QRect

QRect is a class in the Qt framework that represents a rectangle using integer coordinates. It is widely used to describe widget geometry, painting clipping regions, hit-testing, and other rectangular areas in GUI applications. A QRect is typically defined by its top-left corner and size, or by the coordinates of its edges.

Constructors and basic construction options include a default constructor, a constructor with left, top, width, and height, and constructors that take a top-left point with a size, or a top-left and bottom-right point. There is also a copy constructor. This allows creation from explicit coordinates or from existing points and sizes.

Key properties and accessors expose the rectangle’s geometry. Common methods include left(), top(), right(), bottom(), x(), y(), width(), height(), size(), topLeft(), bottomRight(), and center(). QRect also provides queries such as isNull(), isEmpty(), and contains() (with either point or coordinates), as well as intersects() to test overlap with another rectangle.

Geometric operations support manipulation and combination. Useful functions include translated() (and its in-place variants) to move a rectangle, adjusted() or adjust() to modify edges in place, normalized() to ensure left <= right and top <= bottom, and united() or intersected() to compute the union or intersection with another rectangle.

QRect is complemented by QRectF, the floating-point counterpart, used when sub-pixel precision is required. In practice, QRect is a core datatype in Qt for widget geometry, painting regions, and hit-testing, while QRectF targets precision-sensitive tasks in graphics.