Here is part of my program interface, I can't show it, so it's just to let you now what the problem I have.

On top you can see a thin line around some shape, so this line is showing arond my QGraphicsView, I wanna to enable this line. I've tryed also setSpacing() and set Margin but it couldn't help. I think that problem is in how QLayout add QGraphicsView in layout, why this line is showing?