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)
Se****e ma de ni thui. ("Perhaps thou speakest truth.")
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