// July 2002, java applet by Oliver Knill  for the CCP project
// Green's Theorem and the Planimeter by Oliver Knill and Dale Winter
// Harvard University, Nov 15, 2002. See
// http://math.duke.edu/education/ccp/materials/mvcalc/green
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License of the Free Software Foundation for
// details.  Compile with 
// javac instrument.java comment.java wheel.java curve.java planimeter.java

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

public class planimeter extends Applet {

  static final long serialVersionUID = -1L;
 
  instrument planimeter1;
  wheel      wheel1;
  curve      curve1;
  comment    comment1;                      

  double     sum1=0;                        // integral value
  boolean    active1=false;                 // went over start point
  int        curve_choice=0;                // the chosen curve 
  boolean    change=false;                  // only erase curve if change=true
  boolean    found=false;                   // line integral has been found?
  boolean    counting=false;                // line integral in progress 

  public void init() {
     planimeter1 = new instrument(500,500);
     wheel1      = new wheel(500,500);
     curve1      = new curve(500,500);
     comment1    = new comment(500,500);
  }

  public void paint(Graphics g) {
    planimeter1.paint(g);
    planimeter1.update(g);
    repaint(); 
  }

  public void update(Graphics g) {
    sum1=wheel1.update(g,active1);
    planimeter1.update(g); 
    counting=wheel1.sum_counting(); 
    curve1.menu(g,change,curve_choice); 
    if (change)   { curve1.erase(g); change=false; }
    if (counting || Math.abs(sum1)<1) { comment1.update(g,sum1); }
    curve1.update(g,active1,curve_choice); 
  }
	
  public boolean mouseDrag(Event event,int x,int y) {
    planimeter1.set_pointer(x,y);
    wheel1.read_pointer(x,y);
    if ((Math.abs(x-430)<5) && (Math.abs(y-200)<5)) { active1=true; } 
    repaint();
    return true;
  }

  public boolean mouseDown(Event event,int x,int y) {
    planimeter1.set_pointer(x,y);
    wheel1.read_pointer(x,y);
    if ((Math.abs(y-150)<25) && (Math.abs(x)<50)) { curve_choice=1; change=true; found=false; }
    if ((Math.abs(y-200)<25) && (Math.abs(x)<50)) { curve_choice=2; change=true; found=false; }
    if ((Math.abs(y-250)<25) && (Math.abs(x)<50)) { curve_choice=3; change=true; found=false; }
    if ((Math.abs(y-300)<25) && (Math.abs(x)<50)) { curve_choice=4; change=true; found=false; }
    if ((Math.abs(y-350)<25) && (Math.abs(x)<50)) { curve_choice=5; change=true; found=false; }
    if ((Math.abs(y-400)<25) && (Math.abs(x)<50)) { curve_choice=6; change=true; found=false; }
    repaint();
    return true;
  }

}