                                constant: 0).isActive = true
         }
         
+        maskLayer.colors = [
+            UIColor.clear.cgColor,
+            UIColor.white.cgColor,
+            UIColor.white.cgColor,
+            UIColor.clear.cgColor,
+        ]
+        maskLayer.startPoint = CGPoint(x: 0.5, y: 0)
+        maskLayer.endPoint   = CGPoint(x: 0.5, y: 1)
+        layer.mask = maskLayer
     }
     
     override init(frame: CGRect) {

        case .bottom:
            tableView.contentInset = UIEdgeInsets(top: inset * 2, left: 0, bottom: 0, right: 0)
        }
    }
    
    public override func didMoveToSuperview() {

        }
        
        /// find out index of current line
        var lineIndex = -1
        if currentLineIndex >= 0 && isCurrentLine(lineIndex: currentLineIndex) {
            lineIndex = currentLineIndex
        } else {
