DebugRenderer + UI

How do i render some debug primitives on top of UI? I believe i somehow should convert result of UIElement::GetScreenPosition() to world coordinates and feed it to say AddQuad() bit it is not really clear to me. Help would be greatly appreciated. Thank you.

You might find this useful to convert screen space to world space:

After some digging turns out its Viewport::GetScreenRay().origin_. Not exactly obvious.