AnimRef

engine/asset.go

@@ -1,6 +1,7 @@
 package engine
 
 import (
+	"encoding/gob"
 	"fmt"
 	"image"
 	"io/fs"
@@ -11,20 +12,38 @@ import (
 var (
 	AssetFS fs.FS
 
+	animDefCache = make(map[string]*AnimDef)
 	imageCache   = make(map[string]*ebiten.Image)
 )
 
+// AnimRef
 type AnimRef struct {
 	Path string
 
-	animdef *AnimDef
+	anim *Anim
 }
 
-func (r *AnimRef) Anim() *Anim {
+func (r *AnimRef) Anim() (*Anim, error) {
-	// TODO
+	if r.anim != nil {
-	return &Anim{
+		return r.anim, nil
-		Def: r.animdef,
 	}
+	if ad := animDefCache[r.Path]; ad != nil {
+		r.anim = &Anim{Def: ad}
+		return r.anim, nil
+	}
+	f, err := AssetFS.Open(r.Path)
+	if err != nil {
+		return nil, fmt.Errorf("open asset: %w", err)
+	}
+	defer f.Close()
+	dec := gob.NewDecoder(f)
+	ad := &AnimDef{}
+	if err := dec.Decode(ad); err != nil {
+		return nil, fmt.Errorf("decode asset: %w", err)
+	}
+	animDefCache[r.Path] = ad
+	r.anim = &Anim{Def: ad}
+	return r.anim, nil
 }
 
 // ImageRef loads images from the AssetFS into *ebiten.Image form.

engine/tiles.go

@@ -14,6 +14,7 @@ func init() {
 	gob.Register(Tilemap{})
 }
 
+// Tilemap renders a grid of tiles.
 type Tilemap struct {
 	Map       [][]Tile
 	Src       ImageRef // must be a horizontal tile set
@@ -22,6 +23,7 @@ type Tilemap struct {
 	ZPos
 }
 
+// Draw draws the tilemap.
 func (t *Tilemap) Draw(screen *ebiten.Image, geom ebiten.GeoM) {
 	geom.Concat(t.Transform)
 	for j, row := range t.Map {
@@ -33,7 +35,7 @@ func (t *Tilemap) Draw(screen *ebiten.Image, geom ebiten.GeoM) {
 			sx := tile.TileIndex() * t.TileSize
 			im, err := t.Src.Image()
 			if err != nil {
-				log.Fatalf("Loading image from reference: %v", err)
+				log.Fatalf("Tilemap.Draw loading image: %v", err)
 			}
 			src := im.SubImage(image.Rect(sx, 0, sx+t.TileSize, t.TileSize)).(*ebiten.Image)
 			screen.DrawImage(src, &op)
@@ -41,6 +43,7 @@ func (t *Tilemap) Draw(screen *ebiten.Image, geom ebiten.GeoM) {
 	}
 }
 
+// Update calls Update on any tiles that are Updaters, e.g. AnimatedTile.
 func (t *Tilemap) Update() error {
 	for j := range t.Map {
 		for i := range t.Map[j] {
@@ -54,14 +57,17 @@ func (t *Tilemap) Update() error {
 	return nil
 }
 
+// Tile is the interface needed by Tilemap.
 type Tile interface {
 	TileIndex() int
 }
 
+// StaticTile returns a fixed tile index.
 type StaticTile int
 
 func (s StaticTile) TileIndex() int { return int(s) }
 
+// AnimatedTile uses an Anim to choose a tile index.
 type AnimatedTile struct {
 	Anim
 }

engine/z.go

@@ -1,5 +1,7 @@
 package engine
 
+// ZPos implements ZPositioner directly (as a float64 value).
 type ZPos float64
 
+// Z returns z as a float64.
 func (z ZPos) Z() float64 { return float64(z) }