Hands-On High Performance Programming with Qt 5

QPainter

The software rasterizer will be used when painting the regular widgets through the QPainter class. However, QPainter class will never paint directly to the window, but rather uses a QBackingStore object, which will contain a buffered representation of the window contents. This enables Qt to implement partial updates by using QPainter only to update a subregion of the window. QBackingStore contents will be finally flushed, that is, written to the underlying OS's window by using a subclass of a QPlatformBackingStore class. On Windows, this will result in calling UpdateLayeredWindowIndirect or BitBlt system calls for respectively for translucent and opaque contents. In fact, you could also use QBackingStore and QPainter all alone, without ...