import java.awt.AWTEvent;
import java.awt.AlphaComposite;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.event.MouseEvent;

import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.MenuElement;
import javax.swing.RepaintManager;

import org.jdesktop.animation.timing.Animator;
import org.jdesktop.animation.timing.TimingTarget;
import org.jdesktop.animation.timing.TimingTargetAdapter;

public class WaftMenuBar extends JMenuBar {
    private AlphaComposite ac;
    private Animator fadein;
    private Animator fadeout;

    public WaftMenuBar() {
        ac = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.0f);

        TimingTarget target = new TimingTargetAdapter() {
                public void timingEvent(float fraction) {
                    ac = ac.derive(fraction);
                    repaint();
                }
            };

        fadein = new Animator(1000, target);
        fadeout = new Animator(1000, target);
        fadeout.setDirection(Animator.Direction.BACKWARD);
        
        enableEvents(AWTEvent.MOUSE_EVENT_MASK);
        RepaintManager.setCurrentManager(new FullRepaintManager());

        TimingTarget t = new TimingTargetAdapter() {
                public void timingEvent(float fraction) {
                    if (!isSubElementsVisible()) {
                        fade(fadein, fadeout);
                    }
                }
            };
        Animator animator = new Animator(Animator.INFINITE, t);
        animator.setStartDelay(5000);
        animator.start();
    }

    private boolean isSubElementsVisible() {
        Point pp = getMousePosition();
        if (pp != null && contains(pp)) {
            return true;
        }

        for (MenuElement element: getSubElements()) {
            JMenu menu = (JMenu)element;
            if (menu.isPopupMenuVisible()) {
                return true;
            }
        }
        return false;
    }
    
    public void paint(Graphics g) {
        Graphics2D g2d = (Graphics2D)g;
        g2d.setComposite(ac);
        super.paint(g);
    }

    protected void processMouseEvent(MouseEvent event) {
        if (event.getID() == MouseEvent.MOUSE_ENTERED) {
            fade(fadeout, fadein);
        }
    }

    private void fade(Animator end, Animator begin) {
        if (end.isRunning()) {
            end.stop();
        }

        if (begin.isRunning()) {
            return;
        }
        
        float fraction = ac.getAlpha();
        begin.setInitialFraction(fraction);
        begin.start();
    }
}