Marco,

Thanks for the help.  I understand how to draw to an image, but right
now, that's not my problem.  I have somewhat of a feel for what is
happening though.  When I set the glasspane to be visible and draw
lines on it, none of the lines are erased.  The lines accumulate which
is what I want to happen.  When I set the glasspane to be invisible
and then set it back to be visible, the lines all disappear except the
last one drawn.  I'm assuming paint(Graphics g) is called again when I
reset the glasspane to be visible.  Since the x and y values for the
line are global variables, they are remembered, but the calling of
paint erases the glasspane and only draws the last line (based on the
x and y values).

When I draw multiple lines and the JFrame containing the glasspane
loses focus, the only lines that disappear are those where another
window (such as an application window) has covered those particular
lines.  I am really confused as to how to solve the problem.  The
invocation of the paint is clearing the graphics.  And I have no idea
what is happening with the other problem.  Any ideas on workarounds?

Thanks,
Bryan

Steve and Harald,

Thanks for the information.  I do have one more question to ask.  I am
now able to accumulate my lines in the offscreen image.  I was able to
follow your example Steve and get it to work with the glasspane.  My
new problem is two-fold: a) the offscreen image background is gray and
b) the color of my lines can not be set accordingly.  If you look at
my code below, I've attempted to set the color of the lines to be red
in the paint(Graphics g) method, but instead they always show up as
the color black.  Any ideas as to why?

I suspect that to make the offscreen image transparent (like the
glasspane itself) that I have to mess with the alpha values of the
pixels.  This seems rather expensive, but I've found no other
solutions to make the background transparent.  Is there a "cheap" way
to do this?  As always, thanks for the help.

-Bryan

class TestCanvas extends JComponent implements
MouseListener,ActionListener,ImageObserver {
   
    boolean firstDraw = true;
    JFrame f;
    int x=0,y=0;
    Image img;
   
    public TestCanvas(JFrame jfr) {
        addMouseListener(this);
        f = jfr;
    }
   
   
    public void addNotify() {
        super.addNotify();
        img = createImage(400,400);
    }
   
   
    public void paint(Graphics g) {
        if(!firstDraw) {
            img.getGraphics().setColor(Color.red);
            img.getGraphics().drawLine(x+5,y+5,x+10,y+10);
            g.drawImage(img, 0, 0, this);
        }
    } //End of paint method
   
   
    public void draw(int x1, int y1) {
        x = x1;
        y = y1;
        paint(this.getGraphics().create());
    }
   
   
    public void actionPerformed(ActionEvent ae) {
        this.setVisible(false);   
    }
   
   
    public void mousePressed(MouseEvent e) {
    }
   
   
    public void mouseClicked(MouseEvent e) {
        Point cPPoint = SwingUtilities.convertPoint(this, e.getPoint(),
f.getContentPane());
        Component cmp = SwingUtilities.getDeepestComponentAt(f.getContentPane(),(int)cPPoint.getX(),(int)cPPoint.getY());
        String cmpName = cmp.getName();
        if(cmpName==null) {
            firstDraw = false;
            this.draw(e.getX(),e.getY());   
        }
        else {
            this.setVisible(false);
        }
    }
   
   
    public void mouseReleased(MouseEvent e) {
    }
   
   
    public void mouseEntered(MouseEvent e) {
    }
   
   
    public void mouseExited(MouseEvent e) {
    }
   
} //End of TestCanvas class

Alright, I figured out one problem and thought I would share.  I can't
do img.getGraphics().setColor(Color.red).  I have to first get the
image graphics then set the color like so:

Image img = createImage(400,400);
Graphics imgG = img.getGraphics();
imgG.setColor(Color.red);

The problem with the transparent background remains.  Anyone have any
suggestions that would minimize the use of resources (i.e. I DON'T
want to adjust the alpha values of all the background pixels.) and
enable the offscreen image background to be transparent?

Thanks,
Bryan

Problem solved.

You can use the GraphicsConfiguration class to make a transparent
image using the createCompatibleImage method.  It works great.  Thanks
guys for all your help!

Bryan