private boolean isEnabled(@Nullable VirtualFile vFile, @Nullable EditorWindow window) {
    if (vFile == null || window == null) {
      return false;
    }
    if (!closeSource && FileEditorManagerImpl.forbidSplitFor(vFile)) {
      return false;
    }
    return window.getSiblings$intellij_platform_ide_impl().size() == 1;
  }
private boolean isEnabled(@Nullable VirtualFile vFile, @Nullable EditorWindow window)