Added rotary interface

src/menudisplay.h

@@ -42,7 +42,6 @@ public:
 
     int selectedIndex() const { return m_selectedIndex; }
 
-
     std::size_t menuItemCount() const { return m_menuItems.size(); }
 
     MenuItem& getMenuItem(std::size_t index)
@@ -96,6 +95,11 @@ public:
         return ptr;
     }
 
+    void rotate(int offset)
+    {
+        m_rotateOffset += offset;
+    }
+
 protected:
     void setSelectedIndex(int selectedIndex) { m_selectedIndex = selectedIndex; }