8230728: Thin stroked shapes are not rendered if affine transform has flip bit

Use abs(at.getDeterminant()) in userSpaceLineWidth() to ensure positive value

Reviewed-by: prr, jdv

Author: Laurent Bourgès

src/java.desktop/share/classes/sun/java2d/marlin/DMarlinRenderingEngine.java

@@ -246,7 +246,8 @@ private double userSpaceLineWidth(AffineTransform at, double lw) {
             widthScale = 1.0d;
         } else if ((at.getType() & (AffineTransform.TYPE_GENERAL_TRANSFORM  |
                                     AffineTransform.TYPE_GENERAL_SCALE)) != 0) {
-            widthScale = Math.sqrt(at.getDeterminant());
+            // Determinant may be negative (flip), use its absolute value:
+            widthScale = Math.sqrt(Math.abs(at.getDeterminant()));
         } else {
             // First calculate the "maximum scale" of this transform.
             double A = at.getScaleX();       // m00

src/java.desktop/share/classes/sun/java2d/marlin/MarlinRenderingEngine.java

@@ -245,7 +245,8 @@ private float userSpaceLineWidth(AffineTransform at, float lw) {
             widthScale = 1.0f;
         } else if ((at.getType() & (AffineTransform.TYPE_GENERAL_TRANSFORM  |
                                     AffineTransform.TYPE_GENERAL_SCALE)) != 0) {
-            widthScale = (float)Math.sqrt(at.getDeterminant());
+            // Determinant may be negative (flip), use its absolute value:
+            widthScale = (float)Math.sqrt(Math.abs(at.getDeterminant()));
         } else {
             // First calculate the "maximum scale" of this transform.
             double A = at.getScaleX();       // m00

src/java.desktop/share/classes/sun/java2d/marlin/Version.java

@@ -27,7 +27,7 @@
 
 public final class Version {
 
-    private static final String VERSION = "marlin-0.9.1.2-Unsafe-OpenJDK";
+    private static final String VERSION = "marlin-0.9.1.3-Unsafe-OpenJDK";
 
     public static String getVersion() {
         return VERSION;

test/jdk/sun/java2d/marlin/FlipBitTest.java

@@ -0,0 +1,104 @@
+/*
+ * 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.
+ */
+
+
+import java.awt.BasicStroke;
+import java.awt.Color;
+import java.awt.Graphics2D;
+import java.awt.Rectangle;
+import java.awt.RenderingHints;
+import java.awt.geom.AffineTransform;
+import java.awt.geom.Ellipse2D;
+import java.awt.image.BufferedImage;
+import java.io.File;
+import java.io.IOException;
+import javax.imageio.ImageIO;
+
+
+/**
+ * Tests calculating user space line with a negative determinant (flip).
+ *
+ * @test
+ * @summary verify that flipped transformed lines are properly rasterized
+ * @bug 8230728
+ */
+public class FlipBitTest {
+
+    static final boolean SAVE_IMAGE = false;
+
+    public static void main(final String[] args) {
+
+        final int size = 100;
+
+        // First display which renderer is tested:
+        // JDK9 only:
+        System.setProperty("sun.java2d.renderer.verbose", "true");
+
+        System.out.println("FlipBitTest: size = " + size);
+
+        final BufferedImage image = new BufferedImage(size, size, BufferedImage.TYPE_INT_ARGB);
+
+        final Graphics2D g2d = (Graphics2D) image.getGraphics();
+        try {
+            g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
+            g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
+            g2d.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL, RenderingHints.VALUE_STROKE_NORMALIZE);
+
+            final AffineTransform at = new AffineTransform();
+            at.setToScale(1, -1.01);
+            g2d.setTransform(at);
+
+            g2d.translate(0, -image.getHeight());
+            g2d.setPaint(Color.WHITE);
+            g2d.fill(new Rectangle(image.getWidth(), image.getHeight()));
+
+            g2d.setPaint(Color.BLACK);
+            g2d.setStroke(new BasicStroke(0.1f));
+            g2d.draw(new Ellipse2D.Double(25, 25, 50, 50));
+
+            if (SAVE_IMAGE) {
+                try {
+                    final File file = new File("FlipBitTest.png");
+
+                    System.out.println("Writing file: " + file.getAbsolutePath());
+                    ImageIO.write(image, "PNG", file);
+                } catch (IOException ex) {
+                    ex.printStackTrace();
+                }
+            }
+
+            boolean nonWhitePixelFound = false;
+            for (int x = 0; x < image.getWidth(); ++x) {
+                if (image.getRGB(x, 50) != Color.WHITE.getRGB()) {
+                    nonWhitePixelFound = true;
+                    break;
+                }
+            }
+            if (!nonWhitePixelFound) {
+                throw new IllegalStateException("The ellipse was not drawn");
+            }
+        } finally {
+            g2d.dispose();
+        }
+    }
+}