When you want a frame to receive a particular event from an external program, you must register the frame with OpenROAD for that particular event. Registering a frame tells OpenROAD to notify the frame whenever an external program sends the specified event. For example, if frame A is registered to receive the external _update event, whenever OpenROAD receives the external_update event from the external program, it notifies frame A that the event has occurred. OpenROAD then adds the external_update event to the event queue. (If the specified frame is not running at the time, OpenROAD simply ignores the event. This does not cause an error.)

You can register one frame for any number of external events. You can also register more than one frame for the same external event.

To register the frame to receive the external event, use the FrameExec RegisterUserEvent Method (see RegisterUserEvent Method). To remove an event from the list of registered events for the frame, use the FrameExec UnRegisterUserEvent Method (see UnRegisterUserEvent Method).