Layered Scene Data.

- `renderSettings` is used in `group` while viewing the layers as a whole
- `commonData` is the common data for the whole scene
- `layers` are the layers of the scene with type `AbstractLayer`  DO REMEMBER TO ADD YOUR LAYERS HERE!

Here is an example for it:

{ renderSettings = []
, commonData = cd
, layers =
    [ Main.layer (MainInitData { components = comps, fakeBricks = fakes, isBoss = isBoss }) envcd
    , TechTree.layer NullLayerMsg envcd
    , TextLayer.layer (TextInitData levelName) envcd
    , PauseLayer.layer NullLayerMsg envcd
    , Guide.layer NullLayerMsg envcd
    ]
}

This creates a layered scene.

• init creates the initial layered scene from env data and init msg.

• settingsFunc is a user provided function to modify renderSettings each time the scene updates. If you don't need settingsFunc, simply provide a func _ _ _ = settings

init type sugar for normal (not prototype) layered scenes Receives Environment and sceneMsg (which stores the initial data), and return a record of data, for example this:

   { renderSettings = []
    , commonData = cd
    , layers =
        [ Opening.layer NullLayerMsg envcd ]
    }

• Note: The most important part here is the initialization of scenecommondata. This is so important that it usually takes a separate function to do it.

settingsFunc type sugar This function takes the environment, userevent, the data of the scene and add visual effects to the scene.

init type sugar for scene prototypes This defines the initializing function for a scene prototype. It should be like this:

LayeredSceneProtoInit SceneCommonData UserData LayerTarget (LayerMsg SceneMsg) SceneMsg (InitData SceneMsg)

It receives environment, the initial data to initialize the prototype, and return a layeredSceneData.

init type sugar for levels. Normally it is used internally. No need to worry about it.

Compose LayeredSceneProtoInit with LayeredSceneLevelInit.