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Global Data and Getters

GlobalData is the user-owned state Messenger carries across scenes. Engine-owned runtime state is kept separately in a read-only Runtime value that user code receives beside Env.

type alias GlobalData userdata =
    { extraHTML : Maybe (Html WorldEvent)
    , canvasAttributes : List (Html.Attribute WorldEvent)
    , userData : userdata
    , camera : Camera
    }

Writable Fields​

  • userData: user-owned data, usually the data you save to local storage.
  • extraHTML: optional extra HTML rendered together with the canvas.
  • canvasAttributes: custom attributes attached to the canvas.
  • camera: the global camera used for rendering the scene.

Runtime is opaque and read-only. User code can pass the runtime value to approved helpers, such as texture, coordinate, and audio helpers, but cannot inspect or replace its fields. User update functions return only Env, not Runtime.

Initial Global Data​

MainConfig.initGlobalData returns GlobalDataInit, not a full GlobalData.

type alias GlobalDataInit userdata =
    { camera : Camera
    , volume : Float
    , extraHTML : Maybe (Html WorldEvent)
    , canvasAttributes : List (Html.Attribute WorldEvent)
    , userData : userdata
    }

Messenger initializes runtime fields such as time, current scene, pressed keys, mouse position, loaded resources, and audio state.

Getter Groups​

Import getters from Messenger.Base.

import Messenger.Base exposing (getSceneStartTime, getMousePos, getPressedKeys)

Time and scene:

  • getSceneStartTime : Runtime -> Float
  • getGlobalStartTime : Runtime -> Float
  • getGlobalStartFrame : Runtime -> Int
  • getSceneStartFrame : Runtime -> Int
  • getCurrentTimeStamp : Runtime -> Float
  • getCurrentScene : Runtime -> String

Input and browser state:

  • getWindowVisibility : Runtime -> Visibility
  • getMousePos : Runtime -> ( Float, Float )
  • getPressedMouseButtons : Runtime -> Set Int
  • getPressedKeys : Runtime -> Set Int

Canvas, volume, and resources:

  • getVolume : Runtime -> Float
  • getVirtualSize : Runtime -> ( Float, Float )
  • getRealSize : Runtime -> ( Float, Float )
  • getViewPort : Runtime -> ( Float, Float )
  • getCanvasOffset : Runtime -> ( Float, Float )
  • getLoadingProgress : Runtime -> ( Int, Int )
  • getFonts : Runtime -> Set String
  • getPrograms : Runtime -> Set String
  • getSprite : String -> Runtime -> Maybe REGL.Texture
  • getAllSprites : Runtime -> Dict String REGL.Texture
  • getConfigData : String -> Runtime -> Maybe String

Saving Global Data​

saveGlobalData is used for local storage (see LocalStorage). It receives the read-only Runtime and the writable GlobalData.

saveGlobalData : Runtime -> GlobalData UserData -> String
saveGlobalData runtime globalData =
    encodeUserData globalData.userData

If you need engine-owned values while saving, read them from runtime with getters.