Class Protractor

src/org/opensourcephysics/display/Protractor.java:26–183

A Protractor with an arrow that can be used to measure angles. @author W. Christian @version 1.0

 * @version 1.0
 */
public class Protractor extends InteractiveCircle implements Drawable {
  static final double PI2 = Math.PI*2;
  static final String thetaStr = "$\\theta$=";          //$NON-NLS-1$
  int protractorRadius, protractorRadius2, arrowLengthPix;
  protected Tip tip = new Tip();
  protected double arrowTheta = 0, orientation = 0;
  protected DecimalFormat f = org.opensourcephysics.numerics.Util.newDecimalFormat("000"); //$NON-NLS-1$
  protected boolean showTheta = false;
  protected InteractiveLabel tauBox = new InteractiveLabel(thetaStr+f.format(getTheta()));

  /**
   * Constructs a protractor with the given pixel size.
   *
   * @param protractorRadius int
   */
  public Protractor(int protractorRadius) {
    this.protractorRadius = protractorRadius;
    protractorRadius2 = protractorRadius*2;
    arrowLengthPix = protractorRadius;
    tip.color = Color.BLUE;
    tauBox.setOffsetX(-20);
    tauBox.setOffsetY(5);
  }

  /**
   * Constructs a protractor with a default radius of 40 pixels.
   */
  public Protractor() {
    this(40);
  }

  /**
   * Sets the angle of the arrow on the protractor.
   * @param theta double
   */
  public void setTheta(double angle) {
    this.arrowTheta = angle+orientation;
  }

  /**
   * Gets the angle of the arrow on the protractor.
   * @return double
   */
  public double getTheta() {
    // return PBC.separation(arrowTheta-orientation,Math.PI*2);
    // inline the method for efficiency and to decouple from the numerics package
    double dr = arrowTheta-orientation;
    return dr-PI2*Math.floor(dr/PI2+0.5);
  }

  /**
   * Sets the orientation of the protractor.
   * @param angle double
   */
  public void setOrientation(double angle) {
    this.orientation = angle;
  }