CpuWidget using QCharts

Now that the base class SysInfoWidget is ready, let's implement its first child class: CpuWidget. We will now use the Qt Charts API to display a good-looking widget. The average CPU load will be displayed in a pie graph with a hole in the center, like a partly eaten donut where the eaten part is the percentage of the CPU used. The first step is to add a new C++ class named CpuWidget and make it inherit SysInfoWidget:

#include "SysInfoWidget.h" 
 
class CpuWidget : public SysInfoWidget 
{ 
public: 
    explicit CpuWidget(QWidget* parent = 0); 
}; 

In the constructor, the only parameter needed is a QWidget* parent. Since we provided default values for the startDelayMs and updateSeriesDelayMs variables in SysInfoWidget class, we get the best possible behavior; there is no need to remember it when subclassing SysInfoWidget, but it is still easy to override it if need be.

The next step is to override the updateSeries() function from the SysInfoWidget class and start using...