firefox-vertical-tabs VS qbrt

I am trying to style the tab bar for Firefox to look like Edge browser's grouped vertical tabs. I am not very good at CSS and was trying to find a similar ready styling to use or easily edit, unfortunately, I couldn't. The closest thing was Vertical tabs for Firefox, inspired by Edge but it doesn't support tab grouping. Is there any other CSS I can try?

I use this CSS code with Tab Center Reborn to get vertical tabs. Unfortunately, the last FF update broke things (again). My close/minimize/maximize buttons are white and my back/forward buttons are gone. The author usually updates the CSS code quickly, but since I'm on an OLED display, I don't want a huge white rectangle on my screen.

Firefox have got this for long thanks to custom CSS.

Then I switched to Firefox with this: https://github.com/ranmaru22/firefox-vertical-tabs

Custom css: Thnx to u/0xMii for the custom css.

I assume they meant https://en.wikipedia.org/wiki/XULRunner, which was Mozilla's spiritual predecessor to Electron.

Some abandoned modern alternatives included Positron[1][2] and qbrt[3][4].

While technically possible using Firefox's XULRunner functionality (`firefox --app app.ini` — mostly undocumented, potentially unsupported in the future), as far as I can tell, Mozilla has abandoned the Electron approach for XUL/Gecko bundling, which is a shame since Firefox itself is basically just an implementation on top of the Gecko XUL runtime.

> "[Firefox] is distributed as the combination of a Gecko XUL runtime — libxul, other shared libraries, and non-browser-specific resources like those in toolkit/ — plus a Firefox XUL application — mostly just the files in Contents/Resources/browser/, plus the 'firefox' stub executable that loads Gecko and points it at a XUL application" [5]

[1]: https://github.com/mozilla/positron

[2]: http://web.archive.org/web/20210227132731/https://mykzilla.o...

[3]: https://github.com/mozilla/qbrt

[4]: http://web.archive.org/web/20210601133844/https://mykzilla.o...

[5]: https://mykzilla.org/2017/03/08/positron-discontinued/#comme...

The issue with this is that the more deeply customisable a fork would be the further it would stray from upstream (and by extension the more dev resources it would require to maintain).

> I keep hearing the Firefox codebase isn't very modular and makes it hard to pursue such a project, and I don't doubt it. But aren't there enough of "us" out there to make a concerted effort?

There's been plenty of people making such an effort, but yeah it does appear to be "hard". If you're interested in following previous work, some relevant links:

- Overview of Myk Melez's efforts in this space https://mykzilla.org/2017/03/08/positron-discontinued/

- https://mozilla.github.io/geckoview/ (official but Android-only)

- https://github.com/mozilla/qbrt

It may also be worthwhile reading about CEF which has become something of a defacto standard: https://en.wikipedia.org/wiki/Chromium_Embedded_Framework