The root cause is not fonts-katex itself but font caches holding placeholder entries for its .woff/.woff2 files: only "file" and "fontwrapper", no family and no charset. They are written by a fontconfig built with the fontations backend:
- Google Chrome 154 bundles fontconfig 2.18.3, whose cache writer replaces ~/.cache/fontconfig/*.cache-9 with symlinks to its own .cache-12 files, and fontconfig 2.17.1 reads them: https://gitlab.freedesktop.org/fontconfig/fontconfig/-/work_items/565 - On a fresh Kubuntu 26.04.1 install (image 20260826.1) the /var/cache/fontconfig/*.cache-9 file for /usr/share/fonts/truetype/katex already had these placeholders for all 40 .woff/.woff2 files, dated at image build time, although the archive's fontconfig 2.17.1 has no fontations and writes full entries for the same files. A placeholder wins every match (hence `fc-match sans` -> KaTeX_AMS- Regular.woff above), and Qt 6.10 then crashes in FcCharSetHasChar() because it does not check that the fallback pattern has a charset. Qt fixed that upstream (qtbase 80ddc8dee6a0) but not in 6.10; SRU request for qt6-base: bug 2168504. A lighter workaround than purging fonts-katex, since the same fonts are installed as .ttf: reject the web font files in ~/.config/fontconfig/conf.d/70-no-webfonts.conf <?xml version="1.0"?> <!DOCTYPE fontconfig SYSTEM "urn:fontconfig:fonts.dtd"> <fontconfig><selectfont><rejectfont> <glob>*.woff</glob><glob>*.woff2</glob> </rejectfont></selectfont></fontconfig> then run `sudo fc-cache -r -s` and `fc-cache -r`. It keeps working after Chrome rewrites its cache. (Analysed with the help of an AI assistant, Claude.) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2168311 Title: Default-installed fonts-katex crashes fontconfig (FcCharSetHasChar); Plasma won't start To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/node-katex/+bug/2168311/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
