Question

notepad++ allow me to increase the font size when I hold the Ctrl Key and rotate the mouse middle scroll button to forward.

In the same way, the when I hold Ctrl and rotate the mouse middle scroll button backward, the fond size reduces.

How can I get the same with Emacs?

Answer 1

code for AlexCombas’ answer:

(defun font-big ()
 (interactive)
 (set-face-attribute 'default nil :height 
  (+ (face-attribute 'default :height) 10)))

(defun font-small ()
 (interactive)
 (set-face-attribute 'default nil :height 
  (- (face-attribute 'default :height) 10)))

(global-set-key (kbd "<C-wheel-down>") 'font-small)
(global-set-key (kbd "<C-wheel-up>") 'font-big)

Edit: for a min and a max use

(defun font-big ()
 (interactive)
 (set-face-attribute 'default nil :height 
  (min 720
   (+ (face-attribute 'default :height) 10))))

(defun font-small ()
 (interactive)
 (set-face-attribute 'default nil :height 
  (max 80
   (- (face-attribute 'default :height) 10))))