 (defcustom snails-mode-hook '()
   "Snails mode hook."
   :type 'hook
+  :group 'snails)
+
+(defcustom snails-fame-width-proportion 0.618
+  "The width of snails frame, width ratio of the parent frame."
+  :type 'integer
+  :group 'snails)
+
+(defcustom snails-fame-height-proportion 0.618
+  "The height of snails frame, height ratio of the parent frame."
+  :type 'integer
   :group 'snails)
 
 (defface snails-header-line-face

;;      * Add new command `snails-search-point'.
;;      * Add `snails-flash-line'.
;;      * Improve `snails-sort-candidates'
;;
;; 2019/07/25
;;      * Set undecorated parameter in `make-frame' function.

         (y (nth 1 edges))
         (width (nth 2 edges))
         (height (nth 3 edges))
         (frame-width (truncate (* snails-fame-width-proportion width)))
         (frame-height (truncate (* snails-fame-height-proportion height)))
         (frame-x (/ (+ x (- width frame-width)) 2))
         (frame-y (/ (+ y (- height frame-height)) 3)))

    ;; Set project directory.
    (setq snails-project-root-dir
          (let ((project (project-current)))
