simple 2d graphics using qt

hello,i m quite new to qt.I m developing a project which is supposed to display vector image in a visualizer..the project contains visualizer class inherited from QMainWindow.
Main.cpp creates visualizer object “visualizer w and w.show”
visualizer.ui contains a menubar,toolbar,Qtreeview and QtabWidget.
I have another vecImg class that reads vector file and stores points,lines n polygon info. I want to display the info of vecImg class in
QTabWidget of the ui.
main.cpp calls visualizer which in turn invokes vecImg.cpp

I tried inheriting vecImg from QWidget and override paintEvent to draw lines on tabWidget but that didn’t work.

What should I do to draw vecImg containing info on QTabWidget of the visualizer.ui?