move Bounds from Camera to Scene; add SceneRef

engine/asset.go

@@ -1,6 +1,8 @@
 package engine
 
 import (
+	"compress/gzip"
+	"encoding/gob"
 	"image"
 	"io/fs"
 	"log"
@@ -71,3 +73,31 @@ func (r *ImageRef) Image() *ebiten.Image {
 	imageCache[r.Path] = r.image
 	return r.image
 }
+
+// SceneRef loads a gzipped, gob-encoded Scene from the asset FS.
+type SceneRef struct {
+	Path string
+
+	scene *Scene
+}
+
+func (r *SceneRef) Scene() *Scene {
+	if r.scene != nil {
+		return r.scene
+	}
+	f, err := AssetFS.Open(r.Path)
+	if err != nil {
+		log.Fatalf("Couldn't open asset: %v", err)
+	}
+	defer f.Close()
+
+	gz, err := gzip.NewReader(f)
+	if err != nil {
+		log.Fatalf("Couldn't gunzip asset: %v", err)
+	}
+	r.scene = new(Scene)
+	if err := gob.NewDecoder(gz).Decode(r.scene); err != nil {
+		log.Fatalf("Couldn't decode asset: %v", err)
+	}
+	return r.scene
+}

engine/camera.go

@@ -28,7 +28,6 @@ type Camera struct {
 	Scene *Scene
 
 	// Camera controls
-	Bounds image.Rectangle // world coordinates
 	Centre image.Point // world coordinates
 	Filter ebiten.Filter
 	Zoom   float64 // unitless
@@ -45,7 +44,7 @@ func (c *Camera) Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions) {
 	// The lower bound on zoom is the larger of
 	// { (ScreenWidth / BoundsWidth), (ScreenHeight / BoundsHeight) }
 	zoom := c.Zoom
-	sz := c.Bounds.Size()
+	sz := c.Scene.Bounds.Size()
 	if z := float64(c.game.ScreenWidth) / float64(sz.X); zoom < z {
 		zoom = z
 	}
@@ -58,17 +57,17 @@ func (c *Camera) Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions) {
 	// Camera frame currently Rectangle{ centre ± (screen/(2*zoom)) }.
 	sw2, sh2 := float64(c.game.ScreenWidth/2), float64(c.game.ScreenHeight/2)
 	swz, shz := int(sw2/zoom), int(sh2/zoom)
-	if centre.X-swz < c.Bounds.Min.X {
+	if centre.X-swz < c.Scene.Bounds.Min.X {
-		centre.X = c.Bounds.Min.X + swz
+		centre.X = c.Scene.Bounds.Min.X + swz
 	}
-	if centre.Y-shz < c.Bounds.Min.Y {
+	if centre.Y-shz < c.Scene.Bounds.Min.Y {
-		centre.Y = c.Bounds.Min.Y + shz
+		centre.Y = c.Scene.Bounds.Min.Y + shz
 	}
-	if centre.X+swz > c.Bounds.Max.X {
+	if centre.X+swz > c.Scene.Bounds.Max.X {
-		centre.X = c.Bounds.Max.X - swz
+		centre.X = c.Scene.Bounds.Max.X - swz
 	}
-	if centre.Y+shz > c.Bounds.Max.Y {
+	if centre.Y+shz > c.Scene.Bounds.Max.Y {
-		centre.Y = c.Bounds.Max.Y - shz
+		centre.Y = c.Scene.Bounds.Max.Y - shz
 	}
 
 	// Apply other options

engine/scene.go

@@ -2,6 +2,7 @@ package engine
 
 import (
 	"encoding/gob"
+	"image"
 	"math"
 	"sort"
 
@@ -24,11 +25,12 @@ func init() {
 
 // Scene manages drawing and updating a bunch of components.
 type Scene struct {
+	Bounds     image.Rectangle // world coordinates
 	Components []interface{}
 	Disabled   bool
-	ZOrder
 	Hidden     bool
 	ID
+	ZOrder
 }
 
 // Draw draws all components in order.

main.go

@@ -49,6 +49,7 @@ func main() {
 
 	level1 := &engine.Scene{
 		ID:     "level_1",
+		Bounds: image.Rect(-32, -32, 320+32, 240+32),
 		Components: []interface{}{
 			&engine.Fill{
 				Color:  color.Gray{100},
@@ -108,7 +109,6 @@ func main() {
 					KeyCombo: []ebiten.Key{ebiten.KeyControl, ebiten.KeyD},
 				},
 				&engine.Camera{
-					Bounds: image.Rect(-32, -32, 320+32, 240+32),
 					ID:    "game_camera",
 					Scene: level1,
 				},