how can i expand the QTreeWidgetItem when i click the Icon or double click on anywhere the item ?

[opengpu2]

how can i expand the QTreeWidgetItem when i click the Icon or double click on anywhere the item ?
i want to simulate a "arrow icon" right same with the Qt itself has.
now i use QTreeWidgetItem::setIcon, but i found no way to just expand the item while i click on the Icon but not anywhere on the item.

thank you!