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Re: Common block conumdrum [message #8423 is a reply to message #8355]

Wed, 05 March 1997 00:00

Phil Williams
Messages: 78
Registered: April 1996

Member

John-David Smith wrote:
>
> Struan Gray wrote:
>
>> This works but has it's own problems. I often need to have the
>> state information when the widget is killed so that I can save
>> parameters and variables to disk or pass a response to another widget.
>> David's technique works well if you can be sure that the user will
>> only ever kill the widget with 'close'/'quit'/'cancel' buttons, but if
>> the widget can be killed another way (with the xmanager tool or via a
>> close box provided by the operating system's window manager) I find
>> that by the time my widget knows it is being killed only the top level
>> base remains and my state information is lost.
>
> XMANAGER's CLEANUP callback mechanism gives you control of your dying
> widget after almost all of it has been killed. This is problematic,
> since you often can't then get to your state info.
>
> A technique I often use to prevent this behaviour is the KILL_NOTIFY
> mechanism. Its use is strongly discouraged in various IDL references,
> but the thrust of the warning is "don't assign a kill_notify procedure

<snip>

Figured I'd add my 2 cents again. They way I handle this is to have a
handle that would have any "global" data. Then any additional "global"
data that I needs I simply make a child handle of that main handle. I
then share this handle with any of my widgets that need it. If a popup
then dies the "main" widget still knows where the handle is and is also
responsible for it's cleanup when it dies.

It is my understanding that with IDL 5.0 that we are going to be more
careful with issues such as these since you will be able to run widgets
and still have access to the command line.

Good luck,
Phil
--
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Phil Williams, Ph.D.
Research Instructor
Children's Hospital Medical Center "One man gathers what
Imaging Research Center another man spills..."
3333 Burnet Ave. -The Grateful Dead
Cincinnati, OH 45229
email: williams@irc.chmcc.org
URL: http://scuttle.chmcc.org/~williams/
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[Message index]

		Common block conumdrum By: williams on Mon, 03 March 1997 00:00
		Re: Common block conumdrum By: Phil Williams on Wed, 05 March 1997 00:00
		Re: Common block conumdrum By: J.D. Smith on Wed, 05 March 1997 00:00
		Re: Common block conumdrum By: Struan Gray on Wed, 05 March 1997 00:00
		Re: Common block conumdrum By: wonko on Tue, 04 March 1997 00:00
		Re: Common block conumdrum By: David Foster on Tue, 04 March 1997 00:00
		Re: Common block conumdrum By: Phil Williams on Tue, 04 March 1997 00:00
		Re: Common block conumdrum By: brian.jackel on Tue, 04 March 1997 00:00
		Re: Common block conumdrum By: david.eldon on Fri, 16 May 2014 14:07

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