void notifyUndoStackChanged() {
		Swing.runLater(() -> {
			for (TransactionListener listener : transactionListeners) {
				listener.undoStackChanged(domainObj);
			}
		});
	}
Returns the undo stack depth (The number of items on the undo stack).

<p>
This method is for JUnits.

@return the undo stack depth
Ghidra/Framework/Project/src/main/java/ghidra/framework/data/DomainObjectTransactionManager.java