some tidyups

engine/actor.go

@@ -23,7 +23,6 @@ type Actor struct {
 }
 
 func (a *Actor) CollidesAt(p image.Point) bool {
-	// TODO: more efficient test?
 	hit := false
 	Walk(a.collisionDomain, func(c interface{}) bool {
 		if coll, ok := c.(Collider); ok {

engine/camera.go

@@ -20,15 +20,20 @@ type Camera struct {
 
 	Filter ebiten.Filter
 
-	game      *Game
+	game *Game
-	zoomBound float64
 }
 
 // Draw applies transformations to opts, then calls c.Scene.Draw with it.
 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
-	if zoom < c.zoomBound {
+	sz := c.Bounds.Size()
-		zoom = c.zoomBound
+	if z := float64(c.game.ScreenWidth) / float64(sz.X); zoom < z {
+		zoom = z
+	}
+	if z := float64(c.game.ScreenHeight) / float64(sz.Y); zoom < z {
+		zoom = z
 	}
 
 	// If the configured centre puts the camera out of bounds, move it.
@@ -70,16 +75,5 @@ func (c *Camera) Update() error { return c.Scene.Update() }
 // Scan returns the only child (c.Scene).
 func (c *Camera) Scan() []interface{} { return []interface{}{c.Scene} }
 
-// Prepare, among other things, computes the lower bound for Zoom based on
+// Prepare grabs a copy of game.
-// c.Bounds and game.ScreenWidth/Height.
+func (c *Camera) Prepare(game *Game) { c.game = game }
-func (c *Camera) Prepare(game *Game) {
-	c.game = game
-
-	// The lower bound on zoom is the larger of
-	// { (ScreenWidth / BoundsWidth), (ScreenHeight / BoundsHeight) }
-	sz := c.Bounds.Size()
-	c.zoomBound = float64(c.game.ScreenWidth) / float64(sz.X)
-	if z := float64(c.game.ScreenHeight) / float64(sz.Y); c.zoomBound < z {
-		c.zoomBound = z
-	}
-}

engine/debug.go

@@ -30,7 +30,7 @@ func (p PerfDisplay) Draw(screen *ebiten.Image, _ ebiten.DrawImageOptions) {
 	ebitenutil.DebugPrint(screen, fmt.Sprintf("TPS: %0.2f  FPS: %0.2f", ebiten.CurrentTPS(), ebiten.CurrentFPS()))
 }
 
-func (PerfDisplay) Z() float64 {
+func (PerfDisplay) DrawOrder() float64 {
 	// Always draw on top
 	return math.MaxFloat64
 }

engine/fill.go

@@ -8,10 +8,10 @@ import (
 
 // Fill fills the screen with a colour.
 type Fill struct {
-	Color  color.Color
+	Color color.Color
+	DrawOrder
 	Hidden bool
 	ID
-	DrawOrder
 }
 
 func (f *Fill) Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions) {

engine/scene.go

@@ -16,9 +16,9 @@ func init() {
 type Scene struct {
 	Components []interface{}
 	Disabled   bool
-	Hidden     bool
-	ID
 	DrawOrder
+	Hidden bool
+	ID
 }
 
 // Draw draws all components in order.
@@ -26,6 +26,7 @@ func (s *Scene) Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions) {
 	if s.Hidden {
 		return
 	}
+	// Draw everything.
 	for _, i := range s.Components {
 		if d, ok := i.(Drawer); ok {
 			d.Draw(screen, opts)
@@ -34,7 +35,7 @@ func (s *Scene) Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions) {
 }
 
 // Prepare does an initial Z-order sort.
-func (s *Scene) Prepare(*Game) { s.sortByDrawOrder() }
+func (s *Scene) Prepare(game *Game) { s.sortByDrawOrder() }
 
 // sortByDrawOrder sorts the components by Z position.
 // Everything without a Z sorts first. Stable sort is used to avoid Z-fighting

engine/sprite.go

@@ -14,12 +14,12 @@ func init() {
 // Sprite combines an Actor with the ability to Draw from a single spritesheet.
 type Sprite struct {
 	Actor
+	DrawOrder
 	FrameSize   image.Point
 	FrameOffset image.Point
 	Hidden      bool
 	ID
 	Src ImageRef
-	DrawOrder
 
 	anim *Anim
 }

engine/tiles.go

@@ -16,14 +16,14 @@ func init() {
 // Tilemap renders a grid of tiles.
 type Tilemap struct {
 	Disabled bool
-	Hidden   bool
+	DrawOrder
+	Hidden bool
 	ID
 	Map      map[image.Point]Tile
 	Ersatz   bool        // "fake wall"
 	Offset   image.Point // world coordinates
 	Src      ImageRef
 	TileSize int
-	DrawOrder
 }
 
 // CollidesWith implements Collider.

main.go

@@ -51,15 +51,15 @@ func main() {
 		ID: "level_1",
 		Components: []interface{}{
 			&engine.Fill{
-				Color: color.Gray{100},
+				Color:     color.Gray{100},
-				DrawOrder:  0,
+				DrawOrder: 0,
 			},
 			&engine.Tilemap{
-				ID:       "terrain",
+				ID:        "terrain",
-				Map:      tiles,
+				DrawOrder: 1,
-				Src:      engine.ImageRef{Path: "assets/boxes.png"},
+				Map:       tiles,
-				TileSize: 16,
+				Src:       engine.ImageRef{Path: "assets/boxes.png"},
-				DrawOrder:     1,
+				TileSize:  16,
 			},
 			&engine.SolidRect{
 				ID:   "ceiling",
@@ -74,7 +74,7 @@ func main() {
 				Rect: image.Rect(320, 0, 321, 240),
 			},
 			&game.Awakeman{
-				CameraID: "level_1_camera",
+				CameraID: "game_camera",
 				Sprite: engine.Sprite{
 					ID: "awakeman",
 					Actor: engine.Actor{
@@ -82,10 +82,10 @@ func main() {
 						Pos:             image.Pt(100, 100),
 						Size:            image.Pt(8, 16),
 					},
+					DrawOrder:   2,
 					FrameOffset: image.Pt(-1, 0),
 					FrameSize:   image.Pt(10, 16),
 					Src:         engine.ImageRef{Path: "assets/aw.png"},
-					DrawOrder:        2,
 				},
 			},
 		},
@@ -101,8 +101,8 @@ func main() {
 					KeyCombo: []ebiten.Key{ebiten.KeyControl, ebiten.KeyD},
 				},
 				&engine.Camera{
-					ID:     "level_1_camera",
 					Bounds: image.Rect(-32, -32, 320+32, 240+32),
+					ID:     "game_camera",
 					Scene:  level1,
 				},
 				engine.PerfDisplay{},