A background painter that puts a circle in the background of a component.

Sample.java

BackgroundPainter p = new BackgroundPainter(cmp) {

                @Override
                public void paint(Graphics g, Rectangle rect) {
                    boolean antiAliased = g.isAntiAliased();
                    g.setAntiAliased(true);
                    int r = Math.min(rect.getWidth(), rect.getHeight())/2;
                    int x = rect.getX() + rect.getWidth()/2 - r;
                    int y = rect.getY() + rect.getHeight()/2 - r;
                    switch (style) {
                        case CircleButtonStrokedDark:
                        case CircleButtonStrokedLight: {
                            if (cmp.getStyle().getBgTransparency() != 0) {
                                int alpha = cmp.getStyle().getBgTransparency();
                                if (alpha <0) {
                                    alpha = 0xff;
                                }
                                g.setColor(cmp.getStyle().getBgColor());
                                g.setAlpha(alpha);
                                g.fillArc(x, y, 2*r-1, 2*r-1, 0, 360);
                                g.setAlpha(0xff);
                            }
                            g.setColor(cmp.getStyle().getFgColor());
                            
                            g.drawArc(x, y, 2*r-1, 2*r-1, 0, 360);
                            break;
                        }
                        case CircleButtonFilledDark:
                        case CircleButtonFilledLight:
                        case CircleButtonTransparentDark:
                        case CircleButtonTransparentLight: {
                            int alpha = cmp.getStyle().getBgTransparency();
                            if (alpha < 0) {
                                alpha = 0xff;
                            }
                            g.setAlpha(alpha);
                            g.setColor(cmp.getStyle().getBgColor());
                            g.fillArc(x, y, 2*r, 2*r, 0, 360);
                            g.setAlpha(0xff);
                            break;
                        }
                    }
                    
                    g.setAntiAliased(antiAliased);
                }
                
            };
            cmp.getAllStyles().setBgPainter(p);