public override int DetectHandle(BaseObject op, BaseDraw bd, int x, int y, QUALIFIER qualifier)
 {
     if (0 != (qualifier & QUALIFIER.QUALIFIER_CTRL))
         return -1;
     double4x4 mg = op.GetMg();
     if (bd.PointInRange(mg * GetRTHandle(op,0),x,y))
         return 0; // OK
     return -1; // Not OK
 }