add Buffer::add_cursor()

src/core/Buffer.h

@@ -105,6 +105,12 @@ public:
         m_iterators.push_back(iterator);
         return iterator;
     }
+    std::shared_ptr<Iterator> add_cursor()
+    {
+        auto iterator = add_iterator();
+        m_cursors.push_back(iterator);
+        return iterator;
+    }
     auto get_string() { return m_gap_buffer->get_string(); }
     size_t size() const { return m_gap_buffer->size(); }
     uint8_t * address(size_t offset) const { return m_gap_buffer->address(offset); }
@@ -130,6 +136,7 @@ protected:
     uint8_t m_tabstop;
     bool m_insert_mode;
     std::list<std::shared_ptr<Iterator>> m_iterators;
+    std::list<std::shared_ptr<Iterator>> m_cursors;
     std::shared_ptr<Iterator> m_eof_iterator;
     std::string m_filename;
     std::shared_ptr<ChangeOperation> m_current_change_operation;