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Re: EVENT_PRO [message #73771 is a reply to message #40935]

Mon, 29 November 2010 11:02

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Paul van Delst writes:

> Or maybe "MotionControl::SaveData" and "MotionControl::OpenData" ?
>
> Can objects be used this way in widget programming? If not, does the Catalyst library do all the necessary heavy lifting?
>
> I'm at the tipping point of wanting to learn something new in IDL widget-y stuff now that I'm IDL-OO-enthused. Using IDL
> objects has made my code design a lot easier to understand (despite the necessary increase in actual LOC) and if there's
> one thing my IDL widget programs can greatly benefit from, it's better design!

Well, I can't even remember the details of how
Catalyst does this, so yes, I presume it does
all the necessary heavy lifting. It does just
seem to work. :-)

All widget events in the Catalyst Library (where all
widgets are objects) go to a single "event dispatcher".
(You can find this in the Utilities directory.) The
event dispatcher's job is to determine where the event
should be sent. Each widget has a container with
"event objects" stored there. The event dispatcher
essentially collects the event objects and calls the
EventHandler method on these event objects.

This means that in a Catalyst application a single
"event" might be sent to several different "event
handlers", rather than to a single event handler,
as happens in a strict widget program.

In Catalyst you assign an "event handler" to a widget
with the EVENT_OBJECT keyword. There is an optional
EVENT_METHOD keyword that can be used select the actual event
method for this event object. Otherwise, the event
is always sent to the EventHandler method of the
event object.

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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[Message index]

		event_pro for compound widgets By: Benjamin Hornberger on Tue, 07 September 2004 10:32
		Re: EVENT_PRO By: David Fanning on Mon, 29 November 2010 11:40
		Re: EVENT_PRO By: David Fanning on Mon, 29 November 2010 11:09
		Re: EVENT_PRO By: silje on Mon, 29 November 2010 11:02
		Re: EVENT_PRO By: David Fanning on Mon, 29 November 2010 11:02
		Re: EVENT_PRO By: Paul Van Delst[1] on Mon, 29 November 2010 10:43
		Re: EVENT_PRO By: David Fanning on Mon, 29 November 2010 10:38
		Re: EVENT_PRO By: silje on Mon, 29 November 2010 09:22
		Re: EVENT_PRO By: David Fanning on Mon, 29 November 2010 08:46

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