Bug 504556

Summary: Fonts turned into boxes due to bad cache
Product: [Plasma] plasmashell Reporter: Tobias G. <kde-bugzilla.oink169>
Component: generalAssignee: Plasma Bugs List <plasma-bugs-null>
Status: RESOLVED UPSTREAM    
Severity: normal CC: kde, kdedev, nate, xaver.hugl
Priority: NOR    
Version First Reported In: 6.3.5   
Target Milestone: 1.0   
Platform: openSUSE   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: No text, only boxes

Description Tobias G. 2025-05-20 09:12:05 UTC
Created attachment 181554 [details]
No text, only boxes

SUMMARY
Hi there, since yesterday evening, all fonts are gone throughout KDE on my system. I don't know why, I started two distroboxes and now on my complete system there are no texts anymore lol
Luckily though, apps installed through flatpak still work, so I can at least create this bug report.
I attached a screenshot to show the issue.
I found this reddit post: https://www.reddit.com/r/archlinux/comments/d4mm4a/arch_linux_kde_plasma_displaying_squares_instead/
which sounds and looks very similar.
It seems like QT apps are affected.

However, I could copy the system information from the "About system" page, so copying text seems to work :D

STEPS TO REPRODUCE
Unfortunately, I don't know how to reproduce this. Maybe something changed my GTK settings, though I don't know why (I installed virt-manager in a distrobox, could this be the issue?)

OBSERVED RESULT
All system QT apps show boxes instead of text

EXPECTED RESULT
My apps have text

SOFTWARE/OS VERSIONS
Operating System: Yuga Linux 20250515
KDE Plasma Version: 6.3.5
KDE Frameworks Version: 6.14.0
Qt Version: 6.9.0
Kernel Version: 6.13.7-1-yuga (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 7840U w/ Radeon  780M Graphics
Memory: 30.7 GiB of RAM
Graphics Processor: AMD Radeon 780M
Manufacturer: Framework
Product Name: Laptop 13 (AMD Ryzen 7040Series)
System Version: A7

ADDITIONAL INFORMATION
Yuga Linux is based on openSUSE and uses the official openSUSE Tumbleweed repositories
Comment 1 Tobias G. 2025-05-20 09:22:35 UTC
Nope, the reddit issue is soething else, I don't know how to fix it :D
It looks like the fonts are missing, but I can't check what font is selected/available because the font menu in system settings is also just boxes that I can't seem to copy.
Comment 2 Tobias G. 2025-05-20 09:23:17 UTC
In .config/kcmfonts the only content is
[General]
forceFontDPI=0
Comment 3 Tobias G. 2025-05-20 17:11:30 UTC
I fixed the issue. :)
Turns out my font cache was broken as it seems for some reason.

When I ran fc-list | head it returned nothing at all.
So I did:
rm -rf ~/.cache/fontconfig
sudo rm -rf /var/cache/fontconfig
And to rebuild the cache:
sudo fc-cache -r -v
fc-cache -r -v

I rebuilt it for root and for my local user, as I guess both are relevant?

Anyway, now it's working again after logging out and back in yey! I can use my notebook again :)

I leave this open as I guess that Plasma should _try_ to detect this situation and handle it itself - being left with empty boxes is NOT a great experience and rendered me almost unable to do anything.
Comment 4 TraceyC 2025-05-20 18:52:22 UTC
I'm glad to hear you found the root cause of the problem. 

I'm not seeing this in OpenSuse Tumbleweed or on Solus git-master. I'll let developers more versed in the font cache take a further look.
Comment 5 Tobias G. 2025-06-17 10:07:46 UTC
(In reply to TraceyC from comment #4)
> I'm glad to hear you found the root cause of the problem. 
> 
> I'm not seeing this in OpenSuse Tumbleweed or on Solus git-master. I'll let
> developers more versed in the font cache take a further look.

Hi, it happened to me again.
I setup a distrobox with virt-manager following the official guide:
https://github.com/89luca89/distrobox/blob/main/docs/posts/run_libvirt_in_distrobox.md

Since this is the second time I've setup this distrobox and the second time this error occurs, I feel like they are linked in some way.
Comment 6 TraceyC 2025-06-17 15:52:14 UTC
Thanks for the additional information. At least there's a way this can be reproduced
It seems like we should be something detecting an invalid cache and clearing it
Comment 7 Nate Graham 2025-08-13 22:46:19 UTC
The Fontconfig cache isn't KDE's responsibility; this should be reported to the Fontconfig folks so they can look into it. Cache invalidation is one of those hard problems to solve.