exposed/damaged canvases don't always update correctly on win32

canvases don't repaint correctly when exposed on win32 (only --
this problem does not repro on solaris). the problem is generic
and may involve synchronization of damage with repair. in the
example code shown below, it is not easy to cause the problem to
occur (it may take a couple minutes of damaging the canvas to get
repaint problems), but that is no indication that the problem is
insignificant. in fact, it may be responsible for all sorts of
paint problems...

import java.applet.*;
import java.awt.*;

class Foo extends Canvas
{
    public void paint(Graphics g)
    {
        for (int i = 0; i < 100; i += 2)
        {
            g.drawString("this is a test of foo", i, i);
        }
    }

    public Dimension getPreferredSize()
    {
        return new Dimension(100, 100);
    }

    public Dimension getMinimumSize()
    {
        return getPreferredSize();
    }
}

public class test extends Applet
{
    public void init()
    {
        setLayout(new FlowLayout());
        add(new Foo());
        add(new Foo());
        add(new Foo());
    }
}