more transforms; fix first update-ordering crash :-)

engine/anim.go

@@ -16,6 +16,7 @@ type AnimFrame struct {
 }
 
 // Anim is n animation being displayed, together with the current state.
+// A nil *Anim can be used, but always returns 0 for the current frame.
 type Anim struct {
 	Frames  []AnimFrame
 	OneShot bool
@@ -25,18 +26,34 @@ type Anim struct {
 
 // Copy makes a shallow copy of the anim.
 func (a *Anim) Copy() *Anim {
+	if a == nil {
+		return nil
+	}
 	a2 := *a
 	return &a2
 }
 
 // CurrentFrame returns the frame number for the current index.
-func (a *Anim) CurrentFrame() int { return a.Frames[a.Index].Frame }
+func (a *Anim) CurrentFrame() int {
+	if a == nil {
+		return 0
+	}
+	return a.Frames[a.Index].Frame
+}
 
 // Reset resets both Index and Ticks to 0.
-func (a *Anim) Reset() { a.Index, a.Ticks = 0, 0 }
+func (a *Anim) Reset() {
+	if a == nil {
+		return
+	}
+	a.Index, a.Ticks = 0, 0
+}
 
 // Update increments the tick count and advances the frame if necessary.
 func (a *Anim) Update() error {
+	if a == nil {
+		return nil
+	}
 	a.Ticks++
 	if a.OneShot && a.Index == len(a.Frames)-1 {
 		// on the last frame of a one shot so remain on final frame

engine/billboard.go

@@ -30,13 +30,14 @@ type Billboard struct {
 }
 
 // Draw draws the image.
-func (b *Billboard) Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions) {
+func (b *Billboard) Draw(screen *ebiten.Image, opts *ebiten.DrawImageOptions) {
-	var geom ebiten.GeoM
+	screen.DrawImage(b.Src.Image(), opts)
-	geom.Translate(float64(b.Pos.X), float64(b.Pos.Y))
-	geom.Concat(opts.GeoM)
-	opts.GeoM = geom
-	screen.DrawImage(b.Src.Image(), &opts)
 }
 
 // Scan returns a slice containing Src.
 func (b *Billboard) Scan() []interface{} { return []interface{}{&b.Src} }
+
+func (b *Billboard) Transform() (opts ebiten.DrawImageOptions) {
+	opts.GeoM.Translate(float2(b.Pos))
+	return opts
+}

engine/debug.go

@@ -10,12 +10,21 @@ import (
 	"github.com/hajimehoshi/ebiten/v2/ebitenutil"
 )
 
-var _ interface {
+var (
+	_ interface {
 		Drawer
 		Hider
 	} = &PerfDisplay{}
 
+	_ interface {
+		Drawer
+		Hider
+		Updater
+	} = &DebugToast{}
+)
+
 func init() {
+	gob.Register(&DebugToast{})
 	gob.Register(&PerfDisplay{})
 }
 
@@ -28,7 +37,7 @@ type DebugToast struct {
 	Text  string
 }
 
-func (d *DebugToast) Draw(screen *ebiten.Image, _ ebiten.DrawImageOptions) {
+func (d *DebugToast) Draw(screen *ebiten.Image, _ *ebiten.DrawImageOptions) {
 	ebitenutil.DebugPrintAt(screen, d.Text, d.Pos.X, d.Pos.Y)
 }
 
@@ -54,7 +63,7 @@ type PerfDisplay struct {
 	Hidden
 }
 
-func (p PerfDisplay) Draw(screen *ebiten.Image, _ ebiten.DrawImageOptions) {
+func (p PerfDisplay) Draw(screen *ebiten.Image, _ *ebiten.DrawImageOptions) {
 	ebitenutil.DebugPrint(screen, fmt.Sprintf("TPS: %0.2f  FPS: %0.2f", ebiten.CurrentTPS(), ebiten.CurrentFPS()))
 }
 

engine/fill.go

@@ -28,6 +28,6 @@ type Fill struct {
 	ZOrder
 }
 
-func (f *Fill) Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions) {
+func (f *Fill) Draw(screen *ebiten.Image, opts *ebiten.DrawImageOptions) {
 	screen.Fill(opts.ColorM.Apply(f.Color))
 }

engine/game.go

@@ -104,7 +104,7 @@ func (g *Game) Draw(screen *ebiten.Image) {
 		if st.hidden {
 			continue
 		}
-		d.Draw(screen, st.opts)
+		d.Draw(screen, &st.opts)
 	}
 }
 
@@ -390,7 +390,7 @@ var _ Drawer = tombstone{}
 
 type tombstone struct{}
 
-func (tombstone) Draw(*ebiten.Image, ebiten.DrawImageOptions) {}
+func (tombstone) Draw(*ebiten.Image, *ebiten.DrawImageOptions) {}
 
 func (tombstone) DrawOrder() float64 { return math.Inf(1) }
 

engine/interface.go

@@ -79,7 +79,7 @@ type Disabler interface {
 // must call Draw on any internal components not known to the engine (i.e. not
 // passed to Game.Register or returned from Scan).
 type Drawer interface {
-	Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions)
+	Draw(screen *ebiten.Image, opts *ebiten.DrawImageOptions)
 	DrawOrder() float64
 }
 

engine/sprite.go

@@ -30,8 +30,8 @@ type Sprite struct {
 	anim *Anim
 }
 
-func (s *Sprite) Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions) {
+func (s *Sprite) Draw(screen *ebiten.Image, opts *ebiten.DrawImageOptions) {
-	screen.DrawImage(s.Sheet.SubImage(s.anim.CurrentFrame()), &opts)
+	screen.DrawImage(s.Sheet.SubImage(s.anim.CurrentFrame()), opts)
 }
 
 func (s *Sprite) Scan() []interface{} {
@@ -53,5 +53,6 @@ func (s *Sprite) Transform() (opts ebiten.DrawImageOptions) {
 	return opts
 }
 
-// anim isn't returned from Scan so we must update it ourselves
+// anim can change a bit so we don't tell Game about it, but that means it must
+// be updated here.
 func (s *Sprite) Update() error { return s.anim.Update() }

engine/tiles.go

@@ -65,7 +65,7 @@ func (t *Tilemap) CollidesWith(r image.Rectangle) bool {
 }
 
 // Draw draws the tilemap.
-func (t *Tilemap) Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions) {
+func (t *Tilemap) Draw(screen *ebiten.Image, opts *ebiten.DrawImageOptions) {
 	og := opts.GeoM
 	var geom ebiten.GeoM
 	for p, tile := range t.Map {
@@ -78,7 +78,7 @@ func (t *Tilemap) Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions) {
 		opts.GeoM = geom
 
 		src := t.Sheet.SubImage(tile.CellIndex())
-		screen.DrawImage(src, &opts)
+		screen.DrawImage(src, opts)
 	}
 }
 

engine/walls.go

@@ -78,14 +78,8 @@ type WallUnit struct {
 	wall *Wall
 }
 
-func (u *WallUnit) Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions) {
+func (u *WallUnit) Draw(screen *ebiten.Image, opts *ebiten.DrawImageOptions) {
-	var geom ebiten.GeoM
+	screen.DrawImage(u.wall.Sheet.SubImage(u.Tile.CellIndex()), opts)
-	geom.Translate(float2(mul2(u.Pos, u.wall.UnitSize).Add(u.wall.UnitOffset).Add(u.wall.Offset)))
-	geom.Concat(opts.GeoM)
-	opts.GeoM = geom
-
-	src := u.wall.Sheet.SubImage(u.Tile.CellIndex())
-	screen.DrawImage(src, &opts)
 }
 
 func (u *WallUnit) Prepare(g *Game) error {
@@ -95,3 +89,8 @@ func (u *WallUnit) Prepare(g *Game) error {
 }
 
 func (u *WallUnit) Scan() []interface{} { return []interface{}{u.Tile} }
+
+func (u *WallUnit) Transform() (opts ebiten.DrawImageOptions) {
+	opts.GeoM.Translate(float2(mul2(u.Pos, u.wall.UnitSize).Add(u.wall.UnitOffset).Add(u.wall.Offset)))
+	return opts
+}