I think the last year was the strongest one in whole Fedora Firefox team history. We have been always contributed at Mozilla but in 2019 we finished some major outstanding projects at upstream and also ship them at Fedora.
The first finished project I’d like to mention is disabled system titlebar by default on Gnome. Firefox UI on Linux finally matches Windows/MacOS and provides similar user experience. We also implement various tweaks like styled and HiDPI titlebar button rendering and left/right button placement.
A rather small by code changes but highly impacted was gcc optimization with PGO/LTO. In cooperation with Jakub Jelinek and SuSE guys we managed to match and even slightly outperform default Mozilla Firefox binaries which are built with clang. I’m going to post more accurate numbers in some follow up post as was already published by a Czech linux magazine.
Firefox Gnome search provider is another small but useful feature we introduced last year. It’s not integrated at upstream yet because it needs an update for an upcoming async history lookup API at Firefox side but we ship it as tech preview to get more user feedback.
And then there’s our biggest project so far – Firefox with native Wayland backend. Fedora 31 ships it by default for Gnome which closes an initial developer phase and we can focus on polishing, bug fixing and adding more features now. It’s the biggest project we have been working on so far and also extends the Gtk2 to Gtk3 transition. There are also many people from and outside of Mozilla who helped with it and some of them are brand new contributors to Firefox which is awesome.
The Wayland backend is going to get more and more features in the future. We’re investigating possible advantages of DMA-BUF backend which can be used for HW accelerated video playback or direct WebGL rendering. We need to address missing Xvfb on Wayland to run tests on Wayland and build Firefox with PGO/LTO there. We’re also going to look at other Wayland compositors like Plasma and Sway to make sure Firefox works fine there – so many challenges and a lot of fun are waiting for fearless fox hackers! 😉
When comes to HiDPI screens and resolutions Firefox has always had some technical debts there. Wayland slightly improved it but we still miss clean user experience.
We tried hard to improve it and the last piece – hi-res widget rendering – landed in upcoming Firefox 68 (recently Beta). That means Firefox should be fully compatible with HiDPI screens and you shouldn’t see any glitches there.
Also Firefox 68 supports fractional scaling on Fedora 30 / Wayland which gives you more control over the screen resolution. To test it just grab Firefox Beta and try on your own, as:
While Firefox is already built with Wayland by Mozilla (thx. Mike Hommey) and also Fedora ships Firefox Wayland, Thunderbird users (me included) are missing it. But why to care about it anyway?
Wayland compositors have one great feature (at least for me), they perform screen scale independently on actual hardware. So I can set 200% desktop scale on semi HiDPI monitor (4K & 28″) and all Wayland applications work immediately at that scale without font adjustments/various DPI tweaks/etc.
So here comes the Thunderbird with Wayland backend. I generally did the package for my personal needs and you can have it too 🙂 Just get it from Fedora repos as
dnf install thunderbird-wayland
You’ll receive ‘Thunderbird on Wayland’ application entry which can be registered as default Mail at
Settings -> Details -> Default Applications
Some background info: recent stable Thunderbird (thunderbird-60.5.0) is based on Firefox ESR60 line and I backported related parts from latest stable Firefox 65. Some code couldn’t be ported and there are still issues with Wayland backend (misplaced menus on multi-monitor setup for instances) so use the bird on your own risk.
I’ve had lots of fun with GCC performance tuning at Fedora but without much results. When Mozilla switched its official builds to clang I considered that too due to difficulties with GCC PGO/LTO setup and inferior Fedora Firefox builds speed compared to Mozilla official builds.
That movement woke up GCC fans to parry that threat. Lots of arguments were brought to that ticket about clang insecurity and missing features. More importantly upstream developer Honza Hubicka found and fixed profile data generation bug (beside the others) and Jakub Jelinek worked out a GCC bug which caused Firefox crash at startup.
That effort helped me to convince GCC to behave and thanks to those two guys Fedora can offer GCC Firefox builds with PGO (Profile-Guided Optimization) and LTO (Link-Time Optimization).
The new builds are waiting for you at Koji (Fedora 28, Fedora 29). Don’t hesitate to take them for a test drive, I use Speedometer as general browser responsibility benchmark. You can also compare them with official Mozilla builds which are built with clang PGO/LTO.
As a next step in the Wayland effort we have new fresh Firefox packages  with all the goodies from Firefox 63/64 (Nightly) for you. They come with better (and fixed) rendering, v-sync support, and working HiDPI. Support for hi-res displays is not perfect yet and more fixes are on the way – thanks to Jan Horak who wrote that patches.
The builds also ship PipeWire WebRTC patch for desktop sharing created by Jan Grulich and Tomas Popela. Wayland applications are isolated from desktop and don’t have access to other windows (as X11) thus PipeWire supplies the missing functionality along the browser sandbox.
I think the rendering is generally covered now and the browser should work smoothly with Wayland backend. That’s also a reason why I make it default on Fedora 30 (Rawhide) and firefox-x11 package is available as a X11 fallback. Fedora 29 and earlier stay with default X11 backend and Wayland is provided by firefox-wayland package.
And there’s surely some work left to make Firefox perfect on Wayland – for instance correctly place popups on Gtk 3.24, update WebRender/EGL, fix KDE compositor and so on.
 Fedora 27 Fedora 28 Fedora 29
Many users like hidden system titlebar as Firefox feature although it’s not finished yet. But we’re very close and I hope to have Firefox 64 in shape that the title bar can be disabled by default at least on Gnome and matches Firefox outfit at Windows and Mac.
Thunderbird 60 was finally released for Fedora and comes with a basic version of the feature as it was introduced at Firefox 60 ESR. There’s a simple checkbox at “Customize” page at Firefox but Thunderbird is missing an easy switch.
To disable the title bar at Thunderbird 60, you need to go to system menu Edit -> Preferences and choose Advanced tab. Then click at Config Editor at page left bottom corner, open it and look for mail.tabs.drawInTitlebar. Double clik on it and your bird should be titleless 🙂
After reading Mike’s blog post about official Mozilla Firefox switch to LLVM Clang, I was wondering if we should also use that setup for official Fedora Firefox binaries.
The numbers look strong but as Honza Hubicka mentioned, Mozilla uses pretty ancient GCC6 to create binaries and it’s not very fair to compare it with up-to date LLVM Clang 6.
Also if I’m reading the mozilla bug correctly the PGO/LTO is not yet enabled for Linux, only plain optimized builds are used for now…which means the transition at Mozilla is not so far than I expected.
I also went through some Poronix tests which indicates there’s no black and white situation there although Mike claimed that LLVM Clang is generally better that GCC. But it’s possible that Firefox codebase somehow fits better LLVM Clang than GCC.
After some consideration I think we’ll stay with GCC for now and I’m going compare Fedora GCC 8 builds with the Mozilla LLVM Clang ones when there are available. Both builds can’t use -march=native so It may be an equal comparsion. Also Fedora should enable the PGO+LTO GCC setup to get the best from GCC.
[Update] I was wrong and PGO+LTO should be enabled also for Linux builds now. The numbers looks very well and I wonder if we can match them with GCC8! 🙂