examples/2048: Animate tiles

examples/2048/2048/board.go

@@ -15,14 +15,19 @@
 package twenty48
 
 import (
-	"image/color"
+	"errors"
 
 	"github.com/hajimehoshi/ebiten"
 )
 
+var taskTerminated = errors.New("twenty48: task terminated")
+
+type task func() error
+
 type Board struct {
 	size  int
 	tiles map[*Tile]struct{}
+	tasks []task
 }
 
 func NewBoard(size int) *Board {
@@ -40,66 +45,79 @@ func (b *Board) tileAt(x, y int) *Tile {
 	return tileAt(b.tiles, x, y)
 }
 
+func (b *Board) isAnimating() bool {
+	for t := range b.tiles {
+		if t.isAnimating() {
+			return true
+		}
+	}
+	return false
+}
+
 func (b *Board) Update(input *Input) error {
+	if 0 < len(b.tasks) {
+		t := b.tasks[0]
+		err := t()
+		if err == taskTerminated {
+			b.tasks = b.tasks[1:]
+		} else if err != nil {
+			return err
+		}
+		return nil
+	}
 	if dir, ok := input.Dir(); ok {
 		if err := b.Move(dir); err != nil {
 			return err
 		}
 	}
+	return nil
+}
+
+func (b *Board) Move(dir Dir) error {
+	if !MoveTiles(b.tiles, b.size, dir) {
+		return nil
+	}
+	b.tasks = append(b.tasks, func() error {
 		for t := range b.tiles {
 			if err := t.Update(); err != nil {
 				return err
 			}
 		}
+		for t := range b.tiles {
+			if t.isAnimating() {
+				return nil
+			}
+		}
+		return taskTerminated
+	})
+	b.tasks = append(b.tasks, func() error {
 		nextTiles := map[*Tile]struct{}{}
 		for t := range b.tiles {
+			if t.next.value != 0 {
+				panic("not reach")
+			}
 			if t.current.value == 0 {
 				continue
 			}
 			nextTiles[t] = struct{}{}
 		}
 		b.tiles = nextTiles
-	return nil
-}
-
-func (b *Board) Move(dir Dir) error {
-	if moved := MoveTiles(b.tiles, b.size, dir); !moved {
-		return nil
-	}
 		if err := addRandomTile(b.tiles, b.size); err != nil {
 			return err
 		}
+		return taskTerminated
+	})
 	return nil
 }
 
-const (
-	tileSize   = 40
-	tileMargin = 2
-)
-
-var (
-	tileImage *ebiten.Image
-)
-
-func init() {
-	var err error
-	tileImage, err = ebiten.NewImage(tileSize, tileSize, ebiten.FilterNearest)
-	if err != nil {
-		panic(err)
-	}
-	if err := tileImage.Fill(color.White); err != nil {
-		panic(err)
-	}
-}
-
 func (b *Board) Size() (int, int) {
 	x := b.size*tileSize + (b.size+1)*tileMargin
 	y := x
 	return x, y
 }
 
-func (b *Board) Draw(screen *ebiten.Image) error {
-	if err := screen.Fill(frameColor); err != nil {
+func (b *Board) Draw(boardImage *ebiten.Image) error {
+	if err := boardImage.Fill(frameColor); err != nil {
 		return err
 	}
 	for j := 0; j < b.size; j++ {
@@ -111,13 +129,27 @@ func (b *Board) Draw(screen *ebiten.Image) error {
 			op.GeoM.Translate(float64(x), float64(y))
 			r, g, b, a := colorToScale(tileBackgroundColor(v))
 			op.ColorM.Scale(r, g, b, a)
-			if err := screen.DrawImage(tileImage, op); err != nil {
+			if err := boardImage.DrawImage(tileImage, op); err != nil {
 				return err
 			}
 		}
 	}
+	animatingTiles := map[*Tile]struct{}{}
+	nonAnimatingTiles := map[*Tile]struct{}{}
 	for t := range b.tiles {
-		if err := t.Draw(screen); err != nil {
+		if t.isAnimating() {
+			animatingTiles[t] = struct{}{}
+		} else {
+			nonAnimatingTiles[t] = struct{}{}
+		}
+	}
+	for t := range nonAnimatingTiles {
+		if err := t.Draw(boardImage); err != nil {
+			return err
+		}
+	}
+	for t := range animatingTiles {
+		if err := t.Draw(boardImage); err != nil {
 			return err
 		}
 	}

examples/2048/2048/tile.go

@@ -34,7 +34,7 @@ type TileData struct {
 type Tile struct {
 	current        TileData
 	next           TileData
-	moving  bool
+	animationCount int
 }
 
 func NewTile(value int, x, y int) *Tile {
@@ -63,6 +63,10 @@ func (t *Tile) NextPos() (int, int) {
 	return t.next.x, t.next.y
 }
 
+func (t *Tile) isAnimating() bool {
+	return 0 < t.animationCount
+}
+
 func tileAt(tiles map[*Tile]struct{}, x, y int) *Tile {
 	var result *Tile
 	for t := range tiles {
@@ -91,6 +95,10 @@ func nextTileAt(tiles map[*Tile]struct{}, x, y int) *Tile {
 	return result
 }
 
+const (
+	maxAnimationCount = 10
+)
+
 func MoveTiles(tiles map[*Tile]struct{}, size int, dir Dir) bool {
 	vx, vy := dir.Vector()
 	tx := []int{}
@@ -113,6 +121,9 @@ func MoveTiles(tiles map[*Tile]struct{}, size int, dir Dir) bool {
 			if t == nil {
 				continue
 			}
+			if t.animationCount != 0 {
+				panic("not reach")
+			}
 			ii := i
 			jj := j
 			for {
@@ -140,15 +151,17 @@ func MoveTiles(tiles map[*Tile]struct{}, size int, dir Dir) bool {
 				moved = true
 				break
 			}
+			next := TileData{}
+			next.value = t.current.value
 			if tt := nextTileAt(tiles, ii, jj); tt != t && tt != nil {
-				t.next.value = t.current.value + tt.next.value
+				next.value = t.current.value + tt.next.value
 				tt.next = TileData{}
-			} else {
-				t.next.value = t.current.value
+				tt.animationCount = 1
 			}
-			t.next.x = ii
-			t.next.y = jj
-			t.moving = true
+			next.x = ii
+			next.y = jj
+			t.next = next
+			t.animationCount = maxAnimationCount
 		}
 	}
 	return moved
@@ -157,12 +170,10 @@ func MoveTiles(tiles map[*Tile]struct{}, size int, dir Dir) bool {
 func addRandomTile(tiles map[*Tile]struct{}, size int) error {
 	cells := make([]bool, size*size)
 	for t := range tiles {
-		i := 0
-		if t.moving {
-			i = t.next.x + t.next.y*size
-		} else {
-			i = t.current.x + t.current.y*size
+		if t.isAnimating() {
+			panic("not reach")
 		}
+		i := t.current.x + t.current.y*size
 		cells[i] = true
 	}
 	availableCells := []int{}
@@ -188,12 +199,17 @@ func addRandomTile(tiles map[*Tile]struct{}, size int) error {
 }
 
 func (t *Tile) Update() error {
-	if !t.moving {
+	if t.animationCount == 0 {
+		if t.next.value != 0 {
+			panic("not reach")
+		}
 		return nil
 	}
+	t.animationCount--
+	if t.animationCount == 0 {
 		t.current = t.next
 		t.next = TileData{}
-	t.moving = false
+	}
 	return nil
 }
 
@@ -212,12 +228,47 @@ func colorToScale(clr color.Color) (float64, float64, float64, float64) {
 	return rf, gf, bf, af
 }
 
+func mean(a, b int, rate float64) int {
+	return int(float64(a)*rate + float64(b)*(1-rate))
+}
+
+const (
+	tileSize   = 40
+	tileMargin = 2
+)
+
+var (
+	tileImage *ebiten.Image
+)
+
+func init() {
+	var err error
+	tileImage, err = ebiten.NewImage(tileSize, tileSize, ebiten.FilterNearest)
+	if err != nil {
+		panic(err)
+	}
+	if err := tileImage.Fill(color.White); err != nil {
+		panic(err)
+	}
+}
+
 func (t *Tile) Draw(boardImage *ebiten.Image) error {
 	i, j := t.current.x, t.current.y
+	ni, nj := t.next.x, t.next.y
 	v := t.current.value
+	if v == 0 {
+		return nil
+	}
 	op := &ebiten.DrawImageOptions{}
 	x := i*tileSize + (i+1)*tileMargin
 	y := j*tileSize + (j+1)*tileMargin
+	nx := ni*tileSize + (ni+1)*tileMargin
+	ny := nj*tileSize + (nj+1)*tileMargin
+	if 0 < t.animationCount && t.next.value != 0 {
+		rate := float64(t.animationCount) / maxAnimationCount
+		x = mean(x, nx, rate)
+		y = mean(y, ny, rate)
+	}
 	op.GeoM.Translate(float64(x), float64(y))
 	r, g, b, a := colorToScale(tileBackgroundColor(v))
 	op.ColorM.Scale(r, g, b, a)

examples/2048/2048/tile_test.go

@@ -103,6 +103,21 @@ func TestMoveTiles(t *testing.T) {
 				0, 0, 0, 0,
 			},
 		},
+		{
+			Dir: DirLeft,
+			Input: []int{
+				0, 2, 2, 2,
+				0, 0, 0, 0,
+				0, 0, 0, 0,
+				0, 0, 0, 0,
+			},
+			Want: []int{
+				4, 2, 0, 0,
+				0, 0, 0, 0,
+				0, 0, 0, 0,
+				0, 0, 0, 0,
+			},
+		},
 		{
 			Dir: DirRight,
 			Input: []int{