gtk4 theme stopped working altogether

[RiedleroD]

This started a month ago, but I only had time to debug it now. sorry!

When starting any gtk4 application (tested with door-knocker and easyeffects edit: easyeffects has switched to Qt6 since) with any Arc theme enabled, it will spew the following error twice:

Gtk-WARNING **: 13:18:22.265: Theme parser error: gtk.css:1:1-66: Failed to import: The resource at “/org/gnome/arc-theme/gtk-main-dark.css” does not exist

looking in gtk.css reveals the following statement: @import url("resource:///org/gnome/arc-theme/gtk-main-dark.css"); which seems to be correct. as I understand it, this resource should be loaded from gtk.gresource in the same folder. using gresource list on that file confirms that it indeed contains the requested file.

I have honestly zero idea why this stopped working or how to fix it. Mostly because I cannot find any documentation for this stuff. I assume the gresource file is supposed to be auto-loaded (somehow) but isn't because gtk4 changed how autoloading works (for some reason). pure speculation tho, again, no idea.

I will continue to try debugging this, but I doubt I can get to any meaningful conclusion.

Incorrect	Correct	Default Theme

[RiedleroD]

oh I just realized: it does not work if the theme is set via envvar (GTK_THEME=Arc, errors as reported above) but it does work correctly if GTK_THEME is an empty string and the theme is set via gsettings. what the hell

this is especially surprising, as the tested applications are libadwaita-based and therefore shouldn't even attempt to load the theme without GTK_THEME forcing it

[CarterSnich]

oh I just realized: it does not work if the theme is set via envvar (GTK_THEME=Arc, errors as reported above) but it does work correctly if GTK_THEME is unset or empty and the theme is set via gsettings. what the hell

this is especially surprising, as the tested applications are libadwaita-based and therefore shouldn't even attempt to load the theme without GTK_THEME forcing it

So, the theme is just supposed to look black than kinda dark-blue unlike how Thunar look likeon the screenshot below?

I thought the theme wasn't working because of the colors on apps like File-Roller, Gear Lever, etc. is not the same like on Thunar. I also tried using GTK_THEME, but I'm also getting the same theme parser errors.

what's the point of me blurring if I missed some

[RiedleroD]

no, sorry. I attached the incorrect screenshot. will fix in a sec

edit: fixed

[asrieldashie]

Likely the same issue?
In my case was Winetricks and several flatpak apps, they would end up not rendering any widgets nor even background

However, changing the gtk-theme-name (regardless whatever the input was) in the gtk debug tool would immediately bring it back (in current session):

Passing GTK_THEME= while launching it would also make it apply, but having it as an env just makes it fall back to default theme.
Fedora 43 with Cinnamon desktop.

[CarterSnich]

Is this the correct color? I tried to run, enforced with dark theme: GTK_THEME=Arc-Dark:dark file-roller

[Swarthe]

Same issue, un-setting GTK_THEME and setting color-scheme and gtk-theme with gsettings works as expected, althought I get this warning:

(baobab:2041564): Adwaita-WARNING **: 01:16:04.418: Using GtkSettings:gtk-application-prefer-dark-theme with libadwaita is unsupported. Please use AdwStyleManager:color-scheme instead.

However, running a GTK-4 program through Rofi (application launcher) loads the default Adwaita dark theme for some reason (second image).

I also tried settings gtk-key-theme and gtk-color-scheme to no effect.