What owns what?

[Zlatomir]

1) "Root" QWidget is the widget that don't have a parent at construction if you don't set parameter for parent it is default 0, witch means the widget is a window/used for "parenting" other widgets.

2) Not sure what you meant. Why you want a simple QWidget in anything else? A QWidget has only basic stuff for containing other widgets (derived from QWidget and implementing some functionality)

3) I don't know the QGraphicsViewProxy, but basic rule is: if you add a widget to some container it will be auto-parented to that.

4/5) No, the layout is not really implicated in parent/child relation:

QVBoxLayout *lay = new QVBoxLayout(window);

QVBoxLayout *lay = new QVBoxLayout(window);

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This means that if you add some widgets to the layout that widgets will become child-widgets of the "window" widget.

6) I don't know, but why do you want some of that? It is your job to make sure that widgets that "need" each-other will be "alive" in the same time, that is the reason why we need to dynamically allocate widgets on the heap (using pointers and new).