Re: how to find the TLB of a widget

[davidf(at)dfanning.com (David Fanning)]

Jonathan Joseph (jj21@cornell.edu) writes:

> Is there a simple way (other than recursively getting the parent)
> to find the Top-level base of a widget.  I don't have an event
> structure to query (which stores it as one of it's fields).
> 
> It seems that it should be obtainable in one fell swoop using
> widget_info or widget_control, but I can't seem to find
> it if it is there.
> 
> Shall I bother to write the routine get_tlb (OK, I've already
> written as it is so trivial)  or does such already exist.

No event structure!? Weird.

Then why not pass it as a parameter into whatever program
needs the information.

IDL makes it trivially easy to pick out any widget in 
a widget hierarchy by using the FIND_BY_UNAME keyword
to WIDGET_INFO. For example, you could define the widget
that carried your info structure (a label widget in this
case) like this:

   infoCarrierID = Widget_Label(base, Value='Columns:', $
      UName='INFO_CARRIER')

Then find it (usually) in any event handler like this:

   infoCarrierID = Widget_Info(event.id, Find_By_UName='INFO_CARRIER')

This is particularly useful in compound widgets, where the
info structure cannot be stored in the top-level base.

Cheers,

David
-- 
David Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438 E-Mail: davidf@dfanning.com
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