input: Add TouchIDs and TouchPosition (#497)

This change deprecates Touch interface and Touches function.

examples/2048/2048/input.go

@@ -149,10 +149,10 @@ func (i *Input) Update() {
 	}
 	switch i.touchState {
 	case touchStateNone:
-		ts := ebiten.Touches()
+		ts := ebiten.TouchIDs()
 		if len(ts) == 1 {
-			i.touchID = ts[0].ID()
-			x, y := ts[0].Position()
+			i.touchID = ts[0]
+			x, y := ebiten.TouchPosition(ts[0])
 			i.touchInitPosX = x
 			i.touchInitPosY = y
 			i.touchLastPosX = x
@@ -160,15 +160,15 @@ func (i *Input) Update() {
 			i.touchState = touchStatePressing
 		}
 	case touchStatePressing:
-		ts := ebiten.Touches()
+		ts := ebiten.TouchIDs()
 		if len(ts) >= 2 {
 			break
 		}
 		if len(ts) == 1 {
-			if ts[0].ID() != i.touchID {
+			if ts[0] != i.touchID {
 				i.touchState = touchStateInvalid
 			} else {
-				x, y := ts[0].Position()
+				x, y := ebiten.TouchPosition(ts[0])
 				i.touchLastPosX = x
 				i.touchLastPosY = y
 			}
@@ -188,7 +188,7 @@ func (i *Input) Update() {
 	case touchStateSettled:
 		i.touchState = touchStateNone
 	case touchStateInvalid:
-		if len(ebiten.Touches()) == 0 {
+		if len(ebiten.TouchIDs()) == 0 {
 			i.touchState = touchStateNone
 		}
 	}

examples/paint/main.go

@@ -82,8 +82,8 @@ func update(screen *ebiten.Image) error {
 	}
 
 	// Paint the brush by touches
-	for _, t := range ebiten.Touches() {
-		x, y := t.Position()
+	for _, t := range ebiten.TouchIDs() {
+		x, y := ebiten.TouchPosition(t)
 		paint(canvasImage, x, y)
 		drawn = true
 	}
@@ -98,9 +98,9 @@ func update(screen *ebiten.Image) error {
 	screen.DrawImage(canvasImage, nil)
 
 	msg := fmt.Sprintf("(%d, %d)", mx, my)
-	for _, t := range ebiten.Touches() {
-		x, y := t.Position()
-		msg += fmt.Sprintf("\n(%d, %d) touch %d", x, y, t.ID())
+	for _, t := range ebiten.TouchIDs() {
+		x, y := ebiten.TouchPosition(t)
+		msg += fmt.Sprintf("\n(%d, %d) touch %d", x, y, t)
 	}
 	ebitenutil.DebugPrint(screen, msg)
 	return nil

input.go

@@ -110,7 +110,35 @@ func IsGamepadButtonPressed(id int, button GamepadButton) bool {
 	return input.Get().IsGamepadButtonPressed(id, input.GamepadButton(button))
 }
 
-// Touch represents a touch state.
+// TouchIDs returns the current touch states.
+//
+// TouchIDs returns nil when there are no touches.
+// TouchIDs always returns nil on desktops.
+//
+// TouchIDs is concurrent-safe.
+func TouchIDs() []int {
+	var ids []int
+	for _, t := range ui.AdjustedTouches() {
+		ids = append(ids, t.ID())
+	}
+	return ids
+}
+
+// TouchPosition returns the position for the touch of the specified ID.
+//
+// If the touch of the specified ID is not present, TouchPosition returns (0, 0).
+//
+// TouchPosition is cuncurrent-safe.
+func TouchPosition(id int) (int, int) {
+	for _, t := range ui.AdjustedTouches() {
+		if t.ID() == id {
+			return t.Position()
+		}
+	}
+	return 0, 0
+}
+
+// Touch is deprecated as of 1.7.0. Use TouchPosition instead.
 type Touch interface {
 	// ID returns an identifier for one stroke.
 	ID() int
@@ -119,10 +147,7 @@ type Touch interface {
 	Position() (x, y int)
 }
 
-// Touches returns the current touch states.
-//
-// Touches returns nil when there are no touches.
-// Touches always returns nil on desktops.
+// Touches is deprecated as of 1.7.0. Use TouchIDs instead.
 func Touches() []Touch {
 	touches := ui.AdjustedTouches()
 	var copies []Touch

inpututil/inpututil.go

@@ -150,10 +150,10 @@ func (i *inputState) update() {
 		i.prevTouchDurations[id] = 0
 	}
 
-	for _, t := range ebiten.Touches() {
-		ids[t.ID()] = struct{}{}
-		i.prevTouchDurations[t.ID()] = i.touchDurations[t.ID()]
-		i.touchDurations[t.ID()]++
+	for _, id := range ebiten.TouchIDs() {
+		ids[id] = struct{}{}
+		i.prevTouchDurations[id] = i.touchDurations[id]
+		i.touchDurations[id]++
 	}
 	idsToDelete = []int{}
 	for id := range i.touchDurations {