dagre-d3-es/src/dagre-js/intersect/intersect-ellipse.js

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export { intersectEllipse };

function intersectEllipse(node, rx, ry, point) {
  // Formulae from: http://mathworld.wolfram.com/Ellipse-LineIntersection.html

  var cx = node.x;
  var cy = node.y;

  var px = cx - point.x;
  var py = cy - point.y;

  var det = Math.sqrt(rx * rx * py * py + ry * ry * px * px);

  var dx = Math.abs((rx * ry * px) / det);
  if (point.x < cx) {
    dx = -dx;
  }
  var dy = Math.abs((rx * ry * py) / det);
  if (point.y < cy) {
    dy = -dy;
  }

  return { x: cx + dx, y: cy + dy };
}