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Why Is "Lock Panel Until Handler Completes" Grayed Out For Certain Cases In An Event Structure?

Primary Software:
Primary Software Version: 2009 SP1
Primary Software Fixed Version: N/A
Secondary Software: N/A

When I right-click on the event structure's border, the "Lock Panel Until Handler Completes" option is grayed out for certain cases. Why is this?

In LabVIEW 6.x, removing the checkmark from Lock Panel Until Handler Completes allows front panel manipulation while a given case of an event structure is executing. Right-click on the menu for a given case in an event structure and click Lock Panel Until Handler Completes to locate this option. However, certain events always have this featured grayed out because they are using a type of event called filter events.


Filter events include Key Down, Key Repeat, Mouse Down, Menu Selection (App), and Panel Closing. They lock the front panel until the event has finished processing. Thus, user input is locked until the event completes (specifically, Lock Panel Until Handler Completes is grayed out). One possible workaround for such filter events is to include a subVI in the filter event case. Configure the properties of this subVI to have its front panel appear when called. You can then use the subVI’s front panel to control and monitor user inputs.

The other type of event is a notify event. Notify events trigger immediately when called, thus they allow front panel manipulation if you uncheck Lock Panel Until Handler Completes. Such events include Key Up and Mouse Up.

Note: The Lock Panel Until Handler Completes option does not appear in LabVIEW 7.0 or later. In LabVIEW 6.x, refer to the LabVIEW User Manual (linked below) for more information about this option.

Related Links:
KnowledgeBase 2LRE8H2G: Why Does My User Interface Lock-Up when Using Event Structures? 
White Paper: Event-Driven Programming in LabVIEW
LabVIEW User Manual - November 2001


Report Date: 01/31/2003
Last Updated: 12/19/2016
Document ID: 2TUCG6HM

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