SelectionListener 实现的构造函数接受一个布尔变量，该变量定义要展开还是折叠树项目，具体取决于选中了哪个按钮。

The constructor for the SelectionListener implementation accepts a Boolean variable that defines whether the tree items are to be expanded or collapsed, depending on which button is selected.

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而且，该函数返回布尔值，因为为gtk Widget定义的delete - event信号的回调原型指明的是布尔返回值。

Also, the function returns a Boolean value because the callback prototype for the delete-event signal defined for GtkWidget states a Boolean return.

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清单1显示了一个简单的例子，它声明了一个包含6个属性的hash：一个字符串、一个整数、一个布尔值、一个未定义的属性、另一个hash和一个函数。

A simple example is shown in Listing 1, declaring a hash consisting of 6 attributes: a string, an integer, a Boolean, an undefined attribute, another hash, and a function.

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