Prepare returns error

engine/actor.go

@@ -85,8 +85,9 @@ func (a *Actor) MoveY(dy float64, onCollide func()) {
 	}
 }
 
-func (a *Actor) Prepare(g *Game) {
+func (a *Actor) Prepare(g *Game) error {
 	a.collisionDomain = g.Component(a.CollisionDomain)
+	return nil
 }
 
 func sign(m int) int {

engine/camera.go

@@ -111,4 +111,7 @@ func (c *Camera) Update() error { return c.Scene.Update() }
 func (c *Camera) Scan() []interface{} { return []interface{}{c.Scene} }
 
 // Prepare grabs a copy of game (needed for screen dimensions)
-func (c *Camera) Prepare(game *Game) { c.game = game }
+func (c *Camera) Prepare(game *Game) error {
+	c.game = game
+	return nil
+}

engine/game.go

@@ -104,7 +104,7 @@ func walk(c interface{}, p []interface{}, v func(interface{}, []interface{}) err
 // fastidiously calling RegisterComponent/UnregisterComponent).
 func (g *Game) LoadAndPrepare(assets fs.FS) error {
 	// Load all the Loaders
-	if err := Walk(g.Root, func(c interface{}, _ []interface{}) error {
+	if err := Walk(g, func(c interface{}, _ []interface{}) error {
 		l, ok := c.(Loader)
 		if !ok {
 			return nil
@@ -117,17 +117,17 @@ func (g *Game) LoadAndPrepare(assets fs.FS) error {
 	// Build the component databases
 	g.dbmu.Lock()
 	g.db = make(map[string]Identifier)
-	if err := Walk(g.Root, g.registerComponent); err != nil {
+	if err := Walk(g, g.registerComponent); err != nil {
 		return err
 	}
 	g.dbmu.Unlock()
 
 	// Prepare all the Preppers
-	Walk(g.Root, func(c interface{}, _ []interface{}) error {
+	return Walk(g, func(c interface{}, _ []interface{}) error {
-		if p, ok := c.(Prepper); ok {
+		p, ok := c.(Prepper)
-			p.Prepare(g)
+		if !ok {
+			return nil
 		}
-		return nil
+		return p.Prepare(g)
 	})
-	return nil
 }

engine/interface.go

@@ -80,7 +80,7 @@ type ParallaxScaler interface {
 // database has been populated but before the game is run. The component can
 // store the reference to game, if needed, and also query the component database.
 type Prepper interface {
-	Prepare(game *Game)
+	Prepare(game *Game) error
 }
 
 // Scanner components can be scanned. It is called when the game tree is walked

engine/scene.go

@@ -39,7 +39,10 @@ func (s *Scene) Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions) {
 }
 
 // Prepare does an initial Z-order sort.
-func (s *Scene) Prepare(game *Game) { s.sortByDrawOrder() }
+func (s *Scene) Prepare(game *Game) error {
+	s.sortByDrawOrder()
+	return nil
+}
 
 // sortByDrawOrder sorts the components by Z position.
 // Everything without a Z sorts first. Stable sort is used to avoid Z-fighting

engine/sceneref.go

@@ -83,7 +83,7 @@ func (r SceneRef) Show() { r.scene.Show() }
 func (r SceneRef) Ident() string { return r.scene.Ident() }
 
 // Prepare prepares the scene.
-func (r SceneRef) Prepare(g *Game) { r.scene.Prepare(g) }
+func (r SceneRef) Prepare(g *Game) error { return r.scene.Prepare(g) }
 
 // Scan returns the components in the scene.
 func (r SceneRef) Scan() []interface{} { return r.scene.Scan() }

engine/sheet.go

@@ -21,9 +21,10 @@ type Sheet struct {
 	w int // width as measured in number of cells
 }
 
-func (s *Sheet) Prepare(*Game) {
+func (s *Sheet) Prepare(*Game) error {
 	s.w, _ = s.Src.Image().Size()
 	s.w /= s.CellSize.X
+	return nil
 }
 
 func (s *Sheet) Scan() []interface{} { return []interface{}{&s.Src} }

engine/walls.go

@@ -92,9 +92,10 @@ func (u *WallUnit) Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions) {
 	screen.DrawImage(src, &opts)
 }
 
-func (u *WallUnit) Prepare(g *Game) {
+func (u *WallUnit) Prepare(g *Game) error {
 	u.wall = g.Component(u.WallID).(*Wall)
 	u.wall.regUnit(u)
+	return nil
 }
 
 func (u *WallUnit) Update() error {

game/aw.go

@@ -188,7 +188,7 @@ func (aw *Awakeman) realUpdate() error {
 	return nil
 }
 
-func (aw *Awakeman) Prepare(game *engine.Game) {
+func (aw *Awakeman) Prepare(game *engine.Game) error {
 	aw.camera = game.Component(aw.CameraID).(*engine.Camera)
 	aw.toast, _ = game.Component(aw.ToastID).(*engine.DebugToast)
 
@@ -222,6 +222,7 @@ func (aw *Awakeman) Prepare(game *engine.Game) {
 		{Frame: 8, Duration: 6},
 		{Frame: 9, Duration: 6},
 	}}
+	return nil
 }
 
 func (aw *Awakeman) Scan() []interface{} { return []interface{}{&aw.Sprite} }