On top of those things, I’ve been also presenting our work around WebKit in different venues, such as in the Embedded Open Source Summit or in the Embedded Recipes conference, for instance. Of course, that included presenting our work in the WebKit community as part of the WebKit Contributors Meeting, a small and technically focused event that happens every year, normally around the Bay Area (California). That’s often a pretty dense presentation where, over the course of 30-40 minutes, we go through all the main areas that we at Igalia contribute to in WebKit, trying to summarize our main contributions in the previous 12 months. This includes work not just from the WebKit team, but also from other ones such as our Web Platform, Compilers or Multimedia teams.

So far I did that a couple of times only, both last year on October 24rth as well as this year, just a couple of weeks ago in the latest instance of the WebKit Contributors meeting. I believe the session was interesting and informative, but unfortunately it does not get recorded so this time I thought I’d write a blog post to make it more widely accessible to people not attending that event.

This is a long read, so maybe grab a cup of your favorite beverage first…

Igalia and WebKit

This means that, while WebKitGTK is the go-to solution to embed Web content in GTK applications (e.g. GNOME Web/Epiphany, Evolution), and therefore integrates well with that graphical toolkit, WPE does not even provide a graphical toolkit since its main goal is to be able to run well on embedded devices that often don’t even have a lot of memory or processing power, or not even the usual mechanisms for I/O that we are used to in desktop computers. This is why WPE’s architecture is designed with flexibility in mind with a backends-based architecture, why it aims for using as few resources as possible, and why it tries to depend on as few libraries as possible, so you can integrate it virtually in any kind of embedded Linux platform.

Besides that port-specific work, which is what our WebKit and Multimedia teams focus a lot of their effort on, we also contribute at a different level in the port-agnostic parts of WebKit, mostly around the area of Web standards (e.g. contributing to Web specifications and to implement them) and the Javascript engine. This work is carried out by our Web Platform and Compilers team, which tirelessly contribute to the different parts of WebCore and JavaScriptCore that affect not just the WebKitGTK and WPE ports, but also the rest of them to a bigger or smaller degree.

Last but not least, we also devote a considerable amount of our time to other topics such as accessibility, performance, bug fixing, QA... and also to make sure WebKit works well on 32-bit devices, which is an important thing for a lot of WPE users out there.

Who are our users?

Port users: this category would include anyone that writes a product directly against the port’s API, that is, apps such as a desktop Web browser or embedded systems that rely on a fullscreen Web view to render its Web-based content (e.g. digital signage systems).

Platform providers: in this category we would have developers that build frameworks with one of the Linux ports at its core, so that people relying on such frameworks can leverage the power of the Web without having to directly interface with the port’s API. RDK could be a good example of this use case, with WPE at the core of the so-called Thunder plugin (previously known as WPEFramework).

Web developers: of course, Web developers willing to develop and test their applications against our ports need to be considered here too, as they come with a different set of needs that need to be fulfilled, beyond rendering their Web content (e.g. using the Web Inspector).

End users: And finally, the end user is the last piece of the puzzle we need to pay attention to, as that’s what makes all this effort a task worth undertaking, even if most of them most likely don’t need what WebKit is, which is perfectly fine :-)

We like to make this distinction of 4 possible types of users explicit because we think it's important to understand the complexity of the amount of use cases and the diversity of potential users and customers we need to provide service for, which is behind our decisions and the way we prioritize our work.

Strategic goals

With WPE, it is very important to be able to run the engine in small embedded devices, and that requires good performance and being efficient in multiple hardware architectures, as well as great flexibility for specific hardware, which is why we provided WPE with a backend-based architecture, and reduced dependencies to a minimum.

Then, it is also important that the QA Infrastructure is good enough to keep the releases working and with good quality, which is why I regularly maintain, evolve and keep an eye on the EWS and post-commit bots that keep WebKitGTK and WPE building, running and passing the tens of thousands of tests that we need to check continuously, to ensure we don’t regress (or that we catch issues soon enough, when there’s a problem). Then of course it’s also important to keep doing security releases, making sure that we release stable versions with fixes to the different CVEs reported as soon as possible.

Finally, we also make sure that we keep evolving our tooling as much as possible (see for instance the release of the new SDK earlier this year), as well as improving the documentation for both ports.

Last, all this effort would not be possible if not because we also consider a goal of us to maintain an efficient collaboration with the rest of the WebKit community in different ways, from making sure we re-use and contribute to other ports as much code as possible, to making sure we communicate well in all the forums available (e.g. Slack, mailing list, annual meeting).

Contributions to WebKit in numbers

With that out of the way, it’s interesting to confirm that once again we are still the 2nd biggest contributor to WebKit after Apple, with ~13% of the commits landed in this past 12-month period. More specifically, we landed 2027 patches out of the 15617 ones that took place during the past year, only surpassed by Apple and their 12456 commits. The remaining 1134 patches were landed mostly by Sony, followed by RedHat and several other contributors.

Now, if we remove Apple from the picture, we can observe how this year our contributions represented ~64% of all the non-Apple commits, a figure that grew about ~11% compared to the past year. This confirms once again our commitment to WebKit, a project we started contributing about 14 years ago already, and where we have been systematically being the 2nd top contributor for a while now.

Main areas of work

Web Platform

This feature allows skipping painting and rendering of off-screen sections, particularly useful to avoid the browser spending time rendering parts in large pages, as content outside of the view doesn’t get rendered until it gets visible.

We completed the implementation and it’s now enabled by default.

Navigation API

This is a new API to manage browser navigation actions and examine history, which we started working on in the past cycle. There’s been a lot of work happening here and, while it’s not finished yet, the current plan is that Apple will continue working on that in the next months.

hasUAVisualTransition

This is an attribute of the NavigateEvent interface, which is meant to be True if the User Agent has performed a visual transition before a navigation event. It was something that we have also finished implementing and is now also enabled by default.

Secure Curves in the Web Cryptography API

In this case, we worked on fixing several Web Interop related issues, as well as on increasing test coverage within the Web Platform Tests (WPT) test suites.

On top of that we also moved the X25519 feature to the “prepare to ship” stage.

Trusted Types

This work is related to reducing DOM-based XSS attacks. Here we finished the implementation and this is now pending to be enabled by default.

MathML

We continued working on the MathML specification by working on the support for padding, border and margin, as well as by increasing the WPT score by ~5%.

The plan for next year is to continue working on core features and improve the interaction with CSS.

Cross-root ARIA

Web components have accessibility-related issues with native Shadow DOM as you cannot reference elements with ARIA attributes across boundaries. We haven’t worked on this in this period, but the plan is to work in the next months on implementing the Reference Target proposal to solve those issues.

Canvas Formatted Text

Canvas has not a solution to add formatted and multi-line text, so we would like to also work on exploring and prototyping the Canvas Place Element proposal in WebKit, which allows better text in canvas and more extended features.

Graphics

If you have followed the latest developments, you probably already know that the Linux WebKit ports (i.e. WebKitGTK and WPE) have moved from Cairo to Skia for their 2D rendering library, which was a pretty big and important decision taken after a long time trying different approaches and experiments (including developing our own HW-accelerated 2D rendering library!), as well as running several tests and measuring results in different benchmarks.

The results in the end were pretty overwhelming and we decided to give Skia a go, and we are happy to say that, as of today, the migration has been completed: we covered all the use cases in Cairo, achieving feature parity, and we are now working on implementing new features and improvements built on top of Skia (e.g. GPU-based 2D rendering).

On top of that, Skia is now the default backend for WebKitGTK and WPE since 2.46.0, released on September 17th, so if you’re building a recent version of those ports you’ll be already using Skia as their 2D rendering backend. Note that Skia is using its GPU-based backend only on desktop environments, on embedded devices the situation is trickier and for now the default is the CPU-based Skia backend, but we are actively working to narrow the gap and to enable GPU-based rendering also on embedded.

Architecture changes with buffer sharing APIs (DMABuf)

We did a lot of work here, such as a big refactoring of the fencing system to control the access to the buffers, or the continued work towards integrating with Apple’s DisplayLink infrastructure.

On top of that, we also enabled more efficient composition using damaging information, so that we don’t need to pass that much information to the compositor, which would slow the CPU down.

Enablement of the GPUProcess

On this front, we enabled by default the compilation for WebGL rendering using the GPU process, and we are currently working in performance review and enabling it for other types of rendering.

New SVG engine (LBSE: Layer-Based SVG Engine)

If you are not familiar with this, here the idea is to make sure that we reuse the graphics pipeline used for HTML and CSS rendering, and use it also for SVG, instead of having its own pipeline. This means, among other things, that SVG layers will be supported as a 1st-class citizen in the engine, enabling HW-accelerated animations, as well as support for 3D transformations for individual SVG elements.

On this front, on this cycle we added support for the missing features in the LBSE, namely:

• Implemented support for gradients & patterns (applicable to both fill and stroke)
• Implemented support for clipping & masking (for all shapes/text)
• Implemented support for markers
• Helped review implementation of SVG filters (done by Apple)

General overhaul of the graphics pipeline, touching different areas (WIP):

On top of everything else commented above, we also worked on a general refactor and simplification of the graphics pipeline. For instance, we have been working on the removal of the Nicosia layer now that we are not planning to have multiple rendering implementations, among other things.

Multimedia

We merged the DMABuf-based sink for HW-accelerated video in the GL-based GStreamer sink.

WebCodecs backend

We completed the implementation of  audio/video encoding and decoding, and this is now enabled by default in 2.46. As for the next steps, we plan to keep working on the integration of WebCodecs with WebGL and WebAudio.

GStreamer-based WebRTC backends

We continued working on GstWebRTC, bringing it to a point where it can be used in production in some specific use cases, and we will still be working on this in the next months.

Other

Besides the points above, we also added an optional text-to-speech backend based on libspiel to the development branch, and worked on general maintenance around the support for Media Source Extensions (MSE) and Encrypted Media Extensions (EME), which are crucial for the use case of WPE running in set-top-boxes, and is a permanent task we will continue to work on in the next months.

JavaScriptCore

A lot of work happened around 32-bit support in JavaScriptCore, especially around WebAssembly (WASM): we ported the WASM BBQJIT and ported/enabled concurrent JIT support, and we also completed 80% of the implementation for the OMG optimization level of WASM, which we plan to finish in the next months. If you are unfamiliar with what the OMG and BBQ optimization tiers in WASM are, I’d recommend you to take a look at this article in webkit.org: "Assembling WebAssembly".

We also contributed to the JIT-less WASM, which is very useful for embedded systems that can’t support JIT for security or memory related constraints, and also did some work on the In-Place Interpreter (IPInt), which is a new version of the WASM Low-level interpreter (LLInt) that uses less memory and executes WASM bytecode directly without translating it to LLInt bytecode  (and should therefore be faster to execute).

Last, we also contributed most of the implementation for the WASM GC, with the exception of some Kotlin tests.

As for the next few months, we plan to investigate and optimize heap/JIT memory usage in 32-bit, as well as to finish several other improvements on ARMv7 (e.g. IPInt).

New WPE API

A lot of effort happened this year along these lines, including the fact that we finally upstreamed and shipped its initial implementation with WPE 2.44, back in the first half of the year. Now, while we recommend users to give it a try and report feedback as much as possible, this new API is still not set in stone, with regular development still ongoing, so if you have the chance to try it out and share your experience, comments are welcome!

Besides shipping its initial implementation, we also added support for external platforms, so that other ones can be loaded beyond the Wayland, DRM and “headless” ones, which are the default platforms already included with WPE itself. This means for instance that a GTK4 platform, or another one for RDK could be easily used with WPE.

Then of course a lot of API additions were included in the new API in the latest months:

• Screens management API:  API to handle different screens, ask the display for the list of screens with their device scale factor, refresh rate, geometry...
• Top level management API: This API allows a greater degree of control, for instance by allowing more than one WebView for the same top level, as well as allowing to retrieve properties such as size, scale or state (i.e. full screen, maximized...).
• Maximized and minimized windows API: API to maximize/minimize a top level and monitor its state. mainly used by WebDriver.
• Preferred DMA-BUF formats API: enables asking the platform (compositor or DRM) for the list of preferred formats and their intended use (scanout/rendering).
• Input methods API: allows platforms to provide an implementation to handle input events (e.g. virtual keyboard, autocompletion, auto correction...).
• Gestures API: API to handle gestures (e.g. tap, drag).
• Buffer damaging: WebKit generates information about the areas of the buffer that actually changed and we pass that to DRM or the compositor to optimize painting.
• Pointer lock API: allows the WebView to lock the pointer so that the movement of the pointing device (e.g. mouse) can be used for a different purpose (e.g. first-person shooters).

With all this done so far, the plan now is to complete the new WPE API, with a focus on the Settings API and accessibility support, write API tests and documentation, and then also add an external platform to support GTK4. This is done on a best-effort basis, so there’s no specific release date.

WebKit on Android

In case you’re not familiar with this, the idea here is to provide a WebKit-based alternative to the Chromium-based Web view on Android devices, in a way that leverages HW acceleration when possible and that it integrates natively (and nicely) with the several Android subsystems, and of course with Android’s native mainloop. Note that this is an experimental project for now, so don’t expect production-ready quality quite yet, but hopefully something that can be used to start experimenting with selected use cases.

If you’re adventurous enough, you can already try the APKs yourself from the releases page in GitHub at https://github.com/Igalia/wpe-android/releases.

Anyway, as for the changes that happened in the past 12 months, here is a summary:

• Updated WPE Android to WPE 2.46 and NDK 27 LTS
• Added support for WebDriver and included WPT test suites
• Added support for instrumentation tests, and integrated with the GitHub CI
• Added support for the remote Web inspector, very useful for debugging
• Enabled the Skia backend, bringing HW-accelerated 2D rendering to WebKit on Android
• Implemented prompt delegates, allowing implementing things such as alert dialogs
• Implemented WPEView client interfaces, allowing responding to things such as HTTP errors
• Packaged a WPE-based Android WebView in its own library and published in Maven Central. This is a massive improvement as now apps can use WPE Android by simply referencing the library from the gradle files, no need to build everything on their own.
• Other changes: enabled HTTP/2 support (via the migration to libsoup3), added support for the device scale factor, improved the virtual on-screen keyboard, general bug fixing...

As for the future, we’ll focus on stabilization and regular maintenance for now, and then we’d like to work towards achieving production-ready quality for specific cases if possible.

Quality Assurance

• Fixed a lot of API tests failures in the bots that were limiting our test coverage.
• Fixed lots of assertions-related crashes in the bots, which were slowing down the bots as well as causing other types of issues, such as bots exiting early due too many failures.
• Enabled assertions in the release bots, which will help prevent crashes in the future, as well as with making our debug bots healthier.
• Moved all the WebKitGTK and WPE bots to building now with Skia instead of Cairo. This means that all the bots running tests are now using Skia, and there's only one bot still using Cairo to make sure that the compilation is not broken, but that bot does not run tests.
• Moved all the WebKitGTK bots to use GTK4 by default. As with the move to Skia, all the WebKit bots running tests now use GTK4 and the only one remaining building with GTK3 does not run tests, it only makes sure we don't break the GTK3 compilation for now.
• Working on moving all the bots to use the new SDK. This is still work in progress and will likely be completed during 2025 as it's needed to implement several changes in the infrastructure that will take some time.
• General gardening and bot maintenance

Security

As usual, we kept aligning releases for WebKitGTK and WPE, with both of them happening at the same time (see https://webkitgtk.org/releases and https://wpewebkit.org/release), and then also publishing WebKit Security Advisories (WSA) when necessary, both for WebKitGTK and for WPE.

Last, we also shortened the time before including security fixes in stable releases this year, and we have removed support for libsoup2 from WPE, as that library is no longer maintained.

Tooling & Documentation

This new SDK is regularly maintained and currently runs on Ubuntu 24.04 LTS with GCC 14 & Clang 18. It has been made public on GitHub and announced to the public in May 2024 in Patrick’s blog, and is now the officially recommended way of building WebKitGTK and WPE.

As for documentation, we didn’t do as much as we would have liked here, but we still landed a few contributions in docs.webkit.org, mostly related to WebKitGTK (e.g. Releases and Versioning, Security Updates, Multimedia). We plan to do more on this regard in the next months, though, mostly by writing/publishing more documentation and perhaps also some tutorials.

Final thoughts

In any case, what’s clear it’s that the next months are probably going to be quite interesting as well with all the work that’s already going on in WebKit and its Linux ports, so it’s possible that in 12 months from now I might be writing an equally long essay. We’ll see.

Thanks for reading!

Setting up an environment for cross-compiling WebKit2GTK+ for ARM

Of course, I know for a fact that many people use local recipes to cross-compile WebKit2GTK+ for ARM (or simply build in the target machine, which usually takes a looong time), but those are usually ad-hoc things and hard to reproduce environments locally (or at least hard for me) and, even worse, often bound to downstream projects, so I thought it would be nice to try to have something tested with upstream WebKit2GTK+ and publish it on trac.webkit.org,

So I spent some time working on this with the idea of producing some step-by-step instructions including how to create a reproducible environment from scratch and, after some inefficient flirting with a VM-based approach (which turned out to be insanely slow), I finally settled on creating a chroot + provisioning it with a simple bootstrap script + using a simple CMake Toolchain file, and that worked quite well for me.

In my fast desktop machine I can now get a full build of WebKit2GTK+ 2.14 (or trunk) in less than 1 hour, which is pretty much a productivity bump if you compare it to the approximately 18h that takes if I build it natively in the target ARM device I have :-)

Of course, I’ve referenced this documentation in trac.webkit.org, but if you want to skip that and go directly to it, I’m hosting it in a git repository here: github.com/mariospr/webkit2gtk-ARM.

Note that I’m not a CMake expert (nor even close) so the toolchain file is far from perfect, but it definitely does the job with both the 2.12.x and 2.14.x releases as well as with the trunk, so hopefully it will be useful as well for someone else out there.

Last, I want to thanks the organizers of this event for making it possible once again (and congrats to Igalia, which just turned 15 years old!) as well as to my employer for supporting me attending the hackfest, even if I could not make it in person this time.

It will be different for me this time, though, as now my main focus won’t be on accessibility (yet I’m happy to help with that, too), but on fixing a few issues related to the WebKit2GTK+ API layer that I found while working on our platform (Endless OS), mostly related to its implementation of accelerated compositing.

Besides that, I’m particularly curious about seeing how the hackfest looks like now that it has broaden its scope to include other web engines, and I’m also quite happy to know that I’ll be visiting my home town and meeting my old colleagues and friends from Igalia for a few days, once again.

Last, I’d like to thank my employer for sponsoring this trip, as well as Igalia for organizing this event, one more time.

See you in Coruña!

The following CMake snippet was not properly recognizing my 32bit chroot:

string(TOLOWER ${CMAKE_HOST_SYSTEM_PROCESSOR} LOWERCASE_CMAKE_HOST_SYSTEM_PROCESSOR)
if (CMAKE_COMPILER_IS_GNUCXX AND "${LOWERCASE_CMAKE_HOST_SYSTEM_PROCESSOR}" MATCHES "(i[3-6]86|x86)$")
    ADD_TARGET_PROPERTIES(WebCore COMPILE_FLAGS "-fno-tree-sra")
endif ()

After some investigation, I found out that CMAKE_HOST_SYSTEM_PROCESSOR relies on the output of uname to determine the type of the CPU, and this what I was getting if I ran it myself:

(debian32-chroot)mario:~ $ uname -a
Linux moucho 4.0.6-300.fc22.x86_64 #1 SMP Tue Jun 23 13:58:53 UTC 2015
x86_64 x86_64 x86_64 GNU/Linux

Let’s avoid nasty comments about the stupid name of my machine (I’m sure everyone else uses clever names instead), and see what was there: x86_64.

That looked wrong to me, so I googled a bit to see what others did about this and, besides finding all sorts of crazy hacks around, I found that in my case the solution was pretty simple just because I am using schroot, a great tool that makes life easier when working with chrooted environments.

Because of that, all I would have to do would be to specify personality=linux32 in the configuration file for my chrooted environment and that’s it. Just by doing that and re-entering in the “jail”, the output would be much saner now:

(debian32-chroot)mario:~ $ uname -a
Linux moucho 4.0.6-300.fc22.x86_64 #1 SMP Tue Jun 23 13:58:53 UTC 2015
i686 i686 i686 GNU/Linux

And of course, WebKitGTK+ would now recognize and use the right CPU type in the snippet above and I could “relax” again while seeing WebKit building again.

Now, for extra reference, this is the content of my schroot configuration file:

$ cat /etc/schroot/chroot.d/00debian32-chroot
[debian32-chroot]
description=Debian-like chroot (32 bit) 
type=directory
directory=/schroot/debian32/
users=mario
groups=mario
root-users=mario
personality=linux32

That is all, hope somebody else will find this useful. It certainly saved my day!

As for me, I flew there to work mainly on accessibility related issues, making the most of the fact that both Joanie (Orca maintainer) and Piñeiro (ATK maintainer) would be there too, so it should be possible to make things happen faster, specially discussion-wise.

And turns out that, even if I feel like I could have achieved more than what I actually did (as usual), I believe we did quite well in the end: we discussed and clarified things that were blocking the mapping of new WAI-ARIA roles in WebKitGTK+, we got rid of a bunch of WebKit1-specific unit tests (Joanie converted them into nice layout tests that will be run by WebKit2GTK+ too), we got a few new roles in ATK to be able to better map things from the web world and and we fixed a couple of issues in the way too.

Of course, not everything has been rainbows and unicorns, as it seems that one of the patches I landed broke the inspector for WebKit2GTK+ (sorry Gustavo!). Fortunately, that one has been rolled out already and I hope I will be able to get back to it soon (next week?) to provide a better patch for that without causing any problem. Fingers crossed.

In the other hand, my mate Brian Holt joined us for three days too and, despite of being his first time in the hackfest, he got integrated pretty quickly with other hackers, teaming up to collaborate in the big boost that the network process & multiple web processes items have went through during the event. And not only that, he also managed to give a boost to his last patch to provide automatic memory leak detection in WebKitGTK+, which I’m sure it will be a great tool once it’s finished and integrated upstream.

Anyway, if you want more details on those topics, or anything else, please check out the blog posts that other hackers have been posting these days, specially Carlos’s blog post, which is quite extensive and detailed.

Of course, I would like to thank the main sponsors Igalia and the GNOME Foundation for making this thing happen again, and to my employer Samsung  for helping as well by paying our trips and accommodation, as well as the snacks and the coffee that helped us stay alive and get fatter during the hackfest.

Last, I would like to mention (in case anyone reading this wondered) that it has indeed felt a bit strange to go the city where I used to live in and stay in a hotel, not to mention going to the office where I used to work in and hang around it as a visitor. However, both my former city and my former colleagues somehow ensured that I felt as “at home” once again, and so I can’t do anything about it but feeling enormously grateful for that.

Thank you all, and see you next year!

And finally, I’m really happy to say that such a task is complete once and for all, meaning that now those functions should work as well or as bad on WebKit2GTK+ as they do in WebKitGTK+, so the weird behaviour described in bug 73433 is no longer an issue. You can check I’m not lying by just taking a look to the commit that removed both all trace of Pango and GAIL in the code, as well as and the one that removed the GAIL dependency from the build system. And if you want more detail, just feel free to check the whole dependency tree in WebKit’s bugzilla.

This task has been an interesting challenge for me indeed, and not only because it was one of the biggest accessibility related tasks I’ve worked on in WebKitGTK+ since late 2012 (so I needed to get my brain trained again on it), but also because reimplementing these functions forced me to dive into text editing and accessibility code in WebCore as I never did before. And it’s so cool to see how, despite of having to deal eventually with the frustrating feeling of hitting my head against a wall, at the end of the day it all resulted on a nice set of patches that do the work and help advance the state of the ATK based accessibility layer in WebKitGTK+ forward.

Anyway, even though that is probably the thing that motivated me to write this blog post, that was not the only thing that I did since GUADEC (which has been a blast, by the way):

On the personal side, I’ve spent two lovely weeks in Spain on holidays, which was the biggest period of time I’ve been outside of the UK since I arrived here, and had  an amazing time there just “doing nothing”(tm) but lying around on the beach and seeing the grass grow. And there is not much grass there anywhere, so you can imagine how stressful that life was… it was great.

In the other hand, on the professional side, I’d say that one of the other big things that happened to me lately was that I finally became accepted as a WebKit reviewer, meaning that now I can not only help breaking the Web, but also authorize others to do it so. And while agree that might be fun in some way, it probably would not be very cool, so forgive me if I try instead to do my best to help get exactly the opposite result: make things work better.

And truth to be told, this “upgrade” came just with perfect timing, since these days quite some work is being done in the accessibility layer for both the WebKitGTK+ and the WebKitEFL ports thanks also to my mates Denis Nomiyama, Anton Obzhirov, Brian Holt and Krzysztof Czech from Samsung, and that work would ideally need to be reviewed by someone familiar with the ATK/AT-SPI based accessibility stack. And while I’m still by far not the most knowledgeable person in the world when it comes to those topics, I believe I might have a fairly well knowledge about it anyway, so I assume (and hope) that my reviews will certainly add value and help with those specific pieces of work.

And as a nice plus, now I can finally “return the favour” to the only accessibility reviewer WebKit had until now (Chris Fleizach) by helping reviewing his patches as well, in a similar fashion to what he has been tirelessly doing for me for the last 3 years and a half. Yay!

To finish , I’d like to get back again to the original topic of this post and say a big “thank you” to everyone who helped me along the way with the removal of Pango and GAIL from the ATK specific code. Special thanks go to those who spend time performing the code reviews, as it’s the case of Martin, Gustavo and Chris. I wouldn’t be writing this post otherwise.

Thanks!

And the reason why it was not initially in my plans was mainly because I’ve been already through quite some changes during these past months year, and my family just came over to the UK two months ago. This means that, even I already arrived by the beginning of the year, we just started to settle here as a family a few weeks ago. So in that context, I didn’t feel like leaving them alone for one week already now, it definitely would look like a “wrong management of priorities” to me.

However, it turns out that my wife and kids won’t be here anyway during the first week of August and, on top of that, Samsung has been so kind to sponsor this trip just based on the simple fact that I’m part of the GNOME community. So, I certainly can no longer find a single reason not to go and spend 7 amazing days in Brno, meeting people that I normally see only in conferences (and this time that group of people will be bigger than ever, since my former mates from Igalia are now also included there), while attending to what it seems to be a very appealing event.

Also, I will try to make the most of the trip to do some work during the different hackfests and BoFs that are already planned, which special focus in the one about accessibility, of course. As a personal goal, I expect to have the chance to move forward some work I’ve been doing lately in the WebKitGTK+ a11y world, such as getting rid of the nasty dependency on Pango/Gail we still have there, something I’ve been already working on for some time now, and which I expect it will be fixed soon, hopefully before GUADEC, although time will tell.

Once that it’s fixed, WebKit2GTK+ based apps should recover the ability to properly expose text through the atk_text_get_text_*_offset() family of functions for different text boundaries, which means that ATs (e.g. the Orca screen reader)  will be able to properly allow again line-by-line navigation when in caret browsing mode. And, as you can imagine, this is quite a big problem these days, since WebKit2GTK+ that has become the default backend for some core apps such as the Epiphany browser with the GNOME 3.8 release, so fixing this is like a high priority now, I’d say.

Anyway, I’m starting to write too much (as usual) for what it was going to be a short “I’m going to GUADEC” blog post, so I will stop right now, although not without first thanking Samsung for sponsoring this my first trip to the Czech Republic.

See you all in three weeks!

With regard to that, it has been a very interesting experience so far where I could meet new people I still haven’t had the chance to see in real life yet (e.g. my mates from other Samsung R&D centers or some guys from Apple I didn’t have the chance to meet in person before), as well as chat again with some friends and former mates that I haven’t seen for a while, such as Martin, Xan and Philippe from Igalia, Byungseon from LG, Nayan from Motorola or Gustavo from Collabora to mention some of them. It’s strange, and at the same time wonderful, how easily you can catch up on conversations with people that you barely see once a year (or even less) and mainly in conferences, and definitely one of my favourite parts of attending these kind of events, to be honest.

Also, from a less social point of view, I have to say I found very interesting the sessions I’ve attended so far, specially the one about “managing the differences between ports”, although the one about “build systems” was quite interesting too. Not sure how far we are yet in the WebKitGTK+ port from realistically switching to some kind of commonly agreed build system (cmake?), but at least it’s a good start to agree on the fact that it would be an interesting move and now that some people pushing for it.

My only regret about this first day is that I missed Hyatt’s talk about pagination due to some health issues I’m experimenting while in California, mostly due to the extremely hot and dry weather (anything over 25 Celsius is “unbearable hot” for me), which is causing me a little bit of cough, sore throat and fever, all well mixed with the jet lag to make it a perfect “welcome pack” to the meeting. Fortunately, I got some “interesting” medicines that seem to have relieved a bit the pain and I could attend the rest of the sessions without much trouble, other than some occasional coughing. Not bad.

By the way, for those of you who were not lucky enough to attend the meeting but are anyway interested in the topics being discussed here, make sure you check the main TRAC page for the meeting, where you can also find transcripts for most of the sessions.

As for today, some more sessions will take place as well as a couple of hackathons so I expect it to be very interesting as well. Also I hope I can find some time too to work a bit on my patches to remove the nasty dependency on pango we have in WebKitGTK+ accessibility code, which is preventing us to have proper caret navigation in WebKit2GTK+ based browsers, as well as to discuss possible ways in which our lab could collaborate more actively upstream. Seems a promising day already!

Last (but not least), and in a completely unrelated and super-off-topic way, I would like to tell the world that I’m extremely happy for the fact that next week will be the end of my “lonely existence in the UK”, finally. After 4 months of living away from my family with just some flash trips from Friday to Sunday (every 2 weeks), I’m once and for all travelling on Thursday to my home town with a one way plane ticket to do some final arrangements, put everything (family included!) in the car and travel to Santander, where we’ll be taking a ferry that will take us to the Portsmouth (southern coast of England), from where we will just drive to the UK in order to start our new life, all together again.

It has been quite hard for us to live this way for so long, but I think in the end we managed to handle the situation quite well, and now it seems all our efforts are already paying off because things seem to be finally fitting in the right places: we have a lovely house, we have a place in a nearby public school for my oldest kid to start on September, most of the needed paperwork seems to be done and we already moved all our stuff from Spain (lots of toys!), which is now waiting to be used in our new place.

I really can’t wait to live again in the noisy and chaotic atmosphere that two kids can so easily create around them. Even if that means it will probably drive me crazy every now and then and that I won’t sleep that well sometimes.

Yes. Even considering that.

In order to help them better understand this topic, I wrote a summary to have as reference that explains in my own words which the main pieces of the whole puzzle are, and how they relate to one another. In my experience, it’s not always easy to understand the big picture quickly, and I think this kind of documentation can be quite useful for anyone willing to contribute to accessibility in WebKitGTK+. At least it would have been useful for me when I started working on this. I only regret not having written it before, but better late than never, right?

So let’s begin then. I will start by talking about accessibility-only stuff, which are basically common to any accessible application based in GTK+. Then I will explain the bits specific to WebKitGTK+ and how they fit in the picture.

Accessibility in GTK+ applications

• Assistive Technologies (ATs)
• AT-SPI (Assistive Technology Service Provider Interface)
• ATK (Accessibility ToolKit)
• ATK <-> AT-SPI bridge
• GTK+
• GTK's Accessibility Implementation

Now let’s describe all those points, one by one:

Assistive Technologies (ATs):

ATs are applications whose main purpose is to facilitate access and/or interaction with certain bits of information interesting from an accessibility related point of view, exposed by other applications. This access/interaction can be primarily output based. For instance the Orca screen reader is an AT which provides access via text to speech and/or refreshable braille to on-screen information exposed by editors, browsers, mail agents and other applications.

Other ATs are primarily input based, allowing the user to interact with the exposed applications by executing certain actions over them (e.g. clicking on a exposed link), so it’s not just about “consuming” information. Normally, ATs are called the clients and the applications exposing information the servers, as in the end it’s actually an implementation of a typical client/server architecture.

AT-SPI (Assistive Technology Service Provider Interface):

Set of interfaces that Assistive Technologies (the clients) understand and use to inspect and interact with the accessible content exposed by applications in Linux environments. At some point, “someone” has to provide actual AT-SPI objects (linked together forming a AT-SPI hierarchy) implementing several of those interfaces (depending of the type of object) so ATs can “see them”.

This is the job of the AT-SPI registry, a daemon which takes care of maintaining a hierarchy of AT-SPI objects for every single accessible application in the system, in a centralized way, so ATs can interact with them. It is worth mentioning that the parent/children relationships in that hierarchy are modelled in terms of D-Bus, so different AT-SPI objects can belong to different processes.

ATK (Accessibility ToolKit):

The toolkit used by GTK+ applications to expose accessible representations of the toolkit’s objects, along with appropriate interfaces, on the side of the applications exposing content (the servers). This representation is an almost a 1:1 match with the objects and interfaces defined by AT-SPI (that is, almost).

The main difference when it comes to understanding its place in the puzzle is that AT-SPI is what clients (ATs) understand, and that is not process-bounded (see previous point). ATK, in contrast, is what servers implement to expose accessible information, and it is process-bounded. Thus the parent/children relationships in the ATK hierarchy are modelled by actual references (pointers) between objects living in the same process.

ATK <-> AT-SPI bridge:

The glue that makes sure there’s a mapping between the ATK hierarchy living in the server process and the AT-SPI hierarchy held by the AT-SPI registry. Such a bridge is implemented in terms of D-Bus too, as it needs to communicate with the registry whenever something needs to be updated there, as well as when the server needs to react to external actions coming from ATs (e.g. perform the default action for an object).

GTK+:

The widgets toolkit normally used by applications embedding WebKitGTK+. Explaining what GTK+ is beyond the scope of this post, so I will assume you already know what it is.

GTK’s Accessibility Implementation:

Provides ATK objects implementing different ATK interfaces for every widget from the GTK+ library, and uses the ATK <-> AT-SPI bridge to communicate with the AT-SPI registry. This means that if you use standard GTK+ widgets only, your application will be accessible out-of-the-box. On the contrary, should you use custom widgets, you’ll probably have to write custom ATK objects implementing the proper ATK interfaces to make them accessible too.

So that’s all so far, when it comes to GTK+ applications. Check the following diagram for a more detailed look at all these hierarchies for a hypothetical GTK+ application exposing information and a screen reader accessing it:

As you can see, there’s an ATK tree matching the GTK+ hierarchy, and another AT-SPI tree matching the ATK one. Finally, the screen reader accesses the information through that AT-SPI tree, as explained above.

Accessibility in WebKitGTK+

• WebCore's Accessibility Objects
• WebKitGTK+ (ATK) wrappers
• WebKit2GTK+ specific details

In order to clarify it a bit more before explaining each point, let’s just say that  you’ll have to look in the dashed box named WebCore accessibility world, where the hierarchy on the left (red & orange) represent the WebCore Accessibility objects, while the one on the right (the green one) represents the WebKitGTK+ ATK wrappers.

With this in mind, let’s examine these three points in more depth:

WebCore Accessibility objects:

Similar to GTK’s Accessibility Implementation, WebCore’s accessibility objects are the implementation of an independent hierarchy exposing accessibility related information for objects present in a web page. As the mission of accessibility in WebKit is to expose information to users that are normally being rendered in the screen (as well as some other information that might be hidden to regular users), there is a tight relationship between this hierarchy and other ones in WebKit, such as the DOM tree and the Render Objects tree.

This layer is meant to be platform-agnostic, so you won’t find much WebKitGTK+ specific stuff here. Instead, you will find the implementation of the accessibility related specifications published by the W3C‘s Web Accessibility Initiative (WAI), such as WAI-ARIA.

WebKitGTK+ ATK wrappers:

An ATK-based implementation of an accessibility hierarchy where every ATK object will take care of wrapping the proper accessibility object from WebCore, as well as implementing the proper ATK interfaces depending on the situation (e.g. the role of the WebCore accessibility object, some properties coming from the associated Render Object…).

The ATK hierarchy created here is connected with the ATK hierarchy from the embedding application (normally a GTK+ app) by setting the root ATK object in this tree (normally representing DOM’s root element) as the child of the leaf ATK object in the tree coming from the embedding application (normally the GtkWidget containing the WebView).

As is the case with any other regular GTK+ application, this ATK hierarchy will finally be seen by ATs thanks to the translation that the ATK <-> AT-SPI bridge will do for us, making the whole ATK tree from the WebKitGTK+ based application (from the top level GTK+ window down to the deepest accessibility object inside WebCore) available to the AT-SPI registry by means of D-Bus.

WebKit2GTK+ specific details:

I already talked about this in previous posts, so I will focus here just on commenting the main difference compared to the generic case for WebKitGTK+ described earlier (see previous diagram above):

WebKit2GTK+ implements a split-process model, where the  high level API belongs to one process (the UI process) while the core logic of the web engine lives in another one (the Web process).

From an accessibility point of view, this means that the full hierarchy of ATK objects we had before is also split in two parts: some accessibility objects are now in the UI process and the rest of them will be in the Web process.

To be more specific, we’ll find the following objects in each process:

• UI Process: basically, the ATK object associated with the GtkWidget provided by WebKitGTK+, that is, the WebView.
• Web Process: the whole hierarchy of ATK objects wrapping the accessibility objects from WebCore.

Thus, since ATs just  understand AT-SPI, they will see The Right Thing (tm) as in the previous case where we have one single process. See the following diagram for a more visual explanation of this:

Wrapping up

At least I hope this will be helpful for anyone willing to contribute to accessibility, either in WebKitGTK+ or in a more general way.

After all, most of the stuff I talked about here applies to  every accesible GTK+ application: Assistive Technologies (ATs), AT-SPI, ATK, the ATK <-> AT-SPI bridge…

Last, I would like to thanks Joanmarie Diggs from Igalia for her help with this blog post. One certainly feels more confident writing a long article like this one about a very specific topic when you have one of the most experienced persons on the matter reviewing it!

As you can imagine, being the first week means that I mostly spent my time learning a lot of stuff about my new job and the tools I’d be using, as well as setting up my development environment and getting to know my colleagues and the things we’ll be working on.

But for the time being I have to say that my first impression has already been very positive and that I’m enthusiastically looking at the future and what it’s going to be next. Surely it will be a very different experience compared to what I was used to, but in a way that’s precisely what I was looking for, and so that’s why I feel very optimistic and motivated about it.

Also, and besides work related stuff, being a new resident in the UK also means that I had to spend some time doing some additional things, such as creating a bank account, getting a UK-based SIM card and starting to look for a place that should become our permanent residence in 2-3 months time, once my wife and my children move as well to the UK (they’re still in Spain), hopefully before Easter. Fortunately, being a EU citizen simplifies a lot the whole thing of coming here to work, since I don’t need any VISA or the like. Just my Spanish ID and/or Passport are more than enough.

Anyway, I’ve just arrived in the UK on Monday and started working on Tuesday (yeah, I love having big margins) so still much to do left, but I’m already on my way so it’s a matter of time that we are settled here, and that we start living the “English adventure” all together again.

But in the meanwhile we’ll have to live with me visiting them every 2-3 weeks and the typical audio/video conference tools.

Can’t wait!