import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;

public class SigningSurface extends Canvas {

protected int width, height;			// dimensions of surface
protected int x,y, lastX, lastY;		// stroke coordinates
protected Image offscreenImage = null;
protected Graphics offscreenG;

//-------------------------------------------------------------------
// Constructor
//-------------------------------------------------------------------
public SigningSurface() {

	// since we are bypassing any registration of listeners, we have
	// to manually enable the set of events we wish to deal with !
	enableEvents(
		AWTEvent.MOUSE_EVENT_MASK |
		AWTEvent.MOUSE_MOTION_EVENT_MASK);
}
//-------------------------------------------------------------------
// SigningSurface (on-screen) redaw routines
// Override update() to eliminate the component erase, but still
// call paint() so that component can repaint itself when windowing
// system orders it.
//-------------------------------------------------------------------
public void update(Graphics g) {
	paint(g);
}
//-------------------------------------------------------------------
public void paint(Graphics g) {

	if ( offscreenImage == null ) {
		width  = getSize().width;
		height = getSize().height;

		// System.out.println("Width = "  + width);
		// System.out.println("Height = " + height);

		offscreenImage = createImage(width, height);
		if ( offscreenImage == null ) {
			System.out.println("ERROR: Couldn't create offscreen..");
		}
		offscreenG = offscreenImage.getGraphics();
	}
	g.drawImage(offscreenImage, 0,0, this);
}
//-------------------------------------------------------------------
// Override event dispatcher methods to catch and process events locally
//-------------------------------------------------------------------
protected void processMouseEvent(MouseEvent mouseEvent) {

	x = mouseEvent.getX();
	y = mouseEvent.getY();

	switch ( mouseEvent.getID() ) {
		case MouseEvent.MOUSE_PRESSED :
			// System.out.println("click at " + x +" "+ y);

			lastX = x;		// note start point for line
			lastY = y;
			repaint();
			break;
		default:
			break;
	}
}

protected void processMouseMotionEvent(MouseEvent mouseMotionEvent) {

	x = mouseMotionEvent.getX();
	y = mouseMotionEvent.getY();

	switch ( mouseMotionEvent.getID() ) {
		case MouseEvent.MOUSE_DRAGGED :
			// System.out.println("draw to " + x +" "+ y);

			offscreenG.drawLine(x,y, lastX,lastY);
			lastX = x;
			lastY = y;
			repaint();
			break;
		default:
			break;
	}
}
//-------------------------------------------------------------------
// getImage() allows clients access to image managed by a SigningSurface
//-------------------------------------------------------------------
public Image getImage() {
	return offscreenImage;
}
//-------------------------------------------------------------------
// wipeSignature() allows clients to erase image managed by a SigningSurface
//-------------------------------------------------------------------
public void wipeSignature() {
	wipeImage(offscreenImage, Color.white, this);
	offscreenG.setColor(Color.black);
	repaint();		// show erased image
}
//-------------------------------------------------------------------
// Wipe an image to some background color
//-------------------------------------------------------------------
public static void wipeImage(Image im, Color col, ImageObserver observer) {
Graphics g;
int width, height;

	g      = im.getGraphics();
	width  = im.getWidth(observer);
	height = im.getHeight(observer);

	g.setColor(col);
	g.fillRect(0,0, width, height);
}
} // End of Class SigningSurface