[HowTo] Apply custom theme to GNOME 42

Good news, everyone! GNOME 42 with Libadwaita can be themed!

Steps to reproduce:

  • Install Matcha Gtk Theme1

    pamac install matcha-gtk-theme
    
  • Set Matcha as Shell & Legacy Application theme (can also be done in Tweaks)

    gsettings set org.gnome.shell.extensions.user-theme name "Matcha-dark-sea"
    gsettings set org.gnome.desktop.interface gtk-theme "Matcha-dark-sea"
    
  • Set Matcha as Libadwaita theme

    • Backup the original
    tar -czf ~/.config/gtk-4.0.bkp.tar.gz -C ~/.config gtk-4.0
    
    • Replace the default CSS & other stuff
    cp -rL /usr/share/themes/Matcha-dark-sea/gtk-4.0 -t ~/.config
    
  • Optionally theme GDM using gdm-tools1 (an AUR (Arch User Repository) package)`:

    • Install gdm-tools
    pamac build gdm-tools
    
    • Set the GDM Login Theme
    set-gdm-theme set Matcha-dark-sea
    

I used qt5ct to configure Qt Apps & I added the following to my /etc/environment.

QT_QPA_PLATFORMTHEME=qt5ct
QT_STYLE_OVERRIDE=kvantum-dark

Also, remember to select the “Matcha-dark” theme in Kvantum Manager > Change/Delete Theme & set Qt5 Settings > Appearance > Style to “kvantum-dark”.


1 I have not tested any theme other than Matcha. But if the theme has a gtk-4.0 folder you should be golden.
2 If you choose to set the GDM Theme, there will be a graphical error in the Notification Overlay. This has been fixed & should not be a problem come the next release. Issue Link.

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