Extract AutoRegister logic to a helper class

src/buffer.hh

@@ -244,57 +244,28 @@ constexpr Buffer::Flags operator~(Buffer::Flags lhs)
     return (Buffer::Flags)(~(int)lhs);
 }
 
-class BufferChangeListener_AutoRegister : public BufferChangeListener
+struct BufferListenerRegisterFuncs
+{
+    static void insert(const Buffer& buffer, BufferChangeListener& listener)
+    {
+        buffer.change_listeners().insert(&listener);
+    }
+    static void remove(const Buffer& buffer, BufferChangeListener& listener)
+    {
+        buffer.change_listeners().erase(&listener);
+    }
+};
+
+class BufferChangeListener_AutoRegister
+    : public BufferChangeListener,
+      public AutoRegister<BufferChangeListener_AutoRegister,
+                          BufferListenerRegisterFuncs, const Buffer>
 {
 public:
     BufferChangeListener_AutoRegister(const Buffer& buffer)
-        : m_buffer(&buffer)
+        : AutoRegister(buffer) {}
-    {
-        m_buffer->change_listeners().insert(this);
-    }
 
-    BufferChangeListener_AutoRegister(const BufferChangeListener_AutoRegister& other)
+    const Buffer& buffer() const { return registry(); }
-        : m_buffer(other.m_buffer)
-    {
-        m_buffer->change_listeners().insert(this);
-    }
-
-    BufferChangeListener_AutoRegister(BufferChangeListener_AutoRegister&& other)
-        : m_buffer(other.m_buffer)
-    {
-        m_buffer->change_listeners().insert(this);
-    }
-
-    ~BufferChangeListener_AutoRegister()
-    {
-        m_buffer->change_listeners().erase(this);
-    }
-
-    BufferChangeListener_AutoRegister& operator=(const BufferChangeListener_AutoRegister& other)
-    {
-        if (m_buffer != other.m_buffer)
-        {
-            m_buffer->change_listeners().erase(this);
-            m_buffer = other.m_buffer;
-            m_buffer->change_listeners().insert(this);
-        }
-        return *this;
-    }
-
-    BufferChangeListener_AutoRegister& operator=(BufferChangeListener_AutoRegister&& other)
-    {
-        if (m_buffer != other.m_buffer)
-        {
-            m_buffer->change_listeners().erase(this);
-            m_buffer = other.m_buffer;
-            m_buffer->change_listeners().insert(this);
-        }
-        return *this;
-    }
-
-    const Buffer& buffer() const { return *m_buffer; }
-private:
-    const Buffer* m_buffer;
 };
 
 }

src/utils.hh

@@ -227,6 +227,63 @@ const T& clamp(const T& val, const T& min, const T& max)
     return (val < min ? min : (val > max ? max : val));
 }
 
+// *** AutoRegister: RAII handling of value semantics registering classes ***
+
+template<typename EffectiveType, typename RegisterFuncs, typename Registry>
+class AutoRegister
+{
+public:
+    AutoRegister(Registry& registry)
+        : m_registry(&registry)
+    {
+        RegisterFuncs::insert(*m_registry, effective_this());
+    }
+
+    AutoRegister(const AutoRegister& other)
+        : m_registry(other.m_registry)
+    {
+        RegisterFuncs::insert(*m_registry, effective_this());
+    }
+
+    AutoRegister(AutoRegister&& other)
+        : m_registry(other.m_registry)
+    {
+        RegisterFuncs::insert(*m_registry, effective_this());
+    }
+
+    ~AutoRegister()
+    {
+        RegisterFuncs::remove(*m_registry, effective_this());
+    }
+
+    AutoRegister& operator=(const AutoRegister& other)
+    {
+        if (m_registry != other.m_registry)
+        {
+            RegisterFuncs::remove(*m_registry, effective_this());
+            m_registry = other.m_registry;
+            RegisterFuncs::insert(*m_registry, effective_this());
+        }
+        return *this;
+    }
+
+    AutoRegister& operator=(AutoRegister&& other)
+    {
+        if (m_registry != other.m_registry)
+        {
+            RegisterFuncs::remove(*m_registry, effective_this());
+            m_registry = other.m_registry;
+            RegisterFuncs::insert(*m_registry, effective_this());
+        }
+        return *this;
+    }
+    Registry& registry() const { return *m_registry; }
+
+private:
+    EffectiveType& effective_this() { return static_cast<EffectiveType&>(*this); }
+    Registry* m_registry;
+};
+
 }
 
 #endif // utils_hh_INCLUDED