drafter_finance_engine

The pure, UI-free engine behind drafter_finance — native trading charts for Flutter.

This package has zero Flutter dependency. It does all the hard 80% of a trading chart — scales, viewport math, technical indicators, crosshair hit-testing — and emits a platform-agnostic display list (Scene) of draw primitives in pixel coordinates. A renderer (the drafter_finance package on Flutter, plus the Compose and SwiftUI ports) just walks that list.

Because it's plain Dart, dart test runs the full engine suite with no Flutter toolchain. It is the canonical cross-language spec: the same fixed inputs produce the same indicator arrays and scene shapes in the Kotlin and Swift engines.

What's inside

• Indicators — SMA, EMA, RSI, MACD, Bollinger Bands.
• Scales & viewport — linear scales, padded value ranges, windowing.
• Engines — candlestick, OHLC bar, line, area, baseline, histogram, volume.
• Crosshair — pointer-to-candle snapping and price read-out math.
• Display list — Scene + DrawCommands (line / rect / polyline / fill-path / text) in absolute pixel coordinates.

Usage

import 'package:drafter_finance_engine/drafter_finance_engine.dart';

final rsi = Indicators.rsi(closes, period: 14);
final scene = CandlestickEngine.build(candles, window, plot, style);
// hand `scene` to any renderer

If you're building a Flutter app, depend on drafter_finance instead — it bundles this engine and the CustomPainter widgets.

License

Apache 2.0 — see LICENSE.