firefox: improve firefoxGnomeTheme

[jaredmontoya]

I used the gnome theme for firefox since before it was added to stylix but when I tried to migrate to the stylix implementation of it I noticed that it doesn't look the same as Nautilus or Epiphany in terms of colors.

So I opened Gnome Epiphany and tried to replicate it's look as closely as possible with my theme(catppuccin-mocha) by tweaking firefoxGnomeTheme implementation in stylix. I think new color mixes should work fine with other themes too but it would be great if someone with a different global color scheme used a color picker to compare their Gnome Epiphany to Firefox with the improved gnome theme. A slight mismatch on the blue channel is sometimes expected but all colors should be very similar.

I also added support for reader mode themeing.

---

• I certify that I have the right to submit this contribution under the MIT license
• Commit messages adhere to Stylix commit conventions
• Theming changes adhere to the Stylix style guide
• Changes have been tested locally
• Changes have been tested in testbeds
• Each commit in this PR is suitable for backport to the current stable branch

[trueNAHO]

So I opened Gnome Epiphany and tried to replicate it's look as closely as possible with my theme(catppuccin-mocha) by tweaking firefoxGnomeTheme implementation in stylix.

Thanks a lot for improving the Stylix theme. Note that I did not test this PR yet.

I think new color mixes should work fine with other themes too but it would be great if someone with a different global color scheme used a color picker to compare their Gnome Epiphany to Firefox with the improved gnome theme.

The pending PR #1857 introduces

stylix/stylix/testbed/themes/empty.nix

Line 17 in 3c286df

base16Scheme = "${pkgs.base16-schemes}/share/themes/mellow-purple.yaml";

to make it hopefully visually very obvious when something is unthemed or not adaptive enough. Try using that theme in your setup and see whether everything still looks fine.

[Flameopathic]

LGTM other than the guard on line R63. Visual differences are minor but an improvement. Tested using nix run "github:jaredmontoya/stylix/firefox-gnome#testbed:firefox-gnome-theme:light" and liked what i saw in comparison to upstream. I did not compare it to Epiphany's theming.

[0xda157]

diff LGTM