Table Of Contents

User Interface Events

Last Modified: February 27, 2020

User interface events are events that occur when a user performs a particular action on the panel.

Each time a user interface event occurs, the diagram executes the code you write for the event. Compared with polling the user interface in a loop for interactions, user interface events reduce the CPU requirements of your program, simplify the diagram code, and ensure that the diagram can respond to all user actions.

You can select from two categories of user interface events: notify and filter.

Event Type Description Example Use Case

Informs you that a user action occurred.

Configure an Event structure to execute in order to handle a Value Change event when the user changes the value of a control.

Use notify events only if you want to know the user performed a specific action.


Allows you to validate or change the event data before the software performs the default action associated with that event. You can also discard the event to prevent the change.

Configure an Event structure to discard a Key down? event, which prevents a user from clicking the mouse to select or change behavior on the panel.

Use filter events if you want to influence how the software handles certain user actions.


Filter event names include a question mark to help you distinguish them from notify events. The software generates an associated notify event after most filter events if no event case discarded the event. The notify event has the same name as the filter event but without the question mark.

Recently Viewed Topics