4459231: Focus of JTabbedPane(with Scrollable tablayout) changes on change in LookAndFeel

src/java.desktop/share/classes/javax/swing/plaf/basic/BasicTabbedPaneUI.java

@@ -293,6 +293,16 @@ public void installUI(JComponent c) {
         installDefaults();
         installListeners();
         installKeyboardActions();
+        setFocusIndex(tabPane.getSelectedIndex(), false);
+
+        if (tabPane.getLayout() instanceof TabbedPaneScrollLayout) {
+            ensureCurrentLayout();
+            int index = tabPane.getSelectedIndex();
+            if (index < rects.length && index != -1) {
+                tabScroller.tabPanel.scrollRectToVisible(
+                            (Rectangle)rects[index].clone());
+            }
+        }
     }
 
     public void uninstallUI(JComponent c) {

test/jdk/javax/swing/JTabbedPane/TabbedPaneBugWithLNF.java

@@ -0,0 +1,109 @@
+/*
+ * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code 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 General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 4459231
+ * @summary Verifies getBaseline causes NPE for Nimbus L&F
+ * @library /java/awt/regtesthelpers
+ * @build PassFailJFrame
+ * @run main/manual TabbedPaneBugWithLNF
+ */
+
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import javax.swing.JButton;
+import javax.swing.JFrame;
+import javax.swing.JTabbedPane;
+import javax.swing.SwingUtilities;
+import javax.swing.UIManager;
+
+public class TabbedPaneBugWithLNF {
+
+    private static String LNF = "com.sun.java.swing.plaf.motif.MotifLookAndFeel";
+    private static JTabbedPane tabPane;
+    private static JButton testBtn;
+    private String labelOfCurrentJBtn = null;
+
+    static final String INSTRUCTIONS = """
+        A JTabbedPane with 10 tabs will be shown.
+        Scroll the tabs till the end, i.e., to "Testing Tab9".
+        Select that tab.
+        You will see the main tab JButton's text changed to 'Test Button9'.
+        Click on it, which will change the lookandfeel.
+        Verify if child tabs have scrolled back to starting child tab
+        i.e., 'Testing Tab0', where as the selected tab is still 'Testing Tab9'.
+        If it does, press Fail
+        else if focus of the child Tab is still at "Testing Tab9" press Pass.""";
+
+    public static void main(String[] args) throws Exception {
+        UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");
+        PassFailJFrame.builder()
+                .title("TabbedPaneBugWithLNF Test Instructions")
+                .instructions(INSTRUCTIONS)
+                .columns(50)
+                .testUI(TabbedPaneBugWithLNF::createUI)
+                .position(PassFailJFrame.Position.TOP_LEFT_CORNER)
+                .build()
+                .awaitAndCheck();
+    }
+
+    static JFrame createUI() {
+        JFrame frame = new JFrame("TabbedPaneBugWithLNF");
+        frame.setSize(640, 180);
+
+        tabPane = new JTabbedPane(JTabbedPane.BOTTOM,JTabbedPane.SCROLL_TAB_LAYOUT);
+
+        tabPane.addTab("Testing Tab0", testBtn = new JButton("Test Button0"));
+
+        tabPane.addTab("Testing Tab1", testBtn = new JButton("Test Button1"));
+
+        tabPane.addTab("Testing Tab2", testBtn = new JButton("Test Button2"));
+
+        tabPane.addTab("Testing Tab3", testBtn = new JButton("Test Button3"));
+
+        tabPane.addTab("Testing Tab4", testBtn = new JButton("Test Button4"));
+
+        tabPane.addTab("Testing Tab5", testBtn = new JButton("Test Button5"));
+
+        tabPane.addTab("Testing Tab6", testBtn = new JButton("Test Button6"));
+
+        tabPane.addTab("Testing Tab7", testBtn = new JButton("Test Button7"));
+        tabPane.addTab("Testing Tab8", testBtn = new JButton("Test Button8"));
+        JButton myBtn = null;
+        tabPane.addTab("Testing Tab9", myBtn = new JButton("Test Button9"));
+        myBtn.addActionListener( new ActionListener() {
+            public void actionPerformed(ActionEvent ae) {
+                try {
+                    UIManager.setLookAndFeel(LNF);
+                    SwingUtilities.updateComponentTreeUI(frame);
+                    System.out.println("tabPane.selectedIndex " + tabPane.getSelectedIndex());
+                } catch (Exception exc) {
+                    System.out.println("Error changing L&F : " + LNF);
+                }
+            }
+        });
+        frame.add(tabPane);
+        return frame;
+    }
+}