Name: chT40241 Date: 02/27/98


This example is to show that drawString does not honor clipping
regions for lightweight components. Stretch this thing around in
appletviewer. The cyan rectangles are Containers. The far left is a lightweight component in a container. The center is a heavyweight, the right is a double buffered thing. The only reason the one on the right is correct is that drawString is drawing on the Image graphics, not the one passed in.

Lara Bunni has seen this on 25Feb98 running against JDK 1.1.1G during a visit by SAS Institute Inc.

Here is the source code:
import java.awt.*;
import java.applet.*;

public class ClipSample extends Applet {
    public void init() {
        //set the applet color to blue
        //setLayout(new BorderLayout());
        setLayout(new BorderLayout());
        //Panel panel = new Panel();
        Container panel = new MyContainer();
        panel.setLayout(new BorderLayout());
        panel.setBackground(Color.pink);
        //ScrollPane sp = new ScrollPane();
        Container sp = new MyContainer();
        MyComponent c = new MyComponent();
        c.setBackground(Color.green);
        sp.add(c);
        panel.add("West", sp);

        //sp = new ScrollPane();
        sp = new MyContainer();
        sp.setBackground(Color.blue);
        MyPanel p = new MyPanel();
        p.setBackground(Color.green);
        sp.add(p);
        panel.add("Center", sp);

        //sp = new ScrollPane();
        sp = new MyContainer();
        sp.setBackground(Color.blue);
        MyDoubleBufferedComponent dbc = new MyDoubleBufferedComponent();
        dbc.setBackground(Color.green);
        sp.add(dbc);
        panel.add("East", sp);
        add("Center", panel);
        add("South", new MyContainer(){
            public Dimension getPreferredSize() {
                return new Dimension(200, 200);
            }
        });
    }
}
class MyComponent extends Component {
    public MyComponent() {
        super();
    }
    public void update(Graphics g) {
        //do not fill with the background
        //but call paint directly
        paint(g);
    }
    public void paint(Graphics g) {
        //fill a rectangle only on left side
        //of the panel (0,0,150,200)
        Color c = g.getColor();
        g.setColor(Color.red);
        g.fillRect(20, 20, 150, 200);
        Rectangle clip = g.getClipBounds();
        g.setClip(20, 20, 150, 200);
        //draw the current java version in the component
        g.setColor(Color.black);
        String version = System.getProperty("java.version");
        String vendor = System.getProperty("java.vendor");
        int y = 10;
        for(int i = 0; i < 30; i++) {
            g.drawString("Lightweight: Java version: " + version +
                         ", Vendor: " + vendor, 10, y += 20);
        }
        g.setColor(c);
        g.setClip(clip);
        super.paint(g);
    }

    public Dimension preferredSize() {
        return new Dimension(300, 300);
    }
}
class MyDoubleBufferedComponent extends Component {
    public MyDoubleBufferedComponent() {
        super();
    }
    public void update(Graphics g) {
        //do not fill with the background
        //but call paint directly
        paint(g);
    }
    public void paint(Graphics graphics) {
        //fill a rectangle only on left side
        //of the panel (0,0,150,200)
        Dimension size = this.getSize();
        Graphics g = graphics;
        Image image = null;
        if((size.width > 0) && (size.height > 0)) {
            image = createImage(size.width, size.height);
            g = image.getGraphics();
        }
        Color c = g.getColor();
        g.setColor(Color.red);
        g.fillRect(20, 20, 150, 200);
        Rectangle clip = g.getClipBounds();
        g.setClip(20, 20, 150, 200);
        //draw the current java version in the component
        g.setColor(Color.black);
        String version = System.getProperty("java.version");
        String vendor = System.getProperty("java.vendor");
        int y = 10;
        for(int i = 0; i < 30; i++) {
            g.drawString("Double buffered: Java version: " +
                         version + ", Vendor: " + vendor, 10, y += 20);
        }
        g.setColor(c);
        if(image != null) {
            graphics.drawImage(image, 0, 0, this);
        }
        g.setClip(clip);
        super.paint(g);
    }

    public Dimension preferredSize() {
        return new Dimension(300, 300);
    }
}
class MyPanel extends Panel {
    public MyPanel() {
        super();
    }
    public void update(Graphics g) {
        //do not fill with the background
        //but call paint directly
        paint(g);
    }
    public void paint(Graphics g) {
        //fill a rectangle only on left side
        //of the panel (0,0,150,200)
        Color c = g.getColor();
        g.setColor(Color.red);
        g.fillRect(20, 20, 150, 200);
        Rectangle clip = g.getClipBounds();
        g.setClip(20, 20, 150, 200);

        //draw the current java version in the panel
        g.setColor(Color.black);
        String version = System.getProperty("java.version");
        String vendor = System.getProperty("java.vendor");
        int y = 10;
        for(int i = 0; i < 30; i++) {
            g.drawString("Heavyweight: Java version: " + version +
                         ", Vendor: " + vendor, 10, y += 20);
        }
        g.setColor(c);
        g.setClip(clip);
        super.paint(g);
    }

    public Dimension preferredSize() {
        return new Dimension(300, 300);
    }
}
class MyContainer extends Container {
    public MyContainer() {
        super();
        setLayout(new FlowLayout());
    }
    public void paint(Graphics g) {
        Rectangle bounds = new Rectangle(getSize());
        g.setColor(Color.cyan);
        g.drawRect(bounds.x, bounds.y, bounds.width - 1, bounds.height - 1);
        super.paint(g);
    }
}


And here is the html file:

<HTML>
<HEAD>
<TITLE> A sample program </TITLE>
</HEAD>
<BODY>
<APPLET CODE="ClipSample.class" WIDTH=400 HEIGHT=300></APPLET>
</BODY>
</HTML>

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