Set all Qt app's to use GTK+ font & theme settings

13-March-2018: Updated contents & method.

Introduction

For those of us that use Desktop Environments &/or Window Managers that use GTK+ , this fix is particularly helpful.

For those such as myself that run 1080p or higher screen resolutions on largish monitors it can be quite a strain on the eyes when you can't control the size of the fonts that an application uses.

This fix makes your Qt app's use your GTK+ theme (colours & such) & your chosen font settings.

How do you do it?

1) Install qt5ct

2) Set environment variables in /etc/profile and add the following lines:

export QT_QPA_PLATFORMTHEME="qt5ct"

export QT_AUTO_SCREEN_SCALE_FACTOR=0

3) source the file by using: source /etc/profile

4) Start qt5ct

5) In the first tab Appearance choose Standard Dialogs: default (some people get crashes if they choose GTK3)

Because we used /etc/profile to set the environment variables back in step 2), after you reboot, both the user & root accounts will be able to benefit from these changes.

(If you find that certain widget styles are missing, you can see if qt5-styleplugins brings a fix for you.)

Links

This ArchWiki page goes into far more detail:

Uniform look for Qt and GTK applications [1]

Support

Following is a link to this page's forum counterpart where you can post any related feedback: [2]