Minimal Rust + WASM library for Figma‑style vector networks (undirected graphs) targeting the browser.

It exposes a small API to JavaScript for creating a graph, connecting nodes, listing neighbors, and computing shortest paths (BFS).

# 1) Prereqs
rustup target add wasm32-unknown-unknown
cargo install wasm-pack

# 2) Build the WASM bundle (from contour-wasm/)
# outputs to ../pkg so the web demo can import it
cd contour-wasm && wasm-pack build --target web --out-dir ../pkg && cd -

# 3) Serve statically (from repo root)
python3 -m http.server

# 4) Open the demo in your browser
# visit http://localhost:8000/web/index.html

This produces a pkg/ folder with JS/WASM bindings that the demo imports.

• Rust toolchain
• Target wasm32-unknown-unknown: rustup target add wasm32-unknown-unknown
• wasm-pack (recommended): cargo install wasm-pack

From the workspace contour-wasm/ crate:

wasm-pack build --target web --out-dir ../pkg

This creates a pkg/ folder with JS/WASM bindings.

WASM unit tests are written with wasm-bindgen-test under tests/.

Run in a headless browser (requires Chrome or Firefox installed). Run from the contour-wasm/ crate directory:

# Chrome (from contour-wasm/)
cd contour-wasm && wasm-pack test --headless --chrome && cd -

# or Firefox
cd contour-wasm && wasm-pack test --headless --firefox && cd -

You can also run them in a non-headless browser by omitting --headless.

For production, prefer the strict *_res methods which validate inputs and never panic. They return a Result-like object:

• { ok: true, value: T } on success
• { ok: false, error: { code, message, data? } } on failure

See docs/errors.md for error codes and invariants. A minimal TypeScript declaration is provided at contour-wasm/types.d.ts.

Serve the folder via any static file server (so the browser can fetch the WASM file). For example, from contour/:

python3 -m http.server
# or use any other static server

Then open http://localhost:8000/web/index.html.

Demo controls:

• Import SVG: click "Import SVG" or drag-and-drop a .svg onto the canvas. The demo parses all <path d> commands (M/L/C/Z) and imports them into the graph.
• Save/Load: persists the current graph to localStorage.
• Clear: removes all nodes and edges.
• Bucket (F): toggles region fills.
• Bend (B): drag directly on a curve to bend.

• new Graph()
• graph.add_node() -> number
• graph.add_edge(a: number, b: number) -> boolean
• graph.node_count() -> number
• graph.edge_count() -> number
• graph.neighbors(id: number) -> number[] | null
• graph.shortest_path(start: number, goal: number) -> number[] | null
• graph.add_svg_path(d: string) -> number (append path data; supports M/L/C/Z)
• graph.to_svg_paths() -> string[] (export independent path fragments)
• graph.get_regions() -> [{ key, area, filled, color?: [r,g,b,a], points[] }]
• graph.toggle_region(key: number) -> boolean
• graph.set_region_fill(key: number, filled: boolean)
• graph.set_region_color(key: number, r: number, g: number, b: number, a: number)

Strict variants (examples):

• graph.add_node_res(x, y) -> { ok|error }
• graph.move_node_res(id, x, y) -> { ok|error }
• graph.add_edge_res(a, b) -> { ok|error }
• graph.set_handle_pos_res(id, end, x, y) -> { ok|error }
• graph.bend_edge_to_res(id, t, tx, ty, stiffness) -> { ok|error }
• graph.pick_res(x, y, tol) -> { ok: true, value: null | Pick }
• graph.add_svg_path_res(d) -> { ok|error }
• Full list in contour-wasm/types.d.ts.

• graph.add_freehand(points: Float32Array, close: boolean) -> Uint32Array
  • Fits a smooth cubic Bezier chain (Catmull–Rom with corner detection) through sampled points.
  • Intended for the Pen → Free Draw mode in the demo.

• The crate is built as a cdylib for WebAssembly and uses wasm-bindgen for bindings.
• The simple web demo imports from ./pkg/contour_wasm.js, which is created by building the contour-wasm crate.
• JSON to_json now includes version and fills arrays; from_json reads them.
• Robustness: editing operations clamp parameters and treat degenerate inputs as no-ops. Internals avoid panics under zero-length edges, coincident endpoints, and tiny faces. See docs/epsilons.md for the centralized tolerance policy.