code: void copyTo(TouchState target) {
          target.clear();
          for (int i = 0; i < pointCount; i++) {
              target.addPoint(points[i]);
          }
          target.primaryID = primaryID;
          target.window = window;
      }
docs: Copies the contents of this state object to another.
  
  @param target The TouchState to which to copy this state's data.