// Glenn Rowe's version of Petzold's Cloverleaf
// with minor mods by Nick Taylor (24.10.2003)

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import javax.swing.*;

/**
 * Draws a four-leaved clover
 * (with apologies to Charles Petzold)
 */
class Clover extends JFrame
{
  int frameWidth, frameHeight;
  Shape contentShape;
  Area cloverArea;

  public static void main(String[] argv)
  {
    Clover testShape = new Clover();
    testShape.setVisible(true);
  }

  public Clover()
  {
    setTitle("Cloverleaf using Areas");
    setSize(300,300);
    setBackground(Color.white);
    enableEvents(AWTEvent.WINDOW_EVENT_MASK |
      AWTEvent.COMPONENT_EVENT_MASK);
  }

  /**
   * Overridden so we can exit when window is closed
   */
  protected void processWindowEvent(WindowEvent e) {
    super.processWindowEvent(e);
    if (e.getID() == WindowEvent.WINDOW_CLOSING) {
      System.exit(0);
    }
  }

  /**
   * Defines the clover-shaped mask when the frame is
   * displayed and each time it is resized
   */
  protected void processComponentEvent(ComponentEvent e) {
    super.processComponentEvent(e);
    if (e.getID() == ComponentEvent.COMPONENT_RESIZED) {

      // Get dimensions of the drawing region
      // excluding the title bar
      frameWidth = getContentPane().getWidth();
      frameHeight = getContentPane().getHeight();

      // Define a rectangle that is used to clear the background in paint()
      Shape contentShape = new Rectangle2D.Double(0, 0, frameWidth, frameHeight);

      // Construct the clover mask from several Areas
      //
      // First, define the four elliptical lobes of the leaf
      Area[] ellipse = new Area[4];
      ellipse[0] = new Area(new Ellipse2D.Double(0, frameHeight/3,
        frameWidth/2, frameHeight/3));
      ellipse[1] = new Area(new Ellipse2D.Double(frameWidth/2, frameHeight/3,
        frameWidth/2, frameHeight/3));
      ellipse[2] = new Area(new Ellipse2D.Double(frameWidth/3, 0,
        frameWidth/3, frameHeight/2));
      ellipse[3] = new Area(new Ellipse2D.Double(frameWidth/3, frameHeight/2,
        frameWidth/3, frameHeight/2));

      // OR together the left and right ellipses
      ellipse[0].add(ellipse[1]);
      // OR together the top and bottom ellipses
      ellipse[2].add(ellipse[3]);

      // Creates the final clipping mask by XORing the left/right
      // and top/bottom pairs
      cloverArea = ellipse[0];
      cloverArea.exclusiveOr(ellipse[2]);
   }
  }

  /**
   * Draws the clover leaf using the clipping Area above.
   */
  public void paint(Graphics g)
  {
    // Get the graphics context for the drawing area
    // excluding the title bar
    Graphics2D g2d = (Graphics2D)getContentPane().getGraphics();

    // Clears the background, since the update() method in JFrame
    // won't do this for us.
    g2d.setPaint(getBackground());
    g2d.fill(contentShape);

    // Define the colour and clipping area for the clover
    g2d.setPaint(Color.black);
    g2d.setClip(cloverArea);

    // Draw the radial lines
    double radius =
      Math.sqrt(frameWidth*frameWidth + frameHeight*frameHeight)/2.0;
    GeneralPath clover = new GeneralPath();
    for (double angle = 0.0; angle <= 2*Math.PI;
      angle += Math.PI/180.0) {
      clover.moveTo(frameWidth/2, frameHeight/2);
      clover.lineTo((float)(radius * Math.cos(angle)) + frameWidth/2,
        -(float)(radius * Math.sin(angle)) + frameHeight/2);
    }
    g2d.draw(clover);
  }
}