anchor.diff:      if (!excludeChildren) {
         for (var i = 0; i < element.visualChildCount; i++) {
           var e = element.getVisualChild(i);
  -        ctx.save();
           _borderElement(ctx, e, false, filter);
  -        ctx.restore();
         }
       }
  -    ctx.restore();
     }
   
     static void _borderElementCore(CanvasRenderingContext2D ctx, PElement element) {
  
positive.code:   }
  
    static void _borderElement(CanvasRenderingContext2D ctx, PElement element, [bool excludeChildren = false, core.Predicate<PElement> filter = null]) {
      ctx.save();
      final tx = element.getTransformToRoot();
      CanvasUtil.transform(ctx, tx);
  
      ctx.lineWidth = 2 / ((tx.scaleX + tx.scaleY) / 2);
  
      if (filter == null || filter(element)) {
        _borderElementCore(ctx, element);
      }
  
negative.code:     } else {
        ctx.strokeStyle = 'orange';
      }
  
      final corners = RetainedUtil.getCorners(element);
  
      ctx.moveTo(corners[3].x, corners[3].y);
      for(final p in corners) {
        ctx.lineTo(p.x, p.y);
      }
    }
  }
  