rem: virtual QSize sizeHint() const  { return QSize(contentsWidth(), contentsHeight() + scrollBarHeight()); }
add: virtual QSize sizeHint() const  { return QSize(contentsWidth() + scrollBarWidth(), contentsHeight() + scrollBarHeight()); }
context: 		virtual QSize sizeHint() const  { return QSize(contentsWidth(), contentsHeight() + scrollBarHeight()); }