Focus handling incorrect in a widget hierarchy with Qt::WA_PaintOnScreen and Qt::WA_DontShowOnScreen

#include <QtWidgets>

class HighlightFocusWidget : public QWidget
{
public:
    HighlightFocusWidget(QWidget* parent)
        : QWidget(parent)
        , m_mouseDown(false)
    {
        setAutoFillBackground(false);
        setFocusPolicy(Qt::WheelFocus);

        connect((QApplication*)QApplication::instance(), &QApplication::focusChanged, this, [this]() { update(); });
    }

protected:
    virtual void paintEvent(QPaintEvent* event) override
    {
        QPainter painter(this);
        painter.setPen(Qt::NoPen);
        QColor color = (this == QApplication::focusWidget()) ? QColor(Qt::blue) : palette().color(QPalette::Background);
        painter.setBrush(color);
        painter.drawRect(rect());

        if (m_mouseDown)
        {
            painter.setBrush(Qt::red);
            painter.drawRect(rect().adjusted(4, 4, -4, -4));
        }
    }

    virtual void mousePressEvent(QMouseEvent* event) override
    {
        if (event->button() == Qt::LeftButton)
        {
            m_mouseDown = true;
            update();
        }
    }

    virtual void mouseReleaseEvent(QMouseEvent* event) override
    {
        if (event->button() == Qt::LeftButton)
        {
            m_mouseDown = false;
            update();
        }
    }

    virtual void contextMenuEvent(QContextMenuEvent *event) override
    {
        QMenu menu(this);
        menu.addAction("Menu Entry");
        menu.exec(event->globalPos());
    }

private:
    bool m_mouseDown;
};

class PaintOnScreenWidget : public QWidget
{
public:
    PaintOnScreenWidget()
    {
        setAttribute(Qt::WA_PaintOnScreen);
    }

protected:
    virtual QPaintEngine* paintEngine() const override
    {
        return 0;
    }
};

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QWidget* w = new QWidget();
    QHBoxLayout* layout = new QHBoxLayout(w);

    for (int i = 0; i < 2; ++i)
    {
        HighlightFocusWidget* hightlightWidget = new HighlightFocusWidget(w);
        layout->addWidget(hightlightWidget);
        QHBoxLayout* innerLayout = new QHBoxLayout(hightlightWidget);
        innerLayout->setContentsMargins(8, 8, 8, 8);

        QWidget* paintOnScreenWidget = new PaintOnScreenWidget();
        innerLayout->addWidget(paintOnScreenWidget);
        QHBoxLayout* paintOnScreenLayout = new QHBoxLayout(paintOnScreenWidget);
        paintOnScreenLayout->setContentsMargins(0, 0, 0, 0);

        QWidget* overlayWidget = new QWidget(/*paintOnScreenWidget*/);
        overlayWidget->setAttribute(Qt::WA_DontShowOnScreen);
        paintOnScreenLayout->addWidget(overlayWidget);
    }

    w->setFixedSize(QSize(600, 400));
    w->show();

    return app.exec();
}