QPainter painter(this); QRectF viewportRect(0, 0, 500, 500); painter.setViewport(viewportRect.toRect());
QMatrix oldMatrix = painter.matrix(); painter.translate(50, 50); painter.scale(2, 2); QRectF viewportRect(0, 0, 500, 500); painter.setViewport(viewportRect.toRect()); painter.setMatrix(oldMatrix);In this example, we start by saving the current matrix of the painter. We then apply a translation and scaling to the painter's matrix, which will be reflected in the drawing. We reset the viewport dimensions, set the matrix back to its original state. In summary, QPainter viewport is a powerful tool for applications that need to render complex graphics. It is a part of the Qt library, which is a comprehensive C++ toolkit for developing cross-platform applications.