Display Braille Characters btop, 25.11, kde plasma

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1

Hey everyone

(I’m new to NixOS and besides the ease of being able to have a declarative approach to system management, I’ve found my way here, because I really wanted to give hyperland a try. And I didn’t feel like fucking and unfucking my Kubuntu install several times to get that to work. So here I am.)

I was trying to slowly migrate my configuration over to my new NixOS when I came across the first problem I didn’t manage to resolve on my own. Running btop, there’s a “halo” where the empty Braille characters are. This Github issue has some pictures of the problem. The issue only exists with Konsole, KWrite and Kate. Using Wezterm, the problem disappears. My guess is, under the hood, the kde applications fall back on some other font that has this horrible rendering. This means I a) need to find that setting and change the font to something usable or b) I uninstall all fonts that display Braille so poorly.

What I have done so far:

  • Initially I installed nerd-fonts.* packages (so all nerdfonts that are available) to have the best chance of working. It didn’t.
  • Changed the Font inside Konsole to be JetbrainsMono Nerd Font
  • Changed the Fixed-Width Font ins System Settings to JetbrainsMono Nerd Font
  • Attempted to find Gnu-Free-Fonts inside my fonts and also inside my packages without success.

Did somebody also encounter this issue? How did you fix it? And how do I figure out what font or what font render setting is responsible for displaying such a beautiful application like btop in such a poor way?

Thank you for your support.

AS2k

2

I’ve got some news: I found the font responsible for the ugly rendering!

I had ChatGPT whip up this script to test which fonts can display the Braille characters:

#!/usr/bin/env bash

BRAILLE_STR="⣸⣀⣸⣶⣤⣀⣀⣀⣀⣄⣀"

echo -e "Font Family \t\t\t | Rendering"
echo -e "----------------------------------------------------------------"

# 1. Get all fonts that are Monospace (spacing=100)
# 2. Filter for those that contain the Braille range (charset=2800)
# 3. Loop through and print the name + the string
fc-list ":spacing=100:charset=2800" family | cut -d',' -f1 | sort -u | while read -r font; do
    # We use python or perl to print because bash 'echo' can sometimes
    # struggle with specific unicode escapes in older shells
    printf "%-32s | %b\n" "$font" "$BRAILLE_STR"
done

Using that I came to the conclusion, that FreeMono is the culprit for the ugly rendering. Looking at it on nixpkgs, this is also not really surprising as it is an “outline” font apparently. It is provided by freefont_ttf.

I’m not entirely sure, if this is in fact the same font as the one in the Github Issue or if it’s something else.

I’m now facing the question, solve this problem by somehow telling nix to keep freefont_ttf out of my system (which I’d prefer honestly) or if I work with the font config and somehow define another font or fonts as a fallback if the current font cannot render a given unicode charcter.

— I’ll keep this post up to date with whatever solution I end up choosing. Tho suggestions are always appreciated.

AS2k