6529151: NullPointerException in swing.plaf.synth.SynthLookAndFeel$Handler

Reviewed-by: serb, dnguyen

Author: prsadhuk

src/java.desktop/share/classes/javax/swing/plaf/synth/SynthLookAndFeel.java

@@ -1000,6 +1000,9 @@ private void repaintIfBackgroundsDiffer(JComponent comp) {
                 SynthStyle style = context.getStyle();
                 int state = context.getComponentState();
 
+                if (style == null) {
+                    return;
+                }
                 // Get the current background color.
                 Color currBG = style.getColor(context, ColorType.BACKGROUND);
 

test/jdk/javax/swing/plaf/synth/RepaintNPE.java

@@ -0,0 +1,124 @@
+/*
+ * 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
+ * @bug 6529151
+ * @key headful
+ * @summary  Verifies no NPE is thrown in SynthLookAndFeel$Handler
+ * @run main RepaintNPE
+ */
+import java.awt.Container;
+import java.awt.Component;
+import java.awt.Robot;
+import java.awt.Point;
+import java.awt.event.InputEvent;
+
+import javax.swing.JButton;
+import javax.swing.JComponent;
+import javax.swing.JDialog;
+import javax.swing.JEditorPane;
+import javax.swing.JFrame;
+import javax.swing.JScrollPane;
+import javax.swing.plaf.ComponentUI;
+import javax.swing.SwingUtilities;
+import javax.swing.UIManager;
+
+public class RepaintNPE
+{
+    private static JFrame frame;
+    private static JButton showDialogButton = null;
+
+    private static class DumbDialog extends JDialog {
+
+        public DumbDialog ( JFrame parent )
+        {
+            super ( parent, "DumbDialog", true );
+
+            setDefaultCloseOperation ( DISPOSE_ON_CLOSE );
+
+            JEditorPane editorPane = new JEditorPane();
+            editorPane.setContentType ( "text/html" );
+            editorPane.setEditable ( false );
+
+            JScrollPane scrollPane = new JScrollPane ( editorPane );
+            add( scrollPane );
+            setSize( 400, 400 );
+            setVisible( true );
+        }
+
+        public void dispose() {
+            super.dispose();
+            myDispose( this );
+        }
+
+        private void myDispose( Container container ) {
+            Component[] components = container.getComponents ();
+
+            for ( Component comp : components ) {
+                // Special dispose for JComponent's remove UI
+                if (comp instanceof JComponent) {
+                    JComponent jComp = (JComponent)comp;
+
+                    try
+                    {
+                        ComponentUI compUI = jComp.getUI();
+                        compUI.uninstallUI ( jComp );
+                    } catch ( Throwable t ) {}
+
+                    // Recurse children
+                    myDispose( jComp );
+                }
+            }
+        }
+
+    }
+
+    public static void main ( String args [] ) throws Exception
+    {
+        Robot robot = new Robot();
+        UIManager.setLookAndFeel("javax.swing.plaf.nimbus.NimbusLookAndFeel");
+        SwingUtilities.invokeAndWait ( () -> {
+            frame = new JFrame();
+
+            showDialogButton = new JButton( "Show Dialog" );
+            showDialogButton.addActionListener((e) -> {
+                if ( e.getSource() == showDialogButton ) {
+                    new DumbDialog ( frame );
+                }
+            });
+            frame.add ( showDialogButton );
+            frame.setSize( 100, 100 );
+            frame.setLocationRelativeTo(null);
+            frame.setUndecorated(true);
+            frame.setVisible( true );
+        });
+        robot.waitForIdle();
+        robot.delay(1000);
+        Point loc = frame.getLocationOnScreen();
+        robot.mouseMove(loc.x+10, loc.y+10);
+        robot.mousePress(InputEvent.BUTTON1_DOWN_MASK);
+        robot.mouseRelease(InputEvent.BUTTON1_DOWN_MASK);
+        robot.delay(1000);
+        SwingUtilities.invokeAndWait(() -> frame.dispose());
+    }
+}