The QEvent class is base class of all event classes. ... QEvent  ( int type )  . ... The main event loop of Qt fetches native window system events from the event queue, translates them into QEvent and sends the translated events to QObjects. Generally, events come from the underlying window system, but it is also possible to manually send events through the QApplication class using QApplication::sendEvent () and QApplication::postEvent (). ... The file qevent.h lists all event types. ...