c++ - 什么是树形小部件的视口(viewport)？

Question

我正在尝试定位树形小部件的项目。
在文档中查找，我得到:

QTreeWidgetItem * QTreeWidget::itemAt ( const QPoint & p ) const

Returns a pointer to the item at the coordinates p. The coordinates are relative to the tree widget's viewport().

viewport() 函数也没有给出关于viewport 的定义。
那么什么是树形小部件的视口(viewport)？

Answer 1

QTreeWidget 继承自QAbstractScrollArea ，这是定义视口(viewport)的地方:

QAbstractScrollArea is a low-level abstraction of a scrolling area. The area provides a central widget called the viewport, in which the contents of the area is to be scrolled (i.e, the visible parts of the contents are rendered in the viewport).

视口(viewport)本质上是树的可见部分。