This month in Servo: new elements, IME support, delegate API, and more!

Servo now supports more HTML and CSS features:

• the <details> element (@simonwuelker, #35261)
• the <meter> element (@simonwuelker, #35524)
• the <progress> element (@simonwuelker, #35531)
• the ‘quotes’ property (@xiaochengh, @Loirooriol, #34770, #35420)
• the ‘isolation’ property (@kkoyung, @Loirooriol, #35552)
• ‘overflow: clip’ (@longvatrong111, #35103)
• ‘overflow’ property with two values (@yezhizhen, @mrobinson, #35414)
• the ‘::slotted’ selector (@simonwuelker, #35352)

Plus several new web API features:

• contextmenu events (@pewsheen, #35364)
• WritableStream (@gterzian, @jdm, #34844)
• ReadableStreamBYOBRequest (@Taym95, #35074)
• initial support for FontFace and its load() method (@mukilan, #35262)
• toBlob() and toDataURL() on WebGPU canvases (@sagudev, #35237)
• bytes() on Request, Response, and Blob (@shanehandley, @yoseio, @gterzian, @Taym95, #35250, #35151)
• href, origin, protocol, username, password, host, hostname, port, pathname, search, and hash properties on HTMLAreaElement (@shanehandley, #35482)
• insertRule() with no argument on CSSGroupingRule (@Loirooriol, #35295)

<slot> elements are now fully supported including layout (@simonwuelker, #35220, #35519), and we’ve also landed support for the ‘::slotted’ selector (@simonwuelker, #35352). Shadow roots are now supported in devtools (@simonwuelker, #35294), and we’ve fixed some bugs related to shadow DOM trees (@simonwuelker, #35276, #35338), event handling (@simonwuelker, #35380), and custom elements (@maxtidev, @jdm, #35382).

We’ve landed layout improvements around ‘border-collapse’ (@Loirooriol, #35219), ‘align-content: normal’ (@rayguo17, #35178), ‘place-self’ with ‘position: absolute’ (@Loirooriol, #35208), the intrinsic sizing keywords (@Loirooriol, #35413, #35469, #35471, #35630, #35642, #35663, #35652, #35688), and ‘position: absolute’ now works correctly in a ‘position: relative’ grid item (@stevennovaryo, #35014).

Input has also been improved, with better IME support (@dklassic, #35535, #35623) and several fixes to touch input (@kongbai1996, @jschwe, @shubhamg13, #35450, #35031, #35550, #35537, #35692).

Servo-the-browser (servoshell)

Directory listings are now enabled for local files (@mrobinson, #35317).

servoshell’s dialogs now use egui (@chickenleaf, #34823, #35399, #35464, #35507, #35564, #35577, #35657, #35671), rather than shelling out to a program like zenity (@chickenleaf, #35674), making them more secure and no longer falling back to terminal input.

We’ve also fixed a bug when closing a tab other than the current one (@pewsheen, #35569).

Servo-the-engine (embedding)

We’ve simplified our embedding API by merging all input event delivery into WebView::notify_input_event (@mrobinson, @mukilan, #35430), making bluetooth optional (@jdm, @webbeef, #35479, #35590), making the “background hang monitor” optional (@jdm, #35256), and eliminating the need to depend on webxr (@mrobinson, #35229). We’ve also moved some servoshell-only options out of Opts (@mrobinson, #35377, #35407), since they have no effect on Servo’s behaviour.

We’ve landed our initial delegate-based API (@delan, @mrobinson, @mukilan, #35196, #35260, #35297, #35396, #35400, #35544, #35579, #35662, #35672), which replaces our old message-based API for integrating Servo with your app (@mrobinson, @delan, @mukilan, #35284, #35315, #35366). By implementing WebViewDelegate and ServoDelegate and installing them, you can have Servo call back into your app’s logic with ease.

We’ve simplified the RenderingContext trait (@wusyong, @mrobinson, #35251, #35553) and added three built-in RenderingContext impls (@mrobinson, @mukilan, #35465, #35501), making it easier to set up a context Servo can render to:

• WindowRenderingContext renders to a whole window
• OffscreenRenderingContext renders to part of a window
• SoftwareRenderingContext renders to an image, without hardware acceleration

We’ve heavily reworked and documented our webview rendering model (@mrobinson, @wusyong, @mukilan, #35522, #35621), moved image output and shutdown logic out of the compositor (@mrobinson, @wusyong, #35538), and removed some complicated logic around synchronous repaints when a window is resized (@mrobinson, #35283, #35277). These changes should make it a lot clearer how to get Servo’s webviews onto your display.

One part of this model that we’re starting to move away from is the support for multiple webviews in one rendering context (@mrobinson, @wusyong, #35536). First landed in #31417, this was an expedient way to add support for multiple webviews, but it imposed some serious limitations on how webviews could be interleaved with other app content, and the performance and security was inadequate.

We’ve updated our winit_minimal example to take advantage of these changes (@webbeef, #35350, #35686), simplify it further (@robertohuertasm, #35253), and fix window resizing (@webbeef, #35691).

Perf and stability

The compositor now notifies the embedder of new frames immediately (@mrobinson, #35369), not via the constellation thread.

Servo’s typical memory usage has been reduced by over 1% thanks to Node object optimisations (@webbeef, #35592, #35554), and we’ve also improved our memory profiler (@webbeef, #35618, #35607).

We’ve fixed a bug causing very high CPU usage on sites like wikipedia.org (@webbeef, #35245), as well as bugs affecting requestAnimationFrame (@mukilan, #35387, #35435).

You can now configure our tracing-based profiler (--features tracing) with servo --tracing-filter instead of SERVO_TRACING (@jschwe, #35370).

We’ve continued reducing our use of unsafe in script (@nscaife, @stephenmuss, #35351, #35360, #35367, #35411), and moving parts of script to script_bindings (@jdm, #35279, #35280, #35292, #35457, #35459, #35578, #35620). Breaking up our massive script crate is absolutely critical for reducing Servo’s build times.

We’ve fixed crashes that happen when moving windows past the edge of your monitor (@webbeef, #35235), when unpaired UTF-16 surrogates are sent to the DOM (@mrobinson, #35381), when focusing elements inside shadow roots (@simonwuelker, #35606), and when calling getAsString() on a DataTransferItem (@Gae24, #35699). We’ve also continued working on static analysis that will help catch crashes due to GC borrow hazards (@augustebaum, @yerke, @jdm, @Gae24, #35541, #35593, #35565, #35610, #35591, #35609, #35601, #35596, #35595, #35594, #35597, #35622, #35604, #35616, #35605, #35640, #35647, #35646).

Donations

Thanks again for your generous support! We are now receiving 4363 USD/month (+13.7% over January) in recurring donations. This helps cover the cost of our self-hosted CI runners and Outreachy internships.

Servo is also on thanks.dev, and already 21 GitHub users (+5 over January) that depend on Servo are sponsoring us there. If you use Servo libraries like url, html5ever, selectors, or cssparser, signing up for thanks.dev could be a good way for you (or your employer) to give back to the community.

4363 USD/month

10000

As always, use of these funds will be decided transparently in the Technical Steering Committee. For more details, head to our Sponsorship page.