geometry_kit_widgets

Flutter widgets for geometry_kit shapes — CustomPainter-backed, styled, and composable.

Quick start

import 'package:flutter/material.dart';
import 'package:geometry_kit/geometry_kit.dart';
import 'package:geometry_kit_widgets/geometry_kit_widgets.dart';

class Demo extends StatelessWidget {
  const Demo({super.key});

  @override
  Widget build(BuildContext context) {
    return GeoCircle.fromGeometry(
      circle: const Circle(radius: 40, center: Point(100, 100)),
      style: const ShapeStyle.stroked(Colors.indigo, width: 2),
      size: const Size(200, 200),
    );
  }
}

Two ways to render

Standalone — each Geo* widget owns its own CustomPaint. Drop into any layout:

Column(children: [
  GeoCircle(radius: 30, ...),
  Text('label'),
  GeoTriangle(...),
])

Multi-shape GeometryCanvas — share a single paint pass across many shapes (cheaper, layered, unified hit-testing in later phases):

GeometryCanvas(
  size: const Size(400, 300),
  shapes: [
    StyledShape(
      Circle(center: Point(100, 100), radius: 50),
      style: const ShapeStyle.filled(Colors.blue),
    ),
    StyledShape(
      Triangle(Point(200, 50), Point(300, 200), Point(150, 200)),
      style: const ShapeStyle.stroked(Colors.red, width: 2),
    ),
  ],
)

Both paths use the same painter classes — pick whichever fits the layout.

Phase 1 widgets

Widget	Geometry
`GeoCircle`	`Circle`
`GeoEllipse`	`Ellipse`
`GeoRectangle`	`Rectangle`
`GeoTriangle`	`Triangle`
`GeoQuadrilateral`	`Quadrilateral`
`GeoPolygon`	`Polygon`
`GeoLine`	`Line`

Each widget exposes two constructors: a flat one (build geometry from primitives) and .fromGeometry (pass an existing geometry instance).

Styling

ShapeStyle bundles fill, stroke, opacity, dash pattern, cap, and join into one immutable object:

const ShapeStyle();                                  // 1px black stroke
const ShapeStyle.filled(Colors.indigo);              // solid fill
const ShapeStyle.stroked(Colors.red, width: 3);      // 3px red stroke
const ShapeStyle(
  fillColor: Colors.blue,
  strokeColor: Colors.indigo,
  strokeWidth: 2,
  opacity: 0.7,
  dashPattern: DashPattern([8, 4]),
);

Theming

Wrap a subtree in ShapeStyleTheme to share a default style:

ShapeStyleTheme(
  data: const ShapeStyle.stroked(Colors.teal, width: 2),
  child: Column(children: [
    GeoCircle(radius: 30),       // teal stroke
    GeoTriangle(...),            // teal stroke
    GeoLine(..., style: const ShapeStyle.stroked(Colors.red)), // override
  ]),
)

Resolution order: explicit style → closest ShapeStyleTheme ancestor → default 1px black stroke.

Coordinate mapping

Default = Flutter native (top-left origin, Y-down). Inject a CoordinateMapper for math conventions:

GeoCircle(
  radius: 30,
  mapper: CoordinateMapper.yUp(const Size(200, 200)),
  size: const Size(200, 200),
)

// Origin at the canvas center, Y-up:
GeometryCanvas(
  size: const Size(400, 300),
  mapper: CoordinateMapper.centered(const Size(400, 300)),
  shapes: [...],
)

Built-in mappers: identity, yUp(size), centered(size, {yUp = true}).

Clipping & layering

Every Geo* widget and GeometryCanvas accepts clipBehavior (default Clip.hardEdge). Shapes that extend past size are clipped to widget bounds — they don't bleed onto neighbors. Set Clip.none to allow overflow.

GeoCircle(
  radius: 120,
  size: const Size(80, 80),
  clipBehavior: Clip.none,    // circle draws outside the 80x80 box
)

GeometryCanvas defaults to backgroundColor: null (transparent) so widgets stacked underneath remain visible.

Other features

Semantics(label: ...) baked into every widget for accessibility.
RepaintBoundary wraps every CustomPaint to keep nearby state changes from forcing a full repaint.
Dash patterns are drawn via shared PathMetrics helper — no extra dependency.

Roadmap

Phase 2: tap/hover interactivity, GeoArc, GeoRing, GeoCapsule, GeoBezierCurve, GeoSpline, GeoPolyline, GeoRay, GeometryCanvas hit-testing.
Phase 3: drag, grid + axes overlay, debug parameters (showBoundingBox, showCenter, showVertices).
Phase 4: tooltips, image export, dark mode presets.