That was not a good solution! All I had to do was call QScrollArea::setWidgetResizeable(true); to make the root QWidget fill the QScrollArea.

Still have to tackle with the first problem: How to make, e.g. in the above screenshots, the black boxes change their appearance when the user e.g. selects from the menu View -> Blue Boxes, Double-size and it would change the appearance of the black boxes to "blue and double the size".

Should I:

1) Keep the movie data (see OP) in a simple data structure and construct new QWidgets every time the user requests their appearance to change via some factory pattern that returns whatever template (as in layout) generator function/object that takes the movie data as an argument and spits the desired QWidgets.
or 2) Sub-class QWidgets that have methods for changing their own appearance, perhaps combined with the above pattern suggestion, that are called when the user wants to use another layout for the movie items
or 3) Something else?

Thanks again.