bug: Nerd fonts will probably not be usable anymore after nixpkgs 25.11

[gautaz]

Are you following the right branch?

• My Nixpkgs and Home Manager versions are in sync

Is there an existing issue for this?

• I have searched the existing issues

Issue description

Hello,

I am using home-manager with nixpkgs in a flake, both on master.
Lately a modification occurred on nixpkgs on how the nerdfonts are packaged (see NixOS/nixpkgs@de4dbc5).
Since this modification, alacritty seems unable to load the fonts.

Following are my findings while looking at the issue.

Here are the Alacritty logs:

❯ alacritty -vvv
Created log file at "/tmp/Alacritty-362931.log"
[0.000005494s] [INFO ] [alacritty] Welcome to Alacritty
[0.000146170s] [INFO ] [alacritty] Version 0.14.0
[0.000172330s] [INFO ] [alacritty] Running on X11
[0.000465610s] [INFO ] [alacritty] Configuration files loaded from:
                                     "/home/del/.config/alacritty/alacritty.toml"
[0.014992067s] [INFO ] [alacritty] Using GLX 1.4
[0.036289958s] [DEBUG] [alacritty] Picked GL Config:
                                     buffer_type: Some(Rgb { r_size: 8, g_size: 8, b_size: 8 })
                                     alpha_size: 8
                                     num_samples: 0
                                     hardware_accelerated: true
                                     supports_transparency: Some(true)
                                     config_api: Api(OPENGL | GLES1 | GLES2)
                                     srgb_capable: false
[0.037263012s] [INFO ] [alacritty] Window scale factor: 1.5
[0.039188894s] [DEBUG] [alacritty] Loading "UbuntuMono Nerd Font" font
[0.043615403s] [TRACE] [crossfont] Number of fonts is 18
[0.043643459s] [TRACE] [crossfont] Got font path="/home/del/.nix-profile/share/fonts/truetype/NerdFonts/UbuntuMonoNerdFont-Regular.ttf", index=0
[0.043661603s] [ERROR] [alacritty] Cannot open resource

The font path used by alacritty is the one listed by fc-list:

❯ fc-list | grep UbuntuMonoNerdFont-Regular.ttf
/home/del/.nix-profile/share/fonts/truetype/NerdFonts/UbuntuMonoNerdFont-Regular.ttf: UbuntuMono Nerd Font:style=Regular
/nix/store/g2q1gshfnqdnbidgp1my1iwm5747iqng-home-manager-path/share/fonts/truetype/NerdFonts/UbuntuMono/UbuntuMonoNerdFont-Regular.ttf: UbuntuMono Nerd Font:style=Regular

But the path is obviously not the right one:

❯ ls /home/del/.nix-profile/share/fonts/truetype/NerdFonts/UbuntuMonoNerdFont-Regular.ttf
ls: cannot access '/home/del/.nix-profile/share/fonts/truetype/NerdFonts/UbuntuMonoNerdFont-Regular.ttf': No such file or directory

The fonts are in fact located here:

❯ ls /home/del/.nix-profile/share/fonts/truetype/NerdFonts/UbuntuMono/
UbuntuMonoNerdFont-BoldItalic.ttf  UbuntuMonoNerdFontMono-BoldItalic.ttf  UbuntuMonoNerdFontMono-Regular.ttf      UbuntuMonoNerdFontPropo-Italic.ttf
UbuntuMonoNerdFont-Bold.ttf        UbuntuMonoNerdFontMono-Bold.ttf        UbuntuMonoNerdFontPropo-BoldItalic.ttf  UbuntuMonoNerdFontPropo-Regular.ttf
UbuntuMonoNerdFont-Italic.ttf      UbuntuMonoNerdFontMono-Italic.ttf      UbuntuMonoNerdFontPropo-Bold.ttf        UbuntuMonoNerdFont-Regular.ttf

If anyone has an idea of how to fix/workaround this, I will be happy to try 🙂.

Maintainer CC

@rycee

System information

- system: `"x86_64-linux"`
 - host os: `Linux 6.6.63, NixOS, 25.05 (Warbler), 25.05.20241128.d584552`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.24.10`
 - nixpkgs: `/etc/nixpkgs/channels/nixpkgs`

[poopsicles]

Not really sure if this is what you're asking for, but since they moved the Nerd Fonts to a new package, I recently had to update my home.nix:

• First, change your font packages to pkgs.nerd-fonts.font-name.
  So my config changed:

  home.packages = [
    ...
  - (pkgs.nerdfonts.override {
  -    fonts = ["CodeNewRoman" "FiraCode"];
  - })
  + pkgs.nerd-fonts.fira-code
  + pkgs.nerd-fonts.code-new-roman
  ]

• Switch to the latest generation (I'm using flakes, so home-manager switch --flake .)

• Even after doing this, GNOME Fonts was showing blank box characters for the fonts¹, and kitty was failing to open with this message "Failed to convert descriptor to face for medium font" because it was, like you said, looking in the older NerdFonts/ directory for font.ttf instead of digging into NerdFonts/Family/font.ttf.

  I restarted a couple of times, but after looking through fc-list and noticing there was an entry to the old version, rebuilding the font cache with fc-cache -rv worked (-r means "really force". v means verbose) fixed things; Fonts displays them well now, kitty runs fine.

I'm surprised home-manager switch doesn't reload the font cache, because I thought it does (maybe it does lol but not with the "yes force everything" option.

Footnotes

1. ↩

[cloudlena]

Thanks, @poopsicles! Running fc-cache -rv fixed it for me 😊

[poopsicles]

I'm surprised home-manager switch doesn't reload the font cache, because I thought it does (maybe it does lol but not with the "yes force everything" option.

Looked around and found #520, which linked to #682 which added in this file:

home-manager/modules/misc/fontconfig.nix

Lines 108 to 113 in 8632735

	${getBin pkgs.fontconfig}/bin/fc-cache -f
	rm -f $out/lib/fontconfig/cache/CACHEDIR.TAG
	rmdir --ignore-fail-on-non-empty -p $out/lib/fontconfig/cache
	rm "$FONTCONFIG_FILE"
	unset FONTCONFIG_FILE

So it does refresh the cache, but with -f over r, the differences between them which are:

$ fc-cache -h
...
-f, --force                 scan directories with apparently valid caches
-r, --really-force       erase all existing caches, then rescan
...

I'm not sure if that needs to be switched to -r, especially since they seem to be removing the cache directory afterwards anyways (maybe $out is actually the flake or something...Nix confuses me)

But anyways, tl;dr is to force the cache to actually get cleared first if any font problems occur (though that's probably unlikely...in this case the folder structure of the fonts was changed).

[gautaz]

Hello @poopsicles,

Thanks for your fix!

First, change your font packages to pkgs.nerd-fonts.font-name.

Yes, this one was already done.

rebuilding the font cache with fc-cache -rv worked

This is what was missing 🙂.

My assumption was that home-manager was already doing this, but seems it is not, good catch 👍.

Looking back at #682, it is in fact:

${getBin pkgs.fontconfig}/bin/fc-cache -f

Perhaps @rycee has more insight on this matter.