2D Coordinate point update, spot tracking, positioning, navigation

Hi,

I want to draw a black background color screen with an origin in the center to show a position tracking green spot, with delta X/Y accumulation data retrieved from Optical-Flow Sensor.

Now a solution I can think of is to use QImage to manipulate pixels and draw it onto the screen, creating my own coordinate.
Is there any QClass I can use to help me draw the a coordinate, and locate a certain spot much easier?

Are there any examples similar to a spot tracking problem that I can refer to?

Thank you!

The QGraphicsScene and QGraphicsView in the Qt Graphics View Framework might be useful.

QWidget has its own coordinate system, no need to build.
There is a Analog Clock Example, which can totally answer my question.