I was trying to upgrade the BeanBox to have better support for
lightweight components.

I converted our key container class "Wrappr" to be a lightweight
container. It works OK when it only contains lightweight beans.

However if you put a heavyweight bean inside the lightweight
Wrapper, it behaves wrongly on moves. When the Wrapper gets
moved its contents get left behind at the old location.

I couldn't find any reasonable workaround, so I've had to backoff
and revert the Wrapper to being heavyweight.

Here's a small example that demonstrates the problem. Initially
the wrapper and its contained JellyBean appear in the top left.
After 5 seconds we move them to the bottom right. But only the
Wrapper moves, the JellyBean gets left behind.

If you make the Jellybean "lightweight", the problem goes away. But
I have to be able to deal with existing heavyweight components. :-(

An OK annswer to this bug is to say that lightweight containers
can't contain heavyweight components. Then I can stop worrying
about it. ;-) But it might be worth enforcing that in the container
code.

KGH 4/27/97


import java.awt.*;

class Wrapper extends Container {

    public void paint(Graphics g) {
// draw a bounding box.
int width = getSize().width;
int height = getSize().height;
g.drawLine(0, 0, width-1, 0);
g.drawLine(0, 0, 0, height-1);
g.drawLine(width-1, 0, width-1, height-1);
g.drawLine(0, height-1, width-1, height-1);
super.paint(g);
   }

}

class JellyBean extends Canvas {
    public void paint(Graphics g) {
g.setColor(Color.red);
g.fillArc(5, 5, 30, 30, 0, 360);
g.fillArc(25, 5, 30, 30, 0, 360);
g.fillRect(20, 5, 20, 30);
    }

    public Dimension getPreferredSize() {
return new Dimension(50,80);
    }
}

public class Test {

    public static void main(String argv[]) {

Frame fram = new Frame("Test");
fram.setLayout(null);
Wrapper w = new Wrapper();
w.setLayout(null);
JellyBean jb = new JellyBean();

fram.setSize(300,300);
fram.show();

fram.add(w);
w.setBounds(20,40,100,100);

w.add(jb);
jb.setBounds(5,5,80,80);

try {
Thread.sleep(5000);
} catch (Exception ex) {
}

w.setBounds(160,160,100,100);
w.repaint();
fram.repaint();
jb.repaint();

    }
}