DisplayListExplorer

DisplayList Explorer converts a SwiftUI DisplayList.description S-expression into its compact minimalDescription form, links source elements to their encodings, and explains every token.

The parser and converter are written in Swift. JavaScriptKit compiles the browser executable to WebAssembly, CodeMirror provides the source editor and range decorations, Vite packages the static assets, and GitHub Actions deploys the result to GitHub Pages.

Features

• Converts content, effects, nested flattened lists, effect children, and state variants.
• Reconstructs a readable DisplayList.description from minimalDescription.
• Reproduces the single-line formatting emitted by SExpPrinter.
• Links source and minimalDescription ranges with bidirectional hover highlighting.
• Provides dedicated minimalDesc, encoding info, and occurrence statistics tabs.
• Highlights every matching source range when a statistics row is hovered or focused.
• Runs entirely in the browser; pasted descriptions are not uploaded.
• Tests the conversion engine natively with SwiftPM before every deployment.

Reverse conversion

The direction control can use the current output as the next input. Because minimalDescription intentionally omits rendering details, reconstructed descriptions mark an unknown scalar or identifier with ? and an unrecoverable payload or effect kind with *. Converting the reconstructed description forward again preserves the original minimalDescription.

The mapping follows OpenSwiftUI's DisplayListPrinter.swift, audited for SwiftUI 6.5.4. The interaction model is inspired by SwiftFiddle/swiftregex. The CodeMirror decoration and statistics interaction patterns are adapted from SwiftFiddle/swift-ast-explorer; see THIRD_PARTY_NOTICES.md.

Known ambiguity

DisplayList.description prints identity effects, empty property effects, and platform effects with the same empty (effect …) form, while minimalDescription encodes them differently. Because the source text has already discarded that distinction, the converter renders an empty effect as identity and calls out the ambiguity in the interface.

Local development

Prerequisites:

• Swift 6.2.3 with its matching WebAssembly SDK
• A matching wasm32-unknown-wasip1 Swift SDK
• Node.js 24 or newer

Build the Swift package for WebAssembly, install the web dependencies, and start Vite:

swift package --swift-sdk "$SWIFT_SDK_ID" js
npm ci
npm run dev

Opening index.html through a file:// URL cannot run the ES Module and WebAssembly bundle. To build with the GitHub Pages base path and launch the production preview in one step, run:

npm run preview

Then open http://127.0.0.1:4173/DisplayListExplorer/.

Run the native converter tests with:

swift test

GitHub Pages

The Pages workflow deploys every push to main and can also be run manually from any branch through workflow_dispatch. It tests the converter, builds the SwiftWasm package, bundles the site with the repository's Pages base path, and deploys the dist artifact to https://openswiftuiproject.github.io/DisplayListExplorer/.

License

DisplayList Explorer is available under the MIT License. Third-party attributions are listed in THIRD_PARTY_NOTICES.md.