ChartForge

A zero-dependency, no-build-step financial charting engine for Canvas 2D — with the drawing-tools layer the fast engines don't ship.

TradingView's excellent Lightweight Charts deliberately ships no drawing tools, no indicator UI, and no navigator — and most libraries that do ship them are paid or branded. ChartForge aims at the unoccupied corner: Lightweight-class performance plus the drawing/tools layer, Apache-2.0, zero dependencies, plain ES modules (edit-file → refresh; there is no bundler and never will be).

Measured, not asserted

The repo ships its own benchmark harness (bench/) comparing ChartForge to a vendored Lightweight Charts v5 on identical seeded data. Headless-chromium results, 2026-07-13 (PC / iPad Pro 11 / iPhone 13 emulation; 10K daily candles + volume, and 30K intraday):

metric	ChartForge	Lightweight v5
pan fps (all six device×size cells)	60.0–60.5	60.0–60.2
first paint	14–31 ms	50–87 ms
worst frame	16.8 ms	16.8 ms

Open bench/index.html and press the buttons — the harness re-measures in your browser. Claims that can't be reproduced don't belong in a README.

What's inside

• engine/ — 8 ES modules, ~32KB unminified, zero deps:
  • SoA Float64Array series buffers (no per-point objects)
  • index-space time scale (bar index ↔ px; timestamps only at the axis labeler — gaps/sessions/mixed granularity come free)
  • linear · log · percent price scales with nice ticks
  • three stacked canvases per pane, layer-selective dirty redraw
  • per-style path batching; sub-pixel bars collapse to 1px ticks, sub-pixel lines decimate to per-column min/max
  • pointer-unified pan with velocity-tracked inertia, wheel/pinch anchor zoom, double-tap fit, tap-hold crosshair
  • a pane manager (shared time scale, synced crosshair) and a primitive API (draw(ctx, viewport) / hitTest(pt) / serialize()) for overlays and tools
• tools/drawings.js — the drawing families as adapter-free geometry over the primitive API: trend/ray/h/v lines, parallel channel, pitchfork, Gann fan, Fibonacci retracement/extension, rectangle, ellipse, polyline, text, measure-with-stats, and long/short position tools with R:R readout
• demo/ — a static 10K-candle demo (no server, no data feed — seeded synthetic bars)
• bench/ — the harness above (the LW v5 reference is vendored here for benching only, Apache-2.0, cross-vendor hash in bench/vendor/PROVENANCE.md)

Quick start

<div id="chart" style="height:420px"></div>
<script type="module">
  import { createChart } from "./engine/index.js";
  const chart = createChart(document.getElementById("chart"), { theme: "dark" });
  const volPane = chart.addPane(0.2);
  chart.addSeries("candles", { pane: 0 }).setData(bars);   // [{time,open,high,low,close,volume},…]
  chart.addSeries("volume", { pane: volPane }).setData(bars);
</script>

The engine consumes plain OHLCV arrays. Where the data comes from — your server, a CSV, a websocket — is your adapter's business; the engine has no opinions and no network code.

Scope & maintenance policy (read before filing)

This is a working tool extracted from a private trading-research platform, maintained as time permits. Bug reports and focused PRs are welcome; the feature roadmap is ours. No support SLA. If maintenance cost ever exceeds its value, the repo will be archived with honor rather than left to rot — you'll always be able to fork it.

License

Apache-2.0 (see LICENSE). The benched Lightweight Charts v5 copy in bench/vendor/ is © TradingView, Apache-2.0, used solely as the performance reference.