anchor.diff:  List<Point> pixels = [];
   Shape _canvas;
   var createLineStart = false;
  -StreamSubscription touchListener;
  +StreamSubscription touchListener,touchEndListener;
   int totalPoints = 0;
   int CACHE_THRESHOLD = 1000;
   void main() {
  
positive.code: class Arrow extends DisplayObjectContainer{
    Shape lineVector;
    Bitmap head;
    Bitmap body;
    Arrow(){
      mouseEnabled = false;            
      lineVector = new Shape();
  
negative.code:  document.querySelector('#points').text = "Points: ${pixels.length.toString()}";
    canvasBitmapData.draw(_canvas);
    _canvas.graphics.clear();
    if(touchListener!=null){
     touchListener.cancel();
    }
    if(touchEndListener!=null){
     touchEndListener.cancel();
    }
  }
  
  setButtonStateOn(Element target) {
  