#include <QApplication>
#include <QWidget>
#include <QMouseEvent>

class TestPopup : public QWidget
{
public:
    explicit TestPopup(QWidget* parent = nullptr)
        : QWidget(parent, Qt::Popup)
    {
        auto p = palette();
        p.setColor(QPalette::Window, Qt::cyan);
        setPalette(p);
        setAutoFillBackground(true);
    }

    void resizeEvent(QResizeEvent* event)
    {
        qDebug() << "****" << event->size();
        QWidget::resizeEvent(event);
    }
};

class TestWidget : public QWidget
{
public:
    explicit TestWidget(QWidget* parent = nullptr)
        : QWidget( parent)
        , popup_(new TestPopup(this))
    {
        popup_->resize(200, 200);
    }

protected:
    void mousePressEvent(QMouseEvent* event)
    {
        popup_->show();
        // popup_->move(event->globalPosition().toPoint());
    }

private:
    QWidget *popup_;
};

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

    TestWidget w;
    w.resize(400, 400);
    w.show();

    return app.exec();
}