ebiten: Add AppendInputChars, AppendGamepadIDs, and AppendTouchIDs

These functions reduce unnecessary allocations of arrays.

Closes #1692

examples/2048/2048/input.go

@@ -83,6 +83,7 @@ type Input struct {
 	mouseInitPosY int
 	mouseDir      Dir
 
+	touches       []ebiten.TouchID
 	touchState    touchState
 	touchID       ebiten.TouchID
 	touchInitPosX int
@@ -147,12 +148,13 @@ func (i *Input) Update() {
 	case mouseStateSettled:
 		i.mouseState = mouseStateNone
 	}
+
+	i.touches = ebiten.AppendTouchIDs(i.touches[:0])
 	switch i.touchState {
 	case touchStateNone:
-		ts := ebiten.TouchIDs()
+		if len(i.touches) == 1 {
-		if len(ts) == 1 {
+			i.touchID = i.touches[0]
-			i.touchID = ts[0]
+			x, y := ebiten.TouchPosition(i.touches[0])
-			x, y := ebiten.TouchPosition(ts[0])
 			i.touchInitPosX = x
 			i.touchInitPosY = y
 			i.touchLastPosX = x
@@ -160,21 +162,20 @@ func (i *Input) Update() {
 			i.touchState = touchStatePressing
 		}
 	case touchStatePressing:
-		ts := ebiten.TouchIDs()
+		if len(i.touches) >= 2 {
-		if len(ts) >= 2 {
 			break
 		}
-		if len(ts) == 1 {
+		if len(i.touches) == 1 {
-			if ts[0] != i.touchID {
+			if i.touches[0] != i.touchID {
 				i.touchState = touchStateInvalid
 			} else {
-				x, y := ebiten.TouchPosition(ts[0])
+				x, y := ebiten.TouchPosition(i.touches[0])
 				i.touchLastPosX = x
 				i.touchLastPosY = y
 			}
 			break
 		}
-		if len(ts) == 0 {
+		if len(i.touches) == 0 {
 			dx := i.touchLastPosX - i.touchInitPosX
 			dy := i.touchLastPosY - i.touchInitPosY
 			d, ok := vecToDir(dx, dy)
@@ -188,7 +189,7 @@ func (i *Input) Update() {
 	case touchStateSettled:
 		i.touchState = touchStateNone
 	case touchStateInvalid:
-		if len(ebiten.TouchIDs()) == 0 {
+		if len(i.touches) == 0 {
 			i.touchState = touchStateNone
 		}
 	}

examples/blocks/blocks/input.go

@@ -21,6 +21,7 @@ import (
 
 // Input manages the input state including gamepads and keyboards.
 type Input struct {
+	gamepadIDs                 []ebiten.GamepadID
 	virtualGamepadButtonStates map[virtualGamepadButton]int
 	gamepadConfig              gamepadConfig
 }
@@ -28,7 +29,8 @@ type Input struct {
 // GamepadIDButtonPressed returns a gamepad ID where at least one button is pressed.
 // If no button is pressed, GamepadIDButtonPressed returns -1.
 func (i *Input) GamepadIDButtonPressed() ebiten.GamepadID {
-	for _, id := range ebiten.GamepadIDs() {
+	i.gamepadIDs = ebiten.AppendGamepadIDs(i.gamepadIDs[:0])
+	for _, id := range i.gamepadIDs {
 		for b := ebiten.GamepadButton(0); b <= ebiten.GamepadButtonMax; b++ {
 			if ebiten.IsGamepadButtonPressed(id, b) {
 				return id

examples/flappy/main.go

@@ -176,6 +176,8 @@ type Game struct {
 	pipeTileYs []int
 
 	gameoverCount int
+
+	gamepadIDs []ebiten.GamepadID
 }
 
 func NewGame() *Game {
@@ -204,7 +206,7 @@ func isAnyKeyJustPressed() bool {
 	return false
 }
 
-func jump() bool {
+func (g *Game) jump() bool {
 	if isAnyKeyJustPressed() {
 		return true
 	}
@@ -214,7 +216,8 @@ func jump() bool {
 	if len(inpututil.JustPressedTouchIDs()) > 0 {
 		return true
 	}
-	for _, g := range ebiten.GamepadIDs() {
+	g.gamepadIDs = ebiten.AppendGamepadIDs(g.gamepadIDs[:0])
+	for _, g := range g.gamepadIDs {
 		for i := 0; i < ebiten.GamepadButtonNum(g); i++ {
 			if inpututil.IsGamepadButtonJustPressed(g, ebiten.GamepadButton(i)) {
 				return true
@@ -231,13 +234,13 @@ func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
 func (g *Game) Update() error {
 	switch g.mode {
 	case ModeTitle:
-		if jump() {
+		if g.jump() {
 			g.mode = ModeGame
 		}
 	case ModeGame:
 		g.x16 += 32
 		g.cameraX += 2
-		if jump() {
+		if g.jump() {
 			g.vy16 = -96
 			jumpPlayer.Rewind()
 			jumpPlayer.Play()
@@ -260,7 +263,7 @@ func (g *Game) Update() error {
 		if g.gameoverCount > 0 {
 			g.gameoverCount--
 		}
-		if g.gameoverCount == 0 && jump() {
+		if g.gameoverCount == 0 && g.jump() {
 			g.init()
 			g.mode = ModeTitle
 		}

examples/paint/main.go

@@ -60,7 +60,8 @@ func init() {
 }
 
 type Game struct {
-	count int
+	touches []ebiten.TouchID
+	count   int
 }
 
 func (g *Game) Update() error {
@@ -74,7 +75,8 @@ func (g *Game) Update() error {
 	}
 
 	// Paint the brush by touches
-	for _, t := range ebiten.TouchIDs() {
+	g.touches = ebiten.AppendTouchIDs(g.touches[:0])
+	for _, t := range g.touches {
 		x, y := ebiten.TouchPosition(t)
 		g.paint(canvasImage, x, y)
 		drawn = true
@@ -102,7 +104,7 @@ func (g *Game) Draw(screen *ebiten.Image) {
 
 	mx, my := ebiten.CursorPosition()
 	msg := fmt.Sprintf("(%d, %d)", mx, my)
-	for _, t := range ebiten.TouchIDs() {
+	for _, t := range g.touches {
 		x, y := ebiten.TouchPosition(t)
 		msg += fmt.Sprintf("\n(%d, %d) touch %d", x, y, t)
 	}

examples/sprites/main.go

@@ -115,9 +115,10 @@ const (
 )
 
 type Game struct {
-	sprites Sprites
+	touchIDs []ebiten.TouchID
-	op      ebiten.DrawImageOptions
+	sprites  Sprites
-	inited  bool
+	op       ebiten.DrawImageOptions
+	inited   bool
 }
 
 func (g *Game) init() {
@@ -144,8 +145,8 @@ func (g *Game) init() {
 	}
 }
 
-func leftTouched() bool {
+func (g *Game) leftTouched() bool {
-	for _, id := range ebiten.TouchIDs() {
+	for _, id := range g.touchIDs {
 		x, _ := ebiten.TouchPosition(id)
 		if x < screenWidth/2 {
 			return true
@@ -154,8 +155,8 @@ func leftTouched() bool {
 	return false
 }
 
-func rightTouched() bool {
+func (g *Game) rightTouched() bool {
-	for _, id := range ebiten.TouchIDs() {
+	for _, id := range g.touchIDs {
 		x, _ := ebiten.TouchPosition(id)
 		if x >= screenWidth/2 {
 			return true
@@ -168,9 +169,10 @@ func (g *Game) Update() error {
 	if !g.inited {
 		g.init()
 	}
+	g.touchIDs = ebiten.AppendTouchIDs(g.touchIDs[:0])
 
 	// Decrease the number of the sprites.
-	if ebiten.IsKeyPressed(ebiten.KeyArrowLeft) || leftTouched() {
+	if ebiten.IsKeyPressed(ebiten.KeyArrowLeft) || g.leftTouched() {
 		g.sprites.num -= 20
 		if g.sprites.num < MinSprites {
 			g.sprites.num = MinSprites
@@ -178,7 +180,7 @@ func (g *Game) Update() error {
 	}
 
 	// Increase the number of the sprites.
-	if ebiten.IsKeyPressed(ebiten.KeyArrowRight) || rightTouched() {
+	if ebiten.IsKeyPressed(ebiten.KeyArrowRight) || g.rightTouched() {
 		g.sprites.num += 20
 		if MaxSprites < g.sprites.num {
 			g.sprites.num = MaxSprites

examples/touch/main.go

@@ -74,10 +74,11 @@ type Game struct {
 	x, y float64
 	zoom float64
 
-	touches map[ebiten.TouchID]*touch
+	touchIDs []ebiten.TouchID
-	pinch   *pinch
+	touches  map[ebiten.TouchID]*touch
-	pan     *pan
+	pinch    *pinch
-	taps    []tap
+	pan      *pan
+	taps     []tap
 }
 
 func (g *Game) Update() error {
@@ -111,15 +112,17 @@ func (g *Game) Update() error {
 	// What touches are new in this frame?
 	for _, id := range inpututil.JustPressedTouchIDs() {
 		x, y := ebiten.TouchPosition(id)
-		g.touches[ebiten.TouchID(id)] = &touch{
+		g.touches[id] = &touch{
 			originX: x, originY: y,
 			currX: x, currY: y,
 		}
 	}
 
+	g.touchIDs = ebiten.AppendTouchIDs(g.touchIDs[:0])
+
 	// Update the current position and durations of any touches that have
 	// neither begun nor ended in this frame.
-	for _, id := range ebiten.TouchIDs() {
+	for _, id := range g.touchIDs {
 		t := g.touches[id]
 		t.duration = inpututil.TouchPressDuration(id)
 		t.currX, t.currY = ebiten.TouchPosition(id)
@@ -133,7 +136,7 @@ func (g *Game) Update() error {
 		// If the diff between their origins is different to the diff between
 		// their currents and if these two are not already a pinch, then this is
 		// a new pinch!
-		id1, id2 := ebiten.TouchIDs()[0], ebiten.TouchIDs()[1]
+		id1, id2 := g.touchIDs[0], g.touchIDs[1]
 		t1, t2 := g.touches[id1], g.touches[id2]
 		originDiff := distance(t1.originX, t1.originY, t2.originX, t2.originY)
 		currDiff := distance(t1.currX, t1.currY, t2.currX, t2.currY)
@@ -149,7 +152,7 @@ func (g *Game) Update() error {
 		}
 	case 1:
 		// Potentially this is a new pan.
-		id := ebiten.TouchIDs()[0]
+		id := g.touchIDs[0]
 		t := g.touches[id]
 		if !t.wasPinch && g.pan == nil && g.pinch == nil {
 			diff := math.Abs(distance(t.originX, t.originY, t.currX, t.currY))

examples/typewriter/main.go

@@ -48,15 +48,17 @@ func repeatingKeyPressed(key ebiten.Key) bool {
 }
 
 type Game struct {
+	runes   []rune
 	text    string
 	counter int
 }
 
 func (g *Game) Update() error {
-	// Add a string from InputChars, that returns string input by users.
+	// Add a string by AppendInputChars, that appends runes input by users.
-	// Note that InputChars result changes every frame, so you need to call this
+	// Note that AppendInputChars result changes every frame, so you need to call this
 	// every frame.
-	g.text += string(ebiten.InputChars())
+	g.runes = ebiten.AppendInputChars(g.runes[:0])
+	g.text += string(g.runes)
 
 	// Adjust the string to be at most 10 lines.
 	ss := strings.Split(g.text, "\n")

input.go

@@ -18,21 +18,30 @@ import (
 	"github.com/hajimehoshi/ebiten/v2/internal/driver"
 )
 
-// InputChars return "printable" runes read from the keyboard at the time update is called.
+// AppendInputChars appends "printable" runes, read from the keyboard at the time update is called, to runes,
+// and returns the extended buffer.
+// Giving a slice that already has enough capacity works efficiently.
 //
-// InputChars represents the environment's locale-dependent translation of keyboard
+// AppendInputChars represents the environment's locale-dependent translation of keyboard
 // input to Unicode characters.
 //
 // IsKeyPressed is based on a mapping of device (US keyboard) codes to input device keys.
 // "Control" and modifier keys should be handled with IsKeyPressed.
 //
-// InputChars is concurrent-safe.
+// AppendInputChars is concurrent-safe.
 //
 // On Android (ebitenmobile), EbitenView must be focusable to enable to handle keyboard keys.
 //
 // Keyboards don't work on iOS yet (#1090).
+func AppendInputChars(runes []rune) []rune {
+	return uiDriver().Input().AppendInputChars(runes)
+}
+
+// InputChars return "printable" runes read from the keyboard at the time update is called.
+//
+// Deprecated: as of v2.2.0. Use AppendInputChars instead.
 func InputChars() []rune {
-	return uiDriver().Input().AppendInputChars(nil)
+	return AppendInputChars(nil)
 }
 
 // IsKeyPressed returns a boolean indicating whether key is pressed.
@@ -134,13 +143,21 @@ func GamepadName(id GamepadID) string {
 	return uiDriver().Input().GamepadName(id)
 }
 
+// AppendGamepadIDs appends available gamepad IDs to gamepadIDs, and returns the extended buffer.
+// Giving a slice that already has enough capacity works efficiently.
+//
+// AppendGamepadIDs is concurrent-safe.
+//
+// AppendGamepadIDs doesn't append anything on iOS.
+func AppendGamepadIDs(gamepadIDs []GamepadID) []GamepadID {
+	return uiDriver().Input().AppendGamepadIDs(gamepadIDs)
+}
+
 // GamepadIDs returns a slice indicating available gamepad IDs.
 //
-// GamepadIDs is concurrent-safe.
+// Deprecated: as of v2.2.0. Use AppendGamepadIDs instead.
-//
-// GamepadIDs always returns an empty slice on iOS.
 func GamepadIDs() []GamepadID {
-	return uiDriver().Input().AppendGamepadIDs(nil)
+	return AppendGamepadIDs(nil)
 }
 
 // GamepadAxisNum returns the number of axes of the gamepad (id).
@@ -188,17 +205,25 @@ func IsGamepadButtonPressed(id GamepadID, button GamepadButton) bool {
 // TouchID represents a touch's identifier.
 type TouchID = driver.TouchID
 
-// TouchIDs returns the current touch states.
+// AppendTouchIDs appends the current touch states to touches, and returns the extended buffer.
+// Giving a slice that already has enough capacity works efficiently.
 //
 // If you want to know whether a touch started being pressed in the current frame,
 // use inpututil.JustPressedTouchIDs
 //
-// TouchIDs returns nil when there are no touches.
+// AppendTouchIDs doesn't append anything when there are no touches.
-// TouchIDs always returns nil on desktops.
+// AppendTouchIDs always does nothing on desktops.
 //
-// TouchIDs is concurrent-safe.
+// AppendTouchIDs is concurrent-safe.
+func AppendTouchIDs(touches []TouchID) []TouchID {
+	return uiDriver().Input().AppendTouchIDs(touches)
+}
+
+// TouchIDs returns the current touch states.
+//
+// Deperecated: as of v2.2.0. Use AppendTouchIDs instead.
 func TouchIDs() []TouchID {
-	return uiDriver().Input().AppendTouchIDs(nil)
+	return AppendTouchIDs(nil)
 }
 
 // TouchPosition returns the position for the touch of the specified ID.

inpututil/inpututil.go

@@ -40,6 +40,9 @@ type inputState struct {
 	touchDurations     map[ebiten.TouchID]int
 	prevTouchDurations map[ebiten.TouchID]int
 
+	gamepadIDsBuf []ebiten.GamepadID
+	touchIDsBuf   []ebiten.TouchID
+
 	m sync.RWMutex
 }
 
@@ -117,7 +120,8 @@ func (i *inputState) update() {
 	for id := range i.gamepadIDs {
 		delete(i.gamepadIDs, id)
 	}
-	for _, id := range ebiten.GamepadIDs() {
+	i.gamepadIDsBuf = ebiten.AppendGamepadIDs(i.gamepadIDsBuf[:0])
+	for _, id := range i.gamepadIDsBuf {
 		i.gamepadIDs[id] = struct{}{}
 		if _, ok := i.gamepadButtonDurations[id]; !ok {
 			i.gamepadButtonDurations[id] = make([]int, ebiten.GamepadButtonMax+1)
@@ -150,7 +154,8 @@ func (i *inputState) update() {
 	for id := range i.touchIDs {
 		delete(i.touchIDs, id)
 	}
-	for _, id := range ebiten.TouchIDs() {
+	i.touchIDsBuf = ebiten.AppendTouchIDs(i.touchIDsBuf[:0])
+	for _, id := range i.touchIDsBuf {
 		i.touchIDs[id] = struct{}{}
 		i.touchDurations[id]++
 	}