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sec : U Re: widget_control from call_external
JD Smith wrote:
> David Fanning wrote:
> > firstname.lastname@example.org (email@example.com) writes:
> > > I have a c/c++ programme that is called from within a
> > > widget hierachy via call_external.
> > >
> > > As the computations made take fairly long, I want to update
> > > a status bar with a 'Percentage complete' from the C-routine,
> > > so the user doesn't get upset and thinks the programme died
> > > on him/her.
> > >
> > > How do I go about that???
> > Well, this will be difficult unless your can call your
> > C program in "chunks", or in some other way interrupt
> > it. It might be easier if you just know, in general,
> > how long it takes. Then you can set a "kitchen timer"
> > sort of progress indicator. As long as the cake is
> > baked by the time the timer goes off, no one seems
> > to care. :-)
> > You can see several ways to build such a progress
> > indicator here:
> > http://www.dfanning.com/tips/show_progress.html
> I would use alarm() to throw a SIGALRM every 1 second, say, then update
> a percent complete counter, based on some innate knowledge of the
> calculation. To get this to IDL under call_external is more difficult.
> You *could* then just print it to the terminal, ala:
> printf("\r%02d%% complete",percent_complete);
> Make sure to:
> setbuf(stdout,(char *)NULL);
> first, so the updates will appear.
> Of course, RSI would frown on this, but if it gets the job done...
> If you'd like to do it full blown way, with a snazzy graphical update
> slider, you might have to make a full DLM, and use IDL_Execute to force
> the progress update from the C side. That's a lot of work for a bit of
> eye candy. But everybody likes candy.
> Good luck,
How about using the Widget_Stub functionality to pass an event from the
routine to a widget?
Under OpenVMS (at least) in IDL_DIR:[External.widstub] there are simple
examples of how to create your own widget type in C, and how to send
to it from C.
Comments in the file Widget_ArrowB.pro say :-
"While this code is VMS-centric, the principles apply across
Just another example of VMS leading the way.
I can't find the above directory or the example files in my Windows IDL
however do a Find in the Online Help for Widget Stub and everything you
need is there.
I've used Widget Stub to animate aircraft positions on a draw widget as
the C code fires off an event.
If a C-dunderhead like me can manage that, anyone can... ;-)
Andrew D. Cool .->-.
Electromagnetics & Propagation Group `-<-'
Surveillance Systems Division Transmitted on
Defence Science & Technology Organisation 100% recycled
PO Box 1500, Salisbury electrons
South Australia 5108
Phone : 061 8 8259 5740 Fax : 061 8 8259 6673
Email : firstname.lastname@example.org
--------- * Never trust what a man with half a brain says *-----------