QtGui

QtGui is a module of the Qt cross‑platform application framework that provides the core graphical user interface capabilities used by Qt applications. In current Qt releases, the traditional widget set is implemented in the QtWidgets module, while QtGui supplies the underlying painting, image handling, font and color infrastructure, and windowing support that widgets rely on.

Key components include painting and rendering: QPainter, QPaintDevice, QPainterPath; image handling: QImage, QPixmap, QBitmap; color and font management: QColor, QPalette, QFont, QFontMetrics; drawing primitives and geometry: QPen, QBrush, QTransform, QRegion; iconography: QIcon, QIconEngine; and windowing and input: QWindow, QScreen, QCursor, QClipboard, QDrag, QInputMethod, and QGuiApplication. QtGui also provides the base classes and services used by the window system integration and non-widget GUI elements, such as drag-and-drop support and offscreen rendering.

Usage is oriented toward implementing custom painting, rendering images and text, handling fonts and colors, and working with windowing primitives. For standard user interfaces, the QtWidgets module is typically used, with QtGui providing the underlying functionality.

Historywise, QtGui has evolved through Qt versions. In Qt 4, QtGui contained the widgets themselves; with Qt 5, widgets were moved to QtWidgets, while QtGui focused on painting, fonts, images, and windowing. Qt 6 maintains a similar division, continuing to provide the low-level GUI infrastructure that supports both custom rendering and non-widget GUI operations across platforms.