| Re: Widget event handlers [message #23985] |
Thu, 01 March 2001 21:19  |
davidf
Messages: 2866
Registered: September 1996
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Senior Member |
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Joe Means (means@fsl.orst.edu) writes:
> In a widget program [TranslateAxies] I am writing I specify an event
> handler function for each widget that can generate an event. I specify
> event handlers for each text and button widget but not for base and
> label widgets [no bases are resizeable]. No base widgets can be
> resized. The GUI includes text boxes for user input. When I ran the
> program initially, put text in any box and clicked enter, I always got
> the error:
> Attempt to call undefined procedure/function: 'TRANSLATEAXIES_EVENT'.
>
> So I put a do-nothing procedure with this name in the
> TranslateAxies_EventCB file. Now I do not get the error. Also, all the
> text widgets and their event functions seem to run fine [when I click
> return after entering a value in the text field], because their values
> in the info structure are updated OK.
>
> It does not seem like I need this do-nothing proceedure. Can anyone
> tell me why it is needed?
No, no one will be able to tell you why it is needed. :-)
It's not needed. Somehow events from this text widget
are not getting sent to the text widget's event handler.
Instead, they are "bubbling up" to the top-level base
event handler, which you have not written, but which would
be named 'TRANSLATEAXIES_EVENT'. In the absence of other
information (e.g., a different name assigned with the
EVENT_HANDLER keyword to XMANAGER) IDL uses the register
name ("translateaxies", in this case) and appends the _EVENT
to it, and assigns this to the top-level base.
I'd guess this was a programming error. (Maybe EVENT_PRO is
mis-spelled, or something like that.) But widgets that have
event handlers assigned to them, *always* send their events
to the proper event handlers. I've never known it to fail.
And, of course, I'm totally skeptical that the program
is actually "working". :-)
It is often the case in widget programs that we don't want
to deal with text widget events. In other words, most of
my programs are written in such a way that I totally
ignore text widget events until the user hits the
DOIT button, or whatever. If your program has that
kind of design, I can well believe it appears to
work, even when you are sending text events to a NULL
event handler. That's a design technique I use all the
time. But, in general, it's better to use this design
by choice, rather than by necessity.
> Also, when I type text in a text widget it will not call the event
> function to update the value in the info structure if I click tab to
> move out of the field. Why is this?
You probably have your text widget set up to only return
Carriage Return events (EDITABLE=1, ALL_EVENTS=0). A
carriage return is the character String(13B). A tab is
character String(9B). A character return is not a tab.
It's pretty much as simple as that.
Or, another reason this might fail, is that you
are running IDL on a Mac. There, I don't think it
is even possible to trap tabs if you have ALL_EVENTS=1,
since the MacOS has already decided it's going to do
something spiffy with TAB events. (On more mundane
machines, we have to *make* our TAB characters move
to the next input field. What a bother! But one of
the nice features of FSC_FIELD, by the way.)
Sounds like you have almost de-mystified this
widget programming stuff, Joe. :-)
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438 E-Mail: davidf@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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| Re: Widget event handlers [message #23986 is a reply to message #23985] |
Thu, 01 March 2001 20:36  |
marc schellens[1]
Messages: 183
Registered: January 2000
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Senior Member |
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Joe Means wrote:
>
> In a widget program [TranslateAxies] I am writing I specify an event
> handler function for each widget that can generate an event. I specify
> event handlers for each text and button widget but not for base and
> label widgets [no bases are resizeable]. No base widgets can be
> resized. The GUI includes text boxes for user input. When I ran the
> program initially, put text in any box and clicked enter, I always got
> the error:
> Attempt to call undefined procedure/function: 'TRANSLATEAXIES_EVENT'.
>
> So I put a do-nothing procedure with this name in the
> TranslateAxies_EventCB file. Now I do not get the error. Also, all the
> text widgets and their event functions seem to run fine [when I click
> return after entering a value in the text field], because their values
> in the info structure are updated OK.
>
> It does not seem like I need this do-nothing proceedure. Can anyone
> tell me why it is needed?
>
> Also, when I type text in a text widget it will not call the event
> function to update the value in the info structure if I click tab to
> move out of the field. Why is this?
You probably use EVENT_FUNC and return the event at the end, in wich
case the next
eventhandler in the eventhandler-tree is called (and so on, earlier or
later
'TRANSLATEAXIES_EVENT').
So use EVENT_PRO or don't return anything from
your EVENT_FUNC (even the latter is not best style, but works).
Regarding your second question, just set /ALL_EVENTS keyword in your
widget_text function. Then the eventhandler is called after every change
in the widget, keeping your info structure always up to date.
cheers,
marc
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| Re: Widget event handlers [message #24071 is a reply to message #23986] |
Fri, 02 March 2001 13:26 |
Joe Means
Messages: 44
Registered: November 1996
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Member |
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Thanks to Marc and David for your helpfull ideas. I was indeed
identifying the event handler with Event_func keyword, so using
Event_pro solved my first problem. I found the /Kbrd_focus_events
keyword met my needs better than /All_events. Now the info structure is
being updated but I do not need the TRANSLATEAXIES_EVENT procedure.
Joe Means
Marc Schellens wrote:
> Joe Means wrote:
>
>> In a widget program [TranslateAxies] I am writing I specify an event
>> handler function for each widget that can generate an event. I specify
>> event handlers for each text and button widget but not for base and
>> label widgets [no bases are resizeable]. No base widgets can be
>> resized. The GUI includes text boxes for user input. When I ran the
>> program initially, put text in any box and clicked enter, I always got
>> the error:
>> Attempt to call undefined procedure/function: 'TRANSLATEAXIES_EVENT'.
>>
>> So I put a do-nothing procedure with this name in the
>> TranslateAxies_EventCB file. Now I do not get the error. Also, all the
>> text widgets and their event functions seem to run fine [when I click
>> return after entering a value in the text field], because their values
>> in the info structure are updated OK.
>>
>> It does not seem like I need this do-nothing proceedure. Can anyone
>> tell me why it is needed?
>>
>> Also, when I type text in a text widget it will not call the event
>> function to update the value in the info structure if I click tab to
>> move out of the field. Why is this?
>
>
> You probably use EVENT_FUNC and return the event at the end, in wich
> case the next
> eventhandler in the eventhandler-tree is called (and so on, earlier or
> later
> 'TRANSLATEAXIES_EVENT').
> So use EVENT_PRO or don't return anything from
> your EVENT_FUNC (even the latter is not best style, but works).
>
> Regarding your second question, just set /ALL_EVENTS keyword in your
> widget_text function. Then the eventhandler is called after every change
> in the widget, keeping your info structure always up to date.
>
> cheers,
> marc
--
Joseph E. Means
Assistant Professor, joe.means@orst.edu
Department of Forest Science
Oregon State University
Corvallis, OR 97331-5752
541-750-7351
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