(require 'cl-lib)

(defvar-local 21468-region-overlays nil)

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;;

(defun 21468-update-hunk-region (start end window rol)
  (mapc #'delete-overlay 21468-region-overlays)
  (cl-flet ((ov (start end &rest args)
                (let ((ov (make-overlay start end nil t)))
                  (while args (overlay-put ov (pop args) (pop args)))
                  (push ov 21468-region-overlays)
                  ov)))
    (let* ((align (list 'space :align-to
                        `(+ ,(window-hscroll) (0 . right))))
           (rend-line (save-excursion (goto-char end)
                                      (cons (line-beginning-position)
                                            (line-end-position))))
           (face (list :underline (face-background 'highlight nil t))))
      (message "align = %S" align)
      (ov (car rend-line) (cdr rend-line) 'face face
          'after-string (propertize "\s" 'face face 'display align 'cursor t)))))

(setq-local redisplay-highlight-region-function '21468-update-hunk-region)

(setq-local redisplay-unhighlight-region-function
            (lambda (rol) (mapc #'delete-overlay 21468-region-overlays)))

(setq-local truncate-lines t)