Firefox seemingly very recently shipped their own titlebar controls buttons, which worsens even further the lackluster OS integration. In the screenshot you see my regular control buttons on the window to the left (default KDE Plasma theme) and the new custom buttons Firefox is serving now.
Would anyone know how to undo that change in about:config or anywhere else?
Plasma has a not so bad GTK integration which allows GTK apps to use plasma defaults. Also, GTK apps that weren't written by Gnome also have some good integration with other desktops. Only those written by Gnome are hardcoded to use only GTK styles.
If Firefox is using GTK (GTK3 to be precise) to decorate the window, even in KDE, that might be some good news for him, altough I could be wrong bc I've never used Plasma for this long (30 days tops, long ago) to get to the point of wanting to change the title bar of anything.
In Cinnamon (6.4.7) I'm using an old workaround for cases like this. It's still somewhat maintained. I can't guarantee it will work with Plasma but it doesn't hurt to try: https://aur.archlinux.org/packages/gtk3-nocsd-git
After installation, open (or create) ~/.XSession and put these two lines in it:
export GTK_CSD=0 export LD_PRELOAD=/usr/lib/libgtk3-nocsd.so.0
and reboot.
This is how I've been replacing GEdit's CSD with a normal title bar, as well as Firefox's:
Yes, but IDK of any other way to change the buttons ISOmorph was asking about. The only other way is to find and change/remove them in FF source code and recompile which needs a supercomputer to do, otherwise it may take days to recompile.
I assume he doesn't want to waste days on recompiling, so that's one way to change things. With GTK3-NOCSD (mostly + some other customizations) my title bar always looks the same way, no matter what changes Mozilla make to it: