inpututil: Add JustConnectedGamepadIDs / JustDisconnectedGamepadIDs

Fixes #505

examples/gamepad/main.go

@@ -37,6 +37,13 @@ func update(screen *ebiten.Image) error {
 	axes := map[int][]string{}
 	pressedButtons := map[int][]string{}
 
+	for _, id := range inpututil.JustConnectedGamepadIDs() {
+		log.Printf("gamepad connected: id: %d", id)
+	}
+	for _, id := range inpututil.JustDisconnectedGamepadIDs() {
+		log.Printf("gamepad disconnected: id: %d", id)
+	}
+
 	for _, id := range ids {
 		maxAxis := ebiten.GamepadAxisNum(id)
 		for a := 0; a < maxAxis; a++ {
@@ -51,10 +58,10 @@ func update(screen *ebiten.Image) error {
 
 			// Log some events.
 			if inpututil.IsGamepadButtonJustPressed(id, b) {
-				log.Printf("Button Just Pressed: id(%d), button(%d)", id, b)
+				log.Printf("button pressed: id: %d, button: %d", id, b)
 			}
 			if inpututil.IsGamepadButtonJustReleased(id, b) {
-				log.Printf("Button Just Released: id(%d), button(%d)", id, b)
+				log.Printf("button released: id: %d, button: %d", id, b)
 			}
 		}
 	}

inpututil/inpututil.go

@@ -32,6 +32,9 @@ type inputState struct {
 	mouseButtonDurations     map[ebiten.MouseButton]int
 	prevMouseButtonDurations map[ebiten.MouseButton]int
 
+	gamepadIDs     map[int]struct{}
+	prevGamepadIDs map[int]struct{}
+
 	gamepadButtonDurations     map[int]map[ebiten.GamepadButton]int
 	prevGamepadButtonDurations map[int]map[ebiten.GamepadButton]int
 
@@ -48,6 +51,9 @@ var theInputState = &inputState{
 	mouseButtonDurations:     map[ebiten.MouseButton]int{},
 	prevMouseButtonDurations: map[ebiten.MouseButton]int{},
 
+	gamepadIDs:     map[int]struct{}{},
+	prevGamepadIDs: map[int]struct{}{},
+
 	gamepadButtonDurations:     map[int]map[ebiten.GamepadButton]int{},
 	prevGamepadButtonDurations: map[int]map[ebiten.GamepadButton]int{},
 
@@ -92,15 +98,22 @@ func (i *inputState) update() {
 
 	// Gamepads
 
+	// Copy the gamepad IDs
+	i.prevGamepadIDs = map[int]struct{}{}
+	for id := range i.gamepadIDs {
+		i.prevGamepadIDs[id] = struct{}{}
+	}
+
 	// Reset the previous states first since some gamepad IDs might be already gone.
 	for id := range i.prevGamepadButtonDurations {
 		for b := range i.prevGamepadButtonDurations[id] {
 			i.prevGamepadButtonDurations[id][b] = 0
 		}
 	}
-	ids := map[int]struct{}{}
+
+	i.gamepadIDs = map[int]struct{}{}
 	for _, id := range ebiten.GamepadIDs() {
-		ids[id] = struct{}{}
+		i.gamepadIDs[id] = struct{}{}
 
 		if _, ok := i.prevGamepadButtonDurations[id]; !ok {
 			i.prevGamepadButtonDurations[id] = map[ebiten.GamepadButton]int{}
@@ -121,7 +134,7 @@ func (i *inputState) update() {
 	}
 	idsToDelete := []int{}
 	for id := range i.gamepadButtonDurations {
-		if _, ok := ids[id]; !ok {
+		if _, ok := i.gamepadIDs[id]; !ok {
 			idsToDelete = append(idsToDelete, id)
 		}
 	}
@@ -130,7 +143,7 @@ func (i *inputState) update() {
 	}
 
 	// Touches
-	ids = map[int]struct{}{}
+	ids := map[int]struct{}{}
 
 	// Reset the previous states first since some gamepad IDs might be already gone.
 	for id := range i.prevTouchDurations {
@@ -212,6 +225,32 @@ func MouseButtonPressDuration(button ebiten.MouseButton) int {
 	return s
 }
 
+func JustConnectedGamepadIDs() []int {
+	ids := []int{}
+	theInputState.m.RLock()
+	for id := range theInputState.gamepadIDs {
+		if _, ok := theInputState.prevGamepadIDs[id]; !ok {
+			ids = append(ids, id)
+		}
+	}
+	theInputState.m.RUnlock()
+	sort.Ints(ids)
+	return ids
+}
+
+func JustDisconnectedGamepadIDs() []int {
+	ids := []int{}
+	theInputState.m.RLock()
+	for id := range theInputState.prevGamepadIDs {
+		if _, ok := theInputState.gamepadIDs[id]; !ok {
+			ids = append(ids, id)
+		}
+	}
+	theInputState.m.RUnlock()
+	sort.Ints(ids)
+	return ids
+}
+
 // IsGamepadButtonJustPressed returns a boolean value indicating
 // whether the given gamepad button of the gamepad id is pressed just in the current frame.
 //