/** MyApplet9.java: Interactive Line Drawing and Mouse Events
 ** Assignment:  Modify this file centering the click
 ** instruction at the top of the applet, and changing
 ** it so that instead of drawing lines, it has some other
 ** unusual (weird?) behavior to entertain (befuddle?)
 ** the user.
 ** Also, take a look at the MyApplet9.html webpage
 ** file for displaying this applet.                          **/

/** USE EXISTING JAVA CLASSES **/

import java.awt.*;
import java.applet.Applet;

/** EXTEND THE JAVA APPLET CLASS **/

public class MyApplet9 extends Applet
   {
    Font font = new Font("TimesRoman", Font.BOLD, 18);
    final int maxnumlines = 20;               // Define max number of lines,
    final int maxsize = maxnumlines + 5;      // max array size,
    Point startpoint[] = new Point[maxsize];  // the array of start points,
    Point endpoint[] = new Point[maxsize];    // the array of end points,
    Point anchorpoint, connectpoint;          // the current anchor point and
    int entrynum = 0;                         // connection point, and the
                                              // current array entry number,
                                              // starting with 0 (instead of 1).
    public void init()
       {
        setBackground(Color.white);      // Change the gray background to white.
        }

     /** HANDLE THE MOUSEDOWN EVENT **/

     public boolean mouseDown(Event e, int x, int y)
	{
         if (entrynum < maxsize)
	  {
           anchorpoint = new Point(x,y);     // Initialize both points to
	   connectpoint = anchorpoint;       // the current mouse position.
	   return true;                      // Note that this will give us a
           }                                 // way to prevent painting a single
	 else                                // point (see the mouseUp method).
	  {
           return false;
           }
	 }

     /** HANDLE THE MOUSEDRAG EVENT **/

     public boolean mouseDrag(Event e, int x, int y)
	{
         if (entrynum < maxsize)           // A mouseDrag event occurs only
	  {                                // when the mouse is moved. So,
           connectpoint = new Point(x,y);  // we must have connectpoint !=
	   repaint();                      // anchorpoint, which ensures that
	   return true;                    // a temporary (purple) line will
           }                               // be painted (see the paint method).
	 else
	  {
           return false;
           }
	 }

     /** HANDLE THE MOUSEUP EVENT **/

     public boolean mouseUp(Event e, int x, int y)
	{
         if (entrynum < maxsize && connectpoint != anchorpoint)
	  {                                    // Don't add a single point.
           addline();                          // Add new points to the arrays.
	   repaint();                          // Repaint everything, including
	   return true;                        // the new line (all blue).
           }
	 else
	  {
          return false;
          }
	 }

     /** THE ADDLINE METHOD **/

     void addline()
	{
         startpoint[entrynum] = anchorpoint;// Record the startpoint and
	 endpoint[entrynum] = connectpoint;// endpoint of the new line.
	 entrynum++;                       // Add 1 to the current entry number.
	 anchorpoint = null;               // Nullifying these points prevents
	 connectpoint = null;              // the line from being painted twice
	 }                                 // (see the paint method).

    /** CREATE THE CURRENT FRAME **/

    public void paint(Graphics g)
       {
        g.setColor(Color.blue);
        g.setFont(font);
        g.drawString("Click and Drag in Window", 100, 20);
	for (int i = 0; i < entrynum; i++)    // Note that nothing happens here,
	  {                                   // until a mouseDown event occurs.
           if (i < maxnumlines)               // Repaint all lines from 0 to
	    {                                 // maxnumlines-1.
             g.drawLine(startpoint[i].x, startpoint[i].y,
			    endpoint[i].x, endpoint[i].y);
             }
	   else
	    {
             g.setColor(Color.red);          // Also, if entrynum > maxnumlines,
	     g.drawString("Sorry, line quota exceeded !!",// then print this
			    endpoint[i].x, endpoint[i].y);// instead of any
             }                                            // extra line.
	   }
	if (connectpoint != anchorpoint)   // Paint a temporary purple line
	 {                                 // in response to a mouseDrag event.
          g.setColor(Color.magenta);
	  g.drawLine(anchorpoint.x, anchorpoint.y,
		      connectpoint.x, connectpoint.y);
          }
	}
    }