Firefox and Thunderbird not following the system's bright/dark mode

Support GNOME
1

Firefox 118 and Thunderbird 115 aren’t following the system’s dark/bright-mode on Gnome 44.5. Both apps have the “System” theme active but they stay in dark mode.

From a google search, I found out that there pre-installed extension “Legacy (GTK3) Theme Auto Switcher” should help with that, but, apparently, it doesn’t. I also tried the extension “Night Theme Switcher” but that also didn’t help.

Is this expected to work with Gnome 44.5?

2

All previous themes are unsupported on Gnome 44.5+ – Applicable themes have already been updated in the Arch/Manjaro repos. Gnome is no longer forgiving; you must replace older themes, or find a replacement compatible with Gnome 44.5+.

This is why the Legacy (GTK3) Theme Auto Switcher doesn’t work as expected. Perhaps there will be a Legacy (GTK4) Theme Auto Switcher available sometime in the future; sadly, that isn’t the case yet.

I don’t know specifically how Firefox and Thunderbird themes are affected by the above but maybe setting both to use the native theme (Gtk4) will help.

Otherwise, perhaps they are in a superposition state. :person_shrugging:

3

I found this Firefox theme, which is supposed to make Firefox compatible with GTK4: GitHub - rafaelmardojai/firefox-gnome-theme: A GNOME👣 theme for Firefox🔥

However, it doesn’t seem to follow the system’s dark/bright-setting as Firefox just stays in dark mode.

EDIT: It’s probably just a cosmetic gtk4 and not technically gtk4.

4

Indeed, and judging by the dates of certain theme files, much too early to even give Gtk4 any consideration; the disclaimer is worth noting, also.

With regard the availability of themes, I recall it was much the same during the Gtk2-Gtk3 transition. The only difference being that Gtk3 allowed some backward-compatibility with Gtk2 themes.

Gtk4 apparently does not.

I’m using one of the default themes Dark; there is also Light; and System theme – Auto in Firefox Addons. Any of those seem fine to me, however, I’m, using KDE rather than Gnome.

I imagine the first fully gtk4-compliant themes might start appearing among Firefox Addons eventually; until then, I haven’t much to suggest.

5

Ensure the about:config settings are correct

https://wiki.archlinux.org/title/Firefox#Dark_themes

and/or you can flip them manually

6

Thanks for the link! I tried both things mentioned in that section:

  • installing the package xdg-desktop-portal (xdg-desktop-portal-gnome and xdg-desktop-portal-gtk were already installed) but Firefox still doesn’t follow the system’s dark/bright mode
  • setting the config ui.systemUsesDarkTheme to 0 forces bright mode and setting it to 1 forces dark mode, but it won’t follow the actual system setting

So it seems to be broken on Gnome 44.5+?

7

Some interesting comments found at Bugzilla Port Firefox to GTK4:

Q: Now that GTK4 is officially released and also Gnome 40 is out. Is there a plan to port Firefox to GTK4?

A: We don’t have such plan yet.
A: FWIW this involves killing basically all the native widget drawing code, since that’s not allowed in GTK 4.
A: Is mentioned before there’s no gain to port Firefox to Gtk 4.0 - it does not have any benefit but adds more problems.

… and many more.

My take: Don’t expect an easy solution for custom theming anything on Gtk4 in the near future; if ever. Then again, if someone is motivated enough, perhaps there will be a hack of some kind in the future.