Detailed Description

This handy class takes a copy of a TreeViewItem's openness when you create it, and restores that openness state when its destructor is called.

This can very handy when you're refreshing sub-items - e.g.

void MyTreeViewItem::updateChildItems()
{
    OpennessRestorer openness (*this);  //  saves the openness state here..
 
    clearSubItems();
 
    // add a bunch of sub-items here which may or may not be the same as the ones that
    // were previously there
    addSubItem (...
 
    // ..and at this point, the old openness is restored, so any items that haven't
    // changed will have their old openness retained.
}