[Quick Tip #4] Scale QT application on HiDPI displays.
You may have noticed that some applications (qTox in my case) does scale properly even if the desktop environment is properly configured.
Indeed QT5 applications need an environment variable to define the scale to use.
To set it on Arch Linux, create a startup script in /etc/profile.d/qt-hidpi.sh :
Make it executable :
chmod +x /etc/profile.d/qt-hidpi.sh
And you are done.