Respect sprite X and Y offsets

This makes menus display more correctly, and also fixes trees and other
objects on the main map, although it messes up bounds clipping (sigh).

internal/assetstore/object.go

@@ -9,12 +9,23 @@ import (
 )
 
 type Object struct {
-	assets *AssetStore
-	images []*ebiten.Image
+	assets  *AssetStore
+	sprites []*Sprite
 
 	raw *data.Object
 }
 
+type Sprite struct {
+	obj *Object
+
+	XOffset int
+	YOffset int
+	Width   int
+	Height  int
+
+	Image *ebiten.Image
+}
+
 func (a *AssetStore) Object(name string) (*Object, error) {
 	name = canonical(name)
 
@@ -35,9 +46,9 @@ func (a *AssetStore) Object(name string) (*Object, error) {
 	raw.Name = name
 
 	obj := &Object{
-		assets: a,
-		images: make([]*ebiten.Image, int(raw.NumSprites)),
-		raw:    raw,
+		assets:  a,
+		sprites: make([]*Sprite, int(raw.NumSprites)),
+		raw:     raw,
 	}
 	a.objs[name] = obj
 
@@ -45,11 +56,11 @@ func (a *AssetStore) Object(name string) (*Object, error) {
 }
 
 // Filled lazily
-func (o *Object) Image(idx int) (*ebiten.Image, error) {
-	if img := o.images[idx]; img != nil {
-		return img, nil
+func (o *Object) Sprite(idx int) (*Sprite, error) {
+	if sprite := o.sprites[idx]; sprite != nil {
+		return sprite, nil
 	}
-	log.Printf("Loading sprite %v %v", o.raw.Name, idx)
+	log.Printf("Loading sprite %v:%v", o.raw.Name, idx)
 
 	if o.raw.Sprites[idx] == nil {
 		if err := o.raw.LoadSprite(idx); err != nil {
@@ -57,13 +68,22 @@ func (o *Object) Image(idx int) (*ebiten.Image, error) {
 		}
 	}
 
-	stdImg := o.raw.Sprites[idx].ToImage()
-	img, err := ebiten.NewImageFromImage(stdImg, ebiten.FilterDefault)
+	raw := o.raw.Sprites[idx]
+	img, err := ebiten.NewImageFromImage(raw.ToImage(), ebiten.FilterDefault)
 	if err != nil {
 		return nil, err
 	}
 
-	o.images[idx] = img
+	sprite := &Sprite{
+		obj:     o,
+		Width:   int(raw.Width),
+		Height:  int(raw.Width),
+		XOffset: int(raw.XOffset),
+		YOffset: int(raw.YOffset),
+		Image:   img,
+	}
 
-	return img, nil
+	o.sprites[idx] = sprite
+
+	return sprite, nil
 }