To restrict operators to opening only one sequence file at a time in the LabVIEW Simple Operator Interface, customize the Operator Interface by adding two Application Manager callbacks. This approach follows the TestStand UI customization model, which uses callbacks and event handling to modify user interface behavior without changing the TestStand Engine.
The first customization replaces the default callback VI for the DisplaySequenceFile event. Start with the shipped callback VI and add code that calls Engine.GetCurrentUser. The returned User object can be used to evaluate the current user's privileges or group membership and determine whether the restriction should be applied.
If the restriction is enabled for the current user, obtain references to the Sequence File ComboBox, Open Sequence File button, and Close Sequence File button. When a sequence file is loaded, disable the Sequence File ComboBox and Open Sequence File button. This prevents the operator from opening additional sequence files while allowing the currently loaded file to remain accessible and available for execution or closure.
The following image shows the code added to the DisplaySequenceFile callback.
The second customization adds a callback for the SequenceFileClosing event. When a sequence file is closed, the callback again evaluates the current user's privileges or group membership. If the restriction applies, the callback re-enables the Sequence File ComboBox and Open Sequence File button, allowing the user to select and open another sequence file.
The following image shows the code added to the SequenceFileClosing callback.
With these modifications, operators are limited to a single open sequence file while preserving the standard functionality of the shipped LabVIEW Simple Operator Interface. Because the logic is based on user privileges or group membership, the restriction can be selectively applied to specific user groups while allowing administrators or developers to retain access to multiple open sequence files.