Wayland/X11: How to run Firefox in mixed environment


Mixed X11/Wayland environment is a source of great annoyance when comes to running Firefox on Wayland along other X11 applications, like terminal, mail clients etc. Some X11 applications set GDK_BACKEND variable to x11 which effectively breaks Wayland applications and causes Firefox to start in X11 mode. That breaks Firefox remote protocol when Firefox searches for running instances and tries to reuse it.

When Firefox instance is already running on Wayland and you launch X11 version you get infamous “Firefox is already running” dialog due to locked Firefox profile.

Firefox 74 ships new MOZ_DBUS_REMOTE env variable and it forces Firefox on X11 to use D-Bus remote protocol as well as Wayland version does. So when X11 Firefox is launched after Wayland one with the same profile, already running Wayland instance is reused to open the link instead of the “Close Firefox” greetings.

All you need is to put this line to your ~/.bashrc file and restart your shell:

export MOZ_DBUS_REMOTE = 1

WebGL and fgx acceleration on Wayland

WebGL on Wayland running in full speed.

Firefox on Linux have suffered by poor WebGL performance for long, long time. It was given by missing general acceleration on Linux as there are always broken gfx drivers on X11, various hacks and different standards, closed source drivers and so on. Long story short – to do gfx acceleration seriously on Linux have been PITA. For instance Chrome (which supports gfx acceleration on Linux/X11) shows long list of active exceptions and workarounds listen at chrome://gpu/ page.

It’s also reason why Firefox never enabled it by default although it also implements gfx acceleration – Mozilla does not have resources to spend too much time on every broken gfx card / driver.

Fortunately situation was changed with Wayland. Working gfx acceleration is a sort of prerequisite to even start a decent Wayland compositor like Mutter or Plasma so when Firefox is launched on Wayland we can pretty much expect working GL environment. Also dmabuf is widely supported by Wayland compositor so we finally have all pieces together to build fully accelerated browser on Linux which is equal to its Windows siblings.

Firefox supports two acceleration modes – WebRender and GL compositor. WebRender is the new one and it’s superior in web content rendering. GL compositor is the former one, less advanced but it’s still faster for some scenarios where bits are heavily shifted from one side to another one – video playback and WebGL.

Both WebRender and GL compositor have implemented dmabuf back end which means textures used by WebRender/GL compositor can be created directly at GPU and shared  without copy among compositor / GPU browser processes. Such GPU memory can be in the same time mapped as EGL framebuffer so we can render WebGL frames directly to GPU memory, handle them from webgl process to chrome process and render it as a texture to a web page.

All those pieces are tied together in recent nightly where we finally have full WebGL support on Wayland and it will be shipped as Firefox 75. If you run Fedora/Gnome you can try it by yourself. Just grab latest nightly from Mozilla, enable HW acceleration, set widget.wayland-dmabuf-webgl.enabled to true at about:config, restart browser and open your favorite WebGL application like maps.google.com or WebGL samples.

Fedora Firefox team at 2019

logoI 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! 😉

Firefox & Wayland HiDPI screens

hidpiWhen 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:




Thunderbird for Wayland

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.



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