firePropertyChange("content", oldContent, newContent);
    }
    

    /**
     * Answers if the panel is currently selected (or in other words active)
     * or not. In the selected state, the header background will be
     * rendered differently.
     * 
     * @return boolean  a boolean, where true means the frame is selected 
     *                  (currently active) and false means it is not  
     */
    public boolean isSelected() {
        return isSelected;
    }
    
    
    /**
     * This panel draws its title bar differently if it is selected,
     * which may be used to indicate to the user that this panel
     * has the focus, or should get more attention than other
     * simple internal frames.
     *
     * @param newValue  a boolean, where true means the frame is selected 
     *                  (currently active) and false means it is not
     */
    public void setSelected(boolean newValue) {
        boolean oldValue = isSelected();
        isSelected = newValue;
        updateHeader();
        firePropertyChange("selected", oldValue, newValue);
    }
    

    // Building *************************************************************

    /**
     * Creates and answers the header panel, that consists of:
     * an icon, a title label, a tool bar, and a gradient background.
     * 
     * @param label   the label to paint the icon and text
     * @param bar     the panel's tool bar
     * @return the panel's built header area
     */
    private JPanel buildHeader(JLabel label, JToolBar bar) {
        gradientPanel =
            new GradientPanel(new BorderLayout(), getHeaderBackground());
        label.setOpaque(false);

        gradientPanel.add(label, BorderLayout.WEST);
        gradientPanel.setBorder(BorderFactory.createEmptyBorder(3, 4, 3, 1));

        headerPanel = new JPanel(new BorderLayout());
        headerPanel.add(gradientPanel, BorderLayout.CENTER);
        setToolBar(bar);
        headerPanel.setBorder(new RaisedHeaderBorder());
        headerPanel.setOpaque(false);
        return headerPanel;
    }

    /**
     * Updates the header.
     */
    private void updateHeader() {
        gradientPanel.setBackground(getHeaderBackground());
        gradientPanel.setOpaque(isSelected());
        titleLabel.setForeground(getTextForeground(isSelected()));
        headerPanel.repaint();
    }
    

    /**
     * Updates the UI. In addition to the superclass behavior, we need
     * to update the header component.
     */
    public void updateUI() {
        super.updateUI();
        if (titleLabel != null) {
            updateHeader();
        }
    }


    // Helper Code **********************************************************

    /**
     * Checks and answers if the panel has a content component set.
     * 
     * @return true if the panel has a content, false if it's empty
     */
    private boolean hasContent() {
        return getComponentCount() > 1;
    }
    
    /**
     * Determines and answers the header's text foreground color.
     * Tries to lookup a special color from the L&F.
     * In case it is absent, it uses the standard internal frame forground.
     * 
     * @param selected   true to lookup the active color, false for the inactive
     * @return the color of the foreground text
     */
    protected Color getTextForeground(boolean selected) {
        Color c =
            UIManager.getColor(
                selected
                    ? "SimpleInternalFrame.activeTitleForeground"
                    : "SimpleInternalFrame.inactiveTitleForeground");
        if (c != null) {
            return c;
        }
        return UIManager.getColor(
            selected 
                ? "InternalFrame.activeTitleForeground" 
                : "Label.foreground");

    }

    /**
     * Determines and answers the header's background color.
     * Tries to lookup a special color from the L&F.
     * In case it is absent, it uses the standard internal frame background.
     * 
     * @return the color of the header's background
     */
    protected Color getHeaderBackground() {
        Color c =
            UIManager.getColor("SimpleInternalFrame.activeTitleBackground");
        if (c != null)
            return c;
        if (LookUtils.IS_LAF_WINDOWS_XP_ENABLED)
            c = UIManager.getColor("InternalFrame.activeTitleGradient");
        return c != null
            ? c
            : UIManager.getColor("InternalFrame.activeTitleBackground");
    }


    // Helper Classes *******************************************************

    // A custom border for the raised header pseudo 3D effect.
    private static class RaisedHeaderBorder extends AbstractBorder {

        private static final Insets INSETS = new Insets(1, 1, 1, 0);

        public Insets getBorderInsets(Component c) { return INSETS; }

        public void paintBorder(Component c, Graphics g,
            int x, int y, int w, int h) {
                
            g.translate(x, y);
            g.setColor(UIManager.getColor("controlLtHighlight"));
            g.fillRect(0, 0,   w, 1);
            g.fillRect(0, 1,   1, h-1);
            g.setColor(UIManager.getColor("controlShadow"));
            g.fillRect(0, h-1, w, 1);
            g.translate(-x, -y);
        }
    }

    // A custom border that has a shadow on the right and lower sides.
    private static class ShadowBorder extends AbstractBorder {

        private static final Insets INSETS = new Insets(1, 1, 3, 3);

        public Insets getBorderInsets(Component c) { return INSETS; }

        public void paintBorder(Component c, Graphics g,
            int x, int y, int w, int h) {
                
            Color shadow        = UIManager.getColor("controlShadow");
            if (shadow == null) {
                shadow = Color.GRAY;
            }
            Color lightShadow   = new Color(shadow.getRed(), 
                                            shadow.getGreen(), 
                                            shadow.getBlue(), 
                                            170);
            Color lighterShadow = new Color(shadow.getRed(),
                                            shadow.getGreen(),
                                            shadow.getBlue(),
                                            70);
            g.translate(x, y);
            
            g.setColor(shadow);
            g.fillRect(0, 0, w - 3, 1);
            g.fillRect(0, 0, 1, h - 3);
            g.fillRect(w - 3, 1, 1, h - 3);
            g.fillRect(1, h - 3, w - 3, 1);
            // Shadow line 1
            g.setColor(lightShadow);
            g.fillRect(w - 3, 0, 1, 1);
            g.fillRect(0, h - 3, 1, 1);
            g.fillRect(w - 2, 1, 1, h - 3);
            g.fillRect(1, h - 2, w - 3, 1);
            // Shadow line2
            g.setColor(lighterShadow);
            g.fillRect(w - 2, 0, 1, 1);
            g.fillRect(0, h - 2, 1, 1);
            g.fillRect(w-2, h-2, 1, 1);
            g.fillRect(w - 1, 1, 1, h - 2);
            g.fillRect(1, h - 1, w - 2, 1);
            g.translate(-x, -y);
        }
    }

    // A panel with a horizontal gradient background.
    private static class GradientPanel extends JPanel {
        
        private GradientPanel(LayoutManager lm, Color background) {
            super(lm);
            setBackground(background);
        }

        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            if (!isOpaque()) {
                return;
            }
            Color control = UIManager.getColor("control");
            int width  = getWidth();
            int height = getHeight();

            Graphics2D g2 = (Graphics2D) g;
            Paint storedPaint = g2.getPaint();
            g2.setPaint(
                new GradientPaint(0, 0, getBackground(), width, 0, control));
            g2.fillRect(0, 0, width, height);
            g2.setPaint(storedPaint);
        }
    }

}