Re: Nugget of the week: Dynamic event registration

Ton, I am a bit confused by this.  In your advanced example, two of the events are on a ref constant.  How can you have an event on a ref constant?  I thought that I understood what you were doing by registering a constant, you were turning off an event.  I am trying to write a VI that allows a user to click and drag a data point on a graph.  My intention is that on mouse up, the cursor is placed on a data point.  If the cursor is on the correct data point, the user then could click and drag (mouse move enable) the y axis value of the point.  Upon mouse up, the drag (mouse move) would be disabled again.


MouseEvents3.png:
http://forums.ni.com/attachments/ni/...useEvents3.png


MouseEvents1.png:
http://forums.ni.com/attachments/ni/...useEvents1.png


MouseEvents2.png:
http://forums.ni.com/attachments/ni/...useEvents2.png

Hi Jim,
As I understand Ton's example the re-registration of an event to a contant cancels the previous registration, effectivle shutting it off.
Ben

Hi Ben, that was my understanding of the gist of his posting, and that is what I am trying to do.  What I don't understand from his picture are the two events on a constant (see attached).  I also don't understand why mine is not working.


DynamicEvents.png:
http://forums.ni.com/attachments/ni/...amicEvents.png

<img src="http://forums.ni.com/attachments/ni/170/342541/1/DynamicEvents.png">
&nbsp;
The text shown in the header of the evnt structure comes from the code that executes out to the left. In that case, (I think) Ton was creating those events and registering them against the constant so that they would not be registered initially but only registered against the actual picture control when required.
Sorry can't look at your other pictures now, gotta run!
Ben

Hi, since you can't create event structures and event handlers during execution I use this technique (which is used by NI in their examples as well).You always need the event handler in the dynamic event parts (with the '&lt;'). To unregister you need to feed a constant, you basically register for a control that does not exist.If you feed nothing the event will not be unregistered (just like an empty input to an unnamed cluster bundler).In your code you do the handling in static events, these be unregistered, you could do this by external coding, but it's much nicer to handle it with dynamic events.Ton