| Re: Update text widget [message #65243 is a reply to message #65242] |
Thu, 19 February 2009 07:55   |
Michi
Messages: 9
Registered: December 2007
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Junior Member |
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David, I have the impression that you could recommend a book, too?
Just in case someone couldn't locate it? ;)
(I can recommend that book very much. ITTVIS should pay DF, because
without him, or without his website, IDL would be totally unusable for
beginners. Oh, and for some experts as well).
On Feb 19, 3:27 pm, David Fanning <n...@dfanning.com> wrote:
> titan writes:
>> I'm trying to write my own first widget but probably I'm missing
>> something about the event handler.
>
>> I would like to create a widget text with 4 rows. these rows are
>> created as insensitive and I would like to make them sensitive when
>> each of these processes occur.
>
>> How can I "communicate" to my widget that the process started and
>> after some calculations it is finished and then update my widget???
>
> You can "communicate" with a widget by sending it
> events. These events can be generated by graphical
> user interface objects (buttons, text widgets, and
> the like), or you can just make up an event and send
> it to a widget, assuming you know the identifier of
> that widget, with Widget_Control and the SEND_EVENT
> keyword.
>
> Your widget has not been built in a way that will generate
> any events, so you are unlikely to ever find yourself
> in your event handler. :-)
>
> A good thing, too, since as was pointed out, you are
> using variables in your event handler (text, text1_,
> and text1_msg) that are not defined in that procedure.
> IDL does not take kindly to using undefined variables in
> expressions. :-(
>
> So, the first thing you need to learn is how to get information
> you need in the event handler *into* the event handler. One way
> information comes into your event handler is via the event
> structure. But the event structure contains extremely limited
> information. It will not know the identifiers of any of your
> text widgets, for example. And without those identifiers, you
> have absolutely no way of interacting with them, since the ONLY
> way of interacting with widgets is via their identifiers.
>
> There are a couple of ways of getting the information you need
> where you need it. But the idea that comes immediately to mind,
> common blocks, is the worst possible one. :-)
>
> Go to some reputable web site (I could suggest one if you can't
> find one) and find a widget program. See how information is passed
> in that program. And I would locate a good book on IDL, too. I think
> it will be extremely difficult to learn to write decent widget programs
> if all you have to go on is the IDL documentation.
>
> Widget programming is not difficult, once you get your head around
> how events happen and are processed (one at a time), and how to
> find the information you need to do whatever it is you need to do.
>
> Cheers,
>
> David
> --
> David Fanning, Ph.D.
> Fanning Software Consulting, Inc.
> Coyote's Guide to IDL Programming:http://www.dfanning.com/
> Sepore ma de ni thui. ("Perhaps thou speakest truth.")
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