zh/builder/src/zrender/contain/line.js

/**
 * 线段包含判断
 * @param  {number}  x0
 * @param  {number}  y0
 * @param  {number}  x1
 * @param  {number}  y1
 * @param  {number}  lineWidth
 * @param  {number}  x
 * @param  {number}  y
 * @return {boolean}
 */
export function containStroke(x0, y0, x1, y1, lineWidth, x, y) {
  if (lineWidth === 0) {
    return false;
  }

  var _l = lineWidth;
  var _a = 0;
  var _b = x0; // Quick reject

  if (y > y0 + _l && y > y1 + _l || y < y0 - _l && y < y1 - _l || x > x0 + _l && x > x1 + _l || x < x0 - _l && x < x1 - _l) {
    return false;
  }

  if (x0 !== x1) {
    _a = (y0 - y1) / (x0 - x1);
    _b = (x0 * y1 - x1 * y0) / (x0 - x1);
  } else {
    return Math.abs(x - x0) <= _l / 2;
  }

  var tmp = _a * x - y + _b;

  var _s = tmp * tmp / (_a * _a + 1);

  return _s <= _l / 2 * _l / 2;
}