Planet Igalia WebKit

June 20, 2022

Frédéric Wang

Update on OpenType MATH fonts

I mentioned in a previous post that Igalia organized the Web Engines Hackfest 2022 last week. As usual, fonts were one of the topic discussed. Dominik Röttsches presented COLRv1 color vector fonts in Chrome and OSS (transcript) and we also settled a breakout session on Tuesday morning. Because one issue raised was the availability of OpenType MATH fonts on operating systems, I believe it’s worth giving an update on the latest status…

There are only a few fonts with an OpenType MATH table. Such fonts can be used for math layout e.g. modern TeX engines to render LaTeX, Microsoft Office to render OMML or Web engines to render MathML. Three of such fonts are interesting to consider, so I’m providing a quick overview together with screenshots generated by XeTeX from the LaTeX formula $${\sqrt{\sum_{n=1}^\infty {\frac{10}{n^4}}}} = {\int_0^\infty \frac{2x dx}{e^x-1}} = \frac{\pi^2}{3} \in {\mathbb R}$$:

Recently, Igalia has been in touch with Myles C. Maxfield who has helped with internal discussion at Apple regarding inclusion of STIX Two Math in the list of fonts on macOS. Last week he came back to us announcing it’s now the case on all the betas of macOS 13 Ventura 🎉 ! I just tested it this morning and indeed STIX Two Math is now showing up as expected in the Font Book. Here is the rendering of the last slide of my hackfest presentation in Safari 16.0:

Screenshot of a math formula rendered with STIX Two Math by Safari

Obviously, this is a good news for Chromium and Firefox too. For the former, we are preparing our MathML intent-to-ship and having decent rendering on macOS by default is important. As for the latter, we could in the future finally get rid of hardcoded tables to support the deprecated STIXGeneral set.

Another interesting platform to consider for Chromium is Android. Last week, there has been new activity on the Noto fonts bug and answers seem more encouraging now… So let’s hope we can get a proper math font on Android soon!

Finally, I’m not exactly sure about the situation on Linux and it may be different for the various distributions. STIX and Latin Modern should generally be available as system packages that can be easily installed. It would be nicer if they were pre-installed by default though…

June 20, 2022 12:00 AM

May 02, 2022

Víctor Jáquez

From gst-build to local-projects

Two years ago I wrote a blog post about using gst-build inside of WebKit SDK flatpak. Well, all that has changed. That’s the true upstream spirit.

There were two main reason for the change:

  1. Since the switch to GStreamer mono repository, gst-build has been deprecated. The mechanism in WebKit were added, basically, to allow GStreamer upstream, so keeping gst-build directory just polluted the conceptual framework.
  2. By using gst-build one could override almost any other package in WebKit SDK. For example, for developing gamepad handling in WPE I added libmanette as a GStreamer subproject, to link a modified version of the library rather than the one in flatpak. But that approach added an unneeded conceptual depth in tree.

In order to simplify these operations, by taking advantage of Meson’s subproject support directly, gst-build handling were removed and new mechanism was set in place: Local Dependencies. With local dependencies, you can add or override almost any dependency, while flatting the tree layout, by placing at the same level GStreamer and any other library. Of course, in order add dependencies, they must be built with meson.

For example, to override libsoup and GStreamer, just clone both repositories below of Tools/flatpak/local-projects/subprojects, and declare them in WEBKIT_LOCAL_DEPS environment variable:

$ export WEBKIT_SDK_LOCAL_DEPS=libsoup,gstreamer-full
$ export WEBKIT_SDK_LOCAL_DEPS_OPTIONS="-Dgstreamer-full:introspection=disabled -Dgst-plugins-good:soup=disabled"
$ build-webkit --wpe

by vjaquez at May 02, 2022 11:11 AM

April 21, 2022

WPE WebKit Blog

Happy birthday WPE!

Welcome to the new Blog section on!

Today is a special day for Igalia, especially for those colleagues that work on WebKit: Five years ago, on the 21st of April 2017, the WPE port was announced by our colleague Žan Doberšek on the WebKit mailing list.

Let’s take some time to celebrate and recap how WPE evolved from the early prototyping days to the product empowering hundreds of millions of devices worldwide today.

Celebrating WPEs 5th birthday with a cake

WPE is … what exactly?

To get everyone on the same page, let’s start by reiterating what WPE is: a WebKit port optimized for embedded devices. It allows you to embed a full-fledged Web browser engine that supports a large set of modern Web technologies into your product. WPE itself is not a Web browser such as Safari, Chrome or Firefox but contains the underlying building blocks to load, parse and render websites. To learn more about the distinction between a Web browser and a Web browser engine read our explainer.

You might ask yourself, what does “optimized for embedded devices” mean in practice? Unlike most other WebKit ports, WPE does not rely on a specific user-interface toolkit, such as Qt, GTK, Cocoa, etc., nor does it offer any integration with these kinds of toolkits. WPE WebKit is light-weight, integrates well with a variety of hardware configurations, and only requires a minimum set of APIs on your side: EGL and OpenGL ES 2.

The early days 2014 - 2017

The idea for a new WebKit port was born in 2014, as part of a collaboration between Metrological and Igalia. The goal of this collaboration was to have a WebKit port running efficiently on their set-top boxes, utilizing a modern Wayland based Linux graphics architecture. Back then, QtWebKit was popular among embedders; however, it was unmaintained and its future was unclear since Qt wanted to transition from using WebKit to Blink.

In September 2014 a group of Igalians forked the WebKitGtk port, removed all GTK toolkit dependencies, and prototyped what was necessary to achieve the goal: rendering websites without involving any of the traditional toolkits and instead utilizing a Wayland-based rendering approach.

During development it became apparent that this WebKit port is generally useful for all our customers and the community as a whole. Therefore Igalia decided to aim for an even more flexible design, where Wayland is only one of the possible backends. Our fellow Igalian Miguel Gomez reported in his late 2016 blog post about this change, and the renaming of the port: WPE appears for the first time in public.

The project’s removal of the Wayland dependency and the subsequent reorganization lead to the architecture we have today, consisting of not only the WPE port itself but a whole ecosystem of projects such as libwpe, WPEBackend-fdo, WPEBackend-rdk, etc., that together form the WPE project.

2017 - today

After months of focused engineering efforts, the downstream work was finished and Igalia was ready to announce WPE to the public on the 17th of April 2017, with the promise that Igalia will maintain the port alongside the existing WebKitGtk port. That is not a cheap bill: maintaining an upstream port is a recurring multi-million dollar investment. Just in order to keep the port itself healthy, as updates are made all around it, requires infrastructure, bots and a team of fully dedicated engineers to deal with maintenance, testing, triaging, tickets, etc. To implement new Web standards, fix related bugs or design and contribute features requires an even more considerable amount of resources.

Since then, Igalia ramped up the WPE investments and steadily advanced the port while helping customers to integrate WPE into their environments. Today WPE is healthy, runs on many platforms, and offers the most flexible browser architecture at present. Also, thanks in great part to this work, Igalia was responsible for nearly 16.5% of all commits in WebKit itself last year, helping make the larger project and ecosystem around it healthier too.

However, none of this would be possible without the commitment of many Igalians pushing the project forward every day for the past 8 years. A new People Behind WPE series will be launched soon: over the following months, the Igalians involved with WPE will introduce themselves, their area of expertise, and talk about a specific WPE related technical topic. You’ll get to know the people behind the product and a first-class technical overview of individual parts of the WPE architecture! We plan to release a new article every 3-4 weeks, so be sure to visit again soon and enjoy the upcoming People Behind WPE series.

Feel free to spread the word and make noise about WPE. Stay healthy, stay tuned!

April 21, 2022 12:00 AM

April 19, 2022

Manuel Rego

Web Engines Hackfest 2022

Once again Igalia is organizing the Web Engines Hackfest. This year the event is going to be hybrid. Though most things will happen on-site, online participation in some part of the event is going to be possible too.

Regarding dates, the hackfest will take place on June 13 & 14 in A Coruña. If you’re interested in participating, you can find more the information and the registration form at the event website:

What’s the Web Engines Hackfest?

This event started a long way back. The first edition happened in 2009 when 12 folks visited the Igalia offices in A Coruña and spent there a whole week working on WebKitGTK port. At that time, it was kind of early stages on the project and lots of work was needed, so those joint weeks were very productive to move things forward, discuss plans and implement features.

As the event grew and more people got interested, in 2014 it was renamed to Web Engines Hackfest and started to welcome people working on different web engines. This brought the opportunity for engineers of the different browsers to come together for a few days and discuss different features.

The hackfest has continued to grow and these days we welcome anyone that is somehow involved on the web platform. In this year’s event there will be people from different parts of the web platform community, from implementors and spec editors, to people interested in some particular feature.

This event has an unconference format. People attending are the ones defining the topics, and work together in breakout sessions to discuss them. They could be issues on a particular browser, generic purpose features, new ideas, even sometimes tooling demos. In addition, we always arrange a few talks as part of the hackfest. But the most important part of the event is being together with very different folks and having the chance to discuss a variety of topics with them. There are not lots of places where people from different companies and browsers join together to discuss topics. The idea of the hackfest is to provide a venue for that to happen.

2022 edition

This year we’re hosting the event in a new place, as Igalia’s office is no longer big enough to host all the people that will be attending the event. The venue is called Palexco and it’s close to the city center and just by the seaside (with views of the port). It’s a great place with lots of spaces and big rooms, so we’ll be very comfortable there. Note that we’ll have childcare service for the ones that might need it.

New venue: Palexco (picture by Jose Luis Cernadas Iglesias) New venue: Palexco (picture by Jose Luis Cernadas Iglesias)

The event is going to be 2 days this time, 13th and 14 June. Hopefully the weather will be great at that time of the year, and the folks visiting A Coruña should be able to really enjoy the trip. There are going to be lots of light hours too, sunrise is going to be around 7am and sunset past 10pm.

The registration form is still open. So far we’ve got a good amount of people registered from different companies like: Arm, Deno Land, Fission, Google, Igalia, KaiOS, Mozilla, Protocol Labs, Red Hat and Salesforce.

Arm, Google and Igalia will be sponsoring 2022 edition, and we’re really thankful for your support! If your company is also interested in sponsoring the hackfest, please contact us at

Apart from that there are going to be some talks that will be live streamed during the event. We have a Call For Papers with a deadline by the end of this month. Talks can be on-site or remote, so if you’re interested on giving one, please fill the form.

We know we’re in complex times and not everyone can attend onsite this year. We’re sorry about that, and we hope you all can make it in future editions.

Looking forward to the Web Engines Hackfest 2022!

April 19, 2022 10:00 PM

April 07, 2022

Manuel Rego

:focus-visible is shipping in Safari/WebKit

This is the final report about the work Igalia has been doing to add support for :focus-visible in WebKit. As you probably already know this work is part of the Open Prioritization campaign by Igalia that has been funded by different people and organizations. Big thanks to all of you! If you’re curious and want to know all the details you can find the previous reports on this blog.

The main highlight for this blog post is that :focus-visible has been enabled by default in WebKit (r286783). 🚀 This change was included in Safari Technology Preview 138, with its own post on the official WebKit blog. And finally reached a stable release in Safari 15.4. It’s also included in WebKitGTK 2.36 and WPE WebKit 2.36.

Open Prioritization

Let’s start from the beginning, my colleague Brian Kardell had an idea to find more diverse ways to sponsor the development of the web platform, after some internal discussion that idea materialized into what we call Open Prioritization. In summer 2020 Igalia announced Open Prioritization that intially had six different features on the list:

  • CSS lab() colors in Firefox
  • :focus-visible in WebKit/Safari
  • HTML inert in WebKit/Safari
  • Selector list arguments for :not() in Chrome
  • CSS Containment support in WebKit/Safari
  • CSS d (SVG path) support in Firefox

By that time I wrote a blog post about this effort and CSS Containment in WebKit proposal and my colleagues did the same for the rest of the contenders:

After some months :focus-visible was the winner. By the end of 2020 we launched the Open Prioritization Collective to collect funds and we started our work on the implementation side.

Last year at TPAC, Eric Meyer gave an awesome talk called Adventures in Collective Implementation, explaining the Open Prioritization effort and the ideas behind it. This presentation also explains why there’s room for external investments (like this one) in the web platform, and that all open source projects (in particular the web browser engines) always have to make decisions regarding priorities. Investing on them will help to influence those priorities and speed up the development of features you’re interested in.

It’s been quite a while since we started all this, but now :focus-visible is supported in WebKit/Safari, so we can consider that the first Open Prioritization experiment has been successful. When :focus-visible was first enabled by default in Safari Technology Preview early this year, there were lots of misunderstandings about how the development of this feature was funded. Happily Eric wrote a great blog post on the matter, explaining all the details and going over some of the ideas from his TPAC talk.

:focus-visble is shipping in in WebKit, how that happened?

In November last year, I gave a talk at CSS Conf Armenia about the status of things regarding :focus-visible implementation in WebKit. In that presentation I explained some of the open issues and why :focus-visible was not enabled by default yet in WebKit.

The main issue was that Apple was not convinced about not showing a focus indicator (focus ring) when clicking on a focusable element (like a <div tabindex="0">). However this is one of the main goals of :focus-visible itself, avoiding to get a focus indicator in such situations. As Chromium and Firefox were already doing it, and aiming to have a better interoperability between the different implementations, Apple finally accepted this behavioral change on WebKit.

Then Antti Koivisto reviewed the implementation, suggesting a few changes and spotting some issues (thanks about that). Those things were fixed and the feature was enabled by default in the codebase last December. As usual once a feature is enabled some more issues appear and they were fixed too. Including even a generic issue regarding accesskey on focusable elements, which required to add support to test accesskey on WebKit Web Platform Tests (WPT).

As part of all this work since my previous blog post we landed 9 more patches on WebKit, making a total of 36 patches for the whole feature, together with a few new WPT tests.

Buttons and :focus-visible on Safari

This topic has been mentioned in my previous posts and also in my talk. Buttons (and other form controls) are not mouse focusable in Safari (both in macOS and iOS), this means that when you click a button on Safari, the button is not focused. This behavior has the goal to match Apple platform conventions, where the focus doesn’t move when you click a button. However Safari implementation differs from the platform one, as the focus gets actually lost when you click on such elements. There are some very old issues in WebKit bugtracker about the topic (see #22261 from 2008 or #112968 from 2013 for example).

There’s a kind of coincidence related to this. Before :focus-visible existed, buttons were never showing a focus indicator in Safari after mouse click, as they are not mouse focusable. This was different in other browsers where a focus ring was showed when clicking on buttons. So while :focus-visible fixed this issue for other browsers, it didn’t change the default behavior for buttons in Safari.

However with :focus-visible implementation we introduced a problem somehow related to this. Imagine a page that has an element and when you click it, the page moves the focus via script (using HTMLElement.focus()) to a different element. Should the new focused element show a focus indicator? Or in other words, should it match :focus-visible?

ol > li::marker { content: counter(list-item) ") "; }

The answer varies depending on whether the element clicked is or not mouse focusable:

  1. If you click on a focusable element and the focus gets moved via script to a different element, the newly focused element does NOT show a focus indicator and thus it does NOT match :focus-visible.
  2. If you click on a NON focusable element and the focus gets moved via script to a different element, the newly focused element shows a focus indicator and thus it matches :focus-visible.

All implementations agree on this, and Chromium and Firefox have been shipping this behavior for more than a year without known issues so far. But a problem appeared on Safari, because unlike the rest of browsers, buttons are not mouse focusable there. So when you click a button in Safari, you go to point 2) above, and end up showing a focus indicator in the newly focused element. Web authors don’t want to show a focus indicator on that situations, and that’s something that :focus-visible is fixing through point 1) in the rest of browsers, but not in Safari (see bug #236782 for details).

We landed a workaround to fix this problem in Safari, that somehow adds an exception for buttons to follow point 1) even if they are not mouse focusable. Anyway this doesn’t look like the solution for the long term, and looking into making buttons mouse focusable on Safari might be the way to go in the future. That will also help to solve other interop issues.

And now what?

The feature is complete and shipped, but as usual there are some other things that could be done as next steps:

  • The :focus-visible specification is kind of vague and has no normative text related to when or not show a focus indicator. This was done on purpose to advance on this area and have flexibility to adapt to user needs. Anyway now that all 3 major web engines agree on the implementation, maybe there could be the chance to define this in some spec. We tried to write a PR for HTML spec when we started the work on this feature, at that time it was closed, probably it was not the right time anyway. But maybe something like that could be retaken at some point in the future.
  • WebKit Web Inspector (Dev Tools) don’t allow you to force :focus-visible yet. We sent a patch for forcing :focus-within first but some UI refactoring is needed, once that’s done adding support for :focus-visible too should be straight forward.
  • Coming back to the topic on buttons not being mouse focusable in Safari. The web platform provides a way to make elements not keyboard focusable via tabindex="-1". Why not providing a way to mark an element as not mouse focusable? Maybe there could be a proposal for a new HTML attribute that allows making elements not mouse focusable, that way websites could mimic Apple platform conventions. There are nice use cases for this, for example when you’re editing an input and then you click on some button to show some contextual information, with something like this you could avoid losing the focus from the input to carry on with your editing.


So yeah after more than a year since Igalia started working on :focus-visible in WebKit, we can now consider that this work has been complete. We can call the first Open Prioritization experiment a success, and we can celebrate together with all the people that have supported us during this achievement. 🎉

Thank you very much to all the people that sponsored this work. And also to all the people that helped reviewing patches, reporting bugs, discussing things, etc. during all this time. Without all your support we won’t be able to have made this happen. 🙏

Last but not least, we’d like to highlight how this work has helped the web platform as a whole. Now the major web browser engines have shipped :focus-visible and are using it in the default UA stylesheet. This makes tweaking the focus indicator on websites easier than ever.

April 07, 2022 10:00 PM