From a79c287bb774494088cf550e28bb4f6865a62b87 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Sat, 10 Jul 2021 22:18:13 +0900
Subject: [PATCH] inpututil: Add AppendPressedKeys

Updates #1705
---
 examples/flappy/main.go   |  8 +++++---
 examples/keyboard/main.go |  2 +-
 inpututil/inpututil.go    | 15 +++++++++++----
 3 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/examples/flappy/main.go b/examples/flappy/main.go
index 1ec3b60b9..3b2bc638b 100644
--- a/examples/flappy/main.go
+++ b/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) {
diff --git a/examples/keyboard/main.go b/examples/keyboard/main.go
index 8fa1d8744..ea121e053 100644
--- a/examples/keyboard/main.go
+++ b/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
 }
 
diff --git a/inpututil/inpututil.go b/inpututil/inpututil.go
index 06dcc2e1e..812af885c 100644
--- a/inpututil/inpututil.go
+++ b/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.
 //