Broke GTK4 Icon Theme -- how does it work and how to fix it?

pyzahl · October 7, 2025, 12:11am

I need some hints here, experimenting with Hyprland out of desparacy with all so far existing Wayland based window mangers been non capable or not providing at least tools to manage application startup window positions. I managed to get that all working with Hyprland (from source build on Debian-testing/Trixie via GitHub - JaKooLit/Debian-Hyprland: For automated installation of Hyprland on Debian 13 Trixie (Testing) and Debian SiD (Unstable) ), cool beans after some customizations (non theme related), but it’s also a wee bit experimental all over and I managed to break my gtk4 icon theme a little – while gtk3 is still looking just fine. It worked until I switched theme from default dark to light as contrasts were simply not usable….

This is what I am looking at now, particular the check buttons are shown now a funny huge circle only.

While the theme selection tool (gtk3) is looking OK.

I wonder where I can learn how this theme selection process works and how to fix it?

gwillems · October 7, 2025, 9:14am

Hi,

These icons are controlled by the CSS theme.
Do you have any theme overrides in $HOME/.config/gtk-4.0/?

pyzahl · October 7, 2025, 11:29am

Oh good to know thanks. So I guess I can simply delete anything in my own ~/.config/gtk-4.0 folder if some thing broke it and it’s been restores to defaults?

gwillems · October 7, 2025, 2:02pm

Yes. Or just rename the folder, to keep a backup of its contents, just in case.

pyzahl · October 7, 2025, 4:00pm

I’ll check later what’s actually in there!

I am currently running three major “environments” and some clashes seam to happen, also I recently got another issue with my Cursor “theme” broken in different ways on X11 and Wayland, OK on Hyprland – vs. the Gtk4 “appearance” what is broken the same way now in all environments:

Gnome on X11/Xorg: on a 4k screen, the scaling of the cursor to the correct size all sudden is broken and it’s “tiny” and only the default arrow,

Gnome on Wayland I now only get a odd white square, no cursor symbols at all ??!?!,

and Hyprland: Cursors are all normal, changing as expected on edges, etc. and are OK.

pyzahl · October 7, 2025, 6:30pm

What I found in there – I never touch it myself, but played with ngw-theme and gnome-tweak tools:

✘  Tue  7 Oct - 14:20
  ~/.config/gtk-4.0
 @pzahl
  ls -l
lrwxrwxrwx pzahl pzahl  46 B Sat Oct  4 21:27:49 2025  assets ⇒ /usr/share/themes/Materia-light/gtk-4.0/assets
lrwxrwxrwx pzahl pzahl  52 B Sat Oct  4 21:27:49 2025  gtk-dark.css ⇒ /usr/share/themes/Materia-light/gtk-4.0/gtk-dark.css
lrwxrwxrwx pzahl pzahl  47 B Sat Oct  4 21:27:49 2025  gtk.css ⇒ /usr/share/themes/Materia-light/gtk-4.0/gtk.css
.rw-rw-r-- pzahl pzahl 125 B Thu Oct  2 01:52:01 2025  gtk.css~
.rw-rw-r-- pzahl pzahl  33 B Thu Oct  2 01:46:31 2025  settings.init~

After renaming it looked OK again