question: kvantum-qt5 and kvantum-qt6 coexistence

[danixland]

Hello,
on slackware64-current, I've built kvantum-qt6 with the kvantummanager and themes, and kvantum-qt5 (only the style plugin) since I have also qt5 apps running.
Is it possible to have both coexist and use the same theme/settings? So far I see the qt6 apps taking the settings, but qt5 ones don't.

thanks a lot for your time and for this beautiful software.

[tsujan]

Is it possible to have both coexist and use the same theme/settings?

Yes, of course. You can even compile and install its Qt4 plugin alongside them.

So far I see the qt6 apps taking the settings, but qt5 ones don't.

That requires a Qt5 "platform plugin". It's a Qt plugin that recognizes Qt widget styles.

In my system and for Qt5, it's inside the folder /usr/lib/qt/plugins/platformthemes/, while that of Qt6 is inside /usr/lib/qt6/plugins/platformthemes/. I have both Qt6 and Qt5 versions of lxqt-qtplugin installed alongside each other; they provide platform plugins for Qt6 and Qt5 respectively. I'm not sure if KDE still provides a Qt5 plugin, but qt6ct and qt5ct are plugins that are usually used under non-Qt DEs (not recommended under Wayland though).

Warning: Do not use qt6ct under a Qt-based DE like KDE or LXQt! It interferes with the native plugin and causes problems.

[danixland]

thanks for your reply,
I have both qt5ct and qt6ct, both configured the exact same way, but QT_QPA_PLATFORMTHEME=qt6ct, so only qt6 apps get themed correctly.
I thought I said earlier, I'm under hyprland.

How can I make them look similar?

[tsujan]

but QT_QPA_PLATFORMTHEME=qt6ct

Then it may be a limitation in qt6ct and qt5ct plugins. You might want to ask their developer(s).

LXQt sets QT_QPA_PLATFORMTHEME to lxqt, which doesn't make a difference between Qt6 and Qt5. It's up to the user to install the Qt5 plugin(s) to make Qt5 apps inherit Qt6 settings — as they do here. I'm sure it's like that under KDE too: a single value for that EV but different plugins that can be installed alongside each other.