Increase text size permanently

Question

How can I set the text size to be larger all the time, starting from when I open the GUI app? I am specifically referring to the text size for the buffer and modeline.

I am moderately visually impaired. In order to read comfortably on computers, I either set the text size to be larger or use zoom. Periodically I decide I want to learn Emacs... and then I get frustrated by the tiny text and give up. I'm sure if I continued learning and experimenting, I would eventually figure out how to customize Emacs to my needs, but it's hard to do that when the text size resets to be painfully small every time I open the app.

Here's what I've tried:

In the top menu, I click Options > Set Default Font. Then I set my default font to my preferred font and text size: Hack size 12. I select Options > Save Options, and emacs adds something to my init.el:

(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 (:family "Hack Nerd Font Mono" :foundry "SRC" :slant normal :weight normal :height 120 :width normal)))))

Then I close the GUI app and open it again... and the text is back to being illegibly tiny Deja Vu Sans Mono size 10. I read this page and tried editing the code above, but nothing has worked so far. (Note: I have no experience with Lisp.)

I can also zoom in/zoom out using C-X C-+ and C-X C--. However, unlike other apps, Emacs doesn't remember my zoom level when I reopen the app.

Selecting Options > Use System Font does nothing.

System: Ubuntu 22.04.2 LTS. Gnome version: 42.9. Emacs version: GNU Emacs 27.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.30, cairo version 1.16.0) of 2022-01-24, modified by Debian. I have Ubuntu's default "Large Text" accessibility setting enabled, which makes the Emacs menu bar legible for me.

Answer 1

What you did should solve the problem. You changed the default font size and saved that change.

When you see the smaller font in a new session, try M-x customize-face default just to see if it shows the font that you set for face default. You can also use C-u C-x = on a character, and look at what the *Help* buffer tells you the font is at that location.

Display can use different faces, hence different fonts, at different locations. E.g., perhaps some font-lock highlighting (which can set the font size), or some other display shenanigans, such as a theme, can override your setting in some places or even globally.

Test with an init file that contains only that custom-set-faces code you showed, to eliminate interference from the rest of your init file. Or bisect your init file to find the culprit.