8344981: [REDO] JDK-6672644 JComboBox still scrolling if switch to another window and return back

Co-authored-by: Alexander Zvegintsev <azvegint@openjdk.org>
Reviewed-by: azvegint, psadhukhan, honkar

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 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
@@ -1609,6 +1609,11 @@ public class BasicScrollBarUI
 
         /** {@inheritDoc} */
         public void actionPerformed(ActionEvent e) {
+            // If scrollbar isn't visible, stop the timer
+            if (!scrollbar.isShowing()) {
+                stopScrollTimer(e);
+                return;
+            }
             // If frame is disabled and timer is started in mousePressed
             // and mouseReleased is not called, then timer will not be stopped
             // Stop the timer if frame is disabled
@@ -1616,9 +1621,7 @@ public class BasicScrollBarUI
             do {
                 if (parent instanceof JFrame par) {
                     if (!par.isEnabled()) {
-                        ((Timer)e.getSource()).stop();
-                        buttonListener.handledEvent = false;
-                        scrollbar.setValueIsAdjusting(false);
+                        stopScrollTimer(e);
                         return;
                     }
                     break;
@@ -1660,6 +1663,12 @@ public class BasicScrollBarUI
         }
     }
 
+    private void stopScrollTimer(ActionEvent e) {
+        ((Timer) e.getSource()).stop();
+        buttonListener.handledEvent = false;
+        scrollbar.setValueIsAdjusting(false);
+    }
+
     private boolean isMouseLeftOfThumb() {
         return trackListener.currentMouseX < getThumbBounds().x;
     }

test/jdk/javax/swing/JComboBox/JComboBoxScrollFocusTest.java

@@ -0,0 +1,149 @@
+/*
+ * 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.
+ */
+
+import java.awt.Component;
+import java.awt.Point;
+import java.awt.Rectangle;
+import java.awt.Robot;
+import java.awt.event.InputEvent;
+import java.util.concurrent.FutureTask;
+import java.util.concurrent.TimeUnit;
+
+import javax.swing.JComboBox;
+import javax.swing.JFrame;
+import javax.swing.JScrollBar;
+import javax.swing.JScrollPane;
+import javax.swing.SwingUtilities;
+import javax.swing.plaf.basic.BasicComboPopup;
+
+/*
+ * @test
+ * @key headful
+ * @bug 6672644
+ * @summary Tests JComboBox scrollbar behavior when alt-tabbing
+ * @run main JComboBoxScrollFocusTest
+ */
+
+public class JComboBoxScrollFocusTest {
+    private static Robot robot;
+    private static JFrame comboboxFrame;
+    private static JComboBox<String> combobox;
+
+    public static void main(String[] args) throws Exception {
+        robot = new Robot();
+        try {
+            SwingUtilities.invokeAndWait(JComboBoxScrollFocusTest::createAndShowGUI);
+            doTest();
+        } finally {
+            SwingUtilities.invokeAndWait(comboboxFrame::dispose);
+        }
+    }
+
+    private static void createAndShowGUI() {
+        comboboxFrame = new JFrame("JComboBoxScrollFocusTest Test Frame");
+        combobox = new JComboBox<>();
+        for (int i = 0; i < 100; i++) {
+            combobox.addItem(String.valueOf(i));
+        }
+        comboboxFrame.add(combobox);
+        comboboxFrame.setSize(400, 200);
+        comboboxFrame.setLocationRelativeTo(null);
+        comboboxFrame.setVisible(true);
+    }
+
+    static Rectangle getOnScreenBoundsOnEDT(Component component) throws Exception {
+        robot.waitForIdle();
+        FutureTask<Rectangle> task = new FutureTask<>(()
+                -> new Rectangle(component.getLocationOnScreen(),
+                component.getSize()));
+        SwingUtilities.invokeLater(task);
+        return task.get(500, TimeUnit.MILLISECONDS);
+    }
+
+    private static JScrollBar getScrollBar() {
+        BasicComboPopup popup = (BasicComboPopup) combobox
+                .getAccessibleContext().getAccessibleChild(0);
+        JScrollPane scrollPane = (JScrollPane) popup
+                .getAccessibleContext().getAccessibleChild(0);
+        return scrollPane.getVerticalScrollBar();
+    }
+
+    private static int getScrollbarValue() throws Exception {
+        FutureTask<Integer> task = new FutureTask<>(() -> {
+            JScrollBar scrollBar = getScrollBar();
+            return scrollBar.getValue();
+        });
+        SwingUtilities.invokeAndWait(task);
+
+        return task.get(500, TimeUnit.MILLISECONDS);
+    }
+
+    private static void doTest() throws Exception {
+        robot.waitForIdle();
+        robot.delay(500);
+
+        Rectangle rectangle = getOnScreenBoundsOnEDT(combobox);
+
+        Point ptOpenComboboxPopup = new Point(rectangle.x + rectangle.width - 5,
+                rectangle.y + rectangle.height / 2);
+
+        robot.mouseMove(ptOpenComboboxPopup.x, ptOpenComboboxPopup.y);
+        robot.mousePress(InputEvent.BUTTON1_DOWN_MASK);
+        robot.mouseRelease(InputEvent.BUTTON1_DOWN_MASK);
+        robot.waitForIdle();
+        robot.delay(500);
+
+        JScrollBar scrollBar = getScrollBar();
+
+        // Start scrolling
+        Rectangle scrollbarBounds = getOnScreenBoundsOnEDT(scrollBar);
+        robot.mouseMove(scrollbarBounds.x + scrollbarBounds.width / 2,
+                scrollbarBounds.y + scrollbarBounds.height - 5);
+        robot.mousePress(InputEvent.BUTTON1_DOWN_MASK);
+
+        robot.delay(1000);
+
+        if (getScrollbarValue() == 0) {
+            throw new RuntimeException("The scrollbar is not scrolling");
+        }
+
+        // closing popup by moving focus to the main window
+        comboboxFrame.requestFocus();
+        robot.waitForIdle();
+        robot.mouseRelease(InputEvent.BUTTON1_DOWN_MASK);
+
+        robot.waitForIdle();
+        robot.delay(500);
+
+        // open popup again
+        robot.mouseMove(ptOpenComboboxPopup.x, ptOpenComboboxPopup.y);
+        robot.mousePress(InputEvent.BUTTON1_DOWN_MASK);
+        robot.mouseRelease(InputEvent.BUTTON1_DOWN_MASK);
+        robot.waitForIdle();
+        robot.delay(500);
+
+        if (getScrollbarValue() != 0) {
+            throw new RuntimeException("The scroll bar is scrolling");
+        }
+    }
+}