How can i remove/hide qframe's white line?

Question

env: qt4.8.6 cpp

how can i remove these white thing and scroll bar?

it's a qframe embed a third exe, but i dont want these white line and scroll bar. these horizontalline verticalline have 10px width, what is it ? and how can i remove or hide it?

if qframe'size equal third exe's resolution ,these scrollbar will disappear , but the lefttop line and left line are still there, how can i remove/hide these white line ?

thanks

i have tried :

    ui.frame->setContentsMargins(0,0,0,0);
    ui.frame->setWindowFlags(Qt::FramelessWindowHint);
    ui.frame->setFrameShape(QFrame::NoFrame);
    QScrollArea* scrollArea = new QScrollArea(ui.widget);
    scrollArea->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    scrollArea->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);

but all of them cannot work

here is my problem's picture