test/jdk/java/awt/GradientPaint/ShearTest.java

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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/*
 * @test
 * @bug 4171820
 * @summary Checks that GradientPaint responds to shearing transforms correctly
 *          The gradients drawn should be parallel to the sides of the
 *          indicated anchor rectangle.
 * @library /java/awt/regtesthelpers
 * @build PassFailJFrame
 * @run main/manual ShearTest
 */

import java.awt.Canvas;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Frame;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridLayout;
import java.awt.Panel;
import java.awt.Rectangle;
import java.awt.geom.AffineTransform;

public class ShearTest {
    public static void main(String[] args) throws Exception {
        String INSTRUCTIONS = """
                This test displays 2 rows each containing 4 gradient fills. Each
                gradient fill is labeled depending on whether the line or lines
                of the gradient should be truly vertical, truly horizontal, or
                some slanted diagonal direction. The test passes if the direction
                of each gradient matches its label.
                """;

        PassFailJFrame.builder()
                .title("Test Instructions")
                .instructions(INSTRUCTIONS)
                .columns(35)
                .testUI(ShearTest::createUI)
                .build()
                .awaitAndCheck();
    }

    public static Frame createUI() {
        Frame f = new Frame("Shear Gradient Test");
        f.setLayout(new GridLayout(0, 1));
        f.add(getPanelSet(false), "North");
        f.add(getPanelSet(true), "Center");
        f.setSize(500, 300);
        return f;
    }

    public static Panel getPanelSet(boolean horizontal) {
        String direven = horizontal ? "Slanted" : "Vertical";
        String dirodd = horizontal ? "Horizontal" : "Slanted";

        Panel p = new Panel();
        p.setLayout(new GridLayout(0, 4));
        p.add(new ShearCanvas(direven, false, horizontal, false, true));
        p.add(new ShearCanvas(dirodd,  false, horizontal, true,  false));
        p.add(new ShearCanvas(direven, true,  horizontal, false, true));
        p.add(new ShearCanvas(dirodd,  true,  horizontal, true,  false));

        return p;
    }

    public static class ShearCanvas extends Canvas {
        public static final int GRADW = 30;

        public static final Rectangle anchor =
            new Rectangle(-GRADW / 2, -GRADW / 2, GRADW, GRADW);

        public static final Color faintblue = new Color(0f, 0f, 1.0f, 0.35f);

        private AffineTransform txform;
        private GradientPaint grad;
        private String label;

        public ShearCanvas(String label,
                           boolean cyclic, boolean horizontal,
                           boolean shearx, boolean sheary) {
            txform = new AffineTransform();
            if (shearx) {
                txform.shear(-.5, 0);
            }
            if (sheary) {
                txform.shear(0, -.5);
            }
            int relx = horizontal ? 0 : GRADW / 2;
            int rely = horizontal ? GRADW / 2 : 0;
            grad = new GradientPaint(-relx, -rely, Color.green,
                                     relx, rely, Color.yellow, cyclic);
            this.label = label;
        }

        public void paint(Graphics g) {
            Graphics2D g2d = (Graphics2D) g;

            AffineTransform at = g2d.getTransform();
            g2d.translate(75, 75);
            g2d.transform(txform);
            g2d.setPaint(grad);
            g2d.fill(g.getClip());
            g2d.setColor(faintblue);
            g2d.fill(anchor);
            g2d.setTransform(at);

            Dimension d = getSize();
            g2d.setColor(Color.black);
            g2d.drawRect(0, 0, d.width - 1, d.height - 1);
            g2d.drawString(label, 5, d.height - 5);
            g2d.dispose();
        }
    }
}