WebKit Igalia Periodical #4

The documentation on GTK/WPE port profiling with Sysprof landed upstream.

Support for anchor-center alignment landed upstream for all the WebKit ports. This is a part of cutting-edge CSS spec called CSS Anchor Positioning. To test this feature, the CSSAnchorPositioning runtime preference needs to be enabled.

WebKit has since a long time offered a non-standard method Document.caretRangeFromPoint() to get the caret range at a certain coordinate, but now offers the same functionality in a standardised way.

We improved the multi touch support on WPE: the touch identifiers are now more reliable when using the Web API Pointer Events. This has been backported to the last stable release 2.46.4

On the JSC front, Justin Michaud has fixed a tricky issue in the implementation of Air shuffles (i.e. smartly copying N arbitrary locations to N different arbitrary locations). He also fixed some lowering code that generated invalid B3, as well as the 32-bit version of addI31Ref (part of the GC wasm extension).

Angelos Oikonomopoulos fixed another corner case in the testing of single-precision floating point arguments on 32-bits.

Support for multi-threaded GPU rendering landed upstream for both GTK/WPE ports. In main branch, GPU accelerated tile rendering was already activated by default—it is still the case, but now it utilizes one extra GPU rendering thread instead of performing the GPU rendering using (and blocking) the main thread.

The number of threads used for CPU multi-threaded rendering was controlled by the WEBKIT_SKIA_PAINTING_THREADS environment variable and has been renamed to WEBKIT_SKIA_CPU_PAINTING_THREADS. Likewise we now support the setting WEBKIT_SKIA_GPU_PAINTING_THREADS (where 0 implies using the main thread, and values in the 1 to 4 range enable threaded GPU rendering) to control the amount of GPU rendering threads used.

Negotiation of buffer formats with Wayland using DMA-BUF feedback was getting the first format that fits with the requirements in the first tranche even when the transparency did not match. Now we honor the transparency if there is a way to do it, even when other tranches than the first one need to be used. This allows the compositor to do direct scanout in more cases.

This has been a week filled with releases!

On the stable series, WebKitGTK 2.46.4 and WPE WebKit 2.46.4 include the usual stream of small fixes, a number of multimedia handling improvements focused on around Media Stream, and two important security fixes covered in a new security advisory (WSA‑2024‑0007: GTK, WPE). The covered vulnerabilities are known to be exploited in the wild, and updating is strongly encouraged; fresh packages are already available (or will be soon) in popular Linux distributions.

Also, development releases WebKitGTK 2.47.2 and WPE WebKit 2.47.2 are now available. The main highlights are the multi-threaded GPU rendering, and the added system settings API in WPEPlatform. These development snapshots are often timed around important changes; we greatly appreciate when people put the effort to give them a try, because detecting (and reporting) any issues earlier is a great help that gives us developers more time to polish the code before it reaches a stable version.

Flatpak 1.15.11 was released with a handful of patches related to accessibility. These patches enable WebKit accessibility to work in sandboxed environments. With this release, all the pieces of this puzzle fell in place, and now sandboxed apps that use WebKit are properly accessible and introspectable by screen readers and Braille generators.

Of course, there are further improvements to be made, and lots of fine-tuning to how WebKit handles accessibility of web pages. But this is nonetheless an exciting step, both for accessibility on Linux and also for the platform.

A WPE MiniBrowser runner for the Web-Platform-Tests (WPT) cross-browser test suite was added recently. Please check the documentation on how to use it and remember that there is also a WebKitGTK MiniBrowser runner there also available. Both runners allow to automatically download and use the last nightly universal bundle for running the tests if you pass the flag --install-browser to ./wpt run. Pass also --log-mach=- for increased verbosity. Please note that this only adds the runner for manual testing. We are still working on adding WPE to the automated testing dashboard at wpt.fyi

Justin Michaud submitted a fix for flashing Yocto images to external SD cards.

The WPE WebKit web site now has a separate RSS feed for security advisories. It can be reached at https://wpewebkit.org/security.xml and may be useful for those interested in automated notifications about security fixes.