My default face only supports one size

Question

I am trying to restore the face scaling functionality I had in previous versions of Emacs.

On Ubuntu 22.04, Emacs (not 30!) master branch d4d6830f8a0. Tested on tag emacs-29.2 with the same result.

I installed terminus like this:

sudo apt install xfonts-terminus

My init file does this:

(when (member "Terminus" (font-family-list))
  (set-frame-font "Terminus:size=18" nil t)
  (add-to-list 'default-frame-alist '(font . "Terminus:size=18")))

No matter what size I set, my emacs buffers always look the same. I've try to write height instead of size, no difference.

How do I change the size of my emacs face? Do I need to install different font sizes at system level?

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Edit: I previously set the default face like this:

(when (member "Terminus" (font-family-list))
  (set-frame-font "-xos4-Terminus-normal-normal-normal-*-12-*-*-*-c-60-iso10646-1")
  (add-to-list 'default-frame-alist '(font . "-xos4-Terminus-normal-normal-normal-*-12-*-*-*-c-60-iso10646-1")))

If I replace 12 with 18, I do get a difference. text-scale-decrease does have an effect then, but it's weird, the decrement/increments are very small, not all characters are supported, it sometimes switches to italics... Which makes me think that this is not the correct way.

Answer 1

Terminus is a bitmap font; it only supports specific sizes. If you want a font that can scale to any arbitrary size, find a vector (TrueType or OpenType) font that you like.

From the package description:

This package contains normal and bold fonts in the following sizes: 6x12, 8x14, 8x16, 10x20, 11x22, 12x24, 14x28 and 16x32 and supports the following encodings: ISO10646-1, ISO8859-1, ISO8859-2, ISO8859-5, ISO8859-9, ISO8859-13, ISO8859-15, ISO8859-16, KOI8-R, KOI8-U, CP1251 and PT154.

Also from the description:

Note: You might want to use the package fonts-terminus-otb instead of this package because the fonts in this package are used by the X server directly. Several modern applications will ignore such fonts.

Emacs won't ignore server–side fonts, but while it does install OpenType fonts they’re still bitmap fonts and not vector fonts.