6542439: Significant memory leak in BasicComboBoxUI and MetalComboBoxButton

Reviewed-by: serb

src/java.desktop/macosx/classes/com/apple/laf/AquaComboBoxButton.java

@@ -229,5 +229,8 @@ class AquaComboBoxButton extends JButton {
         rendererPane.paintComponent(g, c, this, left, top, cWidth, height, shouldValidate); // h - (insets.top + insets.bottom) );
 
         if (inhibitBackground) c.setBackground(bg);
+
+        // Remove component from renderer pane, allowing it to be gc'ed.
+        rendererPane.remove(c);
     }
 }

src/java.desktop/share/classes/com/sun/java/swing/plaf/motif/MotifComboBoxUI.java

@@ -175,6 +175,8 @@ public class MotifComboBoxUI extends BasicComboBoxUI implements Serializable {
             g.setColor(UIManager.getColor("controlHighlight"));
             g.fillRect(r.x,r.y,r.width,r.height);
         }
+        // Empty out the renderer pane, allowing renderers to be gc'ed.
+        currentValuePane.removeAll();
     }
 
     public void paintCurrentValue(Graphics g,Rectangle bounds,boolean hasFocus) {

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

@@ -944,6 +944,8 @@ public class BasicComboBoxUI extends ComboBoxUI {
             paintCurrentValueBackground(g,r,hasFocus);
             paintCurrentValue(g,r,hasFocus);
         }
+        // Empty out the renderer pane, allowing renderers to be gc'ed.
+        currentValuePane.removeAll();
     }
 
     @Override

src/java.desktop/share/classes/javax/swing/plaf/metal/MetalComboBoxButton.java

@@ -283,6 +283,8 @@ public class MetalComboBoxButton extends JButton {
                 rendererPane.paintComponent( g, c, this,
                                              left + iconWidth, top, cWidth, height, shouldValidate );
             }
+            // Remove the component from renderer pane, allowing it to be gc'ed.
+            rendererPane.remove(c);
         }
     }
 

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

@@ -358,6 +358,8 @@ public class SynthComboBoxUI extends BasicComboBoxUI implements
             Rectangle r = rectangleForCurrentValue();
             paintCurrentValue(g,r,hasFocus);
         }
+        // Empty out the renderer pane, allowing renderers to be gc'ed.
+        currentValuePane.removeAll();
     }
 
     /**

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

@@ -0,0 +1,108 @@
+/*
+ * Copyright (c) 2020, 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 6542439
+ * @summary Verifies memory leak in BasicComboBoxUI and MetalComboBoxButton
+ * @run main TestMemLeakComboBox
+ */
+import java.awt.Graphics;
+import java.awt.Component;
+import java.awt.Container;
+import java.awt.Dimension;
+import java.awt.FlowLayout;
+import javax.swing.JFrame;
+import javax.swing.JPanel;
+import javax.swing.JComboBox;
+import javax.swing.CellRendererPane;
+import javax.swing.SwingUtilities;
+import javax.swing.UIManager;
+import javax.swing.UnsupportedLookAndFeelException;
+
+public class TestMemLeakComboBox {
+    private static JFrame frame;
+    private static String failed = null;
+
+    private static void setLookAndFeel(UIManager.LookAndFeelInfo laf) {
+        try {
+            UIManager.setLookAndFeel(laf.getClassName());
+        } catch (UnsupportedLookAndFeelException ignored) {
+            System.out.println("Unsupported L&F: " + laf.getClassName());
+        } catch (ClassNotFoundException | InstantiationException
+                 | IllegalAccessException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private static class MyPanel extends JPanel {
+        public void paint(Graphics g) {
+            super.paint(g);
+            for (Component child : getComponents()) {
+                verifyChild(child);
+            }
+        }
+
+        private void verifyChild(Component c) {
+            if (c instanceof JComboBox) {
+                for (Component child : ((Container)c).getComponents()) {
+                    if (child instanceof CellRendererPane &&
+                            ((CellRendererPane)child).getComponentCount() > 0) {
+                        failed = new String("CellRendererPane still has children for: " + c);
+                    }
+                }
+            }
+        }
+    }
+
+    public static void main(String[] args) throws Exception {
+        for (UIManager.LookAndFeelInfo laf : UIManager.getInstalledLookAndFeels()) {
+            System.out.println("Testing l&f : " + laf.getClassName());
+            SwingUtilities.invokeAndWait(() -> setLookAndFeel(laf));
+            test();
+            if (failed != null) {
+                throw new RuntimeException(failed);
+            }
+        }
+    }
+
+    private static void test() throws Exception {
+        try {
+            SwingUtilities.invokeAndWait(() -> {
+                frame = new JFrame();
+                JPanel panel = new MyPanel();
+                panel.setPreferredSize(new Dimension(100, 100));
+                panel.setLayout(new FlowLayout());
+                panel.add(new JComboBox(new String[]{"one", "two", "three"}));
+
+                frame.add(panel);
+                frame.pack();
+                frame.setVisible(true);
+            });
+        } finally  {
+            if (frame != null) {
+                SwingUtilities.invokeAndWait(() -> frame.dispose());
+            }
+        }
+    }
+}