The QMenu class provides a menu widget for use in menu bars, context menus, and other popup menus.| doc.qt.io
The QMainWindow class provides a main application window.| doc.qt.io
The QMenuBar class provides a horizontal menu bar.| doc.qt.io
The QWidget class is the base class of all user interface objects.| doc.qt.io
The QAction class provides an abstraction for user commands that can be added to different user interface components.| doc.qt.io
The Qt namespace contains miscellaneous identifiers used throughout the Qt library.| doc.qt.io
The QCoreApplication class provides an event loop for Qt applications without UI.| doc.qt.io