| Re: Idl pointers/widget events [message #12490] |
Thu, 13 August 1998 00:00 |
davidf
Messages: 2866
Registered: September 1996
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Senior Member |
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Damian Hamilton (dhamilton@ssrl.slac.stanford.edu) writes:
> I am having a pointer problem. I use a pointer to maintain information from a
> widget event handler (as per David Fanning). However, despite the fact that
> the "info" structure which contains the pointer is passed successfully into the
> container with "set_uvalue", the pointer itself becomes invalid. Is there some
> problem with IDL for VMS or am I just doing something wrong?
>
> ptr = ptr_new({thing:thing, junk:junk})
> info = {stuff:stuff, ptr:ptr}
> widget_control, tlb, set_uvalue=info, /no_copy
> xmanager, "config", tlb, /no_block
>
> ...
>
> (now, in my event_handler "config_event":)
>
> widget_control, event.top, get_uvalue=info, /no_copy
>
> (at this point, "info" is a completely valid structure, and I can examine
> "info.stuff" to my heart's content. However, an attempt to reference
> "(*info.ptr)" results in crashing my program and an invalid pointer message.)
This seems odd. Here is a little example program that works
perfectly for me. How about you?
pro config_event, event
widget_control, event.top, get_uvalue=info
Help, info.ptr, (*info.ptr).thing, (*info.ptr).junk
print, (*info.ptr).thing
print, (*info.ptr).junk
END
pro config
tlb=widget_base()
button = widget_button(tlb, value='do it', scr_xsize=100)
thing=findgen(10)
junk = bytarr(20)
stuff=5
ptr = ptr_new({thing:thing, junk:junk})
info = {stuff:stuff, ptr:ptr}
widget_control, tlb, set_uvalue=info, /no_copy, /realize
xmanager, "config", tlb, /no_block
END
> I have also noticed some inconsistency with this problem between regular IDL
> and IDL/DE, which seems impossible. However, sometimes my code works in the
> development environment, but not in the regular command line. ?
No. I am sure this is impossible, even if it DOES involve
computers. :-) Something else has to explain this. Perhaps
your paths are not identical. But let's work on the first
problem first. What version of IDL?
Print, !Version
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting
E-Mail: davidf@dfanning.com
Phone: 970-221-0438, Toll Free Book Orders: 1-888-461-0155
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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| Re: Idl pointers/widget events [message #12497 is a reply to message #12490] |
Thu, 13 August 1998 00:00  |
mirko_vukovic
Messages: 50
Registered: January 1998
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Member |
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In article <1998Aug13.100127@ssrl.slac.stanford.edu>,
dhamilton@ssrl.slac.stanford.edu wrote:
> I am having a pointer problem. I use a pointer to maintain information from a
> widget event handler (as per David Fanning). However, despite the fact that
> the "info" structure which contains the pointer is passed successfully into
the
> container with "set_uvalue", the pointer itself becomes invalid. Is there
some
> problem with IDL for VMS or am I just doing something wrong?
>
> ptr = ptr_new({thing:thing, junk:junk})
> info = {stuff:stuff, ptr:ptr}
> widget_control, tlb, set_uvalue=info, /no_copy
> xmanager, "config", tlb, /no_block
>
> ...
>
> (now, in my event_handler "config_event":)
>
> widget_control, event.top, get_uvalue=info, /no_copy
>
> (at this point, "info" is a completely valid structure, and I can examine
> "info.stuff" to my heart's content. However, an attempt to reference
> "(*info.ptr)" results in crashing my program and an invalid pointer message.)
>
> I have also noticed some inconsistency with this problem between regular IDL
> and IDL/DE, which seems impossible. However, sometimes my code works in the
> development environment, but not in the regular command line. ?
>
> Thanks for your time and help
> Damian Hamilton, SLAC
>
Is your syntax correct. I would think that *(info.ptr) is the correct way
for your setup.
BTW, without knowing the details of your application, I believe that
what you should do is put _everything_ into info, and make info a pointer,
i.e.
> info = ptr_new({stuff:stuff,thing:thing, junk:junk})
> widget_control, tlb, set_uvalue=info
Since you are copying only the pointer address, there is no need to
use the /no_copy. That was the main point of using pointers. They
eliminate the use of /no_copy in widget events, and thus, any changes
you make to info, you do not need to restore it to the widgets uvalue
at the end of the event routine.
mirko
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