//
// HelloWeb3 applet example.
// Source:  _Exploring Java_, Niemeyer & Peck.
// Modified by:  B. Massingill.
//
// Description:
//      A HelloWeb3 applet displays an environment-selected message 
//      and allows the user to drag it around with the mouse.
//      It also provides a "change color" button that, when clicked,
//      changes the color of the message, cycling through a 
//      pre-defined list of colors.
//
// Usage:
//      Applet tag parameter "message" gives message to display.
//      Requires window sufficiently large to display selected
//              message, starting at position (125, 95).
//      Responds to click-and-drag operations on displayed messages.
//      Responds to button clicks.
//
import java.applet.Applet ;
import java.awt.* ;
import java.awt.event.* ;

public
class HelloWeb3
extends Applet 
implements MouseMotionListener, ActionListener {

        int messageX = 125, messageY = 95 ;
        String theMessage ;
        Button theButton ;
        int colorIndex = 0 ;    
        static Color[] someColors = {
                Color.black, Color.red, Color.green,
                Color.blue, Color.magenta
                } ;

        // ---- overridden superclass methods --------------------------

        // init:  get message, set things up.
        public void
        init() {
                theMessage = getParameter("message") ;

                // create "change color" button
                theButton = new Button("Change Color") ;
                add(theButton) ;

                // set up to process mouse and button events
                addMouseMotionListener(this) ;
                theButton.addActionListener(this) ;
        }

        // paint:  display message at current location.
        public void 
        paint(Graphics gc) {
                gc.drawString(theMessage, messageX, messageY) ;
        }

        // ---- methods to handle mouse events -------------------------

        // respond to "mouse dragged" events by changing location
        //      of displayed message.
        public void
        mouseDragged(MouseEvent e) {
                messageX = e.getX() ;
                messageY = e.getY() ;
                repaint() ;
        }

        // ignore "mouse moved" events.
        public void
        mouseMoved(MouseEvent e) {
        }

        // ---- methods to handle button events ------------------------

        // respond to click on "change color" button.
        public void
        actionPerformed(ActionEvent e) {
                if (e.getSource() == theButton) changeColor() ;
        }

        // ---- methods to set, obtain current color for message -------
        //      synchronized to avoid simultaneous access to colorIndex
        //      by changeColor and currentColor.

        // changeColor:  reset foreground color, repaint.
        synchronized private void
        changeColor() {
                if (++colorIndex == someColors.length) colorIndex = 0 ;
                setForeground(currentColor()) ;
                repaint() ;
        }

        synchronized private Color
        currentColor() {
                return someColors[colorIndex] ;
        }
}