Function insidePolygon

d3-3.2.8/d3.js:2932–2946

(p)

        return i;
      }
      function insidePolygon(p) {
        var wn = 0, n = polygon.length, y = p[1];
        for (var i = 0; i < n; ++i) {
          for (var j = 1, v = polygon[i], m = v.length, a = v[0], b; j < m; ++j) {
            b = v[j];
            if (a[1] <= y) {
              if (b[1] > y && isLeft(a, b, p) > 0) ++wn;
            } else {
              if (b[1] <= y && isLeft(a, b, p) < 0) --wn;
            }
            a = b;
          }
        }
        return wn !== 0;
      }
      function isLeft(a, b, c) {
        return (b[0] - a[0]) * (c[1] - a[1]) - (c[0] - a[0]) * (b[1] - a[1]);
      }