public class MyIONApplet extends Applet  

<APPLET NAME="myIONApplet" CODE=myIONApplet.class
             WIDTH=300 HEIGHT=300 >  
</APPLET>  

CODEBASE="./java"  

// -*-C++-*-  
//  
// commands.java  
//  
//  
  
/*****************************************************************  
 Copyright (c) 1997-2002, ITT Visual Information Solutions, Inc. 
 All rights reserved. Unauthorized reproduction prohibited.  
  
 (Of course, because these are examples, feel free to remove these   
 lines and modify to suit your needs.)  
******************************************************************
/  
  
import java.awt.*;  
import java.applet.*;  
import java.io.*;  
import java.net.*;  
import com.itt.ion.*;   // Import the ION Package  
  
public class commands extends Applet implements 
IONDisconnectListener  
{  
// Instance Vars  
    
   IONGrConnection c_ionCon;  // the ion connection  
   IONGrDrawable   c_ionDrw;  // the ION drawable  
   Dimension       c_dimApp;  // Size of drawing area  
   int             c_bConnected=0; // 0 => !conn, 1 => conn, -1 => 
conn failed  
  
// ******************************  
// Init Method  
// ******************************  
    
  public void init(){  
 // Create connection and drawable objects  
    c_ionCon = new IONGrConnection();  
    c_dimApp = getSize();  
    c_ionDrw = new IONGrDrawable(c_dimApp.width, c_dimApp.height);  
  
 // Add the drawable to the AWT tree  
    setLayout(new GridLayout(1, 1));  
    add(c_ionDrw);  
  }  
/*  
 *************************************************  
 * Inorder to display status messages at startup and also   
 * to be able to disconnect when the page is not being viewed  
 * we override the Applets start() and stop() methods  
 *************************************************  
 * start()  
 *  
 * Purpose:  
 *   Overide the applet's start method.  
 *   Connect to IONJ if not already connected.  
 *  
 * Note: in pre-ION1.4 releases, this method called repaint.   
 * repaint then would call our paint method (now deleted from this   
 * file). The paint method was responsible for connecting.  
 * However, in some cases our paint method would not be called and   
 * the applet would not get its data from the server.    
 * We are now guaranteed that we will connect to the IONJ server   
 * because start() will always be called when the applet starts.  
 */  
  public void start(){   
    if(c_bConnected == 0)  // Not connected to ION, do so.  
      connectToServer();  
  }  
/*  
 *************************************************  
 * stop()  
 *  
 * Purpose:  
 *   Override the applet's stop method. This method  
 *   Is called when the page is not being viewed. We  
 *   disconnect from the server when this is the case.  
 */  
  public void stop(){  
    if(c_bConnected == 1){  
      c_ionCon.removeIONDisconnectListener(this);  
      c_ionCon.disconnect();  
      c_bConnected=0;  
    }  
  }  
  
/*  
 ************************************************  
 * connectToServer()  
 *  
 * Purpose:  
 *  Connects to the ION server, providing feedback to user  
 */  
  private void connectToServer(){  
  
  // Write Status message  
     writeMessage("Connecting to ION Java Server...");  
  
  // Connect to the server  
     try {   
       c_ionCon.connect(this.getCodeBase().getHost());   
     } catch(UnknownHostException eUn) {    
         System.err.println("Error: Unknown Host.") ;         
	     writeMessage("Error:Unknown Host.");  
         c_bConnected = -1;  
	     return;  
     } catch(IOException eIO) {  
         System.err.println("Error: Establishing Connection. ION 
Java Server Down?");  
	     writeMessage("Error: Establishing Connection. ION Java 
Server Down?");  
         c_bConnected = -1;  
	     return;  
     } catch(IONLicenseException eLic){  
         System.err.println("Error: ION Java License Unavailable.") 
;         
	     writeMessage("Error: ION Java License Unavailable.");  
         c_bConnected = -1;  
	     return;  
     }  
  
    c_bConnected = 1;  
    c_ionCon.addIONDisconnectListener(this);  
  
 // Add the drawable to the connection  
    c_ionCon.addDrawable(c_ionDrw);  
  
   writeMessage("Drawing Graphics..."); // message to screen  
 // Issue IDL commands to generate a plot  
    try {  
    // Set the color table  
       c_ionCon.executeIDLCommand("loadct, 15");           
  
    // Create some data  
       c_ionCon.executeIDLCommand("a = dist(30)");        
  
    // Draw a contour plot  
       c_ionCon.executeIDLCommand("show3, a");   
	     
   //Note that it is generally faster to package multiple   
   //IDL commands into a single .pro to call.  This example   
   //sends commands separately so that the code is easier to   
	//follow.  
    } catch(Exception e) {   
      String smsg;  
      if(e instanceof IOException)  
         smsg = "Communication error:"+e.getMessage();   
      else if(e instanceof IONSecurityException )  
         smsg = "ION Java security error";   
      else if(e instanceof IONIllegalCommandException )  
         smsg = "Illegal IDL Command detected on server.";   
      else   
         smsg = "Unknown error: "+e.getMessage();  
      System.err.println("Error: "+smsg);  
      writeMessage("Error: "+smsg);  
      return;  
    }  
    writeMessage("Done");  
 }        
  
/*  
 ************************************************  
 * IONDisconnection()  
 *  
 * Purpose:  
 *  Called when the connection is broken (can report reason).  
 */  
 public void IONDisconnection(int i){  
  System.err.println("Server Connection Closed");  
  writeMessage("Server Connection Closed");  
  if(c_bConnected == 1)  
     c_bConnected = 0;  
 }  
/*  
 ***********************************************  
 * writeMessage()  
 *  
 * Purpose:  
 *   Utility method that is used to write a string to the  
 *   screen using Java.  
 */  
  private void writeMessage(String sMsg){  
    showStatus(sMsg);  
	System.out.println(sMsg);  
  }  
}  

Further Examples

Example code illustrating ION features is included in the installed ION distribution.

See Running the ION Java Examples for more information.

ION Applets and Scripting Languages

You can use scripting languages such as JavaScript and VBScript to control ION applets included on an HTML page by calling ION methods that are available to all applets. Communication between scripts and applets gives you a simple way to create interactive HTML pages that build on ION's pre-built applets.

Browser and Script Language Differences

Two competing scripting languages are currently available for use in HTML pages: JavaScript and VBScript. JavaScript was developed by Netscape for use in its Navigator browser; VBScript was developed by Microsoft for use in its Internet Explorer browser. While the two scripting languages have much in common, they do differ in ways that are beyond the scope of this manual to describe. In the context of writing scripts that communicate with ION applets, the important differences are:

The practical result of this situation is that in order to create HTML pages that allow users of both Netscape's Navigator and Microsoft's Internet Explorer to interact with ION applets via scripts, you must write HTML code that decides "on the fly" which scripting language to use.

Choosing Between JavaScript and VBScript

The simplest way to provide pages that use JavaScript for Netscape browsers and pages that use VBScript for Microsoft browsers is to use a "gateway" HTML page that loads one of two other HTML pages depending on the type of browser. The following HTML page uses JavaScript statements to detect whether the browser accessing the page is Netscape Navigator. If so, it loads a JavaScript version of the HTML page; otherwise it loads a VBScript version of the HTML page.

<HTML>  
<! This page refers IE or Netscape to the proper ION example >  
<SCRIPT language=JavaScript>  
// <!--  
var browser = navigator.appName;  
  
if (browser.indexOf ("Netscape") != -1)  
   location = "javascript.html";  // jump to JavaScript page  
else  
   location = "vbscript.html";    // jump to VBScript page  
// -->  
</SCRIPT>  
</HTML>  

Methods Available

The following methods are available for communication between scripting languages and ION applets:

executeIDLCommand('string')

where string is a valid IDL command string. The executeIDLCommand() method allows you to execute any IDL command via a script, with IDL's output going to the specified applet's drawing area.

For example, if you have an IONSurfaceApplet named MYSURF, you could use the following JavaScript statement to change the color table when the user presses a button:

document.MYSURF.executeIDLCommand("LOADCT, 5");  

See Example: Using JavaScript for a more complete discussion.

disconnect()

Use this method to disconnect from the ION Server.

Example: Using JavaScript

The following HTML code demonstrates the use of JavaScript to interactively update an ION graphic. The example includes an IONGraphicApplet that displays a shaded surface, uses a JavaScript select object to create a pulldown list of rotation values, and adds a button to rotate the surface to the selected angle.

<!-- Define the HTML header. Note that the JavaScript is  
     included in the HEAD section. -->  
<HTML>  
<HEAD>  
 <TITLE>Simple JavaScript Applet Test</TITLE>  
<!-- The script language is JavaScript. We declare the variable 
rotation with an initial value of 30 degrees. -->  
<SCRIPT language=JavaScript>  
   var rotation = "30";  
  
// The getSelectedValue() function returns the text associated  
// with the value chosen from the pulldown list.  
  
function getSelectedValue(sel) {  
   return sel.options[sel.selectedIndex].text  
 }  
  
// The rot_surf() function retrieves the rotation value and  
// executes the IDL command to re-draw the graphic. It is called  
// when the button is clicked.  
  
function rot_surf() {  
   rotation = getSelectedValue(document.command_form.rot_value);  
   document.SURFAPP.executeIDLCommand("SHADE_SURF, a, 
       AZ="+rotation);  
 }  
</SCRIPT>  
</HEAD>  
<BODY>  
<!-- JavaScript input controls must be contained in an   
     HTML form. -->  
<FORM NAME="command_form">  
  
<!-- Create an IONGraphicApplet applet named "SURFAPP" that  
generates some data and creates a shaded surface. Note that the  
CODEBASE attribute is set to "../classes". This is the proper path  
for the example as installed with the ION documentation   
files.-->  
  
<APPLET NAME="SURFAPP" CODE=com.itt.ion.IONGraphicApplet.class  
   CODEBASE="../classes" WIDTH=200 HEIGHT=200>  
   <PARAM NAME="DEBUG_MODE" VALUE="YES">  
   <PARAM NAME="SERVER_DISCONNECT" VALUE="NO">  
   <PARAM NAME="DECOMPOSED_COLOR" VALUE="NO">  
   <PARAM NAME="IDL_COMMAND_0"   
          VALUE="a = EXP(-(SHIFT(DIST(30), 15, 15)/7)^2)">  
   <PARAM NAME="IDL_COMMAND_1" VALUE="LOADCT, 5">  
   <PARAM NAME="IDL_COMMAND_2" VALUE="SHADE_SURF, a">  
</APPLET>  
<BR>  
<!-- Create the pulldown menu of rotation values -->  
<SELECT NAME="rot_value" SIZE=1>  
<OPTION VALUE=15>15  
<OPTION VALUE=30 SELECTED>30  
<OPTION VALUE=45>45  
<OPTION VALUE=60>60  
<OPTION VALUE=75>75  
<OPTION VALUE=90>90  
</SELECT>   
  
<!-- Create the "Rotate Surface" button, which calls the 
JavaScript function rot_surf().-->  
<INPUT TYPE=BUTTON NAME="rot_button" VALUE="Rotate Surface"  
onClick="rot_surf()">  
</FORM>  
</BODY>  
</HTML>  

See Notes on the Differences Between the JavaScript and VBScript Versions.

Example: Using VBScript

The following HTML code demonstrates the use of VBScript to interactively update an ION graphic. The example includes an IONGraphicApplet that displays a shaded surface, uses a VBScript select object to create a pulldown list of rotation values, and adds a button to rotate the surface to the selected angle. The line numbers are provided to aid in discussion; they are not part of the HTML code.

<!-- Define the HTML header. Note that the VBScript is included in 
the HEAD section. -->  
<HTML>  
<HEAD>  
 <TITLE>Simple VBScript Applet Test</TITLE>  
<!-- The script language is VBScript. We declare the variable  
     rotation with an initial value of 30 degrees. -->  
 <SCRIPT language=VBScript>  
   Dim rotation  
   rotation = "30"  
  
  
// The rot_button_OnClick() subroutine retrieves the index of  
// the value selected in the pulldown list, uses the index to  
// retrieve the text value, and executes the IDL command to redraw  
// the graphic.  
  
 sub rot_button_OnClick()  
   ind = document.command_form.rot_value.selectedIndex  
   rotation = document.command_form.rot_value.options(ind).value  
   document.SURFAPP.executeIDLCommand("SHADE_SURF, a, 
        AZ="+rotation)  
 end sub  
 </SCRIPT>  
</HEAD>  
<BODY>  
  
<!-- Create an IONGraphicApplet applet named "SURFAPP" that  
generates some data and creates a shaded surface. Note that the  
CODEBASE attribute is set to "../classes". This is the proper path  
for the example as installed with the ION documentation   
files. -->  
  
<APPLET NAME="SURFAPP" CODE=com.itt.ion.IONGraphicApplet.class  
   CODEBASE="../classes" WIDTH=200 HEIGHT=200>  
   <PARAM NAME="DEBUG_MODE" VALUE="YES">  
   <PARAM NAME="SERVER_DISCONNECT" VALUE="NO">  
   <PARAM NAME="DECOMPOSED_COLOR" VALUE="NO">  
   <PARAM NAME="IDL_COMMAND_0"   
          VALUE="a = EXP(-(SHIFT(DIST(30), 15, 15)/7)^2)">  
   <PARAM NAME="IDL_COMMAND_1" VALUE="LOADCT, 5">  
   <PARAM NAME="IDL_COMMAND_2" VALUE="SHADE_SURF, a">  
</APPLET>  
  
<!-- VBScript input controls must be contained in an   
     HTML form. -->  
<FORM NAME="command_form">  
   <BR>  
  
   <!-- Create the pulldown menu of rotation values. -->  
   <SELECT NAME="rot_value" SIZE=1>  
      <OPTION VALUE=15>15  
      <OPTION VALUE=30 SELECTED>30  
      <OPTION VALUE=45>45  
      <OPTION VALUE=60>60  
      <OPTION VALUE=75>75  
      <OPTION VALUE=90>90  
   </SELECT>   
  
   <!-- Create the "Rotate Surface" button. The  
        rot_button_OnClick() subroutine is called automatically  
        when this button is clicked. -->  
   <INPUT TYPE=BUTTON NAME="rot_button" VALUE="Rotate Surface">  
</FORM>  
</BODY>  
</HTML>