import java.applet.Applet;
import java.awt.*;
import netscape.javascript.JSObject;

// This appears in Core Web Programming from
// Prentice Hall Publishers, and may be freely used
// or adapted. 1997 Marty Hall, hall@apl.jhu.edu.

/** An applet that draws a mountain image and displays
 *  a slider. Dragging the slider changes a textfield
 *  in the HTML file containing the applet. Moving the
 *  mouse over the image changes another textfield in the
 *  containing HTML file, using an altitude value
 *  where the bottom of the applet corresponds to 0
 *  and the top to 29000 feet. This requires
 *  an HTML file with a form named "highPeaksForm"
 *  containing two text fields: one named "costField"
 *  and one named "altitudeField". It also requires use
 *  of the MAYSCRIPT tag in the <APPLET ...> declaration.
 *  <B>Works only in Netscape, in version 3.0
 *  or later.</B>.
 */

public class Everest extends Applet {
  private Image mountain;
  private JSObject window, document, highPeaksForm,
          costField, altitudeField;
  private int width, height;

  public void init() {
    setBackground(Color.lightGray);
    mountain = getImage(getCodeBase(),
                        "images/peak5.gif");
    width = size().width;
    height = size().height;
    // Start image loading immediately
    prepareImage(mountain, width, height, this);
    setLayout(new BorderLayout());
    Font sliderFont =
      new Font("Helvetica", Font.BOLD, 18);
    LabeledCostSlider costSlider =
      new LabeledCostSlider("Specify a maximum cost:",
                            sliderFont,
                            2000, 20000, 5000,
                            this);
    add("South", costSlider);
    // Get references to HTML textfields via JavaScript
    window = JSObject.getWindow(this); // this=applet
    document =
      (JSObject)window.getMember("document");
    highPeaksForm =
      (JSObject)document.getMember("highPeaksForm");
    costField =
      (JSObject)highPeaksForm.getMember("costField");
    altitudeField =
      (JSObject)highPeaksForm.getMember("altitudeField");
    setCostField(5000);
    setAltitudeField(15000);
  }

  public void paint(Graphics g) {
    g.drawImage(mountain, 0, 0, width, height, this);
  }

  /** When user moves the mouse, scale the y value
   *  from 29000 (top) to 0 (bottom) and send it
   *  to external textfield through JavaScript.
   */
  
  public boolean mouseMove(Event event, int x, int y) {
    setAltitudeField((height - y) * 29000 / height);
    return(true);
  }

  /** Change textfield via JavaScript. */
  
  public void setCostField(int val) {
    costField.setMember("value",
                        String.valueOf(val));
  }

  /** Change textfield via JavaScript. */
  
  private void setAltitudeField(int val) {
    altitudeField.setMember("value",
                            String.valueOf(val));
  } 
}