Indent whole buffer with a keystroke

(defun my-indent-region ()
  "Mark whole buffer and indent."
  (interactive)
  (save-excursion
    (mark-whole-buffer) 
    (if (region-active-p)
 (progn
   (indent-region (point-min) (point-max))))))

Declare the function in your .emacs file. then bind it with:

(global-set-key (kbd "<f8>") 'my-indent-region)