add ability to gradually move camera to a target (aka heading to)

scripts/main_camera.gd

@@ -1,11 +1,17 @@
 extends Camera3D
 
+enum CameraState {
+	FREE,
+	HEADING_TO,
+}
+
 const ZOOM_SPEED: float = 0.1
 const ZOOM_DAMP: float = 5
 const ZOOM_VALUE_DEFAULT: float = 0.3
 ## How many pixels the mouse needs to be away
 ## from the screen edge to move the camera.
 const EDGE_THRESHOLD: float = 10
+const HEADING_SPEED: float = 1
 
 @export var zoom_in_distance: float = 5
 @export var zoom_in_fov: float = 25
@@ -23,10 +29,18 @@ var mouse_position: Vector2 = Vector2()
 var zoom_value: float = ZOOM_VALUE_DEFAULT
 var zoom_raw: float = zoom_value
 
-var mouse_outside_window: bool = false
+var heading_to_position: Vector3 = Vector3.ZERO
+var heading_from_position: Vector3 = Vector3.ZERO
+var heading_from_zoom: float = 0
+var heading_progress: float = 0
+
+var state: CameraState = CameraState.FREE
+
+var window_out_of_focus: bool = false
 
 
 func _process(delta: float) -> void:
+	_handle_heading_to(delta)
 	zoom_value = lerp(zoom_value, zoom_raw, delta * ZOOM_DAMP)
 
 	_handle_movement(delta)
@@ -56,19 +70,26 @@ func _input(event: InputEvent) -> void:
 			zoom_raw = clamp(zoom_raw, 0, 1)
 
 	if event.is_action_pressed("reset_camera"):
-		target_position = Vector3.ZERO
-		zoom_raw = ZOOM_VALUE_DEFAULT
+		head_to(Vector3.ZERO)
 
 
 func _notification(what: int) -> void:
-	if what == NOTIFICATION_WM_MOUSE_ENTER:
-		mouse_outside_window = false
-	elif what == NOTIFICATION_WM_MOUSE_EXIT:
-		mouse_outside_window = true
+	if what == NOTIFICATION_WM_WINDOW_FOCUS_IN:
+		window_out_of_focus = false
+	elif what == NOTIFICATION_WM_WINDOW_FOCUS_OUT:
+		window_out_of_focus = true
+
+
+func head_to(to: Vector3) -> void:
+	heading_to_position = to
+	heading_from_position = target_position
+	heading_progress = 0
+	heading_from_zoom = zoom_value
+	state = CameraState.HEADING_TO
 
 
 func _handle_movement(delta: float) -> void:
-	if mouse_outside_window:
+	if window_out_of_focus or state != CameraState.FREE:
 		return
 
 	var viewport_size := get_viewport().get_visible_rect().size
@@ -99,3 +120,29 @@ func _handle_movement(delta: float) -> void:
 	var speed: float = lerp(zoom_in_speed, zoom_out_speed, zoom_value)
 	var velocity := direction * speed
 	target_position += velocity * delta
+
+
+func _handle_heading_to(delta: float) -> void:
+	if state != CameraState.HEADING_TO:
+		return
+
+	if heading_progress >= 1:
+		target_position = heading_to_position
+		state = CameraState.FREE
+	
+	heading_progress += HEADING_SPEED * delta
+	target_position = lerp(heading_from_position, heading_to_position, heading_progress)
+	zoom_raw = quadratic_bezier(heading_from_zoom, 1, ZOOM_VALUE_DEFAULT, heading_progress)
+	zoom_value = zoom_raw
+
+	
+func quadratic_bezier(
+		p0: float,
+		p1: float,
+		p2: float,
+		t: float,
+) -> float:
+	var q0: float = lerp(p0, p1, t)
+	var q1: float = lerp(p1, p2, t)
+	var r: float = lerp(q0, q1, t)
+	return r