Virtual Scene Runner

note

This feature is provided in the messenger-core package.

Users may want to run multiple scenes simultaneously, or use stacked scenes (which can remember your previous scene automatically).

Messenger provides several functions to allow users to run scenes in user code, like running "virtual machines".

The API is very simple, in Messenger.Scene.VSR:

{-| Virtual Scene Runner
-}
type alias VSR userdata scenemsg =
    { env : Env () userdata
    , runtime : Runtime
    , scene : MAbstractScene userdata scenemsg
    }

{-| Update the VSR.
-}
updateVSR : VSR userdata scenemsg -> UserEvent -> ( VSR userdata scenemsg, List (SceneOutputMsg scenemsg userdata) )

{-| View the VSR.
-}
viewVSR : VSR userdata scenemsg -> Renderable

A VSR stores an Env, a Runtime (own timeline), and an abstract scene. updateVSR advances the virtual scene including its own time counters on Tick. viewVSR renders it.

But how to get the scene?

In global components, the common data GCCommonData is just MAbstractScene so we could get it easily.

For normal user code, if there is a scene defined as:

scene : SceneStorage UserData SceneMsg

Users could generate an abstract scene by initializing it with a message, runtime, and environment, since its type is:

type alias SceneStorage userdata scenemsg =
    Maybe scenemsg -> Runtime -> Env () userdata -> MAbstractScene userdata scenemsg