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import java.awt.AWTException;
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.GraphicsDevice;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.ScrollPane;
import java.awt.event.MouseEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.lang.reflect.InvocationTargetException;
import java.util.Arrays;
import java.util.concurrent.atomic.AtomicReference;

import static java.awt.EventQueue.invokeAndWait;
import static java.awt.GraphicsEnvironment.getLocalGraphicsEnvironment;

/**
 * A test case for
 * <a href="https://bugs.openjdk.org/browse/JDK-8297923">JDK-8297923</a>:
 * <i>java.awt.ScrollPane broken after multiple scroll up/down</i>.
 * <p>
 * The test consists of a main frame, a scroll pane and a canvas which is
 * scrolled inside it. After scrolling up and down for a while, the canvas
 * starts to paint over the main frame.
 * <p>
 * Usually, the problem is reproduced after one repeat of the up/down cycle.
 * The number of repeats is controlled by {@link #REPEATS}, and the number
 * of cycles is controlled by {@link #UP_DOWN_CYCLES}.
 * <p>
 * You may need to pass {@code -Dsun.java2d.d3d=false} to disable Direct3D
 * pipeline.
 * <p>
 * If you need to stop the test before the automatic actions are complete,
 * click left mouse button, then press {@code Alt+F4} to close the frame.
 */
public class ScrollPaneTest {

    /**
     * The number of times the test repeats scrolling cycles.
     */
    private static final int REPEATS = 1;

    /**
     * The number of times the robot moves the scroll bar thumb down and up
     * per one cycle.
     */
    private static final int UP_DOWN_CYCLES = 20;

    private static final Dimension canvasSize = new Dimension(400, 600);
    private static final Dimension frameSize = new Dimension(canvasSize.width * 2,
                                                             3 * canvasSize.height / 4);
    private static final Dimension scrollPaneSize = new Dimension(canvasSize.width,
                                                                  canvasSize.height / 2);

    private static Frame frame;
    private static ScrollPane scroll;

    private static final AtomicReference<Rectangle> scrollBounds = new AtomicReference<>();

    private static final AtomicReference<Integer> vertBarWidth = new AtomicReference<>();
    private static final AtomicReference<Integer> horzBarHeight = new AtomicReference<>();

    public static void main(String[] args)
            throws InterruptedException, InvocationTargetException, AWTException {
        invokeAndWait(ScrollPaneTest::createUI);

        final Robot robot = new Robot();
        robot.waitForIdle();

        invokeAndWait(() -> frame.setExtendedState(frame.getExtendedState()
                                                   | Frame.MAXIMIZED_BOTH));
        robot.waitForIdle();

        invokeAndWait(() -> {
            scrollBounds.set(new Rectangle(scroll.getLocationOnScreen(),
                                           scroll.getSize()));

            vertBarWidth.set(scroll.getVScrollbarWidth());
            horzBarHeight.set(scroll.getHScrollbarHeight());
        });
        robot.waitForIdle();

        invokeAndWait(() -> scroll.setScrollPosition(0, 0));
        robot.waitForIdle();
        robot.delay(1000);

        final Rectangle sb = scrollBounds.get();
        final int vbar = vertBarWidth.get();
        final int hbar = horzBarHeight.get() * 2;

        final Point pos = new Point();
        for (int no = 0; no < REPEATS; no++) {
            pos.x = sb.x + sb.width - vbar / 3;
            pos.y = sb.y + hbar;

            robot.mouseMove(pos.x, pos.y);
            robot.mousePress(MouseEvent.BUTTON1_DOWN_MASK);
            for (int i = 0; i < UP_DOWN_CYCLES; i++) {
                while (++pos.y < sb.y + sb.height - hbar) {
                    robot.mouseMove(pos.x, pos.y);
                    robot.delay(5);
                }
                while (--pos.y > sb.y + hbar) {
                    robot.mouseMove(pos.x, pos.y);
                    robot.delay(5);
                }
            }
            robot.mouseRelease(MouseEvent.BUTTON1_DOWN_MASK);

            invokeAndWait(() -> frame.setExtendedState(frame.getExtendedState()
                                                       | Frame.ICONIFIED));
            robot.delay(2000);
            invokeAndWait(() -> frame.setExtendedState(frame.getExtendedState()
                                                       & ~Frame.ICONIFIED));
            robot.delay(2000);
        }
        invokeAndWait(() -> scroll.setScrollPosition(0, sb.height / 2));
    }

    private static void createUI() {
        GraphicsDevice mainScreen = getLocalGraphicsEnvironment()
                                    .getDefaultScreenDevice();
        GraphicsDevice frameScreen = Arrays.stream(getLocalGraphicsEnvironment()
                                                   .getScreenDevices())
                                           .filter(s -> s != mainScreen)
                                           .findFirst()
                                           .orElse(mainScreen);

        frame = new Frame("Scroll Pane Test",
                          frameScreen.getDefaultConfiguration());
        frame.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        });

        frame.setLayout(new FlowLayout(FlowLayout.CENTER));
        frame.setLocation(frameScreen
                          .getDefaultConfiguration()
                          .getBounds()
                          .getLocation());

        Canvas canvas = new Canvas() {
            final Color color = new Color(200, 240, 200);

            @Override
            public void paint(Graphics g) {
                g.setColor(color);
                g.fillRect(0, 0, getWidth(), getHeight());
            }
        };
        canvas.setBackground(new Color(240, 200, 240));
        canvas.setSize(canvasSize);

        scroll = new ScrollPane(ScrollPane.SCROLLBARS_ALWAYS);
        scroll.add(canvas);
        scroll.setSize(scrollPaneSize);
        scroll.setBackground(new Color(240, 240, 200));

        frame.add(scroll);
        frame.setSize(frameSize);

        frame.setVisible(true);
    }

}