| Re: Interrupting widget applications [message #7912] |
Sun, 26 January 1997 00:00 |
davidf
Messages: 2866
Registered: September 1996
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Senior Member |
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Sam Haimov <haimov@uwyo.edu> quotes M. Hegde with respect to interrupting loops
in widget programs:
>> So far the most convenient method I have found out is to monitor the event
>> queue with WIDGET_EVENT( interrupt button ) wherever the interrupt is desired
>> and proceed accordingly.
He goes on to write:
> I have similar experience.
>
> My application uses widgets for a real-time radar display. It can show
several different
> images on one or two windows and includes various widget controled
features. The main
> reason I am using widget_event to handle widgets is the fact that my main
loop is controled
> by the radar data acquisition system (non-IDL program) and I want the
interrupts to be
> based on the DAQ behaviour rather than on time intervals by TIMER.
Here, in my opinion, is just about the *only* justification for using
WIDGET_EVENT to manage IDL events rather than XMANAGER. Sam is
exactly right. If the locus of control is in an external program, then
I think you want to use WIDGET_EVENT to get IDL widget events
and process them appropriately.
But suppose the locus of control was the IDL widget program.
How could you get the program to respond to real-time events
that were being monitored by an external program?
One possible solution would be to use TIMER events. I typically
set timers on widgets that don't ordinarily receive events.
Usually I use a sub-base, whose only other purpose is to
organize my widget layout. I attach an event handler
to that base to handle the timer event. It looks like this:
subbase = WIDGET_BASE(tlb, EVENT_PRO='Timer_Event', COLUMN=2)
When I am ready to check my external program, I want to get
into the TIMER_EVENT event handler, so I set the timer to
go off immediately, like this:
WIDGET_EVENT, subbase, TIMER=0.0
Now I am inside my TIMER_EVENT event handler. Here I can do
whatever it is I need to do. For example, I can check my external
program to see if any new data has come in from my instruments.
If it has, I can plot it.
When I am finished doing whatever it is I need to do, I am set
to exit my event handler. If I want to come back periodically
I need to set the next timer event before I exit. Suppose I wanted
to check for new data every 1.5 seconds, then I would probably
have code like this at the bottom of my TIMER_EVENT event
handler:
IF info.stop NE 1 THEN WIDGET_CONTROL, event.id, TIMER=1.5
The info.stop variable is a stop flag that is usually set by a
STOP or INTERRRUPT or CANCEL button of some sort. In 1.5
seconds, I get back into this event handler for the next
round of doing whatever it is I do. But meanwhile, I can be
processing whatever other events are being generated by
my widget program, in the order in which they are being
generated. This will include EXIT buttons, READ DATA
buttons, etc.
If you want to see a good example of a TIMER event in
action, look at the program XMOVIE on my web page.
This program shows you how to do an animation
correctly in a widget program. It is possible to
interrupt the animation because the STOP and START
buttons just cue up the TIMER events.
Hope this gives people some ideas.
David
-----------------------------------------------------------
David Fanning, Ph.D.
Fanning Software Consulting
2642 Bradbury Court, Fort Collins, CO 80521
Phone: 970-221-0438 Fax: 970-221-4762
E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com
-----------------------------------------------------------
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| Re: Interrupting widget applications [message #7922 is a reply to message #7912] |
Fri, 24 January 1997 00:00  |
haimov
Messages: 9
Registered: August 1996
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Junior Member |
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In article <5c8dlj$996@post.gsfc.nasa.gov>, hegde@news.gsfc.nasa.gov says...
>
> Thanks for your suggestion. Although it works for a simple for loop, this
> type of implementation goes out of hand for multiple loops or recursive
> operations. And if it is required to monitor within a time consuming loop,
> I have to find another way.
>
> My need is to have an interrupt button in the main application window and
> it interrupt anything going on in other windows ( display windows, printer
> gizmos etc., ).
>
> So far the most convenient method I have found out is to monitor the event
> queue with WIDGET_EVENT( interrupt button ) wherever the interrupt is desired
> and proceed accordingly. Any suggestion is appreciated.
>
> Thanks,
>
> -M. Hegde
> hegde@neptune.gsfc.nasa.gov
I have similar experience, although I have not put much efforts to come up with a good
algorithm based on using TIMER.
My application uses widgets for a real-time radar display. It can show several different
images on one or two windows and includes various widget controled features. The main
reason I am using widget_event to handle widgets is the fact that my main loop is controled
by the radar data acquisition system (non-IDL program) and I want the interrupts to be
based on the DAQ behaviour rather than on time intervals by TIMER.
I also have a complex situations, which include needs for cancelations.
I control all of them through a DESTROY/CANCEL button on my main widget.
If you would like to see my code send me an email. It is relatively big set of routines
(about 1200 lines, not including external routines). This is my first serious work with
widgets and I am sure I am far from being an expert. Nevertheless it works nicely.
I am curious to know if I should make any efforts to avoid using widget_event even if
TIMER is not the natural thing to do.
Cheers, Sam
Samuel Haimov, Ph.D.
Atmos. Sci. Dept.
University of Wyoming
tel: (307) 766-2726
email: haimov@uwyo.edu
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| Re: Interrupting widget applications [message #7940 is a reply to message #7922] |
Thu, 23 January 1997 00:00 |
hegde
Messages: 17
Registered: December 1995
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Junior Member |
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Thanks for your suggestion. Although it works for a simple for loop, this
type of implementation goes out of hand for multiple loops or recursive
operations. And if it is required to monitor within a time consuming loop,
I have to find another way.
My need is to have an interrupt button in the main application window and
it interrupt anything going on in other windows ( display windows, printer
gizmos etc., ).
So far the most convenient method I have found out is to monitor the event
queue with WIDGET_EVENT( interrupt button ) wherever the interrupt is desired
and proceed accordingly. Any suggestion is appreciated.
Thanks,
-M. Hegde
hegde@neptune.gsfc.nasa.gov
William Thompson (thompson@orpheus.nascom.nasa.gov) wrote:
: What you need to do is to break your application down into discrete events, and
: then use TIMER events to run the events in sequence. For example, if your
: program uses a FOR loop, then you could instead make each run through the loop
: a discrete event, and store the loop counter between events.
:
: For example, you might define your main base with a line like
:
: MAIN_BASE = WIDGET_BASE(TITLE='CDS FITS Generation Software', $
: /FRAME, /COLUMN, UVALUE='Timer')
:
: and then in the event handler you would have code that would read
:
: WIDGET_CONTROL, EV.ID, GET_UVALUE=VALUE
: IF VALUE EQ 'Timer' THEN BEGIN
: ... do one piece of the complete operation ...
:
: It's important to restart the timer after every timed event, to keep it going.
: What I like to do is to keep a parameter called RUNNING which can be either 0
: or 1. A start button generates an event which does some initial preparation
: (e.g. setting the loop counter to 0), and sets RUNNING=1. Then at the bottom
: of the event handler routine I put a line like
:
: IF RUNNING THEN WIDGET_CONTROL, MAIN_BASE, TIMER=0.1
:
: A stop button simply sets RUNNING=0.
:
: Bill
--
test
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| Re: Interrupting widget applications [message #7943 is a reply to message #7940] |
Thu, 23 January 1997 00:00 |
davidf
Messages: 2866
Registered: September 1996
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Senior Member |
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M Hegde <hegde@news.gsfc.nasa.gov> writes:
> What is the best way to interrupt a loop in widget applications?.
> According to my IDL knowledge, IDL doesn't support concurrency; so I can't
> have a button/widget to do that. Ctrl-C is not a smart way as it exits the
> application. Any suggestions?.
Here is the most important suggestion: Don't write loops in widget
event handlers! Instead, take advantage of the fact that a widget
program *is itself* a loop. I have several examples of what I
mean on my web page. Take a look at the programs XMOVIE and
ZIMAGE for two ways to take advantage of the widget program
as a loop.
Alright, so sometimes there just isn't any other way. What then?
Then, you have a button that can "cancel" the loop. I have a
"show progress" widget example that you can download from
my anonymous ftp site. The idea is that something that takes
a lot of time is going on. (In this example, a BIG calculation.)
I want to allow the user to see the progress of the calculation
and I want them to be able to cancel the calculation if they
don't want to wait.
Here is the relevant section of the code that is inside the big
calculation loop. The variable info.cancel is the ID of the
CANCEL CALCULATION button. Notice that I am using
WIDGET_EVENT to look for an event directly. This is about
the *only* time I manage events myself. The rest of the
time I use XMANAGER.
; Did the "Cancel Operation" button get clicked?
; Look for an event. Don't turn off the hourglass cursor!
progressEvent = Widget_Event(info.cancel, /NoWait)
; Is this a button event?
eventName = Tag_Names(progressEvent, /Structure_Name)
IF eventName EQ 'WIDGET_BUTTON' THEN BEGIN
; If it IS a button event, destroy the show progress widget and
; issue an informational message to the user to alert him or her.
Widget_Control, info.top, /Destroy
result = Widget_Message('Operation Canceled!!', /Information)
; Escape from the loop. Interrupt code would go here.
GoTo, outSideLoop
You can download the "show progress" example program via anonymous
ftp from ftp.frii.com. It is in the directory:
/pub/dfanning/outgoing/idl_training/showprog.pro
Compile the program and type "test" to see it work:
IDL> .Compile showprog
IDL> test
Let me know if you have questions.
Yours,
David
-----------------------------------------------------------
David Fanning, Ph.D.
Fanning Software Consulting
2642 Bradbury Court, Fort Collins, CO 80521
Phone: 970-221-0438 Fax: 970-221-4762
E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com
-----------------------------------------------------------
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| Re: Interrupting widget applications [message #7944 is a reply to message #7940] |
Thu, 23 January 1997 00:00 |
thompson
Messages: 584
Registered: August 1991
|
Senior Member |
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hegde@news.gsfc.nasa.gov (M Hegde) writes:
> Hi,
> What is the best way to interrupt a loop in widget applications?.
> According to my IDL knowledge, IDL doesn't support concurrency; so I can't
> have a button/widget to do that. Ctrl-C is not a smart way as it exits the
> application. Any suggestions?.
What you need to do is to break your application down into discrete events, and
then use TIMER events to run the events in sequence. For example, if your
program uses a FOR loop, then you could instead make each run through the loop
a discrete event, and store the loop counter between events.
For example, you might define your main base with a line like
MAIN_BASE = WIDGET_BASE(TITLE='CDS FITS Generation Software', $
/FRAME, /COLUMN, UVALUE='Timer')
and then in the event handler you would have code that would read
WIDGET_CONTROL, EV.ID, GET_UVALUE=VALUE
IF VALUE EQ 'Timer' THEN BEGIN
... do one piece of the complete operation ...
It's important to restart the timer after every timed event, to keep it going.
What I like to do is to keep a parameter called RUNNING which can be either 0
or 1. A start button generates an event which does some initial preparation
(e.g. setting the loop counter to 0), and sets RUNNING=1. Then at the bottom
of the event handler routine I put a line like
IF RUNNING THEN WIDGET_CONTROL, MAIN_BASE, TIMER=0.1
A stop button simply sets RUNNING=0.
Bill
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