macOS: fixed NullPointerException when using AWT component `java.aw…

…t.Choice` (issue #439)

CHANGELOG.md

@@ -12,6 +12,8 @@ FlatLaf Change Log
 - MenuItem: Changed accelerator delimiter from `-` to `+`. (Windows and Linux).
 - ComboBox: Fixed occasional `StackOverflowError` when modifying combo box not
   on AWT thread. (issue #432)
+- macOS: Fixed `NullPointerException` when using AWT component
+  `java.awt.Choice`. (issue #439)
 
 ## 1.6.4
 

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatComboBoxUI.java

@@ -260,7 +260,10 @@ protected LayoutManager createLayoutManager() {
 			public void layoutContainer( Container parent ) {
 				super.layoutContainer( parent );
 
-				if( arrowButton != null ) {
+				// on macOS, a Swing combo box is used for AWT component java.awt.Choice
+				// and the font may be (temporary) null
+
+				if( arrowButton != null && comboBox.getFont() != null ) {
 					// limit button width to height of a raw combobox (without insets)
 					FontMetrics fm = comboBox.getFontMetrics( comboBox.getFont() );
 					int maxButtonWidth = fm.getHeight() + scale( padding.top ) + scale( padding.bottom );

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatPopupFactory.java

@@ -121,17 +121,17 @@ private Popup getPopupForScreenOfOwner( Component owner, Component contents, int
 				popupWindow.getGraphicsConfiguration() == owner.getGraphicsConfiguration() )
 			  return popup;
 
+			// avoid endless loop (should newer happen; PopupFactory cache size is 5)
+			if( ++count > 10 )
+				return popup;
+
 			// remove contents component from popup window
 			if( popupWindow instanceof JWindow )
 				((JWindow)popupWindow).getContentPane().removeAll();
 
 			// dispose unused popup
 			// (do not invoke popup.hide() because this would cache the popup window)
 			popupWindow.dispose();
-
-			// avoid endless loop (should newer happen; PopupFactory cache size is 5)
-			if( ++count > 10 )
-				return popup;
 		}
 	}
 

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

@@ -0,0 +1,76 @@
+/*
+ * 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.*;
+import java.awt.event.WindowAdapter;
+import java.awt.event.WindowEvent;
+import com.formdev.flatlaf.FlatLightLaf;
+
+/**
+ * Used to test AWT components on macOS, which internally use Swing.
+ *
+ * @author Karl Tauber
+ */
+public class FlatAWTTest
+{
+	public static void main( String[] args ) {
+		EventQueue.invokeLater( () -> {
+			FlatLightLaf.setup();
+
+			Frame frame = new Frame( "FlatAWTTest" );
+			frame.addWindowListener( new WindowAdapter() {
+				@Override
+				public void windowClosing( WindowEvent e ) {
+					System.exit( 0 );
+				}
+			} );
+			frame.setLayout( new FlowLayout() );
+
+			frame.add( new Label( "text" ) );
+			frame.add( new Button( "text" ) );
+			frame.add( new Checkbox( "text" ) );
+
+			CheckboxGroup checkboxGroup = new CheckboxGroup();
+			frame.add( new Checkbox( "radio 1", true, checkboxGroup ) );
+			frame.add( new Checkbox( "radio 2", false, checkboxGroup ) );
+			frame.add( new Checkbox( "radio 3", false, checkboxGroup ) );
+
+			Choice choice = new Choice();
+			choice.add( "item 1" );
+			choice.add( "item 2" );
+			choice.add( "item 3" );
+			frame.add( choice );
+
+			frame.add( new TextField( "text" ) );
+			frame.add( new TextArea( "text" ) );
+
+			List list = new List();
+			list.add( "item 1" );
+			list.add( "item 2" );
+			frame.add( list );
+
+			frame.add( new Scrollbar() );
+			frame.add( new ScrollPane() );
+			frame.add( new Panel() );
+			frame.add( new Canvas() );
+
+			frame.setSize( 800, 600 );
+			frame.setVisible( true );
+		});
+	}
+}