public void update(Graphics g) {
flags |= IS_IN_UPDATE;
// clear and draw yourself
g.clearRect(0, 0, width, height);
paint(g);
flags &= ~IS_IN_UPDATE;
}
void makeImage() {
// if we have no image or if the image has changed
if (getGraphicsConfiguration() != null && getWidth() > 0) {
Dimension dim = c.getPreferredSize();
// width and height must be > 0 to be able to create an image
if (dim.height > 0) {
img = getGraphicsConfiguration().createCompatibleImage(getWidth(), dim.height);
c.setSize(getWidth(), dim.height);
c.paint(img.getGraphics());
} else {
img = null;
}
}
}