Function isPointInPolygon

packages/react-aria/src/tooltip/useSafeArea.ts:155–169

(point: Point, polygon: Point[])

// Ray casting point-in-polygon test.
function isPointInPolygon(point: Point, polygon: Point[]): boolean {
  let {x, y} = point;
  let inside = false;
  for (let i = 0, j = polygon.length - 1; i < polygon.length; j = i++) {
    let xi = polygon[i].x;
    let yi = polygon[i].y;
    let xj = polygon[j].x;
    let yj = polygon[j].y;
    let intersect = yi > y !== yj > y && x < ((xj - xi) * (y - yi)) / (yj - yi) + xi;
    if (intersect) {
      inside = !inside;
    }
  }
  return inside;
}