code: ///////////////////////////////////////////////////////////////////////////////////////////////
  // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
  // Copyright (C) 2001-2023 the original author or authors.
  //
  // This library is free software; you can redistribute it and/or
  // modify it under the terms of the GNU Lesser General Public
  // License as published by the Free Software Foundation; either
  // version 2.1 of the License, or (at your option) any later version.
  //
  // This library is distributed in the hope that it will be useful,
  // but WITHOUT ANY WARRANTY; without even the implied warranty of
  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  // Lesser General Public License for more details.
  //
  // You should have received a copy of the GNU Lesser General Public
  // License along with this library; if not, write to the Free Software
  // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  ///////////////////////////////////////////////////////////////////////////////////////////////
  
  package com.puppycrawl.tools.checkstyle.gui;
  
  import java.awt.Component;
  import java.awt.Graphics;
  
  import javax.swing.JTable;
  import javax.swing.JTree;
  import javax.swing.UIManager;
  import javax.swing.table.TableCellRenderer;
  import javax.swing.tree.DefaultTreeCellRenderer;
  import javax.swing.tree.TreeCellRenderer;
  import javax.swing.tree.TreeModel;
  
  /**
   * A TreeCellRenderer that displays a JTree.
   */
  class TreeTableCellRenderer extends JTree implements
          TableCellRenderer {
  
      /**
       * Serial ID.
       */
      private static final long serialVersionUID = 4324031590789321581L;
  
      /** The text color for selected cells. */
      private static final String COLOR_KEY_TABLE_SELECTION_FOREGROUND = "Table.selectionForeground";
  
      /** The background color for selected cells. */
      private static final String COLOR_KEY_TABLE_SELECTION_BACKGROUND = "Table.selectionBackground";
  
      /** The background color for table. */
      private static final String COLOR_KEY_TABLE_BACKGROUND = "Table.background";
  
      /** Tree table to render. */
      private final TreeTable treeTable;
  
      /** Last table/tree row asked to render. */
      private int visibleRow;
  
      /**
       * Creates a new instance.
       *
       * @param treeTable tree table to render.
       * @param model Tree model.
       */
      /* package */ TreeTableCellRenderer(TreeTable treeTable, TreeModel model) {
          super(model);
          this.treeTable = treeTable;
      }
  
      /**
       * UpdateUI is overridden to set the colors of the Tree's renderer
       * to match that of the table.
       */
      @Override
      public void updateUI() {
          super.updateUI();
          // Make the tree's cell renderer use the table's cell selection
          // colors.
          final TreeCellRenderer tcr = getCellRenderer();
          if (tcr instanceof DefaultTreeCellRenderer) {
              final DefaultTreeCellRenderer renderer = (DefaultTreeCellRenderer) tcr;
              renderer.setBorderSelectionColor(null);
              renderer.setTextSelectionColor(
                      UIManager.getColor(COLOR_KEY_TABLE_SELECTION_FOREGROUND));
              renderer.setBackgroundSelectionColor(
                      UIManager.getColor(COLOR_KEY_TABLE_SELECTION_BACKGROUND));
          }
      }
  
      /**
       * Sets the row height of the tree, and forwards the row height to
       * the table.
       */
      @Override
      public void setRowHeight(int newRowHeight) {
          if (newRowHeight > 0) {
              super.setRowHeight(newRowHeight);
              if (treeTable != null
                      && treeTable.getRowHeight() != newRowHeight) {
                  treeTable.setRowHeight(getRowHeight());
              }
          }
      }
  
      /**
       * This is overridden to set the height to match that of the JTable.
       */
      @Override
      public void setBounds(int x, int y, int w, int h) {
          super.setBounds(x, 0, w, treeTable.getHeight());
      }
  
      /**
       * Subclassed to translate the graphics such that the last visible
       * row will be drawn at 0,0.
       */
      @Override
      public void paint(Graphics graph) {
          graph.translate(0, -visibleRow * getRowHeight());
          super.paint(graph);
      }
  
      /**
       * TreeCellRenderer method. Overridden to update the visible row.
       *
       * @see TableCellRenderer
       */
      @Override
      public Component getTableCellRendererComponent(JTable table,
              Object value,
              boolean isSelected,
              boolean hasFocus,
              int row, int column) {
          final String colorKey;
          if (isSelected) {
              colorKey = COLOR_KEY_TABLE_SELECTION_BACKGROUND;
          }
          else {
              colorKey = COLOR_KEY_TABLE_BACKGROUND;
          }
  
          setBackground(UIManager.getColor(colorKey));
          visibleRow = row;
          return this;
      }
  
  }
  