1y ago

How to correctly set QT_QPA_PLATFORMTHEME according to the WM I'm using? My script doesn't seem to work

I created this script at ~/.config/i3/scripts/qt6ct.sh to set QT_QPA_PLATFORMTHEME depending on whether I'm using Plasma or I3wm:

  bash

    
#!/bin/bash
CURRENT_DESKTOP=$(echo "$XDG_CURRENT_DESKTOP")

if [ "$CURRENT_DESKTOP" = "i3" ]; then
    export QT_QPA_PLATFORMTHEME="qt5ct"

elif [ "$CURRENT_DESKTOP" = "KDE" ]; then
    # Si estás usando Plasma (KDE), comentar la línea que exporta la variable
    unset QT_QPA_PLATFORMTHEME
else
    echo "Gestor de ventanas no es i3 ni kwin: $CURRENT_DESKTOP"
fi

echo $CURRENT_DESKTOP
echo $QT_QPA_PLATFORMTHEME

I created an autostart program and added this to my i3 config file

    
exec ~/.config/i3/scripts/qt6ct.sh
exec source ~/.config/i3/scripts/qt6ct.sh

I don't know what's wrong with it, but if I run it on a terminal, I get this (screenshot):

    
➤ ~/.config/i3/scripts/qt6ct.sh 
i3
qt5ct
➤ echo "$QT_QPA_PLATFORMTHEME"
                    
➤

So this script doesn't really export anything at all.

I have searched on every file that I thought could be exporting it as a null value (~/.bashrc, ~/.profile, ~/.bash_profile, ~/.xinitrc, ~/.Xresources, /etc/environment, /root/.profile, /root/.bashrc), but everything looks fine (no QT_QPA_PLATFORMTHEME anywhere, or is commented).

Solution

The only thing we'll need in.xprofile is sourcing the script:

    
#!/bin/bash
CURRENT_DESKTOP=$(echo "$XDG_CURRENT_DESKTOP")

if [[ "$CURRENT_DESKTOP" = "i3" ]]; then
    export QT_QPA_PLATFORMTHEME="qt5ct"
    export QT_SCREEN_SCALE_FACTORS=1.5 # 1.5
    export QT_AUTO_SCREEN_SCALE_FACTOR=0
elif [[ "$CURRENT_DESKTOP" = "KDE" ]]; then
    unset QT_QPA_PLATFORMTHEME
    export QT_AUTO_SCREEN_SCALE_FACTOR=1

else
    echo "Gestor de ventanas no es i3 ni kwin: $CURRENT_DESKTOP"
fi

echo $CURRENT_DESKTOP
echo $QT_QPA_PLATFORMTHEME
echo $QT_SCREEN_SCALE_FACTORS
echo $QT_AUTO_SCREEN_SCALE_FACTOR

LOL you're right! Yet, I am still getting no better result when changing it:

    
➤ ~/.config/i3/scripts/qt6ct.sh 
i3
qt5ct
➤ echo "$QT_QPA_PLATFORMTHEME"

➤ ~/.config/i3/scripts/qt6ct.sh 
i3
qt5ct
➤ source ~/.config/i3/scripts/qt6ct.sh 
i3
qt5ct
➤ echo "$QT_QPA_PLATFORMTHEME"
qt5ct

Ok, here are very interesting things:

I added source ~/.config/i3/scripts/qt6ct.sh at .profile, and logout. When I logged in, nothing has changed. I don't know why, since when I manually run it, it apparently changes the value of QT_QPA_PLATFORMTHEME.
After doing all of that, Qt apps doesn't seem affected at all, when I open the qt5ct application from Rofi, it keeps showing me the same warning (something like: The QT_QPA_PLATFORMTHEME environment variable has not been set (required values: qt5ct or qt6ct)).
AFTER I do all of this, if I run qt5ct or run rofi --show -drun and then select the qt5ct app, then it works just fine. The same happens with dolphin: if I run it from rofi, then it looks awful, but if I run it from the terminal, it looks great. BUT if I close the terminal and open it again, everything goes back to normal (meaning: awful).

After including source ~/.config/i3/scripts/qt6ct.sh to /etc/environment and rebooting to see if anything changed: nope. No changes, the problem persists.

7 comments

BASH is so annoying. Try fixing your spaces. On my terminal I get this:

[ "$CURRENT_DESKTOP" = "i3" ] && echo True [ "$CURRENT_DESKTOP"="i3" ] && echo True True
- LOL you're right! Yet, I am still getting no better result when changing it:
  
  ➤ ~/.config/i3/scripts/qt6ct.sh i3 qt5ct ➤ echo "$QT_QPA_PLATFORMTHEME" ➤ ~/.config/i3/scripts/qt6ct.sh i3 qt5ct ➤ source ~/.config/i3/scripts/qt6ct.sh i3 qt5ct ➤ echo "$QT_QPA_PLATFORMTHEME" qt5ct
  Ok, here are very interesting things:
  I added source ~/.config/i3/scripts/qt6ct.sh at .profile, and logout. When I logged in, nothing has changed. I don't know why, since when I manually run it, it apparently changes the value of QT_QPA_PLATFORMTHEME.
  After doing all of that, Qt apps doesn't seem affected at all, when I open the qt5ct application from Rofi, it keeps showing me the same warning (something like: The QT_QPA_PLATFORMTHEME environment variable has not been set (required values: qt5ct or qt6ct)).
  AFTER I do all of this, if I run qt5ct or run rofi --show -drun and then select the qt5ct app, then it works just fine. The same happens with dolphin: if I run it from rofi, then it looks awful, but if I run it from the terminal, it looks great. BUT if I close the terminal and open it again, everything goes back to normal (meaning: awful).
  After including source ~/.config/i3/scripts/qt6ct.sh to /etc/environment and rebooting to see if anything changed: nope. No changes, the problem persists.
  
  OK, I have neither qt apps, nor other desktops, so I'm kind of shooting in the dark. I seem to remember reading that .profile is sometimes not looked at and it's better to put in .bash_profile or even paste it into your .bashrc and see you still have the issue.