First of all I would like to say that I\' ve already read all the other questions about Qt and MVC, but I couldn\'t find what I\'m looking for. So please, unless you find so
There are varying definitions of "MVC". If you mean Model-View-MEDIATING Controller, I think it is best to use the term MVA, i.e. Model-View-Adapter. Check this out: https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93adapter
A class called MainWindow is absolutely part of a view per this model. The fact that the object is window makes it a type of view. I have a program for instance with three views: GuiView, TerminalView, and ServiceView. Those are radically different interfaces, which use the same underlying model, and have an adapter in between. Note: I also a virtual base class "View" which the adapter uses and thus doesn't care if I swap out derived view types.
There are plenty of ways to split up "views" other than the example I provided, but basically your view is how the user and/or client interacts with the program.
A window class should not be storing information, by any varied definition or interpretation of MVC.