/*
 * Gary Cornell and Cay S. Horstmann, Core Java (Book/CD-ROM)
 * Published By SunSoft Press/Prentice-Hall
 * Copyright (C) 1996 Sun Microsystems Inc.
 * All Rights Reserved. ISBN 0-13-565755-5
 *
 * Permission to use, copy, modify, and distribute this 
 * software and its documentation for NON-COMMERCIAL purposes
 * and without fee is hereby granted provided that this 
 * copyright notice appears in all copies. 
 * 
 * THE AUTHORS AND PUBLISHER MAKE NO REPRESENTATIONS OR 
 * WARRANTIES ABOUT THE SUITABILITY OF THE SOFTWARE, EITHER 
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A 
 * PARTICULAR PURPOSE, OR NON-INFRINGEMENT. THE AUTHORS
 * AND PUBLISHER SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED 
 * BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING 
 * THIS SOFTWARE OR ITS DERIVATIVES.
 */
 
/**
 * @version 1.00 07 Feb 1996 
 * @author Cay Horstmann
 */

import java.awt.*;

public class ScrollTest extends Frame
{  public ScrollTest()
   {  setTitle("ScrollTest");
      add("East", vert = new Scrollbar(Scrollbar.VERTICAL));
      add("South", horiz = 
         new Scrollbar(Scrollbar.HORIZONTAL));
      add("Center", canvas = new SquareCanvas());
   }

   public boolean handleEvent(Event evt)
   {  if (evt.id == Event.WINDOW_DESTROY) System.exit(0);
      else if (evt.id == Event.WINDOW_MOVED)
      {   Dimension d = canvas.size();
          horiz.setValues(horiz.getValue(), d.width, 0, 600);
          vert.setValues(vert.getValue(), d.height, 0, 400);
      }
      else if (evt.id == Event.SCROLL_ABSOLUTE
         || evt.id == Event.SCROLL_LINE_DOWN
         || evt.id == Event.SCROLL_LINE_UP 
         || evt.id == Event.SCROLL_PAGE_DOWN 
         || evt.id == Event.SCROLL_PAGE_UP)
      {  canvas.translate(horiz.getValue(), vert.getValue());
         return true;
      }
      return super.handleEvent(evt);
   }
   
   public void show()
   {  super.show();
      Dimension d = canvas.size();
      horiz.setValues(0, d.width, 0, 600);
      vert.setValues(0, d.height, 0, 400);
   }
   
   public static void main(String args[])
   {  Frame f = new ScrollTest();
      f.resize(300, 200);
      f.show();
   }

   private Scrollbar horiz;
   private Scrollbar vert;
   private SquareCanvas canvas;   
}


class SquareCanvas extends Canvas
{  public void translate(int x, int y)
   {  dx = x;
      dy = y;
      repaint();
   }
   
   public void paint(Graphics g)
   {  g.translate(-dx, -dy);
      for (int i = 0; i < nsquares; i++)
         draw(g, i);
   }
   
   public int find(int x, int y)
   {  for (int i = 0; i < nsquares; i++)
         if (squares[i].x <= x 
               && x <= squares[i].x + SQUARELENGTH
               && squares[i].y <= y 
               && y <= squares[i].y + SQUARELENGTH)
            return i;
      return -1;
   }

   public void draw(Graphics g, int i)
   {  g.drawRect(squares[i].x, squares[i].y, SQUARELENGTH,
      SQUARELENGTH);
   }

   public void add(int x, int y)
   {  if (nsquares < MAXNSQUARES)
      {  squares[nsquares] = new Point(x, y);
         nsquares++;
         repaint();
      }
   }

   public void remove(int n)
   {  nsquares--;
      squares[n] = squares[nsquares];
      if (current == n) current = -1;
      repaint();
   }

   public boolean mouseDown(Event evt, int x, int y) 
   {  x += dx; y += dy;
      current = find(x, y);
      if (current < 0) // not inside a square
      {  add(x, y);
      }
      else if (evt.clickCount >= 2)
      {  remove(current);
      }
      return true;
   }

   public boolean mouseDrag(Event evt, int x, int y) 
   {  x += dx; y += dy;
      if (current >= 0)
      {  Graphics g = getGraphics();
         g.translate(-dx, -dy);
         g.setXORMode(getBackground());
         draw(g, current);      
         squares[current].x = x;
         squares[current].y = y;
         draw(g, current);      
         g.dispose();
      }
      return true;       
   }
   
   private static final int SQUARELENGTH = 10;

   private static final int MAXNSQUARES = 100;
   private Point[] squares = new Point[MAXNSQUARES];
   private int nsquares = 0;
   private int current = -1;
   private int dx = 0;
   private int dy = 0;
}