my-font-size-manage.el

  (defvar default-font-size 12)
  (setq target-font-size default-font-size)
  
  (global-set-key (kbd "C-x C-=") 'increase-font-size)
  (global-set-key (kbd "C-x C--") 'decrease-font-size)
  (global-set-key (kbd "C-x C-0") 'reset-font-size)

  (defun my-ja-font-setter (spec)
      (set-fontset-font nil 'japanese-jisx0208 spec)
      (set-fontset-font nil 'katakana-jisx0201 spec)
      (set-fontset-font nil 'japanese-jisx0212 spec)
      (set-fontset-font nil '(#x0080 . #x024F) spec)
      (set-fontset-font nil '(#x0370 . #x03FF) spec)
      (set-fontset-font nil 'mule-unicode-0100-24ff spec))
    
  (defun my-ascii-font-setter (spec)
    (set-fontset-font nil 'ascii spec))      
    
  (defun increase-font-size ()
    (interactive)
    (setq target-font-size (+ target-font-size 1))
    (set-font-size target-font-size)
    (message "+1: %s" target-font-size))
  
  (defun decrease-font-size ()
    (interactive)
    (setq target-font-size (- target-font-size 1))
    (set-font-size target-font-size)
    (message "-1: %s" target-font-size))
  
  (defun reset-font-size ()
    (interactive)
    (set-font-size default-font-size)
    (setq target-font-size default-font-size)
    (message "0: %s" target-font-size))
  
  (defun set-font-size-input (n)
    (interactive "nSize: ")
    (setq target-font-size n)
    (set-font-size target-font-size)
    (message "0: %s" target-font-size))
  
  (defun set-font-size (arg)
    (interactive "p")
    (let* ((font-size arg)
          (frame-width 80)
          (frame-height (if (> arg 15) 20 40))
          (ja-font-scale 1.2)
          (ja-font "Migu 2M")
          (ascii-font "Monaco"))
      
      (my-ascii-font-setter (font-spec :family ascii-font :size font-size))
      (my-ja-font-setter (font-spec :family ja-font :size font-size))
      (setq face-font-rescale-alist
            `((".*Migu.*" . ,ja-font-scale)))
      (set-frame-size (selected-frame) frame-width frame-height)))