Creating a Run-Time IDL Application

QUESTION: I want to have the user start a stand-alone IDL application by double clicking an icon on the display of my Windows machine. Can you show me how to do that in IDL?

ANSWER: First of all, you should know that it is not possible in IDL to create a stand-alone IDL executable. That is, it is not possible to create an IDL program that is capable of being run by someone who doesn't have an IDL license. (See Can I create an IDL executable file? for additional information.)

It is possible, however, to create an IDL application on a Windows machine that runs when the application icon is double clicked. The secret is to use the IDL run-time license that is part of the IDL Windows distribution. Here are the steps I go through to make such an application on my Windows NT machine.

Step 1:

I write a main program that calls my application program. (This main is not strictly necessary, but I find it makes it easier to automate the application building process.) Suppose I want to make a stand-alone application from the XSurface program (an example program that can be downloaded from my web page). I write the Main program like this:

   PRO Main
      XSurface
   END

Step 2:

Open a new IDL session and type these commands:

   IDL> .Compile Main
   IDL> Resolve_All

Since this is a program that uses objects, I must also explicitly compile all of my 'object'__define.pro files, since Resolve_All doesn't think about these files:

   IDL> .Compile Trackball__Define

Step 3:

Save all the compiled modules in a "save" file:

   IDL> Save, /Routines, Filename='main.sav'

Step 3.5:

This step added at the request of Eric Frans, who struggled with this for hours before Dick Jackson (djackson@dfanning.com) bailed him out. Be sure your path does not have any blank characters in it. For example, the path to the save file cannot be "C:\RSI\Program Files\main.sav". This is a bug in all versions of IDL up to IDL 5.2 Beta 2, the last version we checked.

Step 4:

Exit IDL.

Step 5:

If I just want to run the XSurface application, I can now just double-click the main.sav program name with my mouse. If you have difficulty with this step it may be because the sav file extension is not associated with the run-time version of IDL in the Windows Registry. If it is not, open the NT Explorer application, find the View|Options menu, go to the File Types tab, and make sure the association is set up correctly. (I believe, although I am not sure, that in Windows 95 the File Types association may be accessed from a Control Panel program rather from the File Manager. See your Windows 95 documentation.)

Step 6:

If I want to make this file have a different icon (i.e., an "application" icon), I make a shortcut to the main.sav file. Then I right-click on the shortcut, select the Properties menu item, select the Shortcut tab, and click the Change Icon button to select an icon more indicative of my application. I probably also give the shortcut a really nifty name, like PowerVis or something really exciting. :-)

Step 7:

When I run the application, it is as if I were running a built-in application such as Photoshop. There is no evidence of the IDL Development Environment or, for that matter, IDL at all.