How can I judge user click position is on one QTreeView item(index) 's "+" (expanded flag)

[jzq740176597]

I need to do some process before the item collapsed or expanded. So I derived MyTreeView : public QTreeView .

Overload QTreeView ::MousePressEvent(). I know most stuff useful for me is in QTreeViewPrivate. But is private in QTreeView .the Derived MyTreeView is not accessible.

I think : VisualRect(index) and style()->getSubElement() . may help me to get the rect of "+" flag.

Thanks in advance for any advice!