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Re: Widget Event_Pro question [message #59598 is a reply to message #59480]

Wed, 02 April 2008 08:47

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Spon writes:

> I think I'm already doing what you suggest, but just to be sure:
>
> Graphs = PTR_NEW([-1L])

I wouldn't do this. If there is nothing in it, I would
probably make it a null pointer:

graphs = PTR_NEW()

Then check to see if I had a valid pointer in my code
before I used it.

Or, if you *want* a valid pointer, but don't have anything
to put in it, you can just do this:

graphs = Ptr_New(/ALLOCATE_HEAP)

Now, you have a valid pointer:

IDL> Print, Ptr_Valid(graphs)
1

But, the thing inside it is an undefined variable:

IDL> help, *graphs
<PtrHeapVar1> UNDEFINED = <Undefined>

You can stick something in it:

*graphs = [widgetID]

You can even find out how many things are in it:

IDL> Print, N_Elements(*graphs)

> Oh, and another question while I'm at it: I'm trying to check if a
> widget still exists before trying to load its UVal, I thought that
>
> IF WIDGET_INFO(GraphUVal.GroupLeader, /ACTIVE) THEN BEGIN
>
> would do what I want, but apparently the /ACTIVE keyword doesn't work
> with an argument.

I don't know what ACTIVE does. The keyword you want
is VALID_ID.

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming (www.dfanning.com)
Sepore ma de ni thui. ("Perhaps thou speakest truth.")

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[Message index]

		Widget Event_Pro question By: Spon on Mon, 31 March 2008 04:29
		Re: Widget Event_Pro question By: Spon on Wed, 02 April 2008 09:10
		Re: Widget Event_Pro question By: David Fanning on Wed, 02 April 2008 08:47
		Re: Widget Event_Pro question By: Spon on Wed, 02 April 2008 08:38
		Re: Widget Event_Pro question By: David Fanning on Wed, 02 April 2008 08:23

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