8252194: Add automated test for fix done in JDK-8218469

Reviewed-by: serb, jdv, kizune

test/jdk/javax/swing/JSlider/TestJSliderRendering.java

@@ -0,0 +1,148 @@
+/*
+ * Copyright (c) 2020, 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
+ * @requires (os.family == "linux")
+ * @key headful
+ * @bug 8218469
+ * @summary Tests JSlider is rendered properly with gtk3
+ * @run main TestJSliderRendering
+ */
+
+import javax.swing.JFrame;
+import javax.swing.JPanel;
+import javax.swing.JSlider;
+import javax.swing.SwingUtilities;
+import javax.swing.UIManager;
+import javax.swing.UnsupportedLookAndFeelException;
+import java.awt.Color;
+import java.awt.Component;
+import java.awt.Point;
+import java.awt.Rectangle;
+import java.awt.Robot;
+
+public class TestJSliderRendering {
+    private static JFrame frame;
+    private static JSlider slider;
+    private static Point point;
+    private static Rectangle rect;
+    private static Robot robot;
+    private static final String GTK_LAF_CLASS = "GTKLookAndFeel";
+    private static int minColorDifference = 50;
+
+    private static void blockTillDisplayed(Component comp) {
+        Point p = null;
+        while (p == null) {
+            try {
+                p = comp.getLocationOnScreen();
+            } catch (IllegalStateException e) {
+                try {
+                    Thread.sleep(500);
+                } catch (InterruptedException ie) {
+                }
+            }
+        }
+    }
+
+    private static int getMaxColorDiff(Color c1, Color c2) {
+        return Math.max(Math.abs(c1.getRed() - c2.getRed()),
+                Math.max(Math.abs(c1.getGreen() - c2.getGreen()),
+                        Math.abs(c1.getBlue() - c2.getBlue())));
+    }
+
+    public static void main(String[] args) throws Exception {
+        if (!System.getProperty("os.name").startsWith("Linux")) {
+            System.out.println("This test is meant for Linux platform only");
+            return;
+        }
+
+        for (UIManager.LookAndFeelInfo lookAndFeelInfo :
+                UIManager.getInstalledLookAndFeels()) {
+            if (lookAndFeelInfo.getClassName().contains(GTK_LAF_CLASS)) {
+                try {
+                    UIManager.setLookAndFeel(lookAndFeelInfo.getClassName());
+                } catch (final UnsupportedLookAndFeelException ignored) {
+                    System.out.println("GTK L&F could not be set, so this " +
+                            "test can not be run in this scenario ");
+                    return;
+                }
+            }
+        }
+
+        robot = new Robot();
+        robot.setAutoDelay(100);
+
+        try {
+            SwingUtilities.invokeAndWait(new Runnable() {
+                public void run() {
+                    JPanel panel = new JPanel();
+                    slider = new JSlider(JSlider.HORIZONTAL, 0, 100, 50);
+                    panel.add(slider);
+                    frame = new JFrame("TestJSliderRendering");
+                    frame.add(panel);
+                    frame.setSize(200, 200);
+                    frame.setAlwaysOnTop(true);
+                    frame.setLocationRelativeTo(null);
+                    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+                    frame.setVisible(true);
+                }
+            });
+
+            robot.waitForIdle();
+            robot.delay(500);
+
+            blockTillDisplayed(slider);
+            SwingUtilities.invokeAndWait(() -> {
+                point = slider.getLocationOnScreen();
+                rect = slider.getBounds();
+            });
+            robot.waitForIdle();
+            robot.delay(500);
+
+            int h = point.y+rect.height*6/7;
+
+            Color backgroundColor = robot
+                    .getPixelColor(point.x+rect.width/4, h);
+            robot.waitForIdle();
+
+            boolean knobFound = false;
+            for (int i=point.x+rect.width/4;i<point.x+rect.width*3/4;i+=2) {
+                Color highlightColor = robot.getPixelColor(i, h);
+                if (getMaxColorDiff(backgroundColor, highlightColor)
+                        > minColorDifference) {
+                    knobFound = true;
+                    break;
+                }
+                robot.waitForIdle();
+            }
+            if (!knobFound) {
+                throw new RuntimeException("The slider is not rendered properly");
+            }
+        } finally {
+            if (frame != null) {
+                SwingUtilities.invokeAndWait(frame::dispose);
+            }
+        }
+    }
+}