Sub-panel Events

[ASTDan]

Hello,

I found this in the LabVIEW help on-line

http://zone.ni.com/reference/en-XX/help/371361J-01/lvhowto/using_events_and_subpanels/

If you configure a VI to handle an event and then configure the VI you load into a subpanel control to handle the same event, the top-level VI containing the subpanel control handles the event.

Does anyone have an example of this?

This may be cool...

Thanks

Dan

[mikeporter]

I'm not sure what the context for this statement might be, but as far as I know every VI that is registered to receive an event will catch it at the same time.

Mike...

[ASTDan]

How can 2 vi's register for the same event?

Thanks

[mikeporter]

It's easy. With a UDE you can have dozens of VIs respond to the event. In fact that's typically how I stop an application.

For a control reference it takes a bit more work. Pass a reference to a control on one VI to another VI. In the second VI you can use that reference to register an event on it. I will often do that if I have a subpanel VI that I want to respond to clicks of buttons on the main GUI.

Now I have never actually tried having two VIs respond to the same control event, so that may be what the old help file is talking about, but note that it is talking about a version 3 major revs ago. Another potential complication is that when you create a control event in the normal way LabVIEW by default locks out the front panel until the event is handled, that might cause an issue also. Someday when I have time I'll have to try it out for grins and giggles.

For examples of both use cases, check out my blog. Link is in my signature.

Mike...

[Intaris]

I have never found this statement to be true.  It would be a programming nightmare.

There may be a small subset of events which are handled by the parent VI but the VAST majority work as advertised.

I personally treat this statement as false.

[Bob_Schor]

Intaris, forgive me, but which statement do you regard as false?

Bob Schor

[Intaris]

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@Bob_Schor wrote:

Intaris, forgive me, but which statement do you regard as false?

---

Sorry, I was rather indiscriminate in my statement.

I'm referring to this one:

If you configure a VI to handle an event and then configure the VI you load into a subpanel control to handle the same event, the top-level VI containing the subpanel control handles the event.

I have often been curious about this statement and have never really found data to back it up.

[stevem181]

ASTDan,

I was curious, so attached is an example in LabVIEW 2012.

The Count 1 and 2 indicators receive User Event data from the respective subvis.

-Click on the Fire Gen Event button to send event to the main and subvis with the Generate User Event node

-Mouse up on the Fire MU Event button to send mouse event to both vis

-Click on the subvi OK button to send Mouse Up to both vis

I'm not sure what the Help message is referring to.

steve

[MarcDub]

My experience has been the same. No issue to have multiple Event structures configured for the same event. What I have been unofficially told from someone at NI is that all the warnings about using multiple Event Structures are due to the possible use of Filter events. If one of the structure is configured to filter events, you might get unpredictable behavior: some structures getting the events, and some don't.