Uniform theme and fonts for Qt apps in GTK environments

The article needs help and is partly outdated! It seems with change on qt6 it needs some extra to set up for all qt applications. (10.01.2022)

_{By @joekamprad}

There are many ways to get a uniform look and feel working, and this is only one of those that you can choose.

The easiest way to set a uniform appearance for QT applications under GTK environments is to use Kvantum and QT5CT.

Install both packages:

sudo pacman -S kvantum-qt5 qt5ct

Both applications are required because kvantum does not allow the font settings. Therefore qt5ct is also set as an environment variable, as it works in most desktop environments or when using a window manager as a user. In some cases, e.g. when using Cinnamon, it is necessary to set the variable system-wide, because Cinnamon seems to ignore variables that are set as users. Then we set qt5ct to use the kvantum theme and set fonts inside qt5ct.

Per-user variable will be configured like so:

It seems this method is not working on XFCE4 where using ~/.profile usage is working!

Same counts for Cinnamon.

Create the needed directory

mkdir ~/.config/environment.d

and the needed config file with the needed variable:

echo "QT_QPA_PLATFORMTHEME=qt5ct" > ~/.config/environment.d/qt-theme.conf

To use ~/.profile method:

echo "export QT_QPA_PLATFORMTHEME=qt5ct" >> ~/.profile

To set this systemwide (if per user variable does not work at all):

su

echo "QT_QPA_PLATFORMTHEME=qt5ct" >> /etc/environment