Drawing tab bar base behind some other control

FrameTabBarBase.cpp

QStylePainter p(this);

QStyleOptionTab tabOverlap;
int overlap = style()->pixelMetric(QStyle::PM_TabBarBaseOverlap, &tabOverlap);

QStyleOptionTabBarBase tabBarStyleOption;
tabBarStyleOption.rect.setRect(0, height() - overlap, width(), overlap);
tabBarStyleOption.tabBarRect = rect();
p.drawPrimitive(QStyle::PE_FrameTabBarBase, tabBarStyleOption);