1. override
DisplayObject hitTestInput(num localX, num localY)

Evaluates this display object to see if the coordinates localX and localY are inside this display object.

If the coordinates are inside, this display object is returned; null otherwise.

localX and localY are relative to to the origin (0,0) of this display object (local coordinates).

Source 

@override
DisplayObject hitTestInput(num localX, num localY) {

  for (int i = 0; i < ixList.length - 2; i += 3) {

    int i1 = ixList[i + 0] << 2;
    int i2 = ixList[i + 1] << 2;
    int i3 = ixList[i + 2] << 2;

    num x1 = vxList[i1 + 0];
    num y1 = vxList[i1 + 1];
    num x2 = vxList[i2 + 0];
    num y2 = vxList[i2 + 1];
    num x3 = vxList[i3 + 0];
    num y3 = vxList[i3 + 1];

    if (localX < x1 && localX < x2 && localX < x3) continue;
    if (localX > x1 && localX > x2 && localX > x3) continue;
    if (localY < y1 && localY < y2 && localY < y3) continue;
    if (localY > y1 && localY > y2 && localY > y3) continue;

    num vx1 = x3 - x1;
    num vy1 = y3 - y1;
    num vx2 = x2 - x1;
    num vy2 = y2 - y1;
    num vx3 = localX - x1;
    num vy3 = localY - y1;

    num dot11 = vx1 * vx1 + vy1 * vy1;
    num dot12 = vx1 * vx2 + vy1 * vy2;
    num dot13 = vx1 * vx3 + vy1 * vy3;
    num dot22 = vx2 * vx2 + vy2 * vy2;
    num dot23 = vx2 * vx3 + vy2 * vy3;

    num u = (dot22 * dot13 - dot12 * dot23) / (dot11 * dot22 - dot12 * dot12);
    num v = (dot11 * dot23 - dot12 * dot13) / (dot11 * dot22 - dot12 * dot12);

    if ((u >= 0) && (v >= 0) && (u + v < 1)) return this;
  }

  return null;
}