SequenceContext.StepIndex generates "Execution is not paused" error in LabView Simple UI

[CIM1]

I am trying out TestStand 4.0 with a LabView 8.5 UI based on a modified NI Simple GUI.

I tried a simple poll of SequenceContext.StepIndex using the appropriate Property Nodes in a 1 second while loop to asynchronously check the progress of the sequence execution - but this fails to get the SequenceContext Property with an error:

    -17500 Exception occured in
    TSUI.IExecutionViewMgr:
    Execution is not paused in
    UI Main.vi

The error suggests that if the program was paused I could access the test step index but this seems to be contradictory to the expected functionality as described in the TestStand Help:

"StepIndex Property
Returns the zero-based index of the currently executing step. The index indicates the position of the step in the step group identified by the StepGroup property. If execution is suspended between steps, this property returns -1"

I can however successfully extract other ExecutionView Manager properties during execution such as Execution.SecondsExecuting.

How can I get get SequenceContext.StepIndex (or something equivalent) to return the test step successfully during execution?

[CIM1]

Ah I just found a thread which says that callbacks must be used to update the property successfully so I guess that is the problem...

[Jimmy_Reumuth]

From that error message, it looks like you got an error accessing SequenceContext on ExecutionViewMgr, rather than accessing StepIndex on SequenceContext.

Is the callback you found the Trace event on ExecutionViewMgr? That should work as long as it's ok that this won't get called when tracing is disabled.

[CIM1]

Yes the error was while attempting to access SequenceContext on ExecutionViewMgr - I was puzzled because I had successfully accessed Execution.SecondsExecuting (for example) without using callbacks.

I haven't completely mastered the use of callbacks yet - having messed around with the LabView Simple UI and other tutorial examples it is still a challenge to work out what is required to extend that functionality to display some of the other arbitrary data.

I assume that it is a common requirement amongst GUI designers to want to display things like progress bars, current test information etc in a customised fashion to suit an end user but there seems to be a lack of examples displaying this sort of thing - most seem to concentrate on the standard TestStand Controls.