Ok, I understand that this is not possible and why it is.
The datasource methods load, when needed, the view controllers that are before and after the current one. Making these view controllers' views always visible, as I desired, will require that the datasource loads more than one view controllers after (or before, depends on the direction of scrolling) the current one, to be ready for the pan actions (potentially, before the animation is ended by the user lifting up its finger, two view controllers "after" or "before" could become visible it my desired configuration), and this is not intended by UIPageViewController
on iPhone, especially in portrait mode.
So actually, the only way to achieve that more than one view is visible in an horizontal-scrolling component at any time, is to implement a UIScrollview
with horizontal paging and calculate the contentSize
and other sizes accordingly.