The OnUpdate handler is called right before each frame is painted (i.e. between the processing of events and user actions, but before the UI elements are drawn onto the screen). It is invoked for every visible frame that declares an OnUpdate handler.
- arg1 - The time (in seconds) since the last OnUpdate dispatch (I'm not sure if this is based on when the last dispatch run started or ended, or if it's maintained per frame). Also note that it does NOT include time spent zoning, only actual time spent looking at the world.