[Qt-interest] QLayout::SizeConstraint

[Mitchell L Model]

To what does "main widget" refer in the documentation of  
QLayout::SizeConstraint? For example:

	QLayout::SetFixedSize			The main widget's size is set to sizeHint();  
it cannot be resized at all

Is there a widget associated with the QLayout itself? If so, does it  
"contain" the layout or does the layout "contain" the widget?