Every GTK desktop applications under Plasma complain about a missing window_decoration.css that should be in ~/.config/gtk-3.0/ folder.
(/usr/lib64/firefox/firefox:3086): Gtk-WARNING **: 17:10:35.184: Theme parsing error: gtk.css:2:33: Failed to import: Error opening file /home/aurelien/.config/gtk-3.0/window_decorations.css : No such file or directory.
Backup the ~/.config/gtk-3.0/ into ~/.config/gtk-3.0.bak
Systemsettings5 => Application Style => Configure GNOME/GTK Application Style...
Select Breeze theme.
Booh window_decorations.css appears in ~/.config/gtk-3.0/ but now
it is colors.css which is missing. I can import back it from previous folder backup.
So the KCM Application Style is somewhat buggy in Plasma 5.20.4
Note that by default, right after installation, every GTK app seems to use default GTK theme (Adwaita?) instead of Breeze... which is not very visually appealing.
Firefox should use Breeze theme instead of Adwaita under Plasma.
Added FOR_ERRATA8 keywords. We are in RC Freeze.
Assigning to KDE maintainers.
Created attachment 12312 [details]
Correct gtk-3.0 folder for ~/.config/ that correct all GTK errors
This attached tar.gz archive contains the correct gtk-3.0 to be placed in
~/.config/ to no longer have complain about missing files when GTK apps are running under Plasma.
Note that these errors were logged in ~/.local/share/sddm/xorg-session.log
David G has backported a potential fix in 8/core/updates_testing/kde-gtk-config-5.20.4-2.mga8.x86_64.rpm
Will test this.
Yeah,this has been tested but no, this does not fix the issue.
So, for errata.
In facts, some settings in ~/.config/gtk-3.0/ directory are carried over update from Mageia 7 to Mageia 8.
GTK3 apps will complain silently in ~/.local/share/sddm/xorg-session.log about missing files. This leads to unnecessary datas written in this file because apparently window decorations are properly applied meanwhile.
Parenthesis: That is sad is that upstream Plasma Devs fix issues in some Plasma Workspace/KDE Frameworks/KDE Applications in newer major version instead of appliyng them in already released version:
Fixes for some bugs land in Plasma Workspace 5.21 or even 5.22 now instead of current 5.20 series. And, meanwhile there is an LTS Plasma version (5.18) it has no fixes here since a while... This is Plasma rolling release...
This make us to have to backport some fixes (commit) in out current shipping version because we are a fixed version release.
But it feels good that we, Mageia, try fixing it :)
I updated Errata with link to your comment 1 for the manual fix, thanks.