[Bug] Flatpak v8.0.3 ignores dark mode preference (COLOR_SCHEME) on XFCE/Mint with KDE runtime

[3DSpotters]

EasyEffects Version

8.0.3

What package are you using?

Flatpak (Flathub)

Distribution

Linux Mint 22.2 XFCE

Describe the bug

Hello,

I am experiencing an issue where Easy Effects (Flatpak release) always displays the light theme, regardless of the system settings. This occurs despite the recent commit 2b6097b which was intended to fix this issue.

Environment Details

• Application Version: Easy Effects v8.0.3 (Flatpak)
• Operating System: Linux Mint 22.2 XFCE
• System Theme: Mint-Y-Dark
• Flatpak Runtime (Confirmed via flatpak info): org.kde.Platform/x86_64/6.10
• Issue Severity: High (Prevents use in a dark environment)

Steps Taken / Diagnostics

I have performed extensive troubleshooting, and the issue appears to be a regression in the application's theme integration with KDE/Qt libraries when running on a GTK host (XFCE).

1. System Settings: System theme is set globally to Mint-Y-Dark.
2. Portal Check: Required XDG portals are installed and running correctly (xdg-desktop-portal and xdg-desktop-portal-xapp / -gtk).
3. Flatpak Theme Override: The issue persists even when manually forcing standard dark themes:
   • flatpak override --user --env=COLOR_SCHEME=prefer-dark com.github.wwmm.easyeffects
   • flatpak override --user --env=GTK_THEME=Adwaita:dark com.github.wwmm.easyeffects
   • flatpak override --user --env=QT_STYLE_OVERRIDE=kvantum com.github.wwmm.easyeffects (with Kvantum installed).
4. Configuration Tool Check: I have installed and configured qt5ct to use a dark color scheme and style, and the application still displays light mode.
5. Troubleshooting Conclusion: The application is ignoring the host's theme preferences, suggesting a failure in the Qt/xdg-portal integration within the v8.0.3 Flatpak package, likely due to running the KDE runtime on a GTK environment.

Could you please investigate why the theme preference is still not being applied by the application despite the fix in commit 2b6097b?

Thank you for your time.

Expected Behavior

Easy Effects in Dark Mode on Linux Mint 22.2 XFCE with System Theme: Mint-Y-Dark

Debug Log

Debug Log

Paste your log here

Additional Information

No response

[3DSpotters]

PS. It is dark, when I use Adwaita (Dark) theme, behaviour is not consistent though. When I close and then re-open Easy Effects, their background is light again...

...

[wwmm]

It does feel like a bug in the lower level libraries indeed. The only case where EasyEffects tries to set dark or light theme is the spectrum. What has nothing to do with the overall app theme.

[3DSpotters]

OK...so (with AI :) help): [Regression] Flatpak v8.0.3 (KDE Runtime) ignores dark theme, but v7 worked correctly on XFCE/Mint

Hello,

I am following up on the dark theme issue (which you identified as a lower-level library bug).

Crucially, Easy Effects v7 (Flatpak) worked perfectly with the dark theme on my system. The problem began with the upgrade to Easy Effects v8.x.

Environment Details

• Current Faulty Version: Easy Effects v8.0.3 (Flatpak)
• Previous Working Version: Easy Effects v7.x (Flatpak)
• Operating System: Linux Mint XFCE
• System Theme: Mint-Y-Dark (GTK Theme)
• Flatpak Runtime (V8): org.kde.Platform/x86_64/6.10

Problem Description

The application is stuck in light mode. This regression strongly suggests that the theme integration was broken during the switch to the modern KDE/Qt runtime for v8. The newer KDE runtime seems unable to correctly negotiate the prefer-dark setting from the GTK-based host system (Mint-Y-Dark via xdg-desktop-portal-xapp).

All previously suggested diagnostic steps have been followed (including using v8.0.3, resetting overrides, and checking portal installation).

This issue is a regression introduced when moving from the working v7 release to the v8 runtime environment.

Thank you for your assistance.

[vchernin]

I will try take a look at this. But just to clarify if it is unclear, there are two ways of doing this.

1. Use xdg desktop portal based settings for light/dark mode and color schemes.
2. Use the new (unreleased) experimental preferences option that disables the breeze theme. This then allows you to use tools like qt6ct and have them hopefully work properly.

[vchernin]

On my system (Fedora 43, GNOME 49 Wayland), dark mode with xdg desktop portal works out of the box with Easy Effects. I tried both v8.0.3 and c6e53c724a2548914c23dc5f25ae9c11e8e05288.

The accent color portal is definitely working on my system for other apps, but Easy Effects does not seem to support it. Apps like Firefox are changing accent colors as expected. I could not find any kirigami apps that reacted to accent color changes, so I asked on the kirigami matrix room for some examples.

@3DSpotters do you have any flatpak overrides being set for Easy Effects or all Flatpak apps? Any custom environment variables being set? I don't know what customizations or tricks Mint might be doing, but I would think these things would work out of the box. Especially considering the portal api was designed to work properly for sandboxed apps like Flatpak. Not to mention the fact it worked fine in Flatpak on Mint previously.

[3DSpotters]

I have performed a full cleanup as requested:

1. All Flatpak overrides were reset using flatpak override --user --reset com.github.wwmm.easyeffects.
2. The custom environment variable (QT_QPA_PLATFORMTHEME) was removed from ~/.profile and the system was restarted.
3. The application (v8.0.3) remains stuck in light mode.

This confirms that the issue is not caused by any custom user configuration or residual overrides. It is a genuine regression related to how the XFCE/Mint environment's portal (xdg-desktop-portal-xapp) communicates the dark theme preference to the KDE 6.10 Flatpak runtime.

I will now wait for further instructions regarding the experimental preference option you mentioned, or for a fix in the lower-level libraries.

Thank you for your time.

[3DSpotters]

PS. When I change the system theme to Advaita (Light) and then to Advaita (Dark) => Easy Effects gets DARK ! So I change then back to Mint-Y-Dark and.... Easy Effects remains dark (in Advaita (Dark) style)... Weird but this is my "workaround" for now.

So...I have to change the system theme to Advaita (Light) manually then to ANY dark theme (mine is Mint-Y-Dark) and now EE gets dark. But not when I start the system and EE.

[3DSpotters]

PS2. Even better: I start my system and EE, EE gets light. I change system theme to ANY light theme manually in Theme Manager and then to any DARK theme and now EE gets dark...

[vchernin]

As far as I can tell Qt/QML/Kirigami does not support the accent color portal to begin with. I opened a KDE bug: https://bugs.kde.org/show_bug.cgi?id=512260.

The color scheme (dark mode) setting is definitely supported and seems to work fine elsewhere, but I have no idea why it is so janky on your system.

[3DSpotters]

I did tinkered with /usr/share/themes/Mint-Y-Dark/gtk-3.0/gtk.css + gtk-dark.css but that is all :)

[insipidlight]

8.0.4 This isn't working for me either. Arch, Sway, native install. At first I thought it was just because I only had GTK themes installed, but now I've installed both qt5ct and qt6ct, as well as Kvantum, switched themes, and easyeffects is still stuck unchanged and in light mode unlike (I'm pretty sure) every other program I have installed

[wwmm]

I've installed both qt5ct and qt6ct, as well as Kvantum

Take a look at https://github.com/wwmm/easyeffects/issues/4332#issuecomment-3565301954. I am not sure if that works when using the Flatpak package but at least outside of it it seems to work.

[MeguMario]

I've installed both qt5ct and qt6ct, as well as Kvantum, switched themes, and easyeffects is still stuck unchanged and in light mode unlike (I'm pretty sure) every other program I have installed

I'm pretty sure those tools don't respect your light and dark settings, not to mention your theme must also have a light and dark equivalent too. If you want them to follow your system settings you must write a script to switch the theme automatically for you.

https://github.com/user-attachments/assets/58168863-c2ee-4b60-8ac7-cfadf840172b

As with any Qt app (running on Plasma included), you have to fully restart the app for the theme to apply.

[insipidlight]

@wwmm Yep qt6ct-kde works, sorry I missed that thread, guess I didn't search back far enough. It's unfortunate such a workaround is necessary

@MeguMario Thanks, but not quite sure why I would need that since I am on Sway, everything is just config files, and I don't have any light themes set and never want light mode. I have a dark theme set and have no issues, most apps use it, default to dark mode, or have a dark mode setting. Krita, which I started using recently, has nice defaults too

[MeguMario]

@MeguMario Thanks, but not quite sure why I would need that since I am on Sway, everything is just config files, and I don't have any light themes set and never want light mode.

Don't worry, if you don't need to use light mode then the above workaround is fine for set up one and done kind of situation. The later half is mostly for those that want EE and other qt app to be a little bit more integrated with their current non KDE DE while also using things like qt6ct (& kvantum) since those apps don't adjust the theme base on Light/Dark settings of their respective DE.