--- a/src/java.desktop/macosx/native/libawt_lwawt/awt/AWTWindow.m	Tue Oct 30 15:43:37 2018 +0530
+++ b/src/java.desktop/macosx/native/libawt_lwawt/awt/AWTWindow.m	Tue Oct 30 17:06:32 2018 +0530
@@ -214,7 +214,7 @@
     if (IS(styleBits, UNIFIED))       type |= NSUnifiedTitleAndToolbarWindowMask;
     if (IS(styleBits, UTILITY))       type |= NSUtilityWindowMask;
     if (IS(styleBits, HUD))           type |= NSHUDWindowMask;
-    if (IS(styleBits, SHEET))         type |= NSDocModalWindowMask;
+    if (IS(styleBits, SHEET))         type |= NSWindowStyleMaskDocModalWindow;
     if (IS(styleBits, NONACTIVATING)) type |= NSNonactivatingPanelMask;
 
     return type;
@@ -273,7 +273,12 @@
 {
 AWT_ASSERT_APPKIT_THREAD;
 
-    NSUInteger styleMask = [AWTWindow styleMaskForStyleBits:bits];
+    NSUInteger newBits = bits;
+    if (IS(bits, SHEET) && owner == nil) {
+        newBits = bits & ~NSWindowStyleMaskDocModalWindow;
+    }
+    NSUInteger styleMask = [AWTWindow styleMaskForStyleBits:newBits];
+
     NSRect contentRect = rect; //[NSWindow contentRectForFrameRect:rect styleMask:styleMask];
     if (contentRect.size.width <= 0.0) {
         contentRect.size.width = 1.0;
@@ -289,7 +294,8 @@
     if (IS(bits, UTILITY) ||
         IS(bits, NONACTIVATING) ||
         IS(bits, HUD) ||
-        IS(bits, HIDES_ON_DEACTIVATE))
+        IS(bits, HIDES_ON_DEACTIVATE) ||
+        IS(bits, SHEET))
     {
         self.nsWindow = [[AWTWindow_Panel alloc] initWithDelegate:self
                             frameRect:contentRect
@@ -319,6 +325,10 @@
         [self.nsWindow setCollectionBehavior:(1 << 8) /*NSWindowCollectionBehaviorFullScreenAuxiliary*/];
     }
 
+    if (IS(bits, SHEET) && owner != nil) {
+        [self.nsWindow setStyleMask: NSWindowStyleMaskDocModalWindow];
+    }
+
     return self;
 }
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/jdk/java/awt/Dialog/DocumentModalSheetTest/DocumentModalSheetTest.java	Tue Oct 30 17:06:32 2018 +0530
@@ -0,0 +1,160 @@
+/*
+ * Copyright (c) 2018, 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
+ * @bug 8208543
+ * @requires (os.family == "mac")
+ * @summary Support for apple.awt.documentModalSheet incomplete in Mac
+ * @run main/manual DocumentModalSheetTest
+ */
+
+import java.awt.Dialog;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.awt.FlowLayout;
+import javax.swing.JFrame;
+import javax.swing.JDialog;
+import javax.swing.JLabel;
+import javax.swing.JButton;
+import javax.swing.JTextArea;
+import javax.swing.Timer;
+import javax.swing.SwingUtilities;
+
+public class DocumentModalSheetTest {
+
+    private static JFrame jFrame;
+    private static JDialog jDialog;
+    private static JFrame instructionFrame;
+    private static Timer timer;
+    private static final int sleepTime = 300000;
+    private static volatile boolean testContinueFlag = true;
+    private static final String TEST_INSTRUCTIONS =
+    " This is a manual test\n\n" +
+    " 1) A Modal dialog with label 'Modal Dialog as Sheet' will be displayed\n" +
+    "   i) Press PASS if dialog appears as a sheet\n" +
+    "   ii) Press FAIL otherwise\n" +
+    " 2) A Modal dialog with label 'Modal Dialog as Window' will be displayed\n" +
+    "   i) Press PASS if dialog appears as a Window\n" +
+    "   ii) Press FAIL otherwise\n";
+    private static String FAIL_MESSAGE = "Modal dialog displayed as a new window";
+
+    private static void createAndShowInstructionFrame() throws Exception {
+        SwingUtilities.invokeAndWait(new Runnable() {
+            public void run() {
+                JButton passButton = new JButton("Pass");
+                passButton.setEnabled(true);
+
+                JButton failButton = new JButton("Fail");
+                failButton.setEnabled(true);
+
+                JTextArea instructions = new JTextArea(5, 60);
+                instructions.setText(TEST_INSTRUCTIONS);
+
+                instructionFrame = new JFrame("Test Instructions");
+                instructionFrame.add(passButton);
+                instructionFrame.add(failButton);
+                instructionFrame.add(instructions);
+                instructionFrame.setSize(200,200);
+                instructionFrame.setLayout(new FlowLayout());
+                instructionFrame.pack();
+                instructionFrame.setVisible(true);
+
+                passButton.addActionListener(ae -> {
+                    jDialog.setVisible(false);
+                    timer.stop();
+                    dispose();
+                });
+
+                failButton.addActionListener(ae -> {
+                    jDialog.setVisible(false);
+                    timer.stop();
+                    dispose() ;
+                    testContinueFlag = false;
+                    throw new RuntimeException(FAIL_MESSAGE);
+                });
+            }
+        });
+    }
+
+    private static void createAndShowModalDialog() throws Exception {
+        SwingUtilities.invokeAndWait(new Runnable() {
+            public void run() {
+                try {
+                    //Display Modal Dialog as a SHEET
+                    jFrame = new JFrame();
+                    createAndShowModalSheet(jFrame, "Modal Dialog as Sheet");
+                    if (testContinueFlag) {
+                        //Display Modal Dialog as a Window
+                        FAIL_MESSAGE = "Modal dialog displayed as a Sheet";
+                        createAndShowModalSheet(null, "Modal Dialog as Window");
+                        testContinueFlag = false;
+                    }
+                } catch (Exception e) {
+                    throw new RuntimeException("Modal dialog creation failed");
+                } finally {
+                    if (instructionFrame != null) {
+                        instructionFrame.dispose();
+                    }
+                }
+            }
+        });
+    }
+
+    private static void createAndShowModalSheet(JFrame frame, String label) throws Exception {
+        jDialog = new JDialog(frame, null, Dialog.ModalityType.DOCUMENT_MODAL);
+        jDialog.setSize(200, 200);
+        jDialog.getRootPane().putClientProperty("apple.awt.documentModalSheet", Boolean.TRUE);
+        JLabel jLabel = new JLabel(label);
+        jDialog.add(jLabel);
+
+        timer = new Timer(sleepTime, new ActionListener() {
+            public void actionPerformed(ActionEvent e) {
+                jDialog.setVisible(false);
+                testContinueFlag = false;
+                dispose();
+                throw new RuntimeException("Timed out after " +
+                                           sleepTime / 1000 + " seconds");
+            }
+        });
+        timer.setRepeats(false);
+        timer.start();
+
+        jDialog.pack();
+        jDialog.setVisible(true);
+    }
+
+    private static void dispose() {
+        if (jDialog != null) {
+            jDialog.dispose();
+        }
+        if (jFrame != null) {
+            jFrame.dispose();
+        }
+    }
+
+    public static void main(String[] args) throws Exception {
+        createAndShowInstructionFrame();
+        createAndShowModalDialog();
+    }
+}