elisp animated spinner generator

generate-spinner.el

;; to generate an animated spinner
;;
;; starting from from this:
;; ".oO@Oo."
;;
;; and producing this:
;; ["[    ]"
;;  "[.   ]"
;;  "[o.  ]"
;;  "[Oo. ]"
;;  "[@Oo.]"
;;  "[O@O.]"
;;  "[oO@O]"
;;  "[.oO@]"
;;  "[ .oO]"
;;  "[  .o]"
;;  "[   .]"]
;;
;; suitable for passing into `spinner-start'

(require 'spinner)

(defun generate (body left right width)
  (let* ((pad (concat (make-string width ? ) body))
         (wrap (concat pad pad))
         (result nil))
    (dolist (i (number-sequence (1- (length pad)) 0 -1))
      (push (format "%s%s%s"
                    left
                    (substring wrap i (+ i width))
                    right)
            result))
    (vconcat result)))


;; single character looks like it "pulses"
;; (spinner-start (generate ".:+*O*+:." "[" "]" 1))
;; (spinner-stop)

;; rolling string is a "breather"
;; (spinner-start (generate ".oO@Oo." "[" "]" 4))
;; (spinner-stop)

;; can also be a rolling marquee with text
;; (spinner-start (generate "Gathering results..." "[" "]" 5))
;; (spinner-stop)

;; easy to reverse the direction
;; (spinner-start (nreverse (generate "<(O)>" "{" "}" 20)))
;; (spinner-stop)