8212904: JTextArea line wrapping incorrect when using UI scale

src/java.desktop/share/classes/javax/swing/text/Utilities.java

@@ -665,7 +665,7 @@ static final int getBreakLocation(Segment s, FontMetrics metrics,
     public static final int getBreakLocation(Segment s, FontMetrics metrics,
                                              float x0, float x, TabExpander e,
                                              int startOffset) {
-        return getBreakLocation(s, metrics, x0, x, e, startOffset, false);
+        return getBreakLocation(s, metrics, x0, x, e, startOffset, true);
     }
 
     /**

src/java.desktop/share/classes/javax/swing/text/WrappedPlainView.java

@@ -360,7 +360,8 @@ protected int calculateBreakPosition(int p0, int p1) {
         int currentWidth = getWidth();
         if (wordWrap) {
             p = p0 + Utilities.getBreakLocation(segment, metrics,
-                                                tabBase, tabBase + currentWidth,
+                                                (float)tabBase,
+                                                (float)(tabBase + currentWidth),
                                                 this, p0);
         } else {
             p = p0 + Utilities.getTabbedTextOffset(segment, metrics,

test/jdk/javax/swing/JTextArea/JTextAreaWordWrapTest.java

@@ -0,0 +1,116 @@
+/*
+ * Copyright (c) 2019, 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 8212904
+ * @summary Verifies JTextArea line wrapping using UI scale
+ * @run main JTextAreaWordWrapTest
+ */
+import java.awt.BorderLayout;
+import java.awt.event.WindowAdapter;
+import java.awt.event.WindowEvent;
+import java.io.IOException;
+import java.net.URISyntaxException;
+import javax.swing.JFrame;
+import javax.swing.JScrollPane;
+import javax.swing.JTextArea;
+import javax.swing.ScrollPaneConstants;
+import javax.swing.SwingUtilities;
+
+public class JTextAreaWordWrapTest {
+
+    static JFrame frame;
+    static JFrame frame1;
+    static JTextArea textArea;
+    static JTextArea textArea1;
+
+    public static void doWrapOnTest() {
+
+        frame = new JFrame();
+        frame.setSize( 720, 300 );
+        frame.setLayout( new BorderLayout() );
+
+        textArea = new JTextArea();
+        textArea.setLineWrap( true );
+        textArea.setWrapStyleWord( true );
+
+        StringBuffer sb = new StringBuffer();
+        for (int i = 0; i < 100; i++) {
+            sb.append( "zz zzz zzzz zz zz zz zzz xzzzz zzzzzzzzzzzzzzzzx yyyyyyy tttttttttt sssss hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh\n" );
+        }
+        textArea.setText( sb.toString() );
+        JScrollPane pane = new JScrollPane( textArea,
+                                            ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS,
+                                            ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED );
+        frame.add( pane, BorderLayout.CENTER );
+        frame.setVisible( true );
+
+    }
+
+    public static void doWrapOffTest() {
+        frame1 = new JFrame();
+        frame1.setSize( 720, 300 );
+        frame1.setLayout( new BorderLayout() );
+
+        textArea1 = new JTextArea();
+
+        StringBuffer sb1 = new StringBuffer();
+        for (int i = 0; i < 100; i++) {
+            sb1.append( "zz zzz zzzz zz zz zz zzz xzzzz zzzzzzzzzzzzzzzzx yyyyyyy tttttttttt sssss hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh\n" );
+        }
+        textArea1.setText( sb1.toString() );
+        JScrollPane pane1 = new JScrollPane( textArea1,
+                                             ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS,
+                                             ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED );
+        frame1.add( pane1, BorderLayout.CENTER );
+        frame1.setLocationRelativeTo(null);
+        frame1.setVisible( true );
+    }
+
+    public static void main( String[] args ) throws Exception {
+        System.setProperty( "sun.java2d.uiScale", "1.25" );
+        try {
+            SwingUtilities.invokeAndWait(() -> doWrapOnTest());
+            Thread.sleep(500);
+            SwingUtilities.invokeAndWait(() -> doWrapOffTest());
+            Thread.sleep(500);
+
+            SwingUtilities.invokeAndWait(() -> {
+
+                int wraponHeight = textArea.getHeight();
+                System.out.println("wraponheight " + wraponHeight);
+                int wrapoffHeight = textArea1.getHeight();
+                System.out.println("wrapoffheight " + wrapoffHeight);
+
+                if (wraponHeight == wrapoffHeight) {
+                    throw new RuntimeException("JTextArea line wrapping incorrect when using UI scale");
+                }
+            });
+
+        } finally {
+            SwingUtilities.invokeAndWait(() -> frame.dispose());
+            SwingUtilities.invokeAndWait(() -> frame1.dispose());
+        }
+    }
+}