ComboBox: fixed occasional StackOverflowError when modifying combo box not on AWT thread (issue #432)

flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatStressTest.java

@@ -0,0 +1,83 @@
+/*
+ * Copyright 2021 FormDev Software GmbH
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.formdev.flatlaf.testing;
+
+import java.awt.Container;
+import java.awt.FlowLayout;
+import java.util.Random;
+import javax.swing.JComboBox;
+import javax.swing.JComponent;
+import javax.swing.JFrame;
+import javax.swing.SwingUtilities;
+import com.formdev.flatlaf.FlatClientProperties;
+import com.formdev.flatlaf.FlatLightLaf;
+
+/**
+ * @author Karl Tauber
+ */
+public class FlatStressTest
+{
+	public static void main( String[] args ) {
+		SwingUtilities.invokeLater( () -> {
+			FlatLightLaf.setup();
+			new FlatStressTest();
+		} );
+	}
+
+	protected FlatStressTest() {
+		JFrame frame = new JFrame( "FlatStressTest" );
+		frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
+
+		Container contentPane = frame.getContentPane();
+		contentPane.setLayout( new FlowLayout() );
+
+		contentPane.add( createStressTest() );
+
+		frame.setSize( 800, 600 );
+		frame.setLocationRelativeTo( null );
+		frame.setVisible( true );
+	}
+
+	private JComponent createStressTest() {
+		return createComboBoxStressTest();
+	}
+
+	// for https://github.com/JFormDesigner/FlatLaf/issues/432
+	// simulates StackOverflowError in FlatComboBoxUI when doing stuff in various threads
+	//
+	// requires adding `Thread.sleep( 1 );` to `FlatComboBoxUI.CellPaddingBorder.install()`
+	// after invocation of `uninstall()`
+	private JComponent createComboBoxStressTest() {
+		Random random = new Random();
+
+		JComboBox<String> comboBox = new JComboBox<>();
+		comboBox.putClientProperty( FlatClientProperties.MINIMUM_WIDTH, 0 );
+		for( int i = 0; i < 100; i++ )
+			comboBox.addItem( Integer.toString( random.nextInt() ) );
+
+		Thread thread = new Thread( () -> {
+			for(;;) {
+				comboBox.setSelectedIndex( random.nextInt( comboBox.getItemCount() ) );
+				comboBox.putClientProperty( FlatClientProperties.MINIMUM_WIDTH, random.nextInt( 500 ) );
+			}
+		});
+		thread.setDaemon( true );
+		thread.start();
+
+		return comboBox;
+	}
+}