private boolean isEnabled(@Nullable VirtualFile file, @Nullable EditorWindow window) {
    if (file == null || window == null) {
      return false;
    }
    if (!closeSource && FileEditorManagerImpl.forbidSplitFor(file)) {
      return false;
    }
    int minimum = closeSource ? 2 : 1;
    return window.getTabCount() >= minimum;
  }
private boolean isEnabled(@Nullable VirtualFile file, @Nullable EditorWindow window)