详细请见：
https://doc.qt.io/qt-5/qtwidgets-graphicsview-diagramscene-example.html
底下为摘抄内容。版权归原作者所有。
Diagram Scene Example
Demonstrate how to use the Graphics View framework.
The Diagram Scene example is an application in which you can create a flowchart diagram. It is possible to add flowchart shapes and text and connect the shapes by arrows as shown in the image above. The shapes, arrows, and text can be given different colors, and it is possible to change the font, style, and underline of the text.
The Qt graphics view framework is designed to manage and display custom 2D graphics items. The main classes of the framework are QGraphicsItem, QGraphicsScene and QGraphicsView. The graphics scene manages the items and provides a surface for them. QGraphicsView is a widget that is used to render a scene on the screen. See the Graphics View Framework for a more detailed description of the framework.
In this example we show how to create such custom graphics scenes and items by implementing classes that inherit QGraphicsScene and QGraphicsItem.