ImageRef implements Loader

engine/asset.go

@@ -20,7 +20,8 @@ var (
 
 	imageCache = make(map[string]*ebiten.Image)
 
-	// Ensure SceneRef does the same stuff as Scene.
+	// Ensure ref types satisfy interfaces.
+	_ Loader = &ImageRef{}
 	_ Scener = &SceneRef{}
 )
 
@@ -52,36 +53,43 @@ func (r *AnimRef) Anim() *Anim {
 
 // ImageRef loads images from the AssetFS into *ebiten.Image form.
 // It is your responsibility to import _ "image/..." for whatever
-// format the files are in.
+// format the files are in, and to load it (either return it as a
+// subcomponent from Scan so that Game will Load it, or call Load
+// yourself).
 type ImageRef struct {
 	Path string
 
 	image *ebiten.Image
 }
 
-// Image returns the image. If it hasn't been loaded yet, it loads.
+// Image returns the image, or nil if not loaded.
 // Multiple distinct ImageRefs can use the same path.
-// TODO: adopt Loader?
 func (r *ImageRef) Image() *ebiten.Image {
-	if r.image != nil {
 	return r.image
-	}
+}
+
+// Load loads the image. Load is required before Image returns.
+// Loading the same path multiple times uses a cache to return
+// the same image.
+func (r *ImageRef) Load() error {
+	// Fast path load from cache
 	r.image = imageCache[r.Path]
 	if r.image != nil {
-		return r.image
+		return nil
 	}
+	// Slow path
 	f, err := AssetFS.Open(r.Path)
 	if err != nil {
-		log.Fatalf("Couldn't open asset: %v", err)
+		return err
 	}
 	defer f.Close()
 	i, _, err := image.Decode(f)
 	if err != nil {
-		log.Fatalf("Couldn't decode asset: %v", err)
+		return err
 	}
 	r.image = ebiten.NewImageFromImage(i)
 	imageCache[r.Path] = r.image
-	return r.image
+	return nil
 }
 
 // SceneRef loads a gzipped, gob-encoded Scene from the asset FS.

engine/image.go

@@ -13,6 +13,7 @@ var (
 	_ Drawer         = &Image{}
 	_ DrawOrderer    = &Image{}
 	_ ParallaxScaler = &Image{}
+	_ Scanner        = &Image{}
 )
 
 func init() {
@@ -36,3 +37,6 @@ func (i *Image) Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions) {
 	opts.GeoM = geom
 	screen.DrawImage(i.Src.Image(), &opts)
 }
+
+// Scan returns a slice containing Src.
+func (i *Image) Scan() []interface{} { return []interface{}{&i.Src} }

engine/sprite.go

@@ -51,7 +51,12 @@ func (s *Sprite) Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions) {
 	screen.DrawImage(src.SubImage(image.Rectangle{sp, sp.Add(s.FrameSize)}).(*ebiten.Image), &opts)
 }
 
-func (s *Sprite) Scan() []interface{} { return []interface{}{&s.Actor} }
+func (s *Sprite) Scan() []interface{} {
+	return []interface{}{
+		&s.Actor,
+		&s.Src,
+	}
+}
 
 func (s *Sprite) SetAnim(a *Anim) {
 	if s.anim != a {

engine/tiles.go

@@ -13,6 +13,7 @@ var (
 	_ Collider    = &Tilemap{}
 	_ Drawer      = &Tilemap{}
 	_ DrawOrderer = &Tilemap{}
+	_ Scanner     = &Tilemap{}
 	_ Updater     = &Tilemap{}
 )
 
@@ -86,6 +87,9 @@ func (t *Tilemap) Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions) {
 	}
 }
 
+// Scan returns a slice containing Src.
+func (t *Tilemap) Scan() []interface{} { return []interface{}{&t.Src} }
+
 // Update calls Update on any tiles that are Updaters, e.g. AnimatedTile.
 func (t *Tilemap) Update() error {
 	if t.Disabled {