avoid using sun.swing.SwingUtilities2

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

@@ -29,7 +29,6 @@ import javax.swing.JComponent;
 import javax.swing.UIManager;
 import javax.swing.plaf.ComponentUI;
 import javax.swing.plaf.basic.BasicButtonUI;
-import sun.swing.SwingUtilities2;
 
 /**
  * Provides the Flat LaF UI delegate for {@link javax.swing.JButton}.
@@ -109,11 +108,11 @@ public class FlatButtonUI
 	@Override
 	protected void paintText( Graphics g, JComponent c, Rectangle textRect, String text ) {
 		AbstractButton b = (AbstractButton) c;
-		FontMetrics fm = SwingUtilities2.getFontMetrics( c, g );
+		FontMetrics fm = c.getFontMetrics( c.getFont() );
 		int mnemonicIndex = b.getDisplayedMnemonicIndex();
 
 		g.setColor( b.getModel().isEnabled() ? getForeground( c ) : disabledText );
-		SwingUtilities2.drawStringUnderlineCharAt( c, g, text, mnemonicIndex,
+		FlatUIUtils.drawStringUnderlineCharAt( c, g, text, mnemonicIndex,
 			textRect.x + getTextShiftOffset(),
 			textRect.y + fm.getAscent() + getTextShiftOffset() );
 	}

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

@@ -23,7 +23,6 @@ import javax.swing.JLabel;
 import javax.swing.UIManager;
 import javax.swing.plaf.ComponentUI;
 import javax.swing.plaf.basic.BasicLabelUI;
-import sun.swing.SwingUtilities2;
 
 /**
  * Provides the Flat LaF UI delegate for {@link javax.swing.JLabel}.
@@ -59,6 +58,6 @@ public class FlatLabelUI
 	protected void paintDisabledText( JLabel l, Graphics g, String s, int textX, int textY ) {
 		int mnemIndex = l.getDisplayedMnemonicIndex();
 		g.setColor( disabledForeground );
-		SwingUtilities2.drawStringUnderlineCharAt( l, g, s, mnemIndex, textX, textY );
+		FlatUIUtils.drawStringUnderlineCharAt( l, g, s, mnemIndex, textX, textY );
 	}
 }

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

@@ -33,7 +33,6 @@ import javax.swing.plaf.ComponentUI;
 import javax.swing.plaf.UIResource;
 import javax.swing.plaf.basic.BasicTabbedPaneUI;
 import javax.swing.text.View;
-import sun.swing.SwingUtilities2;
 
 /**
  * Provides the Flat LaF UI delegate for {@link javax.swing.JTabbedPane}.
@@ -261,7 +260,7 @@ public class FlatTabbedPaneUI
 		int mnemIndex = tabPane.getDisplayedMnemonicIndexAt( tabIndex );
 
 		g.setColor( color );
-		SwingUtilities2.drawStringUnderlineCharAt( tabPane, g, title, mnemIndex,
+		FlatUIUtils.drawStringUnderlineCharAt( tabPane, g, title, mnemIndex,
 			textRect.x, textRect.y + metrics.getAscent() );
 	}
 

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

@@ -27,6 +27,7 @@ import java.awt.geom.Path2D;
 import java.awt.geom.RoundRectangle2D;
 import javax.swing.JComponent;
 import javax.swing.UIManager;
+import com.formdev.flatlaf.util.JavaCompatibility;
 import com.formdev.flatlaf.util.UIScale;
 
 /**
@@ -156,4 +157,13 @@ public class FlatUIUtils
 		rect.closePath();
 		return rect;
 	}
+
+	/**
+	 * Replacement for SwingUtilities2.drawStringUnderlineCharAt()
+	 */
+	public static void drawStringUnderlineCharAt( JComponent c, Graphics g,
+		String text, int underlinedIndex, int x, int y )
+	{
+		JavaCompatibility.drawStringUnderlineCharAt( c, g, text, underlinedIndex, x, y );
+	}
 }

flatlaf-core/src/main/java/com/formdev/flatlaf/util/JavaCompatibility.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2019 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
+ *
+ *     http://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.util;
+
+import java.awt.Graphics;
+import java.awt.Graphics2D;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import javax.swing.JComponent;
+
+/**
+ * Provides Java version compatibility methods.
+ *
+ * WARNING: This is private API and may change.
+ *
+ * @author Karl Tauber
+ */
+public class JavaCompatibility
+{
+	private static Method drawStringUnderlineCharAtMethod;
+
+	/**
+	 * Java 8: sun.swing.SwingUtilities2.drawStringUnderlineCharAt( JComponent c,
+	 *				Graphics g, String text, int underlinedIndex, int x, int y )
+	 * Java 9: javax.swing.plaf.basic.BasicGraphicsUtils.drawStringUnderlineCharAt( JComponent c,
+	 *				Graphics2D g, String string, int underlinedIndex, float x, float y )
+	 */
+	public static void drawStringUnderlineCharAt( JComponent c, Graphics g,
+		String text, int underlinedIndex, int x, int y )
+	{
+		synchronized( JavaCompatibility.class ) {
+			if( drawStringUnderlineCharAtMethod == null ) {
+				try {
+					Class<?> cls = Class.forName( SystemInfo.IS_JAVA_9_OR_LATER
+						? "javax.swing.plaf.basic.BasicGraphicsUtils"
+						: "sun.swing.SwingUtilities2" );
+					drawStringUnderlineCharAtMethod = cls.getMethod( "drawStringUnderlineCharAt", SystemInfo.IS_JAVA_9_OR_LATER
+						? new Class[] { JComponent.class, Graphics2D.class, String.class, int.class, float.class, float.class }
+						: new Class[] { JComponent.class, Graphics.class, String.class, int.class, int.class, int.class } );
+				} catch( Exception ex ) {
+					ex.printStackTrace();
+					throw new RuntimeException( ex );
+				}
+			}
+		}
+
+		try {
+			if( SystemInfo.IS_JAVA_9_OR_LATER )
+				drawStringUnderlineCharAtMethod.invoke( null, c, g, text, underlinedIndex, (float) x, (float) y );
+			else
+				drawStringUnderlineCharAtMethod.invoke( null, c, g, text, underlinedIndex, x, y );
+		} catch( IllegalAccessException | IllegalArgumentException | InvocationTargetException ex ) {
+			ex.printStackTrace();
+			throw new RuntimeException( ex );
+		}
+	}
+}