// 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 -O instrument.java comment.java wheel.java curve.java planimeter.java

import java.lang.Math;
import java.awt.*;

class instrument {

private int h,w;
private int x,y,x1,y1;    
private double u,v,u1,v1; 

private int i,j;                                // indices
private int wr;                                 // wheel radius
private int wf;                                 // number vectors in each dimension
private int x_cen,y_cen;                        // instrument center
private int a,b,a1,b1;                          // knew center
private int c,d,c1,d1; 
private double  aa,bb,aa1,bb1; 
private int a_old,b_old;
private int c_old,d_old;
private int x_old,y_old;
private double r,r1; 
private double l;                               // knee length of instrument

private int left_border=80;                     // left border for menu

public instrument(int width,int height) {
  this.w = width;   this.h = height;
  wr       = (int) w/70;                        
  wf       = 3;                                 
  l        = (int) w/4;                        
  x_cen    = w/2;            y_cen    = h/2;    
  x        = x_cen+100;      y        = y_cen; 
}

public void set_pointer(int x, int y) { this.x = x; this.y = y; }
public void set_pointer2(int x, int y) { this.x = x+100; this.y = y+100; }

public void paint(Graphics g) {
    g.setColor(Color.black);
    g.fillRect(0,0,w,h);
}

public void update( Graphics g ) {

  if (x_old>left_border) {

  g.setColor(new Color(0,0,0));               // erase old center
  for (i=0; i<5; i++) {                       
    g.drawOval(x_cen-3*i,y_cen-3*i,6*i,6*i);
  }
  g.drawOval(x_cen-1,y_cen-1,2,2);


  g.setColor(Color.black         );            // erase old planimeter
  for (i=-1; i<2; i++)  for (j=-1;j<2; j++) { 
    g.drawLine(x_cen+i, y_cen+j,a_old+i, b_old+j);
    g.drawLine(a_old+i, b_old+j, x_old+i, y_old+j);	
  }
  g.drawOval(x_old-wr, y_old-wr, 2*wr, 2*wr);
  g.drawOval(a_old-4,b_old-4,8,8);
  g.drawOval(x-1,y-1,2,2);                
  g.drawOval(a-1,b-1,2,2);                
  g.drawLine(x_old,y_old,c_old,d_old);

for (i=-wf; i<wf; i++) {                       // erase old vector field
    for (j=-wf; j<wf; j++) {
       if ((i*i+j*j)<wf*wf-1) {
       x1=x_old+i*20;  y1=y_old+j*20;
       u1  = (x1-w/2);   v1 = (y1-h/2);
       r1 = Math.sqrt(u1*u1+v1*v1);
       if (r1>(2*l)) { r1=2*l; }; if (r1==0) {r1=1; }
       aa1 = r1/2; bb1=Math.sqrt( l*l-r1*r1/4 );
       a1  = (int) (w/2+( aa1*u1 + bb1*v1)/r1);
       b1  = (int) (h/2+(-bb1*u1 + aa1*v1)/r1);
       c1  = (int) (x1+15*(y1-b1)/l);
       d1  = (int) (y1-15*(x1-a1)/l);
       g.setColor(Color.black);
       g.drawLine(x1,y1,c1,d1); 
       g.drawOval(c1-1,d1-1,2,2);
       }
    }
  }

  }                                            // end if bracket

  if (x>left_border) {                         // don't draw over menu

  u  = (x-w/2);   v  = (y-h/2);                // calculate new situation
  r = Math.sqrt(u*u+v*v); 
  if (r>(2*l)) { r=2*l; }; if (r==0) {r=1; }
  aa = r/2; bb=Math.sqrt( l*l-r*r/4 );
  a  = (int) (w/2+( aa*u + bb*v)/r);     
  b  = (int) (h/2+(-bb*u + aa*v)/r); 
  c  = (int) (x+15*(y-b)/l); 
  d  = (int) (y-15*(x-a)/l);  

  
  for (i=-wf; i<wf; i++) {                     // draw new vector field
    for (j=-wf; j<wf; j++) {
       if ( (i*i+j*j)<wf*wf-1) {
       x1=x+i*20;  y1=y+j*20; 
       u1  = (x1-w/2);   v1 = (y1-h/2); 
       r1 = Math.sqrt(u1*u1+v1*v1);
       if (r1>(2*l)) { r1=2*l; }; if (r1==0) {r1=1; }
       aa1 = r1/2; bb1=Math.sqrt( l*l-r1*r1/4 );
       a1  = (int) (w/2+( aa1*u1 + bb1*v1)/r1);  
       b1  = (int) (h/2+(-bb1*u1 + aa1*v1)/r1);
       c1  = (int) (x1+15*(y1-b1)/l);
       d1  = (int) (y1-15*(x1-a1)/l);
       g.setColor(new Color(255,155,0));
       g.drawLine(x1,y1,c1,d1); 
       g.setColor(new Color(255,255,0));
       g.drawOval(c1-1,d1-1,2,2);
       }
    }
  }
   
  g.setColor(new Color(0,0,255));              // draw new planimeter
  for (i=-1; i<2; i++)  for (j=-1;j<2; j++) { 
    g.drawLine(x_cen+i, y_cen+j, a+i, b+j);
    g.drawLine(a+i, b+j, x+i, y+j );	
  }
  g.setColor(new Color(120,120,255));
  g.drawOval(a-4,b-4,8,8); 

  g.setColor(new Color(255,255,255));
  g.drawOval(x_cen-1,y_cen-1,2,2);
  g.drawOval(x-1,y-1,2,2); 
  g.drawOval(a-1,b-1,2,2); 

  g.setColor(new Color(127,127,255));
  g.drawOval(x-wr, y-wr, 2*wr, 2*wr);

  g.setColor(new Color(255,155,0));
  g.drawLine(x,y,c,d);
  g.setColor(new Color(255,255,0));
  g.drawOval(c-1,d-1,2,2);



  for (i=0; i<5; i++) {                       // draw center
    g.setColor(new Color(50*i,50*i,255));
    g.drawOval(x_cen-3*i,y_cen-3*i,6*i,6*i);
  }
  g.setColor(new Color(200,200,255));
  g.drawOval(x_cen-1,y_cen-1,2,2);


  }                                            // end if bracket
 

  a_old=a; b_old=b;                            // store old situation
  x_old=x; y_old=y; 
  c_old=c; d_old=d; 

}

}