Introduction to the Figure Package - Response to keypresses

Sample Code in which a figure responds to keypresses

Here is a sample figure just containing a set of axes, a label and a subfigure consisting of a rose with three petals. Pressing the key "b" causes the rose petals to rotate backwards. Pressing any other key casues them to rotate forwards.

              /*  File:  keyRose.java    */

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

 

public class  keyRose extends Applet {

   Figure canvas ;
   fSubFigure subfig ;

   public void init() {

      canvas = new Figure(this,6,6) ;
      this.add(canvas) ;

      canvas.limits(-300,-300,300,300) ;
      canvas.showCoords = true ;
      canvas.useZoom = true ;     
      canvas.useDrag = true ;

      canvas.append(new fAxes("x axis","y axis") ) ;    
      subfig= new fSubFigure() ;
      subfig.append(new fCurve(new rose(200,3),
                               0,Math.PI,
                               fCurve.CLOSED+fCurve.FILLED)) ;
      canvas.append(new fEnv("fillColor", Color.yellow)) ;
      canvas.append(subfig) ;
      canvas.append(new fLabel(100,50,"cc","Petal")) ;

      canvas.toScreen() ;
   }

   public boolean keyDown(Event e, int key) {
      if ( key-96 == 2 )  subfig.rotate(-Math.PI/8) ;
      else  subfig.rotate(Math.PI/8) ;
      canvas.toScreen() ;
      return true ;
   }
     
}


class rose implements S2V {

   double radius ;
   int noPetals ;

   public rose(double radius, int noPetals) {
      this.radius = radius ;
      this.noPetals = noPetals ;
   }

   public double[] map(double t) {
      double[] out = new double[2] ;
      out[0] = radius*Math.cos(t)*Math.sin(noPetals*t)  ;
      out[1] = radius*Math.sin(t)*Math.sin(noPetals*t)  ;
      return out ;
   }

}

To execute this you would have to save the above program to a file named keyRose.java and you would also have to create a file called keyRose.html and containing

<HEAD><TITLE>Figure Test Program</TITLE></HEAD>
<BODY>
<H1>Figure Test Program </H1>

<P>
<APPLET code="keyRose.class" width=600 height=600></APPLET>

</BODY>

You then compile and execute the program using

     javac keyRose.java
     appletviewer keyRose.html &