public static void paintDuplicateNodesBackground(Graphics g, JTree tree) {
    Rectangle clipBounds = g.getClipBounds();
    int start = tree.getClosestRowForLocation(clipBounds.x, clipBounds.y);
    int end = Math.min(tree.getRowCount(), tree.getClosestRowForLocation(clipBounds.x+clipBounds.width, clipBounds.y+clipBounds.height)+1);
    Color old = g.getColor();
    for (int i = start; i < end; i++) {
      TreePath path = tree.getPathForRow(i);
      if (path == null) continue;
      DefaultMutableTreeNode node = (DefaultMutableTreeNode)path.getLastPathComponent();
      Rectangle accumRect = null;
      TreePath accumPath = null;
      while (node != null) {
        Object userObject = node.getUserObject();
        if (!(userObject instanceof DuplicatableNode duplicatableNode)) break;
        Object duplicate = duplicatableNode.getDuplicate();
        if (duplicate == null) break;
        accumPath = accumRect == null ? path : accumPath.getParentPath();
        accumRect = union(tree.getPathBounds(accumPath), accumRect);
        node = (DefaultMutableTreeNode)node.getParent();
      }
      if (accumRect != null) {
        Rectangle rowRect = tree.getRowBounds(tree.getRowForPath(accumPath));
        accumRect = accumRect.intersection(new Rectangle(rowRect.x, rowRect.y, Integer.MAX_VALUE, Integer.MAX_VALUE));

        //unite all expanded children node rectangles since they can stretch out of parent's
        node = (DefaultMutableTreeNode)accumPath.getLastPathComponent();
        accumRect = union(accumRect, getExpandedNodesRect(tree, node, accumPath));

        g.setColor(Gray._230);
        g.fillRoundRect(accumRect.x, accumRect.y, accumRect.width, accumRect.height, 10, 10);
        g.setColor(Color.lightGray);
        g.drawRoundRect(accumRect.x, accumRect.y, accumRect.width, accumRect.height, 10, 10);
      }
    }
    g.setColor(old);
  }
public static void paintDuplicateNodesBackground(Graphics g, JTree tree)