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Re: Problem with INFO definition [message #45176 is a reply to message #45175]

Tue, 16 August 2005 08:57

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

pravesh.subramanian@gmail.com writes:

> I am a big fan of David's book and I like the way Info structure has
> been used. I use the same method to handle data to be passed around.
> In one of my Event handler proc, I am returned a 1-d array which I
> would like to put in Info.
> Since I do not know the size of this array, how is it possible to
> define this 1-d array in the INFO structure in the Widget Def. Module?
>
> currently, I do something like this...
>
> 1-d = bytarr(32000)
> ...
>
> info = { $
> ......
> 1-d: 1-d $
> }
>
> I really donno what size this array could take (anything between 0 and
> 32000).
> Is there a way to define this element in the event handler and not the
> WDM? What if the size of this array is not fixed (say the 32000 factor
> is not available).

Anytime you have information in the info or state structure
and you don't know how big it is, or the size might be changing,
you use a pointer to store it. This doesn't change the size
of the info structure, and allows you to redefine your data
at will.

info = { $
....
data: Ptr_New(), $
}

When you go to fill it up:

IF Ptr_Valid(info.data) THEN $
*info.data = data ELSE info.data = Ptr_New(data)

Of course, you need to free the pointer in the CLEANUP
method of the widget program, so you don't leak memory
when your widget program is destroyed.

Cheers,

David

P.S. I thought this was explained pretty well in that
darn book. :-)
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/

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[Message index]

		Re: Problem with INFO definition By: pravesh.subramanian on Wed, 17 August 2005 06:02
		Re: Problem with INFO definition By: K. Bowman on Tue, 16 August 2005 13:36
		Re: Problem with INFO definition By: David Fanning on Tue, 16 August 2005 09:42
		Re: Problem with INFO definition By: pravesh.subramanian on Tue, 16 August 2005 09:05
		Re: Problem with INFO definition By: David Fanning on Tue, 16 August 2005 08:57

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