Javas GridBagLayout does not display an (extended) Canvas (AWT / Java 1.4)

Good evening!

I don't manage to make an AWT-Frame with a GridBagLayout display a
Canvas. This Canvas will be displayed as soon as I use an other than
the damned GridBagLayout. Unfortunately I have to use that
GridBagLayout but do not know how.

An other posting I found suggested to extend the Canvas and override
it's method getPreferredSize. I did so but still the (My)Canvas does
not appear within the GridBagLayout. Can anybody give me a helping
hint?

Regards

Christian

import java.awt.*;
import java.awt.event.*;

public class PaintCanves extends Frame {

    public PaintCanves() {

        GridBagLayout layout = new GridBagLayout();
        this.setLayout(layout);

        this.setSize(150, 200);
        this.setLocation(100, 100);
        this.setBackground(Color.gray);

        GridBagConstraints constraints = new GridBagConstraints();
        constraints.gridheight = GridBagConstraints.REMAINDER;
        constraints.gridwidth = GridBagConstraints.REMAINDER;
        constraints.anchor = GridBagConstraints.CENTER;
        constraints.fill = GridBagConstraints.BOTH;
        constraints.gridx = 0;
        constraints.gridy = 0;

        MyCanvas canvas = new MyCanvas();
        canvas.setBackground(Color.black);

        this.add(canvas, constraints);

    }

    class MyCanvas extends Canvas {

        public Dimension getPreferredSize() {
            // canvas claims at least all the surrounding frame
            return new Dimension(getWidth(), getHeight());
        }

    }

    public static void main (String argv[]) {

        PaintCanves maler = new PaintCanves();

        maler.addWindowListener(new WindowAdapter()
        {
            public void windowClosing (WindowEvent e) {
                System.exit (0);
            }
        });

        maler.setVisible (true);

    }

}