Eager load used sprites

internal/assetstore/map.go

@@ -62,6 +62,21 @@ func (a *AssetStore) Map(name string) (*Map, error) {
 	return m, nil
 }
 
+func (m *Map) LoadSprites() error {
+	// Eager load the sprites we use
+	for x := m.Rect.Min.X; x <= m.Rect.Max.X; x++ {
+		for y := m.Rect.Min.Y; y <= m.Rect.Max.Y; y++ {
+			for z := 0; z < maps.MaxHeight; z++ {
+				if _, err := m.SpritesForCell(x, y, z); err != nil {
+					return err
+				}
+			}
+		}
+	}
+
+	return nil
+}
+
 // SpritesForCell returns the sprites needed to correctly render this cell.
 // They should be rendered from first to last to get the correct ordering
 func (m *Map) SpritesForCell(x, y, z int) ([]*Sprite, error) {

internal/assetstore/object.go

@@ -1,6 +1,7 @@
 package assetstore
 
 import (
+	"fmt"
 	"log"
 
 	"github.com/hajimehoshi/ebiten"
@@ -18,6 +19,7 @@ type Object struct {
 type Sprite struct {
 	obj *Object
 
+	ID      string
 	XOffset int
 	YOffset int
 	Width   int
@@ -50,8 +52,8 @@ func (a *AssetStore) Object(name string) (*Object, error) {
 		sprites: make([]*Sprite, int(raw.NumSprites)),
 		raw:     raw,
 	}
-	a.objs[name] = obj
 
+	a.objs[name] = obj
 	return obj, nil
 }
 
@@ -75,6 +77,7 @@ func (o *Object) Sprite(idx int) (*Sprite, error) {
 	}
 
 	sprite := &Sprite{
+		ID:      fmt.Sprintf("%v:%v", o.raw.Name, idx),
 		obj:     o,
 		Width:   int(raw.Width),
 		Height:  int(raw.Width),