| Re: exchanging parameters with a modal dialog [message #26443] |
Fri, 24 August 2001 16:29 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Rick Baer (rick_baer@agilent.com) writes:
> What is the most elegant way to exchange data with a modal dialog box? I
> would like to change some parameters that exist within the scope of the main
> program. These parameters are currently part of the info structure of the
> main program, so they are like member variables of the "App" class (in MFC
> parlance). I could include the ID of the top-level base of the main program
> in the user data of the modal dialog, and then use widget_control to access
> the uvalue and modify the parameters. This would be like passing the
> "theApp" pointer and dereferencing it. Alternatively, I could just place the
> parameters in a common block. It would be much simpler, but I could only run
> one invocation of the program at a time. Any recommendations?
If this is truly a "modal" dialog, chances are
you are going to pass the top-level base identifier
to the program anyway as the Group Leader of the modal
dialog. So, accessing the TLB's info structure will work
fine.
Except... Here is a case where you really wish that
TLB user value was a pointer to the info structure
rather than the structure itself. Everything would
be much easier that way. As a structure, you are going
to be tempted to make another copy of it for the
dialog's use.
But don't worry, keep passing the thing around with
those NO_COPY keywords, and it acts like a pointer
anyway. Just be sure you stuff it back in the
original location (I.e., the user value of the
Group Leader) before you issue the command that
destroys the modal dialog. And since "commands"
rarely kill widget programs (mice wielding users
do), this might very well require some creative
use of a Kill_Notify or TLB_Kill_Request_Events
keyword.
Another way to do this, and one I would probably
use if it were me, is to write the modal dialog
as a function. If done properly, you could then
call it like this:
Widget_Control, event.top, Get_UValue=info, /No_Copy
modifiedinfo = MyDialog(info, Group_Leader=event.top)
Widget_Control, event.top, Set_UValue=modifiedinfo , /No_Copy
It could take the current info structure in, and
pass a modified info structure back. You will have
to take some care about what happens if the user
kills the dialog before anything happens, but these
are the usual details.
Cheers,
David
P.S. You are absolutely correct to *always* avoid
common blocks in widget programs. They always lead
to problems. :-)
--
David W. Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438, E-mail: david@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155
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