Firefox: extension UI briefly shows as light mode when entering/leaving settings; lacks transition present in Chromium

[Ka1Haan]

Windows 10 22H2 laptop
Firefox 148.0.2

https://github.com/user-attachments/assets/bedae357-e073-45e5-a861-c6b39edcc81e
Recorded after reinstalling the extension and no settings and custom CSS were imported yet. Normally too fast to see, but recording slowed it down enough.

Effect remains the same even after setting the extension to dark mode. Every setting I've tried (from Windows to Firefox) that can be turned to dark mode is already dark mode. Firefox version doesn't have the moving screen transition in Chromium but I don't know if that has any bearing on the issue.

[k-ivan]

Yes, it seems that Firefox starts rendering at a very early stage, since fetching the current theme value from the settings is asynchronous. Firefox appears to apply the light background during this moment.

I need to think about it, but honestly, for now, I don’t see a way around it.