goog.editor.plugins.UndoRedoManager.EventType Enumgoog.editor.plugins.UndoRedoManager.EventTypeEvent types for the events dispatched by undo-redo manager.
.BEFORE_REDOSignifies that the redo method of a state is about to be called. Events of this type will have a {@code state} property whose value is the state whose redo action is about to be performed. If the event is cancelled the action does not proceed, but the state will still transition between stacks.
.BEFORE_UNDOSignifies that the undo method of a state is about to be called. Events of this type will have a {@code state} property whose value is the state whose undo action is about to be performed. If the event is cancelled the action does not proceed, but the state will still transition between stacks.
.STATE_ADDEDSignifies that a state was just added to the undo stack. Events of this type will have a {@code state} property whose value is the state that was just added.
.STATE_CHANGESignifies that he undo or redo stack transitioned between 0 and 1 states, meaning that the ability to peform undo or redo operations has changed.