood-line).

(defun window-scroll-percentage ()
  "Return current position in window, as a fraction, accounting for window height."
  (let* ((end (window-end))
         (total (point-max)))
    (if (< end total)
        (let* ((start (window-start)))
          (/ (float start) (+ (- total end) start)))
      1)))
;; MLScroll tries to be smart about optimizing, the above, but 
;; (benchmark-run 10000 (window-scroll-percentage)) is less than 0.007 on
;; Emacs 30 and my current MacBook Air M2.

(defun mood-line-segment-scroll-bar (width)
  "Draws a bar of total WIDTH, showing the current scroll position in the window,
to be used in mood-line"
  (let* ((pos (round (* width (window-scroll-percentage)))))
    (concat
     (make-string pos ?▒)
     (make-string (- width pos ) ? ))))