arch/pkg/de-p1st-theme/README.md

Adwaita theme - in GTK and QT

• https://wiki.archlinux.org/index.php/Uniform_look_for_Qt_and_GTK_applications#Adwaita

NOTE: This has just been tested with XFCE4 so far!

GTK

If using XFCE4 or Gnome this is the default theme. No action required.

qt5

aur sync -c adwaita-qt

Enable via env variable.

echo 'export QT_STYLE_OVERRIDE=adwaita' | sudo tee -a /etc/profile.d/98_qt5_theme.sh

qt4

aur sync -c adwaita-qt4

Then edit /etc/xdg/Trolltech.conf :

# ...
[Qt]
style=adwaita
# ...

A quote that gave me this idea

If you are using a GTK-based environment you need to configure Qt applications look and feel (using adwaita-qt qt5ct qt5-styleplugins. You can read this wiki page about it.