Strobing flashes on github.com

[bennypowers]

Hello!

I'm a long time user. Thanks for publishing this addon.

I've noticed that on macOS 11.6.1 using Firefox 95.0b3 (64-bit), the browser's color scheme strobes back and forth on github.com.

I notice this in the browser bar, as well as in dev tools, which strobe along with the toolbar.

This only seems to happen on github.com

[toastal]

It also really drains battery and spins up my laptop fans

[toastal]

If you visit the Appearance settings, you can see the day/night themes toggle indefinitely. There are no issues on other git forges, GitLab, Sourcehut, Codeberg, etc.

[bennypowers]

Setting "Alternate color source" to anything other than "Favicon" stops the strobing, but also prevents VivaldiFox from working on most other websites

[nt1m]

This is an interesting issue:

• Github reacts to prefers-color-scheme media query updates and sets the favicon to white/black accordingly (white on dark theme, black on light theme)
• Firefox changes the prefers-color-scheme media query value based on the toolbar background (black -> dark, white -> light)

So what ends up happening here is:

• You visit Github
• initially favicon is black
• vivaldifox turns Firefox toolbar background into black to match favicon
• Firefox changes prefers-color-scheme to dark to match Firefox toolbar background
• Github turns favicon to white again (since prefers-color-scheme is now dark)
• Vivaldifox turns Firefox toolbar background into white to match favicon
• Firefox changes prefers-color-scheme to light to match Firefox toolbar background
• Github turns favicon to dark again (since prefers-color-scheme is now light)
• and so on...

A workaround here would be setting layout.css.prefers-color-scheme.content-override to 2 in about:config to restore former behavior.

Though I think the extension can do that by itself, so I might do that for the next release.

@emilio Do you know if there's something that can be done directly on the Firefox side? I think Firefox shouldn't react to per-window/dynamic theme changes (updates given by browser.theme.update()) for prefers-color-scheme imo.

[nt1m]

@bennypowers @toastal This should be fixed when Version 3.2 comes out. Thanks for reporting!

[toastal]

@nt1m Awesome. Great work!

That seems really odd to me though. I built a reactive favicon recently and did the prefers-color-scheme wholly inside the SVG's <style> tag. Are they involving JavaScript where they don't need to?