This fall, the WPE WebKit team has released the 2.50 series of the Web engine after six months of hard work. Let’s have a deeper look at some of the most interesting changes in this release series!
Improved rendering performance
For this series, the threaded rendering implementation has been switched to use the Skia API. What has changed is the way we record the painting commands for each layer. Previously we used WebCore’s built-in mechanism (DisplayList) which is not thread-safe, and led to obscure rendering issues in release builds and/or sporadic assertions in debug builds when replaying the display lists in threads other than the main one. The DisplayList usage was replaced with SkPictureRecorder, Skia’s built-in facility, that provides similar functionality but in a thread-safe manner. Using the Skia API, we can leverage multithreading in a reliable way to replay recorded drawing commands in different worker threads, improving rendering performance.
An experimental hybrid rendering mode has also been added. In this mode, WPE WebKit will attempt to use GPU worker threads for rendering but, if these are busy, CPU worker threads will be used whenever possible. This rendering mode is still under investigation, as it is unclear whether the improvements are substantial enough to justify the extra complexity.
Damage propagation to the system compositor, which was added during the 2.48 cycle but remained disabled by default, has now been enabled. The system compositor may now leverage the damage information for further optimization.
Vertical writing-mode rendering has also received improvements for this release series.
Changes in Multimedia support
When available in the system, WebKit can now leverage the XDG desktop portal for accessing capture devices (like cameras) so that no specific sandbox exception is required. This provides secure access to capture devices in browser applications that use WPE WebKit.
Managed Media Source support has been enabled. This potentially improves multimedia playback, for example in mobile devices, by allowing the user agent to react to changes in memory and CPU availability.
Transcoding is now using the GStreamer built-in uritranscodebin element instead of GstTranscoder, which improves stability of the media recording that needs transcoding.
SVT-AV1 encoder support has been added to the media backend.
WebXR support
The WebXR implementation had been stagnating since it was first introduced, and had a number of shortcomings. This was removed in favor of a new implementation, also built using OpenXR, that better adapts to the multiprocess architecture of WebKit.
This feature is considered experimental in 2.50, and while it is complete enough to load and display a number of immersive experiences, a number of improvements and optional features continue to be actively developed. Therefore, WebXR support needs to be enabled at build time with the ENABLE_WEBXR=ON CMake option.
Android support
Support for Android targets has been greatly improved. It is now possible to build WPE WebKit without the need for additional patches when using the libwpe-based WPEBackend-android. This was achieved by incorporating changes that make WebKit use more appropriate defaults (like disabling MediaSession) or using platform-specific features (like ASharedMemory and AHardwareBuffer) when targeting Android.
The WebKit logging system has gained support to use the Android logd service. This is particularly useful for both WebKit and application developers, allowing to configure logging channels at runtime in any WPE WebKit build. For example, the following commands may be used before launching an application to debug WebGL setup and multimedia playback errors:
adb setprop log.tag.WPEWebKit VERBOSE # Global logging filter
adb setprop debug.WPEWebKit.log 'WebGL,Media=error' # Channels
adb logcat -s WPEWebKit # Follow log messagesThere is an ongoing effort to enable the WPEPlatform API on Android, and while it builds now, rendering is not yet working.
Web Platform support
As usual, changes in this area are extensive as WebKit constantly adopts, improves, and supports new Web Platform features. However, some interesting additions in this release cycle include:
- The new CookieStore API.
- ManagedMediaSource.
- CSS container-progress().
- CSS text-wrap-style: pretty.
- CSS font-family: math.
- CSS Animation: support for the overallProgress property.
- HTML auto-expanding <details>.
- CSS hidden=“until-found”.
API changes
- The WebKitSettings:enable-hyperlink-auditing option has been deprecated. This feature is now always enabled.
- The
webkit_web_view_get_theme_color()function has been added to allow querying the theme color declared by the content loaded in a web view. The corresponding WebKitWebView:theme-color property is available as well, which allows using thenotifysignal to watch for theme color changes.
WPEPlatform
Work continues on the new WPEPlatform API, which is still shipped as a preview feature in the 2.50 and needs to be explicitly enabled at build time with the ENABLE_WPE_PLATFORM=ON CMake option. The API may still change and applications developed using WPEPlatform are likely to need changes with future WPE WebKit releases; but not for long: the current goal is to have it ready and enabled by default for the upcoming 2.52 series.
One of the main changes is that WPEPlatform now gets built into libWPEWebKit. The rationale for this change is avoiding shipping two copies of shared code from the Web Template Framework (WTF), which saves both disk and memory space usage. The wpe-platform-2.0 pkg-config module is still shipped, which allows application developers to know whether WPEPlatform support has been built into WPE WebKit.
The abstract base class WPEScreenSyncObserver has been introduced, and allows platform implementations to notify on display synchronization, allowing WebKit to better pace rendering.
WPEPlatform has gained support for controllers like gamepads and joysticks through the new WPEGamepadManager and WPEGamepad classes. When building with the ENABLE_MANETTE=ON CMake option a built-in implementation based on libmanette is used by default, if a custom one is not specified.
WPEPlatform now includes a new WPEBufferAndroid class, used to represent graphics buffers backed by AHardwareBuffer. These buffers support being imported into an EGLImage using wpe_buffer_import_to_egl_image().
As part of the work to improve Android support, the buffer rendering and release fences have been moved from WPEBufferDMABuf to the base class, WPEBuffer. This is leveraged by WPEBufferAndroid, and should be helpful if more buffer types are introduced in the future.
Other additions include clipboard support, Interaction Media Features, and an accessibility implementation using ATK.
What’s new for WebKit developers?
WebKit now supports sending tracing marks and counters to Sysprof. Marks indicate when certain events occur and their duration; while counters track variables over time. Together, these allow developers to find performance bottlenecks and monitor internal WebKit performance metrics like frame rates, memory usage, and more. This integration enables developers to analyze the performance of applications, including data for WebKit alongside system-level metrics, in a unified view. For more details see this article, which also details how Sysprof was improved to handle the massive amounts of data produced by WebKit.
Finally, GCC 12.2 is now the minimum required version to build WPE WebKit. Increasing the minimum compiler version allows us to remove obsolete code and focus on improving code quality, while taking advantage of new C++ and compiler features.
Looking forward to 2.52
The 2.52 release series will bring even more improvements, and we expect it to be released during the spring of 2026. Until then!
Claudio is long-time WebKit contributor from Igalia, working in different areas of WebKit, WPE, and the stack around it.