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.



Fedora Firefox heads to updates with PGO/LTO.

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.


Firefox on Wayland update

As a next step in the Wayland effort we have new fresh Firefox packages [1] 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.

[1] Fedora 27 Fedora 28 Fedora 29

Thunderbird 60 with title bar hidden

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 🙂

Fedora Firefox – GCC/CLANG dilemma

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! 🙂