core/undo: provide access to the QUndoStack

This is used by the mobile UI to get notifications when the undo
text changes.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

commands/command_base.cpp

@@ -29,6 +29,12 @@ bool isClean()
 	return undoStack.isClean();
 }
 
+// this can be used to get access to the signals emitted by the QUndoStack
+QUndoStack *getUndoStack()
+{
+	return &undoStack;
+}
+
 QAction *undoAction(QObject *parent)
 {
 	return undoStack.createUndoAction(parent, QCoreApplication::translate("Command", "&Undo"));

commands/command_base.h

@@ -172,6 +172,8 @@ public:
 // If nothing is to be done, the command will be deleted and false is returned.
 bool execute(Base *cmd);
 
+QUndoStack *getUndoStack();
+
 } // namespace Command
 
 #endif // COMMAND_BASE_H