Gets whether redo is possible
Gets whether undo is possible
Clears action history
Gets max undo history
Gets the action history
Index of the current action
Initialize actions system
Notify that the top action has changed
Pushes a new action to the stack
Steps forward in the action stack
Sets the action index Indexes start at 1, 0 is reserved for the INTIAL index
Sets max undo history length
Gets the "top" action
Steps back in the action stack