This Month in Linebender, August 2025 (#121)

[#linebender > This month in Linebender @
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A pretty big month, with huge news on Fearless SIMD, Blending in Vello
Hybrid, big Xilem updates, Anymore v1.0, and HarfRust usage.

Author: DJMcNab

content/blog/2025-09-12-tmil-20/hybrid-blending.png

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+title = "Linebender in August 2025"
+authors = ["Daniel McNab"]
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+
+Linebender is an informal open-source organization working on various projects to advance the state of the art in GUI for [the Rust programming language](https://rust-lang.org).
+
+## Parley
+
+Parley is a text layout library.
+It handles text layout, mostly at the level of line breaking and resolving glyph positions.
+
+- [parley#400][]: Migrates Parley to [HarfRust](https://github.com/harfbuzz/harfrust) for shaping, which is a Rust port of HarfBuzz.
+- [parley#405][]: Adds a selection of benchmarks.
+- [parley#406][], [parley#413][]: Adds internal caching, improving performance significantly.
+
+## Vello
+
+Vello is our GPU vector renderer.
+It can draw large 2D scenes with high performance, using GPU compute shaders for most of the work.
+
+- [vello#1096][]: Updated to Wgpu version 26.
+- [vello#1161][]: Simplifies the API for rendering a wgpu `Texture` into a Vello `Scene`.
+- [vello#1169][]: Increased the Skrifa version to v0.35.0. This was backported as [Vello v0.5.1](https://github.com/linebender/vello/releases/tag/v0.5.1).
+- [vello#1182][]: Fixed a longstanding issue with our examples, where they would crash if the window was minimised on windows.
+
+The biggest updates to the sparse strip renderers this month are the support for blending and caching in Vello Hybrid.
+We have also had continued SIMD improvements, including x86 support.
+
+- [vello#1136][]: Allows disabling anti-aliasing.
+- [vello#1137][], [vello#1153][]: Add support for caching sparse strips.
+- [vello#1149][]: Support for SSE4.2 and AVX2 SIMD (i.e. on x86 and x86_64).
+  The [benchmark results viewer](https://laurenzv.github.io/vello_chart/) has been updated to include some x86_64 results.
+- [vello#1177][]: Move to the new v0.2.0 release of Fearless SIMD.
+- [vello#1155][], [vello#1178][]: Add full support for blending to Vello Hybrid.
+
+<!-- TODO: This roadmap is a bit out of date.
+Our [working roadmap](https://docs.google.com/document/d/1ZquH-53j2OedTbgEKCJBKTh4WLE11UveM10mNdnVARY/edit?tab=t.0#heading=h.j3duh9pgdm94) outlines the planned timeline for work on the renderers into next year. -->
+
+<img style="height: auto; width: 50%; margin-left: 25%;" width="666" height="673" src="hybrid-blending.png" alt="A series of overlapping shapes of various colours, variously composited.">
+
+<figcaption>
+
+Blending is now supported by Vello Hybrid.
+
+</figcaption>
+</figure>
+
+We have additionally been doing further work on Vello's imaging model.
+This is partly in service of the integrations of Vello in [Graphite](https://graphite.rs/) and [Servo](https://servo.org/).
+
+- [color#191][], [peniko#115][] (in progress): Add support for interpolating gradients in unpremultiplied space.
+  This is provided for web compatibility, and shouldn't be used by most users.
+- [peniko#117][]: Split Image into the sampler and data.
+- [peniko#120][], [peniko#121][]: Add `Brga` and premultiplied image formats.
+- [vello#1183][] (in progress): Support luminance masks.
+
+As of [servo#38962][], Vello and Vello CPU are the only canvas backends used in Servo.
+
+### Fearless SIMD
+
+Fearless SIMD is our SIMD infrastructure library.
+We are developing it in concert with the Vello sparse strips renderers, particularly `vello_cpu`.
+We released [Fearless SIMD v0.2.0](https://github.com/linebender/fearless_simd/releases/tag/v0.2.0), the first Fearless SIMD release since 2018.
+This included the following changes from August:
+
+- [fearless_simd#50][], [fearless_simd#52][]: Add SSE4.2 support.
+- [fearless_simd#58][]: Add some initial docs.
+- [fearless_simd#59][]: Add basic AVX2 support.
+- [fearless_simd#61][]: Removes `f16` support to prepare for release.
+- [fearless_simd#69][]: Fixes a soundness issue with unsafe SIMD functions.
+
+With this release, Fearless SIMD is now ready for experimental use outside of Linebender.
+It now provides a solid way for writing portable SIMD operations across WASM, Aarch64, x86, and x86_64.
+Note however that the library is still in a quite early state - in particular, our documentation is currently only cursory.
+Contributions to improve this would be welcome!
+
+## Masonry
+
+Masonry is the widget system developed by Linebender.
+It provides a non-opinionated retained widget tree, designed as a base layer for high-level GUI frameworks.
+
+- [xilem#1207][]: Make `ObjectFit`, `Linebreaking` and `SpinnerColor` properties.
+- [xilem#1212][]: Add `Widget::Action`, which indicates the action type widgets return.
+- [xilem#1226][]: Refactor tab focus.
+- [xilem#1228][]: Add placeholder text to text input.
+- [xilem#1250][]: Move widgets to use a `Length` type, which represents a number of logical pixels.
+- [xilem#1269][]: Introduce "focus fallback" mechanism.
+- [xilem#1273][]: Update to Anymore v1.0.
+- [xilem#1282][], many others: Add unit tests for passes.
+- [xilem#1295][]: Merge `TextColor` and `SpinnerColor` into `ContentColor`.
+- [xilem#1310][]: Cleans up how the event loop handles being suspended, by Nixon.
+- [xilem#1312][]: Remove the generic on VirtualScroll.
+- [xilem#1314][]: Makes the focused indicator for checkboxes larger, by tannal.
+- [xilem#1320][]: Add `NewWindow` struct to encapsulate attributes needed to create a window.
+- [xilem#1321][]: When a new font is loaded, relayout everything.
+- [xilem#1332][]: Restore base colour customisation.
+- [xilem#1349][]: Move Masonry's examples from "Masonry Winit" to "Masonry".
+- [xilem#1353][]: Limit the size of screenshot tests to 8KiB by default.
+- [xilem#1366][]: Make the `Checkbox`'s checked state be controlled only by the driver.
+- [xilem#1371][]: Fix and optimise window resizing and minimising.
+
+## Xilem
+
+Xilem is our flagship GUI project, inspired by SwiftUI, which uses Masonry for its widgets.
+It lets you build user interfaces declaratively by composing lightweight views together, and will diff them to provide minimal updates to a retained layer.
+
+- [xilem#1260][]: Make the virtual scroll implementation much saner.
+- [xilem#1273][]: Update to Anymore v1.0.
+- [xilem#1363][]: Fix the `declare_property_tuple` macro, by Alex Moon.
+- [xilem#1278][]: Add `Prop`, which changes how Masonry `Properties` are applied to more closely match Xilem Web.
+- [xilem#1318][]: Fix initial font loading in easy cases.
+- [xilem#1333][]: Add docs about precise capturing, by Nils Martel.
+- [xilem#1348][]: Add `flex_row` and `flex_col` as convenience functions, by Paul Xu.
+- [xilem#1352][]: Add error handling to virtual cats example, by Nils Martel.
+- [xilem#1357][]: Fix how the `disabled` property is handled for text input.
+- [xilem#1364][]: Remove the `app_state` parameter from teardown, by Alex Moon.
+
+Placehero:
+
+- [xilem#1323][]: Use an Action for navigation (rather than directly setting fields on the app state).
+- [xilem#1337][]: Use virtual scrolling for timelines.
+- [xilem#1370][]: Show the blurhash based preview of media attachments.
+
+<figure>
+
+<img style="height: auto" width="1991" height="891" src="placehero-progress.png" alt="Two screenshots of a Mastodon app. Left shows the post announcing Matt Campbell's RustWeek 2025 talk, including a very low detail image with alt text shown below. The right screen shows posts from googlefonts@typo.social, which was entered in a box in the left sidebar of the app.">
+
+<figcaption>
+
+Placehero can now load content from anywhere in a user's timeline, and preview images (left).
+It can also jump directly to a specific user's timeline by username (right).
+Note that full image loading is not yet supported, only the preview based on the blurhash.
+
+</figcaption>
+</figure>
+
+## Anymore
+
+On 4 August, we released [Anymore v1.0.0](https://github.com/linebender/anymore/releases/tag/v1.0.0).
+This is our crate for the fundamental `AnyDebug` trait, which greatly aids debugging when using dynamically typed values.
+Anymore is designed to be used in public APIs; it has a minimal API surface so that it can be extremely stable.
+We recommend considering it for use cases where you would otherwise be returning (potentially wrapped) `Box<dyn Any>` values from your libraries.
+
+## Kurbo
+
+Kurbo provides data structures and algorithms for curves and vector paths.
+We've been preparing for the 0.12 release:
+
+- [kurbo#476][]: Adds an `Axis` type taken from Masonry.
+- [kurbo#483][]: Document Kurbo's feature flags.
+- [kurbo#485][]: Better handle edge cases in cubic_to_quadratic, by Cosimo Lupo.
+- [kurbo#486][]: Deprecate and replace existing `aspect_ratio` methods, which used a non-standard definition of aspect ratio.
+- [kurbo#487][], [kurbo#488][], [kurbo#489][]: Remove many long-deprecated items.
+- [kurbo#490][]: Fix miter join in dashed strokes.
+- [kurbo#493][] (in progress): Convert `CubicBez::nearest` to the `poly-cool` quintic solver.
+
+## Get Involved
+
+We welcome collaboration on any of our crates.
+This can include improving the documentation, implementing new features, improving our test coverage, or using them within your own code.
+
+We host an hour long office hours meeting each week where we discuss what's going on in our projects.
+See [#office hours in Zulip](https://xi.zulipchat.com/#narrow/channel/359642-office-hours) for details.
+We're also running a separate office hours time dedicated to the renderer collaboration, details also available at that link.
+
+If you wish to discuss the Linebender project individually, Daniel is offering ["office hours" appointments](https://calendar.google.com/calendar/u/0/appointments/schedules/AcZssZ32eQYJ9DtZ_wJaYNtT36YioETiloZDIdImFpBFRo5-XsqGzpikgkg47LPsiHhpiwiQ1orOwwW2), which are free to book.
+It really helps us to learn what aspects our users care about the most.
+
+[servo#38962]: https://github.com/servo/servo/pull/38962
+
+[color#191]: https://github.com/linebender/color/pull/191
+
+[fearless_simd#50]: https://github.com/linebender/fearless_simd/pull/50
+[fearless_simd#52]: https://github.com/linebender/fearless_simd/pull/52
+[fearless_simd#58]: https://github.com/linebender/fearless_simd/pull/58
+[fearless_simd#59]: https://github.com/linebender/fearless_simd/pull/59
+[fearless_simd#61]: https://github.com/linebender/fearless_simd/pull/61
+[fearless_simd#69]: https://github.com/linebender/fearless_simd/pull/69
+
+[kurbo#476]: https://github.com/linebender/kurbo/pull/476
+[kurbo#483]: https://github.com/linebender/kurbo/pull/483
+[kurbo#485]: https://github.com/linebender/kurbo/pull/485
+[kurbo#486]: https://github.com/linebender/kurbo/pull/486
+[kurbo#487]: https://github.com/linebender/kurbo/pull/487
+[kurbo#488]: https://github.com/linebender/kurbo/pull/488
+[kurbo#489]: https://github.com/linebender/kurbo/pull/489
+[kurbo#490]: https://github.com/linebender/kurbo/pull/490
+[kurbo#493]: https://github.com/linebender/kurbo/pull/493
+
+[parley#400]: https://github.com/linebender/parley/pull/400
+[parley#405]: https://github.com/linebender/parley/pull/405
+[parley#406]: https://github.com/linebender/parley/pull/406
+[parley#413]: https://github.com/linebender/parley/pull/413
+[peniko#115]: https://github.com/linebender/peniko/pull/115
+[peniko#117]: https://github.com/linebender/peniko/pull/117
+[peniko#120]: https://github.com/linebender/peniko/pull/120
+[peniko#121]: https://github.com/linebender/peniko/pull/121
+
+[vello#1096]: https://github.com/linebender/vello/pull/1096
+[vello#1136]: https://github.com/linebender/vello/pull/1136
+[vello#1137]: https://github.com/linebender/vello/pull/1137
+[vello#1149]: https://github.com/linebender/vello/pull/1149
+[vello#1153]: https://github.com/linebender/vello/pull/1153
+[vello#1155]: https://github.com/linebender/vello/pull/1155
+[vello#1161]: https://github.com/linebender/vello/pull/1161
+[vello#1169]: https://github.com/linebender/vello/pull/1169
+[vello#1177]: https://github.com/linebender/vello/pull/1177
+[vello#1178]: https://github.com/linebender/vello/pull/1178
+[vello#1182]: https://github.com/linebender/vello/pull/1182
+[vello#1183]: https://github.com/linebender/vello/pull/1183
+
+[xilem#1207]: https://github.com/linebender/xilem/pull/1207
+[xilem#1212]: https://github.com/linebender/xilem/pull/1212
+[xilem#1226]: https://github.com/linebender/xilem/pull/1226
+[xilem#1228]: https://github.com/linebender/xilem/pull/1228
+[xilem#1250]: https://github.com/linebender/xilem/pull/1250
+[xilem#1260]: https://github.com/linebender/xilem/pull/1260
+[xilem#1269]: https://github.com/linebender/xilem/pull/1269
+[xilem#1273]: https://github.com/linebender/xilem/pull/1273
+[xilem#1278]: https://github.com/linebender/xilem/pull/1278
+[xilem#1282]: https://github.com/linebender/xilem/pull/1282
+[xilem#1295]: https://github.com/linebender/xilem/pull/1295
+[xilem#1310]: https://github.com/linebender/xilem/pull/1310
+[xilem#1312]: https://github.com/linebender/xilem/pull/1312
+[xilem#1314]: https://github.com/linebender/xilem/pull/1314
+[xilem#1318]: https://github.com/linebender/xilem/pull/1318
+[xilem#1320]: https://github.com/linebender/xilem/pull/1320
+[xilem#1321]: https://github.com/linebender/xilem/pull/1321
+[xilem#1323]: https://github.com/linebender/xilem/pull/1323
+[xilem#1332]: https://github.com/linebender/xilem/pull/1332
+[xilem#1333]: https://github.com/linebender/xilem/pull/1333
+[xilem#1337]: https://github.com/linebender/xilem/pull/1337
+[xilem#1348]: https://github.com/linebender/xilem/pull/1348
+[xilem#1349]: https://github.com/linebender/xilem/pull/1349
+[xilem#1352]: https://github.com/linebender/xilem/pull/1352
+[xilem#1353]: https://github.com/linebender/xilem/pull/1353
+[xilem#1357]: https://github.com/linebender/xilem/pull/1357
+[xilem#1363]: https://github.com/linebender/xilem/pull/1363
+[xilem#1364]: https://github.com/linebender/xilem/pull/1364
+[xilem#1366]: https://github.com/linebender/xilem/pull/1366
+[xilem#1370]: https://github.com/linebender/xilem/pull/1370
+[xilem#1371]: https://github.com/linebender/xilem/pull/1371