Non rectangular windows using Swing

Question

Hi everybody
I've been trying to create a non rectangular window (i.e. an oval window) subclassing javax.swing.JWindow but even though the drawing of the inside of the window works correctly, the problem is with the outer part, which is painted anyway using the background color while I'd like to have it
transparent so to simulate a real oval window.
i.e. I'd like to have something like (dots are just fillings to give the drawing some shape):
|. Transparent background...|
| ..... ----------------------- .......... |
| .... / Window ............... \ ....... |
| .... \ contents .............. / ....... | <--- Window's bounds
| ..... ----------------------- .......... |
|_____________________|
Any idea about how to prevent the background from being painted??
Thanks in advance
andrea

Answer 1

Here is what I have done to overcome a similar problem.
These two classes help me show a 'Bubble' popup similar to what Windows XP have
You can tweak it like you want.
/* Subclass of Window to show the Bubbles */
public class WindowBubble extends Window{
public WindowBubble(Frame owner, String text, Point startingPoint){
super(owner);
JBubble bubble = new JBubble(text, startingPoint);
setLocation(startingPoint);
add(bubble);
pack();
/* This code is based on SUN's examples of how to create Oval-Components */
public class JBubble extends JLabel {
int capWidth = 30;
Point start;
String label;
BufferedImage image;
public JBubble() {
this("", null);
public JBubble(String label, Point p) {
this.label = label;
start=p;
try {
Robot r = new Robot();
image = r.createScreenCapture(new Rectangle(start.x,start.y, getPreferredSize().width, getPreferredSize().height));
}catch(Exception e){
e.printStackTrace();
this.setHorizontalAlignment(JLabel.CENTER );
public String getLabel() {
return label;
public void setLabel(String label) {
this.label = label;
invalidate();
repaint();
public void paint(Graphics g) {
int width = getSize().width - 1;
int height = getSize().height - 1;
g.drawImage(image,0,0,this);
Color interior;
interior = (Color)UIManager.get("ToolTip.background") ;
// ***** paint the interior of the button
g.setColor(interior);
// left cap
g.fillArc(0, 0, // start
capWidth, height, // size
90, 180); // angle
// right cap
g.fillArc(width - capWidth, 0, // start
capWidth, height, // size
270, 180); // angle
// inner rectangle
g.fillRect(capWidth/2, 0, width - capWidth, height);
// ***** highlight the perimeter of the button
// draw upper and lower highlight lines
g.setColor(Color.black);
g.drawLine(capWidth/2, 0, width - capWidth/2, 0);
g.drawLine(capWidth/2, height, width - capWidth/2, height);
// upper arc left cap
g.drawArc(0, 0, // start
capWidth, height, // size
90, 180-40 // angle
// lower arc left cap
g.drawArc(0, 0, // start
capWidth, height, // size
270-40, 40 // angle
// upper arc right cap
g.drawArc(width - capWidth, 0,// start
capWidth, height, // size
90-40, 40 // angle
// lower arc right cap
g.drawArc(width - capWidth, 0, // start
capWidth, height, // size
270, 180-40 // angle
// ***** draw the label centered in the button
Font f = getFont(); if(f != null) {
FontMetrics fm =
getFontMetrics(getFont());
g.setColor(getForeground());
g.drawString(label, width/2 - fm.stringWidth(label)/2, height/2 + fm.getHeight()/2 - fm.getMaxDescent() );
public Dimension getPreferredSize() {
Font f = getFont();
if(f != null) {
FontMetrics fm = getFontMetrics(getFont());
return new Dimension(fm.stringWidth(label) + capWidth*2, fm.getHeight() + 10);
} else {
return new Dimension(100, 50);
public Dimension getMinimumSize() {
return new Dimension(100, 50);