The Implementation

How FRAG does it

FRAG’s game loop is pretty standard and can be broken down into several sections.

Initialization

Let’s get things started…

The initialization phase of the game loop begins when the startFrag procedure is called.

  proc startFrag*T =
    var ctx = Frag()
    ctx.init(config, app)
    app.initApp(ctx)
          

  proc initApp(app: App, ctx: Frag) =
    # Application initialization logic goes here!
    discard


startFrag(App(), Config(
    rootWindowTitle: “Frag Example 00-hello-world”,
    rootWindowPosX: window.posUndefined, rootWindowPosY: window.posUndefined,
    rootWindowWidth: 960, rootWindowHeight: 540,
    resetFlags: ResetFlag.VSync,
    logFileName: “example-00.log”,
    assetRoot: “../assets”,
    debugMode: BGFX_DEBUG_TEXT
  ))
          

During this phase of the game loop, the framework itself along with all of its subsystems will be initialized. The initApp procedure of the app object provided to the startFrag procedure, will also be invoked - allowing the FRAG application to execute whatever initialization logic it needs to.

Update

Your game logic goes here!

Once the framework, subsystems, and application have all finished carrying out their initialization logic, the game loop actually begins.

During every iteration of the game loop, the updateApp procedure will be called. This provides the application with a hook where it can implement whatever update logic it needs to.

  proc updateApp(app:App, ctx: Frag, deltaTime: float) =
    # Update application state here!
    discard
          

Render

Ready. Set. Draw.

Along with the updateApp procedure, the renderApp procedure will be called each frame. Similar to how application state updates should be performed during the updateApp invocation, any drawing that is to be done should be performed during this call.

  proc renderApp(app: App, ctx: Frag, deltaTime: float) =
    # Clear Color & Depth Buffers
    ctx.graphics.clearView(0, ClearMode.Color.ord or ClearMode.Depth.ord, 0x303030ff, 1.0, 0)
    # Perform application rendering here!
          

Shutdown

Don’t forget to clean up after yourself!

The final phase of the game loop is the shutdown phase. This phase is entered when the framework calls the shutdownApp procedure.

For this phase to be entered, the conditional check which was enforcing the actual loop of the game loop, must fail. This is generally caused by the end-user of the application closing it, or the application unexpectedly terminating.

During the invocation of the shutdownApp procedure, resources which are not automatically released by the framework, or garbage-collected, should be freed.

  proc shutdownApp(app: App, ctx: Frag) =
    # Free resources here!
    discard