From a355d701ad2ad8342f7c06ba8c2d64b9bc81c0f1 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Mon, 30 Apr 2018 04:34:15 +0900
Subject: [PATCH] inpututil: Replace JustDisconnectedGamepadIDs with
 IsGamepadJustDisconnected (#505)

---
 examples/gamepad/main.go | 15 ++++++++++++---
 inpututil/inpututil.go   | 20 +++++++-------------
 2 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/examples/gamepad/main.go b/examples/gamepad/main.go
index 52f5530c8..f55a4ab40 100644
--- a/examples/gamepad/main.go
+++ b/examples/gamepad/main.go
@@ -32,12 +32,21 @@ const (
 	screenHeight = 480
 )
 
+var (
+	gamepadIDs = map[int]struct{}{}
+)
+
 func update(screen *ebiten.Image) error {
+	// Log the gamepad connection events.
 	for _, id := range inpututil.JustConnectedGamepadIDs() {
 		log.Printf("gamepad connected: id: %d", id)
+		gamepadIDs[id] = struct{}{}
 	}
-	for _, id := range inpututil.JustDisconnectedGamepadIDs() {
-		log.Printf("gamepad disconnected: id: %d", id)
+	for id := range gamepadIDs {
+		if inpututil.IsGamepadJustDisconnected(id) {
+			log.Printf("gamepad disconnected: id: %d", id)
+			delete(gamepadIDs, id)
+		}
 	}
 
 	ids := ebiten.GamepadIDs()
@@ -56,7 +65,7 @@ func update(screen *ebiten.Image) error {
 				pressedButtons[id] = append(pressedButtons[id], strconv.Itoa(int(b)))
 			}
 
-			// Log some events.
+			// Log button events.
 			if inpututil.IsGamepadButtonJustPressed(id, b) {
 				log.Printf("button pressed: id: %d, button: %d", id, b)
 			}
diff --git a/inpututil/inpututil.go b/inpututil/inpututil.go
index 8a10b5610..f1c5722e9 100644
--- a/inpututil/inpututil.go
+++ b/inpututil/inpututil.go
@@ -243,22 +243,16 @@ func JustConnectedGamepadIDs() []int {
 	return ids
 }
 
-// JustDisconnectedGamepadIDs returns gamepad IDs that are disconnected just in the current frame.
+// IsGamepadJustDisconnected returns a boolean value indicating
+// whether the gamepad of the given id is released just in the current frame.
 //
-// JustDisconnectedGamepadIDs might return nil when there is no disconnected gamepad.
-//
-// JustDisconnectedGamepadIDs is concurrent safe.
-func JustDisconnectedGamepadIDs() []int {
-	var ids []int
+// IsGamepadJustDisconnected is concurrent safe.
+func IsGamepadJustDisconnected(id int) bool {
 	theInputState.m.RLock()
-	for id := range theInputState.prevGamepadIDs {
-		if _, ok := theInputState.gamepadIDs[id]; !ok {
-			ids = append(ids, id)
-		}
-	}
+	_, prev := theInputState.prevGamepadIDs[id]
+	_, current := theInputState.gamepadIDs[id]
 	theInputState.m.RUnlock()
-	sort.Ints(ids)
-	return ids
+	return prev && !current
 }
 
 // IsGamepadButtonJustPressed returns a boolean value indicating