Drawing basic shapes on screen

In this section, we will learn how to draw simple vector shapes (line, rectangle, circle, and so on) and display text on the main window using the QPainter class. We will also learn how to change the drawing style of the vector shapes using the QPen class.

How to do it…

First, let's create a new Qt Widgets Application project:

1. Open up mainwindow.ui and remove the menu bar, main tool bar, and status bar so that we get a clean, empty main window. Right-click on the bar widgets and select Remove Menu Bar from the pop-up menu:
   
2. Then, open up mainwindow.h and add the following code to include the QPainter header file:

   #include <QMainWindow>
   #include <QPainter>
   

3. Then, declare the paintEvent() event handler below the class destructor:

   public:
   explicit MainWindow(QWidget *parent = 0);
   ~MainWindow();
   virtual void paintEvent(QPaintEvent *event);
   

4. Next, open up mainwindow.cpp and define the paintEvent() event handler:

   void MainWindow::paintEvent(QPaintEvent...