Add docs about new C++ serialization callbacks

Author: mafiesto4

manual/scripting/advanced/refactoring-renaming.md

@@ -79,3 +79,7 @@ void MyType::Deserialize(DeserializeStream& stream, ISerializeModifier* modifier
 }
 ```
 ***
+
+## Serialization callbacks
+
+Flax supports serialization callback methods that can be used to manipulate an object before and/or after its serialization and deserialization by the serializer. That can be used to perform more advanced data upgrading after version changes. See [C++](../cpp/serialization.md) and [C#](../serialization/index.md) documentation sections to learn more.

manual/scripting/cpp/serialization.md

@@ -18,6 +18,50 @@ private:
     API_FIELD(Attributes="Serialize") float PrivateVarSaved;
 ```
 
+## Serialization callbacks
+
+Flax supports serialization callback methods. A callback can be used to manipulate an object before and/or after its serialization and deserialization by the serializer.
+
+* `OnSerializing`
+* `OnSerialized`
+* `OnDeserializing`
+* `OnDeserialized`
+
+Example:
+
+```cpp
+#include "Engine/Serialization/ISerializeModifier.h"
+
+API_CLASS() class FLAXENGINE_API MyScript : public Script
+{
+    API_AUTO_SERIALIZATION();
+    DECLARE_SCENE_OBJECT(MyScript);
+
+public:
+    API_FUNCTION(Attributes="OnSerializing", Hidden)
+    void OnSerializing(const CallbackContext& context)
+    {
+    }
+
+    API_FUNCTION(Attributes="OnSerialized", Hidden)
+    void OnSerialized(const CallbackContext& context)
+    {
+    }
+
+    API_FUNCTION(Attributes="OnDeserializing", Hidden)
+    void OnDeserializing(const CallbackContext& context)
+    {
+        // 'context.Modifier->EngineBuild' holds engine version of saved data
+    }
+
+    API_FUNCTION(Attributes="OnDeserialized", Hidden)
+    void OnDeserialized(const CallbackContext& context)
+    {
+        // 'context.Modifier->EngineBuild' holds engine version of saved data
+    }
+};
+```
+
 ## Json
 
 Flax uses [RapidJSON](https://rapidjson.org) library to serialize data into *json* format.

manual/scripting/serialization/index.md

@@ -29,14 +29,14 @@ Here are listed various hints about Flax serialization:
 * Avoid recursive references for custom objects types. It's better to use loop-references for scene objects.
 * When performing code refactoring see [this tutorial](../advanced/refactoring-renaming.md) about supporting old data format loading
 
-## Serialization Callbacks
+## Serialization callbacks
 
 Flax supports serialization callback methods. A callback can be used to manipulate an object before and/or after its serialization and deserialization by the serializer.
 
-* OnSerializing
-* OnSerialized
-* OnDeserializing
-* OnDeserialized
+* `OnSerializing`
+* `OnSerialized`
+* `OnDeserializing`
+* `OnDeserialized`
 
 Example: