inpututil: add AppendJustReleasedTouchIDs and TouchPreviousPosition

Closes #2057

examples/lasttouch/main.go

@@ -0,0 +1,87 @@
+// Copyright 2022 The Ebitengine Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build example
+// +build example
+
+package main
+
+import (
+	"fmt"
+	"log"
+
+	"github.com/hajimehoshi/ebiten/v2"
+	"github.com/hajimehoshi/ebiten/v2/ebitenutil"
+	"github.com/hajimehoshi/ebiten/v2/inpututil"
+)
+
+const (
+	screenWidth  = 640
+	screenHeight = 480
+)
+
+type pos struct {
+	x int
+	y int
+}
+
+type Game struct {
+	releasedTouchIDs   []ebiten.TouchID
+	lastTouchPositions []pos
+}
+
+func (g *Game) Update() error {
+	// In general, Append* function allocates a new slice if the given slice doesn't have enough capacity,
+	// or otherwise, just extends the length of the given slice.
+	//
+	// This example passes an empty slice that might have a capacity in order to reduce the chances of slice allocations.
+	// You can also pass 'nil' to AppendJustReleasedTouchIDs if you don't care the cost of creating slices.
+	// In this case, AppendJustReleasedTouchIDs would always create a new slice.
+	g.releasedTouchIDs = inpututil.AppendJustReleasedTouchIDs(g.releasedTouchIDs[:0])
+
+	for _, id := range g.releasedTouchIDs {
+		// Get the last position of the touch.
+		// ebiten.TouchPosition would not work as the touch has already gone in this tick.
+		x, y := inpututil.TouchPositionInPreviousTick(id)
+		g.lastTouchPositions = append(g.lastTouchPositions, pos{x: x, y: y})
+	}
+
+	const n = 10
+	if len(g.lastTouchPositions) > n {
+		copy(g.lastTouchPositions, g.lastTouchPositions[len(g.lastTouchPositions)-n:])
+		g.lastTouchPositions = g.lastTouchPositions[:n]
+	}
+
+	return nil
+}
+
+func (g *Game) Draw(screen *ebiten.Image) {
+	msg := "Touch the screen and release your finger from it.\n\nLast Positions:\n"
+	for _, p := range g.lastTouchPositions {
+		msg += fmt.Sprintf("  (%d, %d)\n", p.x, p.y)
+	}
+	ebitenutil.DebugPrint(screen, msg)
+}
+
+func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
+	return screenWidth, screenHeight
+}
+
+func main() {
+	ebiten.SetWindowSize(screenWidth, screenHeight)
+	ebiten.SetWindowTitle("Last Touch Positions (Ebiten Demo)")
+	if err := ebiten.RunGame(&Game{}); err != nil {
+		log.Fatal(err)
+	}
+}

inpututil/inpututil.go

@@ -23,6 +23,11 @@ import (
 	"github.com/hajimehoshi/ebiten/v2/internal/hooks"
 )
 
+type pos struct {
+	x int
+	y int
+}
+
 type inputState struct {
 	keyDurations     []int
 	prevKeyDurations []int
@@ -41,7 +46,9 @@ type inputState struct {
 
 	touchIDs           map[ebiten.TouchID]struct{}
 	touchDurations     map[ebiten.TouchID]int
+	touchPositions     map[ebiten.TouchID]pos
 	prevTouchDurations map[ebiten.TouchID]int
+	prevTouchPositions map[ebiten.TouchID]pos
 
 	gamepadIDsBuf []ebiten.GamepadID
 	touchIDsBuf   []ebiten.TouchID
@@ -67,7 +74,9 @@ var theInputState = &inputState{
 
 	touchIDs:           map[ebiten.TouchID]struct{}{},
 	touchDurations:     map[ebiten.TouchID]int{},
+	touchPositions:     map[ebiten.TouchID]pos{},
 	prevTouchDurations: map[ebiten.TouchID]int{},
+	prevTouchPositions: map[ebiten.TouchID]pos{},
 }
 
 func init() {
@@ -172,13 +181,19 @@ func (i *inputState) update() {
 
 	// Touches
 
-	// Copy the touch durations.
+	// Copy the touch durations and positions.
 	for id := range i.prevTouchDurations {
 		delete(i.prevTouchDurations, id)
 	}
 	for id := range i.touchDurations {
 		i.prevTouchDurations[id] = i.touchDurations[id]
 	}
+	for id := range i.prevTouchPositions {
+		delete(i.prevTouchPositions, id)
+	}
+	for id := range i.touchPositions {
+		i.prevTouchPositions[id] = i.touchPositions[id]
+	}
 
 	for id := range i.touchIDs {
 		delete(i.touchIDs, id)
@@ -187,10 +202,13 @@ func (i *inputState) update() {
 	for _, id := range i.touchIDsBuf {
 		i.touchIDs[id] = struct{}{}
 		i.touchDurations[id]++
+		x, y := ebiten.TouchPosition(id)
+		i.touchPositions[id] = pos{x: x, y: y}
 	}
 	for id := range i.touchDurations {
 		if _, ok := i.touchIDs[id]; !ok {
 			delete(i.touchDurations, id)
+			delete(i.touchPositions, id)
 		}
 	}
 }
@@ -403,18 +421,21 @@ func StandardGamepadButtonPressDuration(id ebiten.GamepadID, button ebiten.Stand
 //
 // AppendJustPressedTouchIDs is concurrent safe.
 func AppendJustPressedTouchIDs(touchIDs []ebiten.TouchID) []ebiten.TouchID {
-	origLen := len(touchIDs)
 	theInputState.m.RLock()
+	defer theInputState.m.RUnlock()
+
+	origLen := len(touchIDs)
 	for id, s := range theInputState.touchDurations {
 		if s == 1 {
 			touchIDs = append(touchIDs, id)
 		}
 	}
-	theInputState.m.RUnlock()
+
 	s := touchIDs[origLen:]
 	sort.Slice(s, func(a, b int) bool {
 		return s[a] < s[b]
 	})
+
 	return touchIDs
 }
 
@@ -425,15 +446,39 @@ func JustPressedTouchIDs() []ebiten.TouchID {
 	return AppendJustPressedTouchIDs(nil)
 }
 
+// AppendJustReleasedTouchIDs append touch IDs that are released just in the current tick to touchIDs,
+// and returns the extended buffer.
+// Giving a slice that already has enough capacity works efficiently.
+//
+// AppendJustReleasedTouchIDs is concurrent safe.
+func AppendJustReleasedTouchIDs(touchIDs []ebiten.TouchID) []ebiten.TouchID {
+	theInputState.m.RLock()
+	defer theInputState.m.RUnlock()
+
+	origLen := len(touchIDs)
+	for id := range theInputState.prevTouchDurations {
+		if theInputState.touchDurations[id] == 0 && theInputState.prevTouchDurations[id] > 0 {
+			touchIDs = append(touchIDs, id)
+		}
+	}
+
+	s := touchIDs[origLen:]
+	sort.Slice(s, func(a, b int) bool {
+		return s[a] < s[b]
+	})
+
+	return touchIDs
+}
+
 // IsTouchJustReleased returns a boolean value indicating
 // whether the given touch is released just in the current tick.
 //
 // IsTouchJustReleased is concurrent safe.
 func IsTouchJustReleased(id ebiten.TouchID) bool {
 	theInputState.m.RLock()
-	r := theInputState.touchDurations[id] == 0 && theInputState.prevTouchDurations[id] > 0
-	theInputState.m.RUnlock()
-	return r
+	defer theInputState.m.RUnlock()
+
+	return theInputState.touchDurations[id] == 0 && theInputState.prevTouchDurations[id] > 0
 }
 
 // TouchPressDuration returns how long the touch remains in ticks (Update).
@@ -445,3 +490,15 @@ func TouchPressDuration(id ebiten.TouchID) int {
 	theInputState.m.RUnlock()
 	return s
 }
+
+// TouchPositionInPreviousTick returns the position in the previous tick.
+// If the touch is a just-released touch, TouchPositionInPreviousTick returns the last position of the touch.
+//
+// TouchJustReleasedPosition is concurrent safe.
+func TouchPositionInPreviousTick(id ebiten.TouchID) (int, int) {
+	theInputState.m.RLock()
+	defer theInputState.m.RUnlock()
+
+	p := theInputState.prevTouchPositions[id]
+	return p.x, p.y
+}