To provide very fast rendering of its scene, Qt Quick uses a mechanism called scene graph. The graph consists of a number of nodes of well-known types, each describing a primitive shape to be drawn. The framework makes use of knowledge of each of the primitives allowed and their parameters to find the most performance-wise optimal order in which items can be rendered. Rendering itself is done using OpenGL, and all the shapes are defined in terms of OpenGL calls.
Providing new items for Qt Quick boils down to delivering a set of nodes that define the shape using terminology the graph understands. This is done by subclassing QQuickItem and implementing the pure virtual updatePaintNode() method, which is supposed to return a ...
