worker-visualizer

# Worker Visualizer Skill Produce a single self-contained `index.html` that moves heavy per-frame compute into a Web Worker and renders the result to a canvas, keeping the main thread at a smooth 60fps. ## Why this is a powered artifact OpenDesign detects `new Worker(` / `SharedArrayBuffer` / `OffscreenCanvas` and renders this file in **powered preview** — a cross-origin-isolated iframe with `allow-same-origin`. That means external and blob Web Workers construct successfully, `SharedArrayBuffer` is defined (`crossOriginIsolated === true`), and `importScripts` works. In the old opaque sandbox all three failed; here they just work. ## Resource map ``` worker-visualizer/ ├── SKILL.md ← you're reading this └── example.html ← a working 12k-particle SharedArrayBuffer sim (READ FIRST) ``` ## Workflow ### Step 0 — Read the reference Read `example.html`. Note the split: the worker integrates positions each tick; the main thread only reads + draws. It feature-detects `crossOriginIsolated` and uses a `SharedArrayBuffer` for zero-copy when available, falling back to a transferable `postMessage` copy otherwise. Always ship that fallback so the artifact still animates if isolation is off. ### Step 1 — Choose the workload Pick ONE compute-bound job worth offloading: - **Particle / N-body field** (default): thousands of bodies with a cheap force law. - **Fractal**: Mandelbrot/Julia escape-time into an `ImageData` buffer. - **Cellular automata / reaction-diffusion**: grid updated in the worker. - **Data/audio visualizer**: transform a stream into bars/rings each frame. ### Step 2 — Build `index.html` - **One file, zero external requests.** Build the worker from a `Blob` + `URL.createObjectURL` (inline its source), or embed it as a `data:` URL. - **Prefer SharedArrayBuffer** for large per-frame state: allocate on the main thread, pass the `SharedArrayBuffer` to the worker, and read the same `Float32Array`/`Uint8ClampedArray` view while drawing. Guard on `typeof SharedArrayBuffer !== 'undefined' && crossOriginIsolated`. - **Fallback path**: if not isolated, `postMessage` a transferable `ArrayBuffer` each frame. - Consider `OffscreenCanvas` + `canvas.transferControlToOffscreen()` to render inside the worker for the heaviest scenes. ### Step 3 — Overlay + brand - HUD with the title and 2–3 live stat tiles (particle count, transport mode, fps). Map accent color to the active DESIGN.md when present; otherwise a dark ground with one vivid accent. ### Step 4 — Self-review (P0) - [ ] Worker constructs with no SecurityError; sim runs. - [ ] Main-thread render holds ~60fps under the full workload. - [ ] `SharedArrayBuffer` path engages when `crossOriginIsolated` is true; `postMessage` fallback engages otherwise — verify BOTH branches degrade cleanly. - [ ] No unbounded growth: velocities/positions stay stable over minutes. - [ ] The "Transport" stat truthfully reports which path is live.