The Spark RichEditableText component supports undo/redo operations. By default, these operations are limited to one session, which means they are cleared when the component loses focus. Sometimes we want to preserve these operations so that they are available after the component loses and gets focus back. Internally, the component checks the property clearUndoOnFocusOut to decide whether the undo operations should be cleared or not when it loses focus. This property is defined in the mx_internal namespace and set to true by default. To preserve the undo operations, just set its value to false, so if for example the component instance to configure is called ret, the following code will do the trick:
import mx.core.mx_internal; ret.mx_internal::clearUndoOnFocusOut = false;
