#include <QApplication>
#include <QMainWindow>

class TestWidget : public QWidget
{
    Q_OBJECT

public:
    TestWidget(QWidget *parent = nullptr)
        : QWidget(parent) { }

    ~TestWidget()
    {
        cancelLoad();
    }

signals:
    void updated() const;

private:
    void cancelLoad()
    {
        emit updated();
    }
};

class MainWindow : public QMainWindow
{
    Q_OBJECT
    
public:
    MainWindow(QWidget *parent = nullptr)
        : QMainWindow(parent)
    {
        m_test = new TestWidget(this);

        connect(m_test, &TestWidget::updated,
            this, &MainWindow::updateContent);
    }

private:
    void updateContent() { }

    TestWidget *m_test = nullptr;
};

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

#include "main.moc"