有时，甚至很难找到测试对象可识别的父类，所以搜索必须从最顶层开始，例如从窗口开始。

And sometimes, it is difficult to find a recognizable ancestor of the test object, so the search has to begin from the top-level object, such as a window.

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当加壳程序即将被激活时、当处在最顶层的窗口被创建或者销毁时，系统会调用WH_SHELL钩子子程。

The system calls a WH_SHELL hook procedure when the shell application is about to be activated and when a top-level window is created or destroyed.

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