The QRegion class specifies a clip region for a painter.| doc.qt.io
The QRect class defines a rectangle in the plane using integer precision.| doc.qt.io
The QPaintEvent class contains event parameters for paint events.| doc.qt.io
The QWidget class is the base class of all user interface objects.| doc.qt.io
The QEvent class is the base class of all event classes. Event objects contain event parameters.| doc.qt.io
The QPainter class performs low-level painting on widgets and other paint devices.| doc.qt.io