transmission-qt doesn't respect system application style

[squash0r4ng3]

What is the issue?

transmission-qt style is stuck on 'Fusion', system uses 'Breeze'.
Arch, KDE

Which application of Transmission?

Qt app on Linux, BSD, etc.

Which version of Transmission?

4.0.1

[ckerr]

Transmission doesn't do anything with Qt theming AFAIK so I don't think this is a bug in the codebase -- converting to discussion.

Could it possibly be that you have different themes set on your system for Qt5 apps vs Qt6 apps?

[squash0r4ng3]

I wasn't aware you can do that in KDE, differentiate themes between Qt5 and Qt6 apps..
Anyway, Transmission was behaving normal until the 4.0.1 update, which yesterday arrived in the repos, I was previously on the 3.0 ver, again, no complaints before..

[squash0r4ng3]

I've downgraded to 3.0 for the time being, but I still consider this a bug in the 4.0.1, it's the only app exhibiting this behavior.

[ckerr]

You're the only person to report this so far. If you're going to ignore my questions then there's not a lot of action I can take here.

[squash0r4ng3]

Well I answered your question, I don't know how to set in KDE different themes for Qt5 and Qt6 apps. To my knowledge they're all the same.

[mikedld]

This is basically the same as Qt 4 -> 5 transition, see e.g. https://stackoverflow.com/questions/17588750/how-to-build-kde-oxygen-plugin-on-qt-5. Seems that KDE has its own style plugin (platform theme) that needs to be built against Qt 6 to work its magic for Qt 6 apps, much like there's qt5ct plugin that doesn't simply work for Qt 6 and qt6ct is required.

[ckerr]

https://www.reddit.com/r/archlinux/comments/y4814a/qt_apps_not_using_current_application_style_theme/

More apps are using QT6 which is not yet supported by KDE (because they are on QT5).

https://www.reddit.com/r/kde/comments/urug5v/guide_to_a_consistent_application_style_in_plasma/ has a nice long writeup on this. Among other things, it says

There aren't yet many Qt6 apps and many can still be built with Qt5

This is true of Transmission as well; you can rebuild it with Qt5.

[squash0r4ng3]

So it's actually Plasma's 'fault'? Not being fully transitioned to Qt6?

[squash0r4ng3]

I found somewhat of a theming solution, but it requires using kvantum:

1. install kvantum, qt6ct
2. sudo nano /etc/environment and add: QT_QPA_PLATFORMTHEME=qt6ct
3. relogin, run qt6ct, select a style other than "fusion" (kvantum). I don't have brezee in that list..
   Still.. the padding for every UI element is all wrong, triple than normal.