cocos2d file format

[ricardoquesada]

cocos2d needs its own file format.

Currently we have different file formats for different objects. eg:

• Particle System uses ParticleDesigner file format
• TMX map uses the .tmx file format
• BMFont uses the BM file format
• LabelAtlas uses its own file format

But what we need is a way to load (and save) a complete cocos2d scene. CocosBuilder reader lets you load a complete scene, but its current file format its highly coupled with CocosBuilder internals, and not necessarily improved for cocos2d. And it doesn't have a "saver".

What cocos2d needs is:

• a way marshal and unmarshal the scene
• the file format should be compact ( "compact" needs to be defined)
• the file format should be fast ("fast" needs to be defined)

marshaling and unmarshaling the scene means:

• objects of the scene graph
• actions / animations
• textures / spritesheets / spritesheet frames
• any other objects needed to build the scene

[ricardoquesada]

Use cases: 1) Save the state of a game... and load it 2) Load the scenes created by editors (CocosBuilder or CocoStudio). In order for this to happen, the editors will need to have a "converter" or "exporter" to the cocos2d native format... (or continue to use their own reader, but this new file format will be optimized for speed and compactness)

[chengstory]

Currently CocoStudio uses JSON(JavaScript Object Notation) file format to load (and save) a complete scene.

JSON is built on two structures: * A collection of name/value pairs. * A ordered list of values, this is realized as an array, vector, list or sequence.

CocoStudio uses GameObject attached to the scene component as a complete scene, For instance:

{ "classname" : "gameobject", "components":[ { "classname" : "scene" } ], "gameobjects":[ ... ] }

[sergey-shambir]

Saving the state of a game with any cocos2d-x class serialization have one major trouble: fragile save files compatibility. Any change in cocos2d-x can break saves of game fans.

I also think there are no need to bind cocos2d to one serialization format. JSON, XML, fast binary - all formats have own use-cases, and even serialization to CCDictionary can be helpful (e.g for further serialization to JSON or XML).

It is possible to generate serialization code automatically using clang libraries. There is brief example: https://github.com/sergey-shambir/cocos2d-x-extensions-cpp2011 . In this code, example input and produced output are placed in serialization-codegen/test_data. It takes C++ header input with data structs and generates both declaration (in another header) and implementation for getters, setters and methods to save/load to/from CCDictionary. It already iterates over structures in file and uses information about variable type and annotation attributes __attribute__((annotate("any text")))

And of course any utility based on clang can do something using base classes of given class, includes list or other source code properties.

[ricardoquesada]

thanks for the feeback @sergey-shambir

Serialization based on CCDictionary is an option: it is easy to implement, understand, and debug the ouput. But it is not a fast option. The use case that I want to solve is:

• You have a scene with 1.000 nodes, and it should load as fast as possible, in just a few milliseconds. When you switch from one scene no another, the user should not "wait".

In order to achieve that I think we should have:

• our own memory manager: allocing 1.000 nodes is too expensive... so we should have own memory manager
• initializing the nodes should be super fast. A binary format that is not property-oriented should do the trick.

[ricardoquesada]

More info here: https://github.com/cocos2d/cocos2d-js/issues/64#issuecomment-17892773