Описание тега qmainwindow
QMainWindow is a class in Qt library that implements the main window of an application.
As a main window for the application, QMainWindow is different from an ordinary widget.
It has a menu bar on the top, a status bar, it can also have toolbars and dock widgets.
It also have a so-called Central Widget, which can be occupied by any other widgets.
Qt also allows one to easily implement single- and multiply-document-interfaces with this class.
The official Qt documentation can be found here for Qt 4.8 and here for Qt 5.