+ /* returns all or part of the history.
+ If depth==0 it returns just the top
+ node. If depth<0, it returns everything.
+ If depth>0, it returns state for that
+ many elements of the history, or
+ the full history, whichever is smaller.
+ */
+
+ XMLNode &get_state(int32_t depth = 0);
+ void save_state();
+
+ void set_depth (uint32_t);
+
+ PBD::Signal0<void> Changed;
+ PBD::Signal0<void> BeginUndoRedo;
+ PBD::Signal0<void> EndUndoRedo;
+