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Hit Testing and Editing

BezierPath is more than a serialization container. It also carries enough information to support editing-oriented lookup.

Segment marks

Before appending the path data for a logical spline segment, Spline.Render() calls BezierPath.Mark(i).

That means HitTest() can report not only a distance, but also the originating segment index through BestMark.

Approximate hit testing

BezierPath.HitTest(x, y):

• evaluates line segments analytically
• subdivides cubic segments into short line segments
• tracks the best distance and the currently active mark

This approximation is sufficient for:

• selecting nearby spans
• inserting knots into an existing path
• estimating deviation in freehand trace refinement

DemoSpline usage

DemoSpline uses this workflow to decide where pointer interaction should land on a rendered curve, even though the reusable package itself stays UI-free.