Off The Main Thread

In this episode, Jake goes through some of the newer features of the View Transition API, along with some vaguer ideas that are planned for the future.

Resources

• General view transitions docs
• Custom entry and exit transitions
• hasUAVisualTransition so you know when the UA has done its own transition
• view-transition-class
• view-transition-types
• Cross-document view transitions
• to wait for a particular element
• The blocking attribute to wait for a particular resource
• The pageswap and pagereveal events
• Nested view transitions
• The match-element vs auto discussion
• Scoped view transitions
• attr() in Chrome
• Safari just went and released view-transition-name: auto

In this episode, Surma talks about a presenation-maybe-soon-to-be-a-proposal "JS0", which explores the idea of splitting JavaScript into two specifications: JS0, focusing on security, performance and capabilties, implemented by engines; and JSSugar, focussing on developer productivity and syntactic sugar features implemented by build tools.

Notes & Corrections:

• Yes, I know, people still do have to step through assembler. But I stand behind the essence of my point: The debug symbols for compiled languages feel very reliable. We should be able to at least match that reliability in JavaScript.
• Guy Bedford currently works at Fastly.

Resources:

• Previous episode on Shared Structs
• The infamous slide deck
• OTMT episode on SourceMaps on source maps

In this episode, Surma talks about the Stage 2 proposal "JavaScript Struct", which introduces fixed-layout objects and the ability to share them between realms.

Notes & Corrections from Shu:

Surma was slightly wrong about why private fields were originally considered problematic for sharability. The problem occurs when a class can be evaluated multiple times:

function makeClass() { return class MyClass { #priv; getPrivateField(instance) { return instance.#priv; } }; } const C1 = makeClass(); const C2 = makeClass(); const i1 = new C1(); const i2 = new C2(); // this throws! i1.getPrivateField(i2);

This behavior makes it hard to compile private fields just as "slots" on an object, as clearly additional behavior is required. This is somewhat at odds with the goal of achieving a fixed layout.

Also, launching is mid-2025 is very optimistic.

Resources:

• SharedArrayBuffer
• Structs proposal
• Return overrides
• Records & Tuples proposal
• Surma's buffer-backed-object library for SharedArrayBuffer

After talking about Bazel in one of our previous episodes, we are now looking at Nix, a build system that has been getting increasing attention lately.

Resources:

• OTMT Bazel episode
• Surma's video on Nix
• Eelco Dolstra's PhD Thesis
• Nix & NixOS
• A branch of Squoosh using Nix
• Nixpkgs manual
• Comparison of size and freshness of different package managers
• Home Manager
• Nix pills

We're finally getting a element we can fully control with CSS! A bunch of other stuff needed to be added to the platform to make it work, and the good news is we can use it a lot of them independently of .

Resources:

• Chrome's article on the new , and how you can provide feedback.
• The CSS appearance property. Nope, I still don't know what it does.
• The Popover API.
• "On popover accessibility: what the browser does and doesn't do" by Hidde de Vries and Scott O'Hara.
• The CSS anchor positioning API.
• The previous spatnav spec effort.
• The hidden attribute until-found value (sorry, I said if-found in the episode).
• The CSS element function.
• Timing of cloning for the element.
• Animating to height auto.
• The new entry-exit animation feautres.
• The proposed command and commandfor attributes which give buttons declaritive activation behavior.

Chrome is experimenting with exposing an LLM to the web platform. Jake and Surma dig into how the API works, and whether something like this could work on the open web.

Resources:

• The explainer
• ChatGPT functions
• Chrome's initial vague docs about the feature
• Gemini terms of use
• The EURion constellation
• WebNN

Luca found a hidden Chrome extension that is installed by default in Chrome and most Chromium derivatives. Surma and Jake dig into what this extensions does and how reasonable it is to get angry about it.

Resources:

• Luca's original tweet thread
• The extension's source code
• Discussion on blink-dev
• The original PR that introduced the extension
• Brendan Eich's response
• Brave PR disabling the extension

In this episode, Jake and Surma chat about web components. Why they were invented, what they're useful for, and how they would improve.

Resources:

• Surma showers his eyeball.
• The old custom elements 'v0' spec.
• The old shadow DOM 'v0' spec.
• The old HTML imports spec.
• The initial version of Polymer.
• Lit (formally lit-html).
• HTML attributes vs DOM properties.
• Issue looking at ways custom elements could have behavior.
• The ElementInternals API, for making custom elements interact with forms.
• The is attribute.
• WebKit's position on the is attribute.
• Programmatically assigning children to slots.
• Issue looking at ways to slot children that aren't direct children of the shadow host.
• Declarative shadow DOM.
• Custom element support in React 19.
• pinch-zoom custom element.

In this episode, Surma shares with Jake all the things he learned reading up on source maps and DWARF.

Resources:

• Jake's Jericho triangle
• source-map-explorer
• Hacker News comment by Joseph Shorr on the origins of source maps
• The Source Map "specification"
• EvanW's source map visualizer
• Wikipedia: VLQ
• DWARF specification
• llvm-dwarfdump
• gimli
• addr2line
• bundlephobia
• Wasmphobia
• WebAssembly Debugging Chrome Extensions by Ingvar
• TC39 source maps spec
• Squoosh
• Animal Well
• .kkrieger: Gameplay video and Wikipedia article
• "C64 'fast loaders'"
• "Thank you for playing Wing Commander"

In this episode, Jake and Surma chat about the complexities of adding common framework patterns into the web platform, and work that has been done on that so far.

Resources:

• Michael Jackson's tweet.
• Is WebAssembly magic performance pixie dust? - Surma's investigation into wasm performance.
• defaultValue reflects the value attribute.
• The value property is complicated.
• HTML template instantiation.
• DOM parts API.
• DOM Parts Imperative API.
• DOM Parts Declarative Template API.
• Atomic move for elements.
• Shizo Kanakuri's marathon record