SUMMARY Automatic and Manual Light/Dark theme switching loses the custom (Klassy) window decorations STEPS TO REPRODUCE 1. Go to: https://github.com/paulmcauley/klassy?tab=readme-ov-file#prebuilt 2. Download and install Klassy from OpenSUSE's Open Build Service. 3. Open Plasma's System Settings. 4. Go to: Colors & Themes -> Window Decorations. 5. Click on Klassy window decoration to select it and then on the Apply button. 6. Now wait for the time in the evening or in the morning for the automatic switch to the dark or light mode. OBSERVED RESULT Every time that the theme is automatically switching to the dark mode or the light mode, my favorite custom window decorations (in this case Klassy) are lost and they are reverted back to the default Breeze ones. EXPECTED RESULT I expect / want that the the window decorations are changed only by me, from that control panel and that Window Decorations page. I expect / want that I don't have to open that control panel, navigate to that page, select Klassy again and click on the Apply button, two times each day after each automatic switch between light and dark mode. This is too much and defeats the whole purpose of the automatic light / dark theme switch if I have again to make the same amounts of clicks as I did before when I was switching between the light and dark theme manually. SOFTWARE/OS VERSIONS Linux KDE Plasma Version: 6.5.2 KDE Frameworks Version: 6.18.0 Qt Version: 6.9.2 ADDITIONAL INFORMATION This was happening also before when I was switching between the light and / dark theme manually two times a day (for a while as I got tired of it) from the initial (Quick Settings) page and clicking on Breeze or Breeze Dark. I complained so many times about it on multiple forums until somebody told me try to try to switch the between the light and dark modes from the Colors & Themes -> Colors instead. I can confirm that switching from there between the Breeze Light and Breeze Dark colors, indeed works to switch between the light and dark mode, while keeping my custom Klassy window decorations intact, as I want them to remain. But it's again too much trouble to go there and manually fix it 2 times a day, each day! Please make this Automatic light / dark them switching keep Klassy or whatever other custom window decoration we have once set. And while you are there, it would be nice to fix also the Manual light / dark theme switching from the top of the Quick Settings page. I think that it would also be better if Breeze would be renamed to Breeze Light on the Quick Settings page, like in the Colors page. I think it's more clear to everybody if they all have "Light", "Dark", "automatic" after "Breeze". BTW, I cannot select 6.5.2 in that "Version First Reported in" drop-down as 6.5.1 is the most recent one.
And one more thing that I noticed yesterday and today. Even without passing through the evening or morning times, when the automatic dark or light theme switches, now after every restart I have to re-set (choose again) the Klassy window decorations as the control panel forgets that these are my preferences between restarts.
A possibly relevant merge request was started @ https://invent.kde.org/plasma/plasma-workspace/-/merge_requests/6064
I appreciate a lot that you are looking into this and trying to fix it! The discussion is also interesting with valid opinions from both developers. If a full or partial fix (workaround) is made, it would be great it it can be ported to the next minor release of 6.5 version. At the moment I would be happy even with a workaround that just re-sets my custom window decoration back as that's the only thing I have changed from the default Breeze, until a more proper fix is made. The next Plasma version seems pretty far away from now and even since I'm using Debian 14 (the testing repository), there will still be a 2-3 weeks or a month delay after Plasma 6.6 is released. BTW, one more surprise (unexpected thing) that I had these days, it seems that besides the day / night time switch and computer restarts, the computer suspends also trigger this. And this is a big surprise as I have never seen on Linux or on Windows something being changed (besides the date & time of course) from how I left it after a wake up from suspend. To make sure this is really the case before writing this comment, I made these reproducible steps: 1. Go to System Settings -> Window Decorations. 2. Make sure that Breeze is the one selected / used. 3. Now select another one (a custom one), like Klassy, Oxygen, Plastik, whatever others you have installed. 4. Hit Apply and suspend the computer. 5. Wake it up and enter login password. Now you should see the bug being reported here, where the custom window decorations are lost as the are probably being reverted to Breeze. And a second, new bug, where the custom window decoration that was set (chosen) before the computer has been put to sleep is wrongfully still selected, even though is not the active one being used anymore. The Apply button is also wrongfully greyed-out so you cannot re-apply it again, even though we can clearly see that the System Settings and others (Dolphin, Firefox) are not using this custom window decoration anymore. I have to select Breeze or other non-Klassy window decoration to get the Apply button back and press it of course before I can choose Klassy and press apply again. So, while fixing this problem, please keep in mind these 2 additional problems (decorations being lost for suspends & wake-ups and the decorations choosing page in System Settings not being in sync / updated with what is really happening after wake up). Thank you very much!