@osionos/draw-engine

Canvas2D drawing engine (Excalidraw / Figma class): scene model, dirty-driven rAF renderer, camera, tools, bindings.

The core lives in Rust (crates/draw-engine), compiled to WASM. TypeScript is host glue only — React/Svelte/vanilla bind a canvas; they do not own the scene. No compile-time or paint speedup is claimed without a measured artifact (see Timings).

Adapters (hexagonal)

react/DrawCanvas.tsx  ──┐
svelte/DrawCanvas.svelte ─┼──► host/bindCanvas ──► WASM DrawEngine
vanilla bindCanvas()  ──┘

• crates/draw-engine — camera, scene, geometry, edit, history, JSON/SVG, paint loop
• src/host/** — one bind primitive: pointer, keyboard (dispatchKeyDown), resize
• src/react/DrawCanvas.tsx — shipped public component (import { DrawCanvas } from "@osionos/draw-engine")
• src/svelte/DrawCanvas.svelte — additive (import { DrawCanvas } from "@osionos/draw-engine/svelte")
• src/index.ts — public TS contract (types, DrawEngine, DrawCanvas, .osidraw)

DrawCanvas calls loadDrawEngine() on mount (WASM init is async). Vanilla hosts must await loadDrawEngine() before new DrawEngine / bindCanvas, or use bindCanvasAsync.

React stays on the barrel because osionos (and any existing host) imports DrawCanvas from @osionos/draw-engine. Deleting it is a public-surface break.

Toolchain

pnpm only (packageManager: pnpm@10.32.1). npm/yarn are rejected at install. Scripts self-Dockerize; host Node/Rust is not required.

make help      # targets
make test      # cargo test + host node:test in Docker
make quality   # rustfmt, clippy -D warnings, cargo test, host node:test
make wasm      # wasm-bindgen build into pkg/
make lock      # regenerate pnpm-lock.yaml in Docker
make shell     # container shell
make clean     # containers, volumes, local image

Equivalent: pnpm test / pnpm quality (both call scripts/docker-run.sh).

Tests:

• crates/draw-engine/tests/draw_engine.rs — camera, scene, geometry, handles, history, json/svg
• crates/draw-engine/tests/draw_edit.rs — clipboard, z-order, align, flip, group, snap
• crates/draw-engine/tests/draw_binding.rs — connectors, bindings, labels
• src/host/keys.test.ts — host keyboard chords

Playwright specs (drawEditing.spec.mjs, drawDiagram.spec.mjs) stay in osionos: they drive the app UI, not the engine. osionos still vendors a copy at packages/draw-engine; switching the consumer alias is a follow-up.

Timings (measured, not claimed)

Recorded on this machine after the WASM cutover. These are not a speedup claim versus the old TypeScript core (that path had no compile step — node --experimental-strip-types).

Command	Wall time
cargo test --workspace (warm cache)	~0.4s
cargo test --workspace (rebuild crate in Docker, crates.io already cached)	~9.3s compile + test
cargo build --release --target wasm32-unknown-unknown (warm cache)	~0.2s
cargo build --release --target wasm32-unknown-unknown (incremental after WASM API change)	~3.2s
src/host/**/*.test.ts (node:test)	~0.3s

quality.sh --with-tests --no-audit is green (rustfmt, clippy, shellcheck, make test). npm audit is skipped: this package is pnpm-only and has no package-lock.json. Paint vs the deleted TS engine is not measured here: a naive WASM stroke/fill is a hop into JS, so runtime can be slower until profiled on a canvas. Do not advertise “faster” without that artifact.