The user event is the most important communication technique. A user event is an event that you trigger with 4GL code (rather than an event triggered directly by a user action).

By using the SendUserEvent method in one frame script to trigger a user event in another frame, you can make one frame force the execution of some code in another frame. For example, you can provide code so that when the user updates a field in one frame, that frame sends a user event to another active frame. When the other frame receives this user event, it triggers corresponding updates to data being displayed in the frame's window.

Another common use for a user event is to allow a child frame to communicate with its parent frame. For example, when the parent frame requests its child frame to close, the child frame may need to send a message back to the parent indicating that it cannot close because changes are outstanding.

Each of these techniques is discussed in the following sections in more detail.