inpututil: Add AppendPressedKeys

Updates #1705

examples/flappy/main.go

@@ -177,6 +177,7 @@ type Game struct {
 
 	gameoverCount int
 
+	keys       []ebiten.Key
 	gamepadIDs []ebiten.GamepadID
 }
 
@@ -197,8 +198,9 @@ func (g *Game) init() {
 	}
 }
 
-func isAnyKeyJustPressed() bool {
-	for _, k := range inpututil.PressedKeys() {
+func (g *Game) isAnyKeyJustPressed() bool {
+	g.keys = inpututil.AppendPressedKeys(g.keys[:0])
+	for _, k := range g.keys {
 		if inpututil.IsKeyJustPressed(k) {
 			return true
 		}
@@ -207,7 +209,7 @@ func isAnyKeyJustPressed() bool {
 }
 
 func (g *Game) jump() bool {
-	if isAnyKeyJustPressed() {
+	if g.isAnyKeyJustPressed() {
 		return true
 	}
 	if inpututil.IsMouseButtonJustPressed(ebiten.MouseButtonLeft) {

examples/keyboard/main.go

@@ -52,7 +52,7 @@ type Game struct {
 }
 
 func (g *Game) Update() error {
-	g.keys = inpututil.PressedKeys()
+	g.keys = inpututil.AppendPressedKeys(g.keys[:0])
 	return nil
 }
 

inpututil/inpututil.go

@@ -166,14 +166,14 @@ func (i *inputState) update() {
 	}
 }
 
-// PressedKeys returns a set of currently pressed keyboard keys.
+// AppendPressedKeys append currently pressed keyboard keys to keys and returns the extended buffer.
+// Giving a slice that already has enough capacity works efficiently.
 //
-// PressedKeys is concurrent safe.
-func PressedKeys() []ebiten.Key {
+// AppendPressedKeys is concurrent safe.
+func AppendPressedKeys(keys []ebiten.Key) []ebiten.Key {
 	theInputState.m.RLock()
 	defer theInputState.m.RUnlock()
 
-	keys := make([]ebiten.Key, 0, len(theInputState.keyDurations))
 	for i, d := range theInputState.keyDurations {
 		if d == 0 {
 			continue
@@ -183,6 +183,13 @@ func PressedKeys() []ebiten.Key {
 	return keys
 }
 
+// PressedKeys returns a set of currently pressed keyboard keys.
+//
+// Deprecated: as of v2.2.0. Use AppendPressedKeys instead.
+func PressedKeys() []ebiten.Key {
+	return AppendPressedKeys(nil)
+}
+
 // IsKeyJustPressed returns a boolean value indicating
 // whether the given key is pressed just in the current frame.
 //