@hemicycle/vanilla

Framework-free SVG renderer for parliament-style hemicycle seat charts.

@hemicycle/vanilla wraps @hemicycle/core with a lightweight rendering layer that writes directly into an <svg> element — no framework, no bundler magic required. Pass it a config, call render(), and get a fully drawn hemicycle.

Features

• Direct SVG rendering — writes <path> elements into any SVGSVGElement you provide
• Three seat shapes — arc (default), rect, and circle
• Per-seat styling — override color, shape, and border radius on individual seats via seatConfig
• Hide empty seats — optionally omit unoccupied seats for sparse layouts
• All @hemicycle/core options — full access to rows, radii, aisles, mirroring, and ordering
• TypeScript-first — fully typed with ESM and CJS dual output

Installation

npm install @hemicycle/vanilla

@hemicycle/core is a peer dependency and is included automatically.
Requires Node.js ≥ 18 and a DOM environment (browser or jsdom).

Quick Start

<svg id="hemicycle"></svg>

import { Hemicycle } from "@hemicycle/vanilla";

const hemicycle = new Hemicycle({
  rows: 7,
  totalSeats: 577,
  innerRadius: 40,
  outerRadius: 95,
  width: 800,
  height: 420,
});

const svg = document.getElementById("hemicycle") as SVGSVGElement;
hemicycle.render(svg);

API

new Hemicycle(config)

Creates a new renderer. Accepts all @hemicycle/core config options plus the following:

SeatConfig

hemicycle.render(svg)

Clears the target <svg> element and renders all seats into it. Also sets viewBox, width, and height attributes automatically.

hemicycle.render(document.querySelector("svg")!);

hemicycle.updateData(data)

Attaches seat data and computes per-seat paths. Each item must identify a seat by idx or by { rowIndex, seatIndex }, and may include a seatConfig to override the default style for that seat.

hemicycle.updateData([
  { idx: 0, party: "Left", seatConfig: { color: "#e63946" } },
  { idx: 1, party: "Center", seatConfig: { color: "#457b9d" } },
]);

hemicycle.render(svg);

Data items without a seatConfig inherit the global config. The seatConfig field is optional — omit it to use the global default.

hemicycle.updateConfig(config)

Applies a partial config update. Call render() again afterward to redraw.

Other accessors

Examples

Coloring seats by party

const hemicycle = new Hemicycle({
  rows: 7,
  totalSeats: 577,
  seatConfig: { color: "#ddd", shape: "arc" },
});

hemicycle.updateData(
  members.map((m) => ({
    idx: m.seatNumber,
    seatConfig: { color: m.partyColor },
  })),
);

hemicycle.render(document.querySelector("#parliament")!);

Hiding unoccupied seats

const hemicycle = new Hemicycle({
  rows: 5,
  totalSeats: 100,
  hideEmptySeats: true,
});

hemicycle.updateData(occupiedSeats); // Only these will be drawn
hemicycle.render(svg);

Circular seats with custom radius

const hemicycle = new Hemicycle({
  rows: 6,
  totalSeats: 200,
  seatConfig: {
    shape: "circle",
    radius: 2.5,
    color: "#adb5bd",
  },
});

Reactive updates

const hemicycle = new Hemicycle({ rows: 5, totalSeats: 50 });
hemicycle.render(svg);

// On user interaction, update data and re-render:
button.addEventListener("click", () => {
  hemicycle.updateData(newData);
  hemicycle.render(svg); // cleanUp() is called automatically
});

Seat Shapes

Related

• @hemicycle/core — layout engine (no rendering)

Contributing

Bug reports and pull requests are welcome on GitHub.

Support

• Issues: GitHub Issues
• Source: github.com/GabrielVidal1/hemicycle

Maintainer

Gabriel Vidal — gvidalayrinhac@gmail.com

License

MIT