API Reference

`CurveBuilder`

Creates one reusable curve shape. A shape may contain multiple closed contours.

Method	Description
`new CurveBuilder()`	Creates an empty builder.
`moveTo(x, y)`	Starts a contour. The preceding contour must be closed.
`lineTo(x, y)`	Adds a straight segment.
`quadraticCurveTo(cpx, cpy, x, y)`	Adds a quadratic Bézier segment.
`bezierCurveTo(cp1x, cp1y, cp2x, cp2y, x, y)`	Adds a cubic Bézier segment.
`ellipticArcTo(x, y, radiusX, radiusY, rotation, startAngle, sweepAngle)`	Adds an elliptic arc. Angles are in radians.
`addEllipse(x, y, radiusX, radiusY, rotation, clockwise)`	Adds a complete ellipse as a new closed contour.
`closeContour()`	Closes the active contour.
`build()`	Returns `CurveGeometry` and resets the builder after success.

`CurveGeometry`

Stores one or more curve shapes in WebAssembly memory.

Member	Description
`shapeCount`	Number of shapes.
`contourCount`	Total number of contours.
`segmentCount`	Total number of curve segments.
`toData()`	Converts the geometry to ordinary typed JavaScript data.

The toData() result has the following structure:

type CurvePoint = [number, number];

type CurveSegmentData =
    | { type: 'line'; to: CurvePoint }
    | { type: 'quad'; ctrl: CurvePoint; to: CurvePoint }
    | {
          type: 'cubic';
          ctrl0: CurvePoint;
          ctrl1: CurvePoint;
          to: CurvePoint;
      }
    | { type: 'arc'; arc: RationalArcData };

type CurveContourData = {
    start: CurvePoint;
    segments: CurveSegmentData[];
};

type CurveShapeData = CurveContourData[];
type CurveShapesData = CurveShapeData[];

Arc data contains its ellipse metadata, angles, rational quadratic control points, and weights. The control points and weights are the authoritative geometry.

`CurveOverlay`

Represents a single Boolean or subject-resolving operation.

Method	Description
`new CurveOverlay(subject, clip)`	Creates an operation with automatic scaling.
`CurveOverlay.fromSubject(subject)`	Creates an operation for `resolveSubject()`.
`CurveOverlay.withScale(subject, clip, scale)`	Creates an operation with an explicit conversion scale.
`setApproximation(options)`	Configures curve approximation before execution.
`scale()`	Returns the effective conversion scale.
`conversionReport()`	Reports collapsed or linearized input geometry.
`overlay(overlayRule, fillRule)`	Runs a Boolean operation and returns `CurveGeometry`.
`resolveSubject(fillRule)`	Resolves the subject using the selected fill rule.

overlay() and resolveSubject() consume the operation. Calling an operation method again on the same instance throws an error.

Approximation options

type CurveApproximationOptions = {
    minChordLength?: number;
    angleTolerance?: number; // range: (0, 1], default: 0.125
    maxDepth?: number;       // range: 0...16, default: 16
};

Options are optional and may be supplied independently. minChordLength must be a finite positive number when present.

Conversion report

type CurveConversionReport = {
    contourCount: number;
    collapsedContourCount: number;
    collapsedSegmentCount: number;
    linearizedArcCount: number;
    hasDegeneracies: boolean;
};

type CurveOverlayConversionReport = {
    subject: CurveConversionReport;
    clip?: CurveConversionReport;
    hasDegeneracies: boolean;
};

Rules

Use the existing OverlayRule values (Subject, Clip, Intersect, Union, Difference, InverseDifference, or Xor) and FillRule values (EvenOdd, NonZero, Positive, or Negative).

Keyboard shortcuts

iShape