[gnote] Make notebook manager available from NoteManagerBase

[Aurimas Černius <aurimasc src gnome org>]

commit d650980301600d70c71b4cf98b4d6bcdbe1c24f1
Author: Aurimas Černius <aurisc4 gmail com>
Date:   Sun Dec 22 22:22:02 2019 +0200

    Make notebook manager available from NoteManagerBase

 src/notemanager.hpp     | 4 ++--
 src/notemanagerbase.hpp | 7 +++++++
 2 files changed, 9 insertions(+), 2 deletions(-)
---
diff --git a/src/notemanager.hpp b/src/notemanager.hpp
index 324df326..6e7dce76 100644
--- a/src/notemanager.hpp
+++ b/src/notemanager.hpp
@@ -41,11 +41,11 @@ namespace gnote {
     typedef sigc::slot<void, const Note::Ptr &> NoteChangedSlot;
     
     NoteManager(IGnote & g);
-    ~NoteManager();
+    virtual ~NoteManager();
 
     void init(const Glib::ustring &);
 
-    notebooks::NotebookManager & notebook_manager()
+    virtual notebooks::NotebookManager & notebook_manager() override
       {
         return m_notebook_manager;
       }
diff --git a/src/notemanagerbase.hpp b/src/notemanagerbase.hpp
index 238ef186..334936b3 100644
--- a/src/notemanagerbase.hpp
+++ b/src/notemanagerbase.hpp
@@ -29,6 +29,12 @@
 
 namespace gnote {
 
+namespace notebooks {
+
+class NotebookManager;
+
+}
+
 class IGnote;
 class TrieController;
 
@@ -44,6 +50,7 @@ public:
   NoteManagerBase(IGnote & g);
   virtual ~NoteManagerBase();
 
+  virtual notebooks::NotebookManager & notebook_manager() = 0;
   size_t trie_max_length();
   TrieHit<NoteBase::WeakPtr>::ListPtr find_trie_matches(const Glib::ustring &);