The QSettings class provides persistent platform-independent application settings.| doc.qt.io
The QFontMetrics class provides font metrics information.| doc.qt.io
The QFont class specifies a query for a font used for drawing text.| doc.qt.io
The QPainter class performs low-level painting on widgets and other paint devices.| doc.qt.io
The QString class provides a Unicode character string.| doc.qt.io
The QGuiApplication class manages the GUI application's control flow and main settings.| doc.qt.io