4797982: Setting negative size of JSplitPane divider leads to unexpected results.

Reviewed-by: azvegint, prr

src/java.desktop/share/classes/javax/swing/JSplitPane.java

@@ -418,12 +418,16 @@ public class JSplitPane extends JComponent implements Accessible
 
     /**
      * Sets the size of the divider.
+     * Divider sizes {@code newSize < 0} are ignored.
      *
      * @param newSize an integer giving the size of the divider in pixels
      */
     @BeanProperty(description
             = "The size of the divider.")
     public void setDividerSize(int newSize) {
+        if (newSize < 0) {
+            return;
+        }
         int           oldSize = dividerSize;
 
         dividerSizeSet = true;

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

@@ -219,10 +219,14 @@ public class BasicSplitPaneDivider extends Container
      * Sets the size of the divider to {@code newSize}. That is
      * the width if the splitpane is {@code HORIZONTAL_SPLIT}, or
      * the height of {@code VERTICAL_SPLIT}.
+     * Divider sizes {@code newSize < 0} are ignored.
      *
      * @param newSize a new size
      */
     public void setDividerSize(int newSize) {
+        if (newSize < 0) {
+            return;
+        }
         dividerSize = newSize;
     }
 

test/jdk/javax/swing/JSplitPane/JSplitPaneTestNegDivSize.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2022, 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
+ * @key headful
+ * @bug 4797982
+ * @summary Verifies if negative size of JSplitPane divider can be set.
+ * @run main JSplitPaneTestNegDivSize
+ */
+import java.awt.BorderLayout;
+import java.awt.Dimension;
+import javax.swing.JFrame;
+import javax.swing.JSplitPane;
+import javax.swing.JTextArea;
+import javax.swing.SwingUtilities;
+import javax.swing.UIManager;
+import javax.swing.plaf.basic.BasicSplitPaneUI;
+
+public class JSplitPaneTestNegDivSize {
+
+    private static volatile int divSize;
+    private static volatile int basicDivSize;
+    private static JFrame frame;
+    private static JSplitPane sp;
+
+    public static void main(String[] args) throws Exception {
+        SwingUtilities.invokeAndWait(() -> {
+            frame = new JFrame();
+            sp = new JSplitPane(JSplitPane.VERTICAL_SPLIT, true,
+                    new JTextArea("I am top text area!"),
+                    new JTextArea("I am bottom text area!"));
+            frame.getContentPane().add(sp, BorderLayout.CENTER);
+            sp.setDividerSize(-50);
+            divSize = sp.getDividerSize();
+            ((BasicSplitPaneUI)sp.getUI()).getDivider().setDividerSize(-50);
+            basicDivSize = ((BasicSplitPaneUI)sp.getUI()).getDivider().
+                                              getDividerSize();
+            frame.setSize(new Dimension(400,200));
+            frame.setVisible(true);
+        });
+        try {
+            Thread.sleep(1000);
+        } catch(Exception e){}
+        SwingUtilities.invokeAndWait(()->frame.dispose());
+        System.out.println(divSize);
+        System.out.println(basicDivSize);
+        System.out.println((Integer)UIManager.get("SplitPane.dividerSize"));
+        if (divSize < 0 || basicDivSize < 0) {
+            throw new RuntimeException("Negative divider size");
+        }
+    }
+}