Cannot find member “window_fullscreen“ in base “OS“.

Problem Description

Cannot find member “window_fullscreen” in base “OS”.

backtracking method

func _input(event):
	if event.is_action_pressed("toggle_fullscreen"):
		OS.window_fullscreen = !OS.window_fullscreen
		get_tree().set_input_as_handled()

Screenshot of problem

Solution: Implement the toggle_fullscreen function and replace OS.window_fullscreen = !OS.window_fullscreen

toggle_fullscreen method implementation

func toggle_fullscreen():
	if DisplayServer.window_get_mode() == DisplayServer.WINDOW_MODE_WINDOWED:
		DisplayServer.window_set_mode(DisplayServer.WINDOW_MODE_FULLSCREEN)
	else:
		DisplayServer.window_set_mode(DisplayServer.WINDOW_MODE_WINDOWED)