// July 2002, java applet by Oliver Knill  for the CCP project
// Vector Fields and Line Integrals  by Oliver Knill and Dale Winter
// Harvard University, Nov 15, 2002. See
// http://www.math.duke.edu/education/ccp/materials/mvcalc/vfield/index.html
// 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 pencil.java vectorfield.java lineintegral.java

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

public class lineintegral extends Applet {

  static final long serialVersionUID = -1L;

  pencil        pencil1;
  vectorfield   vectorfield1;
  double        sum1=0;                        // integral value
  int           vectorfield_choice=1;          // the chosen vectorfield
  boolean       change=false;                  // only erase curve if change=true
  boolean       found=false;                   // line integral has been found?

  public void init() {
     pencil1       = new pencil(500,500);
     vectorfield1  = new vectorfield(500,500);
  }

  public void paint(Graphics g) {
    pencil1.paint(g);
    repaint(); 
  }

  public void update(Graphics g) {
    vectorfield1.menu(g,change,vectorfield_choice); 
    if (change)   { 
       vectorfield1.erase(g); 
       vectorfield1.erase_old_curve(g); 
       change=false; 
    }
    vectorfield1.update(g,vectorfield_choice);
    pencil1.update(g); 
  }

  public boolean mouseDrag(Event event,int x,int y) {
    pencil1.read_pointer(x,y);
    vectorfield1.read_pointer(x,y);
    repaint();
    return true;
  }

  public boolean mouseDown(Event event,int x,int y) {
    pencil1.read_pointer(x,y);
    vectorfield1.read_pointer(x,y);
    if ((Math.abs(y-150)<25) && (Math.abs(x)<50)) { vectorfield_choice=1; change=true; found=false; }
    if ((Math.abs(y-200)<25) && (Math.abs(x)<50)) { vectorfield_choice=2; change=true; found=false; }
    if ((Math.abs(y-250)<25) && (Math.abs(x)<50)) { vectorfield_choice=3; change=true; found=false; }
    if ((Math.abs(y-300)<25) && (Math.abs(x)<50)) { vectorfield_choice=4; change=true; found=false; }
    if ((Math.abs(y-350)<25) && (Math.abs(x)<50)) { vectorfield_choice=5; change=true; found=false; }
    if ((Math.abs(y-400)<25) && (Math.abs(x)<50)) { vectorfield_choice=6; change=true; found=false; }
    if ((Math.abs(y-450)<25) && (Math.abs(x)<50)) { vectorfield_choice=7; change=true; found=false; }
    repaint();
    return true;
  }

}