qt - widget - positioning

If you really want to set absolute positions, I would ignore using a layout altogether. You can manually set the positions of elements by using the move() function or the setGeometry() function.

QWidget *parent = new QWidget();
parent->resize(400, 400);

QPushButton *buttonA = new QPushButton(parent);
buttonA->setText("First Button");
buttonA->move(10, 10);

QPushButton *buttonB = new QPushButton(parent);
buttonB->setText("Second Button");
buttonB->move(15, 40);

Side note: I would avoid setting absolute positions of elements in Qt. Why? Well, Qt tries to be a platform-independent GUI library. On different platforms, a lot of display things can change (i.e. font size of text in push buttons) so the size of your actual push buttons can vary to accommodate large or smaller font sizes. This can throw off your meticulously spaced push buttons is you use absolute positions as in the example above.

If you use layouts, overlapping buttons or buttons falling off the edge of your window can be avoided.

You can see my answer for overlay button in QT: Qt Widget Overlays. This may help you to achieve what you want.