Can't adjust font size anymore in emacs 25

Question

I just upgraded Emacs to 25.1.1 (via the Arch Linux package manager pacman).

Now I can't set the font size in my .emacs anymore.

I am able to adjust it via C-x C-+ and C-x C--, and I can also use M-x customize to set the default font height to 83 instead of 103. This works for my current session in all buffers, then.

But when I save the generated config code (attached below) in my .emacs and restart, the settings are ignored and Emacs starts with the default font size instead. I am confused as to where to start searching for the cause of the problem, since it works if I adjust it in each session, but does not work when restarting Emacs.

There is no error message and nothing of help in the *Messages* buffer.

Where can I start looking for the problem?

I must add that I have no idea about how Emacs-Lisp works and can only copy-paste things into my config file. It's a very confusing language for me.

(custom-set-variables
 ;; custom-set-variables was added by Custom.
 ;; If you edit it by hand, you could mess it up, so be careful.
 ;; Your init file should contain only one such instance.
 ;; If there is more than one, they won't work right.
 )
(custom-set-faces
 ;; custom-set-faces was added by Custom.
 ;; If you edit it by hand, you could mess it up, so be careful.
 ;; Your init file should contain only one such instance.
 ;; If there is more than one, they won't work right.
 '(default ((t (:inherit nil :stipple nil :background "white" :foreground "black" :inverse-video nil :box nil :strike-through nil :overline nil :underline nil :slant normal :weight normal :height 83 :width normal :foundry "PfEd" :family "DejaVu Sans Mono"))))
 '(tabbar-button ((t (:inherit tabbar-default :foreground "dark red"))))
 '(tabbar-button-highlight ((t (:inherit tabbar-default))))
 '(tabbar-default ((t (:inherit variable-pitch :background "#959A79" :foreground "black" :weight bold))))
 '(tabbar-highlight ((t (:underline t))))
 '(tabbar-selected ((t (:inherit tabbar-default :background "#95CA59"))))
 '(tabbar-separator ((t (:inherit tabbar-default :background "#95CA59"))))
 '(tabbar-unselected ((t (:inherit tabbar-default)))))

Answer 1

This is most likely an instance of Emacs bug#25228 - custom-set-faces from init file ~/.emacs ignored. Basically Emacs is applying gconf settings which override your customization (Emacs versions prior to 25.1 apparently had some bug which prevented the settings from applying at all). To disable gconf updates, add this your .emacs:

(define-key special-event-map [config-changed-event] #'ignore)

Answer 2

You can use this command to increase the font size,

(set-face-attribute 'default nil :height 165)

It works for me on Mac - Emacs 25.1.50