Both are always the same beige color, with the square button and square look to everything. Reminds me of 15 years ago, looking like some old tcl/tk or gtk1 gui apps, LOL...
I remember reading in the past that 2x versions were using QT, so in qtconfig I have it set to GTK, which I'm now assumging it should use this and theme with one of my gtk themes, but it doesn't.
I also noticed in /Browser/.config/gtk-2.0 that there is no gtk-3.0, the tbb doesn't support GTK3?
I do not know anything about theme-ing on Linux, but an Internet search reveals that this is an ongoing issue for Firefox (and therefore for Tor Browser), e.g.,
https://duckduckgo.com/?q=firefox+gtk+theme
I'm using GTK themes that provide for GTK2 & GTK3...
I can help debug if someone tells me what to do?
This is not just a gtk3 issue...
Firefox works just fine with GTK2 & GTK3, I don't see this as just a Firefox issue, but somehow Tor has self contained the browser is my feeling, so it's not able to see the themes in the system and have access to them, because if the Tor Browser was working like any other application it would theme. And Tor is a self containted unit, meaning it just sits in it's own directory and isn't even installed into the system, that means the developers have to figure out how to have access to the system for theming.
My understanding is that GTK or QT look for apps in /usr or /usr/local and if this is a portable applicaiton like Tor browser has been made into, then the developers are going to have to hack some files to gtk or qt, whichever theming they want to pick up Tor in any /path it's sitting...
Actually my bad, --prefix= can be any path /opt as example too...
Also let's PLEASE not FORGET the mouse also does not theme that I mentioned before, it always stays on the default X11 look, typical black cursor, maybe some distros name it differently, I'm not sure...
Tor Browser is only looking at the themes in the /usr/share/themes /path it is not seeing themes the end-user might place in their $HOME under /home/user/.themes
Also the mouse cursor icons are only loading from /user/share/icons instead of being able to have them load as well from the end-users $HOME /path /home/user/.icons
I hope this is now an easy fix since I found the problem...
Just create 3 files; start.sh - gtkrc-path - gtkrc
Also to make it self contained, include a theme and a mouse cursor icon and then have this information in the 3 files; (THE ONLY THING I'M NOT SURE ON, I FORGOT, IS HOW TO WRITE IT TO PICK THE USER USING THIS, UNLESS THAT CAN BE WRITTEN AS /home/$USER/)
start.sh
cd /home/foo/.tor-browser-linux64-6.0.2_en-US
./gtkrc-path
This bug should be closed as "wontfix". The GTK style is used for web page content rendering and can be used for fingerprinting. It affects the size of various GUI controls.
This is simply looking at the 'Differences' and seeing how you compare.
So if everyone using the Tor browser for Linux uses a default theme added to Tor, then there is no fingerprint issue, this only comes into play when you Stand Out from the Crowd!
ALSO you and the Tor team need to understand, or at least convey the understanding that you know about computer Security, Privacy & Anonymity, because talking about implementing something like this, or even a single person using this is ridiculous in those terms, and doesn't convey this understanding!
An experienced user, that applies security and privacy on their end doesn't need to worry about browser fingerprinting, it's utter nonsense!
So, again, Tor applying a theme for Tor Browser bundle that everyone on the planet is using, is not a fingerprinting issue!