QDialog Class | Qt Widgets 5.15.8
https://doc.qt.io/qt-5/qdialog.htmlUnlike exec(), open() is asynchronous, and does not spin an additional event loop. This prevents a series of dangerous bugs from happening (e.g. deleting the dialog's parent while the dialog is open via exec()). When using open() you can connect to the finished() signal of QDialog to be notified when the dialog is closed.
QGuiApplication Class | Qt GUI 5.15.8
doc.qt.io › qt-5 › qguiapplicationDetailed Description. QGuiApplication contains the main event loop, where all events from the window system and other sources are processed and dispatched. It also handles the application's initialization and finalization, and provides session management. In addition, QGuiApplication handles most of the system-wide and application-wide settings ...
QApplication Class | Qt Widgets 5.15.8
doc.qt.io › qt-5 › qapplicationQApplication specializes QGuiApplication with some functionality needed for QWidget -based applications. It handles widget specific initialization, finalization. For any GUI application using Qt, there is precisely one QApplication object, no matter whether the application has 0, 1, 2 or more windows at any given time.
QMainWindow Class | Qt Widgets 5.15.7
https://doc.qt.io/qt-5/qmainwindow.htmlDetailed Description Qt Main Window Framework. A main window provides a framework for building an application's user interface. Qt has QMainWindow and its related classes for main window management. QMainWindow has its own layout to which you can add QToolBars, QDockWidgets, a QMenuBar, and a QStatusBar.The layout has a center area that can be …