onRender property Null safety
Dispatched when the display list is about to be updated and rendered.
This event provides the last opportunity for objects listening for this event to make changes before the display list is rendered. You must call the Stage.invalidate method each time you want a render event to be dispatched. This event is a broadcast event, which means that it is dispatched by all display objects with a listener registered for this event.
EventStream<RenderEvent> get onRender => DisplayObject.renderEvent.forTarget(this);