Cannot resolve font with fontconfig 2.13.96

[sQVe]

Describe the bug
I set my font via fontconfig and with the following section:

<alias>
  <family>term</family>
  <prefer>
    <family>Iosevka Nerd Font</family>
    <family>Symbols Nerd Font</family>
    <family>Noto Color Emoji</family>
    <family>Symbola</family>
  </prefer>
</alias>

# Font specific.
font_family term
bold_font auto
italic_font auto
bold_italic_font auto
disable_ligatures always
font_size 10.0

I just updated fontconfig from 2.13.94 to 2.13.96 and my alias isn't working anymore. Downgrading fontconfig solves it.

To Reproduce
Steps to reproduce the behavior:

1. Update to latest fontconfig (2.13.96).
2. Add an font alias to fonts.conf.
3. Use the font alias in `kitty.
4. Font isn't loaded properly.

Environment details

kitty 0.24.2 created by Kovid Goyal
Linux calcifer 5.16.5-arch1-1 #1 SMP PREEMPT Tue, 01 Feb 2022 21:42:50 +0000 x86_64
CALCIFER

Running under: X11
Frozen: False
Paths:
  kitty: /usr/bin/kitty
  base dir: /usr/lib/kitty
  extensions dir: /usr/lib/kitty/kitty
  system shell: /usr/bin/zsh
Loaded config files:
  /home/sqve/.config/kitty/kitty.conf

Config options different from defaults:
cursor_blink_interval 0.0
disable_ligatures     2
enable_audio_bell     False
enabled_layouts       ['grid', 'horizontal', 'vertical']
font_family           term
font_size             10.0
open_url_with         ['mimeo']
remember_window_size  False
scrollback_pager      ['/home/sqve/scripts/kitty/neovim-scrollback.sh']
shell_integration     frozenset({'no-cursor'})
tab_bar_style         separator
tab_separator          │ 
window_padding_width  FloatEdges(left=2.0, top=2.0, right=2.0, bottom=2.0)
Added shortcuts:
  ctrl+shift+p → previous_window
  ctrl+alt+l → kitten hints --type line --program -
  ctrl+alt+p → kitten hints --type path --program -
  ctrl+alt+u → kitten hints --type path
  ctrl+alt+w → kitten hints --type word --program -
Removed shortcuts:
  ctrl+shift+p > f → kitten hints --type path --program -
  ctrl+shift+p > h → kitten hints --type hash --program -
  ctrl+shift+p > l → kitten hints --type line --program -
  ctrl+shift+p > n → kitten hints --type linenum
  ctrl+shift+p > w → kitten hints --type word --program -
  ctrl+shift+p > y → kitten hints --type hyperlink
  ctrl+shift+p > shift+f → kitten hints --type path
Changed shortcuts:
  ctrl+shift+n → next_window
Colors:
  background            #282828   
  color0                #665c54   
  color1                #ea6962   
  color10               #a9b665   
  color11               #d8a657   
  color12               #7daea3   
  color13               #d3869b   
  color14               #89b482   
  color15               #d4be98   
  color2                #a9b665   
  color3                #e78a4e   
  color4                #7daea3   
  color5                #d3869b   
  color6                #89b482   
  color7                #d4be98   
  color8                #928374   
  color9                #ea6962   
  cursor                #ebdbb2   
  cursor_text_color     #282828   
  foreground            #fbf1c7   
  selection_background  #44475a   
  selection_foreground  #ebdbb2   

Environment variable names seen by the kitty process:
  ANDROID_AVD_HOME
  ANDROID_EMULATOR_HOME
  ANDROID_SDK_HOME
  AWS_CONFIG_FILE
  BIN
  BIN_HOME
  BOOKS
  BROWSER
  CODE
  CUDA_CACHE_PATH
  DBUS_SESSION_BUS_ADDRESS
  DISPLAY
  DOCKER_CONFIG
  DOTFILES
  DOWNLOAD
  EDITOR
  ESLINT_D_LOCAL_ESLINT_ONLY
  EXA_COLORS
  FZF_ALT_C_COMMAND
  FZF_ALT_C_OPTS
  FZF_CTRL_T_COMMAND
  FZF_CTRL_T_OPTS
  FZF_DEFAULT_COMMAND
  FZF_DEFAULT_OPTS
  GIT_SSH_COMMAND
  GONOSUMDB
  GOPATH
  GOPATH_BIN
  GOPROXY
  GPG_TTY
  GREP_COLORS
  GTK2_RC_FILES
  GTK3_MODULES
  GTK_MODULES
  HISTFILE
  HOME
  HTTPIE_CONFIG_DIR
  I3SOCK
  INVOCATION_ID
  KEYTIMEOUT
  KUBECONFIG
  LANG
  LC_MESSAGES
  LESS
  LESSHISTFILE
  LESSOPEN
  LOGNAME
  LS_COLORS
  MAIL
  MOTD_SHOWN
  NODE_REPL_HISTORY
  NOTES
  NPM_CONFIG_CACHE
  NPM_CONFIG_USERCONFIG
  NVM_DIR
  OLDPWD
  PAGER
  PASSWORDS
  PASSWORD_STORE_DIR
  PASSWORD_STORE_GENERATED_LENGTH
  PASSWORD_STORE_GPG_OPTS
  PATH
  PERSISTENT_CACHE
  PICTURES
  PRETTIERD_LOCAL_PRETTIER_ONLY
  PROMPT_LEAN_VIMODE
  PROMPT_LEAN_VIMODE_FORMAT
  PWD
  RCRC
  RIPGREP_CONFIG_PATH
  SCRIPTS
  SHELL
  SHLVL
  SSB_HOME
  SSH_AUTH_SOCK
  SUDO_ASKPASS
  SYSTEMD_EXEC_PID
  TERM
  TERMINAL
  TRASH
  USER
  VISUAL
  WEECHAT_HOME
  WINDOWPATH
  WINIT_X11_SCALE_FACTOR
  WORK
  XAUTHORITY
  XDG_CACHE_HOME
  XDG_CONFIG_HOME
  XDG_DATA_HOME
  XDG_RUNTIME_DIR
  XDG_SEAT
  XDG_SESSION_CLASS
  XDG_SESSION_ID
  XDG_SESSION_TYPE
  XDG_STATE_HOME
  XDG_VTNR
  YARN_CACHE_FOLDER
  YVM_DIR
  ZDOTDIR
  ZIM_HOME
  ZSH_AUTOSUGGEST_HIGHLIGHT_STYLE
  ZSH_AUTOSUGGEST_USE_ASYNC
  _
  _ZL_DATA
  _ZL_FZF_FLAG
  _ZL_MATCH_MODE

[kovidgoyal]

Then report it to the fontconfig project.

[kovidgoyal]

And just for the record, you dont need to do all this dancing in
fontconfig. Simply set unpatched Iosevka see the note here: https://sw.kovidgoyal.net/kitty/faq/#kitty-is-not-able-to-use-my-favorite-font

[sQVe]

Sure - I'll do that.

What's confusing is that my fontconfig setup works fine for other applications, like i3wm, which is why I reported it here first as kitty is the only application I've seen so far that has problems resolving the fonts.

[kovidgoyal]

It isn't not resolving the font, fontconfig has probably reclassified it
as non-monospace, one of the hazards of using patched fonts. Just use
unpatched ones.

[sQVe]

Great tip @kovidgoyal.

I'm trying to find the standalone NERD font but the closes I'm finding on my system (Arch) is ttf-nerd-fonts-symbols. 🤔

[page-down]

I'm trying to find the standalone NERD font ...

I get it from the following location.

https://github.com/ryanoasis/nerd-fonts/tree/2.2.0-RC/src/glyphs

Symbols-1000-em Nerd Font Complete.ttf

I had compared the file hash from that package before and it is the same.

[sQVe]

@page-down Thank you! ❤️

I just tried running:

<alias>
  <family>term</family>
  <prefer>
    <family>Iosevka</family>
  </prefer>
</alias>

and it's still unable to resolve the font 🤔

[page-down]

I installed and tried it specifically. Can not reproduce this.

https://github.com/be5invis/Iosevka/releases/download/v11.3.0/ttc-sgr-iosevka-11.3.0.zip

# Arch Linux
# fontconfig 2:2.13.96-1
# kitty 0.24.2 from github releases, and kitty compiled from src

# kitty -o 'font_family term' --debug-font-fallback
Preloaded font faces:
normal face: ~/.local/share/fonts/sgr-iosevka-regular.ttc:0
bold face: ~/.local/share/fonts/sgr-iosevka-bold.ttc:0
italic face: ~/.local/share/fonts/sgr-iosevka-regular.ttc:3
bi face: ~/.local/share/fonts/sgr-iosevka-bold.ttc:3

It is worth noting that I did not install kitty from archlinux.

EDIT:
I tried what you mentioned below, and it does get abnormal if you make aliases to monospace. (archlinux fontconfig 2.13.96-1)
When I downgraded to fontconfig 2.13.94 it was back to normal.

[sQVe]

@page-down Cheers for helping me debug this! ❤️ I've now narrowed this down to:

<?xml version='1.0'?>
<!DOCTYPE fontconfig SYSTEM 'fonts.dtd'>
<fontconfig>
  <!-- Set preferred serif, sans serif, and monospace fonts. -->
  <alias>
    <family>monospace</family>
    <prefer>
      <family>Cousine</family>
      <family>Noto Color Emoji</family>
    </prefer>
  </alias>
  <alias>
    <family>term</family>
    <prefer>
      <family>Iosevka</family>
      <family>Symbols Nerd Font</family>
      <family>Noto Color Emoji</family>
      <family>Symbola</family>
    </prefer>
  </alias>
</fontconfig>

Strangely enough it seems like kitty prefers the monospace alias before my term alias that I specifically set. Everything resolves nicely if I remove the monospace alias.

---

Running fc-match "term" give me:

iosevka-regular.ttc: "Iosevka" "Regular"

but kitty -o 'font_family term' --debug-font-fallback gives me:

[038 14:34:54.265336] Preloaded font faces:
[038 14:34:54.265374] normal face: /usr/share/fonts/croscore/Cousine-Regular.ttf:0
[038 14:34:54.265387] bold face: /usr/share/fonts/croscore/Cousine-Bold.ttf:0
[038 14:34:54.265402] italic face: /usr/share/fonts/croscore/Cousine-Italic.ttf:0
[038 14:34:54.265413] bi face: /usr/share/fonts/croscore/Cousine-BoldItalic.ttf:0

[sQVe]

I "sort of" solved this by using the monospace alias instead of the term alias.

sQVe/dotfiles@d145168#diff-4fb4286f5f5e882fcae1801191828518c19485e7ce77727b05f47838fa3db65c

[kovidgoyal]

That happens because Iosevka is dual spaced not monospaced so fc-match returns your actual monospaced font and because you are selecting it by an alias not an actual font name, there is no way for kitty to check if fc-match has returned what you wanted. Check it yourself with:

fc-match term:spacing=mono